A multiprotein supercomplex controlling oncogenic signalling in lymphoma.

Therapeutic Approaches

Abstract

B cell receptor (BCR) signaling has emerged as a therapeutic target in B cell lymphomas, but inhibiting this pathway in diffuse large B cell lymphoma (DLBCL) has benefited only a subset of patients1. Gene expression profiling identified two major DLBCL subtypes, known as germinal center (GC) B cell-like (GCB) and activated B cell-like (ABC)2,3, with inferior outcomes following immunochemotherapy in ABC. Autoantigens drive BCR-dependent activation of NF-κB in ABC DLBCL through a kinase cascade of SYK, BTK and PKCβ to promote the assembly of the CARD11-BCL10-MALT1 (CBM) adapter complex that recruits and activates IκB kinase (IKK)4-6. Genome sequencing revealed gain-of-function mutations targeting the CD79A and CD79B BCR subunits and the Toll-like receptor (TLR) signaling adapter MYD885,7, with MYD88L265P being the most prevalent isoform. In a clinical trial, the BTK inhibitor, ibrutinib, produced responses in 37% of ABC cases1. The most striking response rate (80%) was observed in tumors with both CD79B and MYD88L265P mutations, but how these mutations cooperate to promote dependence on BCR signaling remains unclear. Herein, we used genome-wide CRISPR-Cas9 screening and functional proteomics to understand the molecular basis of exceptional clinical responses to ibrutinib. We discovered a new mode of oncogenic BCR signaling in ibrutinib-responsive cell lines and biopsies, coordinated by a multiprotein supercomplex formed by MYD88, TLR9, and the BCR (My-T-BCR). The My-T-BCR co-localizes with mTOR on endolysosomes, where it drives pro-survival NF-κB and mTOR signaling. Inhibitors of BCR and mTOR signaling cooperatively decreased My-T-BCR supercomplex formation and function, providing mechanistic insight into their synergistic toxicity for My-T-BCR+ DLBCL cells. My-T-BCR complexes characterized ibrutinib-responsive malignancies and distinguished ibrutinib responders from non-responders. Our data provide a roadmap for the rational deployment of oncogenic signaling inhibitors in molecularly-defined subsets of DLBCL.

Authors

Phelan, James D; Young, Ryan M; Webster, Daniel E; Roulland, Sandrine; Wright, George W; Kasbekar, Monica; Shaffer, Arthur L; Ceribelli, Michele; Wang, James Q; Schmitz, Roland; Nakagawa, Masao; Bachy, Emmanuel; Huang, Da Wei; Ji, Yanlong; Chen, Lu; Yang, Yandan; Zhao, Hong; Yu, Xin; Xu, Weihong; Palisoc, Maryknoll M; Valadez, Racquel R; Davies-Hill, Theresa; Wilson, Wyndham H; Chan, Wing C; Jaffe, Elaine S; Gascoyne, Randy D; Campo, Elias; Rosenwald, Andreas; Ott, German; Delabie, Jan; Rimsza, Lisa M; Rodriguez, Fausto J; Estephan, Fayez; Holdhoff, Matthias; Kruhlak, Michael J; Hewitt, Stephen M; Thomas, Craig; Pittaluga, Stefania; Oellerich, Thomas; Staudt, Louis M;

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