Introduction: This unplanned post-hoc analysis was based on data from the phase Ib DBL1002 study (NCT01569750) and evaluated the association between molecular biomarkers and clinical response to combined treatment with ibrutinib plus rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) in diffuse large B-cell lymphoma (DLBCL) subtypes.

Methods: DLBCL subtyping was conducted using immunohistochemistry. Next-generation sequencing using immunoglobulin H primers assessed minimal residual disease (MRD). A quantitative assay evaluated Bruton's tyrosine kinase (BTK) occupancy by ibrutinib in peripheral blood mononuclear cells. Targeted DNA sequencing examined genetic variants by DLBCL subtype. Secreted protein expression was evaluated with a SomaLogic analyte panel.

Results: Among 21 patients with DLBCL (median age 53.5 years), 17 achieved a complete response (CR) and 4 a partial response (PR). Of the 11 subtyped patients, 9 had a CR (5/7 germinal center B-cell-like [GCB] and 4/4 non-GCB) and 2 had a PR (both GCB). Nine of 12 patients tested for MRD achieved early (cycle 2 day 1) MRD negativity; most had a CR. There was near-complete BTK occupancy at 4 h postdose. Mutation analysis (n = 19) revealed variants including CREBBP, KMT2D, LRP1B, BCL2, and TNFRSF14; only 1 CD79B and TP53 each; no CARD11 or MYD88.

Conclusions: In this study, first-line ibrutinib plus R-CHOP benefited patients with DLBCL, with good overall response rate and early MRD negativity. With a caveat of small sample size, our results showed that a favorable genetic profile and younger patient age may be important to beneficial clinical outcome with ibrutinib plus R-CHOP in DLBCL.

Keywords: Biomarkers; Diffuse large b-cell lymphoma; Ibrutinib; Phase Ib; R-chop; Response to treatment.

The non-germinal center (non-GCB) subtype of diffuse large B-cell lymphoma (DLBCL) has poor clinical outcomes. Bruton's tyrosine kinase (BTK) inhibitors have established therapeutic activity in B-cell malignancies, with modest activity in DLBCL. Zanubrutinib, a potent and selective BTK inhibitor, was evaluated in patients with relapsed or refractory (R/R) non-GCB DLBCL. The BGB-3111-207 study (NCT03145064) was a multicenter, single-arm, phase 2 study. Patients received twice-daily oral zanubrutinib 160 mg until disease progression or unacceptable toxicity. The primary end point was the overall response rate (ORR). Secondary end points included progression-free survival (PFS) and duration of response (DOR). Overall survival (OS) was an exploratory end point. Forty-one patients were enrolled in China after having progressed or not responded to prior therapy. At data cutoff, 4 patients continued treatment with 37 discontinuations. The median follow-up time is 6.8 months, the ORR was 29.3%, and the complete response rate was 17.1%. Median DOR, PFS, and OS were 4.5, 2.8, and 8.4 months, respectively. Adverse events (AEs) leading to treatment discontinuation were reported in 4 patients and grade ≥3 AEs in 48.8% of patients. Major hemorrhage, atrial fibrillation and/or flutter were not observed. Zanubrutinib demonstrated modest antitumor activity in non-GCB DLBCL, like other BTK inhibitors, and a safety profile consistent with previous studies. Through retrospective biomarker testing, potential antitumor activity was observed in patients with both CD79B and MYD88 mutations which have inferior outcomes to immunochemotherapy. Future studies of zanubrutinib in R/R non-GCB DLBCL will focus on developing mechanism-based treatment combinations and biomarker-driven patient selection.

Anti-CD79 antibodies have been effective at targeting B cell lymphoma cells and depleting B cells in animal models. In order to engineer recombinant antibodies with additional effector functions in mice, we cloned and sequenced the full-length cDNAs of the heavy and light chain of a hamster anti-mouse CD79B antibody. Although hamster antibodies represent a unique source of monoclonal antibodies against mouse, rat, and human antigens, sequence information of hamster immunoglobulins (IG) is sparse. Here, we report a new hamster (Cricetulus migratorius) IG lambda constant (IGLC) gene region that is most homologous to mouse IGLC2 and IGLC3.

Background: Diffuse large B-cell lymphoma (DLBCL) is typically treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). However, only 60% of patients are cured with R-CHOP. Polatuzumab vedotin is an antibody-drug conjugate targeting CD79b, which is ubiquitously expressed on the surface of malignant B cells.

Methods: We conducted a double-blind, placebo-controlled, international phase 3 trial to evaluate a modified regimen of R-CHOP (pola-R-CHP), in which vincristine was replaced with polatuzumab vedotin, as compared with standard R-CHOP, in patients with previously untreated intermediate-risk or high-risk DLBCL. Patients 18 to 80 years of age were randomly assigned in a 1:1 ratio to receive six cycles of either pola-R-CHP or R-CHOP, plus two cycles of rituximab alone. The primary end point was investigator-assessed progression-free survival. Secondary end points included overall survival and safety.

Results: Overall, 879 patients underwent randomization: 440 were assigned to the pola-R-CHP group and 439 to the R-CHOP group. After a median follow-up of 28.2 months, the percentage of patients surviving without progression was significantly higher in the pola-R-CHP group than in the R-CHOP group (76.7% [95% confidence interval (CI), 72.7 to 80.8] vs. 70.2% [95% CI, 65.8 to 74.6] at 2 years; stratified hazard ratio for progression, relapse, or death, 0.73 by Cox regression; 95% CI, 0.57 to 0.95; P = 0.02). Overall survival at 2 years did not differ significantly between the groups (88.7% [95% CI, 85.7 to 91.6] in the pola-R-CHP group and 88.6% [95% CI, 85.6 to 91.6] in the R-CHOP group; hazard ratio for death, 0.94; 95% CI, 0.65 to 1.37; P = 0.75). The safety profile was similar in the two groups.

Conclusions: Among patients with previously untreated intermediate-risk or high-risk DLBCL, the risk of disease progression, relapse, or death was lower among those who received pola-R-CHP than among those who received R-CHOP. (Funded by F. Hoffmann-La Roche/Genentech; POLARIX ClinicalTrials.gov number, NCT03274492.).

Diffuse large B-cell lymphoma (DLBCL) is a clinically aggressive and heterogenous disease. Although most patients can be cured by immunochemotherapy, 30-40% patient will ultimately develop relapsed or refractory disease. Here, we investigated the molecular landscapes of patients with diverse responses to R-CHOP. We performed capture-based targeted sequencing on baseline samples of 105 DLBCL patients using a panel consisting of 112 lymphoma-related genes. Subsequently, 81 treatment-naïve patients with measurable disease and followed for over 1 year were included for survival analysis. Collectively, the most commonly seen mutations included IGH fusion (69%), PIM1(33%), MYD88 (29%), BCL2 (29%), TP53 (29%), CD79B (25%) and KMT2D (24%). Patients with TP53 mutations were more likely to have primary refractory disease (87.0% vs 50.0%, P = 0.009). For those with TP53 disruptive mutations, 91.7% patients were in the primary refractory group. Interestingly, BCL-2 somatic hypermutation was only seen in patients without primary refractory disease (P = 0.014). In multivariate analysis, BCL-2 AMplification (hazard ratio [HR] = 2.94, P = 0.022), B2M mutation (HR = 2.99, P = 0.017) and TP53 mutation (HR = 3.19, p<0.001) were independently associated with shorter time to progression (TTP). Furthermore, TP53 mutations was correlated with worse overall survival (P = 0.049). Next, we investigated mutation landscape in patients with wild-type (WT) TP53 (n = 58) and found that patients harboring MYD88 L265P had significantly inferior TTP than those with WT or non-265P (P = 0.046). This study reveals the mutation spectrum of treatment-naive Chinese DLBCL patients.It also confirms the clinical significance of TP53 mutations and indicates the prognostic value of MYD88 L265P in TP53 WT patients. This article is protected by copyright. All rights reserved.

Introduction: Polatuzumab vedotin is an antibody-drug conjugate comprised of an anti-CD79b monoclonal antibody conjugated to monomethyl auristatin (MMAE), a microtubule-disrupting cytotoxin. CD79b is almost exclusively expressed on normal and malignant B-cells, making it an appealing target for novel therapeutics.

Areas covered: This article reviews the current literature on polatuzumab vedotin, including its pharmacology, as well as summarizing the results of clinical trials in relapsed/refractory diffuse large B-cell lymphoma (DLBCL) as a single agent and in combination with other chemotherapies and chemoimmunotherapies. The current landscape of approved therapies for relapsed and refractory DLBCL, as well as other promising novel approaches, is discussed.

Expert opinion: The recent approval of polatuzumab vedotin in combination with bendamustine and rituximab (BR) offers another option to patients with DLBCL who are not eligible for autologous hematopoietic cell transplant or chimeric antigen receptors (CAR)-T cell therapy. In younger patients and those without serious comorbidities, polatuzumab vedotin-BR may serve as bridging therapy to more intensive therapies with reasonable efficacy and tolerability. Polatuzumab vedotin is currently being studied in a randomized trial in the front line setting in combination with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP).

Keywords: CD79b; Diffuse large B cell lymphoma; antibody-drug conjugate; polatuzumab vedotin.

Aims: The purpose of this study was to investigate the prognostic significance of tumor-infiltrating immune cells and microenvironment-relevant genes in nasopharyngeal carcinoma (NPC) and their correlations.

Materials and methods: The "xCell" algorithm was used to calculate the enrichment scores for 33 immune cells in the samples of GSE12452, GSE40290, GSE53819, GSE68799, and GSE102349. The difference of immune cells between NPC group and non-cancerous group and the prognostic value of the immune cells were analyzed. Besides, based on the Microenvironment scores, the differentially expressed genes (DEGs) between the high- and low-score groups were screened to identify the microenvironment-relevant hub genes. Furthermore, the DEGs were used to establish a risk score model for predicting progression-free survival (PFS) via LASSO penalized Cox regression.

Key findings: The scores of B-cells and Memory B-cells of NPC were significantly lower than those of non-cancerous tissues, and they were positively associated with PFS. Moreover, 10 hub genes (PTPRC, CD19, CD79B, BTK, CD79A, SELL, MS4A1, CD38, CD52, and CD22) were identified and positively correlated with B-cells, Memory B-cells, and Microenvironment scores in GSE12452, GSE68799, and GSE102349. High expression levels of CD22, CD38, CD79B, MS4A1, SELL, and PTPRC were associated with longer PFS. Besides, a risk score model composed of DARC, IL33, IGHG1, and SLC6A8 was established with a good performance for PFS prediction.

Significance: These results enhance our understanding of the composition and prognostic significance of tumor-infiltrating immune cells in NPC lesions, and provide potential targets for prognostication and immunotherapy for NPC patients.

Keywords: Gene expression profiling; Immune cells; Microenvironment; Nasopharyngeal carcinoma.

Model-informed drug development (MIDD) has become an important approach to improving clinical trial efficiency, optimizing drug dosing, and proposing drug labeling in the absence of dedicated clinical trials. For the first time, we developed a physiologically based pharmacokinetic (PBPK) model-based approach to assess CYP3A-mediated drug-drug interaction (DDI) risk for polatuzumab vedotin (Polivy), an anti-CD79b-vc-monomethyl auristatin E (MMAE) antibody-drug conjugate (ADC). The model was developed and verified using data from the existing clinical DDI study for brentuximab vedotin, a similar vc-MMAE ADC. Analogous to the brentuximab vedotin clinical study, polatuzumab vedotin at the proposed labeled dose was predicted to have a limited drug interaction potential with strong CYP3A inhibitor and inducer. Polatuzumab vedotin was also predicted to neither inhibit nor induce CYP3A. The present work demonstrated a high-impact application using a PBPK MIDD approach to predict the CYP3A-mediated DDI to enable drug labeling in the absence of any dedicated clinical DDI study. The key considerations for the PBPK report included in the Biologics License Application/Marketing Authorization Application submission, as well as the strategy and responses to address some of the critical and challenging questions from the health authorities following the submission are also discussed. Our experience and associated perspective using a PBPK approach to ultimately enable a drug interaction label claim for polatuzumab vedotin in lieu of a dedicated clinical DDI study, as well as the interactions with the regulatory agencies, further provides confidence in applying MIDD to accelerate the registration and approval of new drug therapies.

Keywords: antibody-drug conjugate; drug labeling; drug-drug interaction; model-informed drug development; physiologically based pharmacokinetics.

Background: Early progression after the first-line R-CHOP treatment leads to a very dismal outcome and necessitates alternative treatment for patients with diffuse large B-cell lymphoma (DLBCL). This study aimed to develop a genetic predictive model for early progression and evaluate its potential in advancing alternative treatment.

Methods: Thirty-two hotspot driver genes were examined in 145 DLBCL patients and 5 DLBCL cell lines using next-generation sequencing. The association of clinical features, cell-of-origin, double expression, positive p53 protein, and gene alterations with early progression was analyzed, and the genetic predictive model was developed based on the related independent variables and assessed by the area under receiver operating characteristic. The potential of novel treatment based on the modeling was investigated in in-vitro DLBCL cell lines and in vivo xenograft mouse models.

Results: The frequency of CD79B (42.86% vs 9.38%, p = 0.000) and PIM1 mutations (38.78% vs 17.71%, p = 0.005) showed a significant increase in patients with early progression. CD79B and PIM1 mutations were associated with complex genetic events, double expression, non-GCB subtype, advance stage and unfavorable prognosis. A powerful genetic predictive model (AUROC = 0.771, 95% CI: 0.689-0.853) incorporating lactate dehydrogenase levels (OR = 2.990, p = 0.018), CD79B mutations (OR = 5.970, p = 0.001), and PIM1 mutations (OR = 3.021, p = 0.026) was created and verified in the other cohort. This modeling for early progression outperformed the prediction accuracy of conventional International Prognostic Index, and new molecular subtypes of MCD and Cluster 5. CD79B and PIM1 mutations indicated a better response to inhibitors of BTK (ibrutinib) and pan-PIM kinase (AZD 1208) through repressing activated oncogenic signaling. Since the two inhibitors failed to decrease BCL2 level, BCL2 inhibitor (venetoclax) was added and demonstrated to enhance their apoptosis-inducing activity in mutant cells with double expression.

Conclusions: The genetic predictive model provides a robust tool to identify early progression and determine precision treatment. These findings warrant the development of optimal alternative treatment in clinical trials.

Keywords: CD79B; Diffuse large B-cell lymphoma; Early progression; PIM1.

Over the last few years, treatment principles have been changed towards more targeted therapy for many B-cell lymphoma subtypes and in chronic lymphocytic leukemia (CLL). Immunotherapeutic modalities, namely monoclonal antibodies (mAbs), bispecific antibodies (bsAbs), antibody-drug conjugates (ADCs), and chimeric antigen receptor T (CAR-T) cell therapy, commonly use B-cell-associated antigens (CD19, CD20, CD22, and CD79b) as one of their targets. T-cell engagers (TCEs), a subclass of bsAbs, work on a similar mechanism as CAR-T cell therapy without the need of previous T-cell manipulation. Currently, several anti-CD20xCD3 TCEs have demonstrated promising efficacy across different lymphoma subtypes with slightly better outcomes in the indolent subset. Anti-CD19xCD3 TCEs are being developed as well but only blinatumomab has been evaluated in clinical trials yet. The results are not so impressive as those with anti-CD19 CAR-T cell therapy. Antibody-drug conjugates targeting different B-cell antigens (CD30, CD79b, CD19) seem to be effective in combination with mAbs, standard chemoimmunotherapy, or immune checkpoint inhibitors. Further investigation will show whether immunotherapy alone or in combinatory regimens has potential to replace chemotherapeutic agents from the first line treatment.

Keywords: antibody-drug conjugates; bispecific antibodies; brentuximab vedotin; epcoritamab; glofitamab; immunotherapy; mosenutuzumab; polatuzumab vedotin.

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous malignancy. Following front-line immunochemotherapy, 30-40% of DLBCL patients develop relapsed or refractory (r/r) disease, which can be treated with ibrutinib. It has been previously reported that MYD88^MUT affects the response to ibrutinib in patients with r/r DLBCL.

Here, we aimed to gather understanding of MYD88^MUT in r/r DLBCL patients and to evaluate its influence on response to ibrutinib.

In this study, tissue samples from DLBCL patients (n = 212) were retrospectively collected and sequenced by target-capturing panels of either 413 or 112 genes that are frequently mutated in non-Hodgkin's lymphoma. Sixty patients with MYD88 mutations and available clinical information were included for further analysis.

RESULTS

Seven MYD88^MUT variants were identified, L265P (65.0%, n = 39), S219C (13.3%, n = 8), S243N (8.3%, n = 5), P258L (6.7%, n = 4), F283V (1.7%, n = 1), P141R (1.7%, n = 1), and V217F (1.7%, n = 1). One patient had MYD88 amplification. In addition, mutations in PIM1 (67%, n = 40), IGH fusion (48%, n = 29), CD79B (43%, n = 26), KMT2D (30%, n = 18), and TP53 (27%, n = 17) were identified. For patients with L265P, IRF4 (p = 0.011) was frequently mutated. Otherwise, TET2 (p = 0.016), NOTCH2 (p = 0.044), MET (p = 0.037), SOCS1 (p = 0.011), TNFRSF14 (p = 0.011), EZH2 (p = 0.037), and BCL6 (p < 0.001) mutations were associated with MYD88^MUT non-L265P variants. The incidence rate of MYD88^MUT L265P was significantly higher with central nervous system involvement (p = 0.034). Four out of nine MYD88^MUT patients responded to ibrutinib containing treatment, and this included those with MYD88^MUT/CD79B^WT.

CONCLUSIONS

This study adds clinical observations with MYD88^MUT patients, further helping to understand the genetic features and possible correlation of MYD88^MUT with response to ibrutinib.

Changes in the thymus and potential mechanisms underlying the pathogenesis in pristane-induced lupus (PIL) mice are poorly understood. This study aimed to systematically and specifically examine changes in the thymus and the potential mechanisms responsible for immunological abnormalities in PIL mice. The results showed that PIL mice exhibit serious thymic hyperplasia, an elevated thymus index, a damaged histopathological structure and increased thymocyte apoptosis. We found that thymic T cell differentiation was impaired as the CD4⁺ CD8⁺ double-positive (DP) thymocyte frequency significantly decreased, becoming almost absent at 28 weeks after induction, while CD4- CD8- double-negative (DN) thymocytes and CD4⁺ CD8- single-positive (CD4⁺ SP) and CD4- CD8⁺ single-positive (CD8⁺ SP) cells were increased. This phenomenon might be explained by an inhibition of the DN-to-DP-cell transition and stimulation of DP cell conversion into CD4⁺ /CD8⁺ SP thymocytes. Moreover, we discovered a dramatic and abnormal increase in thymic B cells, that was associated with CD19, Irf8, Ebf1, Pax5, Irf4, Blk, CXCL13, CXCR5, CD79a, CD79b, Lyn, Syk, Btk, and BLNK gene accumulation, which exhibited positive interactions. We further verified that the mRNA expression of these genes was significantly upregulated and consistent with the RNA-seq results. These results suggest a role of these genes in the increase of B cells in the thymus of PIL mice. In summary, our results showed the changes in the thymus in PIL and elucidated the immunologic abnormalities of increased B cells, potentially providing insight into the associated molecular mechanisms and facilitating further research.

Keywords: abnormal B cell activation; immunological abnormality; impaired T cell differentiation; pristane-induced lupus; thymus.

Abstract: Polatuzumab vedotin is an anti-CD79b antibody conjugated to monomethyl auristatin E that has shown significant clinical activity in follicular and diffuse large B-cell lymphoma (DLBCL) and is currently FDA-approved in combination with bendamustine and rituximab for patients with relapsed/refractory DLBCL. This review article summarizes data from clinical trials of polatuzumab and discusses its current role and future directions in the treatment of patients with B-cell non-Hodgkin lymphoma.

Methods: We conducted a literature search in PubMed and Google Scholar from inception to January 2020, using the following terms: polatuzumab and CD79. We also reviewed the package insert and available abstracts and posters presented at national and international meetings.

Keywords: CD79; antibody-drug conjugate; clinical trials; novel; polatuzumab.

Atherosclerosis involves phenotypic modulation and transdifferentiation of vascular smooth muscle cells (SMCs). Data are given in tabular or figure format that illustrate genome-wide DNA methylation alterations in atherosclerotic vs. control aorta (athero DMRs). Data based upon publicly available chromatin state profiles are also shown for normal aorta, monocyte, and skeletal muscle tissue-specific DMRs and for aorta-specific chromatin features (enhancer chromatin, promoter chromatin, repressed chromatin, actively transcribed chromatin). Athero hypomethylated and hypermethylated DMRs as well as epigenetic and transcription profiles are described for the following genes: ACTA2, MYH10, MYH11 (SMC-associated genes); SMAD3 (a signaling gene for SMCs and other cell types); CD79B and SH3BP2 (leukocyte-associated genes); and TBX20 and genes in the HOXA, HOXB, HOXC, and HOXD clusters (T-box and homeobox developmental genes). The data reveal strong correlations between athero hypermethylated DMRs and regions of enhancer chromatin in aorta, which are discussed in the linked research article "Atherosclerosis-associated differentially methylated regions can reflect the disease phenotype and are often at enhancers" (M. Lacey et al., 2019).

Double-hit lymphoma (DHL) is a rare type of lymphoma with concurrent chromosomal translocations of C-MYC with BCL2 or BCL6, associated with unfavorable prognosis. We describe a case of DHL in a 79-year-old female patient previously diagnosed with diffuse large B-cell lymphoma (DLBCL) with an early relapse in the ascitic fluid. A seven-color multiparametric flow cytometry immunophenotyping study of the ascitic fluid was carried out, and revealed 99.78% of large in size and high cellular complexity B-cells positive for CD19, CD10 (64.27%), CD45 dim, CD22 dim, CD25 (60%), CD43 bright, CD38 bright, and IgM (18.53%); and negative for CD20, CD5, CD23, CD79b, CD103, CD200, CD11c, and FMC7, and 78.99% without light chain expression and 21% with Lambda chain restriction. Due to the expression of CD19 and CD10 with overexpression of BCL-2 protein and due to CD43 and CD38 positivity detected, those cells showed features between DLBCL and Burkitt lymphoma. Fluorescence in situ hybridization (FISH) confirmed both c-MYC/IGH and BCL2/IGH rearrangement. Our findings may help to identify cases requiring additional cytogenetic analysis. © 2015 International Clinical Cytometry Society.

Diffuse large B-cell lymphoma (DLBCL) has a heterogenous biological behavior, and the western literature has reported activating oncogenic mutations in myeloid differentiation primary response gene 88 (MYD88), in conjunction with B-cell receptor signaling pathway genes, CARD11 and CD79B as the driving force for activating the NF-κB pathway implicated in the pathogenesis of DLBCL. The mutation profile of MYD88 genes was evaluated by Sanger sequencing in a cohort of 97 patients [DLBCL (N=55), non-DLBCL lymphomas (N=30), reactive lymphadenopathy (N=10), and 2 cases of lymphoplasmacytic lymphoma (positive control)]. The mutation profile of CARD11 and CD79B were evaluated in 70 patients [DLBCL (N=30), non-DLBCL lymphomas (N=30), and reactive lymphadenopathy (N=10). MYD88 and NF-κB mRNA expression was also evaluated by quantitative reverse transcriptase polymerase chain reaction. These 55 cases of DLBCL were classified into germinal center B-cell and activated B-cell phenotypes using Hans algorithm, of which 58% were of activated B-cell phenotype and 42% were of germinal center B-cell phenotype. MYD88 mutation was seen in 3.6% (2/55) of DLBCL cases, indicating a lower frequency in Indian de novo DLBCL. The mutations detected were novel 33 bp deletion g.7735_7767del (p.V294_S305del) and a splice-acceptor site mutation in exon 5 of MYD88, different from the reported hotspot mutation MYD88 L265P. CARD11 and CD79B mutations were absent in DLBCL and other lymphoma subtypes. MYD88 transcript expression did not correlate with mutational status. NF-κB showed significant overexpression in MYD88 mutation-negative (P=0.004) DLBCL cases indicating that its regulation is independent of MYD88, CARD11, and CD79B mutations, implying the existence of alternative activating pathways. In silico analysis of 2 novel mutations predicted disruptive structural changes in the B-B loop of the translated protein whose biological significance needs further evaluation.

Waldenström macroglobulinemia is a rare indolent B-cell lymphoma. Whole-exome sequencing studies have improved our knowledge of the Waldenström macroglobulinemia mutational landscape. The MYD88 L265P mutation is present in nearly 90% of patients with Waldenström macroglobulinemia. CXCR4 mutations are identified in approximately 30% of MYD88L265P cases and have been associated with ibrutinib resistance in clinical trials. Mutations in CD79B, ARID1a, or TP53 were described at lower frequency. Deciphering the earliest initiating lesions and identifying the molecular alterations leading to disease progression currently represent important goals in the future to identify the most relevant targets for precision therapy in Waldenström macroglobulinemia.

Next-generation sequencing has revealed recurring somatic mutations in Waldenström macroglobulinemia (WM). Common mutations include MYD88 (95%-97%), as well as CXCR4 (30%-40%), ARID1A (17%), and CD79B (8%-15%), which are typically found in MYD88-mutated patients. The genomic findings provide important insights into the pathogenesis, prognostication, and treatment outcome in WM. We discuss the genomic landscape of WM, and the impact of underlying genomics on disease presentation, transcriptional changes, treatment outcome, and overall survival impact.

The transcription factor STAT6 plays a key role in mediating signaling downstream of the receptors for IL-4 and IL-13. In B cells, STAT6 is required for class switch recombination to IgE and for germinal center formation during type 2 immune responses directed against allergens or helminths. In this study, we compared the transcriptomes and proteomes of primary mouse B cells from wild-type and STAT6-deficient mice cultured for 4 d in the presence or absence of IL-4. Microarray analysis revealed that 214 mRNAs were upregulated and 149 were downregulated >3-fold by IL-4 in a STAT6-dependent manner. Across all samples, ∼5000 proteins were identified by label-free quantitative liquid chromatography/mass spectrometry. A total of 149 proteins was found to be differentially expressed >3-fold between IL-4-stimulated wild-type and STAT6-/- B cells (75 upregulated and 74 downregulated). Comparative analysis of the proteome and transcriptome revealed that expression of these proteins was mainly regulated at the transcriptional level, which argues against a major role for posttranscriptional mechanisms that modulate the STAT6-dependent proteome. Nine proteins were selected for confirmation by flow cytometry or Western blot. We show that CD30, CD79b, SLP-76, DEC205, IL-5Rα, STAT5, and Thy1 are induced by IL-4 in a STAT6-dependent manner. In contrast, Syk and Fc receptor-like 1 were downregulated. This dataset provides a framework for further functional analysis of newly identified IL-4-regulated proteins in B cells that may contribute to germinal center formation and IgE switching in type 2 immunity.

Expression of the membrane-bound form of the immunoglobulin (Ig) as part of the antigen receptor is indispensable for both the development and the effector function of B cells. Among five known isotypes, IgM and IgD are the common B cell antigen receptors (BCRs) that are co-expressed in naïve B cells. Despite having identical antigen specificity and being associated with the same signaling heterodimer Igα/Igβ (CD79a/CD79b), IgM and IgD-BCR isotypes functionally differ from each other in the manner of antigen binding, the formation of isolated nanoclusters and in their interaction with co-receptors such as CD19 and CXCR4 on the plasma membrane. With recent developments in experimental techniques, it is now possible to investigate the nanoscale organization of the BCR and better understand early events of BCR engagement. Interestingly, the cytoskeleton network beneath the membrane controls the BCR isotype-specific organization and its interaction with co-receptors. BCR triggering results in reorganization of the cytoskeleton network, which is further modulated by isotype-specific signals from co-receptors. For instance, IgD-BCR is closely associated with CXCR4 on mature B cells and this close proximity allows CXCR4 to employ the BCR machinery as signaling hub. In this review, we discuss the functional specificity and nanocluster assembly of BCR isotypes and the consequences of cross-talk between CXCR4 and IgD-BCR. Furthermore, given the role of BCR and CXCR4 signaling in the development and survival of leukemic B cells, we discuss the consequences of the cross-talk between CXCR4 and the BCR for controlling the growth of transformed B cells.

Antigen uptake and presentation by naive and germinal center (GC) B cells are different, with the former expressing even low-affinity BCRs efficiently capture and present sufficient antigen to T cells, whereas the latter do so more efficiently after acquiring high-affinity BCRs. We show here that antigen uptake and processing by naive but not GC B cells depend on Cbl and Cbl-b (Cbls), which consequently control naive B and cognate T follicular helper (Tfh) cell interaction and initiation of the GC reaction. Cbls mediate CD79A and CD79B ubiquitination, which is required for BCR-mediated antigen endocytosis and postendocytic sorting to lysosomes, respectively. Blockade of CD79A or CD79B ubiquitination or Cbls ligase activity is sufficient to impede BCR-mediated antigen processing and GC development. Thus, Cbls act at the entry checkpoint of the GC reaction by promoting naive B cell antigen presentation. This regulation may facilitate recruitment of naive B cells with a low-affinity BCR into GCs to initiate the process of affinity maturation.

MALT lymphoma is raised from lymphoid cells of mucosa associated lymphoid tissues in a long-term, multistep process of the accumulation of genomic damage very often under the influence of chronic (e.g. Helicobacter pylori) infection. Cytoimmunofluorometric analysis of cell suspensions obtained from mechanically disintegrated bioptic samples of gut mucosa is a very useful approach to detect the presence of MALT lymphoma cells. MALT lymphoma cells are in a great majority of B cell origin. Malignant cells are characterized by the typical characteristic SS parameter, strong expression of CD20 and CD79b molecules, and by the absence of CD5 and CD23 molecules. The ultimate evidence of clonality is immunoglobulin light chains either kappa or lambda expression determination.