Mutations in DNA repair genes (e.g., BRCA1/2, PALB2, and RAD51C) and genome gatekeeper genes (e.g., TP53, ATM and CHEK2) are frequently found in cancer [212,213], and cancer cells with defective DDR or cell cycle checkpoints replicate damaged DNA to meet the uncontrolled proliferative drive induced by oncogenic signals. This evidence concerns the gene ATM and cancer.