Effects of silencing enhancer of zeste homolog 2 on oxaliplatin chemosensitivity of colon cancer HT29 cells
Objective To investigate the effects of enhancer of zeste homolog 2(EZH2)on the chemosensitivity of colon cancer HT29 cells treated by oxaliplatin and mechanisms.Methods Real-time quantitative polymerase chain reaction(Real-time PCR)was used to detect the relative expression levels of mRNA in the transfection group[transfected with EZH2 small interfering RNA(siRNA)],blank control group(transfected with Control siRNA),and negative control group after 24 h of transfection of HT29 cells with EZH2 siRNA,and the relative expression of EZH2 protein was detected by Western blotting.Different concentrations of oxaliplatin were used to treat transfected cells for 24 h,and the cell viability was detected by methyl thiazolyl tetrazolium(MTT)assay at 48 h after treatment.The half-maximal inhibitory concentra-tion(IC50)was calculated.The cells transfected for 24 h were treated with 50 μg/μL of oxaliplatin,and cell apoptosis was detected by flow cytometry at 48 h after treatment.The relative expression levels of Survivin and cyclooxygenase-2(COX-2)proteins were detected by Western blotting.One-way ANOVA and LSD-t test were used to compare data between groups.Results The relative expression level of EZH2 mRNA in EZH2 siRNA group was lower than that in control group and control siRNA group(105.1±24.3 vs.545.9±88.6,558.4±60.4,F=496.2,P<0.05).The relative expression of EZH2 protein in EZH2 siRNA group was lower than that in blank control group and control siRNA group(75.4±10.9 vs.395.8±29.7,391.7±41.7,F=1 109.6,P<0.05).After oxaliplatin treatment with different concen-trations(0,6.25,12.5,25,50,100 μg/μL),the cell survival rate in EZH2 siRNA group was lower than that in blank control group and control siRNA group,and the IC50 of EZH2 siRNA group was lower than that in blank control group and control siRNA group(26.94 µg/µL vs.63.24,56.74 µg/μL).The apoptosis rate of 50 μg/μL oxaliplatin treated in EZH2 siRNA group was lower than that in control group and control siRNA group(45.4±4.9 vs.7.1±1.6,6.8±2.0,F=95.5,P<0.05).The relative ex-pression of Survivin and COX-2 protein(43.2±8.8,47.0±10.3)in EZH2 siRNA group was lower than that in blank control group and control siRNA group(43.2±8.8,47.0±10.3 vs.252.5±31.9,248.5±23.6,F=790.2,P<0.05;43.2±8.8,47.0±10.3 vs.246.0±7.0,264.8±26.0,F=1 558.1,P<0.05).Conclusion Silencing EZH2 expression by siRNA can improve the chemosensitivity of colon cancer HT29 cells to oxaliplatin by promoting apoptosis.