OBJECTIVETo investigate the treatment efficiency and mechanism of recombinant adenoviral vector carrying LRIG1 gene driven by Survivin promoter for bladder cancer.

METHODSHuman bladder cancer cell line BIU87 and immortalized human bladder epithelial cells SV-HUC-1 were infected with Ad-Surp-LRIG1 and Ad-LRIG, respectively. The selective infection efficiency of Ad-Surp-LRIG1 and Ad-LRIG were evaluated by checking the expression of epidermal growth factor receptor (EGFR). The MTT method was used to test cell growth inhibition ratio of Ad-Surp-LRIG1 and Ad-LRIG. Heterotransplanted models of human bladder cancer cell line BIU87 cells in nude mice were established. The mice were randomly divided into 3 groups during the experiment: Ad-Surp-LRIG1 group received viral supernatant solution of Ad-Surp-LRIG1 by tail vein injection; Ad-LRIG group received viral supernatant solution of Ad-LRIG by tail vein injection; and PBS group received phosphate buffer solution (PBS). The growth of tumors were observed and the growth curve was mapped. The expression of LRIG1 and EGFR were examined by reverse transcription PCR (RT-PCR).

RESULTSWhen Multiplicity of infection was 25, the transfection efficiency of Ad-Surp-LRIG1 was 74.56% in BIU87 cells and 0 in SV-HUC-1 cells (χ² = 58.640, P = 0.000), while the transfection efficiency of Ad-LRIG was 68.27% in BIU87 cells and 72.52% in SV-HUC-1 cells (χ² = 0.075, P = 0.784). The transfection efficiency difference of Ad-Surp-LRIG1 and Ad-LRIG in BIU87 cells was not statistically significant (χ² = 0.016, P = 0.898). Compared with PBS, Ad-Surp-LRIG1 and Ad-LRIG1 could inhibit BIU87 cell growth, the difference was significant in 4 days after transfection (F = 15.960, P = 0.000). There was not significant difference in cell growth rate of Ad-Surp-LRIG1 group and Ad-LRIG1 group. The tumor growth rate in Ad-Surp-LRIG1 group was slower than that in the other 2 groups. The tumor quality in Ad-Surp-LRIG1 was lighter than that in the other two groups, the differences were statistically significant (F = 97.860, P = 0.000), the quality difference in Ad-LRIG1 group and PBS group was not statistically significant difference (t = 1.73, P = 0.06). Compared with Ad-LRIG1 group and PBS group, the mRNA expression of LRIG1 was obviously up-regulated and that of EGFR was down-regulated in Ad-Surp-LRIG1 group (P < 0.01).

CONCLUSIONSThe recombinant adenoviral vector of Ad-Surp-LRIG1 could selectively transfected BIU87 cells, which could inhibit significantly the growth of bladder cancer in vivo and in vitro, the mechanism may be partly LRIG1 can downgrade the expression of EGFR.