Modulation of protein kinase C activity during inhibition of tumor cell growth by IFN-β and -γ

Abstract

We investigated the effects of human interferon(IFN)-β and -γ on protein kinase C activity in human HEp-2 and KHm-14 tumor cells during IFN-induced inhibition of cell growth. Cytosolic protein kinase C activity in both cell lines was strikingly decreased following treatment with either IFN-β or -γ. In the particulate fraction, IFN-γ decreased protein kinase C activity within 1 hr but it reappeared after 24 hr, whereas IFN-β decreased the activity during the inhibition of cell growth. Furthermore, phorbol-12,13-dibutyrate(PDBu)-binding activity was altered in parallel with the changes in protein kinase C activity induced by the IFNs. In summary, we showed that IFN-β and γ cause long-term modulation of protein kinase C activity in these cultured tumor cells.