Furthermore, tumor cells exhibit complex pH regulation via sodium hydrogen exchanger-1 (NHE1), monocarboxylate transporters (MCT1-4), bicarbonate transporters, vacuolar ATPases (VATPase) and carboanhydrases (CAII, CAIX, CAXII) [1,4,5,6]. The gene discussed is SLC9A1; the disease is neoplasm.