Abstract: Objective To explore the effect of c-Fos on proliferation and apoptosis in colorectal cancer cells HCT-116.Methods C-Fos siRNA was transfected into HCT-116 cell and quantitative real-time PCR was used to measure relative expression of c-Fos.The difference in cell proliferation between control group and RNAi group was detected with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.Propidium iodide(PI)staining and fluorescence-activated cell sorter(FACS)assay were adopted to measure apoptosis in c-Fos knockdown cells after etoposide treatment.Results The relative expression of c-Fos in HCT-116 cells was decreased by about 50% 48 hours after c-Fos siRNA was transfected into the cells.The results of MTT assay indicated that the cell growth of RNAi group was significantly accelerated at 1,2,3,4,5 days,with a time-dependent manner.Twelve hours after the cell apoposis was induced by etoposide(100 μM),the percentage of apoptosis in control group and RNAi group was 27.6±2.07 and 39.1±4.84%,respectively.Conclusion C-Fos could promote cell proliferation and inhibit apoptosis in colorectal cancer cells HCT-116.