CONICET | Buscador de Institutos y Recursos Humanos

Malignant melanoma is a rapidly spreading skin tumour with a very high invasive capacity and the incidence continues increasing globally. Melanoma cells but not normal melanocytes contain large amounts of histamine that has been found to accelerate malignant growth. It was previously reported the expression of the histamine H1, H2, and H3 receptors in melanoma cell lines. In addition, histamine modulates proliferation in a dose dependent manner in WM35 cells. The aim of this work was to investigate the presence of histamine H4 receptor (H4R) in WM-35 cells (human primary melanoma cell line) and its associated biological processes. The expression of H4R was analyzed by RT-PCR and immunocytochemistry. To characterize the biological responses we evaluated cell proliferation by the clonogenic, crystal violet and MTT cell viability assays. In addition, cell senescence and differentiation were determined by Ò-galactosidase enzyme assay and dopa oxidase activity, respectively. Apoptosis was studied by Annexin-V staining and flow cytometry. Results indicate that WM-35 cells express H4R at the mRNA and protein level. By using specific histamine agonists and antagonists we determined that the inhibitory effect of histamine on proliferation is in part mediated through the stimulation of the H4R (VUF 8430 IC50=1.9 £gM, Clobenpropit IC50= 1.7 £gM). The decrease in proliferation was associated with an induction of cell senescence and an increase in melanogenesis that is a differentiation marker of these cells. To our knowledge this is the first report that describes the presence of the H4R in WM35 melanoma cells. We conclude that the H4R is involved in the regulation of cell proliferation and senescence, which represent key processes involved in tumor progression.

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