To investigate the inhibitory effect of the Bcl-XL small interfering RNA(siRNA)on BcI-XLgene expression in the human gastric cancer cell line MGC-803,green fluorescent protein(GFP)siRNAwas constructed and transfected into MGC-803 ceils,together with GFP expression vector pTrace SV40.GFP expression levels were observed using fluorescence microscopy.Bcl-XL siRNA and negative siRNAwere then constructed and stably transfected into MGC-803 cells.RT-PCR and immunofluorescence wereused to detect the expression of Bcl-XL.Spontaneous apoptosis was detected by acridine orange(AO)andflow cytometry.Results were as follows:(1)48 h after GFP expression vector and GFP siRNA co-transfection,the expression level of GFP in the GFP siRNA group was much lower than the negative siRNA group,according to fluorescence microscopy results.The mRNA and protein levels of Bcl-XL in Bcl-XL siRNAstable transfectants were reduced to almost background level compared with negative siRNA transfectantsor untreated cells.(2)Changes in nucleus morphology was observed by AO staining nucleic and flowcytometry analysis,which showed that stable Bcl-XL siRNA transfectants have an increased spontaneousapoptosis (21.17%+1.26% vs.1.19%+0.18% and 1.56%+0.15% respectively,P<0.05 vs.negative siRNAor untreated control),siRNA targeting GFP or Bcl-XL genes can specifically suppress GFP or BcI-XLexpression in MGC-803 cells,and Bcl-XL siRNA can increase spontaneous apoptosis.Bcl-XL siRNA maybe a beneficial agent against human gastric adenocarcinoma. To investigate the inhibitory effect of the Bcl-XL small interfering RNA (siRNA) on BcI-XLgene expression in the human gastric cancer cell line MGC-803, green fluorescent protein (GFP) siRNAwas constructed and transfected into MGC-803 ceils, together with GFP expression vector pTrace SV40.GFP expression levels were observed using fluorescence microscopy. Bcl-XL siRNA and negative siRNAwere constructed and stably transfected into MGC-803 cells. RT-PCR and immunofluorescence were used to detect the expression of Bcl-XL. Spontaneous apoptosis was detected by acridine orange (AO) and flow cytometry. Results were as follows: (1) 48 h after GFP expression vector and GFP siRNA co-transfection, the expression level of GFP in the GFP siRNA group was much lower than the negative siRNA group , according to a fluorescence microscopy results. The mRNA and protein levels of Bcl-XL in Bcl-XL siRNA target transfectants were reduced to almost background level compared with negative siRNA transfectants unt untated cells. (2) Changes in nucleus morphology was observed by AO staining nucleic and flowcytometry analysis, which showed that stable Bcl-XL siRNA transfectants have an increased spontaneousapoptosis (21.17% + 1.26% vs.1.19% + 0.18% and 1.56% + 0.15% , P <0.05 vs. negative siRNA or untreated control) siRNA targeting GFP or Bcl-XL genes can specifically suppress GFP or Bcl-XL expression in MGC-803 cells, and Bcl-XL siRNA can increase spontaneous apoptosis. beneficial agent against human gastric adenocarcinoma.