One CA, CAVI, is secreted, two (CAVA and VB) are found in the mitochondria, five are cytosolic (CAs I, II, III, VII, and XIII), and five are found on membranes (CA IV, IX, XII, XIV, and XV); of these, CAIX and CAXII have been shown to play an important role in cancer progression [32,33]. This evidence concerns the gene CA9 and cancer.