l-663536 and Melanoma

To study the effect of 5-lipoxygenase inhibitors on the expression of intercellular adhesion molecule-1 (ICAM-1) in melanoma cells.. ICAM-1 protein of human melanoma cell a375 was detected by enzyme-linked immunosorbent, flow cytometry and Western blot analysis. Level of ICAM-1 mRNA in a375 was evaluated by Northern blot analysis. Adhesion of a375 to endothelial cell EC304 was analyzed by isotopic tracing.. 5-Lipoxygenase inhibitors nordihydroguaiaretic acid, AA861 and MK886, could suppress the expression of ICAM-1 protein as well as of its mRNA in a375 cells and reduce the adhesion of a375 to EC304.. 5-Lipoxygenase inhibitors can inhibit the expression of ICAM-1 in human melanoma cells and may be valuable for treatment of melanoma metastasis.

Topics: Benzoquinones; Cell Adhesion; Cells, Cultured; Endothelial Cells; Humans; Indoles; Intercellular Adhesion Molecule-1; Lipoxygenase Inhibitors; Masoprocol; Melanoma; RNA, Messenger; Tumor Cells, Cultured; Umbilical Veins

We examined the synthesis of leukotrienes (LTs) in human melanoma cells in order to assess the function of LTs in human melanocytes. LTA4 hydrolase, which catalyzes the conversion of LTA4 to LTB4, was detected in the supernatant of cultured human melanoma (MeWo) cells and melanoma cells obtained from patients. Immunoblotting analysis using an antihuman LTA4 hydrolase antibody showed LTA4 hydrolase to be a 70-kDa protein in both MeWo and melanoma cells. Considerable activity of LTC4 synthase, which catalyzes the conversion of LTA4 to LTC4, was detected in the microsomal fraction of both MeWo and melanoma cells. The HPLC profile of the LTC4 synthase reaction products revealed that LTC4 was the main product. LTD4 was not detected under these conditions, indicating that the microsomal fraction of human melanoma cells lacks the membrane-bound gamma-glutamyl transferase that converts LTC4 to LTD4. LTC4 synthase activity was inhibited by the addition of MK-886, and was not altered by treatment with N-ethylmaleimide or 1-chloro-2,4-dinitrobenzene. These results indicate that the enzyme responsible for the conversion of LTA4 to LTC4 in human melanoma cells is LTC4 synthase rather than a nonspecific or microsomal glutathione-S-transferase. These results also suggest that human melanoma cells can generate LTB4 and LTC4 from LTA4, and that this process is catalyzed by two enzymes: LTA4 hydrolase and LTC4 synthase.

Topics: Dinitrochlorobenzene; Enzyme Inhibitors; Epoxide Hydrolases; Ethylmaleimide; Glutathione Transferase; Humans; Indoles; Leukotriene A4; Leukotriene B4; Leukotriene C4; Leukotriene D4; Melanoma; Microsomes; Tumor Cells, Cultured

Metastasis is a complex process, almost a cascade, involving multiple steps and activities. However, an important factor is that malignant cells are able to penetrate through the multiple basement membrane barriers surrounding tissues, blood vessels, nerves and muscle that would otherwise block their dissemination. Penetration of malignant tumor cells through basement membrane is an active process requiring proteolysis. We report here that inhibitors of both the cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism convert mouse melanoma and human fibrosarcoma cells to a non invasive state by reducing the production of MMP-2, an enzyme required for the degradation of basement membranes. Specific metabolites of each pathway, i.e. PGF2 alpha and 5-HPETE, are able to transcend the block and restore collagenase production, invasiveness in vitro and metastatic activity in vivo. These studies indicate a key role for arachidonic acid metabolites in metastasis and suggest novel therapeutic approaches for inhibiting the spread of cancer.

Topics: Animals; Arachidonic Acid; Caffeine; Collagen; Cyclooxygenase Inhibitors; Dinoprost; Drug Combinations; Extracellular Matrix; Fibrosarcoma; Gelatinases; Humans; Indoles; Indomethacin; Laminin; Leukotrienes; Lipoxygenase Inhibitors; Masoprocol; Matrix Metalloproteinase 2; Melanoma; Metalloendopeptidases; Mice; Neoplasm Metastasis; Proteoglycans; Tumor Cells, Cultured; Umbelliferones