Propionate promotes ferroptosis and apoptosis through mitophagy and ACSL4-mediated ferroptosis elicits anti-leukemia immunity

Short-chain fatty acids (SCFAs), particularly propionate and butyrate, have been reported in many cancers. However, the relationship between propionate and acute myeloid leukemia (AML) remains unclear. Additionally, Acyl-CoA synthetase long chain family member 4 (ACSL4) has been reported to regulate immunity in solid tumors, but there are still many gaps to be filled in AML. Here, we discovered the underlying mechanism of propionate and ACSL4-mediated ferroptosis for immunotherapy. Our results showed that the level of propionate in the AML patients' feces was decreased, which was correlated to gut microbiota dysbiosis. Moreover, we demonstrated that propionate suppressed AML progression both in vivo and in vitro. In mechanism, propionate induced AML cells apoptosis and ferroptosis. The imbalance of reactive oxygen species (ROS) and redox homeostasis induced by propionate caused mitochondrial fission and mitophagy, which enhanced ferroptosis and apoptosis. Furthermore, ACSL4-mediated ferroptosis caused by propionate increased the immunogenicity of AML cells, induced the release of damage-associated molecular patterns (DAMPs), and promoted the maturation of dendritic cells (DCs). The increased level of immunogenicity due to ferroptosis enable propionate-based whole-cell vaccines to activate immunity, thus further facilitating effective killing of AML cells. Collectively, our study uncovers a crucial role for propionate suppresses AML progression by inducing ferroptosis and the potential mechanisms of ACSL4-mediated ferroptosis in the regulation of AML immunity.