Targeting HIF-1α/NOTCH1 pathway eliminates CD44+ cancer stem-like cell phenotypes, malignancy, and resistance to therapy in head and neck squamous cell carcinoma

Poor prognosis of head and neck squamous cell carcinomas (HNSCCs) results from resistance to chemotherapy and radiotherapy. To uncover the drivers of HNSCC resistance, including stemness and hypoxia, in this study, we compared the gene expression between CD44(+) and CD44(-) HNSCC cells and assessed the correlation of CD44 and hypoxia-inducible factor 1 alpha (HIF-1 alpha) expression with mouse features and outcomes of patients with HNSCC. We combined the knockdown or activation of HIF-1 alpha with in vitro and in vivo assays to evaluate effects on stemness and resistance of HNSCC cells. Analysis of clinical data showed that activation of HIF-1 alpha in CD44(+) patients with HNSCC was correlated with worse prognosis. Functional assays showed that HIF-1 alpha promoted stemness, resistance, and epithelial-mesenchymal transition in HNSCC CD44(+) cells. HIF-1 alpha activated NOTCH1 signaling in HNSCC stem-like cells characterized by CD44 expression. Moreover, inhibition of these signaling proteins using shRNA or Evofosfamide (Evo) development for cancer treatment, reversed chemoresistance in vitro and in vivo. Taken together, our results indicated that targeting HIF-1 alpha attenuated NOTCH1-induced stemness, which regulates responses to chemotherapy or radiotherapy and malignancy in CD44(+) HNSCCs. HIF-1 alpha/NOTCH1 signaling may represent a target for HNSCC treatment.