Aryl hydrocarbon receptor-dependent lipid droplet accumulation supports redox homeostasis in hypoxia-induced PCa cells.

Abstract

Tumor cells in hypoxic environments generate large amounts of reactive oxygen species (ROS), and lipid droplets (LDs) play an essential role in maintaining redox homeostasis under these harsh conditions. The aryl hydrocarbon receptor (AhR) is a member of the basic helix-loop-helix (bHLH) transcription factor superfamily that is closely associated with malignant tumor phenotypes. AhR has been shown to drive prostate cancer (PCa) cell growth, but the specific mechanistic basis for this effect remains unclear. In this study, we used a hypoxia-induced PC-3M cell model to explore the molecular pathways through which AhR promotes PCa progression. Significant LD accumulation was observed in hypoxia-induced PC-3M cells, and AhR knockdown inhibited LD formation, supporting a potential role for AhR in this process. AhR-dependent LD formation enhanced the ability of PC-3M cells to adapt to oxidative stress, as evidenced by reduced ROS production and a decreased NADP/NADPH ratio. AhR-dependent LD formation also alleviated mitochondrial dysfunction, as evidenced by increased membrane potential, reduced cell apoptosis, and decreased levels of active caspase-3. Treatment with the LD inhibitor PF-06424439 reversed these protective effects, as did DGAT2 knockdown. Mechanistically, AhR was found to activate the PI3K/AKT pathway through RAB3D, thereby promoting LD formation. Co-immunoprecipitation (Co-IP) experiments demonstrated that CYLD inhibits AhR activity by eliminating the K63-linked ubiquitination of AhR. In summary, under hypoxic conditions, these results indicate that AhR protects PCa cells from ROS-associated toxicity through the induction of LD formation.