Autophagy Promotes Hepatocellular Carcinoma Cell Invasion Through Activation Of Epithelial-mesenchymal Transition

Aim: To elucidate the mechanism by which autophagy affects invasion ofhepatocellular carcinoma cell.Methods: Inductions of autophagic activities of cells of HCC cell lines, HepG2andBEL7402, were achieved by starvation, which means incubating HepG2andBEL7402cells in HBSS for6h, and the effect of starvation on the invasiveness ofHCC cells were evaluated with Transwell method. Expressions of epithelial markers,mesenchymal marker and MMP-9of HCC cells treated under different conditionswere assessed with Western blotting and immunofluorescence to evaluate the role forEMT in autophagy-induced invasion. Chloroquine and siRNA targeting Atg3andAtg7were used as inhibitors of autophagy. Exogenous recombinant TGF-β1and SIS3were used to activate and block signaling of TGF-β/Smad3, respectively. Changes ininvasiveness and EMT markers of HCC cells induced by modulations of activities ofautophagy and(or) TGF-β/Smad3signaling activity are also observed.Results: Autophagic activities and invasiveness of HCC cells were effectivelyinduced by starvation, which was also accompanied by down-regulations of epithelialmarkers and up-regulations of mesenchymal markers. And the changes mentionedabove were inhibited by transfections of Atg3and Atg7targeting siRNA andadministration of chloroquine. The blockades of starvation-induced increase ofinvasiveness and changes in EMT markers of autophagy-deficient HCC cells wererescued by administration of exogenous recombinant TGF-β1. Starvation-inducedincreases of invasiveness, down-regulations of epithelial markers and up-regulations of mesenchymal markers of HCC cells were all inhibited by SIS3, an inhibitor ofTGF-β/Smad3signaling, while the autophagic activities of HCC cells were left intact.Conclusion: Autophagy can promote invasion of HCC cells through activation ofepithelial-mesenchymal transition in a TGF-β/Smad3signaling-dependent manner.