Suppressed proliferation of mouse hepatoma cells by conditioned media from interferon gamma-treated hepatocytes

The effect of mouse interferon gamma (IFNg) on the proliferation of Hepa-1c1c7, mouse hepatoma cells was analyzed by means of [3H]thymidine incorporation. IFNg did not suppress the proliferation of Hepa-1c1c7 cells cultivated alone, however, it effectively suppressed in coculture with B6C3F1 mouse hepatocytes and in IFNg-treated mouse hepatocyte-conditioned media. Suppression of proliferation of hepatoma cells was detected only in the IFNg-treated hepatocyte-conditioned media but not in the control hepatocyte-conditioned media. The magnitude of suppression depended upon the amount of IFNg used in the preparation of conditioned media. The suppressive effect of IFNg-treated hepatocyte-conditioned media was retained by an ultrafilteration membrane (M.W. cut off 30,000), and its activity was abrogated by trypsin digestion and heat treatment. These results suggest that IFNg-treated mouse hepatocytes may release a soluble mediator(s) which suppressed the proliferation of hepatoma cells and that IFNg interactions with hepatocytes could be important to the antitumor defense mechanisms of the liver.