Strikingly, the endothelium of the ccRCC vasculature showed very high KCa3.1-protein expression, which is in line with the constitutive expression of KCa3.1 in the endothelium of blood vessels and, in addition, with up-regulation of KCa3.1-mRNA expression and functional KCa3.1-proteins (currents) in human endothelial cells after mitogenic stimulation as shown previously by us [20]. Here, KCNN4 is linked to nonpapillary renal cell carcinoma.