Ion channel phenotype of melanoma cell lines

Abstract

Melanoma cells are transformed melanocytes of neural crest origin. K+ channel blockers have been reported to inhibit melanoma cell proliferation. We used whole-cell recording to characterize ion channels in four different human melanoma cell lines (C8161, C832C, C8146, and SK28). Protocols were used to identify voltage-gated (KV), Ca2+-activated (KCa), and inwardly rectifying (KIR) K+ channels; swelling-sensitive Cl- channels (Clswell); voltage-gated Ca2+ channels (CaV) and Ca2+ channels activated by depletion of intracellular Ca2+ stores (CRAC); and voltage-gated Na+ channels (NaV). The presence of Ca2+ channels activated by intracellular store depletion was further tested using thapsigargin to elicit a rise in [Ca2+]i. The expression of K+ channels varied widely between different cell lines and was also influenced by culture conditions. KIR channels were found in all cell lines, but with varying abundance. Whole-cell conductance levels for KIR differed between C8161 (100 pS/pF) and SK28 (360 pS/pF). KCa channels in C8161 cells were blocked by 10 nm apamin, but were unaffected by charybdotoxin (CTX). KCa channels in C8146 and SK28 cells were sensitive to CTX (Kd = 4 nm), but were unaffected by apamin. KV channels, found only in C8146 cells, activated at approximately -20 mV and showed use dependence. All melanoma lines tested expressed CRAC channels and a novel Clswell channel. Clswell current developed at 30 pS/sec when the cells were bathed in 80% Ringer solution, and was strongly outwardly rectifying (4:1 in symmetrical Cl-). We conclude that different melanoma cell lines express a diversity of ion channel types.