We therefore hypothesized that inhibition of central proteins of the DDR such as ataxia-telangiectasia mutated protein (ATM) and ataxia telangiectasia and Rad3-related protein (ATR) in HPV-negative and HPV-positive head and neck cancer tumor cells in combination with RT differently affects the immune phenotype of HNSCC cells and consecutively also that of natural killer (NK) cells. The gene discussed is ATR; the disease is head and neck squamous cell carcinoma.