Cell cycle-dependent expression of volume-activated chloride currents in nasopharyngeal carcinoma cells

Abstract

Patch-clamping and cell image analysis techniques were used to study the expression of the volume-activated Cl− current, I Cl(vol), and regulatory volume decrease (RVD) capacity in the cell cycle in nasopharyngeal carcinoma cells (CNE-2Z). Hypotonic challenge caused CNE-2Z cells to swell and activated a Cl− current with a linear conductance, negligible time-dependent inactivation, and a reversal potential close to the Cl− equilibrium potential. The sequence of anion permeability was I− > Br− > Cl− > gluconate. The Cl− channel blockers tamoxifen, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and ATP inhibited I Cl(vol). Synchronous cultures of cells were obtained by the mitotic shake-off technique and by a double chemical-block (thymidine and hydroxyurea) technique. The expression of I Cl(vol) was cell cycle dependent, being high in G1 phase, downregulated in S phase, but increasing again in M phase. Hypotonic solution activated RVD, which was cell cycle dependent and inhibited by the Cl− channel blockers NPPB, tamoxifen, and ATP. The expression of I Cl(vol) was closely correlated with the RVD capacity in the cell cycle, suggesting a functional relationship. Inhibition of I Cl(vol) by NPPB (100 μM) arrested cells in G0/G1. The data also suggest that expression of I Cl(vol) and RVD capacity are actively modulated during the cell cycle. The volume-activated Cl− current associated with RVD may therefore play an important role during the cell cycle progress.

ClC-3 is a candidate of the channel proteins mediating acid-activated chloride currents in nasopharyngeal carcinoma cells

“…a sequence of I Ϫ Ͼ Br Ϫ Ͼ Cl Ϫ Ͼ gluconate Ϫ . These properties of the acid-induced currents were to some extent similar to those of the volume-activated Cl Ϫ current reported previously (3,19,20).…”

Involvement of regulatory volume decrease in the migration of nasopharyngeal carcinoma cells

“…The poorly differentiated nasophyaryngeal carcinoma cells (CNE-2Z) were prepared by a method described previously [12]. CNE-2Z cells were grown in culture medium (RPMI 1640 with 10% new-born calf serum, 100 IU/ml penicillin, and 100 µg/ml streptomycin) at 37ºC in a humidified atmosphere of 5% CO 2 and were subcultured every other day.…”

Re-expression of Detachment-inducible Chloride Channel mCLCA5 Suppresses Growth of Metastatic Breast Cancer Cells

“…In glioma cells (16), B lymphocytes (51), and nasopharyngeal carcinoma cells (10), Cl Ϫ currents were observed to peak in G 1 , ebb in S phase, and peak again in mitosis (10). Blockade of Cl Ϫ channels has variable effects depending on the cell type and the blocking agent.…”

“…Blockade of Cl Ϫ channels has variable effects depending on the cell type and the blocking agent. For example, cell proliferation was enhanced by chlorotoxin treatment of astrocytoma cells (15) or DIDS treatment of Schwann cells (52) or B cells (53), but channel blockade in other cell types slowed or arrested proliferation (10,11). Because of the multiplicity of Cl Ϫ channel subtypes, the lack of subtypespecific blockers, and the fact that some channels are still known only by their electrophysiological signatures, the genetic identity of the molecules responsible for these currents remains obscure (8).…”