www.elsevier.com/locate/pharmthera
Pharmacology & Therapeutics 99 (2003) 113–132
Immune responses in cancer
Jamila K. Adama, Bharti Odhavb, Kanti D. Bhoolac,*
aDepartment of Medical Science, Durban Institute of Technology (ML Sultan Campus), Durban, South AfricabDepartment of Biological Science, Durban Institute of Technology (ML Sultan Campus), Durban, South Africa
cAsthma and Allergy Research Institute, University of Western Australia, Ground Floor, E Block, Sir Charles Gairdner Hospital,
Hospital Avenue, Nedlands, WA 6009, Australia
Abstract
The complex of humoral factors and immune cells comprises two interleaved systems, innate and acquired. Immune cells scan the
occurrence of any molecule that it considers to be nonself. Transformed cells acquire antigenicity that is recognized as nonself. A specific
immune response is generated that results in the proliferation of antigen-specific lymphocytes. Immunity is acquired when antibodies and T-
cell receptors are expressed and up-regulated through the formation and release of lymphokines, chemokines, and cytokines. Both innate and
acquired immune systems interact to initiate antigenic responses against carcinomas. A new approach to the treatment of cancer has been
immunotherapy, which aims to up-regulate the immune system in order that it may better control carcinogenesis. Currently, several forms of
immunotherapy that use natural biological substances to activate the immune system are being explored therapeutically. The various forms of
immunotherapy fall into three main categories: monoclonal antibodies, immune response modifiers, and vaccines. While these modalities
have individually shown some promise, it is likely that the best strategy to combat cancer may require multiple immunotherapeutic strategies
in order to demonstrate benefit in different patient populations. It may be that the best results are obtained with vaccines in combination with
a variety of immunotherapy combinations. Another potent strategy may be in combining with more traditional cancer drugs as evidenced
from the benefit derived from enhancing the efficacy of chemotherapy with cytokines. Through such concerted efforts, a durable, therapeutic
antitumour immune response may be achieved and maintained over the course of a patient’s lifespan.
D 2003 Elsevier Science Inc. All rights reserved.
Keywords: Carcinogenesis; Immunity; Immunotherapy; Tumour antigens and surveillance; Vaccines
Abbreviations: ADCC, antibody-dependent cell-mediated cytotoxicity; APC, antigen-presenting cells; ATP, activated receptor pathway; Bcl-2, B-cell
lymphomal leukaemia-2 protein; CDK, cyclin-dependent kinases; CEA, carcinoembryonic antigen; CTL, cytotoxic T-lymphocytes; EGFR, epidermal growth
factor receptor; FGF, fibroblast growth factor; GM-CSF, granulocyte-monocyte colony stimulating factor; HER-2, human epidermal growth factor receptor;
HLA, human leucocyte antigen; HSP, heat shock protein; IFN, interferon; IKB, inhibitors of KB; IL, interleukin; IL-1R, interleukin-1 receptor; IL-1RA,
interleukin-1 receptor antagonist; LPS, lipopolysaccharide; MHC, major histocompatibility complex; NF-kB, nuclear factor-kB; NK, natural killer; PGE2,
prostaglandin E2; PMN, polymorphonuclear leucocytes; RAS, rat sarcoma gene product protein, p21ras; TGF-b, transforming growth factor-b; TNF, tumour
necrosis factor; VEGF, vascular endothelial growth factor; WT1, Wilms’ tumour gene.
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
1.1. Immunity: historical preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
1.2. Innate immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
1.3. Acquired immunity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
1.4. Antigen recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
1.5. Cell populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
1.6. Immune cell regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
1.7. Immune cell modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
1.7.1. Interleukin-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
1.7.2. Tumour necrosis factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
0163-7258/03/$ – see front matter D 2003 Elsevier Science Inc. All rights reserved.
doi:10.1016/S0163-7258(03)00056-1
* Corresponding author. Tel.: +61-8-9346-2954; fax: +61-8-9346-2816.
E-mail address: [email protected] (K.D. Bhoola).
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132114
1.7.3. Interleukin-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
1.7.4. Interleukin-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
1.7.5. Interleukin-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
1.7.6. Granulocyte-macrophage colony stimulating factor. . . . . . . . . . . . . . . . 119
2. Carcinogenic cascade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
2.1. Proliferation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
2.2. Cell cycle progression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
2.3. DNA replication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
2.4. Evading apoptosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
2.5. Angiogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
2.6. Metastasis and invasion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
3. Tumour antigens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
4. Immune surveillance and detection of tumours . . . . . . . . . . . . . . . . . . . . . . . . . . 122
5. Immune-directed apoptosis of cancer cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6. Tumour escape mechanisms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
7. Cancer immunotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
7.1. Molecular aspects of immunotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
8. Immunotherapeutic strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
8.1. Monoclonal antibodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
8.2. Immune response modifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
8.2.1. Interferon-a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
8.2.2. Interleukin-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.2.3. Interleukin-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.3. Colony stimulating factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.4. Vaccination against tumours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Table 1
Immune response modulators
Cytokines Lymphokines Chemokines Growth factors
IL-1a IL-2 IL-8 EGF
IL-1b IL-3 Gro-a TGF-bIL-6 IL-4 Gro-b FGF
IL-10 GM-CSF MIP-1a PDGF
IL-13 IF-g MIP-1b TGF-b family
TNF-a MCP-1, -2, and -3
1. Introduction
1.1. Immunity: historical preamble
The earliest record of treating a patient with cancer comes
from the Edwin Smith papyrus dated 1600 B.C. The papyrus
documents a surgical procedure that was established as the
primary method of treating solid tumours in the 19th century
and remains so today. Radiation therapy came into practice
around 1896, just 1 year after Roentgen first reported the use
of X-rays for diagnostic purposes in medicine. Chemother-
apy is an invention of the 19th century (Old, 1996). William
B. Coley, a New York City surgeon, is often credited with
first recognizing the potential role of the immune system in
cancer treatment (Coley, 1991). He observed that some of
his patients with sarcoma would undergo spontaneous
regression of their tumour. However, not until 1976 was it
possible to more fully understand how tumour recognition
and rejection was mediated at the cellular and molecular
level.
1.2. Innate immunity
The complex of cells and humoral factors that is known
collectively as the immune system may be divided into two
interrelated cascades. The first such functional system is
known as innate (natural) immunity. In general, the term
immunity implies acquired immunity with its antibodies and
T- and B-lymphocyte populations. Innate immunity involves
a large number of different cell populations such as epithe-
lial cells, monocytes, macrophages, dendritic cells, poly-
morphonuclear leucocytes (PMN), natural killer (NK) cells,
and various lymphocyte subpopulations (e.g., CD5-positive
B-lymphocytes and gd T-lymphocytes), which bridge the
divide between innate and acquired immunity. These cells
generally arise from precursor cell populations in the bone
marrow. Humoral systems are also important and include a
large number of cytokines (Table 1), certain enzymes (e.g.,
lysozyme), metal-binding proteins, integral membrane ion
transporters, complex carbohydrates, and complement path-
ways. Molecules that act as recognition ‘‘receptors’’ in
innate immunity comprise humoral proteins (c-reactive
protein, serum amyloid, mannose binding protein, and
CD14) and cellular receptors (scavenger and mannose
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 115
receptors, dendritic cell targets, CD14, CD35, CD21, and
CD11b [see Table 2]). Cytokine formation, release, and
target interactions form an important arm of the cellular
response in growth, repair, and cell proliferation. The
notable cytokines modulating the proliferation of tumour
cells are probably transforming growth factor-b (TGF-b)family, epithelial growth factor, and colony stimulating
factors.
1.3. Acquired immunity
The second, termed acquired or adaptive immunity,
evolved around 400 million years ago. Acquired immun-
ity compromises a unique mechanism whereby genetic
‘‘mutation’’ occurring in two specialised cell populations,
B- and T-lymphocytes (Fig. 1), produces numerous
molecular ‘‘shapes’’ that are expressed as antibodies and
T-cell receptors. If these molecules bind to structurally
related proteins called antigens, and provided costimula-
tory signals are present, proliferation of antigen-specific
lymphocytes occurs and a specific immune response is
generated. The specificity of immune response resides in
selective clonal proliferation of lymphocytes. Two further
families of molecules play major roles in acquired
immunity: major histocompatibility complex (MHC) gene
products and cytokines. They provide an essential link for
cell-to-cell communication and component of the acquired
(as well as the innate) immune response (Clark &
Ledbetter, 1994). The cell surface protein CD40 with its
receptor provides a costimulatory signal for the inter-
action between T-cells and antigen-presenting cells (APC)
(Chen et al., 2002).
Table 2
Immunological receptors
CD number Function
CD1a/1b/1c Peptide, lipid antigen presentation
CD2 T-cell adhesion to APC
CD3 T-cell activation
CD4 Th activation
CD5 T-cell activation
CD8 T-cell subpopulation marker
CD11a/CD18 Leukocyte adhesion protein
CD11b/CD18 Leukocyte adhesion protein
CD11c/CD18 Leukocyte adhesion protein
CD14 LPS binding protein
CD16 Phagocytosis and ADCC
CD19 B-cell activation/proliferation
CD23 B-cell activation/IgE regulation
CD28 Costimulatory molecule
CD54 Adhesion molecule
CD62E Vascular adhesion molecule
CD71 Receptor for transferrin
CD80 Costimulatory molecule
CD86 Costimulatory molecule
CD88 C5a receptor
CD152 Costimulatory molecule
1.4. Antigen recognition
Antibody synthesis is the molecular response to the
presence of nonself epitopes (Fig. 2). Antibodies are specific
immunoproteins formed by B-cells in response to nonself
molecules. Antibodies react directly against the antigen or
Fig. 1. Antigen recognition and antibody formation.
Fig. 2. B-lymphocytes.
Fig. 3. Dendritic cell interactions.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132116
by activation of the complement system. One of the more
important complement effects includes opsonization and
phagocytosis. A product of the complement cascade
strongly activates phagocytosis by neutrophils and macro-
phages, which engulf nonself proteins. This type of cellular
event is called antibody-dependent cell-mediated cytotox-
icity (ADCC) and has the advantage of enhancing T-cell
activity. Antibodies have also been shown to kill cells by
blocking growth mechanisms, particularly in cancer cells.
Growth factor proteins such as human epidermal growth
factor receptor (HER-2)/neu can become overexpressed
after the gene that encodes the protein is amplified. Anti-
bodies specific for HER-2/neu bind to the molecule on the
surface of the cell and block the growth signal (Slamon et
al., 2001).
1.5. Cell populations
Cell populations (macrophages, dendritic cells, NK cells,
and neutrophils) play a major role in both innate and
acquired immunity. However, the two key cell populations
that essentially define acquired immunity are the B- and T-
lymphocytes (Gowans et al., 1962). Adaptive immunity,
therefore, involves a wide range of antigen receptors
expressed on the surface of T- and B-lymphocytes that
detect nonself molecules. T-cells instruct affected host cells
to either shut down protein synthesis or commit suicide. B-
cells respond to antigens by secreting their own antigen
receptors as antibodies. Antibodies also call on the innate
immune system for help. Stimulation of antigen through the
B-cell receptor followed by T-cell activation drives prolif-
eration and differentiation of antigen-specific naive B-lym-
phocytes into memory B-cells and plasma cells. Memory B-
cells mediate secondary immune responses and plasma cells
sustain antibody production for several months.
The different subpopulations of T-cells (Mason, 1987)
are recognized largely by their expression of surface pro-
teins (CD markers). All T-cells express CD3, a heterooligo-
meric protein that is part of the T-cell receptor complex, and
can be further subdivided into those cells that express CD4
and those that express CD8. The CD4 lymphocyte popu-
lation can be further functionally subdivided into two
subpopulations termed Th1 and Th2 lymphocytes (Mason,
1988). Th1 and Th2 cells are initially discriminated not on
the basis of cell surface markers but on the basis of the
patterns of cytokines they produce. In very recent years, it
has proved possible to identify these distinct CD4 subpo-
pulations on the basis of their expression of chemokine
receptors.
Dendritic cells constitute a family of APC defined by
their morphology and their capacity to initiate primary
immune response (Rafiq et al., 2002). Langerhans cells
are paradigmatic dendritic cells, described in 1868 by a
young medical student, Paul Langerhans, in Berlin. Langer-
hans cells are present with epithelial cells in the epidermis,
bronchi, and mucosae (Fig. 3). After antigenic challenge,
the dendritic cells migrate into the T-cell areas of proximal
lymph nodes where they act as professional APC. Langer-
hans cells originate in the bone marrow and CD34+ hae-
matopoietic progenitors are present in cord blood or
circulating blood. They are actively involved in skin lesions
of allergic contact dermatitis or atopic dermatitis in cancer
immunosurveillance (Schmitt, 2001).
Human neutrophil transcribes and secretes peptides
termed a-defensin-1, -2, and -3 in response to nonself
proteins. Defensins have the ability to signal activation of
cells involved in adaptive immunity, specifically CD8+ T.
a-defensin and b-chemokines (MIP-1a, MIP-1b, and
RANTES) may be cooperatively involved in cell defense.
b-defensins are small peptides of the innate immune system.
b-defensins2 may act directly on immature dendritic cells, as
an endogenous ligand for Toll-like receptor 4, to up-regulate
dendritic cell maturation, thereby triggering adaptive imma-
ture responses. It is suggested that b-defensins2 may provide
molecular immunosurveillance against tumour antigens.
The role of macrophages in tumour growth and devel-
opment is complex and multifaceted (Gough et al., 2001).
Whilst there is limited evidence that tumour-associated
macrophages can be directly tumouricidal and stimulate
the antitumour activity of T-cells, there is now contrasting
evidence that tumour cells are able to block or evade the
activity of tumour-associated macrophages at the tumour
site (Bingle et al., 2002).
1.6. Immune cell regulation
Important scientific discoveries in recent years have led
to an increase in our understanding of the role of helper T-
cells. T-cells are either cytotoxic (CD8+) or helpers
(CD4+). Unlike antibodies, which react with intact proteins
only, the CD8+ T-cells react with peptide antigens
expressed on the surface of a cell. Peptide antigens are
those that have been digested by the cell and presented as
peptides displayed in the MHC. MHC-encoded molecules
govern immune responses by presenting antigenic peptides
to T-cells. The peptide and the MHC together attract T-
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 117
helper cells. CD8+ T-cells are specific for class I MHC
molecules, while CD4+ T-cells are specific for class II
MHC molecules. After attaching to the MHC-peptide
complex expressed on a cell, the CD8+ T-cell destroys
the cell by perforating its membrane with enzymes or by
triggering an apoptotic or self-destructive pathway. The
CD8+ T-cell will then move to another cell expressing
the same MHC-peptide complex and destroy it as well. In
this manner, cytotoxic T-cells can kill many invasive cells.
Ideally, CD8+ T-cells could engender a very specific and
robust response against tumour cells. Cytotoxic T-lympho-
cytes (CTL) are considered to be essential effectors of the
cell-mediated immune response. The ability of CTL to
specifically recognize and lyse malignant cells expressing
the relevant surface antigens under optimal in vitro con-
ditions justifies attempts to boost their number and activity
through various forms of immunotherapy (Titu et al.,
2002).
NK cells also form a line of defense against host cells
that are stressed and/or cancerous. NK cells express surface
receptors that receive signals from the environment and
determine their response to foreign or malignant cells. NK
cells respond to these signals by producing effector mole-
cules, which can both directly suppress tumour growth and
convey important information to the rest of the immune
system (Smyth et al., 2002).
The helper T, or CD4+ T-cell, is the major regulator of
virtually all immune system activities. These cells form a
series of protein mediators called lymphokines that act on
other cells of the immune system and on bone marrow.
Some of the most important lymphokines secreted by the
helper T-cells include interleukin (IL)-2, IL-3, IL-4, IL-5,
IL-6, granulocyte-monocyte colony stimulating factor
(GM-CSF), and interferon (IFN)-g (see Table 1). Without
these lymphokines, the remainder of the immune system
does not function as effectively as it would with the
appropriate cytokine environment. Lymphokines produced
by helper T-cells also regulate macrophage response. The
lymphokines slow or stop the migration of macrophages
after they have been engaged, allowing macrophages to
accumulate at the site. These lymphokines also stimulate
more efficient phagocytosis, so they can destroy rapidly
increasing numbers of toxins. The T-helper cell amplifies
itself by secreting lymphokines, particularly IL-2. This
action enhances the helper cell response as well as the
entire immune system’s response to foreign antigens. Like
CD8+ T-cells, the CD4+ T-cells also recognize MHC-
peptide complexes in the context of class II MHC. CD4+
T-cells augment the immune response by secreting cyto-
kines that stimulate either a cytotoxic T-cell response (Th1helper T-cells) or an antibody response (Th2 helper T-cells).
These cytokines can initiate B-cells to produce antibodies
or enhance CD8+ T-cell production. The function of the
CD4+ T-cell depends upon the type of antigen it recognizes
and the type of immune response required. The immuno-
logical dysfunction associated with human cancer com-
prises changes within the immune network including
cytokine imbalance of Th1/Th2 origin (Lauerova et al.,
2002).
The immune response to carcinoma cells like allograft
rejection is initiated through activation of alloreactive T-
cells and APC (e.g., monocyte-macrophages, dendritic
cells, and B-cells). This process involves the activity of
antibodies, adhesion molecules, cytokines, and lympho-
kines. A characteristic feature is the infiltration of the
tumour or graft by host mononuclear cells (lymphocytes
and macrophages). Immunohistologically, these have been
characterized as T- and B-lymphocytes, macrophages, and
NK cells (Medawar, 1944; Mason & Morris, 1986). Stimu-
lated B-lymphocytes differentiate into antibody-producing
plasma cells, which secrete nonspecific and specific nonself
antibodies (Tilney et al., 1979). The immunological
response to the foreign tissue proteins comprises two limbs:
an afferent or sensitising limb and an efferent or effector
limb (Gowans et al., 1962). T-cell activation begins when
T-cells recognize intracellularly processed fragments of
foreign proteins embedded in the groove of the MHC
proteins, expressed on the surface of APC (Krensky et
al., 1990; Weiss & Littman, 1994).
CD4 and CD8 proteins, expressed by peripheral blood T-
cells, bind to human leucocyte antigen (HLA) class II and
class I molecules, respectively (Miceli & Parnes, 1991). The
complex of T-cell antigen receptor and CD3, CD4, and CD8
proteins physically associate with and activate several intra-
cellular protein tyrosine kinases, resulting in mobilization of
ionised calcium from bound intracellular stores by inositol
triphosphate. The increased intracellular free calcium and
sustained activation of protein kinase C promote expression
of genes central to T-cell growth.
Cytokines are a family of peptide molecules that are
responsible for direct cell-to-cell communication. They
mediate interactions between leucocyte populations and
between leucocytes and tissue cells (Table 3). Cytokines
of the IL family, derived from APC (namely, IL-1 and IL-
6), also provide costimulatory signals that result in T-cell
activation. T-cell-derived lymphokines (e.g., IL-2 and IL-
4), and contact between T- and B-cells through specific
pairs of receptors and coreceptors, provide signals essential
for B-cell stimulation (Clark & Ledbetter, 1994). T-cell
proliferation is the result of IL-2 expression that is depend-
ent on T-cell activation.
The net result of cytokine production is the emergence
of antigen specific, tissue infiltrating, and destructive T-
cells. Cytokines also activate macrophages and other
inflammatory cells and the production of antibodies by
stimulated T-cells. Cytokines can amplify the ongoing
immune response by up-regulating the expression of
HLA antigens and costimulatory molecules (such as B7)
on parenchymal cells and APC. The costimulators direct T-
cell differentiation, for example, into a CD4+ Th1 cell,
which secretes lymphokines, facilitating CTL killing of
cells, or differentiates into a CD4+ Th2 cell, which
Table 3
Cellular expression and actions of cytokines
Cytokine Source Actions
IL-1 Macrophages, fibroblasts,
synovial lining cells
. Stimulates production of
IL-6 and TNF-aT-and B-lymphocytes,
endothelial cells
. Augments T-cell proliferation
and B-cell activation
. Induces hepatic production
of acute phase proteins
. Activates neutrophils to
synthesize and release PG
. Increases binding of
lymphocytes and monocytes
to endothelial cells
. Induces endothelial cell
proliferation
TNF Macrophages, monocytes . Stimulates production of
IL-1, -6, and -8
. Increases PGE2 and
collagenase production
. Increases plasminogen
activity
. Increases release of FGF
. Modulates PMN function
such as the release of
oxygen metabolites,
phagocytosis, adhesion to
endothelium, and ability to
degrade cartilage
IL-6 Neutrophils, monocytes,
fibroblasts, T- and B-cells,
. Stimulates the release of
hepatic acute phase proteins
endothelial cells . Induces activated B-cells to
differentiate into plasma cell
IL-8 Neutrophils, fibroblasts,
hepatocytes, epithelial
and endothelial cells
. Stimulates and attracts
neutrophils
GM-CSF Macrophages, fibroblasts,
endothelial cells,
. Stimulates secretion
of IL-1, TNF-a, and PGE2
and activated lymphocytes . Activates chemotaxis,
phagocytosis, antibody
cytotoxicity, and oxidative
metabolism in granulocytes
. Induces HLA-DR expression
on monocytes
Abbreviations: IL, interleukin; TNF, tumour necrosis factor; PG, prosta-
glandin; FGF, fibroblast growth factor; GM-CSF, granulocyte-macrophage
colony stimulating factor.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132118
stimulates antibody production by B-cells (Dallman, 1995).
Cell killing may occur via specific T-cell products, such as
granzyme B (a serine esterase protein) and perforin (a
pore-forming lytic protein), which have been reported to
correlate closely with acute rejection of grafts (Clement et
al., 1994). The type of organ grafted, HLA matching
between donor and host and the degree of presensitisation,
influence the acute rejection process. CD4+ T-helper cells
are the primary, initiating, and organizing component of
host immunoresponsiveness against grafts. CD8+ cells are
recruited secondarily to the site to complete the acute
rejection process (Mason & Morris, 1986; Mason, 1987).
It is considered that these cellular and molecular responses
observed during graft rejection will apply to transformed
cells as they become carcinogenic.
1.7. Immune cell modulation
1.7.1. Interleukin-1
The IL-1 family consists of IL-1a, IL-1b, and IL-1
receptor antagonist (IL-1RA), which are structurally related
to each other and have similar affinity for IL-1R on cells
(Dinarello, 1994). IL-1a and IL-1b are potent agonists that
elicit various biological responses, whereas IL-1RA blocks
the effects of the agonists by competing for binding sites on
the cell surface receptors (Arend, 1993). IL-1a, IL-1b, andIL-1RA are encoded by separate genes, designated as ILIA,
ILIB, and ILIRN, respectively. The three genes are clustered
on the long arm of human chromosome 2 in a region (q13–
q21) that spans more than 430 kb (Nicklin et al., 1994).
Three related cell surface proteins are involved in IL-1
binding and signalling: type 1 IL-1R, type 2 IL-1R, and
IL-1R-associated protein (Sims & Dower, 1994). The IL-1R
genes are members of the large immunoglobulin supergene
family and are located in the same region of human
chromosome 2 as their ligands.
IL-1 is produced during antigen presentation and is
secreted by macrophages, fibroblasts, endothelial cells, and
T- and B-lymphocytes (Lorenzo, 1991). It has a wide range of
biological actions and acts via modulating gene expression in
target cells. Both IL-1a and IL-1b possess comitogenic
properties, recruit cells to the cancer site, and stimulate the
production of proinflammatorymediators, including IL-6 and
tumour necrosis factor (TNF). IL-1 has been shown to
augment T-cell proliferation and B-cell activation in response
to antigenic challenge (Dinarello et al., 1986). The cytokine
activates neutrophils to synthesize and release prostaglandins
(Rossi et al., 1985), enhance binding of lymphocytes and
monocytes to endothelial cells, and induce neovasculariza-
tion, a process that may encompass tumour initiation of new
blood vessels.
1.7.2. Tumour necrosis factor
TNF is produced principally by macrophages and mono-
cytes. The production of TNF is stimulated by several factors,
including lipopolysaccharide (LPS), IL-1, and GM-CSF, and
mediates its effects by interaction with two related membrane
receptors: TNF-R1 and TNF-R2 (or type I and type II). TNF-
a is thought to be the controlling element in the ‘‘cytokines
network’’ and is responsible for the production of other
cytokines (e.g., IL-1, IL-6, and IL-8) (Brennan et al., 1992).
1.7.3. Interleukin-6
IL-6 is produced bymonocytes, T-lymphocytes, and fibro-
blasts. The synthesis of this cytokine is induced by IL-1 and
TNF-a (Wong & Clark, 1988). IL-6 stimulates activated B-
cells to differentiate into plasma cells, which produce immu-
noglobulins (Arend&Dayer, 1990).Circulating levels of IL-6
are elevated in prostate carcinoma (Adler et al., 1999).
y & Therapeutics 99 (2003) 113–132 119
1.7.4. Interleukin-8
IL-8 is a member of the chemokine supergene family.
The chemokines belong to two related polypeptide families,
C-X-C and CC chemokines, as defined by the location of
the two cysteine residues at the amino terminus. In the C-X-
C family, the cysteine residues are separated by a non-
conserved amino acid; in the CC family, the cysteine
residues are in juxtaposition (Baggiolini et al., 1994). The
C-X-C chemokines are clustered on human chromosome 4.
IL-8 is a kDa peptide of the C-X-C chemokine family. It is a
potent neutrophil attractant and stimulator and is produced
by neutrophils, fibroblasts, hepatocytes, and epithelial and
endothelial cells (Baggiolini et al., 1989). IL-1, TNF, and
LPS-stimulated neutrophils exhibit increased expression of
IL-8 mRNA and IL-8 production (Strieter et al., 1992).
1.7.5. Interleukin-2
The lymphokine IL-2 is essential in stimulating T- and B-
cell populations to divide and expand their clones. IL-2 is
produced by antigen-stimulated T-lymphocytes and must be
present in sufficient quantities in order to mount an effective
counterattack against cancer cells. Increased formation of
IL-2 is an important way of expanding Tc-lymphocyte
population. These killer cells can accomplish lysis of
tumour cells through cell-to-cell contact. Two categories
of this cell type are believed to exist, namely, (1) antigen-
specific, MHC-restricted (well-established) Tc lymphocytes
and (2) broad specificity, non-MHC-restricted Tc lympho-
cytes. Thus, antigen-specific killer cells would recognize
cells with specific tumour markers, whereas those with
broad specificity could lyse a variety of different targets
on the tumour cell.
1.7.6. Granulocyte-macrophage colony stimulating factor
GM-CSF is a growth factor that is synthesized by macro-
phages, fibroblasts, endothelial cells, and activated lympho-
cytes (see Table 3) (Groopamn et al., 1989). It was first
characterized based on promotion of growth and differenti-
ation of granulocytes and macrophages. GM-CSF stimulates
the secretion of IL-1 and enhances the secretion of TNF-aand prostaglandin E2 (PGE2) from macrophages (Fischer et
al., 1988; Heidenreich et al., 1989). In addition, GM-CSF
activates chemotaxis, phagocytosis, antibody-dependent
cytotoxicity, and oxidative metabolism in granulocytes
(Firestein, 1994) and induces HLA-DR expression on
monocytes (Xu et al., 1989).
J.K. Adam et al. / Pharmacolog
2. Carcinogenic cascade
2.1. Proliferation
A characteristic of cancer cells is its ability to undergo
extensive proliferation through overproducing growth fac-
tors (vascular endothelial growth factor [VEGF] and fibro-
blast growth factor [FGF]) and/or overexpressing receptors
for growth factors (HER-2, epidermal growth factor recep-
tors [EGFR], and platelet-derived growth factor receptor).
Cellular proliferation begins when cell surface receptors
recognize their appropriate growth factors. The function of
extracellular signal-regulated kinases is to control cell
division, namely, meiosis, mitosis, and postmitotic functions
in differentiated cells. They are members of a specific
molecular group that is activated by the protooncogene
Ras. The next event is a cascade of reactions mediated by
cytoplasmic protein kinases (rat sarcoma gene product
protein, p21ras [RAS], ras-associated factor, MEK, and
MAPK cascade) that culminates in transcriptional activa-
tion, cell cycle progression, and cell division. Inhibition of
such a growth factor-induced mitogenic signalling may be
achieved through (i) binding of the growth factor to its
receptor or receptor dimerization with a specific agent,
namely, a monoclonal antibody, (ii) preventing receptor
activation with small molecule inhibitors, which bind to
the activated receptor pathway (ATP)-binding site in the
intracellular domain of the receptor, and (iii) inhibition of
cytoplasmic proteins downstream of the ATP (namely,
preventing formation of membrane-bound ‘‘activatable’’
RAS). Mutations that convert Ras to an activated oncogene
are common oncogenic mutations in human tumours.
2.2. Cell cycle progression
The four phases of the cell cycle are the M phase (state of
active mitosis), the S phase (state of DNA synthesis), and
the two G or gap phases that separate the other phases.
Cyclins and cyclin-dependent kinases (CDK) govern the
progression of cells from one phase to another (Sender-
owicz, 2001). Inhibiting cells at any point in the cell cycle
inhibits their progression through the cell cycle, thereby
preventing mitosis and cell division. The tumour suppressor
gene (p53) (Levine, 1997) and CDK inhibitors (p15, p16,
p21, and p27) are negative regulators of cell cycle progres-
sion, causing growth arrest. Commonly used cytotoxins
block the cell cycle in the S and G2/M phases (Malumbres
& Barbacid, 2001). The question arises whether carcinoma
cells secrete cytotoxins that target specific components of
the cell cycle. Nucleostemin, a stem cell gene product, if
produced by the tumour cell would bind to p53 and arrest its
function. Mutations of p53 are implicated in the many
different cancers.
2.3. DNA replication
Tumour cells have infinite replicative potential. DNA
replication takes place in the S phase of the cell cycle. The
process of replication essentially duplicates the genetic
material with the help of the replication machinery, namely,
DNA polymerases, DNA ligases, and topoisomerases.
Inhibiting replication ensures that malignant cells do not
progress in the cell cycle. Telomerase is a key component in
immortalization of malignant cells by preserving the integ-
Fig. 4. Diapedesis of tumour cell into the circulation.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132120
rity of telomeres. Consequently, immunotherapeutic inhibi-
tion of telomerase abolishes the potential of cancer cells to
become immortal. Specific, separate signalling pathways are
activated in normal, in contrast to tumour, cells in response
to DNA damage. In normal cells, DNA damage results in
p53-dependent transcription of the CDK inhibitor p21. This
causes activation of Rb through inhibition of the CDK that
inactivates Rb. In normal cells, DNA damage evokes
activation of the transcription factor p53, which in turn
up-regulates the expression of CDK inhibitor p21 and BH3-
domain-containing proapoptotic proteins, PUMA and
NOXA. As a consequence of p21 suppression of cyclin
CDK activity, the gene Rb is activated and prevents deam-
ination of Bcl-XL. The intact Bcl-XL inhibits the activity of
BH3-domain-containing proteins, PUMA and NOXA, to
activate Bak/Bax, release of cytochrome c, and caspase
proteolysis. In contrast in tumour cells that lack Rb, deam-
ination occurs leading via the signalling steps to apoptosis
of tumour cell (Li & Thompson, 2002).
2.4. Evading apoptosis
Cells undergo apoptosis through death sensors and
effectors (Evan & Vousden, 2001). Sensors that trigger the
death pathway are linked to apoptosis-inducing ligands.
Apoptosis-inducing factor, a mitochondrial oxireductase, is
released into the cytoplasm to induce cell death in response
to apoptotic signals. Many of the death signals converge on
the mitochondria where the release of cytochrome c cata-
lyses apoptosis (Griffiths et al., 1999). Caspases are death
effector molecules that ultimately transmit the death signal
(Cohen, 1997; Earnshaw et al., 1999).
Evading apoptosis requires mechanisms that inhibit the
transmission of the death signals. Proapoptotic effectors
include B-cell lymphomal leukaemia-2 protein (Bcl-2),
proteins that belongs to the antiapoptotic Bcl-2 family
(Bcl-XL, Mcl-1, and A1) (Attardi et al., 1993). Cytoplasmic
Bcl-2 is a key player in inhibiting signals that converge on
the mitochondria, leading to cell survival. The Bcl-2 family
regulates cell apoptosis in a biphasic manner; Bcl-2 and Bcl-
XL are antiapoptotic, whereas Bax and Bak are proapoptotic
(Evan & Vousden, 2001). Many human cancer cells show
resistance to apoptosis by increasing the ratio of anti to pro
(Evan & Vousden, 2001). Differential regulation of Bcl-XL
modulates sensitivity to apoptosis. Tumour-associated decri-
mination of Bcl-XL occurs because of mutations of two
tumour suppressor genes, p53 and Rb.
Nuclear factor-kB (NF-kB) and serine/threonine kinase
are also associated with cell survival. NF-kB induces the
expression of inhibitor of apoptosis proteins, which bind to
and inhibit certain caspases. NF-kB is a transcription factor
that cooperatively regulates the expression of genes, which
control both innate and adaptive immune responses (Ghosh
& Karin, 2002; Li & Verma, 2002). NF-kB regulates many
genes that control inter- and intracellular signalling, cellular
stress responses, cell growth, survival, and apoptosis (Pahl,
1999). In mammalian cells, NF-kB is regulated by three
isoforms of the inhibitors of KB (IKB) family. When the
NF-kB signalling pathway is activated by TNF, IKB kinases
cause degradation of IKB proteins, which permits accu-
mulation of NF-kB in the nucleus where it binds to DNA
and initiates expression of target genes.
2.5. Angiogenesis
Tumours need oxygen and nutrients, which are provided
by new blood vessels that permeate the tumour mass.
Cancer cells activate the angiogenic switch by secreting
VEGF (Ohm & Carbone, 2001) and acidic and basic FGF1/
2. These growth factors bind to their receptors (VEGFR) on
the endothelial cell and activate signalling pathways that
eventually lead to tumour vascularization. Growth factor
signalling via integrin receptors and transduction by cyto-
kine kinases contributes to angiogenesis. Inhibiting angio-
genesis stops blood vessel formation to the tumour and
starves the tumour of nutrients that are essential for its
survival.
2.6. Metastasis and invasion
Metastasis and invasion involve primary tumour cells
moving out of the tumour mass, invading adjacent tissue,
and travelling to distant sites (Fig. 4). Some mechanisms
through which this may occur involve a change in the
expression of adhesion molecules. The activation of metal-
loproteases, which break down the extracellular matrix
proteins (namely, laminin and collagen), also contributes
to the process of invasion and metastases. Moreover, cell
surface integrin receptors found on invasive and metastatic
cancer cells are able to bind better to the degraded matrix
proteins.
3. Tumour antigens
Antigens are foreign substances recognized by and
targeted for destruction by the cells of the immune system
(Fig. 5). Tumour antigens have been explored because they
Self antigen-presenting cell
Activated macrophage
Activated B cell
Self MHC class II + peptide
TCR CD4 T-cell
Tumour cell
TCR TCR
CD4 T-cell
CD8 T-cell
MHC class I
MHC class II
CD4 T cell cytokine production and clonal expansion
Perforin granzyme
Delayed type hypersensitivity
Antibody production
Cytotoxic T cell mediated cell death
Fig. 5. Cellular interactions that form the immune response against the tumour cell.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 121
elicit an immune response in patients who have cancer but
not in volunteer blood donors or people who do not have
cancer. Tumour cells express specific antigens on the cell
surface, usually within the MHC molecules. The problem
with tumour cells is that they cannot stimulate a T-cell
response by naive T-cells partly because they lack neces-
sary costimulatory molecules. However, dendritic cells (a
type of APC, found in most parts of the body, in the
circulation and on the epidermis as Langerhans cells) can
provide the stimulus by attracting tumour antigens to its
surface by a variety of mechanisms (Chen et al., 2002).
The dendritic cell can then present the tumour antigens on
their surface, lodged within MHC molecules, in a ready
state to activate T-cells (see Fig. 3). Once the T-cells are
activated, they are capable of recognizing and destroying
antigen-expressing tumour cell. Antigen uptake receptors
on dendritic cells provide efficient imitation of antigen-
specific adaptive immunity. The recent recognition of
dendritic cells as powerful APC capable of inducing
primary T-cell responses in vitro and in vivo in combina-
tion with identification of tumour-specific antigens empha-
sizes the role of dendritic cells in antigen recognition
(Cannon et al., 2002).
Tumour-associated antigens are expressed on (i) tumours
caused by physical or chemical environment, (ii) DNA
virus-induced tumours, and (iii) RNA virus-induced
tumours. In the case of tumour-specific antigens induced
by physical or chemical carcinogens, each tumour expresses
unique cell surface antigens. Thus, chemically induced
tumours carry cell surface antigens unique to the specific
tumour but not unique to the inducing chemical. This fact
makes it difficult to develop antigen-specific immunother-
apy since resistance raised to one set of chemically induced
tumour antigens might not prevent the growth of a second
tumour induced by the same chemical.
Oncofoetal tumour antigens are expressed both as self-
antigens during normal foetal development and as cancer
(nonself) antigens later in some adult tumours. These anti-
gens are considered as nonself by the immune system
because they were originally expressed before the individual
became immunocompetent. Although these foetal antigens
are only weakly immunogenic, their presence can be used
diagnostically to detect early cancer growth. Two examples
of antigens normally expressed by foetal, but not adult,
tissue is a-foetoprotein and carcinoembryonic antigen
(CEA). Tumours of the liver, pancreas, and testes most
often express the a-foetoprotein antigen, which is actually
secreted by tumour cells and found in the circulation. CEA
is a membrane protein usually associated with colon, lung,
and bladder cancers. The presence of these two foetal
antigens suggests that undifferentiated tumour cells express
the two proteins as a result of gene activation. The main
value of oncofoetal proteins is diagnostic and in monitoring
the progress of cancer therapy.
Wild-type Wilms’ tumour gene (WT1) is expressed at
high levels not only in most of acute myelocytic, acute
lymphocytic, and chronic myelocytic leukaemia but also in
various types of solid tumours including lung cancer. TGF-bis suppressed by Wilms’ tumour suppressor WT1 gene
product (Dey et al., 1994). The WT1 protein has been
identified as a novel tumour antigen and recent investi-
gations provide a rationale for developing WT1-based T-cell
therapy and vaccination against various kinds of malignant
neoplasms (Oka et al., 2002).
Many tumour antigens have been defined in terms of
multiple solid tumours: MAGE 1, 2, and 3, defined by
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132122
immunity; MART-1/Melan-A, gp100, CEA, HER-2, mucins,
prostate-specific antigen, and prostatic acid phosphatase are
just a short list. Viral proteins—hepatitis B, Epstein-Barr,
and human papilloma—are important in the development of
hepatocellular carcinoma, lymphoma, and cervical cancer,
respectively.
Endogenous HER-2/neu-specific antibody is overex-
pressed in � 20% of human adenocarcinomas and is a
defined tumour antigen in breast cancer (Plunkett & Miles,
2002). HER-2/neu antibodies (titer� 1:100) are detected in
14% (8/57) of patients with colorectal cancer compared with
none of the control population (0/200). Detection of HER-2/
neu-specific antibodies in the patient population is signific-
antly associated with HER-2/neu protein overexpression in
the patients’ tumour (P < 0.01). Nearly half (46%) of the
patients with HER-2/neu-overexpressing tumours (6/13) and
5% of HER-2/neu-negative tumours (2/44) have detectable
HER-2/neu-specific antibodies (Kobayashi et al., 2000).
Tumours induced by oncogenic viruses display cell
surface antigens that are coded from the viral genome. In
case of DNA viruses, these antigens are encoded by virion
DNA sequences and expressed only on transformed cells.
There is extensive cross-reactivity between different onco-
genic DNA viral antigens of the same viral class. Thus,
antigens can be diagnostic of the specific DNA virus or
group and may respond to antigen-specific immunotherapy
(Wilson, 2002).
In contrast, cells transformed by RNA viruses, called
oncornaviruses, show tumour antigens that are also viral
protein products. Therefore, transformed and RNA virus-
infected cells produce the same antigens. Within the oncor-
navirus tumour antigens, one finds (1) group-specific deter-
minants or common antigens that are shared by all viruses in
that group, (2) type-specific products that are displayed only
by tumours induced by only a few closely related viruses
within a group, and (3) unique virus-specific determinants
for only one type of virus. Since it is possible for RNA-
induced tumours to have unique antigens expressed in some
cancers or common antigens in others, it may be possible to
develop separate immunotherapeutic reagents for each indi-
vidual tumour.
4. Immune surveillance and detection of tumours
The question to answer is why, if tumours are immuno-
genic, do cancers continue to proliferate and grow? What
prevents the immune response from destroying the tumour?
One explanation is that in cancer patients the immune
response may not be robust enough.
The immune system identifies tumour cells as ‘‘nonself’’
by several mechanisms, including recruitment of pro-
grammed cell death receptors that cause apoptosis of these
cells. However, tumour cells neutralize the immune system
by evading detection and thereby prevent an immune
response. Currently, there are two concepts regarding the
search for carcinoma cells by the immune system. Immune
surveillance is based on the specific identification of trans-
formed and normal cells through their different antigenic
determinants. The Erhlich-Thomas-Burnet theory of
immune surveillance considers that the immune system
protects against transformed cells carrying foreign, nonself
signals (Burnet, 1970), whereas the Grossman-Heberman
theory proposes an antitumour surveillance system that
regulates self-population of cells (Grossman & Herberman,
1986). In essence, the two concepts of immune surveillance
should theoretically assure apoptosis of cancer cells.
Although the precise nature of the immune system’s role
in cancer has not been fully elucidated, we know that
tumours are immunogenic and that cancer is caused by a
variety of genetic defects that occur in genes that encode for
proteins involved in cell growth. The components of the
immune system, antibodies and T-cells, do not recognize or
respond to defective genes but recognize and respond to the
abnormal proteins the cancer-causing genes encode. Thus,
the individual components of the immune system play a
major role in cancer.
Immune recognition of cancer falls into categories: (1)
the detection of tumour ‘‘markers’’ and (2) the evaluation of
the antitumour response of the host. Tumour products that
are secreted by cancer cells and find their way into the
circulation are the best tumour markers. These include the
oncofoetal antigens, activated fibrinolytic pathway (as
found in pancreatic cancer), and CEA (as it occurs in colon
cancer). If antibodies can be raised to specific tumour
antigens, then these can be subsequently radiolabeled or
configurated with probes and used to locate the tumour by
imaging techniques. Such markers may also be helpful in
determining if the primary tumour has spread into other
organ or tissue sites.
Determination of a tumour-specific immune response can
also be important as a means of demonstrating the presence
of a tumour in the host. Humoral responses can be assessed
by testing for the presence of certain antibodies in serum,
which are diagnostic for certain tumours (namely, melano-
mas and sarcomas). Cell-mediated responses can be meas-
ured after antigen stimulation of host T-cells. In one such
test, the isotope release assay, Tc-cell activity can be
measured. Lymphocytes from the cancer host are incubated
with radiolabeled tumour cells. If the lytic activity of Tc-
cells is high, the levels of radioactivity in the tissue culture
medium should also be high, since, as tumour cells die, they
lyse and release radioactivity into the medium.
Tumour markers and antitumour immune responses have
proved useful in evaluating the progression or regression of
the disease, in a patient’s responses to therapy, and in
determining the recurrence of the disease. For example, it
can be used to monitor activated fibrinolytic pathway and
CEA levels in patients with certain cancers following
primary tumour removal. A rise in the levels of the onco-
foetal antigens postsurgery usually indicates a relapse,
whereas low serum levels indicates continued remission.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 123
The identification of neoplasm-associated markers rec-
ognized by cellular or humoral effectors of the immune
system has opened new perspectives for antigen-directed,
individualised antineoplastic immunotherapy (van den
Eynde, 2002). In preparation for this new era of targeted
immunotherapy, a number of neoplasm-associated antigen
families have been identified as targets for CD8+, cytolytic
T-lymphocytes in vitro and in vivo: (1) cytotoxic T-cell
antigens expressed in various neoplasms and in normal
testis, restricted to male germ cells, (2) melanocyte differ-
entiation antigens, (3) point mutations of normal genes, (4)
antigens overexpressed in neoplastic tissues, and (5) viral
antigens (Bodey, 2002).
5. Immune-directed apoptosis of cancer cells
As with foreign grafts (Krensky et al., 1990) and virus-
infected cells, the T-lymphocyte plays a major role in the
destruction of tumour cells in mammals (Scaffidi et al.,
1999). T-cell activation includes the generation of helper,
sensitised, and cytotoxic subset clones. The sensitised T-
cells can affect killing of tumour cells by means of the
lymphokines that they release. Lymphokines mobilize and
activate B-cells through B-cell growth factors and B-cell
differentiation factors. The expression of foreign tumour
antigens on the surface of a cancer cell can be provoked by
activation of immunocytes. This activation leads to the
formation of clones of plasma cells that produce antibodies
that are specific for determinants expressed on the surface of
cancer cells. In turn, these give rise to a range ADCC
reactions. At one level, complement-fixing antibodies can
directly bind to the tumour antigens and lyse the cells by
complement activation (Kulcsar, 1997a). On the other hand,
effector cells, such as cytotoxic killer cells and macro-
phages, carrying Fc receptors may be recruited for tumour
killing by Fc receptor binding to the cancer cell membrane
(Peipp & Valerius, 2002). The binding of antibody to the
tumour cell would trigger opsonization, which would facil-
itate phagocytosis of the cancer cell. In addition, some
lymphocytes (e.g., NK cells and lymphokine-activated killer
cells) can be similarly recruited. Moreover, complement
activation would lead to generation of C3a and C3b
complement fragments. C3a is chemotactic for neutrophils,
whereas C3b induces macrophages enzyme release. Thus,
complement-activated neutrophils and macrophages lead to
cytolysis of tumour cells. A second set of lymphokines may
activate phagocytes of the reticuloendothelial system. These
lympokines include migration-inhibiting and chemotactic
factors, and macrophages recruited by these lympokines
phagocytoze, digest, and kill the tumour cells.
In addition, the lymphokine IFN, an immunomodulator
produced by the T-cell immune response, regulates T-cell
functions and B-cell antibody production and enhances the
tumouricidal activity of NK cells and macrophages. A very
important regulatory role of IFN in tumour killing may be
achieved by amplifying the NK cell population, a hetero-
geneous group of granular lymphocytes that appear very
effective in lysing target cancer cells through cell-to-cell
contact without prior sensitisation. Tumour cells of various
types possess unique sets of tumour markers that can be
recognized by NK cells. In addition, the lytic process
involves the release of cytotoxic factors for which there
seem to be more receptors on the surface of target cancer
cells than on nonmalignant self cells. Thus, the efficiency of
tumour killing by NK cells is both high and specific for
tumour cell (Coleman et al., 1992).
Macrophages and NK cells exert their tumouricidal
effects through different mechanisms. From in vitro studies,
it appears that macrophages can eliminate tumour cells
through both cytolysis and phagocytosis (Gough et al.,
2001; Bingle et al., 2002). It has been shown that the
efficiency of cytolysis of tumour cells by macrophages is
increased by the presence of activated lymphocytes or their
product, the lymphokines (Hamilton & Adams, 1987; Lewis
& McGee, 1992; Paulnock, 1992). The events leading to
cytotoxic macrophage killing are still unclear. Lysis of
tumour cells by NK cells seem to be another important
immune defense against cancer. NK cells are null cells,
neither B-lymphocytes nor T-lymphocytes, comprising 5–
15% of the total lymphocyte population of blood that is
restricted from the spleen, lymph nodes, and bone marrow.
They have a broad specificity, are non-MHC restricted, and
seem to recognize cancer cells by an unidentified NK target
receptor. However, recent studies indicate that the degree of
response of NK cells to tumour cells is inversely related to
the expression of MHC class I antigens. In particular,
tumour cells that express little or no MHC class I antigens
are more readily attacked by NK cells than are those that
express greater amounts of MHC class I antigens. Never-
theless, although NK cell killing is not MHC restricted, it
appears to be influenced by MHC expression. The killing
process is mediated by cell-to-cell contact, leading to
cytolysis where the target cell is destroyed but not the NK
cell. In vitro studies have demonstrated that the NK cell is
responsible for cytolytic activity against a variety of tumour
cell lines. The role of immune modulators in regulating NK
activity is still unclear.
6. Tumour escape mechanisms
When cells become cancerous, they produce new, unfa-
miliar antigens. The immune system may recognize these
antigens as nonself and contain or even destroy them.
However, the immune responses elicited by tumour antigens
are not potent, since most are ‘‘self-proteins.’’ The immune
system tolerates self-proteins, thereby providing a mech-
anism by which cancer cells can evade immune recognition.
Decreased immune function in cancer patients is well
characterized, and tumour cells have developed a variety of
mechanisms to avoid antitumour immune responses.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132124
Although not completely understood, immune escape strat-
egies include (1) ‘‘sneaking through,’’ (2) modulating
tumour antigens, (3) masking tumour antigens, (4) inducing
tolerance, (5) producing blocking antibodies, and (6) pro-
ducing or expressing immunosuppressants (Coleman et al.,
1992).
One way cancer cells can avoid immune cytolysis is
because some tumours are only weakly immunogenic, so
that the small number of cells do not elicit an immune
response. However, when their numbers increase enough to
provoke an immune response, the tumour load may be too
great for the host’s immune system to mount an effective
response. The immune system and tumour may have inter-
acted in such a manner so as to suppress the immune
system’s detection and subsequent cytotoxic response.
Some tumour cells modulate tumour cell surface antigens
and thereby avoid detection. Certain tumour cells may
transfer antigens from their surface into the cytoplasm,
making themselves immunologically invisible. Alternately,
tumour cells might stop expressing certain surface antigens.
For example, tumour cells that are H-2K + may be destroyed
by Tc-cells. However, tumour cells that are H-2K � do not
evoke this cytolytic response. This assures a loss of recog-
nition, making the tumour cells no longer foreign, thus
avoiding recognition and the resultant lysis. In addition,
tumour cells may alter expression of cell adhesion mole-
cules and thereby reduce the formation of stable contacts
with cytolytic cells. Antigen modulation can also be affected
by redistributing the antigen within the cell membrane in
such a way as to prevent immune reaction. Moreover,
tumour antigens can be removed from the surface of the
cancer cell by ‘‘shredding.’’ This loss of tumour antigens
desensitises the cancer cells and protects them against
cytolysis.
Another strategy used is to devise a cloaking mechanism
that renders the cell invisible by the formation of the
mucoprotein, sialomucin, which coats and masks surface
tumour antigens. Since sialomucin is a normal (self) com-
ponent, the immune system cannot ‘‘see’’ through the
surface microprotein layer and avoid detection by the host
immune system. Certain types of tumours can synthesize
various immunosuppressants, thereby be able to actively
suppress the immune response. This would result in a state
of immune tolerance to the cancer, which could then be free
to invade adjacent normal tissue.
The receptor of the Ig superfamily, PD-1, negatively
regulates T-cell antigen receptor signalling by interacting
with the specific ligands (PD-L). This receptor is suggested
to play a role in the maintenance of self-tolerance. The
expression of PD-L1 can serve as a potent mechanism for
potentially immunogenic tumours to escape from host
immune responses and that blockade of interaction between
PD-1 and PD-L may provide a promising strategy for
specific tumour immunotherapy (Iwai et al., 2002).
Cancer cells may stimulate the immune system to express
blocking antibodies, which cannot activate complement, so
lysis of the cell is not possible. This also means that no C3a
or C3b is formed. Blocking antibodies also cover the surface
of cancer cells, preventing Tc-cells from binding to the
hidden receptors. In this way, killing of tumour cells by
compliment and Tc-cells is prevented. Synthesis of the
blocking antibodies has been shown to enhance tumouri-
genesis. Furthermore, the associated decline in immunity
results in a progressive fall in immune responsiveness to all
foreign antigens as the disease progresses.
One mechanism for inhibition of immune cell function
by tumours is the production of soluble factors, such as IL-
10, TNF, TGF-b, and VEGF. The effects of these factors
appear to be 2-fold: to inhibit effector function and to impair
the development of immune cells by acting on earlier stages
of immunopoiesis. Immune suppression by tumours is
accomplished by a variety of cellular and molecular mech-
anisms, and virtually all branches of the immune system can
be affected. VEGF and its receptors have profound effects
on the early development and differentiation of both vas-
cular endothelial and haematopoetic progenitors. It induces
proliferation of mature endothelial cells and is an important
component in the formation of tumour neovasculature.
VEGF is abundantly expressed by a large percentage of
solid tumours and this overexpression is closely associated
with a poor prognosis. Some of the earliest haematopoietic
progenitors express receptors for VEGF (Ohm & Carbone,
2001).
7. Cancer immunotherapy
7.1. Molecular aspects of immunotherapy
Immune-directed cancer therapy essentially has to pre-
serve normal cells and kill tumour cells. The exploitation of
biological differences between normal and malignant cells is
a logical approach to novel treatments for cancer. A century
has passed since the first attempt was made to stimulate the
host immune system against cancer. Recognizing the
immune system’s remarkable ability to defend the body
against disease, a new approach to the treatment of cancer
has been immunotherapy. The aim of cancer immunother-
apy is to bolster the immune system so that it is better able
to combat cancer cells. Clinically effective cancer immuno-
therapy has been sought for more than 100 years. The
identification of tumour-associated antigens recognized by
cellular or humoral effectors of the immune system has
opened new perspectives for cancer immunotherapy. Differ-
ent categories of cancer-associated antigens have been
described as targets for CD8+ T-cells in vitro and in vivo:
(1) ‘‘cancer’’ antigens expressed in different tumours, (2)
melanocyte differentiation antigens, (3) point mutations of
normal genes, (4) antigens that are overexpressed in malig-
nant tissues, and (5) viral antigens (Jager et al., 2001a).
Immunotherapeutic protocols directed against the cytotoxic
T-cell antigens are being used to analyse the induction of
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 125
antigen-specific cellular and humoral immune responses in
vivo (Bodey, 2002).
Over the last decade, there has been a rapid expansion in
the field of tumour immunology. There is now convincing
evidence that both cellular and humoral arms of the immune
system are capable of interacting with tumour cells. As
understanding of how T-cells interact with the micro-
environment of the immune system and how antigens are
recognized has heightened, greater clarity has been attained
with regard to the immune response against cancer cells.
Understanding this antigen recognition pathway and the role
of helper T-cells in enhancing cytotoxic T-cells or antibodies
has encouraged new concepts for immunotherapy (Wang et
al., 2002). Therefore, the feasibility of stimulating specific
immune responses that would be therapeutically effective is
being pursued. In order to achieve this goal, the specific
arms that recognize particular antigens have to be identified.
The most significant advances have been in our under-
standing of cellular responses and the complex events that
lead to T-lymphocyte activation as well as in the identifica-
tion of tumour antigens recognized by T-lymphocytes. This
knowledge has led to the development of anticancer immu-
notherapies designed to produce tumour antigen-specific T-
cell responses, adding to the earlier antibody or whole-cell
vaccine approaches. In addition, new methods have been
developed to quantify antigen-specific T-cell responses, and
the emergent field of recombinant gene technology has led
to an increasing number of novel methods for vaccine
delivery (Smith et al., 2002).
Clinical studies with peptides and proteins derived from
these antigens have been initiated to study the efficacy of
inducing specific CTL responses in vivo. Immunological
and clinical parameters for the assessment of antigen-spe-
cific immune responses are defined-delayed type hypersens-
itivity, CTL, autoimmmune, and tumour regression
responses. Specific defined-delayed type hypersensitivity
and CTL responses and tumour regression have been
observed after the intradermal administration of tumour-
associated peptides alone. Peptide-specific immune reac-
tions are enhanced after using GM-CSF as the systemic
adjuvant and by increasing the frequency of dermal antigen
presented to Langerhans cells. Complete tumour regression
has been observed in the context of measurable peptide-
specific CTL. However, in single cases with disease pro-
gression after an initial tumour response, either a loss of
single antigen targeted by CTL or the loss of presenting
MHC class I allele points towards immunization induced
immune escape (Jager et al., 2001b).
Heat shock proteins (HSP) act as molecular chaperones
binding endogenous antigenic peptides and transporting
them to MHC. HSP chaperones a broad repertoire of
endogenous peptides including tumour antigens. For the
immunotherapy of tumours, a strategy using HSP may be
more advantageous than other procedures because the
identification of each tumour-specific antigen does not
become necessary (Sato et al., 2001).
8. Immunotherapeutic strategies
Currently, several forms of immunotherapy are being
explored. The majority if these approaches use natural
biological products obtained to activate the immune
system through genetic engineering and hybridoma tech-
niques. The various forms of immunotherapy fall into
three main categories: monoclonal antibodies, immune
response modifiers, and vaccines. The antibody-based
therapies are a form of passive immunotherapy (Kulcsar,
1997b). That is, the molecules or substances are intro-
duced into the body rather than the body creating its own
immune response. Vaccines, on the other hand, are
considered to constitute active immunotherapy because
they generate an intrinsic immune response. They are
also considered to be a form of specific immunotherapy
because they attempt to stimulate an immune response
that can directly target the tumour antigens in contrast to
nonspecific approaches such as cytokines that broadly
stimulate the immune system.
8.1. Monoclonal antibodies
In recent years, antibody therapy has become a new
treatment modality for tumour patients (Trauth et al., 1989).
Based on evidence that effector cell-mediated mechanisms
significantly contribute to antibody efficacy in vivo, several
approaches are currently pursued to improve the interaction
between Fc receptor-expressing effector cells and tumour
target antigens. These approaches include application of Fc
receptor-directed bispecific antibodies, which contain one
specificity for a tumour-related antigen and another for a
cytotoxic Fc receptor on immune effector cells. Thereby,
bispecific antibodies selectively engage cytotoxic trigger
molecules on killer cells, avoiding, for example, interaction
with inhibitory Fc receptors. In vitro, chemically linked
bispecific antibodies directed against the Fc g-receptors
FcgRIII (CD16) and FcgRI (CD64) and the Fc a-receptorFcaRI (CD89) are significantly more effective than con-
ventional IgG antibodies. However, results from clinical
trials have been less promising so far and have revealed
clear limitations of these molecules, such as short plasma
half-lives compared with conventional antibodies (Peipp &
Valerius, 2002).
The potential targets for such therapy include the
products of protooncogenes and oncogenes, the inhibition
of growth factor receptor signalling, and the immuno-
logical exploitation of antigenic differences between nor-
mal and malignant cells. Monoclonal antibody technology
was heralded as a potential ‘‘magic bullet’’ for cancer
therapy following its evaluation in the mid-1970s, but it
is only in the past few years that such technology has
entered mainstream clinical practice. Monoclonal antibod-
ies directed against tumour-specific agents have been
approved for the treatment of breast cancer (trastuzumab)
and non-Hodgkin’s lymphoma (rituximab) and for the
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132126
diagnosis of certain cancers (oncoscint) (Plunkett &
Miles, 2002).
Antibodies can be targeted to specific cancer antigens.
Monoclonals can then aid in the diagnosis and treatment of
antigens that distinguish cancer cells from normal cells.
Desmoplastic small round cell tumour is an aggressive and
often misdiagnosed neoplasm of children and young adults.
It is chemotherapy sensitive, yet patients often relapse after
therapy because of residual microscopic disease at distant
sites. Strategies directed at minimal residual disease may be
necessary for cure. Monoclonal antibodies selective for cell
surface tumour-associated antigens may have utility for
diagnosis and therapy of microscopic disease at distant, as
recently demonstrated in advanced-stage neuroblastoma
(Modak et al., 2002). Furthermore, monoclonals serve as
powerful tools to define, treat, and monitor recurrences of
previously treated cancers.
8.2. Immune response modifiers
These are molecules, either extrinsic or intrinsic to the
host, that affect the immune response. One group of
extrinsic modifiers is referred to as immune potentiators.
These include BCG, C. parvum and endotoxin, which are all
microbes or microbial products that have been shown to
modify the immune response and, under certain conditions,
to cause tumours to regress or grow more slowly than usual.
The intrinsic group, known as biological response modi-
fiers, includes IL-1, IL-2, IFN (a, b, and g), TNF, B-cell
growth factors, and haematopoietic growth factors (such as
colony stimulating factors). These agents exert their influ-
ence at different stages of the immune response.
Haematopoietic growth factors are often combined with
chemotherapy and radiotherapy to restore bone marrow
function. Thalidomide, which suppresses TNF-a produc-
tion and has antiangiogenic properties, is currently under
evaluation in several cancers. Currently, there are more
than 20 IL (IL-1 to IL-18) and at least 5 other proteins
have just been found which are likely to be termed IL. The
cellular sources and functions of these IL are provided in
Table 1. Cytokines, the messengers of the immune system,
are either proteins or glycoproteins, secreted by immune
cells. They have autocrine and paracrine functions, so that
they function locally or at a distance to enhance or
suppress immunity. Currently, in cancer therapy, cytokines
are used to enhance immunity. They also regulate the
adaptive immune system, the T- and B-cell immune
responses. In the immune system, cytokines function in
cascades. Thus, clinical trials of individual cytokines are
rarely useful, since cytokines tend not to work individu-
ally but probably cooperatively. Some of the individual
cytokines that have been tested and found ineffective for
cancer treatment include IL-1b, although it may be useful
still because it helps to mediate the severe toxicity of IL-
2. IL-2 is the most widely studied IL and is used for
immunostimulation in metastatic renal cell carcinoma and
malignant melanoma. Although the use of TNF certainly
sounded promising, but because it caused severe hypo-
tension when used systemically, its value is limited. IL-4
shows minimal anticancer activity and is toxic. IL-6 has
some activity against cancer cells but turns out to be a
growth factor for myeloma cells. GM-CSF, used prim-
arily in stem cell transplant to reconstitute the myeloid
series, has been studied for melanoma with controversial
results.
Which cytokines are important for cancer? IL-2 and IFN-
a-2b are two cytokines approved by the Federal Drug
Agent for treatment of cancer. IL-2 has demonstrated
activity against renal cell, melanoma, lymphoma, and leuk-
aemia. IFN has activity in the same histologies but also in
Kaposi’s sarcoma, chronic myelogenous leukaemia, and
hairy cell leukaemia (HCL). Overall, the major cytokines
IFN-a, IL-2, GM-CSF, and IL-12 are being currently
evaluated for cancer therapy, since they appear to have
application in the treatment of haematologic malignancies
or immunogenic tumours.
8.2.1. Interferon-�IFN was isolated in 1970 from white cells and called IFN
because it interfered with viral infection. IFN-a is actually a
family of molecules comprising at least two types. They are
encoded by closely related genes on chromosome 9, encod-
ing proteins that are variably glycosylated. These are com-
prised of about 150 amino acids and bind to certain
receptors on the surface of immune cells. They are known
to have profound and diverse effects on gene expression.
IFN-a has many roles. It up-regulates genes like MHC class
I, tumour antigens, and adhesion molecules. It is also an
antiangiogenic agent, which is very active in the immune
system, promoting B- and T-cell activity. IFN-a stimulates
macrophages and even dendritic cells and up-regulates Fc
receptors. The mode of action of IFN-g appears to be
through activation of the host immune system, which
depends on the intrinsic immunogenicity of the target
tumour cell (Gri et al., 2002).
IFN’s activity in cancer has been well documented
(Quesada et al., 1986; Dorval et al., 1987; Allan et al.,
1995; Kirkwood et al., 1996, 2000, 2001) and is indicated
for the treatment of certain leukaemias and Kaposi’s sar-
coma in order to inhibit tumour proliferation and angio-
genesis. The efficacy of IFN-a has been well established for
the treatment of advanced melanoma and renal cell carcin-
oma patients (Bukowski et al., 2002). Small but consistent
response rates have been observed in a number of other
studies. HCL is a rare lymphoproliferative disease. IFN-adramatically improves the survival of HCL with haemato-
logical values returning to normal and the disappearance of
circulating hair cells in most patients (Zinzani et al., 1997).
HCL is a B-cell malignancy that is highly sensitive to the
immune modulator, IFN-a, which acts by up-regulating
endogenous TNF-a and by restoring the efficacy of the T-
cell receptor family (Baker et al., 2002).
y & Therapeutics 99 (2003) 113–132 127
8.2.2. Interleukin-2
IL-2 is a T-cell growth factor that binds to a specific
tripartite receptor on T-cells. Current clinical trial data
suggest that combined IL-2 and IFN-a administered sub-
cutaneously in accordance with specified regimes achieves
long-term survival benefits in subsets of patients with
metastatic renal cell carcinoma (Atzpodien et al., 2002).
Combining immune modulators may be a way forward for
metastatic carcinomas. The immunobiological agents, IL-2
and IFN-a, when combined with meroxyprogesterone,
produces a good response rate and low toxicity (Naglieri
et al., 2002). However, it should be remembered that clinical
trials restricted to combinations of IL-2 and IFN-a alone
have given contradictory results in the treatment of meta-
static renal cell carcinoma (Ravaud et al., 2002).
8.2.3. Interleukin-12
IL-12 is a very exciting cytokine. It is a heterodimeric
protein that promotes NK and T-cell activity and is a growth
factor for B-cells. IL-12 plays a central role in T-cell-
mediated immune responses. Endogenously formed IL-12
confers T-cells with a tumour migratory capacity and at the
same time entices tumour cells to accept tumour-migrating
T-cells (Uekusa et al., 2002). It has demonstrated antitumour
activity in mouse models. Alone, IL-12 shows minimal
potential for therapeutic effect (Atkins et al., 1997). Essen-
tially, the efficacy of IL-12 is dependent on stimulating Th1cells to release IFN-g (Segal et al., 2002). Furthermore, IL-
12 may have value also as a vaccine adjuvant. When IL-12
was paired with peptide vaccines in patients with resected
stages 3 and 4 melanoma, IL-12 appeared to boost the
response to the vaccine (Lee et al., 2001).
8.3. Colony stimulating factor
Cancer vaccines composed of tumour cells engineered to
secrete the cytokine, GM-CSF, are currently being clinically
evaluated. Although immune recognition of tumours is
known to occur, the failure of the host to either suppress
or attenuate progression of the disease may reflect limited
immunogenicity arising from the absence of critical deter-
minants like the tumour augmenting family of cytokines
(Dranoff, 2002). To enhance the immunogenicity of GM-
CSF-secreting tumour cell vaccines, a novel approach
expressing GM-CSF as a membrane-bound form (mbGM-
CSF) on the tumour cell surface has been investigated. The
intent is to enhance antigen presentation by increasing
interactions between the tumour cell lines in the vaccine
and GM-CSF receptor-positive APC, notably the patient’s
Langerhans cells (dendritic cells) residing within the intra-
dermal injection site. Tumour cells have been engineered to
express either membrane-bound or secreted GM-CSF (Yei et
al., 2002). GM-CSF has been approved also for use in stem
cell and bone marrow transplant to reconstitute the myeloid
series. GM-CSF is also being evaluated as an adjuvant for
vaccine therapy.
J.K. Adam et al. / Pharmacolog
New advances in GM-CSF or cytokine-linked immuno-
therapy devised for pre-B acute lymphocytic leukaemia and
acute myeloid leukaemia attempt to modify acute leukaemia
cells into functional APC. These cells can then be used as
autologous vaccines at the time of minimal residual disease
after standard chemotherapy to stimulate host immune
responses against their own leukaemia cells. The various
approaches toward this aim include incubation of leukaemia
cells with cytokines or growth factors and gene manipula-
tion of these cells. In particular, ex vivo culture of acute
lymphocytic leukaemia cells with CD40 ligand, incubation
of acute myeloid leukaemia cells with GM-CSF and IL-4
(GM-CSF/IL-4), and lentiviral transduction of acute lym-
phocytic leukaemia and acute myeloid leukaemia cells for
expression of immunomodulators (CD80 and GM-CSF) are
current approaches for the development of autologous acute
leukaemia cell vaccines (Stripecke et al., 2002).
The serological prostate-specific antigen progression of
prostate cancer can be reduced significantly following
subcutaneous injection of GM-CSF (Rini et al., 2003).
Expression of plasmids encoding GM-CSF and IL-2 suc-
cessfully produce protective immune responses in animals
immunized with transfected malignant plasma cells (Galea
& Cogne, 2002). However, the optimum choice of antigen,
delivery vector and adjuvant, and administration regimen
for some of these biological response modifiers are still
being investigated (Gupta & Kanodia, 2002).
8.4. Vaccination against tumours
Efforts to treat cancer with vaccines date back to the
origins of immunology. Although cancer immunotherapy
was initiated by William Coley more than a century ago, the
field of cancer vaccines is in an early stage of development
(Espinoza-Delgado, 2002). Only recently, major advances in
cellular and molecular immunology have allowed a com-
prehensive understanding of the complex and high rate of
interactions between the immune system and tumour cells.
Tumour-immune system interactions result either in strong
immune antitumour response or in tolerance to tumour-
associated antigens.
It is now clear that many human tumour antigens can be
recognized by the immune system. These tumour antigens
can be classified into several groups including tissue-spe-
cific differentiated, overexpressed, and viral-associated anti-
gens. In many cases, there is a known molecular basis of
carcinogenesis, which provides the explanation for the
differentiated expression of antigens in tumours when
compared with normal cells. Improved understanding of
the biology of the immune response, particularly of immune
recognition and activation of T-cells, allows better design of
vaccines. Preclinical comparative studies permit evaluation
of optimal vaccine strategies, which can then be delivered to
the clinic. Currently, a range of cancer vaccines are being
tested including those using autologous and allogeneic
tumour cells, proteins, peptides, viral vectors, DNA, or
Table 4
Tumour cell vaccines
Type Vaccine Reference
Tumour cell
vaccines
Melanoma tranduced
with Ad-GM-CSF
Kusumoto et al., 2001
Allogeneic panc.,
tumour-secreting GM-CSF
Jaffee et al., 2001
CancerVax Hsueh et al., 1998
Autologous colon
CA+BCG
Hanna et al., 2001
Autologous GBM+
Newcastle virus
Schneider et al., 2001
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132128
dendritic cells (Dermime et al., 2002; Liu et al., 2002).
Patients have been injected with autologous and allogeneic
tumour and dendritic cell vaccines (Plunkett & Miles,
2002). However, measuring immune response has been
problematic. Now that several tumour antigens have been
identified and the immune response they provoke, progress
has been made in developing cancer vaccines. Vaccines
consisting of peptide or protein administered with an adjuv-
ant have been the most frequently used. These adjuvants
might be compounds such as tumour cell wall components
or cytokines such as IL-12 or GM-CSF that incite a local
response. Monocytes, neutrophils, eosinophils, and T-cells
are all recruited to the site where adjuvant is used, but it is
believed that in situ dendritic cells ultimately take up the
tumour proteins and peptides, process them if necessary, and
present them on the cell surface as peptides capable of
binding to the MHC molecules. Dendritic cells can then
stimulate T-cells that have the receptors to recognize those
particular peptides.
Substantial data from several preclinical models and
early human clinical trials have confirmed the ability of
cancer vaccines to induce immune responses that are tumour
specific and, in some cases, associated with clinical
responses. One future challenge will be to determine how
to appropriately stimulate the pathways leading to effective
interaction among APC, T-lymphocytes, and tumour cells. It
also is critical to develop monitoring strategies that may
allow the identification of patients who may benefit from
cancer vaccines (Espinoza-Delgado, 2002).
Tumour cell-based vaccines are another vital area of
research (Ward et al., 2002). Some studies have used
autologous tumour, in which tumour cells are extracted
from surgical resection or biopsy specimens. Allogeneic
cell lines have also been developed for tumours such as
melanoma that likely encompass many of the tumour-
associated antigens expressed by the melanomas of most
affected individuals (Lauerova et al., 2002). Tumour cells
can also be modified to make them more immunogenic. To
accomplish that, tumour cells may be infected with various
types of viruses so that viral proteins are expressed on the
surface and transduced with genes expressing cytokines
such as IL-2 and GM-CSF or genes for HLA molecules or
costimulatory molecules. The idea is to irradiate the cells so
they can no longer proliferate then inject the tumour cells
back into the patient. The expectation is activation of the
immune system by either the tumour cells or the inflam-
matory response that includes recruitment of dendritic cells.
As the injected tumour cells undergo apoptosis or are
destroyed by the inflammatory reaction, antigens are picked
up by the dendritic cells and represented to the T-cells
(Morse et al., 1999).
The results of some of the current research on tumour
vaccines are illustrated in Table 4. These studies employed
several strategies. One of the most popular is to transduce
with a vector containing GM-CSF so that the tumour
secretes GM-CSF and sets up an inflammatory response.
In animal studies, this strategy has been the most promising
in inducing a protective immune response. Newcastle dis-
ease virus has antineoplastic and pleitropic immune stim-
ulatory properties. It alters the immunogenicity of tumour
cells. The virus preferentially replicates in and kills tumour
cells. The attenuated Newcastle disease virus vaccine causes
regression of human neoplasms and has been used for the
treatment of malignant melanoma. The mechanism of its
oncolytic action appears to affect specific signalling path-
ways of the tumour cell (Termeer et al., 2000; Fabian et al.,
2001; Schirrmacher et al., 2001).
Use of Bacille Calmette-Guerin as an inflammation-
inducing adjuvant along with autologous colorectal cancer
cells showed increased defined-delayed type hypersensitiv-
ity but no survival benefit (Smith et al., 2002). In fact, most
of these tumour cell approaches show an immune response
but have again been of limited clinical value. Nonetheless,
Cancer Vax70 tested on nonrandomized studies has
recorded survival benefits in melanoma.
Despite the identification of tumour antigens and their
subsequent generation in subunit form for use as cancer
vaccines, whole tumour cells remain a potent vehicle for
generating antitumour immunity. This is because tumour
cells express an array of target antigens for the immune
system to react against, avoiding problems associated with
MHC-restricted epitope identification for individual pa-
tients. Furthermore, whole cells are relatively simple to
propagate and are potentially efficient at contributing to
the process of T-cell priming. However, whole cells can also
possess properties that allow for immune evasion, so the
question remains of how to enhance the immune response
against tumour cells so that they are rejected. Scenarios
where whole tumour cells may be utilised in immunother-
apy include autologous tumour cell vaccines generated from
resected primary tumour, allogeneic (MHC-disparate) cross-
reactive tumour cell line vaccines, and immunotherapy of
tumours in situ. Since tumour cells are considered poorly
immunogenic, mainly because they express self-antigens in
a nonstimulatory context, the environment of the tumour
cells may have to be modified to become stimulatory by
using immunological adjuvants. Recent studies have reeval-
uated the relative roles of direct and cross-priming in
generating antitumour immunity and have highlighted the
need to circumvent immune evasion (Ward et al., 2002).
Table 5
Viral vector and plasmid vaccines
Type Vaccine Reference
Viral vector and ALVAC-CEA B7.1 von Mehren et al., 2001
plasmid vaccines Vaccinia CEA/avipox-
CEA+GM-CSF
Marshall et al., 2000
Vaccinia CEA Conry et al., 1999
PSMA/CD86 plasmid Mincheff et al., 2000
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 129
The development of genetically modified tumour vac-
cines has been prompted by a better understanding of
antitumour immune responses and genetic engineering tech-
nologies as well as the identification of numerous tumour
antigens in several malignancies, which occasionally induce
spontaneous tumour regressions. Cellular vaccines are based
on autologous or allogeneic tumour cells genetically engi-
neered to secrete different cytokines, costimulatory mole-
cules, or allogeneic HLA molecules programmed to provide
a strong stimulatory signal. Another promising approach
that is targeted towards breaking immune tolerance to
tumour antigens exploits dendritic cells loaded with gen-
etically modified tumour antigens (Liu et al., 2002). Effect-
ive nonviral and viral gene delivery systems have been
constructed including a third generation of adenoviral,
lentiviral, and hybrid vectors (Nawrocki et al., 2001).
In active immunization, cancer prevention is attempted
by vaccinating with actual inactivated tumour cells or their
antigens. Tumour cells are emulsified in Freund’s adjuvant
and injected prior to tumour challenge in animals. One
oncogenic viral vaccine, feline leukaemia vaccine, has been
very effective in reducing the incidence of leukaemia in the
domestic cat population. However, immunization against
the tumour itself depends on both the presence of tumour
cell surface antigens that can be ‘‘seen’’ by the immune
system and the appropriate cytotoxic responses by the
immune system. To date, most anticancer vaccines have
failed—either because the tumour’s antigenicity is somehow
hidden or because the immune system responds by pro-
ducing blocking antibodies that enhance tumour growth.
Cancer is a multigenic disorder involving mutations of
both tumour suppressor genes and oncogenes. A large body
of preclinical data, however, has suggested that cancer
growth can be arrested or reversed by treatment with gene
transfer vectors that carry a single growth inhibitory or
proapoptotic gene or a gene that can recruit immune
responses against the tumour. Many of these gene transfer
vectors are modified viruses that retain the capability of the
virus for efficient gene delivery but are safer than the native
virus due to modifications that eliminate or alter one or more
essential viral functions. In the field of viral-based gene
transfer, vectors for the treatment of cancer, vectors and
indeed naked DNA in the form of plasmids encoding
tumour antigens, can be used to immunize people (Wilson,
2002). Initially, these vaccines were administered to muscle
cells, but it is likely that dendritic cells were ultimately the
targets infected by the virus or were picking up the antigen
released by apoptotic muscle cells. Poxviruses are another
popular way to apply this approach, and a considerable
amount of work has been done with vaccinia and avian and
fowl pox vectors. One of the most interesting strategies is
the prime boost approach. An example of this is when a
patient is first immunized with vaccinia virus encoding the
gene for CEA.
Vaccinia is very immunogenic, so it can only be used once
or twice—after the first injection patients develop high
neutralizing antibody titers. In subsequent immunizations,
the antibody immediately binds to the virus, making it
difficult to get true immunization against the encoded tumour
antigen. However, an avian vector expressing CEA is used
and better immunologic responses are observed (Marshall et
al., 2000). Prostate cancer is a disease that may be amenable
to immunotherapy approaches, as evidenced by the ability to
induce human cytotoxic immune responses against prostate
cancer cells. Recent interest in recombinant poxvirus vac-
cines coupled with the need for new prostate cancer therapies
has led to the development of several recombinant poxvirus
agents designed for prostate cancer treatment. Whether these
agents will be effective in treating prostate cancer is under
investigation in several ongoing and upcoming clinical trials
(see Table 5) (Hwang & Sanda, 1999).
Cancer vaccines are injected with appropriate boosters to
stimulate an immune response to a specific type of cancer.
Current development efforts are centred on vaccines for
melanoma, rectal cancer, and breast cancer as well as other
cancers. Vaccines may someday serve as cancer prophy-
lactic modules, which by creating a state of acquired
immunity stop specific types of cancer from recurring in
people previously afflicted by them.
Acknowledgments
Research grant support from the Medical Research
Council (MRC, SA) and National Research Foundation
(NRF, SA) is much appreciated. We thank Celia Snyman for
the figure drawings and Bonita Jeena for assisting with the
manuscript.
References
Adler, H. L., McCurdy, M. A., Kattan, M. W., Time, T. L., Scardino, P. T.,
& Thompson, T. C. (1999). Elevated levels of circulating interleukin-6
and transforming growth factor-beta1 in patients with metastatic pro-
static carcinoma. J Urol 61, 182–187.
Allan, N. C., Richards, S. M., & Shepherd, P. C. (1995). UK Medical
Research Council randomized, multicenter trial of interferon alfa n1
for chronic myeloid leukaemia: improved survival irrespective of cyto-
genetic response. Lancet 345, 1392–1397.
Arend, W. P. (1993). IL-1 receptor antagonist. Adv Immunol 54, 167–227.
Arend, W. P., & Dayer, J. M. (1990). Cytokines and cytokine inhibitors or
antagonists in rheumatoid arthritis. Arthritis Rheum 33(3), 305–315.
Atkins, M. B., Roberston, M. J., Gordon, M., Lotze, M. T., DeCoste, M.,
DuBois, J. S., Ritz, J., Sandler, A. B., Edington, H. D., Garzone, P. D.,
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132130
Mier, J. W., Canning, C. M., Battiato, L., Tahara, H., & Sherman, M. L.
(1997). Phase I evaluation of intravenous recombinant human interleu-
kin-12 in patients with advanced malignancies. Clin Cancer Res 3,
409–417.
Attardi, L. D., Reczek, E. E., Cosmas, C., Demicco, E. G., McCurrach,M. E.,
Lowe, S.W., Boise, H. L., Gonzales-Garcia,M., Postema, E. C., Ding, L.,
Lindstein, T., Turka, A. L., Mao, X., Nunez, G., & Thompson, C. B.
(1993). Bcl-x, a Bcl-2 related gene that function as a domain regulator of
apoptotic cell death. Cell 74, 597–608.
Atzpodien, J., Hoffmann, R., Franzke, M., Stief, C., Wandert, T., & Reitz,
M. (2002). Thirteen-year, long-term efficacy of interferon 2alpha and
interleukin 2-based home therapy in patients with advanced renal cell
carcinoma. Cancer 95(5), 1045–1050.
Baggiolini, M., Walz, A., & Kunkel, S. L. (1989). Neutrophil-activating
peptide-1/interleukin 8, a novel cytokine that activates neutrophils. J Clin
Invest 84, 1045–1049.
Baggiolini, M., Deward, B., & Moser, B. (1994). Interleukin-8 and related
chemotactic cytokines—CVC and CC chemokines. Adv Immunol 55,
97–179.
Baker, P. K., Pettitt, A. R., Slupsky, J. R., Chen, H. J., Glenn, M. A., Zuzel,
M., & Cawley, J. C. (2002). Response of hairy cells to IFN-alpha
involves induction of apoptosis through autocrine TNF-alpha and pro-
tection by adhesion. Blood 100(2), 647–653.
Bingle, L., Brown, N. J., & Lewis, C. E. (2002). The role of tumour-
associated macrophages in tumour progression: implications for new
anticancer therapies. J Pathol 196(3), 254–265.
Bodey, B. (2002). Cancer-testis antigens: promising targets for antigen
directed antineoplastic immunotherapy. Expert Opin Biol Ther 2(6),
577–584.
Brennan, F. M., Maini, R. N., & Feldmann, M. (1992). TNF-alpha—a
pivotal role in rheumatoid arthritis? Br J Rheumatol 31, 293–298.
Bukowski, R., Ernstoff, M. S., Gore, M. E., Nemunaitis, J. J., Amato, R.,
Gupta, S. K., & Tendler, C. L. (2002). Pegylated interferon alfa-2b
treatment for patients with solid tumours: a phase I/II study. J Clin
Oncol 20(18), 3841–3849.
Burnet, F. M. (1970). The concept of immunological surveillance. Prog Exp
Tumor Res 13, 1–4.
Cannon, M. J., O’Brien, T. J., Underwood, L. J., Crew, M. D., Bondurant,
K. L., & Santin, A. D. (2002). Novel target antigens for dendritic cell-
based immunotherapy against ovarian cancer. Expert Rev Anticancer
Ther 2(1), 97–105.
Chen, H. W., Huang, H. I., Lee, Y. P., Chen, L. L., Liu, H. K., Cheng,
M. L., Tsai, J. P., Tao, M. H., & Ting, C. C. (2002). Linkage of
CD40L to a self-tumor antigen enhances the antitumor immune
responses of dendritic cell-based treatment. Cancer Immunol Immun-
other 51(6), 341–348.
Clark, E. A., & Ledbetter, J. A. (1994). How B and T cells talk to each
other. Nature 367, 425–428.
Clement, M. V., Legros-Maida, S., Israel-Biet, D., Carnot, F., Soulie, A.,
Reynaud, P., Guillet, J., Gandjbakch, I., & Sasportes, M. (1994). Per-
forin and granzyme B expression is associated with severe acute rejec-
tion. Evidence for in situ localization in alveolar lymphocytes of lung-
transplanted patients. Transplantation 57, 322–326.
Cohen, G. M. (1997). Caspases: the executioners of apoptosis. Biochem J
326, 1–16.
Coleman, R. M., Lombard, M. F., & Sicard, R. E. (1992). Tumour immu-
nology. Fundamental Immunology (2nd ed.) (pp. 460–483). W.M.C.
Brown.
Coley, W. B. (1991). The treatment of malignant tumours by repeated
inoculations of erysipelas. With a report of ten original cases, 1893.
Clin Orthop 262, 3–11.
Conry, R. M., Khazaeli, M. B., Saleh, M. N., Allen, K. O., Barlow, D. L.,
Moore, S. E., Craig, D., Arani, R. B., Schlom, J., & LoBuglio, A. F.
(1999). Phase I trial of a recombinant vaccinia virus encoding carci-
noembryonic antigen in metastatic adenocarcinomas: comparison of
intradermal versus subcutaneous administration. Clin Cancer Res 5,
2330–2337.
Dallman, M. J. (1995). Cytokines and transplantation: Th1/ Th2 regulation
of the immune response to solid organ transplants in the adult. Curr
Opin Immunol 7, 632–638.
Dermime, S., Armstrong, A., Hawkins, R. E., & Stern, P. L. (2002). Cancer
vaccines and immunotherapy. Br Med Bull 62, 149–162.
Dey, B. R., Sukhatme, V. P., Roberts, A. B., Sporn, M. B., Rauscher, F. J.,
& Kim, S. J. (1994). Repression of the transforming growth factor beta
1 gene by the Wilms’ tumour suppressor WT1 gene product. Mol En-
docrinol 8, 595–602.
Dinarello, C. A. (1994). The biological properties of interleukin-1. Eur
Cytokine Netw 5, 517–531.
Dinarello, C. A., Cannon, J. G., Mier, J. W., Bernheim, H. A., LoPreste, G.,
Lynn, D. I., Love, R. N., Weblo, A. C., Auron, P. E., Reuben, R. C.,
Rich, A., Wolff, S. M., & Putney, S. C. (1986). Multiple biological
activities of human recombinant interleukin-1. J Clin Invest 77,
1734–1739.
Dorval, T., Palangie, T., Jouve, M., Garcia-Giralt, E., Falcoff, E., Schwab,
D., Lerminier, M., & Pouillart, P. (1987). Treatment of metastatic
melanoma with recombinant interferon alfa-2b. Invest New Drugs 5,
S61–S63.
Dranoff, G. (2002). GM-CSF-based cancer vaccines. Immunol Rev 188(1),
147–154.
Earnshaw, W. C., Martins, L. M., & Kaufman, S. H. (1999). Mammalian
caspase: structure, activation, substrates, and functions during apopto-
sis. Annu Rev Biochem 68, 383–424.
Espinoza-Delgado, I. (2002). Cancer vaccines. Oncologist 7(2), 20–33.
Evan, G. I., & Vousden, K. H. (2001). Proliferation, cell cycle and apoptosis
in cancer. Nature 411, 4342–4348.
Fabian, Z., Torocsik, B., Kiss, K., Csatary, L. K., Bodey, B., Tigyi, J.,
Csatary, C., & Szeberenyi, J. (2001). Induction of apoptosis by a New-
castle disease virus vaccine (MTH-68/H) in PC12 rat phaeochromocy-
toma cells. Anticancer Res 21(1A), 125–135.
Firestein, G. S. (1994). Rheumatoid arthritis: rheumatoid synovitis and
pannus. In J. A. Klippel, & P. A. Dieppe (Eds.), Rheumatology
( pp. 3.12.1–3.12.30). Mosby-Year Book Europe.
Fischer, H. G., Frosch, S., Reske, K., & Reske-Kunz, A. B. (1988). Granu-
locyte macrophage colony-stimulating factor activates macrophages de-
rived from bone marrow cultures to synthesis of MHC class II
molecules and to augmented antigen presentation function. J Immunol
141, 3883–3888.
Galea, H. R., & Cogne, M. (2002). GM-CSF and IL-12 production by
malignant plasma cells promotes cell-mediated immune responses
against monoclonal Ig determinants in a light chain myeloma model.
Clin Exp Immunol 129(2), 247–253.
Ghosh, S., & Karin, M. (2002). Missing pieces in the NF-kappaB puzzle.
Cell 109(81–96), 581.
Gough, M. J., Melcher, A. A., Ahmed, A., Crittenden, M. R., Riddle, D. S.,
Linardakis, E., Ruchatz, A. N., Emiliusen, L. M., & Vile, R. G. (2001).
Macrophages orchestrate the immune response to tumor cell death.
Cancer Res 61(19), 7240–7247.
Gowans, J. L., McGregor, D., Collen, D. M., & Ford, C. E. (1962).
Initiation of immune response by small lymphocytes. Nature 196,
651–665.
Gri, G., Chiodoni, C., Gallo, E., Stoppacciaro, A., Liew, F. Y., & Colombo,
M. P. (2002). Antitumor effect of interleukin (IL)-12 in the absence of
endogenous IFN-gamma: a role for intrinsic tumor immunogenicity and
IL-15. Cancer Res 62(15), 4390–4397.
Griffiths, G. J., Dubrez, L., Morgan, C. P., Jones, N. A., Whitehouse, J.,
Corfe, B. M., Dive, C., & Hickman, J. A. (1999). Cell damage-induced
conformational changes of Bax is responsible for mitochondrial cyto-
chrome c release during apoptosis. J Cell Biol 144, 903–914.
Groopamn, J. E., Molina, J. M., & Seadden, D. T. (1989). Hematopoietic
growth factors. N Engl J Med 321, 1449–1459.
Grossman, Z., & Herberman, R. B. (1986). Immune surveillance without
immunogenecity. Immunol Today 7, 128–131.
Gupta, S., & Kanodia, A. K. (2002). Biological response modifiers in
cancer therapy. Natl Med J India 15(4), 202–207.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132 131
Hamilton, T. A., & Adams, D. O. (1987). Molecular mechanisms of signal
transduction in macrophage activation. Immunol Today 8, 151–158.
Hanna, Jr. M. G., Hoover, Jr. H. C., Vermorken, J. B., Harris, J. E., &
Pinedo, H. M. (2001). Adjuvant active specific immunotherapy of stage
II and stage III colon cancer with an autologous tumour cell vaccine:
first randomized phase III trials show promise. Vaccine 19, 2576–2582.
Heidenreich, S., Gong, J. H., Schmidt, A., Nain, M., & Gemsa, D. (1989).
Macrophage activation by granulocyte/macrophage colony stimulating
factor. Priming for enhanced release of tumour necrosis factor-alpha and
prostaglandin E2. J Immunol 143, 1198–1205.
Hsueh, E. C., Famatiga, E., Gupta, R. K., Qi, K., & Morton, D. L. (1998).
Enhancement of complement-dependent cytotoxicity by polyvalent
melanoma cell vaccine (CancerVax): correlation with survival. Ann
Surg Oncol 5, 595–602.
Hwang, C., & Sanda, M. G. (1999). Prospects and limitations of recombi-
nant poxviruses for prostate cancer immunotherapy. Curr Opin Mol
Ther 1(4), 471–479.
Iwai, Y., Ishida, M., Tanaka, Y., Okazaki, T., Honjo, T., & Minato, N.
(2002). Involvement of PD-L1 on tumor cells in the escape from host
immune system and tumor immunotherapy by PD-L1 blockade. Proc
Natl Acad Sci USA 99(19), 12293–12297.
Jaffee, E. M., Hruban, R. H., Biedrzycki, B., Laheru, D., Schepers, K.,
Sauter, P. R., Goemann, M., Coleman, J., Grochow, L., Donehower,
R. C., Lillemoe, K. D., O’Reilly, S., Abrams, R. A., Pardoll, D. M.,
Cameron, J. L., & Yeo, C. J. (2001). Novel allogeneic granulocyte-
macrophage colony-stimulating factor-secreting tumour vaccine for
pancreatic cancer: a phase I trial of safety and immune activation.
J Clin Oncol 19, 145–156.
Jager, D., Jager, E., & Knuth, A. (2001a). Immune responses to tumour
antigens: implications for antigen specific immunotherapy of cancer.
J Clin Pathol 54(9), 675–676.
Jager, D., Jager, E., & Knuth, A. (2001b). Vaccination for malignant mel-
anoma: recent developments. Oncology 60(1), 1–7.
Kirkwood, J. M., Strawderman, M. H., Ernstoff, M. S., Smith, T. J., Bor-
den, E. C., & Blum, R. H. (1996). Interferon alfa-2b adjuvant therapy of
high-risk resected cutaneous melanoma: the Eastern Cooperative On-
cology Group Trial EST 1684. J Clin Oncol 14, 7–17.
Kirkwood, J. M., Ibrahim, J. G., Sondak, V. K., Richards, J., Flaherty,
L. E., Ernstoff, M. S., Smith, T. J., Rao, U., Steele, M., & Blum,
R. H. (2000). High and low-dose interferon alfa-2b in high-risk
melanoma: first analysis of inter-group trial E1690/S9111/C9190. J
Clin Oncol 18, 2444–2458.
Kirkwood, J. M., Ibrahim, J. G., Sosman, J. A., Sondak, V. K., Agarwala,
S. S., Ernstoff, M. S., & Rao, U. (2001). High-dose interferon alfa-2b
significantly prolongs relapse-free and overall survival compared with
GM2-KLH/QS-21 vaccine in patients with resected stage IIB-III mel-
anoma: results of an inter-group trial E1694/S9512/C509801. J Clin
Oncol 19, 2370–2380.
Kobayashi, H., Wood, M., Song, Y., Appella, E., & Celis, E. (2000). Defin-
ing promiscuous MHC class II helper T cell epitopes for the HER-2/neu
tumour antigen. Cancer Res 60, 5228–5236.
Krensky, A. M., Weiss, A., Crabtree, G., Davis, M. M., & Parham, P.
(1990). T lymphocyte-antigen interactions in transplant rejection.
N Engl J Med 322, 510–517.
Kulcsar, G. (1997a). Apoptosis of tumor cells induced by substances of the
circulatory system. Cancer Biother Radiopharm 12(1), 19–26.
Kulcsar, G. (1997b). Theoretical and literary evidence for the existence of the
passive antitumor defence system. Cancer Biother Radiopharm 12(4),
281–286.
Kusumoto, M., Umeda, S., Ikubo, A., Aoki, Y., Tawfik, O., Oben, R.,
Williamson, S., Jewell, W., & Suzuki, T. (2001). Phase 1 clinical trial
of irradiated autologous melanoma cells adenovirally transduced with
human GM-CSF. Cancer Immunol Immunother 50, 373–381.
Lauerova, L., Dusek, L., Simickova, M., Kocak, I., Vagundova, M., Zalou-
dik, J., & Kovarik, J. (2002). Malignant melanoma associates with Th1/
Th2 imbalance that coincides with disease progression and immuno-
therapy response. Neoplasma 49(3), 159–166.
Lee, P., Wang, F., Kuniyoshi, J., Rubio, V., Stuges, T., Groshen, S., Gee, C.,
Lau, R., Jeffery, G., Margolin, K., Marty, V., & Weber, J. (2001). Effects
of interleukin-12 on the immune response to a multipeptide vaccine for
resected metastatic melanoma. J Clin Oncol 19, 3836–3847.
Levine, A. J. (1997). P53, the cellular gatekeeper for growth and division.
Cell 88, 323–331.
Lewis, C. E., & McGee, J. O. D. (1992). The Natural Immune System: The
Macrophage. Oxford, UK: IRS.
Li, C., & Thompson, C. B. (2002). Cancer. DNA damage, deamidation, and
death. Science 298(5597), 1346–1347.
Li, Q., & Verma, I. M. (2002). NF-kappaB regulation in the immune
system. Nat Rev Immunol 2(10), 725–734.
Liu, Y., Zhang, W., Chan, T., Saxena, A., & Xiang, J. (2002). Engineered
fusion hybrid vaccine of IL-4 gene-modified myeloma and relative
mature dendritic cells enhances antitumor immunity. Leuk Res 26(8),
757–763.
Lorenzo, J. A. (1991). The role of cytokines in the regulation of local bone
resorption. Crit Rev Immunol 11, 195–213.
Malumbres, M., & Barbacid, M. (2001). Milestones in cell division: to cycle
or not to cycle: a critical decision in cancer. Nat Rev Cancer 1, 222–231.
Marshall, J. L., Hoyer, R. J., Toomey, M. A., Faraguna, K., Chang, P.,
Richmond, E., Pedicano, J. E., Gehan, E., Peck, R. A., Arlen, P., Tsang,
K. Y., & Schlom, J. (2000). Phase I study in advanced cancer patients of
a diversified prime-and-boost vaccination protocol using recombinant
vaccinia virus and recombinant nonreplicating avipox virus to elicit
anti-carcinoembryonic antigen immune responses. J Clin Oncol 18,
3964–3973.
Mason, D. W. (1987). Subpopulations of T lymphocytes. Immunol Lett 14,
269–270.
Mason, D. W. (1988). The role of T cell subpopulations in allograft rejec-
tion. Transplant Proc 20, 239–242.
Mason, D. W., & Morris, P. J. (1986). Effector mechanisms in allograft
rejection. Annu Rev Immunol 4, 119–145.
Medawar, P. B. (1944). The behaviour and fate of skin allografts and skin
homografts in rabbits. J Anat 79, 158–176.
Miceli, M. C., & Parnes, J. R. (1991). The roles of CD4 and CD8 in T cell
activation. Semin Immunol 3(3), 133–141.
Mincheff, M., Tchakarov, S., Zoubak, S., Loukinov, D., Botev, C., Altan-
kova, I., Georgiev, G., Petrov, S., & Meryman, H. T. (2000). Naked
DNA and adenoviral immunizations for immunotherapy of prostate
cancer: a phase I/II clinical trial. Eur Urol 38, 208–217.
Modak, S., Gerald, W., & Cheung, N. K. (2002). Disialoganglioside GD2
and a novel tumor antigen: potential targets for immunotherapy of
desmoplastic small round cell tumor. Med Pediatr Oncol 39(6),
547–551.
Morse, M. A., Deng, Y., Coleman, D., Hull, S., Kitrell-Fisher, E., Nair, S.,
Schlom, J., Ryback, M. E., & Lyerly, H. K. (1999). A phase I study of
active immunotherapy with carcinoembryonic antigen peptide (CAP-1)-
pulsed, autologous human cultured dendritic cells in patients with meta-
static malignancies expressing carcinoembryonic antigen. Clin Cancer
Res 5, 1331–1338.
Naglieri, E., Lopez, M., Lelli, G., Morelli, F., Amodio, A., Di Tonno, P.,
Gebbia, N., Di Seri, M., Chetri, M. C., Rizzo, P., Abbate, I., Casamas-
sima, A., Selvaggi, F. P., & Colucci, G. (2002). Interleukin-2, interfer-
on-alpha and medroxyprogesterone acetate in metastatic renal cell
carcinoma. Anticancer Res 22(5), 3045–3051.
Nawrocki, S., Wysocki, P. J., & Mackiewicz, A. (2001). Genetically modi-
fied tumour vaccines: an obstacle race to break host tolerance to cancer.
Expert Opin Biol Ther 1(2), 193–204.
Nicklin, M. J. H., Weith, A., & Duff, G. W. (1994). A physical map of the
region encompassing the human interleukin-1a, interleukin-1b, and in-
terleukin-1 receptor antagonist genes. Genomics 19, 382–384.
Ohm, J. E., & Carbone, D. P. (2001). VEGF as a mediator of tumor-
associated immunodeficiency. Immunol Res 23(2–3), 263–272.
Oka, Y., Tsuboi, A., Elisseeva, O. A., Udaka, K., & Sugiyama, H. (2002).
WT1 as a novel target antigen for cancer immunotherapy. Curr Cancer
Drug Targets 2(1), 45–54.
J.K. Adam et al. / Pharmacology & Therapeutics 99 (2003) 113–132132
Old, L. J. (1996). Immunotherapy for cancer. Sci Am 275, 136–143.
Pahl, H. L. (1999). Activators and target genes of Rel/NF-kappaB tran-
scription factors. Oncogene 18(49), 6853–6866.
Paulnock, D. M. (1992). Macrophage activation by T cells. Curr Opin
Immunol 4, 344–349.
Peipp, M., & Valerius, T. (2002). Bispecific antibodies targeting cancer
cells. Biochem Soc Trans 30(4), 507–511.
Plunkett, T. A., & Miles, D. W. (2002). New biological therapies for breast
cancer. Int J Clin Pract 56(4), 261–266.
Quesada, J. R., Hersh, E. M., Manning, J., Reuben, J., Keating, M., Schnip-
per, E., Itri, L., & Gutterman, J. U. (1986). Treatment of hairy cell
leukemia with recombinant alfa-interferon. Blood 68, 493–497.
Rafiq, K., Bergtold, A., & Clynes, R. (2002). Immune complex-mediated
antigen presentation induces tumor immunity. J Clin Invest 110(1),
71–79.
Ravaud, A., Delva, R., Gomez, F., Chevreau, C., Douillard, J. Y., Peny, J.,
Coudert, B., & Negrier, S. (2002). Subcutaneous interleukin-2 and
interferon alpha in the treatment of patients with metastatic renal cell
carcinoma—less efficacy compared with intravenous interleukin-2 and
interferon alpha. Results of a multicenter Phase II trial from the
Groupe Francais d’Immunotherapie. Cancer 95(11), 2324–2330.
Rini, B. I., Weinberg, V., Bok, R., & Small, E. J. (2003). Prostate-specific
antigen kinetics as a measure of the biologic effect of granulocyte-
macrophage colony-stimulating factor in patients with serologic pro-
gression of prostate cancer. J Clin Oncol 21(1), 99–105.
Rossi, V., Breviario, F., Ghenzzi, P., Dejana, E., & Mantovani, A. (1985).
Prostacylin synthesis induced in vascular cells by interleukin-1. Science
229, 1174–1176.
Sato, K., Torimoto, Y., Tamura, Y., Shindo, M., Shinzaki, H., Hirai, K., &
Kohgo, Y. (2001). Immunotherapy using heat-shock protein prepara-
tions of leukemia cells after syngeneic bone marrow transplantation in
mice. Blood 98(6), 1852–1857.
Scaffidi, C., Kirchhoff, S., Krammer, P. H., & Peter, E. M. (1999). Apop-
tosis signaling in lymphocytes. Curr Opin Immunol 11, 277–285.
Schirrmacher, V., Griesbach, A., & Ahlert, T. (2001). Antitumor effects
of Newcastle disease virus in vivo: local versus systemic effects. Int
J Oncol 18(5), 945–952.
Schmitt, D. (2001). The Langerhans cell: from in vitro production to use in
cellular immunotherapy. J Soc Biol 195(1), 69–74.
Schneider, T., Gerhards, R., Kirches, E., & Firsching, R. (2001). Prelimi-
nary results of active specific immunization with modified tumour cell
vaccine in glioblastoma multiforms. J Neuro-oncol 53, 39–46.
Segal, J. G., Lee, N. C., Tsung, Y. L., Norton, J. A., & Tsung, K. (2002).
The role of IFN-gamma in rejection of established tumors by IL-12:
source of production and target. Cancer Res 62(16), 4696–4703.
Senderowicz, A. M. (2001). Cyclin-dependent kinase modulators: a novel
class of cell cycle regulators for cancer therapy. Cancer Chemother Biol
Response Modif 19, 165–188.
Sims, J. E., & Dower, S. K. (1994). Interleukin-1 receptors. Eur Cytokine
Netw 5, 539–546.
Slamon, D. J., Leyland-Jones, B., Shak, S., Fuchs, H., Paton, V., Baja-
monde, A., Fleming, T., Eiermann, W., Wolter, J., Pegram, M., Baselga,
J., & Norton, L. (2001). Use of chemotherapy plus a monoclonal anti-
body against HER-2 for metastatic breast cancer that overexpresses
HER-2. N Engl J Med 344, 783–792.
Smith, C. L., Dulphy, N., Salio, M., & Cerundolo, V. (2002). Immunother-
apy of colorectal cancer. Br Med Bull 64, 181–200.
Smyth, M. J., Hayakawa, Y., Takeda, K., & Yagita, H. (2002). New aspects
of natural-killer-cell surveillance and therapy of cancer. Nat Rev Cancer
2(11), 850–861.
Strieter, R. M., Kasahara, K., Allen, R. M., Standiford, T. J., Rolfe,
M. W., Becker, F. S., Chensue, S. W., & Kunkel, S. L. (1992).
Cytokine-induced neutrophil derived interleukin-8. Am J Pathol
141, 397–407.
Stripecke, R., Levine, A. M., Pullarkat, V., & Cardoso, A. A. (2002).
Immunotherapy with acute leukemia cells modified into antigen-pre-
senting cells: ex vivo culture and gene transfer methods. Leukemia
16(10), 1974–1983.
Termeer, C. C., Schirrmacher, V., Brocker, E. B., & Becker, J. C. (2000).
Newcastle disease virus infection induces B7-1/B7-2-independent
T-cell costimulatory activity in human melanoma cells. Cancer Gene
Ther 7(2), 316–323.
Tilney, N. L., Garovoy, M. R., & Busch, G. J. (1979). Rejected human renal
allografts: recovery and characteristics of infiltrating cells and antibody.
Transplantation 28, 421–426.
Titu, L. V., Monson, J. R., & Greenman, J. (2002). The role of CD8(+) T
cells in immune responses to colorectal cancer. Cancer Immunol Im-
munother 51(5), 235–247.
Trauth, B. C., Klas, C., Peters, A. M. J., Matzku, S., Moler, P., Falk,
W., Debatin, K. M., & Krammer, P. H. (1989). Monoclonal anti-
body-mediated tumour regression by induction of apoptosis. Science
245, 301–305.
Uekusa, Y., Gao, P., Yamaguchi, N., Tomura, M., Mukai, T., Nakajima, C.,
Iwasaki, M., Takeuchi, N., Tsujimura, T., Nakazawa, M., Fujiwara, H.,
& Hamaoka, T. (2002). A role for endogenous IL-12 in tumor immun-
ity: IL-12 is required for the acquisition of tumor-migratory capacity by
T cells and the development of T cell-accepting capacity in tumor
masses. J Leukoc Biol 72(5), 864–873.
van den Eynde, B. (2002). Identification of cancer antigens of rele-
vance for specific cancer immunotherapy. Bull Mem Acad R Med
Belg 156(10–12), 548–555.
von Mehren, M., Arlen, P., Gulley, J., Rogatko, A., Cooper, H. S., Meropol,
N. J., Alpaugh, R. K., Davey, M., McLaughlin, S., Beard, M. T., Tsang,
K. Y., Schlom, J., & Weiner, L. M. (2001). The influence of granulocyte
macrophage colony-stimulating factor and prior chemotherapy on the
immunological response to a vaccine (ALVAC-CEA B7.1) in patients
with metastatic carcinoma. Clin Cancer Res 7, 1181–1191.
Wang, R. F., Zeng, G., Johnston, S. F., Voo, K., & Ying, H. (2002). T cell-
mediated immune responses in melanoma: implications for immuno-
therapy. Crit Rev Oncol Hematol 43(1), 1–11.
Ward, S., Casey, D., Labarthe, M. C., Whelan, M., Dalgleish, A., Pandha,
H., & Todryk, S. (2002). Immunotherapeutic potential of whole tumour
cells. Cancer Immunol Immunother 51(7), 351–357.
Weiss, A., & Littman, D. R. (1994). Signal transduction by lymphocyte
antigen receptors. Cell 76, 263–274.
Wilson, D. R. (2002). Viral-mediated gene transfer for cancer treatment.
Curr Pharm Biotechnol 3(2), 151–164.
Wong, G. G., & Clark, S. C. (1988). Multiple actions of interleukin 6 within
a cytokine network. Immunol Today 9(5), 137–139.
Xu, W. D., Firestein, G. S., Taetle, R., Kaushansky, K., & Zvaifler, N. J.
(1989). Cytokines in chronic inflammatory arthritis: II. Granulocyte-
macrophage colony-stimulating factor in rheumatoid synovial effusions.
J Clin Invest 83, 876–882.
Yei, S., Bartholomew, R. M., Pezzoli, P., Gutierrez, A., Gouveia, E., Bassett,
D., Soo Hoo, W., & Carlo, D. J. (2002). Novel membrane-bound GM-
CSF vaccines for the treatment of cancer: generation and evaluation of
mbGM-CSF mouse B16F10 melanoma cell vaccine. Gene Ther 9(19),
1302–1311.
Zinzani, P. L., Lauria, F., Salvucci, M., Rondelli, D., Raspadori, D., Ben-
dandi, M., Magagnoli, M., & Tura, S. (1997). Hairy-cell leukemia and
alpha-interferon treatment: long-term responders. Haematologica 82(2),
152–155.
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