NHE1 is critical in normal mammary branching morphogenesis (Jenkins et al., 2012), helps to maintain an alkaline pHi in cancer cells (McLean et al., 2000), and is involved in the early events leading to the malignant transformation and G2/M entry of NIH3T3 mouse fibroblasts (Reshkin et al., 2000; Putney and Barber, 2003) as well as for human cancer cell polarization and invasion (Lagana et al., 2000; Reshkin et al., 2000; Paradiso et al., 2004). Here, SLC9A1 is linked to cancer.