AIM:To investigate the function of the KISS-1 gene in gastric carcinoma cells and to explore its potential mechanism.METHODS:A KISS-1 eukaryotic expression vector was constructed and transfected into BGC-823 cells.Resistant clones were obtained through G418 selection.reverse transcription-polymerase chain reaction and western blotting were used to detect KISS-1 and matrix metalloproteinase-9(MMP-9)expression in transfected cells.The growth of transfected cells was investigated by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide(MTT)proliferation assays,and the cells’invasive potential was analyzed by basement membrane(Matrigel)invasion assays.The anti-tumor effects of KISS-1 were tested in vivo using allografts in nude mice.RESULTS:The expression level of KISS-1 mRNA andprotein in BGC-823/KISS-1 transfected cells were significantly higher than in BGC-823/pcDNA3.1 transfected cells(P<0.05)or the parental BGC-823 cell line(P< 0.05).The expression level of MMP-9 mRNA and protein in BGC-823/KISS-1 were significantly less than in BGC-823/pcDNA3.1(P<0.05)or BGC-823 cells(P< 0.05).MTT growth assays show the proliferation of BGC-823/KISS-1 cells at 48 h(0.642±0.130)and 72 h(0.530±0.164)were significantly reduced compared to BGC-823/pcDNA3.1(0.750±0.163,0.645±0.140)(P<0.05)and BGC-823 cells(0.782±0.137,0.685± 0.111)(P<0.05).Invasion assays indicate the invasive potential of BGC-823/KISS-1 cells(16.50±14.88)is significantly reduced compared to BGC-823/pcDNA3.1(20.22±14.87)(P<0.05)and BGC-823 cells after 24 h(22.12±16.12)(P<0.05).In vivo studies demonstrate the rate of pcDNA3.1-KISS-1 tumor growth is significantly slower than pcDNA3.1 and control cell tumor growth in nude mice.Furthermore,tumor volume of pcDNA3.1-KISS-1 tumors(939.38±82.08 mm3)was significantly less than pcDNA3.1(1250.46±44.36 mm3) and control tumors(1284.36±55.26 mm3)(P<0.05).Moreover,the tumor mass of pcDNA3.1-KISS-1 tumors(0.494±0.84 g)was significantly less than pcDNA3.1(0.668±0.55 g)and control tumors(0.682±0.38 g)(P <0.05).CONCLUSION:KISS-1 may inhibit the proliferation and invasion of gastric carcinoma cells in vitro and in vivo through the downregulation of MMP-9. AIM: To investigate the function of the KISS-1 gene in gastric carcinoma cells and to explore its potential mechanism. METHODS: A KISS-1 eukaryotic expression vector was constructed and transfected into BGC-823 cells. Resistant clones were obtained through G418 selection. reverse transcription-polymerase chain reaction and western blotting were used to detect KISS-1 and matrix metalloproteinase-9 (MMP-9) expression in transfected cells. The growth of transfected cells was investigated by 3- (4,5-dimethylthiazolyl- -2,5-diphenyltetrazolium bromide (MTT) proliferation assays, and the cells’ invasive potential was analyzed by basement membrane (Matrigel) invasion assays. The anti-tumor effects of KISS-1 were tested in vivo using allografts in nude mice. : The expression level of KISS-1 mRNA and protein in BGC-823 / KISS-1 transfected were significantly higher than in BGC-823 / pcDNA3.1 transfected cells (P <0.05) or the parental BGC- 0.05). The expression level of MMP-9 mRNA and protei BGC-823 / KISS-1 was significantly less than in BGC-823 / pcDNA3.1 (P <0.05) or BGC-823 cells 1 cells at 48 h (0.642 ± 0.130) and 72 h (0.530 ± 0.164) were significantly reduced compared to BGC-823 / pcDNA3.1 (0.750 ± 0.163, 0.645 ± 0.140) 0.782 ± 0.137,0.685 ± 0.111) (P <0.05) .Invasion assays indicate the invasive potential of BGC-823 / KISS-1cells (16.50 ± 14.88) was significantly reduced compared to BGC- 823 / pcDNA3.1 (20.22 ± 14.87 (P <0.05) and BGC-823 cells after 24 h (22.12 ± 16.12) (P <0.05) .In vivo studies demonstrate the rate of pcDNA3.1-KISS-1 tumor growth was significantly slower than pcDNA3.1 and control cell tumor growth in nude mice. Fermentmore, tumor volume of pcDNA3.1-KISS-1 tumors (939.38 ± 82.08 mm3) was significantly less than pcDNA3.1 (1250.46 ± 44.36 mm3) and control tumors (1284.36 ± 55.26 mm3) <0.05) .Moreover, the tumor mass of pcDNA3.1-KISS-1 tumors (0.494 ± 0.84 g) was significantly less than pcDNA3.1 (0.668 ± 0.55 g) and controltumors (0.682 ± 0.38 g) (P <0.05) .CONCLUSION: KISS-1 may inhibit the proliferation and invasion of gastric carcinoma cells in vitro and in vivo through the downregulation of MMP-9.