Abstract A010: Proteasome inhibitors induce a BAX and BAK independent, non-canonical apoptosis

Abstract

Abstract In the intrinsic pathway of apoptosis, death stimuli (including drugs, cellular stress, viral infections, etc.) trigger the oligomerization of BAX and BAK resulting in pore formation in the outer mitochondrial membrane to release cytochrome c from the intermembrane space. The released cytochrome c then activates APAF-1 and CASPASE9 to form a 1.4 MDa complex known as apoptosome, which recruits and activates downstream caspases that dismantle the cell. However, we have found that proteasome inhibition leads to a BAX and BAK independent apoptotic cell death. We show using immunofluorescence, fluorogenic assays, and flow cytometry that the proteasome inhibitors, bortezomib and MG-132, trigger a caspase dependent cell death that requires the apoptosome components APAF-1 and CASPASE9, but not cytochrome c. Furthermore, size exclusion chromatography revealed that unlike classical death stimuli, which induce the mega-dalton canonical apoptosome fomation, proteasome inhibitors induce a minor shift in APAF-1, forming a smaller, non-canonical apoptosome. Current efforts are focused on the identification of the APAF-1 activator. Our results indicate the existence of a non-canonical caspase-dependent cell death pathway, which could be a novel therapeutic target in malignancies by bypassing the BCL-2 family of apoptotic regulators. Citation Format: Tresor O Mukiza, Ricardo Enrique-Rodriguez, Amit Budhraja, Lauren Brakefield, Tudor Moldoveanu, Joseph T Opferman. Proteasome inhibitors induce a BAX and BAK independent, non-canonical apoptosis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr A010.