AIM:To investigate the effects of small interference RNA(siRNA) targeting of Cdx2 on human gastric cancer MGC-803 cells in vitro and in vivo.METHODS:The recombinant pSilencer 4.1-Cdx2 siRNA plasmids were constructed and transfected into gastric cancer MGC-803 cells in vitro.The stable transfectants were selected.The effects of Cdx2 siRNA on growth,proliferation,cell cycle,apoptosis,migration and invasiveness of human gastric cancer MGC-803 cells were evaluated and the expression of phosphatase and tensin homolog(PTEN),caspase-9 and caspase-3 was observed in vitro by reverse transcription polymerase chain reaction(RT-PCR) and Western blotting analysis.We also investigated the effect of Cdx2 siRNA on growth of MGC-803 cells in nude mice in vivo.RESULTS:Cdx2 siRNA led to inhibition of endogenous Cdx2 mRNA and protein expression as determined by RT-PCR and Western blotting analysis.Cdx2 siRNA significantly inhibited cell growth and proliferation,blocked entry into the S-phase of the cell cycle,induced cell apoptosis,and reduced the motility and invasion of MGC-803 cells.Cdx2 siRNA also increased PTEN expression,and activated caspase-9 and caspase-3 in MGC-803 cells in vitro.In addition,siRNA targeting of Cdx2 inhibited the growth of MGC-803 cells and promoted tumor cell apoptosis in vivo in nude mice tumor models.CONCLUSION:Cdx2 was involved in regulating progression of human gastric cancer cells MGC-803.Manipulation of Cdx2 expression may be a potential therapeutic strategy for gastric cancer. AIM: To investigate the effects of small interference RNA (siRNA) targeting of Cdx2 on human gastric cancer MGC-803 cells in vitro and in vivo. METHODS: The recombinant pSilencer 4.1-Cdx2 siRNA plasmids were constructed and transfected into gastric cancer MGC-803 cells in vitro. These stable transfectants were selected. These effects of Cdx2 siRNA on growth, proliferation, cell cycle, apoptosis, migration and invasiveness of human gastric cancer MGC-803 cells were evaluated and the expression of phosphatase and tensin homolog (PTEN), caspase-9 and caspase-3 were observed in vitro by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting analysis. We also investigated the effect of Cdx2 siRNA on growth of MGC-803 cells in nude mice in vivo .RESULTS: Cdx2 siRNA led to inhibition of endogenous Cdx2 mRNA and protein expression as determined by RT-PCR and Western blotting analysis. Cdx2 siRNA was marked cell growth and proliferation, blocked entry into the S-phase of the cell c ycle, induced cell apoptosis, and reduced the motility and invasion of MGC-803 cells. Cdx2 siRNA also increased PTEN expression, and activated caspase-9 and caspase-3 in MGC-803 cells in vitro. the growth of MGC-803 cells and promoted tumor cell apoptosis in vivo in nude mice tumor models. CONCLUSION: Cdx2 was involved in regulating progression of human gastric cancer cells MGC-803. Manipulation of Cdx2 expression may be a potential therapeutic strategy for gastric cancer .