EPIDERMAL GROWTH FACTOR-STIMULATED PRODUCTION OF ESTERIFIED 13(S)-HYDROXYOCTADECADIENOIC ACID IS ASSOCIATED WITH TUMOR-SUPPRESSOR PHENOTYPEIN SYRIAN-HAMSTER EMBRYO FIBROBLASTS

Epidermal growth factor (EGF) stimulates the lipoxygenase metabolism o f linoleic acid to 13(S)-hydroxyoctadecadienoic acid (HODE) in Syrian hamster embryo (SHE) fibroblasts. 13(S)-HODE is a potent and specific enhancer of EGF-dependent DNA synthesis in normal phenotypic SHE cells (supB(+)), but is inactive in Variant SHE cells that have lost tumor suppressor gene function (supB(-)). EGF activation of quiescent SHE ce lls results in increased levels of 13-HODE esterified in cellular phos pholipid and triglyceride. Steric analyses suggest that this metabolit e is generated in part by direct oxygenation of membrane lipids by an n-6 lipoxygenase. In studies on the uptake and mobilization of 13-HODE in SHE cells, we observed EGF to stimulate a time- and dose-dependent incorporation and reacylation of the monohydroxy linoleate metabolite . The level of 13-HODE uptake in supB(+) cells is twice that of supB(- ). Among classes of phospholipids, radiolabeled 13-HODE is esterified pre dominantly into phosphatidylcholine and this distribution pattern is similar for both SHE cell lines. Pretreatment of cells with the tyr osine kinase inhibitor methyl-2,5-dihydroxycinnamate blocks EGF-stimul ated HODE incorporation. Inhibition of tyrosine phosphatase activity w ith vanadate potentiates HODE uptake in supB(+) but not supB(-) cells. Moreover, activation of protein kinase C with phorbol ester stimulate s HODE incorporation in the supB(+) line only. The differential effect s of EGF on 13-HODE uptake and mobilization in supB(+) and supB(-) cel ls appear to be related to loss of the tumor suppressor phenotype. EGF -stimulated generation of esterified 13-HODE may be an important biolo gical process in determining the mechanism and site of HODE interactio n with the mitogenic signaling pathway.