New pathogenic mechanisms in Burkitt lymphoma

Update: The molecular spectrum of virus-associated high-grade B-cell non-Hodgkin lymphomas

The vast spectrum of aggressive B-cell non-Hodgkin neoplasms (B-NHL) encompasses several infrequent entities occurring in association with viral infections, posing diagnostic challenges for practitioners. In the emerging era of precision oncology, the molecular characterization of malignancies has acquired paramount significance. The pathophysiological comprehension of specific entities and the identification of targeted therapeutic options have seen rapid development. However, owing to their rarity, not all entities have undergone exhaustive molecular characterization. Considerable heterogeneity exists in the extant body of work, both in terms of employed methodologies and the scale of cases studied. Presently, therapeutic strategies are predominantly derived from observations in diffuse large B-cell lymphoma (DLBCL), the most prevalent subset of aggressive B-NHL. Ongoing investigations into the molecular profiles of these uncommon virus-associated entities are progressively facilitating a clearer distinction from DLBCL, ultimately paving the way towards individualized therapeutic approaches. This review consolidates the current molecular insights into aggressive and virus-associated B-NHL, taking into consideration the recently updated 5th edition of the WHO classification of hematolymphoid tumors (WHO-5HAEM) and the International Consensus Classification (ICC). Additionally, potential therapeutically targetable susceptibilities are highlighted, offering a comprehensive overview of the present scientific landscape in the field.

Clinicopathologic and genetic features of the starry-sky pattern in double-expressor diffuse large B-cell lymphoma

Double expressor lymphoma (DEL) is a subset of diffuse large B-cell lymphoma (DLBCL) characterized by the co-expression of MYC and BCL2 proteins with a poor prognosis. However, there are no standard criteria for evaluating the morphologic features of DEL. We aimed to analyze the prognostic value of the starry-sky pattern (SSP) and its correlation with clinicopathologic and genetic features in 153 DEL cases. The SSP was significantly associated with aggressive parameters, including c-MYC overexpression, CD5 expression, higher IPI, and age-adjusted IPI. In the univariate survival analyses, the presence of SSP was associated with unfavorable progression-free survival (PFS) (p = 0.040), and tended towards an adverse overall survival (OS) (p = 0.061). However, when c-MYC was overexpressed, SSP was significantly correlated with inferior OS (p = 0.019). In the multivariate survival analysis, SSP was also associated with poor PFS (p = 0.048). Additionally, next-generation sequencing data revealed SSP was significantly associated with the KMT2D mutation and had different genetic mutation profiles from non-SSP. In conclusion, SSP may represent morphologic characteristics of aggressiveness in DEL.

Integrative genomic analysis focused on cell cycle genes for MYC-driven aggressive mature B-cell lymphoma

MYC is a transcriptional factor that regulates growth and proliferation through cell cycle pathways. MYC alterations, in particular MYC rearrangements, are important in assessing the prognosis of aggressive B-cell lymphoma. In this study, we focused on the impact of nine major cell cycle genes for MYC-driven aggressive mature B-cell lymphoma and analyzed the mutational status using targeted next generation sequencing. Our 40 cases of aggressive mature B-cell lymphomas included 5 Burkitt lymphomas, 17 high-grade B-cell lymphomas and 18 diffuse large B-cell lymphomas with MYC breaks in 100%, 88% and 11%, respectively. Our data allowed a molecular classification into four categories partially independent from the histopathological diagnosis but correlating with the Ki-67 labelling index: (I) harboring TP53 and CDKN2A mutations, being highly proliferative, (II) with MYC rearrangement associated with MYC and/or ID3 mutations, being highly proliferative, (III) with MYC rearrangement combined with additional molecular changes, being highly proliferative, and (IV) with a diverse pattern of molecular alterations, being less proliferative. Taken together, we found that mutations of TP53, CDKN2A, MYC and ID3 are associated with highly proliferative B-cell lymphomas that could profit from novel therapeutic strategies.

A modular transcriptome map of mature B cell lymphomas

BACKGROUND

Germinal center-derived B cell lymphomas are tumors of the lymphoid tissues representing one of the most heterogeneous malignancies. Here we characterize the variety of transcriptomic phenotypes of this disease based on 873 biopsy specimens collected in the German Cancer Aid MMML (Molecular Mechanisms in Malignant Lymphoma) consortium. They include diffuse large B cell lymphoma (DLBCL), follicular lymphoma (FL), Burkitt's lymphoma, mixed FL/DLBCL lymphomas, primary mediastinal large B cell lymphoma, multiple myeloma, IRF4-rearranged large cell lymphoma, MYC-negative Burkitt-like lymphoma with chr. 11q aberration and mantle cell lymphoma.

METHODS

We apply self-organizing map (SOM) machine learning to microarray-derived expression data to generate a holistic view on the transcriptome landscape of lymphomas, to describe the multidimensional nature of gene regulation and to pursue a modular view on co-expression. Expression data were complemented by pathological, genetic and clinical characteristics.

RESULTS

We present a transcriptome map of B cell lymphomas that allows visual comparison between the SOM portraits of different lymphoma strata and individual cases. It decomposes into one dozen modules of co-expressed genes related to different functional categories, to genetic defects and to the pathogenesis of lymphomas. On a molecular level, this disease rather forms a continuum of expression states than clearly separated phenotypes. We introduced the concept of combinatorial pattern types (PATs) that stratifies the lymphomas into nine PAT groups and, on a coarser level, into five prominent cancer hallmark types with proliferation, inflammation and stroma signatures. Inflammation signatures in combination with healthy B cell and tonsil characteristics associate with better overall survival rates, while proliferation in combination with inflammation and plasma cell characteristics worsens it. A phenotypic similarity tree is presented that reveals possible progression paths along the transcriptional dimensions. Our analysis provided a novel look on the transition range between FL and DLBCL, on DLBCL with poor prognosis showing expression patterns resembling that of Burkitt's lymphoma and particularly on 'double-hit' MYC and BCL2 transformed lymphomas.

CONCLUSIONS

The transcriptome map provides a tool that aggregates, refines and visualizes the data collected in the MMML study and interprets them in the light of previous knowledge to provide orientation and support in current and future studies on lymphomas and on other cancer entities.

Paradoxical role of Id proteins in regulating tumorigenic potential of lymphoid cells

A family of transcription factors known as Id proteins, or inhibitor of DNA binding and differentiation, is capable of regulating cell proliferation, survival and differentiation, and is often upregulated in multiple types of tumors. Due to their ability to promote self-renewal, Id proteins have been considered as oncogenes, and potential therapeutic targets in cancer models. On the contrary, certain Id proteins are reported to act as tumor suppressors in the development of Burkitt's lymphoma in humans, and hepatosplenic and innate-like T cell lymphomas in mice. The contexts and mechanisms by which Id proteins can serve in such contradictory roles to determine tumor outcomes are still not well understood. In this review, we explore the roles of Id proteins in lymphocyte development and tumorigenesis, particularly with respect to inhibition of their canonical DNA binding partners known as E proteins. Transcriptional regulation by E proteins, and their antagonism by Id proteins, act as gatekeepers to ensure appropriate lymphocyte development at key checkpoints. We re-examine the derailment of these regulatory mechanisms in lymphocytes that facilitate tumor development. These mechanistic insights can allow better appreciation of the context-dependent roles of Id proteins in cancers and improve considerations for therapy.

Role of MYC in B Cell Lymphomagenesis

B cell lymphomas mainly arise from different developmental stages of B cells in germinal centers of secondary lymphoid tissue. There are a number of signaling pathways that affect the initiation and development of B cell lymphomagenesis. The functions of several key proteins that represent branching points of signaling networks are changed because of their aberrant expression, degradation, and/or accumulation, and those events determine the fate of the affected B cells. One of the most influential transcription factors, commonly associated with unfavorable prognosis for patients with B cell lymphoma, is nuclear phosphoprotein MYC. During B cell lymphomagenesis, oncogenic MYC variant is deregulated through various mechanisms, such as gene translocation, gene amplification, and epigenetic deregulation of its expression. Owing to alterations of downstream signaling cascades, MYC-overexpressing neoplastic B cells proliferate rapidly, avoid apoptosis, and become unresponsive to most conventional treatments. This review will summarize the roles of MYC in B cell development and oncogenesis, as well as its significance for current B cell lymphoma classification. We compared communication networks within transformed B cells in different lymphomas affected by overexpressed MYC and conducted a meta-analysis concerning the association of MYC with tumor prognosis in different patient populations.

Relevance of ID3-TCF3-CCND3 pathway mutations in pediatric aggressive B-cell lymphoma treated according to the non-Hodgkin Lymphoma Berlin-Frankfurt-Münster protocols

Mature B-cell non-Hodgkin lymphoma is the most common subtype of non-Hodgkin lymphoma in childhood and adolescence. B-cell non-Hodgkin lymphomas are further classified into histological subtypes, with Burkitt lymphoma and Diffuse large B-cell lymphoma being the most common subgroups in pediatric patients. Translocations involving the MYC oncogene are known as relevant but not sufficient for Burkitt lymphoma pathogenesis. Recently published large-scale next-generation sequencing studies unveiled sets of additional recurrently mutated genes in samples of pediatric and adult B-cell non-Hodgkin lymphoma patients. ID3, TCF3 and CCND3 are potential drivers of Burkitt lymphomagenesis. In the study herein, frequency and clinical relevance of mutations in ID3, TCF3 and CCND3 were analyzed within a well-defined cohort of 84 uniformly diagnosed and treated pediatric B-cell non-Hodgkin lymphoma patients of the Berlin-Frankfurt-Münster group. Mutation frequency was 78% (ID3), 13% (TCF3) and 36% (CCND3) in Burkitt lymphoma (including Burkitt leukemia). ID3 and CCND3 mutations were associated with more advanced stages of the disease in MYC rearrangement positive Burkitt lymphoma. In conclusion, ID3-TCF3-CCND3 pathway genes are mutated in more than 88% of MYC-rearranged pediatric B-cell non-Hodgkin lymphoma and the pathway may represent a highly relevant second hit of Burkitt lymphoma pathogenesis, especially in children and adolescents.

Diagnosis of ‘double hit’ diffuse large B-cell lymphoma and B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma: when and how, FISH versus IHC

Identification of large B-cell lymphomas that are “extra-aggressive” and may require therapy other than that used for diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS), is of great interest. Large B-cell lymphomas with MYC plus BCL2 and/or BCL6 rearrangements, so-called ‘double hit’ (DHL) or ‘triple hit’ (THL) lymphomas, are one such group of cases often recognized using cytogenetic FISH studies. Whether features such as morphologic classification, BCL2 expression, or type of MYC translocation partner may mitigate the very adverse prognosis of DHL/THL is controversial. Classification of the DHL/THL is also controversial, with most either dividing them up between the DLBCL, NOS and B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma (BCLU) categories or classifying at least the majority as BCLU. The BCLU category itself has many features that overlap those of DHL/THL. Currently, there is growing interest in the use of MYC and other immunohistochemistry either to help screen for DHL/THL or to identify “double-expressor” (DE) large B-cell lymphomas, defined in most studies as having ≥40% MYC+ and ≥50%-70% BCL2+ cells. DE large B-cell lymphomas are generally aggressive, although not as aggressive as DHL/THL, are more common than DHL/THL, and are more likely to have a nongerminal center phenotype. Whether single MYC rearrangements or MYC expression alone is of clinical importance is controversial. The field of the DHL/THL and DE large B-cell lymphomas is becoming more complex, with many issues left to resolve; however, great interest remains in identifying these cases while more is learned about them.

Burkitt lymphoma research in East Africa: highlights from the 9(th) African organization for research and training in cancer conference held in Durban, South Africa in 2013

A one-day workshop on Burkitt lymphoma (BL) was held at the 9(th) African Organization for Research and Training in Cancer (AORTIC) conference in 2013 in Durban, South Africa. The workshop featured 15 plenary talks by delegates representing 13 institutions that either fund or implement research on BL targeting AORTIC delegates primarily interested in pediatric oncology. The main outcomes of the meeting were improved sharing of knowledge and experience about ongoing epidemiologic BL research, BL treatment in different settings, the role of cancer registries in cancer research, and opportunities for African scientists to publish in scientific journals. The idea of forming a consortium of BL to improve coordination, information sharing, accelerate discovery, dissemination, and translation of knowledge and to build capacity, while reducing redundant efforts was discussed. Here, we summarize the presentations and discussions from the workshop.

The combined expression of VPREB3 and ID3 represents a new helpful tool for the routine diagnosis of mature aggressive B-cell lymphomas

Genomic studies, such as gene expression profiling and next-generation sequencing studies, have provided new insights into the phenotypic characteristics and pathogenesis of mature aggressive B-cell lymphomas. In particular, mutations in the transcription factors ID3 and TCF3, leading to overexpression of B-cell receptor components such as VPREB3, have been shown to be specific for Burkitt lymphoma (BL) and play an important tumourigenic role by mediating the activation of the pro-survival phosphatidylinositol-3-OH kinase pathway. We performed immunohistochemical analysis by applying commercially available anti-VPREB3 antibody to a large cohort of 185 genetically and immunophenotypically characterized mature aggressive B-cell lymphomas and analyzed these results together with recent data on ID3 expression. The combined expression of both VPREB3 and ID3 was associated with a diagnosis of BL with high sensitivity (0.77), high specificity (0.75) and high negative predictive values (0.96), however, with lower positive predictive value (0.30). Double negative cases were absent in the group of BLs but could be found in approximately one third of the remaining cases of mature aggressive B-cell lymphomas. Further, we could not identify a correlation with MYC, BCL2 or BCL6 aberrations with neither VPREB3 nor ID3 expression in each of the diagnostic groups analyzed. Our results, which are in line with recently discovered mutations in next-generation sequencing studies, suggest that the combined immunohistochemical detection of VPREB3 and ID3 is applicable to the routine diagnostic in case of mature aggressive B-cell lymphomas. In particular, it represents a useful and routinely applicable diagnostic tool to exclude BL diagnosis in case of single positive or double negative cases.

Mature B-cell lymphoma and leukemia in children and adolescents-review of standard chemotherapy regimen and perspectives

Mature B-cell non-Hodgkin lymphoma (B-NHL) comprises more than 50% of all non-Hodgkin lymphoma (NHL) in children and adolescents. Many B-NHL subtypes frequently observed in adults are rarely diagnosed in children and adolescents. In this age group, Burkitt lymphoma (BL), Burkitt leukemia or FAB L3 leukemia (B-AL), diffuse large B-cell lymphoma (DLBCL), primary mediastinal large B-cell lymphoma (PMLBL), follicular lymphoma (FL), and aggressive mature B-NHL not further classifiable (B-NHL nfc) are the most common subtypes. Diverse clinical trials demonstrated similar results of current combination chemotherapy regimens succeeding in overall survival rates of more than 80%. However, treatment-related toxicity and the poor prognosis of relapse are serious concerns. Furthermore, specific histological B-NHL subtypes are rare in children and optimal treatment is not established. New treatment modalities are urgently needed for these patient groups. Rituximab, a monoclonal antibody that is already established in the treatment of adults with mature B-NHL, demonstrated promising results in pediatric patients. The definitive role of rituximab in the treatment of children and adolescents with B-NHL needs to be evaluated in prospective controlled clinical trials. This review provides a comprehensive overview of chemotherapy regimens and the perspectives for children and adolescents with mature B-cell lymphoma and leukemia.