Gene therapy of epithelial ovarian cancer using adenoviral vectors

Ovarian cancer is the fourth most common cause of death in women. Gene therapy using the herpes simplex virus thymidine kinase (HSV-tk) gene followed by ganciclovir (GCV) treatment has been successfully applied in the treatment of different cancers in experimental animals and in humans. In a recent report, we have demonstrated that the HSV-tk/GCV system can be used efficiently to kill human epithelial ovarian cancer cells (Gynecol Obstet Invest 1997;43:268–75). In this work, we wanted to test the ability of the HSV-tk/GCV to treat ovarian cancer in an animal model.The immune-deficient nude mice model was employed, and mice were injected intraperitoneally with the human epithelial ovarian cancer cell line OVCAR3, 10⁸ cell/mouse. The mice were divided into three different groups, groups 1 and 2 were treated by intraperitoneal injection of adenovirus carrying the HSV-tk gene (ad-tk) on day 3 after cell implantation. Group 1 received 2 × 10⁸ pfu/mouse; group 2 received 20 × 10⁸ pfu/mouse. Group 3 did not receive any viral injection and served as our negative control. All mice received GCV 10 mg/kg IP bid for 6 days. All mice were hosted in the same facilities and had access to food and water ad libitum. Mice in group 3 started to show clinical manifestations of disease by day 10, and all mice were dead by day 21 (16 ± 1.5). At this point mice in groups 1 and 2 appeared perfectly healthy. Autopsy done on group 3 mice demonstrated multiple cancer implants in the abdominal cavity plus hemorrhagic ascitis. In contrast, autopsy on sample mice from groups 1 and 2 at the same time point failed to demonstrate any macroscopic or microscopic cancer.On further follow-up, mice in groups 1 and 2 started to show cancer-related signs, eg, weight loss, movement difficulty, poor reflex response, and finally death. Survival varied between 50 and 101 days with a mean of 66 ± 17 days for group 1 and 74 ± 13 days for group 2. Autopsy done on treated mice demonstrated multiple cancer implants and ascitis. In conclusion, a single injection of ad-tk/GCV was able to improve survival in an ovarian cancer mouse model from an average of 16 days to 74 days. Trials with multiple injection in a novel immune-competent mouse model of ovarian cancer are underway in our laboratory.