CA9 and head and neck cancer: Notably, the expression levels of glucose transporter-1 (GLUT-1) and/or carbonic anhydrase IX (CAIX) were proved to correlate with the intensity of pimonidazole staining, a poor prognosis in patients with deep, large, high-grade soft tissue sarcomas [115], resistance of head and neck cancers to platinum-based radio-chemotherapy [116], and the frequency of local recurrence of glottic squamous cell carcinoma [117], etc.