Scaffold Protein IQGAP1 Regulates Cisplatin Resistance Of Gastric Cancer Through Epithelial-mesenchymal Transition(EMT)

Objective:The present study was performed to investigate the regulation of IQGAP1 in EMT in SGC7901 cells and SGC7901/DDP cells and their involvement in cisplatin sensitivity,for the purpose of a new treatment strategy for drug resistance of gastric cancer.Methods:1.Using CCK-8 assay assessed the half maximal inhibitory concentration(IC50)of DDP in SGC7901 and SGC7901/DDP cells.2.Western Blot was used to detect the expression of EMT-related proteins E-cadherin,N-cadherin,Snail,Vimentin and Slug in SGC7901 and SGC7901/DDP cells.Transwell migration and invasion assays evaluated the migration and invasion abilities of SGC7901 and SGC7901/DDP cells.3.We analyzed IQGAP1 expression in SGC7901 and SGC7901/DDP cells by western Blot.4.Transfecting plasmid pFlag-IQGAP1 in SGC7901 and transfecting small interfering RNA(siRNA)against IQGAP1 in SGC7901/DDP cell,then we examined the effect of transfection by Western Blot.5.The expression of EMT-related proteins were detected by Western Blot after transfection in SGC7901 and SGC7901/DDP cells.The migration and invasion abilities of SGC7901 and SGC7901/DDP cells after transfection were evaluated by transwell migration and invasion assays.6.The IC50 of cisplatin in SGC7901 and SGC7901/DDP cells after transfection was detected by CCK-8 assay.The expression of MRP1,MDR1 and apoptosis-related proteins Bcl-2 and Bax were detected by Western Blot after transfection in SGC7901 and SGC7901/DDP cells.The apoptosis rate of SGC7901 and SGC7901/DDP cells after treatment of DDP was detected by flow cytometry assay.Results:1.The IC50 of cisplatin in SGC790/DDP cells was 4.9 times than that in SGC7901 cells.2.E-cadherin protein was relatively higher in SGC7901 cells,which was relatively lower in SGC7901/DDP cells;N-cadherin,Snail,Vimentin and Slug proteins were relatively lower in SGC7901 cells,which were relatively higher in SGC7901/DDP cells.SGC7901/DDP cells had increased migration and invasion abilities than SGC7901 cells.3.IQGAP1 protein was higher in SGC7901/DDP cells comparing with SGC7901 cells.4.Western blot results showed that transfection of pFlag-IQGAP1 in SGC7901 and transfection of IQGAP1-siRNA in SGC7901/DDP were effective.5.The expression of E-cadherin protein was decreased and the expression of N-cadherin,Snail,Vimentin and Slug proteins were increased in SGC7901 after transfecting plasmid pFlag-IQGAP1.The migration and invasion abilities of SGC7901 were enhanced after transfecting plasmid pFlag-IQGAP1.The expression of E-cadherin protein was increased and the expression of N-cadherin,Snail,Vimentin and Slug proteins were decreased in SGC7901/DDP after transfecting IQGAP1-siRNA.The migration and invasion abilities of SGC7901/DDP were weakened after transfecting IQGAP1-siRNA.6.After transfecting plasmid pFlag-IQGAP1 in SGC7901,the IC50 of cisplatin and the expression of MRP1,MDR1,Bcl-2 proteins were increased,while the expression of Bax protein and apoptosis rate were decreased.After transfecting IQGAP1-siRNA in SGC7901/DDP,the IC50 of cisplatin and the expression of MRP1,MDR1,Bcl-2 proteins were decreased,while the expression of Bax protein and apoptosis rate were increased.Conclusions:1.Human gastric cancer cisplatin-resistant cell line(SGC7901/DDP)showed overexpression of IQGAP1 which involved in the occurance of EMT during the process of drug resistance.2.IQGAP1 may affect the sensitivity of gastric cancer to cisplatin through EMT.