Effects of interferon-beta on Daudi cells and on small cell lung carcinoma cells which over-express the c-myc oncogene.

The effects of human interferon-beta (IFN-beta) on four lung cancer cell lines, two of which over-express the c-myc oncogene, were compared to Daudi cells which also over-express c-myc. The anti-proliferative effect of IFN-beta on Daudi cells was correlated with a decrease in steady state levels of c-myc mRNA. IFN-beta treatment of a classic small cell lung carcinoma cell line and a non-small cell lung carcinoma cell line which express normal levels of c-myc did not decrease the rate of cell proliferation. IFN-beta, however, was found to have dramatic anti-proliferative effects on the two lung cancer cell lines with c-myc over-expression. The growth inhibitory effects of IFN-beta on the two lung cancer cell lines could not, however, be correlated with decreased amounts of c-myc mRNA. Furthermore, Western blot analysis showed that interferon treatment did not detectably affect the c-myc protein levels in these cells. Therefore, the mechanism by which IFN-beta slowed the growth rates of the two lung cancer cell lines did not appear to directly involve down-regulation of the c-myc oncogene, expressed in amplified amounts, in these cells.