Impact of TP53-induced glycolysis and apoptosis regulator on malignant activity and resistance to ferroptosis in intrahepatic cholangiocarcinoma.

TP53-induced glycolysis and apoptosis regulator (TIGAR) is an important gene that encodes a regulatory enzyme of glycolysis and reactive oxygen species (ROS) detoxification and is associated with worse prognosis in various cancers. Ferroptosis is a recently identified type of programmed cell death that is triggered by iron-dependent lipid peroxidation. There are no reports on the prognostic impact of TIGAR on intrahepatic cholangiocarcinoma (ICC), and its role in ferroptosis is unclear. Ninety ICC patients who had undergone hepatic resection were enrolled. Immunohistochemical staining for TIGAR was performed. The regulation of malignant activity by TIGAR and the association between ferroptosis and TIGAR were investigated in vitro. Twenty-two (24.4%) patients were categorized into TIGAR-high and -low groups by immunohistochemical staining. There were no noticeable differences in background factors between the two groups, but TIGAR positivity was an independent prognostic factor in disease-free survival (hazard ratio [HR], 2.00; 95% confidence interval [CI], 1.04-3.85, p = 0.0378) and overall survival (HR, 2.10; 95% CI, 1.03-4.30, p = 0.00422) in a multivariate analysis. In vitro, TIGAR knockdown (KD) decreased cell motility (cell proliferation/migration/invasion/colony-forming capabilities) and elevated ROS and lipid peroxidation. This indicated that TIGAR KD induced ferroptosis. TIGAR KD-induced ferroptosis was suppressed using liproxstatin. TIGAR KD decreased the expression of glutathione peroxidase 4, known as factor-suppressing ferroptosis. The combination of TIGAR KD with cisplatin significantly induced more ferroptosis. In conclusion, TIGAR is associated with poor outcomes in ICC patients and resistance to ferroptosis.