Although allele frequencies of 5q11.2/MAP3K1 rs889312 (like 16q12.1/TOX3 rs3803662) were substantially different between Europeans and Koreans, the rs889312 C allele was also significantly associated with increased risk of breast cancer (OR = 1.16; 95% CI = 1.06 to 1.27; Ptrend = 8.49 × 10-4). Here, MAP3K1 is linked to breast cancer.