Tumor necrosis factor-α attenuates starvation-induced apoptosis through upregulation of ferritin heavy chain in hepatocellular carcinoma cells

Xingrui Kou,Qingmin Fan,Guofeng Yu,Fei Ye,Zhipeng Han,Lixin Wei,Qiudong Zhao,Xue Zhao,Lu Gao,Weijie Deng,Rong Li,Kai Sun,Mengchao Wu,Yingying Jing

doi:10.1186/1471-2407-13-438

Abstract

BackgroundTumor microenviroment is characteristic of inflammation, ischemia and starvation of nutrient. TNF-α, which is an extraordinarily pleiotropic cytokine, could be an endogenous tumor promoter in some tumor types. The basic objective of this study was to investigate the effects of TNF-α on the cell viability and apoptosis of hepatocellular carcinoma cells under serum starvation, and to identify the molecular mechanisms involved.MethodsFor this purpose, five different concentrations of TNF-α and two different serum settings (serum-cultured and serum-deprived) were used to investigate the effects of TNF-α on the cell viability and apoptosis of Hep3B and SMMC-7721 cells.ResultsTNF-α (10 ng/ml) attenuated serum starvation-induced apoptosis of hepatocellular carcinoma cells, and autophagy conferred this process. BAY11-7082, a specific inhibitor of NF-κB, reversed the suppression of serum starvation-induced apoptosis by TNF-α. Moreover, TNF-α-induced NF-κB transactivation was suppressed by autophagy inhibitor 3-MA. In addition, TNF-α up-regulated Ferritin heavy chain (FHC) transiently by NF-κB activation and FHC levels were correlated with the TNF-α-induced protection against serum starvation-mediated apoptosis of hepatocellular carcinoma cells. Furthermore, FHC-mediated inhibition of apoptosis depended on suppressing ROS accumulation.ConclusionsOur findings suggested that autophagy conferred the TNF-α protection against serum starvation-mediated apoptosis of hepatocellular carcinoma cells, the mechanism involved with the activation of the TNF-α/ NF-κB /FHC signaling pathway.

Highlights

Tumor microenviroment is characteristic of inflammation, ischemia and starvation of nutrient
We have previously shown that Hep3B and SMMC-7721 cells are resistant to serum starvationinduced cell death due to activation of Nuclear factor-κB (NF-κB) by Tumor necrosis factor-α (TNF-α)
We show that serum starvation induced significant apoptosis in the Hep3B and SMMC-7721 cells, and this cell death was attenuated by pre-incubation of TNF-α via suppression of caspase activation and coincident with Ferritin heavy chain up-regulation

Summary

Introduction

Tumor microenviroment is characteristic of inflammation, ischemia and starvation of nutrient. TNF-αmediated the killing of certain cancer cells has been demonstrated [3,4]. Recent studies have shown that NF-κB-regulated FHC can inhibit caspase activity and can prevent TNF-α-induced apoptosis [13]. Additional studies have shown that suppression of IAP genes sensitized endothelial cells to TNF-α-induced apoptosis. We have previously shown that Hep3B and SMMC-7721 cells are resistant to serum starvationinduced cell death due to activation of NF-κB by TNF-α. We show that serum starvation induced significant apoptosis in the Hep3B and SMMC-7721 cells, and this cell death was attenuated by pre-incubation of TNF-α via suppression of caspase activation and coincident with Ferritin heavy chain up-regulation. Inhibition of NF-κB transactivation using a pharmacological inhibitor of IKK abrogated the TNF-α-induced protection against serum starvation killing. We demonstrate that temporal TNF-α-mediated suppression of serum starvation-mediated apoptosis may be due to the transient up-regulation of FHC by TNF-α

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