CHEK2 and breast cancer: In addition to the two major breast cancer susceptibility genes, BRCA1 and BRCA2, several other genes associated with breast cancer predisposition have been identified, including ATM, CHEK2, PALB2, RAD51C and BRIP1. Many of these genes are associated with BRCA1 and BRCA2 in the DNA damage response (DDR) pathway (4).