Objective To observe the changes of proliferation and apoptosis of colon cancer cell line treated with oxaliplatin after the downregulation of ERRα and to investigate the mechanism.Methods Colon cancer cell lines Colo-205,HCT-116,SW620 and HT-29 were cultured by adherent cells and in accordance with the given intervention,they were divided into group XCT790-OHP-HCT-116(after oxaliplatin treatment,ERR αinhibitor XCT790 was administered),group siERRα-OHP-HCT-116(after oxaliplatin treatment,siERR α was transfected into HCT-116 cells and downregulated ERR αexpression),oxaliplatin intervention group(group OHP-HCT-116)and the control group(NC group)which was given no intervention.The experiment was divided into siERR αgroup with siERR α transfected with HCT-116 cells,downregulated ERR αexpression and the negative control group(siNC group)transfected with siNegative Control.Using Western blot method and real-time quantitative(qRT)-PCR for the detection of colorectal cancer cell ERRαprotein and mRNA expression,the expression of ERR αwas downregulated by ERR αinhibitors XCT790 and siERR,and apoptosis and proliferation of colon cancer cells were detected by flow cytometry and MTT.Western blot and qRT-PCR were used to detect apoptosis and proliferation-related gene proteins and mRNA expression.Results ERR αand mRNA protein in HCT-116 were higher than those of Colo-205,SW620 and HT-29 cell lines(P<0.05); in the XCT790-OHP-HCT-116 group,the early apoptosis rate was higher than those of the NC group and OHP-HCT-116 group(P<0.05),the survival rate of cell culture in 72 and 96 h in the XCT790-OHP-HCT-116 group was lower than those in the NC group and OHP-HCT-116 group(P<0.05).The siERR α HCT-116 cells transfected with down-regulation of ERR expression,siERR α -OHP-HCT-116 group early apoptosis rate was lower than those of NC group and OHP-HCT-116 group(P<0.05),siERR -OHP-HCT-116 group cells cultured for 72 and 96 h after the survival rate was lower than the NC group and OHP-HCT-116 group(P<0.05);After the downregulation of ERRαby siERR alpha transfected with HCT-116 cells,the early apoptotic rate in the group siERRα-OHP-HCT-116 was lower than that in the group NC and group OHP-HCT-116(P<0.05),the survival rate of the group siERRα-OHP-HCT-116 after 72 and 96 h were lower than those in the group NC and group OHP-HCT-116(P<0.05),siERR α was transfected into HCT-116 cells,compared with the siNC group,YAP1,p73,p63,MDM2, Capase 8,Capase 9 protein in the siERR group decreased(P<0.01),there was no significant difference in the level of mRNA(P>0.05).Conclusion The downregulation the expression of ERRαcan promote colon cancer cell apoptosis,inhibit proliferation,and enhance the killing effect of oxaliplatin on colon cancer cells.