Response to Bruton's tyrosine kinase inhibitors in aggressive lymphomas linked to chronic selective autophagy.

Diffuse large B cell lymphoma (DLBCL) is an aggressive, profoundly heterogeneous cancer, presenting a challenge for precision medicine. Bruton's tyrosine kinase (BTK) inhibitors block B cell receptor (BCR) signaling and are particularly effective in certain molecular subtypes of DLBCL that rely on chronic active BCR signaling to promote oncogenic NF-κB. The MCD genetic subtype, which often acquires mutations in the BCR subunit, CD79B, and in the innate immune adapter, MYD88 ^L265P , typically resists chemotherapy but responds exceptionally to BTK inhibitors. However, the underlying mechanisms of response to BTK inhibitors are poorly understood. Herein, we find a non-canonical form of chronic selective autophagy in MCD DLBCL that targets ubiquitinated MYD88 ^L265P for degradation in a TBK1-dependent manner. MCD tumors acquire genetic and epigenetic alterations that attenuate this autophagic tumor suppressive pathway. In contrast, BTK inhibitors promote autophagic degradation of MYD88 ^L265P , thus explaining their exceptional clinical benefit in MCD DLBCL.
Competing Interests: Declaration of interests T.O. received research funding from Gilead and Merck KGaA, is a consultant/received honoraria for/from Beigene, Roche, Janssen, Merck KGaA, Gilead, Kronos Bio and Abbvie (all not related to this work). Z.W. is a current employee at GSK. A.L.S III is a current employee at AstraZeneca and has stock options.
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