Targeting GPX4 to Overcome Sorafenib Resistance of Human Hepatocellular Carcinoma by Inducing Ferroptosis.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death. Sorafenib, a multikinase inhibitor, has been approved as a first-line systemic therapeutic for HCC patients based on the results of two large clinical trials, in which sorafenib significantly increased life expectancy of patients with Child Pugh A advanced stage of liver cancer, no matter which races they were or whether being infected with hepatitis B or C virus; however, its efficacy is compromised by the resistance of the tumor cells. By using integrative bioinformatics analysis, we identified ferroptosis as a candidate to modulate sorafenib-resistant HCC. Ferroptosis is a novel, iron-dependent, non-apoptotic regulated cell death with characteristics of impaired lipid peroxide repair, redox active iron, and the oxidation of polyunsaturated fatty acids. Here, glutathione peroxidase 4 (GPX4) was further identified as a favorable prognostic factor in cancer survival by analyzing data repositories. Compared to the parental human HCC Huh7 cells, lower expression of GPX4, dysregulated iron homeostasis, and higher expression of acyl-CoA synthetase long-chain family member 4 were observed in sorafenib-resistant Huh7R cells, and the Huh7R cells exhibited higher sensitivity to ferroptosis induction exerted by RSL3, a GPX4 inhibitor. The RSL3-induced ferroptosis was attenuated by lysosomal blocker bafilomycin A1, indicating that lysosomal degradation of ferritin may confer sensitivity to GPX4-inactivation-induced ferroptosis by providing accessible iron. Taken together, our findings demonstrate that GPX4-inactivation-induced ferroptosis is a promising and effective treatment option capable of overcoming sorafenib resistance in liver cancer, and our novel gene expression-screening platform via integrated analysis of differentially expressed genes and pathways allows efficient identification of therapeutic strategies.