ABSTRACT
Survival of activated B cell-subtype (ABC) of diffuse large B cell lymphoma (DLBCL) is driven by chronic B cell receptor (BCR) signaling that activates the canonical NF-κB pathway. Inhibition of BTK by Ibrutinib has been shown to kill ABC DLBCL cells that carry activating mutations in the BCR adaptor CD79. However, mutations in BTK or in downstream components such as CARMA1/CARD11 can render lymphomas Ibrutinib resistant. Therefore, we assessed here the simultaneous inhibition of BTK and the protease MALT1 that acts downstream of CARMA1 and is essential for ABC DLBCL tumor growth. We show that in CD79 mutant cells BTK is a crucial upstream regulator of MALT1, but dispensable in CARMA1 mutant ABC DLBCL. Combined inhibition of BTK by Ibrutinib and MALT1 by S-Mepazine additively impaired MALT1 cleavage activity and expression of NF-κB pro-survival factors. Thereby, combinatorial Ibrutinib and S-Mepazine treatment enhanced killing of CD79 mutant ABC DLBCL cells. Moreover, while expression of oncogenic CARMA1 in CD79 mutant cells conferred Ibrutinib resistance, double mutant cells were still sensitive to MALT1 inhibition by S-Mepazine. Thus, based on the genetic background combinatorial BTK and MALT1 inhibition may improve effectiveness of therapeutic treatment and reduce the chances for the development of drug resistances.
Subject(s)
CD79 Antigens/metabolism , Caspases/metabolism , Mutation , Neoplasm Proteins/metabolism , Protein-Tyrosine Kinases/metabolism , Adenine/analogs & derivatives , Agammaglobulinaemia Tyrosine Kinase , Apoptosis/drug effects , Apoptosis/genetics , Blotting, Western , CARD Signaling Adaptor Proteins/genetics , CARD Signaling Adaptor Proteins/metabolism , CD79 Antigens/genetics , Caspases/genetics , Cell Line, Tumor , Cell Survival/drug effects , Cell Survival/genetics , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/genetics , Drug Synergism , Guanylate Cyclase/genetics , Guanylate Cyclase/metabolism , Humans , Jurkat Cells , Lymphoma, Large B-Cell, Diffuse/genetics , Lymphoma, Large B-Cell, Diffuse/metabolism , Lymphoma, Large B-Cell, Diffuse/pathology , Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein , NF-kappa B/metabolism , Neoplasm Proteins/antagonists & inhibitors , Neoplasm Proteins/genetics , Phenothiazines/chemistry , Phenothiazines/pharmacology , Piperidines , Protein-Tyrosine Kinases/antagonists & inhibitors , Protein-Tyrosine Kinases/genetics , Pyrazoles/pharmacology , Pyrimidines/pharmacology , StereoisomerismABSTRACT
MALT1 paracaspase is activated upon antigen receptor stimulation to promote lymphocyte activation. In addition, deregulated MALT1 protease activity drives survival of distinct lymphomas such as the activated B cell type of diffuse large B cell lymphoma (ABC-DLBCL). Here, we designed fluorophore or biotin-coupled activity based-probes (ABP) that covalently modify the active center of MALT1. MALT1-ABPs are exclusively labeling an active modified full length form of MALT1 upon T cell stimulation. Further, despite the CARMA1 requirement for initial MALT1 activation, the MALT1-ABPs show that protease activity is not confined to the high-molecular CARMA1-BCL10-MALT1 (CBM) complex. Using biotin-coupled ABPs, we developed a robust assay for sensitive and selective detection of active MALT1 in cell lines, primary lymphocytes, and DLBCL tumor biopsies. Taken together, MALT1-ABPs represent powerful chemical tools to measure cellular MALT1 activation, determine efficacy of small molecule inhibitors, and classify lymphomas based on MALT1 activity status.
