Abstract: Objective: To expore the effects of cucurbitacin B(CUB) combined with oxaliplatin(OXA)on the proliferation and apoptosis of human colon cancer SW480 cells, and to clarify their mechanisms. Methods: The SW480 cells were divided into control group, 10,20, and 40 μmol·L^-1 CUB groups, OXA group(100 μmol·L^-1) and combination group (40 μmol·L^-1 CUB +100 μmol·L^-1 OXA). The proliferation rate of the SW480 was determined by MTT assay. Hoechst33258 staining was used to observe the morphology of SW480 cells. The cell cycle and apoptotic rates of SW480 cells were detected by flow cytometry. The expressions levels of caspase-3,cleaved caspase-3,Bax and Bcl-2 proteins were measured by Western blotting method. Results: The MTT results showed that compared with control group, the proliferation rates of the SW480 cells in different doses of CUB groups and OXA group were significantly decreased(P<0.05); compared with different doses of CUB groups and OXA group, the proliferation rate of the SW480 cells in combination group was significantly decreased(P<0.05). The results of Hoechst 33258 staining showed that the blue fluorescence in the SW480 cells in different doses of CUB groups and OXA group were brighter than that in control group,which showed granular blue fluorescence in the cell nucles. Compared with different doses of CUB groups and OXA group, the blue fluorescence in the SW480 cells in combination group was more significantly bright, and granular blue fluorescence was significantly increased. The cell cycle detection results of flow cytometry showed that compared with control group, the percentages of the SW480 cells in G₂/M phase in different doses of CUB groups and combination group were incresaed (P<0.05); the percentages of SW480 cells in S phase in 40 μmol·L^-1 CUB group, OXA group and combination group were incresaed (P<0.05). The apoptosis detection results of flow cytometry showed that compared with control group, the apoptotic rates of the SW480 cells in different doses of CUB groups and OXA group were increased (P<0.05); compared with different doses of CUB groups and OXA group, the apoptotic rate of the SW480 cells in combination group was significantly increased(P<0.05).The Western blotting results showed that compared with control group, the expressions levels of caspase-3 and Bcl-2 in the SW480 cells in different doses of CUB groups and OXA group were decreased (P<0.05), the expression levels of cleaved caspase-3 and Bax were increased (P<0.05),and the Bcl-2/Bax ratios were decreased(P<0.05); compared with different doses of CUB groups and OXA group, the changes of the above protein expression levels,the cleaved caspase-3/caspase-3 ratio and the Bcl-2/Bax ratio in combination group were more obvious (P<0.05). Conclusion: CUB combined with OXA can effectively inhinbit the proliferation of colon cancer SW480 cells, and its mechanism may be related to the S and G₂/M phase arrest,up regulation of the ratio of cleaved-caspase-3/caspase-3 and down-regulation of the ratio of Bcl-2/Bax.

Key words: cucurbitacin B, oxaliplatin, colon neoplasms, cell proliferation, apoptosis