Influence of Connexin43 on the Bystander Effect Induced by Double Suicide Genes System in Vitro and in Vivo

Objective: To observe the influence of connexin 43 (Cx43) on the bystander effect induced by cytosine deaminase (CD) and herpes simplex virus thymidine kinase (HSV-tk) coexpression suicide genes system in human cholangiocarcinoma QBC939 cells and transplantation tumors in nude mice. Methods: In vitro, the CD+tk+ and CD+tk+Cx+ cells were respectively treated with 5-fluorocytosine (5-Fc) and Ganciclovir (GCV). The cytotoxic effect was evaluated by MTT method. In order to investigate the influence of Cx43 on the bystander effect, the size of transplantation tumors of the CD+tk+ and CD+tk+Cx+ cells was measured before and after application of 5-Fc and GCV. Results: CD and tk genes were stably expressed in transfected QBC939 cells. The increased expression of Cx43 was determined by testing for the presence of Cx43 mRNA by RT-PCR and the presence of Cx43 protein by Western Blot in CD+tk+Cx+ cells. The killing effect of 5-Fc and GCV on CD+tk+Cx+ cells was more effective than that on CD+tk+ cells both in vitro and in vivo. Conclusion: Double suicide genes system CD/5-Fc+tk/GCV could induce remarkable killing effect on cholangiocarcinoma cells in vitro and transplantation tumors in vivo. The cotransfection of Cx43 gene could enhance the bystander effect and hence the inhibition of carcinoma cells.