INHIBITION BY MOUSE ALPHA-BETA-INTERFERON OF THE MULTIPLICATION OF ALPHA-BETA-INTERFERON-RESISTANT FRIEND-ERYTHROLEUKEMIA CELLS COCULTURED WITH MOUSE HEPATOCYTES

  • 15 June 1990
    • journal article
    • research article
    • Vol. 50  (12) , 3533-3539
Abstract
Administration of .alpha./.beta.-interferon (IFN) exerts a marked antitumor effect in DBA/2 mice given injections i.v. of large numbers of IFN-.alpha./.beta.-resistant erythroleukemia cells (FLC). To investigate the possible mechanisms of FLC tumor inhibition in the liver of interferon-treated mice, we developed an in vitro model consisting of a coculture of IFN-.alpha./.beta.-resistant 3Cl8 FLC and syngeneic mouse hepatocytes. Whereas IFN-.alpha./.beta. did not inhibit the multiplication of 3Cl8 FLC cultivated alone, it effectively inhibited the multiplication of 3Cl8 FLC in coculture with hepatocytes. The inhibitory effect was directly proportional to the amount of IFN-.alpha./.beta. added to the cocultures, and more than 90% inhibition of FLC multiplication was noted with 1.6 .times. 105 IU/ml of IFN-.alpha./.beta. on Day 3 of coculture. When FLC were separated from the monolayer of hepatocytes by a pored membrane (0.4 .mu.m), the inhibitory effect on FLC proliferation was unchanged, indicating that a soluble factor(s) released from IFN-treated hepatocytes was most important in the inhibition of FLC multiplication. An inhibitory activity of FLC multiplication was detected only in the conditioned medium of IFN-treated hepatocytes but not in the conditioned medium of control hepatocytes nor in extracts of IFN-treated or control hepatocytes. The inhibitory factor(s) in the conditioned medium of IFN-treated hepatocytes was retained by an ultrafiltration membrane (Mr cut off 10,000), and its activity was completely abrogated by trypsin digestion. Its stability to treatment with 1 M acetic acid as well as lack of correlation between the antiproliferative effect and the amount of L-arginine in the medium distinguished this factor(s) from liver arginase which was also found to be a potent inhibitor of FLC multiplication in vitro. The inhibitory factor(s) was also distinguishable in its biological activity from IFN .gamma., interleukin 1.alpha. and .beta., and transforming growth factor .beta.1 and .beta.2. These results suggest the possibility that the inhibitory effect of IFN-.alpha./.beta. on the development of 3Cl8 FLC in the livers of IFN-treated mice may be mediated by an IFN-induced inhibitor of FLC multiplication.