Abstract 2862: The TNF-α/ROS/HIF-1-mediated upregulation of FoxM1 expression promotes proliferation, resistance to apoptosis and indicates poor prognosis in hepatocellular carcinoma.

Abstract

Abstract Background and aims: Inflammatory microenvironment plays a critical role in promoting hepatocellular carcinoma (HCC) progression. Among the factors secreted by cancer-associated inflammatory cells, tumor necrosis factor-alpha (TNF-α) has been identified as a master regulator of inflammation and a potential mediator in inflammation-related cancers. Forkhead box M1 (FoxM1) is a key cell cycle regulator of the transition from the G1 to the S phase and the progression to mitosis. We previously reported that FoxM1 promotes metastasis and indicates poor prognosis in HCC. However, the critical regulatory mechanism linking TNF-α to FoxM1 activation in inflammation-induced HCC progression remains unclear. In this study, we aim to investigate the mechanism by which FoxM1 is regulated by TNF-α, and the potential role of FoxM1 in inflammation-associated HCC. Methods: Luciferase reporter, chromatin immunoprecipitation, and electrophoretic mobility shift assays were used to measure the transcriptional regulation of FoxM1 promoter by TNF-α. The clinical significance of TNF-α/ROS/HIF-1/FoxM1 pathway in a cohort of 406 HCC patients who underwent curative resection was assessed by Kaplan-Meier analysis and Multivariate Cox proportional hazards model. Results: TNF-α induced FoxM1 expression and transactivated its promoter activity in hepatoma cells. Serial 5′ deletion and site-directed mutagenesis revealed that the induction of FoxM1 expression by TNF-α was dependent upon the HIF1-1 and HIF1-3/4 binding sites within the FoxM1 promoter. Furthermore, at the transcriptional level, the stabilization of HIF-1α via reactive oxygen species (ROS) generation led to the binding of HIF-1α to the FoxM1 promoter and resulted in increased FoxM1 expression. The inhibition of both HIF-1α expression and ROS generation significantly decreased TNF-α-induced FoxM1 expression. Consequently, the upregulation of FoxM1 promoted the proliferation of hepatoma cells and enhanced their resistance to TNF-α-induced apoptosis, whereas downregulation of FoxM1 dramatically attenuated these effects. TNF-α expression was positively correlated with HIF-1α and FoxM1 expression in human HCC tissues. Patients with positive coexpression of TNF-α and FoxM1 had shorter overall survival and higher recurrence rates than those with negative coexpression of TNF-α and FoxM1. Simarily, patients with HIF-1(+)/FoxM1(+) expression had shorter overall survival and higher recurrence rates than those with HIF-1(-)/FoxM1(-) expression. Conclusions: We report a new molecular mechanism by which FoxM1 expression is regulated by the TNF-α/ROS/HIF-1 pathway, and this mechanism results in the proliferation of hepatoma cells and their resistance to apoptosis. Thus, TNF-α/ROS/HIF-1/FoxM1 pathway may provide a target for clinical intervention in HCC. Citation Format: Limin Xia, Daiming Fan, Yongzhan Nie, Kaichun Wu. The TNF-α/ROS/HIF-1-mediated upregulation of FoxM1 expression promotes proliferation, resistance to apoptosis and indicates poor prognosis in hepatocellular carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2862. doi:10.1158/1538-7445.AM2013-2862 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.