Roles of volume-activated Cl- currents and regulatory volume decrease in the cell cycle and proliferation in nasopharyngeal carcinoma cells

Objectives: Previously it has been shown, that the volume-activated plasma membrane chloride channel is associated with regulatory volume decrease (RVD) of cells and may play an important role in control of cell proliferation. We have demonstrated that both expression of the channel and RVD capacity are actively regulated in the cell cycle. In this study, we aimed to further study the role of the volume-activated chloride current and RVD in cell cycle progression and overall in cell proliferation. Materials and methods: Whole-cell currents, RVD, cell cycle distribution, cell proliferation and cell viability were measured or detected with the patch-clamp technique, the cell image analysis technique, flow cytometry, the MTT assay and the trypan blue assay respectively, in nasopharyngeal carcinoma cells (CNE-2Z cells). Results: The Cl- channel blockers, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen, inhibit the volume-activated chloride current, RVD and proliferation of CNE-2Z cells in a dose-dependent manner. Analysis of relationships between the current, RVD and cell proliferation showed that both the current and RVD were positively correlated with cell proliferation. NPPB (100 mu M) and tamoxifen (20 mu M) did not significantly induce cell death, but inhibited cell proliferation, implying that the blockers may inhibit cell proliferation by affecting cell cycle progression. This was verified by the observation that tamoxifen (20 mu M) and NPPB (100 mu M) inhibited cell cycle progress and arrested cells at the G(0)/G(1) phase boundary. Conclusions: Activity of the volume-activated chloride channel is one of the important factors that regulate the passage of cells through the G(1) restriction point and that the Cl- current associated with RVD plays an important role in cell proliferation.