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Elena Rodriguez de Turco, Nicholas Delamere, Mohammad Shahidullah; Unusual sodium-potassium dynamics and Na,K-ATPase expression in Mel-290 uveal melanoma cells. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4205.
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© ARVO (1962-2015); The Authors (2016-present)
Uveal melanoma is a common malignant intraocular tumor and metastasis is frequent. The mortality for metastatic uveal melanoma approaches 90 %. Here we report on abnormal sodium-potassium dynamics in a particular uveal melanoma cell line, Mel-290.
Melanoma cells were cultured in RPMI 1640 medium supplemented with 10% FBS, 3mM glutamine and 2% penicillin + streptomycin. The ratio of cell sodium concentration to potassium concentration was determined by atomic absorption spectrometry. Abundance of Na,K-ATPase and other proteins was examined by western blot analysis.
The Na:K concentration ratio in Mel-290 cells was 0.57 compared to 0.1 in a different melanoma cell, OCM-3, and 0.15 in pig ciliary epithelium. Assuming cell Na+K = 140 mM, the resting sodium concentration in Mel-290 cells is approximately 50 mM which is several fold higher than the concentration in normal cells. Western blot studies showed lower abundance of Na,K-ATPase alpha 1 subunit protein in Mel-290 compared to OCM-3. Differences in Na,K-ATPase alpha subunit phosphorylation also were observed. In contrast to Na,K-ATPase, the abundance of H/K-ATPase beta subunit and H-ATPase (v-ATPase) beta subunit was higher in Mel-290 compared to OCM-3. A high Na:K ratio was detected in two other melanoma cell types, suggesting the possible existence of a high sodium sub-group of melanomas.
Certain uveal melanoma cells display a high-sodium phenotype. It is interesting that high cytoplasmic sodium has been reported in certain liver, brain and breast tumors by MRI and other techniques. It remains to be determined whether the high-sodium phenotype is related to a particular pattern of ATPase expression or regulation.
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