The Mechanism Of Autophagy Induced By Sunitinib In Renal Cancer

Sunitinib is a newly approved multi-targeted treatment of tumors oral drug,with significant inhibition of tumor.It exerts anti-tumor activity by specific inhibition of receptor tyrosine kinases,including vascular endothelial growth factor(VEGF)receptor,stem cell factor(SCF)receptor and platelet derived growth factor(PDGF)receptor.Autophagy is a eukaryotic cell physiology in a relatively conservative process,is an important way to maintain the eukaryotic cell homeostasis.Autophagy is a highly conservative physiological process which plays a important role in maintain homeostasis in eukaryotic.Autophagy not only plays an important role in maintaining cellular matter and energy supply,but also contributes to degrade long-lived proteins,remove unfunctional organelles,cells invading pathogens process.Previous studies have shown that sunitinib can induce apoptosis.However,the underlying mechanism of the regulatory role in autophagy and the interplay between autophagy and apoptosis associated with sunitinib remain unclear.For researching the mechanism,we utilize MTS activity and colony formation assay,the result show that sunitinib can cause multiple cell death pathways in 786-O cells.Moreover,sunitinib can promote autophagy by electron microscopy and Western blot,which blunts the caspase-dependent apoptotic process.Akt/mTOR signaling pathway is one of the main signal paths of autophagy,we use immunoblotting to detect the key protein in the signaling pathway.Results show that mTOR and S6K1 phosphorylation upregulation concurring with Akt phosphorylation degradation induced by sunitinib.Using small molecule inhibitors or decreasing the expression of the signaling pathway primarily protein by RNA interference technology can obviously decrease the autophagy induced by sunitinib.These results indicate that: Akt/mTOR signaling pathway involved in the regulation of sunitinib-induced autophagy.Glycolysis is ubiquitous in vivo energy metabolism,it refers to glucose through a series of enzymatic reactions to generate pyruvic acid,while a small amount of ATP release process.Currently,researches between Glycolysis and autophagy are rare.Sunitinib is capable of inhibits the expression of PFKFB3 both in mRNA and protein levels verified by Real-time PCR and immunoblotting,which is the key glycolysis gene.However,with inhibitor of PFKFB3 can promote autophagy and apoptosis induced-sunitinib by the increasing of LC3-II level and PARP-1 cleavage level.Sunitinib increase autophagy continuously by adenoviral transfection,which increase the expression of PFKFB3 in 786-O.Moreover,glycolytic pathway inhibition increase the effection of sunitinib anti-tumor.All above,these data demonstrate that PFKFB3 is involved in sunitinib induced-autophagy and the caspase-dependent apoptotic process.Taken together,the research found that sunitinib induce autophagy through Akt/mTOR signaling pathway,sunitinib induced-autophagy and apoptotic is associated with glycolysis pathway.Further studies of the relationship between glycolytic pathway and autophagy in tumor cells,not only accelerate tumorigenesis development,but also enrich anti-tumor mechanisms of these drugs,which provide a theoretical basis for the further studies on cancer therapy.