Suicide gene therapy for human uterine adenocarcinoma cells using herpes simplex virus thymidine kinase

In gene therapy, the herpes simplex virus thymidine kinase (HSV-tk) gene is widely used as a suicide agent. Tumor cells expressing HSV-tk are sensitiv e to nucleoside analogs such as ganciclovir (GCV). An advantage of this sys tem is the bystander killing effect whereby HSV-tk-positive cells exposed t o GCV are lethal to surrounding HSV-tk-negative cells. We transfected the H SV-tk gene into a human cervical adenocarcinoma cell line, BU25TK-, and a h uman endometrial adenocarcinoma cell line, HHUA, by the Lipo-fectine method . The sensitivity of HSV-tk-positive cells to GCV and bystander killing eff ect on HSV-tk-negative cells were examined in vitro. HSV-tk-positive cells were sensitive to GCV at concentrations of 1 to 100 mu g/ml in a dose- and time-dependent manner. The growth of HSV-tk-negative cells was inhibited wh en the population of cultured cells contained more than about 3% HSV-tk-pos itive cells. Moreover, for BU25TK- cells, HSV-tk-positive cells were inject ed into SCID mice subcutaneously and the effects of GCV therapy and bystand er killing at a daily concentration of 25 mg/kg for 14 days were examined. HSV-tk-positive tumors transduced into SCID mice almost disappeared upon GC V treatment. Furthermore, tumor reduction was observed when mixtures of HSV -tk-negative cells containing more than 20% HSV-tk-positive cells were inje cted into SCID mice. In conclusion, the HSV-tk/GCV system might be applied to both cervical and endometrial adenocarcinoma. (C) 1999 Academic Press.