12(S)‐hete promotes tumor‐cell adhesion by increasing surface expression of α_Vβ₃ 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 α_vβ₃ integrin receptors in endothelial cells (rat aortic endothelial cells, or RAEC). Several monoclonal and polyclonal antibodies localized α_vβ₃ in focal adhesions in both subconfluent and post‐confluent RAEC. RAEC α_vβ₃ 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 α_vβ₃ 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 α_vβ₃ 12(S)‐HETE also promoted tumor‐cell (W256 carcinosarcoma) adhesion to vitronectin, which was inhibited by various antibodies against α_IIbβ₃ but not by an antibody against αv. W256 adhesion to 12(S)‐HETE‐treated RAEC demonstrated a significant increase, which was inhibited by anti‐αv, ‐β3, or ‐α_vβ₃antibodies and by 13‐HODE. Western blotting, immunoprecipitation and reverse transcription‐polymerase chain reaction indicated that W256 carcinosarcoma cells expressed αIIbβ3 integrins but not αvβ3. 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 en'dothelium by enhancing endothelial cell integrin (e.g., α_vβ₃)expression.