High frequency of inactivating tetraspanin C D37 mutations in diffuse large B-cell lymphoma at immune-privileged sites

Red blood cell dynamics during malaria infection violate the assumptions of mathematical models of infection dynamics

For decades, mathematical models have been used to understand the course and outcome of malaria infections (i.e., infection dynamics) and the evolutionary dynamics of the parasites that cause them. A key conclusion of these models is that red blood cell (RBC) availability is a fundamental driver of infection dynamics and parasite trait evolution. The extent to which this conclusion holds will in part depend on model assumptions about the host-mediated processes that regulate RBC availability i.e., removal of uninfected RBCs and supply of RBCs. Diverse mathematical functions have been used to describe host-mediated RBC supply and clearance, but it remains unclear whether they adequately capture the dynamics of RBC supply and clearance during infection. Here, we use a unique dataset, comprising time-series measurements of erythrocyte (i.e., mature RBC) and reticulocyte (i.e., newly supplied RBC) densities during Plasmodium chabaudi malaria infection, and a quantitative data-transformation scheme to elucidate whether RBC dynamics conform to common model assumptions. We found that RBC clearance and supply are not well described by mathematical functions commonly used to model these processes. Furthermore, the temporal dynamics of both processes vary with parasite growth rate in a manner again not captured by existing models. Together, these finding suggest that new model formulations are required if we are to explain and ultimately predict the within-host population dynamics and evolution of malaria parasites.

Clonal Relationship and Mutation Analysis in Lymphoplasmacytic Lymphoma/Waldenström Macroglobulinemia Associated With Diffuse Large B-cell Lymphoma

Patients with lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) occasionally develop diffuse large B-cell lymphoma (DLBCL). This mostly results from LPL/WM transformation, although clonally unrelated DLBCL can also arise. LPL/WM is characterized by activating MYD88L265P (>95%) and CXCR4 mutations (~30%), but the genetic drivers of transformation remain to be identified. Here, in thirteen LPL/WM patients who developed DLBCL, the clonal relationship of LPL and DLBCL together with mutations contributing to transformation were investigated. In 2 LPL/WM patients (15%), high-throughput sequencing of immunoglobulin gene rearrangements showed evidence of >1 clonal B-cell population in LPL tissue biopsies. In the majority of LPL/WM patients, DLBCL presentations were clonally related to the dominant clone in LPL, providing evidence of transformation. However, in 3 patients (23%), DLBCL was clonally unrelated to the major malignant B-cell clone in LPL, of which 2 patients developed de novo DLBCL. In this study cohort, LPL displayed MYD88L265P mutation in 8 out of eleven patients analyzed (73%), while CXCR4 mutations were observed in 6 cases (55%). MYD88WT LPL biopsies present in 3 patients (27%) were characterized by CD79B and TNFAIP3 mutations. Upon transformation, DLBCL acquired novel mutations targeting BTG1, BTG2, CD79B, CARD11, TP53, and PIM1. Together, we demonstrate variable clonal B-cell dynamics in LPL/WM patients developing DLBCL, and the occurrence of clonally unrelated DLBCL in about one-quarter of LPL/WM patients. Moreover, we identified commonly mutated genes upon DLBCL transformation, which together with preserved mutations already present in LPL characterize the mutational landscape of DLBCL occurrences in LPL/WM patients.

Role of RNA Splicing Mutations in Diffuse Large B Cell Lymphoma

Ribonucleic acid splicing is a crucial process to create a mature mRNA molecule by removing introns and ligating exons. This is a highly regulated process, but any alteration in splicing factors, splicing sites, or auxiliary components affects the final products of the gene. In diffuse large B-cell lymphoma, splicing mutations such as mutant splice sites, aberrant alternative splicing, exon skipping, and intron retention are detected. The alteration affects tumor suppression, DNA repair, cell cycle, cell differentiation, cell proliferation, and apoptosis. As a result, malignant transformation, cancer progression, and metastasis occurred in B cells at the germinal center. B-cell lymphoma 7 protein family member A (BCL7A), cluster of differentiation 79B (CD79B), myeloid differentiation primary response gene 88 (MYD88), tumor protein P53 (TP53), signal transducer and activator of transcription (STAT), serum- and glucose-regulated kinase 1 (SGK1), Pou class 2 associating factor 1 (POU2AF1), and neurogenic locus notch homolog protein 1 (NOTCH) are the most common genes affected by splicing mutations in diffuse large B cell lymphoma.

Fatty acid metabolism in aggressive B-cell lymphoma is inhibited by tetraspanin CD37

The importance of fatty acid (FA) metabolism in cancer is well-established, yet the mechanisms underlying metabolic reprogramming remain elusive. Here, we identify tetraspanin CD37, a prognostic marker for aggressive B-cell lymphoma, as essential membrane-localized inhibitor of FA metabolism. Deletion of CD37 on lymphoma cells results in increased FA oxidation shown by functional assays and metabolomics. Furthermore, CD37-negative lymphomas selectively deplete palmitate from serum in mouse studies. Mechanistically, CD37 inhibits the FA transporter FATP1 through molecular interaction. Consequently, deletion of CD37 induces uptake and processing of exogenous palmitate into energy and essential building blocks for proliferation, and inhibition of FATP1 reverses this phenotype. Large lipid deposits and intracellular lipid droplets are observed in CD37-negative lymphoma tissues of patients. Moreover, inhibition of carnitine palmitoyl transferase 1 A significantly compromises viability and proliferation of CD37-deficient lymphomas. Collectively, our results identify CD37 as a direct gatekeeper of the FA metabolic switch in aggressive B-cell lymphoma.

Tetraspanin CD37 deficiency has been reported as a prognostic marker for aggressive B-cell lymphoma. Here, the authors show that CD37 interacts with the fatty acid transporter 1 to inhibit palmitate uptake and its deficiency leads to increased fatty acid metabolism which promotes tumorigenesis in B-cell lymphoma.

CD37 expression in follicular lymphoma

CD37 is a tetraspanin protein expressed in various B-cell lymphomas that mediates tumor survival signaling. Follicular lymphoma (FL) is a representative B-cell neoplasm composed of germinal center B cells. In recent years, CD37 has been focused on as a therapeutic target for B-cell lymphoma. The purpose of this study was to characterize CD37 expression in FL patients to identify risk factors associated with various prognostic factors. We retrospectively reviewed 167 cases of FL and evaluated the immunohistochemical expression of CD37 and its statistical association with clinicopathological features. Immunohistochemically, CD37 was observed in the cytoplasm and/or membrane of neoplastic cells, mainly in neoplastic follicles to various extents. One hundred cases (100/167, 60.0%) were categorized as CD37-positive, and 67 cases were CD37-negative. In cases with high Follicular Lymphoma International Prognostic Index (FLIPI), CD37-negative cases had a poor overall survival compared with CD37-positive cases (P = 0.047), although no significant differences were observed in other clinicopathologic factors, including histological grade, BCL2-IGH translocation, and immunohistochemical phenotype. Therefore, CD37 protein may play a role in tumor progression and may serve as a therapeutic target. However, further studies are needed to explore its significance.

IRF8 is a transcriptional activator of CD37 expression in diffuse large B-cell lymphoma

IRF8 is a transcriptional regulator of CD37 expression in DLBCL, which may have implications for anti-CD37 therapies.

Patients with poor prognostic CD37-negative DLBCL show significantly lower IRF8 expression compared with patients with CD37-positive DLBCL.

Diffuse large B-cell lymphoma (DLBCL) represents the most common form of non-Hodgkin lymphoma (NHL) that is still incurable in a large fraction of patients. Tetraspanin CD37 is highly expressed on mature B lymphocytes, and multiple CD37-targeting therapies are under clinical development for NHL. However, CD37 expression is nondetectable in ∼50% of DLBCL patients, which correlates with inferior treatment outcome, but the underlying mechanisms for differential CD37 expression in DLBCL are still unknown. Here, we investigated the regulation of the CD37 gene in human DLBCL at the (epi-)genetic and transcriptional level. No differences were observed in DNA methylation within the CD37 promoter region between CD37-positive and CD37-negative primary DLBCL patient samples. On the contrary, CD37-negative DLBCL cells specifically lacked CD37 promoter activity, suggesting differential regulation of CD37 gene expression. Using an unbiased quantitative proteomic approach, we identified transcription factor IRF8 to be significantly higher expressed in nuclear extracts of CD37-positive as compared with CD37-negative DLBCL. Direct binding of IRF8 to the CD37 promoter region was confirmed by DNA pulldown assay combined with mass spectrometry and targeted chromatin immunoprecipitation (ChIP). Functional analysis indicated that IRF8 overexpression enhanced CD37 protein expression, while CRISPR/Cas9 knockout of IRF8 decreased CD37 levels in DLBCL cell lines. Immunohistochemical analysis in a large cohort of primary DLBCL (n = 206) revealed a significant correlation of IRF8 expression with detectable CD37 levels. Together, this study provides new insight into the molecular mechanisms underlying differential CD37 expression in human DLBCL and reveals IRF8 as a transcriptional regulator of CD37 in B-cell lymphoma.

Testicular Diffuse Large B-Cell Lymphoma-Clinical, Molecular, and Immunological Features

Simple Summary

Testicular diffuse large B-cell lymphoma (T-DLBCL) is a rare and aggressive lymphoma entity that mainly affects elderly men. It has a high relapse rate with especially the relapses of the central nervous system associating with dismal outcome. T-DLBCL has a unique biology with distinct genetic characteristics and clinical presentation, and the increasing knowledge on the tumor microenvironment of T-DLBCL highlights the significance of the host immunity and immune escape in this rare lymphoma, presenting in an immune-privileged site of the testis. This review provides an update on the latest progress made in T-DLBCL research and summarizes the clinical perspectives in T-DLBCL.

Abstract

Primary testicular lymphoma is a rare lymphoma entity, yet it is the most common testicular malignancy among elderly men. The majority of the cases represent non-germinal center B-cell-like (non-GCB) diffuse large B-cell lymphoma (DLBCL) with aggressive clinical behavior and a relatively high relapse rate. Due to the rareness of the disease, no randomized clinical trials have been conducted and the currently recognized standard of care is based on retrospective analyses and few phase II trials. During recent years, the tumor microenvironment (TME) and tumor-related immunity have been the focus of many tumor biology studies, and the emergence of targeted therapies and checkpoint inhibitors has significantly modulated the field of cancer therapies. Testicular DLBCL (T-DLBCL) is presented in an immune-privileged site of the testis, and the roles of NF-κB pathway signaling, 9p24.1 aberrations, and tumor-infiltrating immune cells, especially immune checkpoint expressing lymphocytes and macrophages, seem to be unique compared to other lymphoma entities. Preliminary data on the use of immune checkpoint inhibitors in the treatment of T-DLBCL are promising and more studies are ongoing.

The Context-Dependent Impact of Integrin-Associated CD151 and Other Tetraspanins on Cancer Development and Progression: A Class of Versatile Mediators of Cellular Function and Signaling, Tumorigenesis and Metastasis

Simple Summary

Tetraspanins are a family of molecules abundantly expressed on the surface of normal or tumor cells. They have been implicated in recruiting or sequestering key molecular regulators of malignancy of a variety of human cancers, including breast and lung cancers, glioblastoma and leukemia. Yet, how their actions take place remains mysterious due to a lack of traditional platform for molecular interactions. The current review digs into this mystery by examining findings from recent studies of multiple tetraspanins, particularly CD151. The molecular basis for differential impact of tetraspanins on tumor development, progression, and spreading to secondary sites is highlighted, and the complexity and plasticity of their control over tumor cell activities and interaction with their surroundings is discussed. Finally, an outlook is provided regarding tetraspanins as candidate biomarkers and targets for the diagnosis and treatment of human cancer.

Abstract

As a family of integral membrane proteins, tetraspanins have been functionally linked to a wide spectrum of human cancers, ranging from breast, colon, lung, ovarian, prostate, and skin carcinomas to glioblastoma. CD151 is one such prominent member of the tetraspanin family recently suggested to mediate tumor development, growth, and progression in oncogenic context- and cell lineage-dependent manners. In the current review, we summarize recent advances in mechanistic understanding of the function and signaling of integrin-associated CD151 and other tetraspanins in multiple cancer types. We also highlight emerging genetic and epigenetic evidence on the intrinsic links between tetraspanins, the epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs), and the Wnt/β-catenin pathway, as well as the dynamics of exosome and cellular metabolism. Finally, we discuss the implications of the highly plastic nature and epigenetic susceptibility of CD151 expression, function, and signaling for clinical diagnosis and therapeutic intervention for human cancer.

Novel CD37, Humanized CD37 and Bi-Specific Humanized CD37-CD19 CAR-T Cells Specifically Target Lymphoma

Simple Summary

Chimeric antigen receptor (CAR) T cell therapy represents a major advancement in cancer treatment. Recently, FDA approved CAR-T cells directed against the CD19 protein for treatment of leukemia and lymphoma. In spite of impressive clinical responses with CD19-CAR-T cells, some patients demonstrate disease relapse due to either antigen loss, cancer heterogeneity or other mechanisms. Novel CAR-T cells and targets are important for the field. This report describes novel CD37, humanized CD37 and bispecific humanized CD37-CD19-CAR-T cells targeting both CD37 and CD19. The study demonstrates that these novel CAR-T cells specifically targeted either CD37 positive or CD37 and CD19-positive cells with endogenous and exogenous protein expression and provides a basis for future clinical studies.

Abstract

CD19 and CD37 proteins are highly expressed in B-cell lymphoma and have been successfully targeted with different monotherapies, including chimeric antigen receptor (CAR)-T cell therapy. The goal of this study was to target lymphoma with novel CD37, humanized CD37, and bi-specific humanized CD37-CD19 CAR-T cells. A novel mouse monoclonal anti-human CD37 antibody (clone 2B8D12F2D4) was generated with high binding affinity for CD37 antigen (KD = 1.6 nM). The CD37 antibody specifically recognized cell surface CD37 protein in lymphoma cells and not in multiple myeloma or other types of cancer. The mouse and humanized CD37-CAR-T cells specifically killed Raji and CHO-CD37 cells and secreted IFN-gamma. In addition, we generated bi-specific humanized hCD37-CD19 CAR-T cells that specifically killed Raji cells, CHO-CD37, and Hela-CD19 cells and did not kill control CHO or Hela cells. Moreover, the hCD37-CD19 CAR-T cells secreted IFN-gamma against CD37-positive and CD19-positive target CHO-CD37, Hela-CD19 cells, respectively, but not against CD19 and CD37-negative parental cell line. The bi-specific hCD37-CD19 significantly inhibited Raji xenograft tumor growth and prolonged mouse survival in NOD scid gamma mouse (NSG) mouse model. This study demonstrates that novel humanized CD37 and humanized CD37-CD19 CAR-T cells specifically targeted either CD37 positive or CD37 and CD19-positive cells and provides a basis for future clinical studies.

A phase Ib, open-label, dose-escalation trial of the anti-CD37 monoclonal antibody, BI 836826, in combination with gemcitabine and oxaliplatin in patients with relapsed/refractory diffuse large B-cell lymphoma

Background BI 836826 is a chimeric mouse–human monoclonal antibody directed against human CD37, a transmembrane protein expressed on mature B lymphocytes. This open-label, phase I dose-escalation trial (NCT02624492) was conducted to determine the maximum tolerated dose (MTD), safety/tolerability, and preliminary efficacy of BI 836826 in combination with gemcitabine and oxaliplatin in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL). Methods Eligible patients received intravenous infusions of BI 836826 on day 8 and gemcitabine 1000 mg/m² plus oxaliplatin 100 mg/m² on day 1, for up to six 14-day treatment cycles. Dose escalation followed the standard 3 + 3 design. Results Of 21 treated patients, 17 had relapsed/refractory DLBCL and four had follicular lymphoma transformed to DLBCL. BI 836826 dosing started at 25 mg and proceeded through 50 mg and 100 mg. Two dose-limiting toxicities (DLTs) occurred during cycle 1, both grade 4 thrombocytopenia lasting > 7 days, affecting 1/6 evaluable patients (17%) in both the 50 mg and 100 mg cohorts. Due to early termination of the study, the MTD was not determined. The most common adverse events related to BI 836826 treatment were neutropenia (52%), thrombocytopenia (48%), and anemia (48%). Eight patients (38%) experienced BI 836826-related infusion-related reactions (two grade 3). Overall objective response rate was 38%, including two patients (10%) with complete remission and six patients (29%) with partial remission. Conclusions BI 836826 in combination with GemOx was generally well tolerated but did not exceed the MTD at doses up to 100 mg given every 14 days.

CD37 in B Cell Derived Tumors-More than Just a Docking Point for Monoclonal Antibodies

CD37 is a tetraspanin expressed prominently on the surface of B cells. It is an attractive molecular target exploited in the immunotherapy of B cell-derived lymphomas and leukemia. Currently, several monoclonal antibodies targeting CD37 as well as chimeric antigen receptor-based immunotherapies are being developed and investigated in clinical trials. Given the unique role of CD37 in the biology of B cells, it seems that CD37 constitutes more than a docking point for monoclonal antibodies, and targeting this molecule may provide additional benefit to relapsed or refractory patients. In this review, we aimed to provide an extensive overview of the function of CD37 in B cell malignancies, providing a comprehensive view of recent therapeutic advances targeting CD37 and delineating future perspectives.