Gene therapy by in vivo interferon-gamma gene transfer to murine bladder tumor

For the clinical application of the cytokine gene therapy, the antitumor effects of systemic administration of Interferon-gamma (IFN-gamma) and those of in vivo direct IFN-gamma gene transfer to the tumors of mouse bladder carcinoma (MBT2) were compared. After the subcutaneous inoculation of MBT2 cells into mice, 10(2), 10(3) or 10(4) units of IFN-gamma were injected intraperitoneally (i.p.) or subcutaneously (s.c.). Neither i.p. nor s.c. injection of IFN-gamma resulted in tumor suppression or prolonged the survival time of tumor-bearing mice. The effect of in vivo direct IFN-gamma gene transfer by a retrovirus vector to MBT2 tumors was also evaluated. After the subcutaneous inoculation of MBT2 cells into mice, a virus culture supernatant containing IFN-gamma gene was injected into the same tumor site once a day for 3 days. In 50% of the mice in the treatment groups with IFN-gamma gene induction, no tumor formation was observed. Tumor-free survival and actuarial survival in the treatment groups were significantly longer than those in the control group. These results showed the possibility of in vivo direct IFN-gamma gene transfer into tumors and were encouraging for the execution of tumor cell-targeted IFN-gamma gene therapy against human bladder cancer.