Differential expression of volume‐regulated anion channels during cell cycle progression of human cervical cancer cells

Abstract

This study investigated the volume-regulated anion channel (VRAC) of human cervical cancer SiHa cells under various culture conditions, testing the hypothesis that the progression of the cell cycle is accompanied by differential expression of VRAC activity. Exponentially growing SiHa cells expressed VRACs, as indicated by the presence of large outwardly rectifying currents activated by hypotonic stress with the anion permeability sequence I- > Br- > Cl-. VRACs were potently inhibited by tamoxifen with an IC50 of 4.6 [mu]M. Fluorescence-activated cell sorting (FACS) experiments showed that 59 +/- 0.5, 5 +/- 0.5 and 36 +/- 1.1% of unsynchronized, exponentially growing cervical cancer SiHa cells were in G0/G1, S and G2/M stage, respectively. Treatment with aphidicolin (5 [mu]M) arrested 88 +/- 1.4% of cells at the G0/G1 stage. Arrest of cell growth in the G0/G1 phase was accompanied by a significant decrease of VRAC activity. The normalized hypotonicity-induced current decreased from 48 +/- 5.2 pA pF-1 at +100 mV in unsynchronized cells to 15 +/- 2.6 pA pF-1 at +100 mV in aphidicolin-treated cells. After removal of aphidicolin, culturing in medium containing 10% fetal calf serum triggered a rapid re-entry into the cell cycle and a concomitant recovery of VRAC density. Pharmacological blockade of VRACs by tamoxifen or NPPB caused proliferating cervical cancer cells to arrest in the G0/G1 stage, suggesting that activity of this channel is critical for G1/S checkpoint progression. This study provides new information on the functional significance of VRACs in the cell cycle clock of human cervical cancer cells.

Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance

“…[56][57][58][59] In several cell types it is found that VRAC is regulated throughout the cell cycle and that VRAC inhibitors obstruct cell proliferation. [60][61][62] In particular, changes in VRAC activity seem important for the G 1 /S transition phase and many cells are halted in the G 1 phase by Cl -channel inhibitors. [63][64][65][66][67][68][69] It should be noted that conclusions about VRAC and cell cycle generally rely on data obtained with pharmacological compounds with low selectivity / specificity and should be reinvestigated now that essential components of VRAC have been cloned.…”

Biophysical and pharmacological characterization of hypotonically activated chloride currents in cortical astrocytes

“…Shen et al, 2000;Wondergem et al, 2001). In different cell types, these currents have been given several names, including volume-activated Cl -currents (I Cl,vol ) (Nilius et al, 1994(Nilius et al, , 1996, swellingactivated Cl -currents (ICl,swell) (Ackerman et al, 1994a, b;Krapivinsky et al, 1994), or volume-regulated anion currents (VRAC) (Hubert et al, 2000;Levitan et al, 2000).…”

A Novel Function of BCL-2 Overexpression in Regulatory Volume Decrease

“…amino acids) that are required for cell growth (1,4). We found previously (17) that the differential expressions of swellingactivated Cl Ϫ channel associated with the cell cycle progression. The malignant transformation of human cervical epithelial cells is accompanied by the significant up-regulation of swelling-activated Cl Ϫ channel (27,28).…”

“…Electrophysiological Measurements-The whole-cell mode of the patch clamp technique was used to measure membrane currents as described previously (17). Cells were bathed at room temperature (22-25°C) and continuously superfused with isotonic or hypotonic solution.…”