INTERFERON-GAMMA-INDUCING FACTOR GENE TRANSFECTION INTO LEWIS-LUNG-CARCINOMA CELLS REDUCES TUMORIGENICITY IN-VIVO

To investigate the immunoregulatory effect of murine interferon-gamma- inducing factor (mIGIF), we transfected Lewis lung carcinoma (LLC) cel ls with a mammalian expression vector containing the mIGIF complementa ry DNA. The culture medium of the transfectant cells stimulated interf eron-gamma (IFN-gamma) production by spleen cells in vitro in the pres ence of anti-CD3 antibody and markedly potentiated the effect of inter leukin-12 (11,-12) on IFN-gamma production by spleen cells. mIGIF tran sfectant cells showed reduction of tumorigenicity and induction of an in vivo immune-protective effect against the parental LLC cells. To ex amine the combined effect of systemic administration of recombinant IL -12 (r1L-12) and local mIGIF on the tumorigenicity, mice were challeng ed with LLC or transfectant cells on day 0, and the tumor-bearing mice were injected with 50 ng of rIL-12 intraperitoneally from day 7 to 11 . Systemic rIL-12 showed an anti-tumor effect. However, mIGIF gene exp ression did not potentiate this effect of systemic rIL-12 in vivo.