Down Regulation Of IQGAP1 Inhibits Epithelial-mesenchymal Transition Via The HIF1?/VEGF-A Signaling Pathway In Gastric Cancer

Objective:To confirm the IQ motif containing GTPase activating protein 1?IQGAP1?expression in gastric adenocarcinoma tissues in gastric cancer patients using UALCAN and Human Protein Atlas databases.To detect the protein expression of IQGAP1 in gastric cancer cell lines and the gastric epithelial cell,and to identify the effects of down regulation of IQGAP1 on the migration and epithelial mesenchymal transition?EMT?in gastric cancer cells,and to investigate the possible molecular mechanism of the role of knockdown of IQGAP1 in EMT in gastric cancer cells.Methods:1.UALCAN and Human Protein Atlas databases were used to analysis IQGAP1expression in gastric cancer.IQGAP1 expression in gastric epithelial cell?GES1?and gastric cancer cell lines?SGC7901,HGC27,and MGC803?was detected by western blotting.2.The IQGAP1 siRNA was tranfected into HGC27 and MGC803 cells,that express higher level of IQGAP1,scramble siRNA as a control.And the IQGAP1 expression was detected by Western blot.Then transwell and wound healing experiment was applied to detect the effect of IQGAP1 on cellular migration and EMT.The EMT-related proteins were investigated following IQGAP1 siRNA treatment in HGC27 and MGC803 cells by Western blot.3.The expression of vascular endothelial growth factor-A?VEGF-A?in SGC7901,HGC27,MGC803 and GES1 was detected by Western blot.And we identified the VEGF-A expression when IQGAP1 was silenced in HGC27 and MGC803 cells.VEGF-A secretion from gastric cancer cells subjected to different treatments was measured by an ELISA.4.After transfection with siRNA,the cells were incubated with different concentrations of CoCl₂.The expression of hypoxia-inducible factors 1??HIF1??and VEGF-A in cells was investigated by Western blot.The secretion of VEGF-A from different treated-gastric cancer cells groups was also measured by ELISA.Nuclear/cytoplasmic fractionation was used to measure the subcellular localization of HIF1?in the gastric cancer cells.Results:1.We found that compared with the mRNA level of IQGAP1 in normal tissues,it was higher in gastric cancer tissues with individual cancer stages by UALCAN database.The Human Protein Atlas database demonstrated IQGAP1 was also expressed higher in the gastric adenocarcinoma specimen than the normal one.The IQGAP1 expression was markedly increased in the gastric cancer cell lines SGC7901,MGC803,HGC27,contrasted with the GES1.2.We found that the IQGAP1 expression was obviously inhibited under the treatment of IQGAP1 siRNA in the HGC27 and MGC803 cells.Down regulation of IQGAP1expression decreased migration in gastric cancer cells.In IQGAP1 siRNA group,the epithelial E-cadherin expression was increased,meanwhile the mesenchymal proteins expression,including Vimentin,Snail,Slug,?-catenin,and N-cadherin,was reduced comparing with the scrambled siRNA group.3.VEGF-A was upregulated in gastric cancer cells with IQGAP1 higher expressed.VEGF-A expression was decreased when IQGAP1 was silenced.Knockdown of IQGAP1 repressed the VEGF-A level in cultural supernatant.4.Hypoxia-induced HIF1?and VEGF-A expression were reduced in the gastric cancer cells with IQGAP1 knockdown.Nuclear/cytoplasmic fractionation indicated that IQGAP1 silence inhibited the translocation of HIF1?to the nuclear.Conclusion:IQGAP1 was upregulated in human gastric cancer specimens and cells.Down regulation of IQGAP1 expression decreased migration and EMT via the impairing the translocation of HIF1?to nuclear and VEGF-A expression and secretion in gastric cancer cells.