[Role of interferon in the phenotypic reversion of transformed cells: loss of malignancy].

Transformation of cells by oncogenic RNA viruses is related to a number of significant changes in cell morphology and functions. The most common features of transformed cells are essentially the decrease of cell adhesiveness and the loss of contact inhibition. These changes are probably associated with an alteration of the cytoskeleton together with a marked modification in the number and distribution of membrane and extracellular matrix components. BALB/c embryonic fibroblasts transformed by murine sarcoma virus Moloney strain (MSV) are characterized by a disorderly growth pattern with a high proliferative rate and a colony forming capacity in soft agar. After a continuous treatment of MSV-transformed cells with interferon, these cells recover a normal phenotype and contact inhibition and are unable to form colonies in agar. Furthermore, reverse transformation is correlated with a polymerization of cytoskeleton constituents and a neosynthesis of two major matrix components: collagen and fibronectin. This experimental model leads to a new concept of the physiological role of interferon, such as mediator of the regulation of cell phenotype and antitumor protection.