[Alterations in ATP-dependence of swelling-activated Cl- current associated with neuroendocrine differentiation of LNCaP human prostate cancer epithelial cells].

Increasing population of malignant, apoptosis resistant neuroendocrine (NE) cells due to differentiation of prostate epithelial/basal cells is a hallmark of advanced, androgen-independent prostate cancer, for which there is no successful therapy. Acquisition of apoptosis resistance involves alterations in the mechanisms of cell volume homeostasis, of which volume-regulate anion channels (VRAC) that carry swelling-activated Cl- current (I(Cl,swell)) represent one of the key determinants. Given that VRAC function is generally known to be ATP-dependent, here we investigated how such dependence may evolve during NE differentiation of LNCaP prostate cancer epithelial cells. In the whole-cell patch-clamp recording mode I(Cl,swell) could be activated in response to hypotonicity-induced cell swelling in control and NE-differentiated (by incubation in membrane-permeable cAMP analogs) LNCaP cells even following total depletion of intracellular ATP using a cocktail of metabolic inhibitors. However, this basal I(Cl,swell) had about 30% higher density and was less inactivating in NE-differentiated cells. Inclusion of 5 mM Mg-ATP in the patch pipette caused I(Cl,swell) augmentation in both cell types. The augmentation in the control cells was more prominent and occurred mostly at the expense of a non-inactivating current component. We conclude that I(Cl,swell) in LNCaP cells consists of a non-inactivating, ATP-dependent and inactivating, ATP-independent components. NE differentiation promotes the increase of non-inactivating component and partial loss of its ATP sensitivity making the whole I(Cl,swell) less ATP-sensitive as well. By largely avoiding the ATP metabolic control I(Cl,swell) may contribute to better control of cell volume under metabolic stress and thus enhance the survival rates of apoptosis-resistant NE cells.