Eag1 and Bestrophin 1 are up-regulated in fast-growing colonic cancer cells.

Ion channels like voltage-gated ether-á-go-go (Eag1) K(+) channels or Ca(2+)-activated Cl(-) channels have been shown to support cell proliferation. Bestrophin 1 (Best1) has been proposed to form Ca(2+)-activated Cl(-) channels in epithelial cells. Here we show that original T(84) colonic carcinoma cells grow slowly (T(84)-slow) and express low amounts of Eag1 and Best1, whereas spontaneously transformed T(84) cells grow fast (T(84)-fast) and express high levels of both proteins. Both Eag1 and Best1 currents are up-regulated in T(84)-fast cells. Eag1 currents were cell cycle-dependent with up-regulation during G(1)/S transition. T(84)-slow, but not T(84)-fast, cells formed tight monolayers when grown on permeable supports. RNA interference inhibition of Eag1 and Best1 reduced proliferation of T(84)-fast cells, whereas overexpression of Best1 turned T(84)-slow into fast-growing cells. Eag1 and Best1 improve intracellular Ca(2+) signaling and cell volume regulation. These results establish a novel role for bestrophins in cell proliferation.