Adenovirus-mediated HSV-tk Gene/GCV Therapy For Experimental Human Bladder Cancer

Background: Recent trials of suicide gene therapy for bladder cancer have shown that these threatments were well tolerated with significant effects and minimal side effects. But patients with high-grade bladder cancer frequently experience recurrence and progress and there is minimal threatment success with surgery,chemotherapy or radiotherapy in metastasis bladder cancer. In this study, we evaluated the feasibility and efficacy of suicide gene therapy using adnovirus-mediated herpes simplex virus thymidine kinase gene combined with ganciclbvir as a potential therapeutic approach in murine subcutaneous bladder cancer models. Methods: A replication-deffective adenovirus vector containing toxic HSV-tk gene under the transcriptional control of CMV promoter was used. Subcutaneous bladder cancer was established with 1 106 human bladder cancer cells in BALB/c nude mice. Intratumoral injection of Ad.CMV-tk(5 108 plaque forming units PFU) hi combination with GCV (40mg/Kg body weight/day i.p. bid 10 days) was administered in vivo for the determination of treatment efficacy .We also determinated tumor microvessel density (MVD), proliferating cell nuclear antigen (PCNA) expression and CD8+T cell infiltration by immunohistochemical methods. Results: In vivo experiments demonstrated greater inhibition in SCaBER tumor growth for the animals treated with Ad.CMV-tk/GCV therapy (P<0.01). Central tumor necrosis and apoptosis were revealed by histomorphology and FCM compared with other control animals ( Ad.CMV-tk/PBS, PBS/GCV, PBS alone).The microvessel density and PCNA were significantly decreased compared with other control animals revealed by immunohistochemical methods(P<0.01). The CD8+T cell infiltration was also found hi Ad.CMV-tk treatment tumor. The expression of HSV-tk but not the adenoviral El gene was determined by PCR. Derect intratumoral injection with Ad.CMV-tk followed by GCV also resulted in significant tumor growth inhibition over the MMC group (P<0.01). Conclusions: Suicide gene therapy using Ad.CMV-tk/GCV provides an effective therapyin an experimental murine subcutaneous bladder cancer by significantly inhibiting tumor growth. The treatment mechanisms of Ad.CMV-tk/GCV system included inducing apoptosis, decreasing PCNA expression, supressing angiogenesis and improving antitumor immune response. Ad.CMV-tk/GCV therapy may become a potential protocol for poor prognosis bladder cancer for clinical use.