12(S)-HETE PROMOTES TUMOR-CELL ADHESION BY INCREASING SURFACE EXPRESSION OF ALPHA-V-BETA-3 INTEGRINS ON ENDOTHELIAL-CELLS

The present work was undertaken to investigate the regulatory role of 12(S)-HETE, a lipoxygenase metabolite of arachidonic acid, in the surface expression Of alpha(v)beta3 integrin receptors in endothelial cells (rat aortic endothelial cells, or RAEC). Several monoclonal and polyclonal antibodies localized alpha(v)beta3 in focal adhesions in both subconfluent and post-confluent RAEC. RAEC alpha(v)beta3 integrins were further characterized by immunoblotting and immunoprecipitation. 12(S)-HETE, but not 12(R)-HETE or other lipoxygenase-derived hydroxy fatty acids, induced a dose-dependent increase in alpha(v)beta3 surface expression in RAEC, which was antagonized by prostacyclin or its analog iloprost as well as by 13-HODE, a 15-lipoxygenase product of linoleic acid. 12(S)-HETE promoted RAEC adhesion to vitronectin, an effect inhibited by antibodies against alpha(v)beta3. 12(S)-HETE also promoted tumor-cell (W256 carcinosarcoma) adhesion to vitronectin, which was inhibited by various antibodies against alpha(IIb)beta3 but not by an antibody against alphav. W256 adhesion to 12(S)-HETE-treated RAEC demonstrated a significant increase, which was inhibited by anti-alpha(v), -beta3, or -alpha(v)beta3 antibodies and by 13-HODE. Western blotting, immunoprecipitation and reverse transcription-polymerase chain reaction indicated that W256 carcinosarcoma cells expressed alphaIIbbeta3 integrins but not alphavbeta3. The results suggest that the lipoxygenase metabolites [i.e., 12(S)-HETE and 13-HODE] play a significant role in modulating tumor-cell interactions with endothelium by enhancing endothelial cell integrin (e.g., alpha(v)beta3) expression.