Search

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype worldwide, accounting for 40% of all non-Hodgkin lymphomas. DLBCL presents as an aggressive disease requiring immediate treatment. Although significant improvement in outcome has been achieved, ~40% of patients still experience treatment failure. Here, we characterized the recurrent genetic alterations and transcriptomic signatures in diagnostic biopsies from a population registry-based cohort of 347 patients with de novo DLBCL uniformly treated with R-CHOP. This analysis revealed bi-allelic loss of function mutations of TMEM30A that were associated with favorable treatment outcome. TMEM30A is a chaperone protein, involved in maintaining the asymmetric distribution of phosphatidylethanolamine and phosphatidylserine, an integral component of the plasma membrane and “eat-me” signal recognized by macrophages. Using TMEM30A knockout systems by CRISPR genome editing techniques, we have functionally characterized this loss-of-function mutation in representative human and mouse DLBCL cell line models. We have discovered that TMEM30A loss is associated with increased B-cell signaling following antigen stimulation, including a two-fold increase in the diffusion rate of B-cell receptor (BCR) clustering, using high resolution Single Particle Tracking (SPT) technology. In addition, we have measured three-fold increase in chemotherapeutic drug accumulation in both knockout cell lines and randomly selected patient biopsies with TMEM30A biallelic loss. This observation was validated in a xenograft mouse model, which presented improved survival and limited tumor growth following vincristine treatment in mice injected with TMEM30A null DLBCL cell lines compared with native cell lines. This phenotype explains the improved prognosis observed in DLBCL patients following R-CHOP treatment. Furthermore, we have observed over two fold higher numbers of tumor-associated macrophages in B-cell lymphoma syngeneic mouse models with Tmem30a loss-of-function, prior to any form of treatment, suggesting the existence of “hot” and primed tumors. Our data highlight a multi-faceted role for TMEM30A and plasma membrane physiology in B-cell lymphomagenesis, and characterize intrinsic and extrinsic vulnerabilities of cancer cells that can be therapeutically exploited. Characterization of these mechanisms will address a missing link in the cancer field as related insights in lymphoma will outline therapeutic approaches that can be extended to cancer therapy in general. Citation Format: Shannon Healy, Daisuke Ennishi, Ali Bashashati, Saeed Saberi, Christoffer Hother, Anja Mottok, Fong Chun Chan, Lauren Chong, Robert Kridel, Merrill Boyle, Barbara Meissner, Tomohiro Aoki, Katsuyoshi Takata, Bruce W. Woolcock, Elena Vigano, Libin Abraham, Michael Gold, Adele Telenius, Pedro Farinha, Graham Slack, Susana Ben-Neriah, Daniel Lai, Allen W. Zhang, Sohrab Salehi, Hennady P. Shulha, Derek S. Chiu, Sara Mostafavi, Alina S. Gerrie, Diego Villa, Laurie H. Sehn, Kerry J. J. Savage, Andrew J. J. Mungall, Andrew P. Weng, Marcel Bally, Ryan D. Morin, Gabriela V. Cohen Freue, Joseph M. Connors, Marco A. Marra, Sohrab P. Shah, Randy D. Gascoyne1, David W. Scott, Christian Steidl, Ulrich Steidl. TMEM30A loss-of-function mutations drive lymphomagenesis and confer therapeutically exploitable vulnerability in B-cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3480.

Transcription factors play a central role in malignant transformation by activating or repressing waves of downstream target genes. Therapeutic targeting of transcription factors can reprogram cancer cells to lose their advantages in growth and survival. The BCL6 transcriptional repressor plays a central role in the pathogenesis of diffuse large B-cell lymphomas (DLBCL) and controls downstream checkpoints, including the p53 tumor suppressor gene. We report that a specific inhibitor of BCL6 called BPI can trigger a p53 response in DLBCL cells. This was partially due to induction of p53 activity and partially due to relief of direct repression by BCL6 of p53 target genes. BPI could thus induce a p53-like response even in the presence of mutant p53. Moreover, sequential BCL6 peptide inhibitors followed by p53 peptide or small-molecule activators provided a more powerful antilymphoma effect than either treatment alone by maximally restoring p53 target gene expression. Therefore, tandem targeting of the overlapping BCL6 and p53 transcriptional programs can correct aberrant survival pathways in DLBCL and might provide an effective therapeutic approach to lymphoma therapy. [Cancer Res 2008;68(9):3361–9]