Sulforaphene inhibits hepatocellular carcinoma through repressing keratin 8 and activating anoikis

Abstract

Sulforaphene (SFE), a natural isothiocyanate, extracted from radish seeds is forcefully associated with cancer prevention. Nonetheless, the mechanism responsible for SFE-induced cell death is not understood. In the present study, one of the anti-cancer mechanisms of SFE was clarified in hepatocellular carcinoma. SFE exerted cytotoxicity in a concentration-dependent manner and led to apoptotic cell death in HepG2 and SMMC7721. After SFE treatment, a large number of spherical cells were suspended in the medium, and the phenomenon was not associated with EMT. We speculated that the phenomenon should be connected with anoikis. A proteomics study revealed that levels of some proteins including Keratin 8 (KRT8) and Enolase1 (ENO1), etc. were changed in SFE treated cells compared to an untreated control. We had further confirmed that SFE reduced the expression of Keratin 8 and Keratin 18 (K8/18) typically co-expressed as the primary keratin pair with western blotting. What's more, K8/18 loss increased the level of Fas and decreased the level of the inhibitory protein cFLIP. Interestingly, we showed that SFE-treated cells lost cell–matrix interactions without inducing metastasis and increased the apoptosis ratio in a suspension culture model as well as the K8/18 siRNA-treated cell. Taken together, these findings suggest that keratin 8 plays a role in mediating SFE-induced Fas-related death in hepatocellular carcinoma. And our findings present the first evidence that SFE decreased the resistance to anoikis in liver cancer cell lines.