OBJECTIVETo investigate the therapeutic efficacy of double-mutated oncolytic adenovirus AxdAdB-3 in combination with gemcitabine for treating bladder cancer in an orthotopic nude mouse model.

METHODSThe susceptibility to the adenovirus was evaluated in bladder cancer cell lines YTS-1, T24, 5637 and KK47, and normal cell lines HCV29 and WI38. The cells were infected with AxCAlacZ and stained with 5-bromo-4-chloro-3-indolyl-β-galactoside (X-Gal). Immunostaining against adenoviral hexon protein was performed to determine the selective replication of AxdAdB-3 in the cancer cells. Flow cytometry was used to determine the YTS-1 cells in S phase of cell cycle after adenovirus infection. Cell viability after AxdAdB-3 and/or gemcitabine was measured by CCK-8 assay. Orthotopic bladder cancer model was established in nude mice, and the inhibitory efficacy of intravesical instillation therapy with AxdAdB-3 or/and gemcitabine was assessed.

RESULTSGene transduction efficiency was different among the cell lines, and correlated with expression of CAR. 5637 and KK47 cells with high expression of CAR were more susceptible to the adenovirus, whereas YTS-1 and T24 cells with little CAR expression were resistant to adenoviral infection. Immunostaining showed that the expression levels of hexon protein varied among the cell lines. Normal cells infected with AxdAdB-3 expressed little hexon protein. The proportion of S-phase cells was (39 ± 3) % and (49 ± 5) % in the AxCAlacZ- and AxdAdB-3-infected bladder cancer cells, respectively. AxdAdB-3 effectively induced S-phase entry of cell cycle (P < 0.05). AxdAdB-3 combined with gemcitabine significantly inhibited the growth of bladder cancer cell lines. In vivo, the mean weight of the bladder tumors in mice treated with intravesical instillation of AxCAlacZ, gemcitabine, AxdAdB-3, and AxdAdB-3 + gemcitabine were 400.6, 126.4, 82. 0, 40.4 mg, respectively. Either AxdAdB-3 (P < 0.0001) and gemcitabine (P < 0.0001) suppressed the tumor growth in nude mice, and the combination therapy reduced tumors more effectively than either AxdAdB-3 (P < 0.0001) or gemcitabine (P < 0.0001) alone.

CONCLUSIONSIntravesical instillation therapy with AxdAdB-3 in combination with gemcitabine can effectively inhibit the orthotopic bladder cancer in nude mouse, and further relevant clinical studies are guaranteed.