Effects of sphingosine kinase 1 inhibitors in combination with 5-FU on gastric cancer MGC-803 cells and the possible mechanisms

Objective To investigate the effects of sphingosine kinase 1(SphK1)inhibitor N,Ndimethylsphingosine(DMS)combined with 5-fluorouracil(5-FU)on the proliferation and apoptosis of gastric cancer MGC-803 cells and to explore the possible mechanisms involved.Methods MGC-803 cells were cultured in vitro.The effects of DMS and 5-FU on cell proliferation,apoptosis,and cell cycle distribution of MGC-803 cells were detected by MTT assay and flow cytometer(FCM),respectively.The expressions of SphK1,TS,DPD,NF-κB p65 and Bcl-2 proteins were detected by Western blot.Results Different concentrations of DMS or 5-FU alone or in combination could obviously inhibit the proliferation of MGC-803 cells in a dose-dependent and time-dependent manners(P 0.05).And the proliferation inhibition rate of MGC-803 cells in the combination group was significantly higher than that in the single drug groups(P0.05).Treatment of MGC-803 cells with DMS did not affect the cell cycle distribution(P0.05).As compared with the cells without drug treatment,DMS or 5-FU alone could obviously increase the apoptosis rate of MGC-803 cells(P0.05);the apoptosis rate in the combination group was significantly higher than that in the single-drug groups(P0.05).The expression levels of SphK1,NF-κB p65 and bcl-2 proteins were down-regulated with the treatment of DMS alone or in combination,whereas those of TS and DPD were not affected.Conclusion DMS can inhibit the proliferation and induce apoptosis of gastric cancer MGC-803 cells in vitro.It shows a good synergetic effect in combination with 5-FU,probably by down-regulating the expressions of SphK1,NF-κB p65 and Bcl-2 proteins.