APC and breast cancer: In addition, other genes involved in DNA damage repair (DDR) pathways different from HR and cell cycle control, such as APC, CDH1, CDK4, CDKN2A, PTEN, SMAD4, TP53 [13,14,15,16,17,18], and the DNA helicase RECQL [19], have been associated with high or moderate susceptibility to familial breast cancer (BC) and other types of malignancies.