| Abstract: | The molecular mechanisms underlying the growth inhibition of human tumor cells induced by recombinant interferon-α (IFNα) are mostly unknown. It has been proposed that this effect could be related to down-regulation and/or impaired function of peptide growth factor receptors (PGF-Rs) in tumor cells exposed to IFNα. However, we have previously described that IFNα-induced growth inhibition of human epidermoid carcinoma cells is paralleled by up-regulation of epidermal growth factor receptor (EGF-R). Here we report that an increase in EGF-R synthesis is detectable after 3 hr of exposure to cytostatic concentration of IFNα in epidermoid KB tumor cells. In these experimental conditions IFNα does not depress and even potentiates EGF-R function. IFNα-treated KB cells retain sensitivity to the cytotoxic activity of the anti-EGF-R 225 monoclonal antibody (MAb), which acts through receptor blockade, and are sensitized to the growth-promoting effect of EGF. EGF-induced tyrosine (tyr) phosphorylation both of total cellular protein extracts and of the immunoprecipitated EGF-R is increased in IFNα-treated cells. We conclude that a cross-talk between IFNα and EGF occurs in KB cells since IFNα, at cytostatic concentration, potentiates the effects mediated by the EGF-R. © 1995 Wiley-Liss, Inc. |
