1, 25-Dihydroxyvitamin D3 alters ectonucleotidase expression and activity in human cutaneous melanoma cells

PurposeWe hypothesized that vitamin D decreases rates of adenosine formation in human cutaneous melanoma cells through the inhibition of extracellular adenosine 5-triphosphate breakdown, thereby affecting tumor cell viability. Therefore, the objective of this study was to explore the mechanisms of action of 1, 25-dihydroxyvitamin D3 (1,25(OH)(2)D3) on the activity and expression of ectonucleotidases in cutaneous melanoma cells. MethodsA human melanoma cell line, SK-Mel-28, was treated with 1 to 50nM of the active vitamin D metabolite (1,25(OH)(2)D3) over 24hours, followed by determination of NTPDase1/CD39 and ecto-5-nucleotidase/CD73 activity and expression rates of the purinergic system-related NTPDASE1, NT5E and adenosine deaminase and vitamin D receptor. An 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay was used to evaluate cellular viability. Results1,25(OH)(2)D3 decreased adenosine monophosphate hydrolysis via ecto-5-nucleotidase/CD73 and expression of CD73, but did not change NTPDase1/CD39 activity; it increased the CD39 expression. We also observed an increase of cell viability at 1nM, but this viability decreased as the concentrations of vitamin D active metabolite increased to 50nM. There were no differences in gene expression levels. ConclusionTo the best of our knowledge, we showed for the first time a mechanism of control of adenosine production via modulation of the purinergic system in cutaneous melanoma cells treated with the active metabolite of vitamin D. This study provides original information regarding mechanisms, in which vitamin D plays a key role in preventing tumor progression in human melanoma cells.