This study examined the effect of silencing LRIG3 expression on the proliferation and apoptosis of bladder cancer T24 cells and explored the role of LRIG3 in the tumorigenesis of bladder cancer.Bladder cancer T24 cells were routinely cultured and pSilencer plasmids were employed to construct LRIG3 eukaryotic expression vector of LRIG3-siRNA,i.e.,pSilencer-LRIG3-siRNA.After confirmation,the vector was transfected into HEK293 cells to make a replication-deficient adenovirus,pAd-LRIG3-siRNA,which was then introduced into bladder cancer T24 cells.RT-PCR,Western-blotting were performed to detect the levels of LRIG3 mRNA and proteins.Cells number was determined by using MTT test.Hoechst33258 staining,transmission microscopy,flow cytometery were conducted to examine the cell apoptosis.Three groups included a blank control group,a negative control group (containing non-interfering plasmids) and a pAd-LRIG3-siRNA group.Our results showed that the recombinant pAd-LRIG3-siRNA was successfully transfected into the bladder cancer T24 cells.The siRNA formed by the transcription of the recombinant plasmids resulted in significantly reduced expressions of LRIG3 gene and protein and significantly decreased cell proliferation and growth in the pAd-LRIG3-siRNA group as compared with the control group (P＜0.01).The siRNA also caused apoptotic changes of some cells,with the apoptosis rate being (17.69±0.75)％,which was significantly different from that of the control group (P＜0.01).It was concluded that recombinant pAd-LRIG3-siRNA plasmids could effectively decrease the expression of LRIG3 mRNA and proteins and,to some extent,inhibit the proliferation and promote the apoptosis of bladder cancer T24 cells.Silencing LRIG3 gene might be a novel alternative for the treatment of bladder cancer.