Interferon-gamma induces autophagy with growth inhibition and cell death in human hepatocellular carcinoma (HCC) cells through interferon-regulatory factor-1 (IRF-1)

Interferon-gamma (IFN-gamma) is a pleiotropic cytokine with immunomodulatory, anti-viral, and anti-proliferative effects. In this study, we examined the effects of IFN-gamma on autophagy and cell growth in human hepatocellular carcinoma (HCC) cells. IFN-gamma inhibited cell growth of Huh7 cells with non-apoptotic cell death. IFN-gamma induced autophagosome formation and conversion/turnover of microtubule associated protein 1 light chain 3 (LC3) protein. Furthermore, overexpression of IRF-1 also induced autophagy in Huh7 cells. Silencing IRF-1 expression with target small hairpin RNA blocked autophagy induced by IFN-gamma. Silencing of the autophagy signals Beclin-1 or Atg5 attenuated the inhibitory effect of IFN-gamma on Huh7 cells with decreased cell death. Additionally, IFN-gamma activated autophagy in freshly cultured human HCC cells. Together, these findings show that IFN-gamma induces autophagy through IRF-1 signaling pathway and the induction of autophagy contributes to the growth-inhibitory effect of IFN-gamma with cell death in human liver cancer cells. (C) 2011 Elsevier Ireland Ltd. All rights reserved.