Mechanistically, there is evidence to suggest that the sensitization effect following combined STAT3 inhibition and radiation in HNSCC is mediated by apoptosis [32,92,93,94,95,98], enhanced residual DNA-damage assessed by γH2AX staining [92] or comet assay [94], G2/M cell cycle arrest [98], and reduced tumor angiogenesis in murine xenografts of HNSCC cells [32]. Here, STAT3 is linked to head and neck squamous cell carcinoma.