The combination of PF-429242 and chloroquine triggers pH-dependent cell death in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) remains a significant health challenge due to its resistance to conventional treatments and high recurrence rates. Developing novel therapeutic strategies is critical for improving outcomes for HCC patients. In this study, we identified the synergistic anticancer activity of the combination of PF-429242 and chloroquine against HCC cells. Combined treatment exhibited significant cytotoxicity against HCC cell lines, which was not observed with other therapeutic drugs. Notably, this synergistic effect was not mediated through apoptosis or autophagy. Further investigation revealed that the combination induced pH-dependent cell death, distinct from the previously described alkaliptosis. Unlike alkaliptosis, this cell death mechanism did not involve intracellular alkalinization or the IKKβ/NF-κB/CA9 signaling pathway. We also found that the ATP6V0D1/STAT3 axis, implicated in alkaliptosis, was not crucial for PF-429242/chloroquine-induced cell death. Additionally, site-1 protease inhibition by PF-429242 was not responsible for the observed synergistic effect. While the exact mechanism remains unclear, combined treatment induced a necrosis-like morphology and membrane rupture, which could be prevented by acidifying the culture medium. This research highlighted a novel pH-dependent cell death mechanism in HCC cells and suggests potential therapeutic implications for combining PF-429242 and chloroquine in cancer treatment.