Genomic and gene expression profiling defines indolent forms of mantle cell lymphoma

A case of hairy cell leukemia with CCND1-IGH@ translocation: indolent non-nodal mantle cell lymphoma revisited

CCND1-IGH@ translocation is considered pathognomonic of mantle cell lymphoma (MCL), as this distinct chromosomal abnormality has not been reported in any other subtypes of mature B-cell lymphoma. Despite this unifying cytogenetic feature, MCL encompasses 2 distinct groups: the usual MCLs with an overall survival of 3 to 5 years and the so-called "indolent non-nodal mantle cell lymphomas (INNMCLs)." The latter group of MCLs has quite distinctive clinical features, including frequent neoplastic lymphocytosis, absent peripheral lymphadenopathy, and indolent clinical courses. The clinical, biological, and molecular characteristics of INNMCL are still not well understood. Herein, we report a patient with clinical and cytogenetic features of INNMCL with overlapping morphologic and immunophenotypic features resembling hairy cell leukemia (HCL). After failing the chemotherapeutic regimen for MCL, he received a HCL-directed therapy and achieved durable response. This case suggests that CCND1-IGH@ may rarely occur in other mature B-cell neoplasms such as HCL. Further clinicopathologic studies of the so-called "INNMCL" are warranted.

Colonic in situ mantle cell lymphoma

This report describes the first case, to our knowledge, of in situ mantle cell lymphoma (MCL) in the gastrointestinal tract identified retrospectively by immunostains and fluorescence in situ hybridization (FISH) analysis after progression to disseminated disease with pleomorphic morphology several years later. A 45-year-old man with blood per rectum underwent colonoscopy and had random biopsies interpreted as benign colonic mucosa. Two years later, he presented with ileocolic intussusception related to enlarged lymph nodes. Biopsies on the second presentation demonstrated widespread MCL. Reevaluation of the original colonic biopsies showed cyclin D1-positive cells within small lymphoid aggregates, confirmed by FISH for t(11;14). Postchemotherapy, lymphoid aggregates in colonic biopsies showed scattered cyclin D1- and FISH t(11;14)-positive cells, similar to the original in situ lymphoma. We discuss this case in the context of the current understanding of the evolution of MCL and the difficulties associated with detecting primary GI lymphoma.

The use of microarray technologies in mantle cell lymphoma

Mantle cell lymphoma (MCL) is characterized by adverse prognosis and the development of novel therapeutic approaches is essential to improve outcome. The introduction of gene expression profiling using DNA microarrays has significantly enhanced our understanding of the molecular pathogenesis of MCL, which is a prerequisite to the development of novel treatment strategies. Gene expression profiling can furthermore be applied to predict treatment response at diagnosis and thus can be used to assess a patient's individual risk profile. This review summarizes our current knowledge on the use of microarray technology in MCL.

Epigenetic activation of SOX11 in lymphoid neoplasms by histone modifications

Recent studies have shown aberrant expression of SOX11 in various types of aggressive B-cell neoplasms. To elucidate the molecular mechanisms leading to such deregulation, we performed a comprehensive SOX11 gene expression and epigenetic study in stem cells, normal hematopoietic cells and different lymphoid neoplasms. We observed that SOX11 expression is associated with unmethylated DNA and presence of activating histone marks (H3K9/14Ac and H3K4me3) in embryonic stem cells and some aggressive B-cell neoplasms. In contrast, adult stem cells, normal hematopoietic cells and other lymphoid neoplasms do not express SOX11. Such repression was associated with silencing histone marks H3K9me2 and H3K27me3. The SOX11 promoter of non-malignant cells was consistently unmethylated whereas lymphoid neoplasms with silenced SOX11 tended to acquire DNA hypermethylation. SOX11 silencing in cell lines was reversed by the histone deacetylase inhibitor SAHA but not by the DNA methyltransferase inhibitor AZA. These data indicate that, although DNA hypermethylation of SOX11 is frequent in lymphoid neoplasms, it seems to be functionally inert, as SOX11 is already silenced in the hematopoietic system. In contrast, the pathogenic role of SOX11 is associated with its de novo expression in some aggressive lymphoid malignancies, which is mediated by a shift from inactivating to activating histone modifications.

Mantle cell lymphoma

MCL is a well-characterized clinically aggressive lymphoma with a poor prognosis. Recent research findings have slightly improved the outcome of this neoplasm. The addition of rituximab to conventional chemotherapy has increased overall response rates, but it does not improve overall survival with respect to chemotherapy alone. The use of intensive frontline therapies including rituximab and consolidated by ASCT ameliorates response rate and prolongs progression-free survival, but any impact on survival remains to be proven. Furthermore, the optimal timing, cytoreductive regimen and conditioning regimen, and the clinical implications of achieving a disease remission even at molecular level remain to be elucidated. The development of targeted therapies as the consequence of better dissection of pathogenetic pathways in MCL might improve the outcome of conventional chemotherapy in most patients and spare the toxicity of intense therapy in a minority of MCL patients characterized by a relatively indolent disease. Patients not eligible for intensive regimens, such as hyperC-VAD, may be considered for less demanding therapies, such as the combination of rituximab either with CHOP or with purine analogues, or bendamustine. Allogeneic SCT can be an effective option for relapsed disease in patients who are fit enough and have a compatible donor. Maintenance rituximab may be considered after response to immunochemotherapy for relapsed disease, although there are currently no data to recommend this approach as the first-line strategy. As the optimal approach to the management of MCL is still evolving, it is critical that these patients be enrolled in clinical trials to identify better treatment options.

Indolent mantle cell leukemia: a clinicopathological variant characterized by isolated lymphocytosis, interstitial bone marrow involvement, kappa light chain restriction, and good prognosis

BACKGROUND

Cases of mantle cell lymphoma with indolent behavior have been reported, but are poorly identified by current clinical risk models. Early studies found peripheral blood involvement to be an adverse prognostic factor; however, cases of a seemingly indolent variant of mantle cell lymphoma, characterized by peripheral blood involvement and minimal nodal disease, have been incompletely described, particularly with regard to bone marrow findings. We report a series of leukemic phase mantle cell lymphomas with a non-progressive or slowly progressive course.

DESIGN AND METHODS

Cases presenting with mantle cell lymphoma limited to the peripheral blood/bone marrow from 2000-2010 were identified. Diagnoses were established by morphology, flow cytometric analysis and requisite evidence of IGH-CCND1@ by fluorescence in-situ hybridization or t(11;14)(q13;q32) by cytogenetics. Patients with lymphadenopathy, splenomegaly and gastrointestinal symptomatology were excluded.

RESULTS

Patients (n=8, median age 60.5 years) were asymptomatic with mild lymphocytosis (8.7×10(9)/L; range, 4.5-14.2×10(9)/L) and cytology typical of mantle cell lymphoma. Flow cytometric analysis showed that all expressed CD5, CD19, CD20, variable CD23, and a striking kappa immunoglobulin light chain restriction (7/8 cases). Bone marrow biopsy at diagnosis showed interstitial single or small lymphoid aggregates with similar patterns of CD20 and cyclin D1 immunostaining which were not readily discernable by hematoxylin and eosin stain. SOX11 was negative (4/5) or only weakly expressed (1/5). The median follow-up was 27 months (range, 5-109 months) and all patients, but one, are alive with no clinical evidence of disease. The prevalence of indolent mantle cell lymphoma presenting only with lymphocytosis, among all mantle cell lymphomas diagnosed during the same period, was 3%.

CONCLUSIONS

Leukemic mantle cell lymphoma limited to blood and bone marrow is an indolent variant characterized by mild-moderate lymphocytosis, interstitial low-level bone marrow involvement, simple karyotype, kappa light chain expression, cyclin D1 expression with lack of SOX11, and slow or absent clinical progression. Some cases may represent a mantle cell lymphoma counterpart to chronic lymphocytic leukemia - phenotype monoclonal B-cell lymphocytosis. Recognition of this variant could inform treatment decisions and possibly avoid unnecessary treatment.

Pathogenesis of non-Hodgkin's lymphoma

The understanding of the molecular pathogenesis of non-Hodgkin's lymphomas (NHL) has significantly improved in recent years. Advances in molecular biology and genetics lead to the identification and characterization of several oncogenic pathways involved in lymphomagenesis. This knowledge will ultimately lead to improved diagnostic and therapeutic strategies for patients with NHL. This review summarizes current concepts of the molecular pathogenesis of the most common NHL subtypes, with a special emphasis on diffuse large B-cell lymphoma, the most common lymphoma subtype.

The expression of SOX11, cyclin D1, cyclin D2, and cyclin D3 in B-cell lymphocytic proliferative diseases

SOX11 is mainly correlated with embryo neurogenesis and remodeling of tissues. D cyclins (cyclin D1, cyclin D2, and cyclin D3) work in cell transformation. We assessed the expression of SOX11, cyclin D1, cyclin D2, and cyclin D3 mRNA in 152 patients with B-cell lymphocytic proliferative diseases (B-LPD) using qRT-PCR and we detected SOX11 protein using immunohistochemistry in 15 B-LPD patients, to clarify the clinical significance of the four genes in B-LPD. Data showed the transcriptional levels of SOX11 and cyclin D1 were higher for the mantle cell lymphoma (MCL) samples compared with chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), hairy cell leukemia (HCL), splenic marginal zone lymphoma (SMZL), and healthy collators. The expression levels of cyclin D1 and cyclin D2 were both higher in DLBCL than in SMZL. The expression levels of the four genes were highly related to each other. Three of 4 MCL patients showed nuclear staining for SOX11, while other 11 B-LPD examples were negative. Furthermore, we also found the ZAP70-positive CLL patients had higher SOX11 expression levels than ZAP70-negative CLL patients. It was revealed that MCL patients have higher expression levels of SOX11 and cyclin D1 mRNA, specially expressed nuclear SOX11 protein.

A rare case of t(11;22) in a mantle cell lymphoma like B-cell neoplasia resulting in a fusion of IGL and CCND1: case report

The chromosomal translocation (11;14)(q13;q32) rearranging the locus for cyclin D1 (CCND1) to that of the immunoglobulin heavy chain (IGH) can be found in virtually all cases of mantle cell lymphoma (MCL), while other CCND1 translocations are extremely rare. As CCND1 overexpression and activation is a hallmark of MCL it is regarded as a central biological mechanism in the development and maintenance of this disease.

Here we present a patient initially diagnosed with chronic lymphocytic leukemia (CLL) where chromosome banding analysis revealed, among other aberrations, a translocation (11;22)(q13;q11.2). We show by fluorescence in situ hybridization (FISH) analysis that on chromosome 22 the immunoglobulin light chain lambda (IGL) is involved in this cytogenetic aberration. Additionally, we demonstrate the resulting overexpression of CCND1 on the RNA and protein level, thereby consolidating the new diagnosis of a MCL-like B-cell neoplasia. Summing up, we described a rare case of t(11;22)(q13;q11.2) in a MCL-like neoplasia and showed that this aberration leads to an overexpression of CCND1 which is regarded as a key biological feature in MCL. This case underlines the importance of cytogenetic analyses especially in atypical cases of B cell lymphomas.

The 2008 WHO classification of lymphoid neoplasms and beyond: evolving concepts and practical applications

The World Health Organization classification of lymphoid neoplasms updated in 2008 represents a worldwide consensus on the diagnosis of these tumors and is based on the recognition of distinct diseases, using a multidisciplinary approach. The updated classification refined the definitions of well-recognized diseases, identified new entities and variants, and incorporated emerging concepts in the understanding of lymphoid neoplasms. However, some questions were unresolved, such as the extent to which specific genetic or molecular alterations define certain tumors, and the status of provisional entities, categories for which the World Health Organization working groups felt there was insufficient evidence to recognize as distinct diseases at this time. In addition, since its publication, new findings and ideas have been generated. This review summarizes the scientific rationale for the classification, emphasizing changes that have had an effect on practice guidelines. The authors address the criteria and significance of early or precursor lesions and the identification of certain lymphoid neoplasms largely associated with particular age groups, such as children and the elderly. The issue of borderline categories having overlapping features with large B-cell lymphomas, as well as several provisional entities, is reviewed. These new observations chart a course for future research in the field.

Should there be a standard therapy for mantle cell lymphoma?

Mantle cell lymphoma (MCL) is an uncommon subtype of B-cell lymphomathat is characterized by monoclonal B cells that express CD5 on their surface, but not CD23, and harbor the t(11:14) chromosomal translocation that leads to dysregulated expression of cyclin D1. MCL is a biologically and clinically heterogeneous disease. It has the unfavorable characteristics of both aggressive and indolent lymphoma in that MCL is not curable with current standard therapy, yet patients have a shorter survival compared with other indolent histology. MCL is incurable, yet more intensive therapy does lead to longer disease-free intervals; therefore, treatment must be designed to optimize survival while maintaining quality of life. Thus, therapy should be individualized based on both the clinical behavior of the lymphoma and the patient’s status. While there is no clear standard therapy that can be recommended for all patients, there may be an optimal choice for each patient. Knowledge of the expected clinical benefits and toxicities of various approaches will allow the physician and patient to appropriately select the therapy.

Update on the molecular pathogenesis and clinical treatment of Mantle Cell Lymphoma (MCL): minutes of the 9th European MCL Network conference

Mantle cell lymphoma (MCL) is a distinct subtype of malignant lymphoma which is characterized by the chromosomal translocation t(11;14)(q13;q32), resulting in constitutional overexpression of cyclin D1 and cell cycle dysregulation in virtually all cases. Clinically, MCL shows an aggressive clinical course with a continuous relapse pattern and a median survival of only 3-5 years. However, recently a subset of 15% long-term survivors has been identified with a rather indolent clinical course, even after conventional treatment strategies only. Advanced stage disease is usually apparent already at first clinical manifestation; thus, conventional chemotherapy is only palliative, and the median duration of remissions is only 1-2 years. Emerging strategies including proteasome inhibitors, immune modulatory drugs (IMiDs), mTOR inhibitors, and others are based on the dysregulated control of cell cycle machinery and impaired apoptotic pathways. Monotherapy of these compounds achieves efficacy comparable to conventional chemotherapy in relapsed MCL, and combination strategies are currently being investigated in numerous trials; however, their introduction into clinical practice and current treatment algorithms remain a challenge. In 2000 the European MCL Network ( http://www.european-mcl.net ) was founded, consisting of 15 national lymphoma study groups supplemented by experts in histopathology and molecular genetics. During the past decade, the European consortium has successfully initiated the largest phase III trials in MCL worldwide, with a current annual recruitment of almost 200 patients per year in first-line studies. In detail, in prospective randomized studies, the addition of a B-lymphocyte specific antibody doubled the median progression-free survival from 14 to 28 months, and a dose-intensified consolidation with high-dose radiochemotherapy and subsequent autologous stem cell transplant resulted in superior response duration (3.7 vs. 1.6 years) and even improved overall survival in a recent analysis. Future strategies will apply individualized approaches according to the molecular risk profile of the patient. At the recent annual conference in Jerusalem, recent results of molecular pathogenesis, analyses of current clinical trials, and new study concepts were discussed.

Mantle cell lymphoma: report of the 2010 Mantle Cell Lymphoma Consortium Workshop

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma typically characterized by cyclin D1 overexpression as result of the t(11;14) translocation. MCL is biologically and clinically heterogeneous and frequently involves extranodal dissemination. Although MCL is incurable with current therapies, with the exception of allogeneic stem cell transplant, recent advances are improving long-term outcomes in MCL. Intensive research has continued to focus on elucidating biological mechanisms of MCL, identifying new molecular targets, and optimizing existing therapies. Most recently, researchers have begun focusing on new areas such as epigenetics and microRNAs and their potential applications to MCL therapy. Advances across a broad spectrum of MCL research were presented at a recent MCL Workshop. This report provides an overview of the scientific highlights from the meeting and a framework for future research.

How I diagnose and treat splenic lymphomas

The incidental finding of an isolated splenomegaly during clinical assessment of patients evaluated for unrelated causes has become increasingly frequent because of the widespread use of imaging. Therefore, the challenging approach to the differential diagnosis of spleen disorders has emerged as a rather common issue of clinical practice. A true diagnostic dilemma hides in distinguishing pathologic conditions primarily involving the spleen from those in which splenomegaly presents as an epiphenomenon of hepatic or systemic diseases. Among the causes of isolated splenomegaly, lymphoid malignancies account for a relevant, yet probably underestimated, number of cases. Splenic lymphomas constitute a wide and heterogeneous array of diseases, whose clinical behavior spans from indolent to highly aggressive. Such a clinical heterogeneity is paralleled by the high degree of biologic variation in the lymphoid populations from which they originate. Nevertheless, the presenting clinical, laboratory, and pathologic features of these diseases often display significant overlaps. In this manuscript, we present our approach to the diagnosis and treatment of these rare lymphomas, whose complexity has been so far determined by the lack of prospectively validated prognostic systems, treatment strategies, and response criteria.

Gene expression profiling and chromatin immunoprecipitation identify DBN1, SETMAR and HIG2 as direct targets of SOX11 in mantle cell lymphoma

The SRY (sex determining region Y)-box 11 (SOX11) gene, located on chromosome 2p25, encodes for a transcription factor that is involved in tissue remodeling during embryogenesis and is crucial for neurogenesis. The role for SOX11 in hematopoiesis has not yet been defined. Two genes under direct control of SOX11 are the class- III β-tubulin gene (TUBB3) in neural cells and the transcription factor TEA domain family member 2 (TEAD2) in neural and mesenchymal progenitor cells. Normal, mature lymphocytes lack SOX11 but express SOX4, another member of the same group of SOX transcription factors. We and others recently identified SOX11 as aberrantly expressed in mantle cell lymphoma (MCL). Since SOX11 is variably expressed in MCL it may not be essential for tumorigenesis, but may carry prognostic information. Currently, no specific functional effects have been linked to SOX11 expression in MCL and it is not known which genes are under influence of SOX11 in lymphoma. In this study we found variable expression of SOX11, SOX4 and SOX12 mRNA in mantle cell lymphoma cell lines. Downregulation of SOX11 expression by siRNA verified that SOX11 controlled the expression of the gene TUBB3 in the MCL cell line Granta 519. Furthermore we identified, by global gene expression analysis, 26 new target genes influenced by siRNA SOX11 downmodulation. Among these genes, DBN1, SETMAR and HIG2 were found to be significantly correlated to SOX11 expression in two cohorts of primary mantle cell lymphomas. Chromatin immunoprecipitation (ChIP) analysis showed that these genes are direct targets of the SOX11 protein. In spite of almost complete downregulation of the SOX11 protein no significant effects on Granta 519 cell proliferation or survival in short term in vitro experiments was found. In summary we have identified a number of genes influenced by SOX11 expression in MCL cell lines and primary MCL. Among these genes, DBN1, SETMAR and HIG2 are direct transcriptional targets of the SOX11 protein.

Mantle cell lymphoma: biology, pathogenesis, and the molecular basis of treatment in the genomic era

Mantle cell lymphoma (MCL) is a B-cell non-Hodgkin lymphoma of which at least a subset arises from antigen-experienced B cells. However, what role antigen stimulation plays in its pathogenesis remains ill defined. The genetic hallmark is the chromosomal translocation t(11;14) resulting in aberrant expression of cyclin D1. Secondary genetic events increase the oncogenic potential of cyclin D1 and frequently inactivate DNA damage response pathways. In combination these changes drive cell-cycle progression and give rise to pronounced genetic instability. Several signaling pathways contribute to MCL pathogenesis, including the often constitutively activated PI3K/AKT/mTOR pathway, which promotes tumor proliferation and survival. WNT, Hedgehog, and NF-κB pathways also appear to be important. Although MCL typically responds to frontline chemotherapy, it remains incurable with standard approaches. Proteasome inhibitors (bortezomib), mTOR inhibitors (temsirolimus), and immunomodulatory drugs (lenalidomide) have recently been added to the treatment options in MCL. The molecular basis for the antitumor activity of these agents is an area of intense study that hopefully will lead to further improvements in the near future. Given its unique biology, relative rarity, and the difficulty in achieving long-lasting remissions with conventional approaches, patients with MCL should be encouraged to participate in clinical trials.

Gall bladder and extrahepatic bile duct lymphomas: clinicopathological observations and biological implications

Lymphomas of the gall bladder and extrahepatic bile ducts are exceedingly rare. We present the clinicopathological features of 19 cases from our files; 14 patients had primary lymphoma (13 involving gall bladder and 1 involving common hepatic duct), while 5 had systemic lymphoma on further work-up. Most patients presented with symptoms mimicking cholecystitis. The most common primary lymphoma types were diffuse large B-cell lymphoma, extranodal marginal zone lymphoma, B-lymphoblastic lymphoma, and follicular lymphoma. Two cases had features of lymphomatous polyposis, one a case of follicular lymphoma and the second a case of mantle cell lymphoma, with disease limited to the mantle zones, so-called in situ mantle cell lymphoma. Other rare lymphoma subtypes not described earlier in this site included the extracavitary variant of primary effusion lymphoma and plasmablastic lymphoma. Patients with diffuse large B-cell lymphoma and extranodal marginal zone lymphoma were older (mean age 75.8 y) than those with other subtypes (mean age 47 y) and more likely to have gallstones (60% vs. 12.5%). A comprehensive literature review revealed 36 primary gall bladder and 16 primary extrahepatic bile duct lymphomas. When compared with primary gall bladder lymphomas, those involving the extrahepatic bile ducts present at a younger age (47 y vs. 63 y) usually with obstructive jaundice, and are less often associated with gallstones (17% vs. 50%) or regional lymph node involvement (6% vs. 31%). In conclusion, primary lymphomas of the gall bladder and extrahepatic bile ducts show a broad spectrum of disease types, but in many respects mirror the spectrum of primary lymphomas of the gastrointestinal tract.

Cytogenetic aberrations and their prognostic value in a series of 330 splenic marginal zone B-cell lymphomas: a multicenter study of the Splenic B-Cell Lymphoma Group

We conducted a retrospective collaborative study to cytogenetically characterize splenic marginal zone lymphoma (SMZL) and ascertain the prognostic value of chromosomal aberrations. Of 330 cases, 72% displayed an aberrant karyotype, 53% were complex, and 29% had a single aberration. The predominant aberrations were gains of 3/3q and 12q, deletions of 7q and 6q and translocations involving 8q/1q/14q. CD5 expression was detected in 39 of 158 cases (25%). The cytogenetic makeup of the CD5+ group differed significantly from that of the CD5− group. Cases with unmutated IGHV were significantly associated with deletions of 7q and TP53. A strong association was noted between usage of the IGVH1-2 and deletion 7q, 14q alterations, and abnormal karyotype. On univariate analysis, patients with more than or equal to 2 aberrations, 14q alterations, and TP53 deletions had the shortest survival; 7q deletion did not affect survival. On multivariate analysis, cytogenetic aberrations did not retain prognostic significance; the parameters negatively affecting survival were hemoglobin and age. In conclusion, the cytogenetic profile of SMZL is distinct from other B-cell lymphomas. Complexity of the karyotype, 14q aberrations, and TP53 deletions are poor prognostic indicators and may be considered together with other clinicobiologic parameters to ascertain the prognosis of SMZL.

The basis and rational use of molecular genetic testing in mature B-cell lymphomas

An increasing number of neoplasms are associated with variably specific genetic abnormalities. This is best exemplified by hematological malignancies, in which there is a growing list of entities that are defined by their genetic lesion(s); this is not (yet) the case in mature B-cell lymphomas. However, enhanced insights into the pathogenesis of this large and diverse group of lymphomas have emerged with the ongoing unraveling of a plethora of fascinating genetic abnormalities. The purpose of this review is to synthesize well-recognized data and nascent discoveries in our understanding of the genetic basis of a spectrum of mature B-cell lymphomas, and how this may be applied to contemporary clinical practice. Despite the explosion of new and exciting knowledge in this arena, with the potential for enhanced diagnostic and prognostic strategies, it is essential to remain cognizant of the limitations (and complexity) of genetic investigations, so that assays can be developed and used both judiciously and rationally.

SOX11 expression correlates to promoter methylation and regulates tumor growth in hematopoietic malignancies

Background

The transcription factor SOX11 plays an important role in embryonic development of the central nervous system (CNS) and is expressed in the adult immature neuron but is normally not expressed in any other adult tissue. It has recently been reported to be implicated in various malignant neoplasms, including several lymphoproliferative diseases, by its specific expression and in some cases correlation to prognosis. SOX11 has been shown to prevent gliomagenesis in vivo but the causes and consequences of aberrant expression of SOX11 outside the CNS remain unexplained.

Results

We now show the first function of SOX11 in lymphoproliferative diseases, by demonstrating in vitro its direct involvement in growth regulation, as assessed by siRNA-mediated silencing and ectopic overexpression in hematopoietic malignancies. Gene Chip analysis identified cell cycle regulatory pathways, including Rb-E2F, to be associated with SOX11-induced growth reduction. Furthermore, promoter analysis revealed that SOX11 is silenced through DNA methylation in B cell lymphomas, suggesting that its regulation is epigenetically controlled.

Conclusions

The data show that SOX11 is not a bystander but an active and central regulator of cellular growth, as both siRNA-mediated knock-down and ectopic overexpression of SOX11 resulted in altered proliferation. Thus, these data demonstrate a tumor suppressor function for SOX11 in hematopoietic malignancies and revealed a potential epigenetic regulation of this developmentally involved gene.