Functional Role of NOXA in Hypoxia-Mediated PD-L1 Inhibitor Response in Hepatocellular Carcinoma

Hypoxia is a crucial characteristic of hepatocellular carcinoma (HCC) and contributes to immune resistance by upregulating PD-L1 and recruiting immunosuppressive cells. However, the molecular mechanisms of hypoxia-induced immunotherapy resistance are still unclear. The hypoxia-related immunotherapy response (IRH) genes were identified and developed a hypoxia risk score model to predict patient survival. The model was validated using GSE233802 and EGAD00001008128 datasets. A hypoxia-induced drug-resistant (HepG2-R) cell line was established by co-culturing HepG2 cells with Jurkat T cells under CoCl₂-induced hypoxia and PD-L1 inhibitor administration. The effect of NOXA knockdown on the apoptosis of HepG2-R cells under the same co-culture conditions was examined. The hypoxia risk score model including NOXA effectively stratified patients based on risk and demonstrated excellent survival predictive ability (p = 0.0236). Prolonged exposure to hypoxia (48h) in HepG2 cells significantly led to the increased hypoxia risk score (p < 0.02). The establishment of the HepG2-R cell line showed that prolonged hypoxia reduced cancer cell apoptosis, which implies potential treatment resistance. Under hypoxia and PD-L1 inhibitor treatment, NOXA knockdown increased the survival rate of HepG2-R cells and reduced early and late apoptosis. This indicates that NOXA plays a crucial role in apoptosis regulation and immune response in hypoxic tumors. NOXA knockdown significantly reduces apoptosis in immunotherapy-resistant cells induced by hypoxia. These findings provide important evidence that targeting NOXA may enhance immunotherapy efficacy and help overcome treatment resistance in HCC, highlighting its potential as a therapeutic target.