Malignant Lymphomas |
1 Hematopathology Section, Department of Pathology and Hematology, Hospital Clinic, Institut dInvestigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Spain
2 Institute of Pathology, University of Würzburg, Würzburg, Germany
3 Department of Pathology, The Netherlands Cancer Institute/Antoni von Leevenhoek Hospital, Amsterdam, The Netherlands
4 Laboratory of Molecular Cytogenetics, Department of Pathology, Hospital del Mar, Barcelona, Spain
5 Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha
6 Department of Pathology, Norwegian Radium Hospital, Olso, Norway
7 Department of Pathology, Chi-Mei Medical Center, Tainan, Taiwan
8 Section of Hematopathology and Lymphoma Clinical Research, Center for Cancer Research, Division of Cancer Treatment and Diagnosis, National Cancer Institute, National Institutes of Health, Bethesda, USA
9 Department of Pathology, Vall dHebron University Hospital, Autonomous University of Barcelona, Spain
10 Duke Institute for Genome Sciences and Policy, Duke University, Durham, North Carolina, USA
11 Department of Pathology, The University of Arizona College of Medicine, Tucson, Arizona, USA
12 Department of Pathology, Oregon Health and Science University, USA
13 Department of Pathology & Laboratory Medicine, University of British Columbia, Vancouver, Canada
14 Institut für Klinische Pathologie, Robert-Bosch-Krankenhaus, Stuttgart, Germany
Correspondence: Elias Campo, MD, PhD. Department of Pathology, Hospital Clinic, Villarroel 170, Barcelona 08036, Spain. E-mail:ecampo{at}clinic.ub.es
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Design and Methods: The microarray database of 238 mature B-cell neoplasms was re-examined. SOX11 protein expression was investigated immunohistochemically in 12 cases of cyclin D1-negative mantle cell lymphoma, 54 cases of conventional mantle cell lymphoma, and 209 additional lymphoid neoplasms.
Results: SOX11 mRNA was highly expressed in conventional and cyclin D1-negative mantle cell lymphoma and in 33% of the cases of Burkitts lymphoma but not in any other mature lymphoid neoplasm. SOX11 nuclear protein was detected in 50 cases (93%) of conventional mantle cell lymphoma and also in the 12 cyclin D1-negative cases of mantle cell lymphoma, the six cases of lymphoblastic lymphomas, in two of eight cases of Burkitts lymphoma, and in two of three T-prolymphocytic leukemias but was negative in the remaining lymphoid neoplasms. Cyclin D2 and D3 mRNA levels were significantly higher in cyclin D1-negative mantle cell lymphoma than in conventional mantle cell lymphoma but the protein expression was not discriminative. The clinico-pathological features and outcomes of the patients with cyclin D1-negative mantle cell lymphoma identified by SOX11 expression were similar to those of patients with conventional mantle cell lymphoma.
Conclusions: SOX11 mRNA and nuclear protein expression is a highly specific marker for both cyclin D1-positive and negative mantle cell lymphoma.
Key words: mantle cell lymphoma, cyclin D1, SOX11.
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The recognition of cyclin D1-negative MCL is difficult because it may resemble other small B-cell lymphomas morphologically and phenotypically. However, this distinction is clinically very relevant. Although the clinical information on cyclin D1-negative MCL is limited, published data indicate that the behavior of the variant is as aggressive as that of conventional MCL.12 On the other hand, patients with small B-cell lymphomas mimicking MCL have a significantly better outcome than those with real MCL.8 It is, therefore, important to find reliable biomarkers that may allow the identification of cyclin D1-negative MCL in clinical practice.
Cyclin D1-negative MCL seem to express high levels of cyclin D2 or D3 which, in some cases, are associated with translocations of these genes.12–14 These cyclins are also expressed at lower levels in other B-cell lymphomas. SOX11, a neural transcription factor, was found to be expressed at higher levels in leukemic MCL cells than in naïve B cells and other B-cell lymphomas.15,16 Nuclear expression of the protein has been identified in conventional MCL but not in other lymphoid neoplasms.16,17 Thus, the presence of SOX11 may be a useful identifier of cyclin D1-negative MCL. However, the spectrum of lymphoid neoplasms in previous studies was limited and no real cases of MCL negative for cyclin D1 and 11q13 rearrangements were included. The goal of our study was, therefore, to confirm the specific expression of SOX11 in MCL and define its value as a biomarker to identify cyclin D1-negative MCL.
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Table 1. SOX11 nuclear protein expression in lymphoid neoplasms.
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Immunohistochemistry
SOX11 protein expression was studied in tissue microarrays and whole tissue sections. Formalin-fixed paraffin-embedded tissue sections were stained for SOX11 (1:100; Atlas Antibodies, Stockholm, Sweden), cyclin D1 (1:100; Thermo Fisher Scientific, Runcorn, UK), cyclin D2 (1:100) and cyclin D3 (1:50) (Cell Signaling Technology, Beverly, MA, USA) in the automated platform BondMax (VisionBiosystems, Mount Waverley, Victoria, Australia). We used heat-induced retrieval with ER2 BondMax buffer solution for 15 min and detected positivity with a horseradish-peroxidase–linked polymer for 8 min (Define; Vision Biosystems) and 5'-3' diaminobenzidine for 10 min.
Quantitative polymerase chain reaction
SOX11, cyclin D1, D2, and D3 mRNA expression was investigated by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in cases not included in previous microarray expression profiling studies. Total RNA was extracted from frozen tissue samples and formalin-fixed paraffin-embedded tissue blocks using the RNeasy minikit and FFPE RNeasy minikit, respectively (Qiagen, Germantown, MA, USA). The potential residual DNA was removed using the TURBO DNA-freeTM kit from Ambion (Applied Biosystems) according to the manufacturers protocol. Complementary DNA synthesis was carried out from 1 µg of total RNA and the product was amplified and quantified using TaqMan® Universal PCR Master Mix (Applied Biosystems, Foster City, CA, USA) and TaqMan® Gene Expression Assays for SOX11 (Hs00846583_s1), CCND1 (Hs00765553_m1), CCND2 (Hs00153380_m1) and CCND3 (Hs00236949_m1) in an ABI Prism 7900HT Fast Sequence Detection System (Applied Biosystems). Relative quantification of gene expression was performed as described in the Taqman® users manual and the expression levels were analyzed with the 2–
Ct method using human β–glucoronidase (GUS) as the endogenous control and universal human reference RNA (Stratagene, Agilent Technologies, Santa Clara, CA, USA) as the mathematical calibrator.
Using quantitative PCR, we analyzed frozen tissue obtained from nine patients with MCL, five with DLBCL, two with chronic lymphocytic leukemia, one with FL, two with splenic marginal zone lymphoma (MZL), two with nodal MZL, one with MALT MZL and three with BL. Moreover, we studied ten cyclin D1-positive and five cyclin D1-negative MCL using formalin-fixed paraffin-embedded tissue.
Fluorescence in situ hybridization
Interphase fluorescence in situ hybridization (FISH) analysis was performed on formalin-fixed, paraffin-embedded tissue sections. The CCND1 rearrangement was studied using a dual color break-apart probe (DAKO, Denmark code Y5414). CCND2 and CCND3 rearrangements were studied using dual color break-apart non-commercial translocation probes. The CCND2 probe consisted of two bacterial artificial chromosome (BAC) clones directly labeled using nick translation. BAC RP11-578L13 located at the 5' end of the gene was labeled in green and BAC RP11-388F6 located at the 3' end of the gene was labeled in red.9
The CCND3 locus was investigated using the previously described probes19 consisting of one BAC clone RP11-288J23 and three plasmid artificial chromosomes (PAC): RP5-973N23, RP1-139D8 and RP1-321B9. The BAC clones were obtained from the CHORI library (www.chori.org) available in our center and the PAC clones were provided by Dr. Gesk (Institute of Human Genetics, University Hospital Kiel, Germany). At least 200 nuclei were examined. Five tonsil samples from healthy donors were used as negative controls for paraffin-embedded tissues. The cut-off value was calculated as the mean percentage of cells with a false-positive signal constellation plus three standard deviations.
Statistical analysis
The
2 test was used to evaluate the different levels of SOX11 expression. The quantitative RT-PCR results of SOX11, cyclin D1, D2 and D3 expression levels were compared using the Mann-Whitney test. p values less than 0.05 were considered statistically significant. Statistical tests were performed using SPSS v14 software (SPSS, Chicago, IL, USA).
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Figure 1. Heat map representing gene expression values for SOX11, CYCLIN D1 (CCND1), CYCLIN D2 (CCND2) AND CYCLIN D3 (CCND3). Cases of MCL, including CCND1-negative MCL are shown in the top half whereas other lymphoid neoplasms are displayed in the bottom half.
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Figure 2. Quantitative RT-PCR analysis of SOX11 mRNA expression in mantle cell lymphoma (MCL), Burkitts lymphoma (BL) and other lymphoid neoplasms (Other).
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Figure 3. SOX11 protein expression in conventional and cyclin D1-negative MCL. (A, D) Conventional and cyclin D1-negative MCL, respectively (Hematoxilin & Eosin; x400); (B, E) Cyclin D1 and (C, F) SOX11 expression in conventional and cyclin D1-negative MCL, respectively (immunohistochemistry; x200);
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Figure 4. Nuclear SOX11 staining is observed in Burkitts lymphoma and T-cell prolymphocytic lymphoma but staining is only cytoplasmic in follicular lymphoma and diffuse large B-cell lymphoma. (A,B) Burkitts lymphoma; (C,D) T-cell prolymphocytic lymphoma; (E,F) follicular lymphoma; (G,H) diffuse large B-cell lymphoma.
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SOX11 expression in cyclin D1-negative mantle cell lymphoma
To determine whether SOX11 expression could be a reliable marker for cyclin D1-negative MCL we analyzed SOX11 expression in 12 cases of cyclin D1-negative MCL. Five of the six initial cases examined by microarrays showed very high levels, similar to the remaining cyclin D1-positive MCL (Figure 1).8 SOX11 mRNA expression was then investigated in five additional cases of cyclin D1-negative MCL by quantitative RT-PCR using RNA extracted from formalin-fixed paraffin embedded tissues. The five cases showed high levels (mean=4.28; SD=4.38), similar to those observed in conventional cyclin D1-positive MCL obtained from equivalent tissue (mean=12.9; SD=19.46)(p=0.39). SOX11 protein expression was examined by immunohistochemistry in the 12 cyclin D1-negative MCL, and all of them showed strong nuclear positive staining similar to that occurring in conventional cyclin D1-positive MCL (Figure 3).
Clinical and pathological characteristics of cyclin D1-negative mantle cell lymphoma
The clinical characteristics of the 12 patients with cyclin D1-negative MCL are summarized in Table 2. Nine patients were males and the median age of the 12 patients was 60 years (range, 39–70 years). B-symptoms were observed in five patients (46%). Generalized lymphadenopathy was the most common form of presentation and extranodal sites were involved in ten patients (83%), bone marrow being the most common site (67%). Serum levels of lactate dehydrogenase were elevated in four patients (36%). All patients received different chemotherapeutic treatments. Case 1 relapsed with peripheral blood, bone marrow and colorectal involvement 26 months after the initial diagnosis and case 12 relapsed with prostate involvement 12 months after the initial diagnosis. After a median follow-up for surviving patients of 38 months (range, 37–60 months), eight patients had died of progressive lymphoma and four patients were alive with disease.
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Table 2. Clinical features of 12 patients with cyclin D1-negative MCL.
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Figure 5. FISH analysis on cyclin D1-negative MCL. (A) CCND1 break-apart probe showing two fusion signals in each cell; (B) CCND2 probe showing a split signal pattern suggesting a rearrangement of the gene.
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To determine the potential use of cyclin D2 or D3 protein expression to identify cyclin D1-negative MCL we stained the 12 cyclin D1-negative MCL, 4 conventional MCL and 21 other B-cell lymphomas. Most of the tumors showed nuclear positivity for both cyclins or predominantly one of them without clear differences between the cyclin D1-positive or negative MCL and other B-cell lymphomas (Figure 6). We investigated the possible presence of CCND2 or CCND3 translocations in the six new cyclin D1-negative tumors by FISH. Only one case (case 10) showed a split signal pattern of CCND2 in 21% of the cells, suggesting a rearrangement of this gene (Figure 5).
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Figure 6. Cyclin D2 protein expression in conventional and cyclin D1-negative MCL and in various lymphoid neoplasms. (A,B) conventional MCL; (C,D) cyclin D1-negative MCL; (E,F) small lymphocytic lymphoma; (G,H) follicular lymphoma; (I,J) splenic marginal zone lymphoma.
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The aggressive clinical evolution of these lymphomas highlights the need for reliable markers to identify such malignancies and to distinguish them from other small B-cell lymphomas because a different therapeutic management is advocated. Indeed, Yatabe et al. observed a significantly better outcome in patients with small B-cell lymphomas resembling MCL than in patients with true MCL.8
The differential diagnosis between cyclin D1-negative MCL and other small B-cell lymphomas may be difficult. Morphologically the irregular nuclei characteristic of MCL may be observed in some cases of chronic lymphocytic leukemia (CLL)21 or marginal zone lymphoma (MZL).22 CD23 is expressed in CLL but also in occasional cases of MCL.23 On the other hand, CD5 and CD43 expression, a common feature of MCL and CLL may also occur in MZL.24 Finally, although CD10 or BCL-6 have not been detected in cyclin D1-negative MCL some conventional MCL may express these germinal center markers.25,26 On this background, new and reliable biomarkers are of paramount importance.
In this study, we investigated the potential value of SOX11 expression as a marker for cyclin D1-negative MCL. Two recent studies16,17 reported overexpression of this transcription factor as highly specific to MCL because it was detected in around 90% of the MCL examined but in none of the CLL or FL and only weakly in two of 30 DLBCL. To confirm these findings and expand the number of lymphoid neoplasms investigated we first reviewed the expression profile database of the cases examined in the LLMPP consortium. SOX11 was highly expressed in virtually all conventional MCL (98%) but the levels were undetectable in all FL, DLBCL, and PMBL examined. Interestingly, moderate levels of expression were observed in 33% of the BL. We further confirmed these observations by quantitative RT-PCR and immunohistochemistry in additional MCL cases and other lymphoid neoplasms. Thus, nuclear expression of the SOX11 protein was detected in 93% of all MCL examined but in none of the large series of CLL, FL, nodal and splenic MZL, DLBCL T-cell lymphomas and in only one classical Hodgkins lymphoma. In concordance with the gene expression array studies, we detected variable SOX11 expression in BL. In addition, two of the three T-PLL and all LBL were also positive. However, these tumors are not usually mistaken for MCL.
Like Ek et al.16 we observed immunohistochemical reactivity with a dot-like pattern in the cytoplasm of lymphoid cells in reactive germinal centers and in some lymphomas but notably this pattern was not observed in MCL. The significance of this pattern is not clear but most probably does not correspond to the presence of SOX11 since it was only detected in non-MCL and reactive tissues that do not have detectable SOX11 mRNA by microarray gene expression profiling or quantitative RT-PCR. Altogether, these findings confirm that high SOX11 mRNA levels and detection of the nuclear protein are reliable markers of MCL.
These results prompted us to investigate SOX11 expression in our cyclin D1-negative MCL. Interestingly, all of them showed strong SOX11 nuclear protein expression indicating that this may indeed be a useful marker to identify these tumors. Ek et al.16 included a case of apparently cyclin D1-negative MCL in their series. However, this case had a t(11;14) translocation and, therefore, the lack of detection of cyclin D1 was most probably the consequence of a technical problem. This observation suggests that SOX11 may also be a reliable marker for diagnosing conventional MCL when cyclin D1 detection fails for technical reasons.
Gene expression array studies showed that cyclin D1-negative MCL overexpressed cyclin D2 or D3, and some cases carried chromosomal translocations of these genes.9,12,13,20 We confirmed the high levels of these two cyclins in the newly studied cyclin D1-negative MCL cases and in one case we demonstrated a cyclin D2 rearrangement by FISH. Cyclin D2 and D3 were detected immunohistochemically in the cyclin D1-negative tumors but also in most non-MCL without marked differences in the intensity of the staining, probably due to the lower discriminatory power of this technique which would, therefore, be of limited value in the differential diagnosis of these tumors.
In conclusion, we have confirmed the high specificity of SOX11 mRNA and nuclear protein expression as markers of MCL. The detection of this transcription factor is a useful biomarker for identifying true cyclin D1-negative MCL. Although SOX11 can also be detected in some BL, LBL and T-PLL, the different morphological and phenotypic features of these malignancies allow easy recognition of the cases of cyclin D1-negative MCL.
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AM and CR performed research, collected, analyzed and interpreted data and drafted the manuscript, contributed equally to it; EH, DJ, DW, JD, S-SC, ESJ, CR-M, KF, AR, DC and AL-G collected and interpreted data. CB, AV, FS, SD, LR, RB, RDG and LMS performed research and interpreted data; GO, PJ and EC designed research, analyzed and interpreted data, drafted the manuscript and are co-senior authors.
The authors reported no potential conflicts of interest.
Funding: this study was supported by the Spanish Ministery of Science and Innovation SAF 2008-03630, Instituto de Salud Carlos III "Red Temática de Investigación Cooperativa de Cancer" (2006RET2039) and Acción Transversal (V-2008-ISCIII01) and the National of Health (5U01CA114778-03). AR and EMH are supported by the Interdisciplinary Center for Clinical Research (IZKF), University of Würzburg, Germany.
Received for publication April 16, 2009. Revision received May 15, 2009. Accepted for publication May 19, 2009.
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