CA9 and head and neck cancer: Again, clinical evidence from human tumors shows that stromal CA IX expression is strongly associated with the poor survival of head and neck cancer patients as well as in patients with colorectal cancer (Tomes et al., 2003; Cleven et al., 2007; Brockton et al., 2011, 2012; Kwon et al., 2013), and that in colorectal carcinoma, CA IX is co-expressed with the pro-inflammatory enzyme COX-2 (Sansone et al., 2009).