Sodium butyrate increases USP5-mediated ubiquitination degradation of GPX4 and enhances anti-cancer efficacy of anti-PD-1 antibody

accumulation, reactive oxygen species (ROS) generation, and malondialdehyde (MDA) production. Notably, these effects are effectively mitigated by Ferrostatin-1 (Fer-1), underscoring the ferroptosis-inducing capacity of NaBu. Mechanistically, NaBu exerts its action by diminishing the level of ubiquitin-specific protease 5 (USP5), which subsequently leads to the ubiquitination and destabilization of glutathione peroxidase 4 (GPX4), a crucial suppressor in ferroptosis. In a preclinical setting, NaBu significantly inhibits tumor xenograft growth in nude mice, highlighting its in vivo efficacy. When paired with an anti-programmed death 1 (PD-1) antibody, NaBu exhibits a potent synergistic antitumor effect, suggesting a potential role in enhancing immunotherapy response. Collectively, our results underscore the potential of NaBu as a novel therapeutic agent for HCC, through its ability to inhibit USP5 and indirectly downregulate GPX4, thereby stimulating ferroptosis.