Due to a synergistic relationship among GSTM1 (OMIM: 138350), GSTT1 (OMIM: 600436), and GSTP1, the presence of GSTM1 or GSTT1 nulls with GSTP1 Ile/Val or Val/Val genotypes significantly increased the BC susceptibility in this population. This evidence concerns the gene GSTP1 and breast cancer.