It has been demonstrated that endothelial interleukin 6 (IL-6) enhances the self-renewal of CSCs through the activation of Bmi-1 and downstream signal transducer and activator of transcription 3 (STAT3) signaling in human HNSCC, while humanized anti-IL-6R antibody (tocilizumab) significantly inhibits CSC-mediated tumorigenic ability [25, 26]. Here, STAT3 is linked to head and neck squamous cell carcinoma.