One popular model is that Na+/H+ exchangers, particularly NHE1 (SLC9A1), are the main reason for the reversal of pHi and pHe in cancer tissues, along with monocarboxylate-H+ efflux cotransporters MCT1 (SLC16A1) and MCT4 (SLC16A3) and carbonic anhydrases for CO2 hydration [1]. Here, SLC9A1 is linked to cancer.