HIF1A and head and neck squamous cell carcinoma: Among general resistance mechanisms, chronic/intermittent hypoxia and hypoxia-inducible factors are known to adversely impact tumor response to radiation and chemotherapy in many types of cancer [16,17,18,19], and especially in HNSCC [10,20] where hypoxia and HIF-1 have been shown to induce the upregulation of EGFR [8].