The lipoxygenase metabolite 12(S)-HETE promotes alpha IIb beta 3 integrin-mediated tumor-cell spreading on fibronectin. 
Tumor-cell interaction with the vessel wall during metastasis involves adhesion, induction of endothelial-cell retraction and spreading on the exposed sub-endothelial matrix.  The signals for initiation of tumor-cell spreading and the receptors involved are unknown.  A protocol was developed to distinguish between initial tumor-cell (B16 amelanotic melanoma; B16a) adhesion to and spreading on fibronectin.  The time for maximum spreading was 50 min.  Treatment with a lipoxygenase metabolite of arachidonic acid [12(S)-HETE] resulted in maximum spreading in 15 min (max.  effect approx.  0.1 microM).  Other lipoxygenase metabolites were ineffective.  12(S)-HETE treatment induced a rearrangement of F-actin, vinculin, vimentin intermediate filaments and integrin alpha IIb beta 3, but not integrin alpha 5 beta 1.  Antibodies to alpha IIb beta 3 but not alpha 5 beta 1 blocked the 12(S)-HETE effect on B16a spreading.  B16a-cell attachment to fibronectin resulted in increased metabolism of arachidonic acid to 12(S)-HETE, which was inhibited by lipoxygenase but not by cyclo-oxygenase inhibitors.  Accordingly, lipoxygenase inhibitors but not cyclo-oxygenase inhibitors blocked spontaneous B16a-cell spreading.  The protein-kinase-C inhibitors calphostin C, H7 and staurosporine also inhibited spreading, while the protein-kinase-A inhibitor H8 was ineffective.  These data suggest that B16a-cell spreading on fibronectin is initiated by a lipoxygenase metabolite [12(S)-HETE] of arachidonic acid and is mediated by protein kinase C.