ENDOGENOUS 12(S)-HETE - PRODUCTION BY TUMOR-CELLS AND ITS ROLE IN METASTASIS

12(S)-Hydroxyeicosatetraenoic acid [12(S)-HETE] is the 12-lipoxygenase metabolite of arachidonic acid. Previously, we have demonstrated that exogenous 12(S)-HETE can activate protein kinase C, increase cell sur face expression of integrins, enhance adhesion, induce endothelial cel l retraction, and increase experimental metastasis of tumor cells. Bec ause of these prominent effects of exogenous 12(S)-HETE on tumor cell metastatic potential, it is important to determine whether there is en dogenous 12(S)-HETE production by tumor cells. In the present study, m RNAs from human, rat, and mouse platelets as well as human colon carci noma (Clone A), rat Walker carcinoma (W256), and mouse melanoma (B16a) and lung carcinoma (3LL) were reverse transcribed and amplified by po lymerase chain reaction with platelet 12-lipoxygenase specific primers . Identity of the polymerase chain reaction fragments was confirmed by sequencing. 12-lipoxygenase protein was detected by Western blotting. Tumor cell-derived 12-HETE was determined by reverse phase-high perfo rmance liquid chromatography analysis. In addition, the effect of endo genous 12(S)-HETE on tumor cells was studied by using a platelet-type 12-lipoxygenase selective inhibitor (N-benzyl-N-hydroxy-5-phenylpentan amide). Our results suggest that some tumor cells express platelet-ape 12-lipoxygenase mRNA, protein and metabolize arachidonic acid to 12(S )-HETE and that endogenous 12(S)-HETE, like the exogenous 12(S)-HETE, may play an important role in tumor cell adhesion to matrix in vitro a nd lung colonization in vivo.