Interferon-induced phenotypic changes in human tumor cells relative to the effects of interferon on c-ras oncogene expression.

Three human tumor cell lines derived from an osteosarcoma (OHA cells), a bladder carcinoma (EJ cells), and a gastric sarcoma (SHAC cells) were passaged serially in the presence of human interferon-alpha (IFN-alpha) for extended periods of time. The long-term IFN-alpha treatment induced a partial reversion of OHA tumor cell phenotype as exemplified by inhibition of cell proliferation, lack of cellular overlapping in confluent cultures and marked reduction in tumorigenicity. In contrast, under the same conditions, long-term IFN treatment did not reverse but even potentiated some of the phenotypic characteristics (including tumorigenicity) of EJ and SHAC cells. In the three tumor cell lines, the transforming ability, genomic level, or expression of activated oncogenes, c-Ki-ras, c-Ha-ras, and N-ras, respectively, were unaltered with long-term IFN-alpha treatment. Our data indicate that IFN-induced phenotypic changes are not necessarily associated with changes in oncogene expression.