Abstract: Objective To construct a glucosylceramide synthase(GCS)specific small interfering RNA(siRNA)expression vector and to investigate its effect on GCS expression and multidrug resistance in gastric carcinoma cells.Methods According to the encoding sequence of mRNA of GCS,oligonucleotide sequences were designed and synthesized,and then cloned into siRNA expression vector to generate the plasmid pSUP ERGCS.The recombinant plasmid was transfected into vincristine(VCR)resistant gastric carcinoma cells SGC7901/VCR.The expression levels of GCS were detected by western blot.The drug resistance of SGC7901/VCR was assayed by MTT.Results The expected fragment was obtained by restriction endonuclease digestion;The constructed vector effectively inhibited the expression of GCS in SGC7901/VCR cells.The sensitivity to VCR of the transfected cells was increased.Conclusion GCS siRNA expression vector is successfully constructed,which suppresses GCS expression and reverses drugresistance of SGC7901/VCR.It will be helpful for the gene therapy of tumors.