PPP1R21 and breast cancer: We have studied the supposed functional effects of BC-involved polymorphisms in 2 directions: (1) the functional significance of rs10454142 PPP1R21 (and 10 SNPs strongly linked to it), which demonstrated the main risk effect for BC, was considered; (2) the functional potential of all 8 SHBG-related polymorphisms associated with BC risk was evaluated; (3) summary functionality of all 130 BC-correlated loci (8 BC-causal and 122 proxy SNPs) was examined.