Abstract: AIM :To determine the inhibitory effect of the hairpin Bcl-XL siRNA on the expression of Bcl-XL gene in human gastric cancer cell line MGC-803, and the effect of Bcl-XL siRNA on drug sensitization in MGC-803 cells.METHODS:Bcl-XL siRNA and negative siRNA were constructed and stably transfected into MGC-803 cells .Immunofluorescence was used to detect the Bcl-XL gene expression .Drug sensitivity of the cells to 5-fluorou- racil ( 5-FU) and diallyl disulfide ( DADS) was analyzed with MTT and flow cytometry .RESULTS:Protein ex- pression level of Bcl-XL in Bcl-XL siRNA stable transfec- tants was reduced to almost background level compared with negative siRNA transfectants or untreated cells .MTT results showed that the cells inhibitary rates of Bcl-XL siRNA transfectants were higher than that of negative vec- tor or untreated cells after treated with 13, 130, 1300, and 13 000 mg·L-1 of 5-FU or treated with 20, 35, and 50 mg·L -1 of DADS .IC50 value of DADS or 5-FU in Bcl-XL siRNA transfected cells was significant lower than that of negative siRNA or untreated cells .Moreover, flow cytometry results demonstrated that Bcl-XL siRNA cells showed higher sub G1 population than negative siRNA or untreated cells after addition 50 mg·L -1 of DADS or 130 mg·L-1 of 5-FU .CONCLUSION:siRNA targeting Bcl- XL gene can specifically down-regulate Bcl-XL expression in MGC-803 cells, and sensitize cells to 5-FU or DADS . Bcl-XL siRNA may be a potential therapy agent against human gastric adenocarcinoma.

Key words: Small interference RNA , Bcl-XL , MGC- 803 cells , apoptosis , 5-FU , DADS