MECHANISM OF THE PROLIFERATION OF MOUSE S ARCOMA-VIRUS TRANSFORMED-CELLS STABLY REVERTED TO NON MALIGNANCY

Prolonged interferon (IFN) treatment can convert Moloney sarcoma-trans formed mouse Balb C fibroblasts to a stable non-malignant status. The cells recover a number of differentiated features, which are maintaine d even when IFN is permanently omitted from the tissue culture medium. We show here that reversion could be at least in part attributed to c onstitutive IFN beta synthesized only in the reverted cells. The conti nued replication of these cells, although unable to induce tumours in athymic mice, could be the result of the maintained expression of an I FN antagonist termed sarolectin (SCL), a balance being struck between the effects of v-mos oncogene, interferon beta and SCLs. In agreement with Lampl et al. [11], we suggest that normal cell growth is disconti nuous, consisting of sudden bursts followed by prolonged arrests which could be necessary to promote differentiation during the ensuring int erphase.