NRF2/xCT-Mediated Antioxidant Adaptation Attenuates Apoptosis Induced by ASCT2 Inhibition in Prostate Cancer

Abstract

Glutamine supports biosynthesis and redox homeostasis in cancer cells. The glutamine transporter ASCT2 is highly expressed in prostate cancer and is associated with higher Gleason grade. Although ASCT2 inhibition induces reactive oxygen species (ROS) accumulation and apoptosis, cancer cells may activate antioxidant adaptive mechanisms that limit therapeutic efficacy. Here, we identified an NRF2/xCT-dependent redox-adaptive response following ASCT2 inhibition in prostate cancer. Mechanistically, ASCT2 inhibition induced ROS accumulation, promoted nuclear translocation of NRF2, and upregulated xCT together with other NRF2-associated antioxidant genes. Functional redox analysis showed that ASCT2 inhibition reduced glutathione-dependent redox capacity, whereas combined ASCT2 and xCT inhibition further increased GSSG accumulation and markedly decreased GSH levels and the GSH/GSSG ratio. These fin\dings were further validated in C4-2 cells as an additional prostate cancer model. Cell death discrimination assays showed that combined ASCT2 and xCT inhibition induced lipid peroxidation that was partially rescued by ferrostatin-1, whereas z-VAD produced a stronger rescue effect and Annexin V/PI staining confirmed prominent apoptotic cell death. In castrated 22Rv1 xenograft models, combined treatment with V-9302 and erastin produced the strongest inhibition of tumor growth without significant body weight loss during treatment. Collectively, these findings demonstrate that NRF2/xCT-mediated residual glutathione redox buffering functions as an adaptive survival mechanism following ASCT2 inhibition and provide a mechanistic rationale for combined targeting of ASCT2 and xCT to overcome redox-adaptive resistance in prostate cancer.