Plasma membrane (PM) and mitochondrial (mt) ion channels - particularly potassium channels - became oncological targets
soon after the discovery that they are involved both in the regulation of proliferation and apoptosis. Some members of the Kv Shaker
family, namely Kv1.1, Kv1.3, Kv1.5 and Kv11.1 (Herg), and the intermediate-conductance calcium-activated potassium KCa3.1 (IK)
channels have been shown to contribute to apoptosis in various cell lines. Kv1.3, Kv1.5 and IK are located in the plasma membrane but
also in the mitochondrial inner membrane, where they participate in apoptotic signalling. Interestingly, an altered protein expression of
some of the channels mentioned above has been reported in neoplastic cell lines/tissues, but a systematic quantification addressing the
protein expression of the above potassium channels in tumor cell lines of different origin has not been carried out yet. In the present study
we investigated whether expression of specific potassium channels, at the mRNA and protein level, can be correlated with cell sensitivity
to various apoptotic stimuli, including chemotherapeutic drugs, in a panel of cancer cell lines. The results show correlation between the
protein expression of the Kv1.1 and Kv1.3 channels and susceptibility to death upon treatment with staurosporine, C2-ceramide and cisplatin.
Furthermore, we investigated the correlation between Kv channel expression and sensitivity to three distinct membrane-permeant
Kv1.3 inhibitors, since these drugs have recently been shown to be able to induce apoptosis and also reduce tumor volume in an in vivo
model. Higher protein expression of Kv1.3 significantly correlated with lower cell survival upon treatment with clofazimine, one of the
Kv1.3 inhibitors. These results suggest that expression of Kv1.1 and Kv1.3 sensitizes tumour cells of various origins to cytotoxins. Data
reported in this work regarding potassium channel protein expression in different cancer cell lines may be exploited for pharmacological
manipulation aiming to affect proliferation/apoptosis of cancer cells.