Epidemiological studies revealed that the association of breast cancer with many susceptibility loci (e.g., FGFR2, TNRC9, ADAM29, 8q24, 2q35, and 5p12) were significantly modified by estrogen receptor status[19–23]; among them a variant in FGRF2, 5p12, and a SNP on 4q34.1/ADAM29 (in Chinese women) was evident to be linked to the ER+ tumor[20–22]. This evidence concerns the gene TOX3 and breast cancer.