CHEK2 and breast cancer: Furthermore, mutations in moderate-penetrance genes such as BRCA1 interacting protein C-terminal helicase 1 (BRIP1), ataxia telangiectasia mutated (ATM), partner and localizer of BRCA2 (PALB2), and checkpoint kinase 2 (CHEK2) are associated with a two-fold increased risk of developing breast cancer [32].