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 surf ace expression Of alpha(v)beta3 integrin receptors in endothelial cell s (rat aortic endothelial cells, or RAEC). Several monoclonal and poly clonal antibodies localized alpha(v)beta3 in focal adhesions in both s ubconfluent 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 exp ression in RAEC, which was antagonized by prostacyclin or its analog i loprost as well as by 13-HODE, a 15-lipoxygenase product of linoleic a cid. 12(S)-HETE promoted RAEC adhesion to vitronectin, an effect inhib ited by antibodies against alpha(v)beta3. 12(S)-HETE also promoted tum or-cell (W256 carcinosarcoma) adhesion to vitronectin, which was inhib ited by various antibodies against alpha(IIb)beta3 but not by an antib ody against alphav. W256 adhesion to 12(S)-HETE-treated RAEC demonstra ted a significant increase, which was inhibited by anti-alpha(v), -bet a3, or -alpha(v)beta3 antibodies and by 13-HODE. Western blotting, imm unoprecipitation and reverse transcription-polymerase chain reaction i ndicated that W256 carcinosarcoma cells expressed alphaIIbbeta3 integr ins but not alphavbeta3. The results suggest that the lipoxygenase met abolites [i.e., 12(S)-HETE and 13-HODE] play a significant role in mod ulating tumor-cell interactions with endothelium by enhancing endothel ial cell integrin (e.g., alpha(v)beta3) expression.