Abstract
Autophagy is an intracellular "self-eating" process that is closely related to inflammation and cellular immunity. New studies indicate that autophagy is also involved in tumor suppression. The anti-inflammatory cytokine interleukin-37 (IL-37) has been shown to have tumor-suppressive abilities in hepatocellular carcinoma (HCC). Notably, autophagy appears to play a dual role in the development of HCC and may be involved in both tumorigenesis and tumor suppression. However, the potential role of IL-37 in autophagy is currently unknown. In this study, we investigated the effect of IL-37 on autophagy in multiple HCC cell lines. In doing so, we found that IL-37 inhibits proliferation in HCC cells and also induces autophagy and apoptosis in the SMMC-7721 and Huh-7 cell lines. Further experiments revealed that IL-37 treatment reduced the levels of phosphorylated protein kinase B (p-AKT), phosphorylated mammalian target of rapamycin (p-mTOR), phosphorylated p70 ribosomal protein s6 kinase (p-p70S6K) and phosphorylated 4E-binding protein 1 (4E-BP1). Moreover, treatment with an AKT agonist, insulin-like growth factor 1 (IGF-1), reversed these IL-37-mediated effects on autophagy, and treatment with an phosphoinositide-3-kinase (PI3K)/AKT inhibitor, LY294002, mimicked the effects of IL-37. Taken together, these results indicate that IL-37 regulates autophagy in SMMC-7721 and Huh-7 cells via inhibition of the PI3K/AKT/mTOR signaling pathway.