Presence of a constitutive paracrine β-interferon in v-mos-bearing nonmalignant reverted cells

A stable nonmalignant revertant cell line was derived from Moloney murine sarcoma virus-transformed BALB/c cells after long-term cultivation in the presence of murine type I interferon (IFN). These cells gradually established resistance to exogenous IFN and were also seen to contain IFN-dependent proteins. The presence of an endogenous IFN was confirmed by the results of Northern blot analysis and in situ hybridization with an IFN-beta probe, showing that only mRNA specific for IFN-beta- could be found in the uninduced reverted cells. The latter synthesized only a small amount of IFN-beta protein and exhibited few IFN-specific membrane receptors, which bound recombinant IFN-beta with a high affinity. After treatment with IFN antibody, the overexpression of H-2 major histocompatibility antigen genes was significantly down-regulated. These findings strongly suggest the existence in this reverted cell line of a constitutive IFN which, acting through an autocrine and/or paracrine mechanism, might play a role in maintaining the reverted state.