CA9 and cancer: Its expression correlates with HIF-1 alpha, and CA-9 the biomarkers of tumor hypoxia in HNC [76] and other cancers like pancreatic cancer, [77] anaplastic thyroid cancer [78] miR210, in head neck paragangliomas associated with VHL gene mutation has been found to be activated along with HIF-1 [79]; however, it has been found to be independent of SDH mutation [80].