CA9 and cancer: These attributes, together with its ease of accessibility to pharmacologic agents due to its membrane-bound, extracellular catalytic domain, have made CAIX a very attractive target for cancer therapy (Neri and Supuran, 2011; Wilson and Hay, 2011; McDonald et al., 2012; Supuran, 2012; Pastorek and Pastorekova, 2015).