Also, eight of the nine studied SHBG-related GWAS-impacted SNPs have been involved in BC susceptibility as part of nine gene interaction models, the greatest contribution to which was made by rs10454142 PPP1R21 (included in all nine models, 100%) and some other loci (rs7910927 JMJD1C, rs17496332 PRMT6, rs780093 GCKR, and rs440837 ZBTB10). This evidence concerns the gene PPP1R21 and breast cancer.