The Linoleic Acid Metabolite, (13S)-Hydroperoxyoctadecadienoic Acid, Augments the Epidermal Growth Factor Receptor Signaling Pathway by Attenuation of Receptor Dephosphorylation

Abstract

In Syrian hamster embryo (SHE) fibroblasts, epidermal growth factor receptor (EGFR) tyrosine kinase activity regulates the metabolism of endogenous linoleic acid to (13S)-hydroperoxyoctadecadienoic acid (13S)-HPODE). (13S)-HPODE stimulates EGF-dependent mito-genesis in a SHE cell phenotype, which expresses tumor suppressor genes (supB ؉ ), but was not effective in a variant that does not express these suppressor genes (supB ؊ ). In the present study, we have investigated the potential effects of this lipid metabolite on the EGFR signaling pathways in these two SHE cell lines. Treatment of quiescent SHE cells with EGF produced a rapid, transient increase in the tyrosine phosphorylation of EGFR. Dependence on EGF concentration for EGFR tyrosine phosphorylation was similar in both SHE cell lines, but a more prolonged phosphorylation was detected in the supB ؊ variant. Incubation of supB ؉ cells with (13S)-HPODE and EGF increased EGFR autophosphorylation and tyrosine phosphorylation on several signaling proteins with Src homology-2 domains including GTPase-activating protein. The lipid metabolite did not significantly alter EGF-dependent tyrosine phosphorylation in the supB ؊ variant. Tyrosine phosphorylation of mitogen-activated protein (MAP) kinase was also measured. The addition of (13S)-HPODE increased the extent and duration of MAP kinase tyrosine phosphorylation in supB ؉ cells but not in the supB ؊ variant. MAP kinase activity in supB ؉ cells, as measured in immunoprecipitates from cells after the addition of EGF, was increased by the presence of (13S)-HPODE. The addition of (13S)-HPODE did not directly alter EGFR kinase activity or the internalization of the EGFR. However, the addition of (13S)-HPODE to supB ؉ cells extended the tyrosine phosphorylation of the EGFR in response to EGF. The dephosphorylation of the EGFR was measured directly, and a slower rate was observed in the supB ؊ compared with the supB ؉ cells. Incubation of the supB ؉ cells with (13S)-HPODE attenuated the dephosphorylation of the EGFR. Thus, (13S)-HPODE stimulates EGF-dependent mitogenesis and up-regulation of EGF-dependent tyrosine phosphorylation by inhibiting the dephosphorylation of the EGFR. This study shows that a metabolite of an essential dietary fatty acid, linoleic acid, can modulate tyrosine phosphorylation and activity of key signal transduction proteins in a growth factor mitogenic pathway.Several lines of evidence suggest that metabolism of the cis-polyunsaturated fatty acids, arachidonic acid and linoleic acid, by prostaglandin H synthase and lipoxygenases generate metabolites that modulate the EGF 1 mitogenic signal in fibroblasts. In Balb/c 3T3 fibroblasts, mitogenic stimulation by EGF induced the formation of prostaglandin E 2 (1) and the expression of c-myc (2). Inhibition of prostaglandin H synthase partially blocked both mitogenesis and c-myc expression, which was restored and enhanced by the addition of exogenous prostaglandins. In these studies lipoxygenase inhibitors were very effective inhibitors of mitogenesis...

12/15-lipoxygenase–derived lipid peroxides control receptor tyrosine kinase signaling through oxidation of protein tyrosine phosphatases

“…In this context it should be noted that the oxidation of the lipid phosphatase PTEN is regulated by unidentified arachidonic acid metabolites (46). Other previous studies meriting attention include the findings that 13-OOH-octadecadienoic acid augments EGFR signaling and that 12-HPETE activates p38 MAPK in platelets (42,47).…”

Melatonin-Depleted Blood from Premenopausal Women Exposed to Light at Night Stimulates Growth of Human Breast Cancer Xenografts in Nude Rats

“…Based on human breast cancer perfusion studies described here, however, we now present the first evidence establishing the fact that physiologic, nocturnal circulating levels of melatonin in humans suppress human breast cancer proliferative activity in vivo as they do in rat hepatoma 7288CTC. This occurs via an MT 1 melatonin receptor-mediated reduction in cAMP formation, a blockade of linoleic acid uptake/ metabolism, via 15-lipoxygenase-1, to 13-HODE leading to a down-regulation in the activation of the MEK/ERK1/2 growth signaling pathway, which is related to both the epidermal growth factor and insulin-like growth factor-I receptor systems (49)(50)(51). The fact that similar results were obtained in tissue-isolated rat hepatoma 7288CTC and SR À and SR + human breast cancer xenografts suggests that this is a more general mechanism by which nocturnal melatonin concentrations inhibit cancer growth in vivo, irrespective of tumor type and/or steroid receptor status.…”

15-Lipoxygenase-1 Metabolites Down-regulate Peroxisome Proliferator-activated Receptor γ via the MAPK Signaling Pathway

“…The addition of tyrosine kinase inhibitors inhibited not only EGF-induced mitogenesis but also the formation of 15-LO-1 metabolites. Furthermore, the exogenous addition of 13-(S)-HpODE or 13-(S)-HODE, but not 15-(S)-HETE, in combi-nation with EGF to Syrian hamster embryo cells inhibited the dephosphorylation of the EGF receptor, thereby up-regulating the EGF cascade and potentiating the mitogenic response (20). The 15-LO-1 linoleic acid metabolites, 13-(S)-HpODE and 13-(S)-HODE, up-regulated EGF-dependent cell proliferation and enhanced MAPK activity, but the 15-LO-2 arachidonic acid metabolite, 15-(S)-HETE, was not active.…”