Of particular note are the Na+/H+ exchanger, NHE1, and the Na+–bicarbonate cotransporter, NBCn1, both of which are upregulated and highly active in breast cancer (Amith et al., 2015; Boedtkjer et al., 2013; Cardone et al., 2005; McIntyre et al., 2016; Toft et al., 2021). This evidence concerns the gene SLC9A1 and breast cancer.