Acid ceramidase inhibition enhances BCL-2 targeting in venetoclax-resistant acute myeloid leukemia via a cytotoxic integrated stress response

Resistance to combination regimens containing the BCL-2 inhibitor venetoclax in acute myeloid leukemia (AML) is a growing clinical challenge for this extensively utilized agent. We previously established the anti-leukemic properties of ceramide, a tumor-suppressive sphingolipid, in AML and demonstrated that upregulated expression of acid ceramidase (AC), a ceramide-neutralizing enzyme, supported leukemic survival and resistance to BH3 mimetics. Here, we report the anti-leukemic efficacy and mechanisms of co-targeting AC and BCL-2 in venetoclax-resistant AML. Analysis of the BeatAML dataset revealed a positive relationship between increased AC gene expression and venetoclax resistance. Targeting AC enhanced single-agent venetoclax cytotoxicity and the venetoclax + cytarabine combination in AML cell lines with primary or acquired venetoclax resistance. SACLAC + venetoclax was equipotent to the combination of venetoclax + cytarabine at reducing cell viability when evaluated ex vivo across a cohort of 71 primary AML patient samples. Mechanistically, SACLAC + venetoclax increased ceramide to levels that trigger a cytotoxic integrated stress response (ISR), ISR-mediated NOXA protein upregulation, mitochondrial dysregulation, and caspase-dependent cell death. Collectively, these data demonstrate the efficacy of co-targeting AC and BCL-2 in AML and rationalize targeting AC as a therapeutic approach to overcome venetoclax resistance.