Pharmacological melatonin induces mitochondrial dysfunction and alters extracellular nucleotide metabolism and CD39/CD73 expression in human melanoma cells.

Cutaneous melanoma remains an aggressive malignant neoplasm characterized by molecular heterogeneity and therapeutic resistance, highlighting the need to identify alternative pathways involved in tumor progression. Purinergic signaling, particularly the conversion of extracellular ATP to immunosuppressive adenosine mediated by ectonucleotidases CD39 (NTPDase1) and CD73 (ecto-5'-nucleotidase), has emerged as a critical determinant of melanoma biology, but its potential regulation by melatonin remains unexplored.Here, we investigated whether pharmacological melatonin (0.1-5 mM, 24 and 48 h) influences metabolic activity, mitochondrial homeostasis, and extracellular nucleotide metabolism in two human melanoma cell lines with distinct molecular profiles (SK-MEL-28 and A375). Melatonin reduced metabolic activity and induced mitochondrial depolarization in both cell lines, although A375 cells exhibited greater mitochondrial sensitivity than SK-MEL-28 cells. These mitochondrial alterations were accompanied by distinct apoptosis- and inflammation-related transcriptional responses, indicating lineage-dependent cellular response to pharmacological melatonin. In parallel, melatonin differentially altered extracellular nucleotide metabolism and CD39/CD73 gene expression, with distinct responses observed between the two melanoma cell lines. Collectively, these findings indicate that the biological effects of pharmacological melatonin extend beyond mitochondrial dysfunction and involve remodeling of extracellular nucleotide metabolism, providing new evidence for an interaction between melatonergic and purinergic signaling in melanoma.