Abstract： Objective To study the effects of all-trans-retinoic acid (ATRA) on chemotherapeutics sensibility and expression of Survivin in human LoVo colon cancer cell line, and to provide a theoretical basis for clinical application of ATRA.Methods Flow cytometer (FCM) was used to detect the cell cycle of LoVo colon cancer cell line after treated with various dose of ATRA (10-5 mol/L, 10-6 mol/L and 10-7 mol/L)for 24 h, 48 h, 72 h, 5 d, 9 d and 15 d respectively.The cells were divided into ATRA group (10-6 mol/L)and control group (cultured in routine medium RPMI1640).Meanwhile, each group were divided into subgroups respectively treated with 0 g/L, 2 g/L, 4 g/L and 6 g/L 5-fluorouracil(5-FU) , or with 0 mg/L, 200 mg/L, 400 mg/L and 600 mg/L mitomycin (MMC).MTT assay was used to detect the viability of cells so as to analyze the change in chemotherapeutics sensibility.Drug interactions were analyzed according to the interaction effects.Staining with acridine orange (AO) and ethidium bromide (EB) was used to study the apoptosis in control group(RPMI1640) , ATRA group (10-6 mol/L), 5-FU group (4 g/L), MMC group (400 mg/L), ATRA (10-6 mol/L) + 5-FU (4 g/L) group and ATRA (10-6 mol/L) + MMC (400 mg/L) group.The expression of Survivin in the LoVo cell line was investigated by immunofluorescence technique.Results Compared with the control group, the percentage of cell in Go-G1 phase increased after interference with various doses of ATRA for 24 hours, peaked at 48 h, and gradually decreased afterwards, while the percentage of cells in stages S and G2-M decreased, reach the trough at 48 h, and then increased gradually.Effects of 10-6 mol/L ATRA were most significant at all time spots.Compared with control group, 10-6 mol/L ATRA reduced cell survival rate (P＜0.05),and the survival rates in control subgroups treated with various doses of 5-FU were significantly higher than those in ATRA group (all P＜0.05).In MMC-treated control group, cell survival rate with 200 mg/L MMC was lower than that in ATRA group (0.72±0.02 vs 1.03±0.13, P＜0.05) , while treatment with 400 mg/L or 600 mg/L MMC did not result in lower cell survival compared with the ATRA group (0.52±0.05 vs 0.39±0.02, 0.36±0.02 vs 0.36±0.01, all P>0.05).Positive interactions of 10-6 mol/L ATRA with 5-FU (2 g/L, 4 g/L, 6 g/L) or MMC (200 mg/L, 400 mg/L) were found.Under fluorescence microscope, cells in ATRA + 5-FU group and ATRA + MMC group showed significantly small size, pyknosis and chromatin condensation and formation of apoptotic bodies when compared with control group, ATRA group, 5-FU group and MMC group.Expression of Survivin was inhibited after 10-6 mol/L ATRA treatment for 48 h compared with control group (33.33% vs 27.96% , P＜0.05).Conclusion ATRA enhances the chemosensibility of LoVo colon cancer cell line to 5-FU and MMC,and induces cell apoptosis, potentially through inhibition of Survivin gene expression.