HIF-2α upregulation mediated by hypoxia promotes NAFLD-HCC progression by activating lipid synthesis via the PI3K-AKT-mTOR pathway

Non-alcoholic fatty liver disease (NAFLD) is a relevant risk factor for developing hepatocellular carcinoma (HCC). Steatohepatitic HCC (SH-HCC), characterized by HCC with steatosis, is influenced by lipid metabolism disorders. A hypoxic microenvironment is common in HCC and affects lipid metabolism. However, whether hypoxia-induced HIF-2α upregulation exacerbates lipid accumulation to contribute to SH-HCC progression remains unclear. In this study, we demonstrated that HIF-2α was elevated in tissues from NAFLD-HCC patients and was associated with survival. Under hypoxic conditions, upregulated HIF-2α was accompanied by lipid accumulation and PI3K-AKT-mTOR pathway activation. HIF-2α knockdown (KD) in steatotic HCC ameliorated triglyceride accumulation and steatosis. HIF-2α-KD steatotic HCC showed minimal lipid synthesis in a hypoxic environment, which contributes to a reduction in malignant behaviours. However, treatment with MHY1485 restored these behaviours. STAM mice, a mouse model that develops NAFLD-HCC, exhibit more rapid tumour progression upon exposure to hypoxia. STAM mice treated with INK-128 presented abrogated mTOR expression and tumour progression under hypoxic conditions with lower triglycerides and steatosis. In conclusion, in a hypoxic microenvironment, HIF-2α upregulation promotes steatotic HCC progression by activating lipid synthesis via the PI3K-AKT-mTOR pathway. Therefore, HIF-2α can be a biomarker and target in developing specific therapeutic measures for NAFLD-HCC patients.