CA9 and cancer: The importance of the carbonic buffer system in cancer is also underscored by the ability of the hypoxia inducible carbonic anhydrase IX (CAIX), which is upregulated in a wide variety of cancers (Bartosova et al., 2002; Chen et al., 2005; Supuran, 2008; Perez-Sayans et al., 2012), to increase HCO−3-dependent resting pHi and decrease pHe in Chinese hamster lung CCL39 fibroblasts.