The relevance of combining SMI of DNA DSB repair with IR was shown in several studies for example by Faulhaber and Jost et al. who inhibited DNA-dependent protein kinase catalytic subunit (DNA-PKcs)/mechanistic target of rapamycin kinase (mTOR), ataxia telangiectasia mutated (ATM), and ataxia telangiectasia and Rad3-related protein (ATR) and showed increased efficacy by a combined treatment with IR in cancer cell lines in vitro22. Here, ATR is linked to cancer.