NOXA-dependent contextual synthetic lethality of BCL-XL inhibition and "osmotic reprogramming" in colorectal cancer.

A sophisticated network of BCL-2 family proteins regulates the mitochondria-associated (intrinsic) apoptosis pathway. Antiapoptotic members such as BCL-XL or MCL-1 safeguard the outer mitochondrial membrane and prevent accidental cell death in a functionally redundant and/or compensatory manner. However, BCL-XL/MCL-1-mediated "dual apoptosis protection" also impairs response of cancer cells to chemotherapy. Here, we show that hyperosmotic stress in the tumor environment abrogates dual BCL-XL/MCL-1 protection. Hypertonicity triggers upregulation of NOXA and loss of MCL-1 and thereby enforces exclusive BCL-XL addiction. Concomitant targeting of BCL-XL is sufficient to unlock the intrinsic apoptosis pathway in colorectal cancer cells. Functionally, "osmotic reprogramming" of the tumor environment grants contextual synthetic lethality to BCL-XL inhibitors in dually BCL-XL/MCL-1-protected cells. Generation of contextual synthetic lethality through modulation of the tumor environment could perspectively boost efficacy of anticancer drugs.

Citation

Gertrud Knoll, Petra Riffelsberger, Danielle Raats, Onno Kranenburg, Martin Ehrenschwender. NOXA-dependent contextual synthetic lethality of BCL-XL inhibition and "osmotic reprogramming" in colorectal cancer. Cell death & disease. 2020 Apr 20;11(4):257

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PMID: 32312973

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