[Cancer immunotherapy by murine bladder cancer cells transfected with mouse interferon-gamma gene]

We established constitutively an interferon-gamma (IFN-gamma) producing cell line (MBT2/gamma) from a mouse bladder cancer cell line (MBT2) by retroviral transfer of a mouse IFN-gamma cDNA. Although the in vitro cell growth of these cells was unaffected by the IFN-gamma production, their subcutaneous tumor growth in syngeneic C3H/He mice was different; MBT2/gamma tumor growth was more strongly suppressed (3/20) than that of MBT2 (10/10). MBT2/gamma tumor growth was observed in nude mice (6/6). The mice immunized with MBT2/gamma were resistant to tumor growth of the parental cells (7/9; 77%), but permitted the growth of another kind of C3H/He tumor line. These findings indicate that the reduced tumorigenicity of the IFN-gamma producing line was due to the augmented specific antitumor immunity, probably as a result of the immunomodulatory effects of the IFN-gamma derived from the tumor.