K+ channel expression in human breast cancer cells: Involvement in cell cycle regulation and carcinogenesis

K+ channels are a most diverse class of ion channels in the plasma membrane and are distributed widely throughout a variety of cells including cancer cells. Evidence has been accumulating from fundamental studies indicating that tumour cells possess various types of K+ channels and that these K+ channels play important roles in regulating tumor cell proliferation, cell cycle progression and apoptosis. Moreover, a significant increase in K+ channel expression has been correlated with tumorigenesis, suggesting the possibility of using these proteins as transformation markers and perhaps reducing the tumor growth rate by selectively inhibiting their functional activity. Significant progress has been made in defining the properties of breast K+ channels, including their biophysical and pharmacological properties and distribution throughout different phases of the cell cycle in breast cell line MCF-7. This review aims to provide a comprehensive overview of the current state of research into K+ channels/currents in breast cancer cells. The possible mechanisms by which K+ channels affect tumor cell proliferation and cell cycle progression are discussed.