XK and breast cancer: Still, our previous studies confirm that the Na+,HCO3– cotransport in human breast cancer tissue is of low 4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid sensitivity (Boedtkjer et al., 2013), which is a pharmacological characteristic of NBCn1 relative to other Na+,HCO3– cotransporters (Boedtkjer et al., 2012; Choi et al., 2000; Romero et al., 2004).