Molecular identification, localization and function of platelet-type 12-lipoxygenase in human melanoma progression, under experimental and clinical conditions.

As previous studies suggested the expression of a 12-LOX enzyme in murine and human melanoma cell lines, the primary aim of this project was to genetically identify the 12-LOX enzyme (platelet-, leukocyte- or epithelial form). By using reverse transcriptase-polymerase chain reaction, sequencing and various immunological techniques we have demonstrated conclusively the expression of the platelet-type 12-LOX in human melanoma cells of different origin, in their transplanted xenografts and in fresh human skin tumors. Furthermore, we found that p12-LOX is able to provide a survival signal for melanoma cells since inhibition of the enzyme by general LOX or selective 12-LOX inhibitors induced apoptosis in vitro. p12-LOX of human melanoma has been shown to be involved in the control of the metastatic phenotype, since we have detected the upregulation of the 12-LOX protein expression in spontaneously metastasizing xenografts and in thick human skin tumors (> 3.0 mm) characterized by high risk for the development of metastasis. Co-expression of two megakaryocytic genes, p12-LOX and alphaIIb integrin chains, was found to be a frequent phenomenon in human melanoma (approximately 70%) suggesting a common regulatory defect in this tumor.