For this purpose, two HNSCC cell lines were examined in this regard after exposure to IR or CDDP and pharmacological inhibition of DNA damage response kinases ataxia telangiectasia and Rad3-related (ATR) and checkpoint kinase 1 (Chk1) or gene knockout of FA complementation group A (FANCA ko). Here, ATR is linked to head and neck squamous cell carcinoma.