Relationship between Inhibition of Cell Growth and of Transferrin Receptor Expression by Interferon (IFN) α: Studies in IFN-sensitive and IFN-resistant Daudi Cells

We previously showed that treatment of different cell lines with interferon-α(IFN-α) concurrently inhibited both cell growth and the rise observed in 125I-labelled transferrin binding when cells are exposed to culture conditions that stimulate proliferation. To gain insight into the relationship between these two IFN-induced inhibitory processes, we investigated the effect of IFN-α on the binding of 125I-labelled transferrin to Daudi cells sensitive or resistant to its antiproliferative action. We found a close correlation between the ability of IFN-α to inhibit cell growth and to inhibit transferrin receptor expression. Since growth inhibition induced by other agents is not always accompanied by an inhibition of transferrin receptor expression, the previous and present observations suggest that the inhibitory effect of IFN on this expression is at least one of the mechanisms by which IFN inhibits cell proliferation. We also observed that IFN-α did not modify transferrin receptor biosynthesis in IFN-sensitive Daudi cells, suggesting that IFN-α may change the processing of the transferrin receptor molecules, making them unable to bind transferrin.