[Down-regulation of sphingosine kinase 1 (SphK1) enhances the chemosensitivity to cisplatin in human colon cancer RKO cells].

Objective To investigate the effect of sphingosine kinase 1 (SphK1) gene silence on the sensitivity to cisplatin (DDP) in RKO colon cancer cell line and the potential mechanism. Methods Targeted SphK1 gene lentivirus virus was constructed to infect RKO cells. The relative mRNA expression of SphK1 was detected by quantitative real-time PCR (qRT-PCR) and the protein level of SphK1 was determined by Western blotting. Then RKO cells were divided into three groups: down-regulated SphK1 group (shSphK1 group), negative control group (shControl group) and blank control group (control group). Cells of these groups were incubated for 0, 24, 48 and 72 hours with 0, 2, 4, 8, 16, 32 μg/mL DDP. After treatment, cell viability was evaluated by MTT assay. Cell apoptosis index was determined by TUNEL. The expressions of ki67, Bcl-2, caspase-9 and caspase-3 were tested by Western blotting. Results Down-regulation of SphK1 inhibited cell proliferation and enhanced apoptosis of RKO cells, expecially after exposed to DDP. Silence of SphK1 sensitized RKO cells to DDP in a concentration- and time-dependent manner. Cell proliferation of shSphK1 group was obviously reduced compared with control group or shControl group, and cell apoptosis rate of shSphK1 group significantly increased compared with control group or shControl group. Moreover, with the down-regulation of SphK1, the expressions of ki67 and Bcl-2 were depressed; the expressions of caspase-9 and caspase-3 were raised, especially after treated with DDP. Conclusion Down-regulation of SphK1 may decrease the expression of Bcl-2, increase the expressions of caspase-9 and caspase-3, inhibit cell proliferation, and promote cell apoptosis, thus improving chemosensitivity of colon cancer RKO cells to DDP.