**2.6. Calcium-activated potassium channels in breast cancer**

Prolactin increases the current density of the human Ca2+-activated K<sup>+</sup> channels (hIKCa1) in MCF-7 breast cancer cells, involved in the cell proliferation in a dose-dependent manner and activating the Janus kinase (JAK2)-coupled cytokine receptor pathway [98].

Large conductance Ca2+-activated K<sup>+</sup> channels (BKCa) were described to be expressed in several breast cancer cell lines (e.g., UACC893, SK-BR-3, and MDA-MB-231) [99]. Intermediateconductance, Ca2+-activated K<sup>+</sup> channels (hIK1) are also functionally expressed in MCF7 breast cancer cells, and their current density and basal cytosolic Ca2+ concentration being augmented in cells synchronized at the end of the G1 or S phase with respect to the cells in the early G1 phase [100]. Caveolin-1 was demonstrated to colocalize with BKCa in MCF-7 breast cancer cells, and silencing caveolin-1 induces increased activation and upregulation of BKCa [101].
