GSTP1 and cancer: GSTP1 and GSTM1 do have multiple SNPs (for example, GSTP1 rs1695, A105G results in an amino acid substitution in codon 105 from valine to isoleucine associated with increased cancer risk), however, the null alleles described and focused on in this review result from gene deletion between the H3 and H5 regions flanking the gene [35].