Hodgkin and Reed-Sternberg cells harbor alterations in the major tumor suppressor pathways and...
Transcript of Hodgkin and Reed-Sternberg cells harbor alterations in the major tumor suppressor pathways and...
doi:10.1182/blood-2002-04-1128Prepublished online September 12, 2002;
and Miguel A PirisFrancisco Mazorra, Javier Menarguez, Maria J Mestre, Manuela Mollejo, Ana I Saez, Lydia Sanchez
Martinez,Alavaro, Carmen Bellas, Angel Castano, Ana Diez, Teresa Flores, Carmen Martin, Miguel A Juan F Garcia, Francisca I Camacho, Manuel Morente, Maximo Fraga, Carlos Montalban, Tomas tissue-microarraystumor suppressor pathways and cell-cycle checkpoints: analyses using Hodgkin's and Reed-Sternberg cells harbor alterations in the major
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Hodgkin’s and Reed-Sternberg cells harbor alterations in the
major tumor suppressor pathways and cell-cycle checkpoints:
analyses using tissue-microarrays
Juan F. García,1 Francisca I. Camacho,1 Manuel Morente,1 Máximo Fraga,3 Carlos
Montalbán,4 Tomás Álvaro,6 Carmen Bellas,5 Ángel Castaño,7 Ana Díez,2 Teresa
Flores,8 Carmen Martín,9 Miguel A. Martínez,10 Francisco Mazorra,11 Javier
Menárguez12, Maria J. Mestre,13 Manuela Mollejo,14 Ana I. Sáez,1 Lydia Sánchez,2 and
Miguel A. Piris,1 for the Spanish Hodgkin’s Lymphoma Study Group.
From the Lymphoma Group, Molecular Pathology Program,(1) and
Immunohistochemistry and Histology Unit,(2) Centro Nacional de Investigaciones
Oncológicas, Madrid. Dpto. Anatomía Patológica,(3) Hospital C.U., Santiago de
Compostela. Dpto. Medicina Interna(4) and Anatomía Patológica,(5) H. Ramón y Cajal,
Madrid. Dptos. Anatomía Patológica, H. Verge de la Cinta, Tortosa,(6) H. Severo
Ochoa, Leganés,(7) H.C. Salamanca,(8) H.U.C. San Carlos, Madrid,(9) H.U. 12 de
Octubre, Madrid,(10) H. M. Valdecilla, Santander,(11) H. Gregorio Marañón,(12) H.
Móstoles, Madrid,(13) and H. Virgen de la Salud, Toledo.(14) SPAIN
Running title: Cell cycle and apoptosis deregulation in H/RS cells
Scientific Section Heading: Neoplasia
27 pages, including 4 tables and 4 figures.
Total word count: 5.241
Abstract word count: 250
Supplementary Information will be given in the web page
This study was supported by grants from the Comunidad Autónoma de Madrid
(08.1/0028.1/2000), and the Ministerio de Ciencia y Tecnologia (grants 1FD97-0431
and SAF2001-0060), Spain.
Address for correspondence and reprint requests: Juan F García, Molecular Pathology
Program. Centro Nacional de Investigaciones Oncológicas. C/ Melchor Fernández
Almagro 3, E-28029 Madrid, Spain. Phone: +34 91 224 69 00. Fax: +34 91 224 69 23.
E-mail: [email protected]
Copyright (c) 2002 American Society of Hematology
Blood First Edition Paper, prepublished online September 12, 2002; DOI 10.1182/blood-2002-04-1128 For personal use only. by guest on May 30, 2013. bloodjournal.hematologylibrary.orgFrom
Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 2
Hodgkin’s and Reed-Sternberg cells harbor alterations in the
major tumor suppressor pathways and cell-cycle checkpoints:
analyses using tissue-microarrays
ABSTRACT
Tumoral cells in Hodgkin’s Lymphoma (HL) display an increased growth fraction and
diminished apoptosis, implying a profound disturbance of the cell cycle and apoptosis
regulation. However, limitations of molecular techniques have prevented the analysis of
the tumor suppressor pathways and cell-cycle checkpoints. Tissue Microarray (TMA) is
a powerful tool for analyzing a large number of molecular variables in large series of
tumors, although the feasibility of this technique has not yet been demonstrated in
heterogeneous tumors.
The expression of 29 genes regulating the cell cycle and apoptosis were analyzed by
immunohistochemistry and ISH in 288 HL biopsies using TMA. The sensitivity of the
technique was validated by comparing the results with those obtained in standard
tissue sections.
The results revealed multiple alterations in different pathways and checkpoints,
including G1/S, G2/M transition and apoptosis. Striking findings were the
overexpression of Cyclin E, CDK2, CDK6, STAT3, Hdm2, Bcl2, Bcl-XL, Survivin, and
NF-kappaB proteins.
A multiparametric analysis identified proteins associated with increased growth fraction
(Hdm2, p53, p21, Rb, Cyclins A, B1, D3, E, CDK2, CDK6, SKP2, Bcl-XL, Survivin,
STAT1, and STAT3), and proteins associated with apoptosis (NF-kappaB, STAT1, and
RB). The analysis also demonstrated that EBV+ cases displayed a characteristic
profile, confirming the pathogenic role of EBV in HL.
Survival probability depends on multiple biological factors, including overexpression of
Bcl2, p53, Bax, Bcl-XL, MIB1 and apoptotic index.
In conclusion, H/RS cells harbor concurrent and overlapping alterations in the major
tumor suppressor pathways and cell-cycle checkpoints. This appears to determine the
viability of the tumoral cells and the clinical outcome.
Scientific Section Heading: Neoplasia
Corresponding author’s e-mail address: [email protected]
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 3
INTRODUCTION
Hodgkin’s Lymphoma (HL) is a distinct primary solid malignancy of the immune system
in which the exuberant production of cytokines and chemokines is associated with an
abundance of a component of inflammatory cells that outnumber the recognized
tumoral subpopulation of Hodgkin’s and Reed-Sternberg (H/RS) cells. These H/RS
cells harbor clonally rearranged and somatically mutated immunoglobulin genes,
indicating that, in most cases, they are derived from germinal center B cells.1
Despite the progress made in the understanding of the biology of HL, the transforming
events in these cells remain to be elucidated. In normal lymphoid tissues, germinal
center B cells lacking expression of functional high affinity Ab inevitably suffer
apoptosis under normal physiological conditions,2 while H/RS cells escape
programmed cell death, and instead proliferate and disseminate clonally by unknown
means.
The analysis of cell cycle regulation in different types of lymphoid and epithelial
neoplasms reveals a relationship whereby increased clinical aggressiveness is
associated with the accumulation of genetic and epigenetic alterations,3 which lead to
the dismantling and inactivation of the main tumor suppressor pathways: p14ARF-p53-
p21WAF1, p16INK4A-Rb and p27KIP1. Thus, although some low-grade lymphomas exhibit
alterations that are limited to apoptosis control, large cell and Burkitt lymphomas tend
to display concurrent and concerted inactivation of these tumor suppressor pathways,3,4
which finally turns them into neoplasms with an extremely high growth fraction and
resistance to standard chemotherapy.
The alterations in the main pathways responsible for controlling the cell cycle in HL
have only rarely been studied and are poorly understood, mainly because the
techniques used for molecular analyses in this disease have been limited by the
scarcity of tumoral cells. Previous studies have shown some relationships between the
expression of cell cycle proteins and patient outcome.5 The incidence of p53 mutations
has been investigated in H/RS cells and is known to be significantly lower than in other
neoplasias.6 Nonetheless proteins regulating the function of p53, such as p14ARF and
Hdm2 are expressed aberrantly and may have an indirect role in regulating the function
of p53.7 On the other hand, the Rb pathway is disrupted by p16INK4a methylation in
some cases.8 The NF-kappaB (p65/RelA) pathway is constitutively activated in different
HL-derived cell lines and tumors,9,10 partially explaining the resistance of H/RS cells to
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 4
apoptosis. The NF-kappaB activation can be related to IkappaBalpha gene mutations
in EBV-negative HL cases,11 but not in EBV-positive cases, indicating a characteristic
regulation of these cases. Other studies have shown disorder in the S-phase,12,13
frequent aneuploidy 14,15 of the tumoral cells, and suggested the presence of structural
anomalies during mitosis that lead to the formation of the characteristic multinucleated
cells.16
The high proliferative index 17,18 and resistance to apoptosis in germinal-center-derived
cells,19,20 such as H/RS cells, that produce no functional immunoglobulin, suggest that
the control of the cell cycle in these cells is seriously disrupted, and highlights the
interest in additional studies that might clarify this issue.
The recently developed Tissue Microarray (TMA) technology allows simultaneous
analyses of hundreds of tissue specimens for numerous molecular targets 21,22 by using
the techniques of immunohistochemistry (IHC), in situ hybridization (ISH) and FISH.
This technology also has the potential to significantly accelerate progress in the search
for associations between molecular changes and clinical traits.23 This tool has proved
to be remarkably useful in evaluating different cancer types, particularly those with
homogeneous histology. However, the feasibility of this technique for analyzing highly
heterogeneous tumors such as HL remains to be elucidated. Recent studies using
TMA 24 have shown the potential of this technology for restricted analyses in HL.
IHC and ISH techniques can contribute significantly to the identification of an
expression profile of cell cycle markers in H/RS cells. However, due to the paucity of
such cells, we decided to investigate whether TMA technology can also be used in this
heterogeneous tumor and in large-scale analyses. With the aim of evaluating the
alterations in the expression of essential cell cycle regulatory proteins, we performed a
series of IHC and ISH analyses of 29 different markers in 288 HL cases. This revealed
different alterations affecting the main checkpoints of the cell cycle, in G1/S and G2/M
transition, and involving all the major pathways simultaneously.
MATERIAL AND METHODS
HL samples and cell lines
288 retrospective cases of HL were collected by collaborating members of the Spanish
Hodgkin’s Lymphoma Study Group. Cases were randomly selected, diagnosed in the
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 5
period between 1994 and 1998, stages being evaluated according to standard
protocols and treated with standard polychemotherapeutic regimes (including
adriamycin in the majority of cases) with or without adjuvant radiotherapy. Paraffin
blocks were selected only on the basis of the availability of suitable formalin-fixed
paraffin-embedded tissue (at least 1 mm thick). All the samples included represent at-
diagnosis biopsies; any relapse biopsies were discarded beforehand. The histological
confirmation of HL and subtype was achieved in 277 cases by central review using
standard tissue sections, and diagnoses were made according to the criteria of the
WHO classification,25 with the help of CD30, CD15, CD20, ALK and HE staining. Cases
included 149 cases of nodular sclerosis HL, 99 cases of mixed cellularity HL, 12 cases
of lymphocyte-rich classical HL, 7 cases of lymphocyte depletion HL, 9 cases of
nodular lymphocyte-predominant HL (NLPHL), and 1 case of unclassifiable HL.
Paraffin-embedded blocks from reactive lymphoid tissue and different B- and T-cell
lymphoma samples were obtained from the tissue archives of the CNIO Tumor Bank.
Five HL-derived cell lines (L428, HDLM2, L540, KMH2, and HD-MY-Z) were obtained
from the German Collection of Microorganisms and Cell Cultures (DSMZ,
Braunschweigh, Germany).
Tissue-Microarray design
We used a Tissue Arrayer device (Beecher Instrument, MD) to construct the TMAs. All
HL cases were histologically reviewed and the richest areas of H/RS cells were marked
in the paraffin blocks. Two selected 1-mm-diameter cylinders from two different areas
were included in each case, along with 43 different controls to ensure the quality,
reproducibility and homogenous staining of the slides. Thus, four different TMA blocks
were constructed, each containing 187 cylinders.
Internal controls were provided by cell lines, normal lymphoid tissue, and different B-
and T-cell lymphomas. Five EBV-negative HL-derived cell lines, with known cell cycle
alterations were used: L428, HDLM2, L540, KMH2, and HD-MY-Z. These cell lines
were grown following standard protocols, fixed in formalin and included in paraffin as
previously described.26 Included in each TMA were a representation of reactive
lymphoid tissue (10 samples, including tonsil, spleen, and lymphadenitis), and the most
frequent non-Hodgkin’s lymphomas, of which there were 28 samples: duplicated
cylinders from B-CLL (2 cases), FCL (2 cases), MCL (2 cases), DLBCL (2 cases), BL
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 6
(2 cases, EBV-positive and -negative), PTCL (2 cases, EBV-positive and -negative),
and ALCL (2 cases).
Immunohistochemistry
TMA blocks were sectioned at a thickness of 3 µm, dried for 16h at 56ºC before being
dewaxed in xylene and rehydrated through a graded ethanol series, and washed with
phosphate-buffered saline. Antigen retrieval was achieved by heat treatment in a
pressure-cooker for 2 min in 10mM citrate buffer (pH 6.5). Before staining the sections,
endogenous peroxidase was blocked.
Immunohistochemical staining was performed on these sections using 27 different
antibodies (Abs), described in table 1. After incubation, immunodetection was
performed with the LSAB Visualization System (DAKO, Glostrup, Denmark) employing
diaminobenzidine chromogen as substrate. Sections were counterstained with
hematoxylin.
The staining of the TMA sections was evaluated by two different pathologists (JFG,
FC), using uniform criteria. In order to guarantee the reproducibility of this method, we
decided to employ straightforward and clear-cut criteria. Briefly, the pattern of staining
for each Ab was recorded as positive or negative, and high or low expression, taking
into account the expression in H/RS cells and different cut-offs for each marker (table
1).
Some exceptions to these rules were: 1) Cytoplasmic STAT1, STAT3, and NFkappaB
expression can generally be found in normal lymphoid cells and in H/RS cells. In this
study, we considered positive cases only when nuclear expression in the tumoral cells
could be seen without difficulty, indicating the activated form of these proteins.9 2) p53
nuclear overexpression is a well-known phenomenon in HL, so we considered cases
with high expression when more than 80% of tumoral cells were strongly positive. 3)
Bcl2 and other antiapoptoic regulators (Bcl-XL, Survivin) overexpression was
considered only when more than 50% of H/RS cells strongly expressed the protein.
Cases with only faint cytoplasmic expression in some tumoral cells were classified as
negative. 4) Cyclin D1 expression is considered abnormal in lymphoid cells, being
positive only in tumoral cells from MCL, MM, and some PLL. Therefore, those HL
cases displaying any kind of expression in H/RS cells were considered to be positive.
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Although the reactivity of most of the antibodies here used have been validated in
different previous studies, we cannot fully exclude that undescribed reactivities of the
antibodies or the technique here used may affect some of the results.
In situ detection of apoptosis and EBER in situ hybridization
Apoptosis was detected using the ApopTag Peroxidase In Situ Apoptosis Detection Kit
(Intergen Co., Oxford, UK), based on the TdT-mediated biotin-dUTP nicked-end
labeling (TUNEL) methodology. Briefly, TMA sections were pre-treated with proteinase
K for 15 min, and then incubated with TdT enzyme for 1 hour at 37ºC and afterwards
with anti-digoxigenin peroxidase conjugate for 1 hour. Color was developed with 3, 3’
diaminobenzidine tetrahydrochloride (10 min) and counterstained with hematoxylin.
EBV was detected by in situ hybridization with Fluorescein-Conjugated Epstein-Barr
Virus (EBER) PNA probe (DAKO). This probe is complementary to the two nuclear
EBER RNAs encoded by the Epstein-Barr virus. TMA sections were pre-treated with
proteinase K for 10 min at 37ºC, and then incubated with EBER PNA probe 1.5 hours
at 55ºC in humid chamber and afterwards washed with Stringent Wash Solution, 25
min at 55ºC in a water bath with shaking. Detection was performed with anti-FITC
antibody (clone DAK-FITC4, from DAKO) diluted at 1:100. After incubation,
immunodetection was performed with biotinylated anti-mouse immunoglobulins,
followed by peroxidase-labeled streptavidin (LSAB Visualization System, DAKO) with
diaminobenzidine chromogen as substrate. Sections were counterstained with
hematoxylin.
Validation of the technique
The reproducibility of the results thus obtained was confirmed by comparing them with
those from whole sections in 42 randomly selected cases, stained using the same
procedures for some of the Abs and probes used in this study, and for other markers
routinely in use in HL that have variable and well-known expression in H/RS cells.
Specifically, we evaluated the expression of CD20, CD30, CD15, LMP, Bcl2, Bcl6, p53,
PTEN, p16, and EBER-ISH.
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 8
Table 1. Abs used in the analyses, indicating source, dilution, threshold and pattern of reactivity used, and positive controls.
Protein Clone Source Dilution Reactivity Threshold Internal control
Ki67 MIB1 DAKO 1:100 High / low > 50% positive H/RS cells Proliferating cells
Bcl2 124 DAKO 1:25 High / low > 50% positive H/RS cells with strong expression Small lymphocytes
Bax POLYCLONAL Santa Cruz 1:1000 positive/negative > 10% positive H/RS cells Benign B-lymphocytes
Bcl-XL 2H12 ZYMED 1:10 High / low > 50% positive H/RS cells with strong expression HL-derived cell lines
Mcl1 POLYCLONAL DAKO 1:100 High / low > 50% positive H/RS cells with strong expression Proliferating cells
Survivin POLYCLONAL RD Systems 1:1500 High / low > 50% positive H/RS cells with strong expression HL-derived cell lines
p65/RelA F-6 (p65) Santa Cruz 1:2000 positive/negative Nuclear expression in H/RS cells HL-derived cell lines
Cyclin A 6E6 Novocastra 1:100 positive/negative > 10% positive H/RS cells Proliferating cells (G2/M)
Cyclin B1 7A9 Novocastra 1:25 positive/negative > 10% positive H/RS cells Proliferating cells (G2/M)
Cyclin D1 DCS-6 DAKO 1:100 positive/negative Any positive H/RS cells Macrophages and endothelial cells
Cyclin D3 DCS-22 Novocastra 1:10 positive/negative > 10% positive H/RS cells Proliferating cells
Cyclin E 13A3 Novocastra 1:10 positive/negative > 10% positive H/RS cells TMA controls, proliferating cells
CDK1 1 Transduction Lab 1:1500 positive/negative > 10% positive H/RS cells TMA controls, proliferating cells
CDK2 8D4 NeoMarkers 1:500 positive/negative > 10% positive H/RS cells TMA controls, proliferating cells
CDK6 K6.83 Chemicon 1:10 positive/negative > 10% positive H/RS cells TMA controls
Bcl6 PG-B6p DAKO 1:10 positive/negative > 10% positive H/RS cells CG B-cells and B-cell lymphomas
SKP2 1G12E9 ZYMED 1:10 positive/negative > 50% positive H/RS cells Proliferating cells
STAT1 C-136 Santa Cruz 1:50 positive/negative Nuclear expression in H/RS cells Reactive lymphocytes and macrophages
STAT3 F-2 Santa Cruz 1:500 positive/negative Nuclear expression in H/RS cells Reactive lymphocytes and macrophages
PTEN 28H6 Novocastra 1:500 positive/negative Expression in H/RS cells similar to benign cells Normal cells
P53 DO-7 Novocastra 1:50 High / low > 80% positive H/RS cells Scattered GC cells
P21 EA10 Oncogene 1:50 High / low > 50% positive H/RS cells Scattered GC cells
P16 POLICLONAL Santa Cruz 1:50 High / low Expression in H/RS cells similar to benign cells Normal cells
P27 57 Transduction Lab 1:1000 High / low > 50% positive H/RS cells Resting lymphoid cells
Hdm2 IF2 (Mdm2) Oncogen 1:10 High / low > 50% positive H/RS cells TMA internal controls, macrophages, and endothelial cells
Rb G3-245 BD PharMingen 1:250 High / low > 50% positive H/RS cells Proliferating cells
EBV-LMP CS1-4 Novocastra 1:250 positive/negative Cytoplasmic and membranous expression in H/RS EBV-positive TMA controls
F
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 9
Statistical study
The Pearson chi-square test and Fisher’s exact test were used where appropriate to
establish whether there were any relationships between the different markers included
in this study. Differences were considered to be significant for values of p<0.05.
Survival analyses were performed of all the classical HL cases for which clinical
information was available (approximately 70%). Actuarial survival curves, in terms of
Overall Survival (OS) were plotted using the Kaplan and Meier method. Statistical
significance of associations between individual variables and OS was determined by
using the log-rank test. Cox’s proportional hazard univariate analysis was also
performed independently for each variable, estimating values of the relative risk (RR),
chi-square and p. All the statistical analyses were performed using the software
package SPSS.
RESULTS
With this design, 89.3% individual core biopsies were found to include identifiable H/RS
cells. As each TMA included two different core cylinders from the same patient, this
resulted in 95.3% of cases being considered as having TMA results that could be
evaluated (Figure 1). An analysis comparing both core samples from the same cases
showed a concordance of 87%.
Figure 1. TMA design: distribution of core cylinders in TMAs (left). Preservation of
morphology, antigen preservation, and representativity of these samples is shown in
one of these cylinders, corresponding to nodular sclerosis HL, stained for H/E (middle)
and CD30 (right). Original magnification 40x; CD30 inset 600x.
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 10
To validate the chosen approach, the results obtained from the staining of 10 different
Abs and probes using TMAs were compared in a series of 42 randomly selected cases
with those obtained in the analysis of whole sections. These proved to be highly
reproducible (table 2). The overall concordance was 93.8%, a figure that accords with
previously reported results for other tumoral models,27 where concordances of greater
than 90% have been recorded when comparing results from the use of TMAs with
whole sections.
Table 2. Evaluation of IHC results in whole sections by comparison with TMA
results: number of concordant cases/number of evaluable cases. Percentage
concordance is shown in brackets. All the cases correspond to classical HL samples.
Concordant results between whole
sections and TMA cores
CD20 32/39 (82.5%)
CD30 38/38 (100%)
CD15 36/39 (92.3%)
BCL2 35/39 (89.8%)
BCL6 37/41 (90.2%)
P53 39/39 (100%)
P16 30/37 (81.1%)
PTEN 35/35 (100%)
LMP 37/37 (100%)
EBER 41/41 (100%)
Overall concordance: 93.5%
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 11
Immunohistochemistry
Threshold reactivity was defined for each Ab according to the characteristics of the
staining, giving priority to the ease of reproducibility of results. Internal control was
provided in each case by the reactivity of accompanying lymphocytes and
macrophages, or the cylinders included in the TMA for control purposes. Figure 2
shows the common pattern of expression for each Ab, and a summary of the results is
shown in Table 3.
As part of the validation process, the immunohistochemical expression of LMP protein
from EBV virus was analyzed and the results compared with those of EBER ISH. A
concordance of nearly 100% was found, thus confirming the specificity of this system.
Additionally, the different control samples illustrated the expression pattern for the
proteins analyzed and provided internal controls for EBER ISH and TUNEL techniques.
As expected, proliferating cells in normal tissue samples showed expression of MIB1,
cyclins A, B1, and D3, CDK1 and 2, SKP2, and Rb, but were negative for p27, whose
expression is opposed to proliferation. Tumor suppressor genes such as PTEN and
p16 were expressed in most cells in normal tissues, whereas only scattered lymphoid
cells in the germinal centers were p53- or Hdm2-positive. The levels of Cyclin D1 and
CDK6 were undetectable in normal lymphoid cells. STAT1 and STAT3 expression was
associated with proliferating cells, markedly in EBV-infected tissues such as those with
infectious mononucleosis. Cytoplasmic p65/RelA expression could be seen in most
lymphocytes, but nuclear protein was undetectable in normal lymphoid cells. The
pattern of expression of Bcl2, Bax, Bcl-XL, Survivin, and Bcl6 in lymphoid tissue has
been described elsewhere 28,29.
In the HL-derived cell lines, overexpression and/or loss of some oncogenes, tumor
suppressor genes, STAT proteins, and p65/RelA have been previously described 7, 30, 31. Our results from the TMAs confirmed these observations and also revealed the
frequent expression of PTEN, Cyclins A, B1, E, CDK1, 2, 6, and Rb. Finally, the
analysis of the different lymphoma samples included in these TMAs demonstrated the
pattern of expression for each protein, provided internal controls for markers such as
Cyclin D1 in MCLs or Bcl2 and Bcl6 in FCLs or DLBCLs, and also delineated the
differences between low-growth fraction lymphomas (indolent lymphomas, such as
CLL, FCL, or MCL, showing low-level expression of Cyclins, p53 and CDKs and
expressing CDKIs) and high-growth fraction lymphomas (aggressive lymphomas, such
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as DLBCL, BL, ALCL, and PTCL, with high-level expression of Cyclins and CDKs,
frequent expression of p53 and loss of some CDKIs, and generally expressing Bcl6).
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 13
Figure 2. IHC and ISH patterns: Samples with positive and negative (or high vs. low
expression) for each marker are shown. All these cases are representative of classical
HL, with either nodular sclerosis or mixed cellularity. Original magnification for Cyclins,
MIB1, Rb, p53, p27, p65/RelA, Bcl6, TUNEL, and EBER 1000x; remaining panels
600x.
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 14
Table 3: IHC and ISH results, indicating number of positive cases (percentage).
The different markers are ordered by the percentage of positive cases in the series
(see also additional information).
Marker Positive cases (%)
PTEN 258/258 (100%)
Bax 259/266 (97.4%)
Cyclin A 262/271 (96.7%)
Cyclin B1 239/257 (93%)
Cyclin E 231/257 (89.9%)
Survivin 234/262 (89.3%)
STAT1 236/267 (88.4%)
CDK1 269/264 (86.7%)
SKP2 226/268 (84.3%)
CDK2 223/265 (83.8%)
P21 218/270 (80.7%)
TUNEL 169/210 (80.5%)
P65/RelA 196/257 (76.3%)
P16 189/259 (73%)
Hdm2 171/244 (70.1%)
STAT3 145/261 (55.6%)
MIB1 121/265 (45.7%)
Rb 102/262 (38.9%)
CyclinD3 103/267 (38.6%)
EBER 98/256 (38.3%)
LMP 96/252 (38.1%)
Bcl2 61/264 (23.1%)
P27 59/256 (23.0%)
CDK6 54/262 (20.6%)
Bcl-XL 50/260 (19.2%)
P53 41/265 (15.5%)
Bcl6 24/254 (9.4%)
Mcl1 18/263 (6.8%)
Cyclin D1 14/270 (5.2%)
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 15
Considering these results together, it seems that H/RS cells express Cyclins and CDKs
involved in G1/S transition (Cyclin D, Cyclin E1, CDK2, CDK6), G2/M transition (Cyclin
A, Cyclin B1, CDK1), and molecules involved in apoptosis control (p65/RelA, Bcl2, Bcl-
XL, Survivin, and Bax). At the same time they exhibit markers suggestive of dysfunction
of the major tumor suppressor pathways, such as high p53 and Hdm2 staining,
frequent loss of p27KIP1 and also p16INK4A in a number of cases, with increased
expression of SKP2.
Some of the most striking findings were the overexpression of Cyclin E, CDK2, and
CDK6, and the increased nuclear expression of p65/RelA, STAT1 and STAT3.
Thus, in 89.9% of cases, H/RS cells showed stronger Cyclin E staining than that
observed in the reactive germinal centers included for control within the TMA. Similar
findings have been observed for CDK2, the normal partner of Cyclin E, whose
overexpression could be detected in 83.8% of samples. Lower percentages of positive
cases were observed for CDK6 (21%), Cyclin D3 (39%) and Cyclin D1 (5%). A high
degree of expression of Cyclin A and Cyclin B1 was also observed in nearly all cases
(97 and 93%, respectively).
In this series, nuclear p65/RelA could also be demonstrated in 76.3% of cases, with a
clear difference from the results obtained in reactive germinal centers, where nuclear
p65/RelA was only rarely detected. Survivin expression was found in 89.3% of cases.
Nuclear STAT1 and STAT3 staining of H/RS cells was detectable in up to 88% and
56% of samples, respectively. In this case there was also a marked difference in
comparison with the rarity of either or both transcription factors in reactive lymphocytes,
with the sole exception of Infectious Mononucleosis control cases.
Cyclin D1, besides its expected presence in endothelial cells and macrophages, was
unexpectedly found in H/RS cells in 5% of samples. Nuclear PTEN was demonstrable
in all cases, in reactive and tumoral cells. Bcl6 was observed in the majority of NLPHL
(67%), and also in a small proportion (7.3%) of classical HL cases.
Classical HL vs. Lymphocyte Predominance HL
The comparison of the expression profiling of classical HL with NLPHL revealed
differences in the profile between the two types of HL. These differences were
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 16
significant even though few NLPHL cases were included. Thus, NLPHL cases were
more frequently negative for EBV (0% positive cases vs. 39.5% in classical HL,
p=0.020), p65/RelA (37.5% vs. 77.5%, p=0.020), CDK2 (37.5% vs. 85.2%, p=0.003),
p16 (37.5% vs. 74.1% in classical HL, p=0.035), and Bcl2 (0% vs. 23.9%, p=0.048);
and they were commonly positive for Bcl6 (66.7% vs. 7.3%, p=0.000). (p values are
those associated with calculated Fisher’s exact test statistics)
Relationship between different markers
The relationships between the different markers are illustrated in Figure 3. Statistical
analysis using the Pearson and Fisher’s exact tests revealed a large number of
significant associations between different characters (see also additional information).
All NPLHL cases were EBV negative. In classical HL, the presence of EBV virus was
more frequent in MC types than in other subtypes (64.6% vs. 20.2%, p=0.000). The
presence of EBV virus in this series appears to be directly associated with STAT1 and
STAT3 expression, while there is an inverse relation with Cyclin E, CDK6, p27, p53,
Hdm2, and Bcl-XL. This confirms the role that EBV plays in this disease. It is of
particular note that EBV presence is strongly associated with STAT1 and STAT3
expression.
One of the most striking associations is that established between MIB1 and apoptosis.
In addition, growth fraction, as detected by MIB1, is associated with a large set of
markers including STAT1 and STAT3, CDK1, CDK2, CDK6, SKP2, Cyclins B1, D3,
and E, Hdm2, p53, p21, Rb, Bcl-XL, and Survivin. The strongest relationships were
found for SKP2 and STAT3.
Apoptosis rate, as measured with TUNEL, was related with nuclear p65/RelA, Rb and
STAT1 expression. At the same time, both MIB1 and TUNEL were closely related.
Cyclin E appears to have a more ubiquitous relationship, being directly related with
Cyclin A and B1, MIB1, p21, p27, Rb, SKP2, STAT1, STAT3, CDK1, CDK2, CDK6 and
p65/RelA. Of particular relevance is the strong relationship between Cyclin E and
p65/RelA identified here.
NF-kappaB (p65/RelA) is also one of the most widely related markers, as shown by two
x two contingency analyses, since in this series its expression is associated with p21,
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 17
p16, p27, Rb, Cyclin E, Cyclin D3, CDK1, CDK2, SKP2, STAT1, STAT3, Survivin, and
TUNEL.
Lastly, Bcl6 expression is strongly opposed to p27 in this series. This finding is
reminiscent of what may be observed in reactive germinal centers. At the same time,
Cyclin D3 is simultaneously expressed with Bcl6.
Figure 3: Chi-square tests: Most significant results. p values of Pearson or Fisher’s
exact (italic) test are indicated. Inverse relationships between pairs of markers are
indicated with an asterisk (*)
Relationship with survival probability
The survival analyses, restricted to classical HL cases, were done in those cases for
whom a complete clinical follow-up was available. The results of survival analyses
using Kaplan-Meier and Cox regression models are shown in table 4. Shorter OS was
significantly related with high apoptotic index (TUNEL), high proliferative index (MIB1),
and overexpression of Bcl2, p53, Bcl-XL, and Bax. Trends were also observed for low
p21 and high STAT3 expression, but they were not statistically significant (see also
additional information).
0,0970,052 0,051
0,032 0,000 0,0150,002 0,000
0,083 0,0240,020 0,0510,093 0,003 0,053 0,000 0,000 0,008
0,068 0,039 0,046 0,0070,082 0,037 0,033 0,019 0,000 0,011
0,060 0,088 0,000 0,062 0,089 0,0660,003 0,001 0,001 0,006 0,022 0,087 0,002
0,001 0,001 0,006 0,004 0,001 0,009 0,014 0,0040,034 0,001 0,004 0,001 0,003 0,008 0,001 0,032 0,004 0,006 0,015 0,000
0,083 0,015 0,010 0,058 0,057 0,0120,005 0,001
0,029 0,051 0,001 0,0280,010 0,081
0,014 0,015* 0,025* 0,006*0,006 0,026 0,013 0,007 0,019 0,080 0,001 0,013 0,002 0,0610,044 0,018 0,040* 0,086
0,027 0,000 0,018 0,000 0,001 0,002 0,020 0,000 0,012 0,001 0,0590,050 0,042 0,014 0,028 0,006 0,018 0,010 0,012 0,000 0,006 0,000
0,012 0,080 0,029 0,0110,072* 0,005* 0,045* 0,016* 0,000* 0,000 0,000 0,019*
Cyclin A
Cyclin D3
Cyclin D3
Cyclin ECyclin E
CDK1CDK1
CDK2CDK2
p16p16
p21p21
p27p27
Hdm2Hdm2
p53p53
RbRbSKP2SKP2
MIB1MIB1
STAT3STAT3
BaxBax
Bcl6Bcl6
BclXLBclXL
Mcl1
SurvivinSurvivin
TUNELTUNEL
EBV
Cyclin ACyclin B1Cyclin D3Cyclin ECDK1CDK2CDK6p16p21p27
Hdm2p53Rb
SKP2MIB1
STAT1STAT3BaxBcl2Bcl6
BclXLMcl1
NF-kBSurvivinTUNEL
EBV
Cyclin A
Cyclin B1
NF-kBNF-kB
Bcl2Bcl2
STAT1STAT1
CDK6CDK6
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 18
Table 4: Biological markers related with patient’s outcome.
DISCUSSION
Experimental models and observations in viral-induced cell transformation have shown
the synergistic effect of concurrent and multiple tumor suppressor pathway inactivation.
Examples of this are provided by viral E6 and E7 HPV proteins binding p53 and Rb,32,33
and EBV-mediated B-cell transformation through p53 and Rb binding by EBNA5
protein.34-36 Observations performed in different experimental models have proved
difficult to transfer and confirm in human tumors, where the simultaneous analysis of
different suppressor pathways requires multiple genes to be explored with an array of
techniques. The availability of monoclonal Abs for paraffin-embedded tissue and the
development of TMA now make it possible to explore this matter in tissue samples from
human tumors, even in the case of HL, where the low proportion of tumoral cells
requires the use of highly sensitive techniques.
HL is exceptional among malignant neoplasms in that the tissue samples involved
consist mainly of reactive lymphocytes, plasma cells and often fibrous stroma,
containing only a limited number of the putative neoplastic cell, the H/RS cell. Thus, in
a majority of cases H/RS cells represent less than 10% of the lymph node cell
population, making in situ techniques such as IHC and ISH the most suitable methods
for analyzing protein, DNA, and RNA expression, as they allow the visualization and
identification of this expression selectively in the neoplastic cells.
Kaplan-Meier Cox’s regression model
P Chi-square RR p
Bcl2 0.0041 8.41 2.83 0.004
MIB1 0.0307 4.67 2.28 0.031
p53 0.0232 5.15 2.45 0.023
Bcl-xL 0.0121 6.28 2.47 0.012
Bax 0.0130 6.16 4.05 0.013
TUNEL 0.0296 4.72 6.78 0.030
STAT3 0.0623 - - 0.068
p21 0.0842 - - 0.061
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 19
TMA allows simultaneous analysis of several proteins in large series of patients, thus
revealing the complex interactions between diverse pathways and genes, and, in turn,
the clinical relevance of multiple biological parameters. Different groups in several
types of human tumors have previously demonstrated the suitability of this technique.
To our knowledge, a single limited study 24 has previously provided evidence of the
feasibility of this tool in HL, based solely on the expression of a single protein.
In this paper we have shown the adequacy of TMA in the analysis of heterogeneous
tumors such as HL, made a comparative study of results from analyses of whole tissue
sections, and demonstrated the suitability of this design and the chosen conditions (two
1-mm diameter cylinders per sample). Detection of EBV LMP by IHC vs. EBER by ISH
has also shown a high concordance rate, highlighting the accuracy of the technique.
Since TMA technology is a population-level research tool, and is not intended for
making clinical diagnoses of individual cases, the general picture provided by these
experiments more than compensates for the information probably lost concerning some
of the cylinders and cases.
The checkpoint regulating transition from G1 to S is frequently disrupted in cancer, and
the mechanism of this regulation is complex. Two Cyclin/CDK complexes, Cyclin
D/CDK4 or –6 and CyclinE/CDK2, phosphorylate the retinoblastoma gene product, Rb,
alter its ability to associate with other cellular proteins, such as E2F, and activate the
transcription of several genes required for S progression. The kinase activities of
CDK4/Cyclin D and CDK2/Cyclin E convert Rb to the hyperphosphorylated state with
loss of binding activity. G1 CDK activity is positively regulated by growth factors and
inhibited by a variety of physiological signals from the cell microenvironment.37
This series shows that H/RS cells display in most of cases deregulation of the genes
involved in the G1/S and G2/M checkpoints, and inactivation of the tumor suppressor
pathways defined by p14ARF-p53-p21WAF1, p16INK4A-Rb and p27KIP1. Thus, the tumoral
cells show almost constant Hdm2 overexpression, which has been found in previous
studies to be associated with the presence of alternative transcripts of Hdm2 lacking
the adhesion to p14ARF, its inhibitory protein.7 Hdm2 overexpression is considered to be
a mechanism that leads to p53 inactivation, binding it and concealing its transcriptional
activity.38 Although alterations in the p53 gene are the most common genetic alteration
found in human cancer (>50%), the incidence of p53 mutations is significantly lower in
HL than in other neoplasias.39,40 The understanding of the activity of these proteins in
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 20
HL may explain the unusual low frequency of p53 mutations in this tumor with
overexpression of the protein and defective p53 function.
The p16INK4a-Rb pathway is also presumably inactivated in a large fraction of these
samples as the result of p16INK4a loss (due to promoter region methylation or deletion)
and/or Cyclin D overexpression. Results obtained here concerning p16 loss differ
slightly from those previously reported, probably as a consequence of the higher
sensitivity of the techniques or the larger size of the series employed in the current
study.
In the majority of cases, p27KIP1 protein is also lost, probably as a consequence of
increased degradation mediated by SKP2. SKP2 protein acts as a ubiquitin ligase for
p27KIP1, and most cases show overexpression of this protein in H/RS cells. Indeed,
consistent with this interpretation, there is an inverse relationship between p27KIP1 and
SKP2 expression in HL tumors.
At the same time, the tumoral cells are characterized by the increased expression in a
large proportion of cases of Cyclins and CDKs involved in G1/S and G2/M transition,
such as Cyclin D, Cyclin A, Cyclin B1, Cyclin E, CDK2 and CDK6. A striking finding
here is the observation that 90% and 84% of cases show overexpression of Cyclin E
and CDK2, respectively, which differs strongly from the observations in reactive
lymphoid tissue and other NHLs. Cyclin E and CDK2 both form a complex, which is
negatively regulated through the interaction with p27KIP1, and whose balance
determines the cell-cycle progression to the S phase. This almost universal finding in
H/RS could be related with the increased growth fraction seen in these cells, as already
described.41 Additionally, deregulated Cyclin E increases chromosomal instability and
polyploidy,42 affecting those processes involved in the faithful duplication and
segregation of chromosomes. These are findings that could be considered to be the
hallmark of HL cells.
Consistent with altered mitotic checkpoint control, the H/RS cells also express elevated
protein levels of the mitotic regulatory proteins cyclin A, cyclin B1, and CDK1 (cdc2).
The cyclin B/CDK1 complex (also called mitosis promoting factor, MPF) is the primary
regulator of transition from G2 to M phase, being involved in chromosome
condensation, nuclear membrane breakdown, and spindle formation. The transition
from G2 to M phases and the proper transition during mitosis depend on cyclin A and B
proteosomal degradation.43 For example, onset of mitosis is regulated by the activation
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 21
of Cyclin B1/CDK1 and this event is controlled at several levels, ensuring that
chromosome segregation does not occur in the case of unreplicated or damaged DNA,
or misaligned chromosomes. The altered expression of these G2/M Cyclins and CDKs
in H/RS cells could depend on inappropriate ubiquitination/degradation, and also could,
at least partially, explain the frequent alterations in cytokinesis and the morphological
abnormalities found in these cells, leading to the formation of the characteristic
multinucleated cells.
H/RS cells also have defective regulation of apoptosis, as shown by the association of
Bcl2 (23%), Bcl-XL (19%), and Survivin (89%) overexpression, loss of Bax expression
(3%), and increased nuclear expression of p65/RelA (76%). These findings are
consistent with those of previous studies9,44,45 suggesting that Bcl2, Bcl-xL, and NF-
kappaB activation are critical mechanisms involved in the resistance to apoptosis by
H/RS cells, at least in some cases as a consequence of the transforming capacity of
LMP1-EBV protein46. The frequent expression of Survivin in the H/RS cells in HL has
not been previously described, and may represent an additional mechanism for
evading apoptosis in the G2/M checkpoint. The relevance of Bcl2 and Bcl-XL
overexpression is underlined by the shortened OS of these patients. This result is
similar to observations in DLBCL, and confirms previous observations in HL.47 In this
context it is worth mentioning that the disease in cases of HL with marked
overexpression of p53 proteins, as observed in 15% of cases, is more aggressive and
has a shortened OS. Here we have chosen this high threshold of p53 expression,
similar to that found to reflect p53 mutations in other lymphoid tumors.
H/RS cells harbor clonally rearranged and somatically mutated immunoglobulin genes,
indicating their derivation in most cases from germinal center B cells,1 but lack B-cell
receptor expression. Although germinal center B cells that lack a functional high-affinity
Ab undergo apoptosis within the germinal center, under physiological conditions,2 the
H/RS cells escape programmed cell death (apoptosis), and instead proliferate and
disseminate. The concurrent alterations in cell cycle regulatory pathways observed in
this series thus explain the insensitivity of H/RS cells to inhibitory signals, and its high
growth fraction.
The analysis of the relationships among the proteins studied yields some interesting
findings. Thus, EBV positive cases have a characteristic profile distinguished by the
overexpression of STAT1 and STAT3 by the H/RS cells, and down-regulation of the
expression of p27, Hdm2, p53, Cyclin E, CDK6, and Bcl-xL, which seems to confirm
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 22
that EBV presence in H/RS is not just an innocent bystander, but also plays a role in
the progression of the disease and the survival of tumoral cells. STAT1 and STAT3
also seem to play a determinant role, since their expression in H/RS cells is
significantly associated with the presence of increased levels of CDK1, CDK2 and
CDK6, Rb, NF-kappaB, and Bax, and also is associated with higher proliferative index.
Previous studies analyzing the expression profile in EBV positive cases at RNA level34
also revealed a specific pattern, but showing some differences from our results at the
protein level. These findings provide convincing evidence that the EBV virus exploits
the normal program of B-cell-cycle activation as part of its strategy.
Another key transcription factor revealed by this study as playing an important role in
HL is NF-kappaB, as has been observed previously in HL-derived cells48,49 and
tumors.9,10 This transcription factor regulates the expression of numerous genes
regulating critical functions in the immune system, inflammatory responses involved in
the control of cell proliferation and apoptosis. This analysis proves that the presence of
NF-kappaB and its activation, as reflected by the nuclear expression, is related to
changes in the expression of a set of proteins that play a role in the control of cell-cycle
progression, apoptosis and gene transcription, such as p21, p16, p27, Rb, Cyclin E,
Cyclin D3, CDK1, CDK2, SKP2, STAT1, STAT3, and Survivin. It is noteworthy the
strong relation observed with Survivin (p<0.000), a member of the inhibitor of apoptosis
(IAP) family, which has been described as a target of NF-kappaB 50. Although the
association with Bcl-XL (another NF-kappaB target) is not statistically significant, the
majority of cases express high levels of both proteins.
High MIB1 expression is associated here with the increased expression of Rb, p21,
p53, Hdm2, Cyclins A, B1, D3, and E, CDK1, CDK2 and CDK6, SKP2, STAT1, STAT3,
and Bcl-XL. Thus it appears that the increased growth fraction, typical of Hodgkin’s
cells, is the consequence of deregulation of multiple genes, significantly including
Cyclins and CDK, transcription factors and SKP2, a key gene in protein degradation
mediated by ubiquitin. The complexity of the changes in cell-cycle regulation in H/RS
cells is shown in Figure 4.
In spite of the small number of NLPHL cases here included, this study also reveals that
these cases have a distinctive profile (Bcl6+, EBV-, p65/RelA-, p16-, Bcl2-, and CDK2-
), different from that seen in classical HL, and not only attributable to the presence of
EBV virus.
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 23
Clinical correlation also sheds further light on the relevance of these findings. Several
of these regulator proteins seem to be associated with patient outcome. Thus, a shorter
survival in this series is related with Bcl2, p53, Bcl-XL, Bax, and high proliferative and
apoptotic indexes. Some of these prognostic markers had been previously noted in the
literature.5,45,51,52 These findings have been shown to be statistically significant using
Kaplan-Meier and Cox regression analyses and restricted to classical HL cases.
Nevertheless, a more comprehensive analysis of these and other markers is currently
being performed with the aim of incorporating biological variables into the clinical
prognosis scoring system.
In summary, TMA studies with a panel of Abs for cell cycle markers show an
unexpected constellation of abnormalities for the expression of oncogenes and cell-
cycle control molecules, thus confirming the complexity of the changes involved in the
malignant transformation in HL. Variations in the expression profiling reflect the
histological sub-typing and account for some of the clinical variability observed in this
disease.
Figure 4. Scheme of cell cycle showing main checkpoints commonly deregulated in
HL tumors (see text).
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Juan F García. Cell cycle and apoptosis deregulation in H/RS cells 24
ACKNOWLEDGMENTS
We are indebted to Laura Cereceda (CNIO Tumor Bank) and L. García (Hematology,
H. Ramón y Cajal, Madrid) for their excellent assistance with data managing, and to R.
Pajares, and M.J. Acuña for their expertise and excellent technical assistance with
TMA technology and immunohistochemical assays. We also thank all the participants
of the Spanish Hodgkin’s Lymphoma Study Group for their cooperation: P. Domínguez
and C. Jara (F.H.A, Alcorcón), R. Quibén and L. Borbolla (H. Móstoles, Madrid), C.
Grande (H. 12 Octubre, Madrid), J. García (H. Ramón y Cajal, Madrid), A. Castaño and
P. Sáncjez-Godoy (H. Servero Ochoa, Leganés), R. Martínez (H.U.C. San Carlos,
Madrid), J. Menárguez, P. Sabín (H. Gregorio Marañón, Madrid), J. González-Carrero
and C. Poderós (H. Xeral-Cies, Vigo), Ll. Font (H. Verge de la Cinta, Tortosa), M.A.
Cruz (H. Virgen de la Salud, Toledo), M. Llanos (H.U. Canarias), C. Morante (H.
Cabueñes, Gijón), E. Conde (H.M. De Valdecilla, Santander), M.F. Fresno and C.
Rayón (H.C. de Asturias, Oviedo), R. García (H.C.U. Salamanca), J. Guma (H. Sant
Joan, Reus), P. Gonzalvo (H.C.de Jarrio, Coaña), G. Fernández (H. Alvarez Buyllas,
Mieres), J. Forteza and J.L. Bello (F. Med Santiago de Compostela), and J.R. Méndez
(H. Valle de Nalón, Asturias).
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