Defective ATM protein or aberrations of the MRE11A-RAD50-NBN complex, essential in DNA damage sensing and detection [80,81,82], silencing or deletion of other proteins involved in HR, such as ATR, RAD51, RAD54, DSS1, RPA1, NBN, CHK1, CHK2, FANCD2, FANCA, FANCC, FANCM or BARD1, may result in tumor sensitivity to PARPi monotherapy [80,83,84]. This evidence concerns the gene NBN and neoplasm.