Targeting BCL10 by small peptides for the treatment of B cell lymphoma.

Rationale: Constitutive activation of the NF-κB signalling pathway plays a pivotal role in the pathogenesis of activated B cell-like diffuse large B-cell lymphomas (ABC-DLBCLs), the most aggressive and chemoresistant form of DLBCL. In ABC-DLBCLs, the CARMA1-BCL10 (CB) complex forms a filamentous structure and functions as a supramolecular organizing centre (CB-SMOC) that is required for constitutive NF-κB activation, making it an attractive drug target for ABC-DLBCL treatment. However, a pharmaceutical approach targeting CB-SMOC has been lacking. Here, we developed Bcl10 peptide inhibitors (BPIs) that specifically target the BCL10 filamentation process. Methods: Electron microscopy and immunofluorescence imaging were used to visualize the effect of the BPIs on the BCL10 filamentation process. The cytotoxicity of the tested BPIs was evaluated in DLBCL cell lines according to cell proliferation assays. Different in vitro experiments (pharmacokinetics, immunoprecipitation, western blotting, annexin V and PI staining) were conducted to determine the functional mechanisms of the BPIs. The in vivo therapeutic effect of the BPIs was examined in different xenograft DLBCL mouse models. Finally, Ki67 and TUNEL staining and histopathology analysis were used to evaluate the antineoplastic mechanisms and systemic toxicity of the BPIs. Results: We showed that these BPIs can effectively disrupt the BCL10 filamentation process, destabilize BCL10 and suppress NF-κB signalling in ABC-DLBCL cells. By examining a panel of DLBCL cell lines, we found that these BPIs selectively repressed the growth of CB-SMOC-dependent DLBCL cells by inducing apoptosis and cell cycle arrest. Moreover, by converting the BPIs to acquire a D-retro inverso (DRI) configuration, we developed DRI-BPIs with significantly improved intracellular stability and unimpaired BPI activity. These DRI-BPIs selectively repressed the growth of CB-SMOC-dependent DLBCL tumors in mouse xenograft models without eliciting discernible adverse effects. Conclusion: We developed novel BPIs to target the BCL10 filamentation process and demonstrated that targeting BCL10 by BPIs is a potentially safe and effective pharmaceutical approach for the treatment of ABC-DLBCL and other CB-SMOC-dependent malignancies.

Molecular architecture and regulation of BCL10-MALT1 filaments.

The CARD11-BCL10-MALT1 (CBM) complex triggers the adaptive immune response in lymphocytes and lymphoma cells. CARD11/CARMA1 acts as a molecular seed inducing BCL10 filaments, but the integration of MALT1 and the assembly of a functional CBM complex has remained elusive. Using cryo-EM we solved the helical structure of the BCL10-MALT1 filament. The structural model of the filament core solved at 4.9 Å resolution identified the interface between the N-terminal MALT1 DD and the BCL10 caspase recruitment domain. The C-terminal MALT1 Ig and paracaspase domains protrude from this core to orchestrate binding of mediators and substrates at the filament periphery. Mutagenesis studies support the importance of the identified BCL10-MALT1 interface for CBM complex assembly, MALT1 protease activation and NF-κB signaling in Jurkat and primary CD4 T-cells. Collectively, we present a model for the assembly and architecture of the CBM signaling complex and how it functions as a signaling hub in T-lymphocytes.