Molecular mechanism underlining ethanol-induced chloride currents in nasopharyngeal carcinoma cells

AIM：To study the effects and mechanisms of ethanol on chloride channels in poorly differentiated nasopharyngeal carcinoma CNE-2Z cells. METHODS：The effect of ethanol on the cell growth was analyzed by MTT assay. The technique of whole-cell patch-clamp was used to detect the chloride current. The characteristics of the chloride current were analyzed by using the chloride channel blockers. The siRNA technique was used to analyze the molecular basis of the ethanol-sensitive chloride channels. RESULTS：Under isotonic conditions, the background current was weak and stable. Ethanol at concentrations of 0.17~170 mmol/L activated a chloride current in a concentration-dependent manner (an inverted U-shape), with a maximum effect at the concentration of 17 mmol/L. The currents showed obviously outward rectification and were susceptible to extracellular hypertonicity and the chloride channel blocker, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). ClC-3 siRNA obviously decreased the currents activated by ethanol. CONCLUSION：Extracellular ethanol induces chloride currents through activating the ClC-3 chloride channels.     

Knockdown of IK1 potassium channel inhibits expression and function of ClC-3 chloride channel

AIM: To investigate whether the ClC-3 chloride channel is an acting target of the IK1 potassium channel, and to study the action of IK1 potassium channel on the functional activities and expression of ClC-3 chloride channels. METHODS: IK1 gene was silenced by IK1 siRNA in poorly-differentiated nasopharyngeal carcinoma cells (CNE-2Z). Real-time PCR and Western blot were used to detect the expression of ClC-3 at mRNA and protein levels. The distribution of ClC-3 protein in the cells was observed under confocal immunofluorescence microscope. The chloride current was recorded by the patch-clamp technique. RESULTS: IK1 siRNA was successfully transfected into the CNE-2Z cells and knocked down the expression of IK1 potassium. The mRNA expression of ClC-3 was increased by the IK1 siRNA. IK1 siRNA inhibited the expression of ClC-3 protein. A chloride current was activated by hypotonic challenges, and the hypotonicity-induced current was reduced in the cells which successfully transfected with IK1 siRNA. CONCLUSION: The knockdown of IK1 potassium channels inhibits the expression and function of ClC-3 chloride channel.     

Inhibition of cell proliferation and arrest of cell cycle progression by blocking Cl- channels in nasopharyngeal carcinoma cells

AIM: The roles of Cl^-channels in regulatory volume decrease (RVD), cell proliferation and cell cycle progression in nasopharyngeal carcinoma cells (CNE-2Z) were investigated. METHODS: Image analysis of living cells was used to detect the volume changes following exposure to hypotonic solutions. Cell viability was determined by the trypan blue assay. MTT method was applied to detected cell proliferation. The effect of the blocker on the cell cycle distribution was monitored by the flow cytometry. RESULTS: 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) inhibited RVD and cell proliferation in a dose-dependent manner. NPPB at the concentration of 100 μmol/L arrested cells in G₁ phase (G₁ population increased from 54% to 71% at 48 h after treatments), but did not significantly alter cell viability. CONCLUSION: Block of chloride channels suppressed cell proliferation by arresting cells in G₁ phase. The results suggest that activation of Cl^-channels and RVD is necessary for facilitating cells to proceed to the S phase from G₁ phase and maintaining cell proliferation.     

Inhibitory role of epigallocatechin-3-gallate in proliferation of human nasopharyngeal carcinoma cells by targeting P53/miR-34a

AIM: To study the effect of epigallocatechin-3-gallate(EGCG) on the proliferation of human nasopharyngeal carcinoma(NPC) cells, and to explore its mechanism by targeting miR-34a.METHODS: Nasopharyngeal carcinoma CNE-2Z cells were treated with various concentrations of EGCG. The ability of cell proliferation was detected by CCK-8 assay, 5-ethynyl-2-deoxyuridine(EdU) incorporation assay and colony-forming assay. The cell cycle distributions were analyzed by flow cytometry. The protein levels of P53 and Notch1 were detected by Western blot. The expression of miR-34a and Notch1 mRNA was measured by real-time PCR.RESULTS: EGCG effectively inhibited the proliferation and colony formation of CNE-2Z cells in a dose-dependent manner, which was related to its induction of cell cycle arrest at G₀/G₁ phase. The expression of P53 and miR-34a in CNE-2Z cells was significantly increased after treated with EGCG, while the expression of Notch1 at mRNA and protein levels was markedly suppressed.CONCLUSION: EGCG induces cell cycle arrest and suppresses cell proliferation by regulating the P53/miR-34a/Notch1 pathway in NPC cells.     

Roles of chloride channels in the migration of nasopharyngeal carcinoma cells at different stages of the cell cycle

AIM: To clarify the migration capability of nasopharyngeal carcinoma cells (CNE-2Z) at different stages of the cell cycle and the roles of chloride channels in cell migration. METHODS: Synchronous cells were obtained by the serum deprivation，double chemical-block, mitotic arrest and shake-off techniques. Cell cycle distribution of CNE-2Z cells was analyzed by the flow cytometry. Migration rate was assayed by transwell chambers and by image analysis. The cytotoxicity of chemicals on cells was tested by MTT assay. RESULTS: CNE-2Z cells at different stages of the cell cycle exhibited different migratory ability. The migration rate of the three stages was G1>M> S. The migration of CNE-2Z cells was inhibited by chloride channel blockers (ATP, NPPB and tamoxifen), but the inhibitory effect of the blockers varied with cells at different stages. CONCLUSIONS: The migratory ability is associated with the cell cycle in CNE-2Z cells. Chloride channels play an important role in cell migration of CNE-2Z cells.     

Effect of protein kinase C-α antisense oligonucleotide on cell cycle of CNE-2Z cells

AIM:To observe the effect of protein kinase C-α(PKCα)antisense oligonucleotide on cell growth, cell cycle and the expression of cyclin E in human poor-differentiated nasopharyngeal carcinoma(NPC) cell line CNE-2Z. METHODS:Antisense PKCα was transfected by cationic liposome(LP) in CNE-2Z cells to analyze the cell growth and cell cycle by MTT colorimetric assay and flow cytometry, respectively. Moreover, the expression of cyclin E was determined by immunocellularchemistry and scanning the result of dot-blotting. RESULTS:①With the concentration of antisense PKCα increasing, the relative cell growth index was decreased gradually(P＜0.01). ②After treated with antisense PKCα, the percentage of cells in G₁ phase enhanced(P＜0.05). ③Compared with the control group, the expressing intensity of cyclin E reduced in antisense PKCα group, and the expression of cyclin E decreased to 66.5%±18.4％(P＜0.05) of the control by scanning quantitative analysis. CONCLUSION:These results indicated that antisense PKCα may inhibit cell growth in CNE-2Z via suppressing the expression of cyclin E and hindering cell process in G₁ phase.     

Chloride currents activated by cisplatin in poorly differentiated naso-pharyngeal carcinoma cells are not Ca2+-activated chloride currents

AIM：To investigate the type of chloride channel activated by cisplatin in poorly differentiated nasopharyngeal carcinoma cells (CNE-2Z cells). METHODS：The technique of whole-cell patch-clamp was used to investigate the role of Ca2+ in the activation of cisplatin-activated chloride currents and to analyze the effect of hypertonic stress on these currents in CNE-2Z cells. RESULTS：Chloride currents were induced when the cells were exposed to the calcium-free cisplatin solution, showing the similar density to the currents induced by cisplatin with the presence of extracellular calcium. However, the latency and the peak time of cisplatin-activated currents in the absence of extracellular calcium were prolonged. The activation of cisplatin-activated chloride currents was insensitive to the depletion of intra- and extracellular calcium. Calcium channel antagonist nifedipine had no effect on the cisplatin-activated chloride currents, while hypertonic solution completely inhibited those currents. CONCLUSION：The cisplatin-activated chloride currents are independent on intra/extracellular calcium. The chloride channels activated by cisplatin are not calcium-activated chloride channels, but are probably volume-sensitive chloride channels.     

Bufalin activates chloride channels in poorly differentiated nasopharyngeal carcinoma cells

AIM: To investigate the activation of chloride channels induced by bufalin and the properties of the channels in poorly differentiated nasopharyngeal carcinoma (CNE-2Z) cells. METHODS: The technique of whole-cell patch clamp was used to record the chloride currents and to analyze the characteristics of the currents in CNE-2Z cells.RESULTS: A chloride current was slowly activated by extracellular application of bufalin (1 μmol/L). The activation of the current was slower than that of the volume-activated chloride current, with an activation latency of(12.1±6.4) min. The reversal potential of the current was close to the calculated Cl^- equilibrium potential (E_Cl =-0.9 mV). The chloride current was outward-rectified and did not show significant time-dependent or voltage-dependent inactivation. The chloride channel blocker tamoxifen completely inhibited the outward and inward currents. The current was also completely inhibited by extra-cellular application of 47% hypertonic solution. CONCLUSION: Bufalin activates chloride channels and induces a chloride current in CNE-2Z cells. Compared with the volume-activated chloride current in CNE-2Z cells, the activation latency of the bufalin-induced current is longer and the outward rectification is more obvious.     

Effect of ClC-3 siRNA on cell cycle of HeLa cells

AIM: To investigate the roles of ClC-3 chloride channels in the regulation of cell cycle and the relationship between ClC-3 chloride channels and the cell cycle regulators, such as cyclin D1, cyclin-dependent kinase (CDK)4, CDK6, P21 and P27 in the HeLa cells.METHODS: ClC-3 genes were silenced by the siRNA technique in the HeLa cells. The transfection efficiency of ClC-3 siRNA was detected by real-time PCR. The cell cycle distribution was analyzed by the flow cytometry. The protein expression of ClC-3, P21, P27, CDK4, CDK6 and cyclin D1 was determined by Western blot.RESULTS: ClC-3 was knocked down by ClC-3 siRNA in the HeLa cells. Transfection of the cells with ClC-3 siRNA arrested the cells at G₀/G₁ phases, decreased the expression of cyclin D1, CDK4 and CDK6, and increased the expression of P21 and P27.CONCLUSION: ClC-3 plays an important role in the cell cycle of HeLa cells through the G₁-S transition point. ClC-3 may regulate the cell cycle progression by up-regulation of cyclin D1, CDK4 and CDK6 expression and/or by down-regulation of P21 and P27 expression.     

Effects of curcumin analogue B50 on proliferation and apoptosis of homologous nasopharyngeal carcinoma cells with different radioresistance

AIM: To compare the effects of B50, a mono-carbonyl analogue of curcumin, on the proliferation and apoptosis between homologous nasopharyngeal carcinoma cells CNE-2R and CNE-2 with different radioresistance.METHODS: The effects of B50 on cell viability and cell growth were detected by MTT assay and colony-forming experiment, respectively. The changes of cell cycle, apoptosis and mitochondrial membrane potential (MMP) were determined by flow cytometry.RESULTS: B50 inhibited the cell viability of CNE-2R cells in a time-and dose-dependent manner with the IC₅₀ of (8.06±0.14) μmol/L (24 h), (2.49±0.02)μmol/L (48 h) and (1.42±0.02) μmol/L (72 h), which was more effective than that in CNE-2 cells . The inhibitory effect of B50 on CNE-2R cell growth was more effective than that on CNE-2 cells . After treated with B50 for 48 h, the proportion of CNE-2R cells in G₂/M stage was increased from 7.1% to 34.9%, which was better than that of CNE-2 cells (from 12.4% to 35.7%). After treated with B50 for 24 h, the early apoptotic rate in CNE-2R cells was increased from 3.7% to 19.5%, which was better than that in CNE-2 cells (from 4.4% to 14.8%), and the MMP in CNE-2R cells was decreased by (43.17±3.11)%, which was better than that in CNE-2 cells .CONCLUSION: B50 is more effective on inhibiting the cell viability and cell growth, blocking the cell cycle at G₂/M stage, inducing apoptosis and decreasing MMP in CNE-2R cells than those in CNE-2 cells, indicating that B50 may enhance the radio-sensitivity of CNE-2R cells by blocking the cell cycle and inducing apoptosis through mitochondrial pathway.     

Curcumin analogue B67 induces apoptosis and G2/M arrest to suppress radioresistant nasopharyngeal carcinoma cells

AIM: To study the effect of curcumin analogues B67 on radioresistant nasopharyngeal carcinoma cells (CNE-2R). METHODS: The effects of B67 on the cell viability and proliferation of CNE-2R and the parent cells CNE-2 were detected by MTT assay and colony formation assay, respectively. The changes of cell cycle, apoptosis and mitochondrial membrane potential were determined by flow cytometry. The morphological changes of the cells were observed under fluorescence microscope. Node mice were subcutaneously inoculated with the cells to determine the tumorigenic ability. RESULTS: The IC₅₀ of B67 on the viability of CNE-2R cells after treatment for 24 h, 48 h and 72 h were 3.96,2.59 and 0.89 μmol/L, respectively, and those of CNE-2 cells were 8.84, 3.55 and 1.10 μmol/L,respectively. The IC₅₀ of B67 on the proliferation of CNE-2R cells after treatment for 48 h was 0.55 μmol/L, and that of CNE-2 cells was 0.73 μmol/L. After treated with B67 for 24 h, CNE-2R and CNE-2 cells at G₂/M stage increased from 5.32% to 40.01% and from 9.07% to 15.73%,respectively. After treated with B67 for 48 h, the apoptosis of CNE-2R and CNE-2 cells increased from 5.49% to 38.06% and from 4.99% to 35.74%, respectively. The mitochondrial membrane potential in CNE-2R and CNE-2 cells was decreased by 66.76% and 72.09%, respectively. After treated with B67 for 24 h, the tumorigenic rate of CNE-2R cells was 0%, while the rates of CNE-2 cells in low- and high-concentration groups were 100% and 0%, respectively.CONCLUSION: Curcumin analogue B67 exhibits enhanced suppressive activity on radioresistant nasopharyngeal carcinoma cells by inducing G₂/M-phase arrest, promoting cell apoptosis and changing mitochondrial membrane potential.     

Chloride currents activated by cisplatin in nasopharyngeal carcinoma cells

AIM: To study the activation and the properties of chloride channels activated by the antineoplastic agent cisplatin (cDDP) in nasopharyngeal carcinoma (CNE-2Z) cells. METHODS: The whole-cell patch clamp technique was used to record chloride currents. The characteristics of the channel were investigated using ion-exchange and pharmacological methods. RESULTS: A chloride current was activated by extracellular application of cDDP (5 μmol/L). The current showed significant outward rectification. The reversal potential of the current was close to the calculated equilibrium potential for Cl-(ECl=-0.9 mV). The activation of the chloride channel was dependent on the existence of the intracellular ATP. The permeability sequence of the four anions was I-≥Br->Cl->gluconate. The current was almost completely inhibited by extracellular application of chloride channel blocker tamoxifen (30 μmol/L). CONCLUSION: Antineoplastic agent cDDP can activate a chloride channel with characteristics similar to the volume-activated chloride channel in CNE-2Z cells.     

Effects of tamoxifen on volume-activated Cl- currents of nasopharyngeal carcinoma cells at different stages of the cell cycle

AIM:To investigate the inhibitory effects of Cl- channel blocker, tamoxifen, on volume-activated Cl- currents of nasopharyngeal carcinoma cells (CNE-2Z cells) in G₁ and S phases. METHODS:Highly synchronous cells in G₁ phase and S phase were obtained by the serum starvation and the double-block techniques. The whole-cell patch clamp technique was used to observe the effects of tamoxifen on volume-activated Cl- currents and to analyze the anion permeability of volume-activated Cl- channels. RESULTS:47% hypotonic stimulation activated a Cl- current in the nasopharngeal carcinoma cells at the cell cycle stage G₁ phase and S phase. Tamoxifen at concentration of 10 to 30 μmol/L completely inhibited the current. However, the time needed to completely inhibit the current was dose-dependent and was different between G₁ phase and S phase. The time needed to completely inhibit the current was shorter in G₁ cells than that in S phase cells. The anion permeability sequence of the volume-activated Cl- channel was I->Cl->gluconate in both G₁ phase and S phase cells. The permeability of G₁ phase cells to I- was higher than that in S phase cells, but to gluconate was lower than that in S phase cells. CONCLUSIONS:The density of the volume-activated Cl- current, the anion permeability of the channel and the sensitivity of the current to tamoxifen were different between the CNE-2Z cells in G₁ phase and those in S phase. The results suggest that the expression of tamoxifen-sensitive, volume-activated chloride channels is differentiated at different stages of the cell cycle.     

Osmolarity,cell volume and proliferation in nasopharyngeal carcinoma cells

AIM: To investigate the relationship between osmolarity, cell volume and cell proliferation in nasopharyngeal carcinoma cells. METHODS: MTT method was applied to detect the proliferation ability of the poorly-differentiated nasopharyngeal carcinoma cell (CNE-2Z) under various osmolarity conditions. The flow cytometry was used to analyse cell cycle distribution. Cell volume was obtained by the image analysis of living cells and cell viability was determined by the trypan blue assay. RESULTS: Cultivation of cells under the hypertonic conditions of 370 and 440 mOsmol/L increased cell volume by 8.7% and 27.8% and facilitated cell proliferation by 22.2% and 33.9%, respectively. However, hypotonic incubation of cells with osmolarity of 160 and 230 mOsmol/L decreased cell volume by 12.8% and 4.1% and inhibited cell proliferation by 34.0% and 15.6%, respectively. Cell volume was positively correlated with cell proliferation rate. Long-term cultivation of cells under anisotonic conditions did not significantly alter cell cycle distribution, but hypotonic cultivation decreased cell viability. CONCLUSION: Proliferation of nasopharyngeal carcinoma cells was closely correlated with the osmolarity of culture medium and cell volume. Hypotonic cultivation may inhibit cell proliferation by decreasing cell volume to facilitate cell death mechanisms.     

Effect of metformin combined with paclitaxel on apoptosis and AMPK signaling in human breast cancer cells

AIM:To investigate the effect of metformin combined with paclitaxel on the viability and apoptosis of breast cancer cell line MCF-7 and its possible mechanism. METHODS:MCF-7 cells were treated with metformin at different concentrations (2, 5, 10, 20, 40 and 80 mmol/L) and in vitro cultured. The viability of MCF-7 cells was measured by MTT assay. Metformin at 2 mmol/L or paclitaxel at 2.4 mg/L alone or in combination was used to treat the cells, and compound C, an inhibitor of adenosine monophosphate-activated protein kinase (AMPK) signaling transduction pathway, was also used. The cells were divided into control group, metformin group, paclitaxel group, combination group, and combination +compound C group. The apoptosis of the cells was analyzed by flow cytometry. The expression of Bax, Bcl-2 and caspase-3 at mRNA and protein levels was determined by RT-qPCR and Western blot. The protein levels of AMPK and P21 were examined by Western blot. RESULTS:Metformin at different concentrations (2, 5, 10, 20, 40 and 80 mmol/L) significantly inhibited the cell viability in a concentration-dependent manner (P<0.05). Compared with control group, treatment with metformin at 2 mmol/L or paclitaxel at 2.4 mg/L alone or in combination significantly inhibited the cell viability, induced apoptosis (P<0.05), decreased the level of Bcl-2 (P<0.05), increased the levels of Bax and caspase-3 (P<0.05), and promoted the protein expression of AMPK and P21 (P<0.05). The effects of metformin and paclitaxel in combination were better than those of single drug treatment, while AMPK inhibitor weaken these effects. CONCLUSION:Metformin combined with paclitaxel inhibits the viability and induces the apoptosis of breast cancer MCF-7 cells by activating AMPK signaling pathway and regulating apoptosis signaling pathway.     

Role of Cl- in regulatory volume decrease of nasopharyngeal carcinoma cells

AIM:To clarify the role of Cl^- in regulatory volume decrease (RVD) of nasopharyngeal carcinoma cells (CNE-2Z).METHODS:Analysis of living cell images was used to detect the volume changes following exposure to hypotonic solution. Iron replacement and block of iron channels were also applied in the present study. RESULTS:Extracelluar hypotonic treatment made the cells swell and induced RVD. The RVD was correlated positively to the swelling in the range of 160-230 mOsmol/L. Substitution of gluconate for Cl^- in perfusing solutions markedly increased RVD. Depletion of cellular Cl^- abolished, and chloride channel blockers inhibited RVD. CONCLUSION:Cl^- is the key iron to establish the RVD in CNE-2Z cells. Activation of Cl^- channels and Cl^- efflux are the major mechanisms of RVD.     

High expression of Axl promotes clinical progression of nasopharyngeal carcinoma

AIM: To explore the expression and significance of receptor tyrosine kinase anexelekto (Axl) in nasopharyngeal carcinoma (NPC). METHODS: Immunohistochemistry was used to detect the Axl protein expression of 78 patients with NPC and 32 patients with nasopharyngeal chronic inflammation (NPI). The correlations between the Axl protein levels and the clinical parameters of NPC patients were analyzed. NPC cells were cultured in vitro, and the expression of Axl in well differentiated CNE1 cells, poorly-differentiated CNE2Z cells and undifferentiated C666-1 cells was detected by immunofluorescence staining. After treatment of the CNE1and C666-1 cells with Axl specific inhibitor TP-0903, CCK-8 assay was used to detect cell viability, flow cytometry was adopted to analyze the cell cycle distribution, qPCR was used to examine the mRNA levels of Axl and proliferating cell nuclear antigen (PCNA), and Western blot was used to examine the protein expression of Axl and p-Axl. RESULTS: Axl protein was localized in the cell membrane and cytoplasm. The rate of high expression of Axl in NPC was significantly higher than that in NPI (P<0.01). High Axl expression showed no correlations with NPC patients' age, gender and M stage, while positively correlated with the clinical stage, T stage and N stage (P<0.05). Axl protein showed a low level in the CNE1 cells, but showed a high level in CNE2Z and C666-1 cells. TP-0903 inhibited cell viability in concentration and time dependent manners. TP-0903 at 2 nmol/L showed significant inhibitory effects, as evidenced by arresting the cell cycle at G₀ phase and reducing Axl activity and PCNA expression. CONCLUSION: High expression of Axl promotes the clinical progress of NPC.TP-0903 significantly inhibits the viability of NPC cells, suggesting that Axl may be a valuable target in the NPC treatment.     

Effects of extract of Oratosquilla on expression of P53, COX-2 and VEGF in human nasopharyngeal carcinoma cell line

AIM: To study the inhibitory effect of the extract of Oratosquilla(EOS) on the expression of P53, cyclooxygenase-2(COX-2) and vascular endothelial growth factor(VEGF) in nasopharyngeal carcinoma cell line CNE-2Z.METHODS: CNE-2Z cells were treated with different concentrations of EOS for 24 h. The methods of RT-PCR and immunocytochemistry were used to detect the expression of COX-2 and VEGF at mRNA and protein levels, respectively. The protein expression of P53 was determined by Western blotting.RESULTS: After treated with EOS, the protein expression of P53 in CNE-2Z cells was decreased(P<0.01), and the expression of COX-2 and VEGF at mRNA and protein levels was also significantly decreased in a dose-dependent manner(P<0.01). The expression of COX-2 was positively correlated with that of VEGF(P<0.05), and a positive correlation between the expression of COX-2 and P53 protein(P<0.05) was also observed.CONCLUSION: EOS may play its antitumor effect by inhibiting the expression of P53, COX-2 and VEGF in nasopharyngeal carcinoma cell line CNE-2Z.     

Difference of ClC-3 protein expression and channel function between cisplatin-sensitive and -resistant ovarian cancer cells

AIM: To study the difference of ClC-3 chloride channel protein expression and channel function between cisplatin-sensitive (a2780) and -resistant (a2780cp) ovarian cancer cells. METHODS: The inhibition of a2780 and a2780cp cell proliferation induced by cisplatin were detected by MTT assay. The mRNA and protein expressions of ClC chloride channel families in a2780 cells and a2780cp cells were detected by real-time PCR and Western blot, respectively. The distribution of ClC-3 protein in a2780 cells and a2780cp cells were analyzed by immunofluorescence staining. The whole cell patch-clamp technique was used to record the chloride current in the cells. RESULTS: The sensitivities of a2780 cells and a2780cp cells to cisplatin were different. The IC₅₀ values of a2780 cells and a2780cp cells to cisplatin were 5 μmol/L and 20 μmol/L, respectively (P<0.01). The a2780 cells and a2780cp cells mainly expressed ClC-3 in ClC families. However, the mRNA expression of ClC-3 was much lower in a2780cp cells than that in a2780 cells (P<0.01). Compared with a2780 cells, the protein expression of ClC-3 in a2780cp cells was also significantly decreased (P<0.01). ClC-3 protein was mainly distributed on the membrane in a2780 cells, while was in cytoplasma in a2780cp cells. Cisplatin activated the chloride channel and induced the chloride current in the a2780 cells, but not in the a2780cp cells. Cisplatin did not induced the chloride current in a2780 cells treated with ClC-3 siRNA. CONCLUSION: The differences in protein distribution, expression and function of ClC-3 chloride channel were observed in cisplatin-sensitive and -resistant ovarian cancer cells, which may be one of the underlying mechanisms of cisplatin resistance.