As DNA sequencing technologies evolved, other cancer susceptibility genes have been discovered, including high-penetrant genes such as TP53, CDH1, STK11, PTEN and PALB2 (>  4 fold cancer relative risk), moderate-penetrant genes such as CHEK2 and ATM (1.5–4 fold cancer relative risk), and a number of common low-penetrant BC susceptibility loci identified through genome-wide association studies (1–1.5 fold cancer relative risk)5–7. Here, CHEK2 is linked to breast cancer.