Disulfiram-copper activates chloride currents and induces apoptosis with tyrosine kinase in prostate cancer cells.

AIM: To elucidates the mechanism that disulfiram/copper complex (DSF/Cu) treatment activates chloride channels and induces apoptosis in prostate cancer cells. METHODS: Cellular membrane currents were measured by membrane clamp technique; western blot to detect protein expression; flow cytometry to detect apoptosis; immunofluorescence to detect target protein co-localization, and further validated by a combination of protein-protein interaction and mock protein molecular docking techniques. RESULTS: DSF/Cu activated chloride channels and induced apoptosis in LNCaP (a type of androgen-dependent prostate cancer cells) cells. The chloride currents activated by DSF/Cu were significantly reduced after knockdown of CLC3 with siRNA. In addition, DSF/Cu-activated chloride currents were reduced to background current levels after perfusion with genistein, a highly specific tyrosine kinase inhibitor. Conversely, DSF/Cu failed to activate chloride currents in LNCaP cells after 30 minutes of pre-incubation with genistein. When genistein was removed, and DSF/Cu was added, the activated currents were small and unstable, and gradually decreased. Immunofluorescence in LNCaP cells also showed co-localization of the CLC3 protein with tyrosine kinase 2ß (PTK2B). CONCLUSION: DSF/Cu can activate chloride channels and induce apoptosis in LNCaP cells with the involvement of tyrosine kinase. These results provide new insights into the target therapy of prostate cancer.

Antitumor effects of disulfiram/copper complex in the poorly-differentiated nasopharyngeal carcinoma cells via activating ClC-3 chloride channel.

The enhancement of the anticancer activity by disulfiram (DSF) chelated with copper (DSF/Cu2+) has been investigated recently, while the underlying molecular mechanisms still need to be fully elucidated. Chloride channel-3 (ClC-3) is over-expressed in a variety of cancers and involves multiple tumor biological events. However, whether the over-expression of ClC-3 in tumor cells affects the sensitivity of anti-tumor drugs remains unclear. Here, we showed that the involvement of ClC-3 chloride channel in the selective cytotoxicity of DSF/Cu2+ in the poorly-differentiated nasopharyngeal carcinoma. The EC50 of DSF alone and DSF/Cu2+ in activating the Cl- channel were 95.36 µM and 0.31 µM in the CNE-2Z cells, respectively. DSF/Cu2+ exhibited a positive correlation between the induction of the Cl- currents and the inhibition of cell proliferation. DSF/Cu2+ increased the ClC-3 protein expression and induced the cell apoptosis. Cl- channel blockers, NPPB and DIDS, and ClC-3 siRNA partially inhibited the cell apoptosis, and depleted the Cl- currents induced by DSF/Cu2+ in CNE-2Z cells. However, these effects could not be observed in the normal nasopharyngeal epithelium NP69-SV40 T cells. In vivo, the transplanted human nasopharyngeal carcinoma tumors size in the DSF/Cu2+ group decreased about 73.2% of those in the solvent control group. The chloride blockers partially inhibited the antitumor action of DSF/Cu2+. These data demonstrated that the selective cytotoxicity of DSF/Cu2+ may relate to its selective activation of ClC-3 Cl- channel pathways in CNE-2Z cells. ClC-3 Cl- channel can be viewed as a new and promising target for the treatment of nasopharyngeal carcinoma.

Opening of the CLC-3 chloride channel induced by dihydroartemisinin contributed to early apoptotic events in human poorly differentiated nasopharyngeal carcinoma cells.

Nasopharyngeal carcinoma (NPC) is a specific type of head and neck cancer that is prevalent in Southeast Asia. Dihydroartemisinin (DHA), a semisynthetic derivative of artemisinin, has specific anticancer activity. Here, we aimed to investigate the role of the CLC-3 chloride channel in the anticancer effect of DHA in poorly differentiated NPC CNE-2Z cells. First, we observed that DHA could specifically inhibit the proliferation, induce apoptosis, and increase cleaved caspase-3 expression in the CNE-2Z cells. Then, we found that DHA could activate chloride channels, which led to Cl- efflux and apoptotic volume decrease (AVD) in the early stage in the CNE-2Z cells. DHA also specifically increased CLC-3 chloride channel protein expression in the CNE-2Z cells. Silencing of the CLC-3 protein expression depleted the Cl- currents, and decreased the AVD capacity and cell apoptosis induced by DHA. Finally, we revealed that the [Ca2+ ]i increased after around 6 hours of treatment with DHA, which was also inhibited by silencing of the CLC-3 protein expression. Our data demonstrated that the selective antitumor activities of DHA in NPC may occur through the specific activation of the CLC-3 Cl- channel, leading to Cl- efflux, and induced AVD, then led to [Ca2+ ]i accumulation and caspase-3 activation, and finally induced apoptosis. The activation of the CLC-3 chloride channel played an essential and proximal upstream role in the antitumor activities of DHA.