Coexistent Rearrangements of c-MYC,BCL2, andBCL6 Genes in a Diffuse Large B-Cell Lymphoma

PRDM15 is a key regulator of metabolism critical to sustain B-cell lymphomagenesis

PRDM (PRDI-BF1 and RIZ homology domain containing) family members are sequence-specific transcriptional regulators involved in cell identity and fate determination, often dysregulated in cancer. The PRDM15 gene is of particular interest, given its low expression in adult tissues and its overexpression in B-cell lymphomas. Despite its well characterized role in stem cell biology and during early development, the role of PRDM15 in cancer remains obscure. Herein, we demonstrate that while PRDM15 is largely dispensable for mouse adult somatic cell homeostasis in vivo, it plays a critical role in B-cell lymphomagenesis. Mechanistically, PRDM15 regulates a transcriptional program that sustains the activity of the PI3K/AKT/mTOR pathway and glycolysis in B-cell lymphomas. Abrogation of PRDM15 induces a metabolic crisis and selective death of lymphoma cells. Collectively, our data demonstrate that PRDM15 fuels the metabolic requirement of B-cell lymphomas and validate it as an attractive and previously unrecognized target in oncology.

Is now the time for molecular driven therapy for diffuse large B-cell lymphoma?

INTRODUCTION

Recent genetic and molecular discoveries regarding alterations in diffuse large B-cell lymphoma (DLBCL) deeply changed the approach to this lymphoproliferative disorder. Novel additional predictors of outcomes and new therapeutic strategies are being introduced to improve outcomes. Areas covered: This review aims to analyse the recent molecular discoveries in DLBCL, the rationale of novel molecular driven treatments and their impact on DLBCL prognosis, especially in ABC-DLBCL and High Grade B Cell Lymphoma. Pre-clinical and clinical evidences are reviewed to critically evaluate the novel DLBCL management strategies. Expert commentary: New insights in DLBCL molecular characteristics should guide the therapeutic approach; the results of the current studies which are investigating safety and efficacy of novel 'X-RCHOP' will probably lead, in future, to a cell of origin (COO) based upfront therapy. Moreover, it is necessary to identify early patients with DLBCL who carried MYC, BCL2 and/or BCL6 rearrangements double hit lymphomas (DHL) because they should not receive standard R-CHOP but high intensity treatment as reported in many retrospective studies. New prospective trials are needed to investigate the more appropriate treatment of DHL.

Prognostic impact of concurrent MYC and BCL6 rearrangements and expression in de novo diffuse large B-cell lymphoma

Double-hit B-cell lymphoma is a common designation for a group of tumors characterized by concurrent translocations of MYC and BCL2, BCL6, or other genes. The prognosis of concurrent MYC and BCL6 translocations is not well known. In this study, we assessed rearrangements and expression of MYC, BCL2 and BCL6 in 898 patients with de novo diffuse large B-cell lymphoma treated with standard chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab). Neither BCL6 translocation alone (more frequent in activated B-cell like diffuse large B-cell lymphoma) nor in combination with MYC translocation (observed in 2.0% of diffuse large B-cell lymphoma) predicted poorer survival in diffuse large B-cell lymphoma patients. Diffuse large B-cell lymphoma patients with MYC/BCL6 co-expression did have significantly poorer survival, however, MYC/BCL6 co-expression had no effect on prognosis in the absence of MYC/BCL2 co-expression, and had no additive impact in MYC⁺/BCL2⁺ cases. The isolated MYC⁺/BCL6⁺/BCL2⁻ subset, more frequent in germinal center B-cell like diffuse large B-cell lymphoma, had significantly better survival compared with the isolated MYC⁺/BCL2⁺/BCL6⁻ subset (more frequent in activated B-cell like diffuse large B-cell lymphoma). In summary, diffuse large B-cell lymphoma patients with either MYC/BCL6 rearrangements or MYC/BCL6 co-expression did not always have poorer prognosis; MYC expression levels should be evaluated simultaneously; and double-hit B-cell lymphoma needs to be refined based on the specific genetic abnormalities present in these tumors.

B-Lymphoblastic Lymphomas Evolving from Follicular Lymphomas Co-Express Surrogate Light Chains and Mutated Gamma Heavy Chains

Follicular lymphoma (FL) is an indolent B-cell non-Hodgkin lymphoma able to transform into germinal center-type diffuse large B-cell lymphoma. We describe four extraordinary cases of FL, which progressed to TdT⁺CD20^- precursor B-lymphoblastic lymphoma (B-LBL). Fluorescence in situ hybridization analysis showed that all four B-LBLs had acquired a MYC translocation on transformation. Comparative genomic hybridization analysis of one case demonstrated that in addition to 26 numerical aberrations that were shared between the FL and B-LBL, deletion of CDKN2A/B and 17q11, 14q32 amplification, and copy-neutral loss of heterozygosity of 9p were gained in the B-LBL cells. Whole-exome sequencing revealed mutations in FMN2, NEB, and SYNE1 and a nonsense mutation in KMT2D, all shared by the FL and B-LBL, and TNFRSF14, SMARCA2, CCND3 mutations uniquely present in the B-LBL. Remarkably, all four FL-B-LBL pairs expressed IgG. In two B-LBLs, evidence was obtained for ongoing rearrangement of IG light chain variable genes and expression of the surrogate light chain. IGHV mutation analysis showed that all FL-B-LBL pairs harbored identical or near-identical somatic mutations. From the somatic gene alterations found in the IG and non-IG genes, we conclude that the FLs and B-LBLs did not develop in parallel from early t(14;18)-positive IG-unmutated precursors, but that the B-LBLs developed from preexistent FL subclones that accumulated additional genetic damage.

[Prognostic analysis of BCL-2/MYC double- hit in diffuse large B-cell lymphoma]

OBJECTIVE

To investigate the effect of BCL-2/MYC double-hit on prognosis in diffuse large B-cell lymphoma（DLBCL）.

METHODS

A retrospective study was conducted to investigate clinical and pathological data of 111 patients with DLBCL. CD10, BCL-6, MUM-1, BCL-2 protein expressions were examined by immune-histochemical methods, and abnormal BCL-2 and MYC genes were analyzed by FISH for patients with sufficient pathological data. SAS 8.2 was adopted to perform Chi- square test, COX's proportional Hazard Model, Life table survival analyses.

RESULTS

Of 111 patients, male 77 cases, female 34 cases, the median age was 55（14-85）years, CD10, BCL-6, MUM-1, BCL-2 positive rates were 15.7%（16/102）, 58.8%（60/102）, 33.0%（34/103）, 74.8（77/103）respectively, the abnormal rate of BCL-2 gene was 43.1%（25/58, 24 cases with multiple copies, 1 case with translocation）, and the abnormal rate of MYC gene was 20.4%（10/49, 10 cases with multiple copies）. Coexistence of BCL-2 and MYC genes abnormalities accounted for 13.0%（6/46）. According to the classification of Hans model, GCB subgroup accounted for 41.2%（42/102）, and non-GCB subgroup 58.8%（60/102）, the median survival time was 24 months, 3-year and 5-year overall survival rates were 48.5% and 39.7% respectively. Overall survival rates of normal and abnormal BCL-2 gene were 34.2%，22.8%, respectively with no statistical significance（P=0.770）. Overall survival rates of normal and abnormal MYC gene were 35.9% and 22.2% ，with no statistical significance（P=0.650）. Overall survival rate of double-hit was 0, far worse than that of single abnormal gene（P=0.034）, which implied double-hit of BCL-2 and MYC gene abnormality to be adverse prognostic factors. BCL-6 protein express could be classified as benign prognostic factors, while ECOG score≥2, escalated IPI index as adverse prognostic factors, and further COX risk model regression analysis indicated that ECOG score, IPI grading and treatment methods were independently adverse factors affecting prognosis. Comprehensive therapy based on chemotherapy could improve outcome.

CONCLUSION

BCL-2/MYC genes double-hit was the factor for the adverse outcome in DLBCL patients. However, ECOG score, IPI risk grading and treatment methods were the independent factors affecting prognosis.

High-resolution copy number analysis of paired normal-tumor samples from diffuse large B cell lymphoma

Copy number analysis can be useful for assessing prognosis in diffuse large B cell lymphoma (DLBCL). We analyzed copy number data from tumor samples of 60 patients diagnosed with DLBCL de novo and their matched normal samples. We detected 63 recurrent copy number alterations (CNAs), including 33 gains, 30 losses, and nine recurrent acquired copy number neutral loss of heterozygosity (CNN-LOH). Interestingly, 20 % of cases acquired CNN-LOH of 6p21 locus, which involves the HLA region. In normal cells, there were no CNAs but we observed CNN-LOH involving some key lymphoma regions such as 6p21 and 9p24.1 (5 %) and 17p13.1 (2.5 %) in DLBCL patients. Furthermore, a model with some specific CNA was able to predict the subtype of DLBCL, 1p36.32 and 10q23.31 losses being restricted to germinal center B cell-like (GCB) DLBCL. In contrast, 8p23.3 losses and 11q24.3 gains were strongly associated with the non-GCB subtype. A poor prognosis was associated with biallelic inactivation of TP53 or 18p11.32 losses, while prognosis was better in cases carrying 11q24.3 gains. In summary, CNA abnormalities identify specific DLBCL groups, and we describe CNN-LOH in germline cells from DLBCL patients that are associated with genes that probably play a key role in DLBCL development.

Acquisition of a t(11;14)(q13;q32) in clonal evolution in a follicular lymphoma with a t(14;18)(q32;q21) and t(3;22)(q27;q11.2)

Chromosome translocations involving an immunoglobulin (IG) locus and another gene, either BCL or MYC, are common events in B-cell lymphoma. Occasionally, two IG loci, one with BCL and the other with MYC, are simultaneously involved; such cases are classified as double-hit (DH) lymphomas. These tumors often show intermediate histologic features between those of diffuse large B-cell lymphoma and those of Burkitt lymphoma. Patients with DH lymphoma have a poor prognosis. Rarely, lymphomas in which three IG loci are simultaneously involved with two different BCL genes and MYC have been reported. These cases are classified as triple-hit lymphomas; virtually all these are aggressive tumors with an even worse prognosis. We present here a unique case of follicular lymphoma (FL) with rearranged BCL2, BCL6, and BCL1 (also known as CCND1) genes. Lymphoma cells at first clinical relapse had a complex karyotype that included a t(3;22)(q27;q11) and t(14;18)(q32;q21). About 15 years after initial diagnosis, the lymphoma cells showed clonal cytogenetic evolution and acquired a t(11;14)(q13;q32). This article is the first case report of a low grade B-cell lymphoma that had three lymphoma-associated reciprocal translocations not involving MYC and that had a long indolent clinical course.

Rearrangements of MYC gene facilitate risk stratification in diffuse large B-cell lymphoma patients treated with rituximab-CHOP

In order to address the debatable prognostic role of MYC rearrangements in diffuse large B-cell lymphoma patients treated with rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisone, we evaluated MYC rearrangements by fluorescence in situ hybridization in 563 cases using break-apart probes and IGH/MYC dual-fusion probes. Concurrent BCL2 and BCL6 aberrations were also assessed. Data were correlated with clinicopathological variables and prognostic parameters. MYC rearrangements were observed in 39/432 evaluable cases (9%), including 4 rearrangements detectable only with the dual-fusion probes, 15 detectable only with the break-apart probes and 20 detectable with both dual-fusion probes and break-apart probes. MYC rearrangements correlated with germinal center B-cell origin (P=0.02), MYC protein expression (P=0.032), and larger tumor mass size (P=0.0003). Patients with MYC rearrangements were more likely to be treatment resistant (P<0.0001). All types of MYC rearrangements were associated with poorer disease-specific survival, that is, 20/39 dead, median disease-specific survival 42 months, compared with 98/393 dead among the non-rearranged cases, median disease-specific survival not reached (P=0.0002). Cases with MYC rearrangements that overexpressed MYC protein were at risk with respect to disease-specific survival independent of the International Prognostic Index (P=0.046 and P<0.001, respectively). Presence of concurrent BCL2 aberrations but not of BCL6 aberrations was prognostically additive. Radiotherapy seemed to diminish the prognostic effects of MYC rearrangements in diffuse large B-cell lymphoma patients since only 2/10 irradiated patients with MYC rearrangements died of/with disease, compared with 16/28 non-irradiated patients with MYC rearrangements. We conclude that MYC rearrangements add prognostic information for individual risk estimation and such cases might represent a distinct, biologically determined disease subgroup.

Diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoid malignancy in adults accounting for 31% of all NHL in Western Countries. Following, morphological, biological and clinical studies have allowed the subdivision of DLBCLs into morphological variants, molecular and immunophenotypic subgroups and distinct disease entities. However, a large number of cases still remain biologically and clinically heterogeneous, for which there are no clear and accepted criteria for subclassification; these are collectively termed DLBCL, not otherwise specified (NOS). DLBCL-NOS occurs in adult patients, with a median age in the seventh decade, but the age range is broad, and it may also occur in children. Clinical presentation, behaviour and prognosis are variable, depending mainly of the extranodal site when they arise. These malignancies present in localized manner in approximately 20% of patients. Disseminated extranodal disease is less frequent, and one third of patients have systemic symptoms. Overall, DLBCLs are aggressive but potentially curable malignancies. Cure rate is particularly high in patients with limited disease with a 5-year PFS ranging from 80% to 85%; patients with advanced disease have a 5-year PFS ≈ 50%. The International Prognostic Index (IPI) and age adjusted IPI (aaIPI) are the benchmarks of DLBCL prognosis. First-line treatment for patients with DLBCL is based on the individual IPI score and age, and three major subgroups should be considered: elderly patients (>60 years, aaIPI=0-3); young patients with low risk (<60 years, aaIPI=0-1); young patients with high risk (<60 years, aaIPI=2-3). The combination of the anti-CD20 monoclonal antibody rituximab and CHOP chemotherapy, every 14 or 21 days, is the standard treatment for DLBCL patients. Recent randomized trials suggest that high-dose chemotherapy supported by autologous stem cell transplant (HDC/ASCT) should not be used as upfront treatment for young high-risk patients outside prospective clinical trials. HDC/ASCT is actually recommended in young patients who did not achieve CR after first-line chemotherapy. Consolidation radiotherapy should be reserved to patients with bulky disease who did not achieve CR after immunochemotherapy. Patients with high IPI score, which indicates increased LDH serum level and the involvement of more than one extranodal site, and patients with involvement of certain extranodal sites (a.e., testes and orbit) should receive CNS prophylaxis as part of first-line treatment. HDC/ASCT should be considered the standard therapy for DLBCL patients with chemotherapy-sensitive relapse. Overall results in patients who cannot be managed with HDC/ASCT due to age or comorbidity are disappointing. New effective and less toxic chemotherapy drugs or biological agents are also worth considering for this specific and broad group of patients. Several novel agents are undergoing evaluation in DLBCL; among other, immunomodulating agents (lenalidomide), m-TOR inhibitors (temsirolimus and everolimus), proteasome inhibitors (bortezomib), histone deacetylase inhibitors (vorinostat), and anti-angiogenetic agents (bevacizumab) are being investigated in prospective trials.

A Practical Approach to the Evaluation of Lymphoid and Plasma Cell Infiltrates in the Lung

Pulmonary biopsy specimens demonstrate varying degrees of infiltration by lymphoid cells and plasma cells, which may raise concern about involvement of a lymphoid or plasma cell neoplasm. Although paraffin section immunohistochemical stains and molecular genotyping studies are capable of assisting in the distinction between reactive and neoplastic infiltrates, it can be difficult to decide what studies to perform. This article describes a practical approach for the evaluation of lymphoid and plasma cell infiltrates in the lung through the identification of several key histologic features.

Diffuse aggressive B-cell lymphomas

Diffuse aggressive B-cell lymphomas comprise a relatively common and increasingly diverse group of neoplasms. Newer modalities including gene expression profiling and an increasing panel of immunohistochemical markers have contributed to greater accuracy in defining these entities. Attention is paid not only to the neoplastic cells but also to the cellular and stromal milieu in which they proliferate. These distinctions may have therapeutic implications as well, with improved outcome related to newer and sometimes targeted therapies. At the same time there is increasing understanding of the overlap, which occurs in the grey zone between diffuse large B-cell lymphoma and Burkitt lymphoma as well as between diffuse large B-cell lymphoma and Hodgkin lymphoma. This review aims to provide practical insights in the correct identification and differential diagnosis of these lymphomas, with emphasis on the changes that have occurred with the publication of the 2008 World Health Organization updated classification.

Mechanisms involved in Burkitt's tumor formation

Burkitt's lymphoma is a rapidly fatal tumor if untreated, but it is curable with intensive polychemotherapy. Unfortunately, the toxicities reported for its treatment in adults are poorly tolerated. Novel therapies aimed at specific molecular targets might prove to be less toxic. A better knowledge of the mechanisms involved in the pathogenesis of Burkitt's lymphoma would facilitate the identification of such targets. This review explores the current knowledge on the alterations found in the three main Burkitt's lymphoma variants.

Epstein-Barr virus and Burkitt lymphoma

Burkitt lymphoma (BL) is an aggressive B-cell malignancy with endemic, sporadic and immunodeficiency-associated variants. It has been known for many years that the fundamental transforming event in BL is the translocation of the MYC gene, and the events that bring about this translocation and those that allow cells to survive with the constitutive expression of MYC have been the subject of intense investigation. Epstein-Barr virus (EBV) infection, malaria, immunodeficiency and spontaneous, somatic mutation can all contribute to the origin and maintenance of this cancer and their mechanisms are the subject of this review.

A novel t(3;8)(q27;q24.1) simultaneously involving both the BCL6 and MYC genes in a diffuse large B-cell lymphoma

Diffuse large B-cell lymphomas (DLBCLs) are a clinically and biologically heterogeneous group of hematologic malignancies. Specific genetic aberrations underlie some of this heterogeneity. These genetic events include distinct and separate translocations resulting in the dysregulated expression of either BCL6 protein with the t(3;14)(q27;q32) or c-MYC protein with the t(8;14)(q24;q32), as a consequence of the juxtaposition of these oncogenes with heterologous promoters or enhancers, such as those of the immunoglobulin heavy chain gene. Here, we report the case of a patient with DLBCL with a unique t(3;8)(q27;q24.1) that involves the BCL6 and MYC genes. We know of no previous report of this translocation in DLBCL, which simultaneously affects two key genes implicated in lymphomagenesis and may reflect a novel genetic mechanism in neoplastic transformation.

Myc translocations in B cell and plasma cell neoplasms

Chromosomal translocations that join the cellular oncogene Myc (c-myc) with immunoglobulin (Ig) heavy-chain (Igh) or light-chain (Igk, Igl) loci are widely believed to be the crucial initiating oncogenic events in the development of B cell and plasma cell neoplasms in three mammalian species: Burkitt lymphoma (BL) in human beings, plasmacytoma (PCT) in mice, and immunocytoma in rats. Among the Myc-Ig translocations found in these neoplasms, mouse PCT T(12;15)(Igh-Myc) is of special interest because it affords a uniquely useful model system to study the fundamental outstanding questions on the mechanisms, genetics, and biological consequences of Myc translocations. Mouse T(12;15) is the direct counterpart of the human BL t(8;14)(q24;q32) translocation and thus of great relevance for human cancer. Mouse T(12;15) is the only cancer-associated translocation in mice that occurs with high incidence, spontaneity, and cell-type specificity. Due to the development of PCR methods for the detection of the underlying reciprocal Myc-Igh junction fragments, it is now known that mouse T(12;15) can be a dynamic process that begins with the genetic exchange of Myc and the Igh switch mu region (Smu), progresses by class switch recombination (CSR) just 3' of the translocation break site, and then undergoes further clonal diversification by micro-deletions in the junction flanks. The molecular pathway that subverts CSR to mediate trans-chromosomal joining of Myc and Smu (translocation origin) and secondary modification of Myc-Igh junctions (translocation "remodeling") has not been elucidated, but recent evidence indicates that it includes CSR factors, such as the activation-induced cytidine deaminase (AID), that may also be involved in the ongoing neoplastic progression of the translocation-bearing tumor precursor. Transgenic mouse models of T(12;15)/t(8;14), including newly developed "iMyc" gene-insertion mice, will be useful in elucidating the role of these CSR factors in the progression of Myc-induced B cell tumors.