Dual Targeting ACK1 And KIT Inhibits Tumor Growth In Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor(GIST)is the most common malignant tumor of gastrointestinal tract.Various studies showed that oncogene KIT(80%)and PDGFRA(5%)mutation and abnormal activation are the main factors for the occurrence and progression of GIST.At present,KIT has become an important tumor biomarker for the diagnosis of GIST.Imatinib(IM),a specific KIT/PDGFRA inhibitor,become a firstline drug for the treatment of GIST.Clinical studies have demonstrated that IM has a remarkable benefit for GIST patients.However,most of the patients eventually acquired resistance to IM after treatment with drugs for two years.The second-line drug sunitinib has a good effect on IM resistant GISTs,but it has badly clinical side effects.Therefore,it is urgent to solve the problem of GIST IM resistance.ACK1(Activated Cdc42-associated Kinase 1)is a member of the non-receptor tyrosine kinase family.Numerous studies have reported that ACK1 has abnormal expression and activation in many kinds of tumors,such as prostate cancer,hepatocellular carcinoma,breast cancer,stomach cancer,pancreatic cancer and so on.Therefore,in the present project,we focused on studying the expression,activation and biological function of ACK1 and the additive effects of dual targeting ACK1 and KIT on GIST signaling pathway,proliferation and metastasis.The results showed that ACK1 overexpressed in GIST cell lines and tumor samples.In addition,it was observed that ACK1 strongly phosphorylated in IM sensitive GIST cell lines(GIST882 and GIST-T1)and IM resistant GIST cell line(GIST 430)by Co-immunoprecipitation(Co-IP).However,there is no interaction between ACK1 and KIT proteins.Inhibition of KIT(IM and Sunitinib)did not reduce ACK1 phosphorylation,and inhibition of ACK1(AIM-100)little affected KIT activation.Treatment with AIM-100 inhibited ACK1 activation in a dose-dependent manner,which further verified that there is no interaction between ACK1 and KIT.MTT assay showed that ACK1 inactivation only partially inhibited the growth of GIST cells.However,AIM-100 can significantly inhibit the wound healing in GIST cells,indicating that ACK1 regulates the migration of GIST cells.Dual targeting ACK1(AIM-100)and KIT(IM)resulted in that the inactivation of ACK1,KIT and downstream intermediates including AKT,MAPK and S6(mTOR),in IM sensitive and IM resistant GIST cell lines.As compared to the inhibition effect of KIT(IM)in GIST cell lines,the combination of AIM-100 and IM had additive inhibition effects on the cell growth,migration,invasion,cell cycle and apoptosis in GIST430,but not in GISTT1 and GIST882 cells.Although it has been widely recognized that ACK1 is a oncoprotein,the activation and function of ACK1 in GIST should be studied in depth.In this paper,we focused on the mechanism and function of ACK1 in GIST,and also clarified that co-targeting inhibition of ACK1 and KIT may provide a new therapeutic strategy and method for treatment of IM resistant GISTs.