CA9 and neoplasm: In a recently published paper exploring the role of the hypoxia-inducible gene carbonic anhydrase IX (CA9) in tumor resistance to bevacizumab, the authors discovered that tumors overexpressing CA9 exhibited increased cellular proliferation in culture and increased tumor growth in vivo. Similar to our study, the larger CA9-expressing tumors exhibited increased necrosis and increased apoptosis, with no elevation of Ki67 staining in the larger tumors [53].