GSTP1 and colorectal carcinoma: Our previous studies have shown that the null genotypes of GSTM1 and GSTT1, GSTP1 Ile105Val, XRCC1 Arg399Gln, XRCC3 Thr241Met, and XPD Lys751Gln allelic variants are associated with significantly increased risks of CRC [29]–[32].