ATR and cancer: Radiotherapy, a major inducer of cellular stress, has been reported to drive an increase in the expression of stress-inducible NK cell–activating ligands, such as ULBP1-3, MICA/B, and B7-H3, on the surface of cancer cells primarily through activation of the ataxia-telangiectasia mutated (ATM)/ATM- and Rad3-Related (ATR) DNA damage response pathway (14, , , –18).