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Stefan Mergler, Arina Boehm, Raissa Derckx, Lisa Schmelzer, Fabian Garreis, Aline Riechardt, ; Calcium regulation by transient receptor potential channels in human uveal melanoma cells. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4204.
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© ARVO (1962-2015); The Authors (2016-present)
Uveal melanoma (UM) is not only the most common primary intraocular cancer, but also the leading primary intraocular disease being fatal in adults. Differences in transient receptor potential channels (TRPs) and cannabinoid receptor type 1 (CB1) expression levels can serve as prognostic factors for uveal melanoma (UM) tumor progression. Here, we postulated that such differences indicate characteristics of UM tissue or healthy human uvea tissue. Therefore, we investigated in malignant human UM and healthy uvea putative TRP channel and CB1 gene expression and their functional activity.
Gene and protein expression was investigated by RT-PCR and immunohistochemistry in various human UM cell lines and human uvea. Intracellular free Ca2+ ([Ca2+]i) was measured in fura2-loaded UM cells, which were kindly provided by M. Jager et al., Leiden University (Netherlands). Whole-cell currents were measured by the planar patch-clamp technique.
RT-PCR analysis revealed TRPV1, TRPM8 and CB1 expression in UM cells. TRPA1 was highly expressed in human uvea but not in all UM cell lines. Capsaicin (CAP) increased whole-cell currents (Fig. 1). The cooling agents menthol (500 µM)/icilin (20-50 µM) or moderate cooling (18 °C) increased [Ca2+]i and whole-cell currents, which could be blocked by the TRPM8 channel blocker BCTC (10 µM). Notably, CAP-induced Ca2+ influxes could be suppressed by capsacepine (CPZ) (20 µM) or by activation of CB1 (10 µM WIN55,212-2) (WIN). Furthermore, 10 µM WIN induced outwardly rectifying whole-cell currents (Fig. 2).
This study demonstrates for the first time functional expression of TRPV1, TRPM8 and TRPA1 subtype and CB1 in UM cells as well as a CB1-TRPV1 communication. This may promise to improve and extend of the arsenal of diagnostic and therapeutic tools available to date in this aggressive neoplastic disease by utilizing TRPs.
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