ATM and cancer: In fact, besides BRCA1/2 mutations, a variety of additional genetic alterations may contribute to induce in cancer cells a “BRCAness phenotype”, characterized either by a defective DNA Damage Response (DDR) [52] or by reduced expression of other factors involved in DNA repair (e.g., PI3-kinase-related protein kinases Ataxia-Telangiectasia Mutated (ATM), RAD3-related (ATR), Checkpoint Kinase 1 and 2 (CHK1/2), DSS1, RAD51, CDK12, TP53, or Phosphatase and Tensin Homolog (PTEN)) [52,53,54,55].