The aim of this review is to give a summary of currently available data on the relation between the CYP, the GST and the UGT biotransformation system and colorectal cancer obtained from clinical and epidemiological studies in humans.
Heritable genetic variants in the ABC and SLC transport pathways; in the CYP450, GST, and UGT-mediated phase I and II metabolism; in the folate metabolic pathway; as well as in the EGF and VEGF signaling pathways, have been associated with a distinct tumor sensitivity phenotype in CRC patients treated with fluoropyrimidines combined with either irinotecan, oxaliplatin or targeted biological agents.
This suggests that UGT genetic variation alters CRC risk differently by anatomical sub-site and gender and that polymorphisms in the UGT1A shared exons may have a regulatory effect on gene expression that allows for the protective effect of NSAIDs on CRC risk.
Metabolizers of environmental carcinogenic and endogenous compounds affecting CRC risk include the phase II detoxification UDP-glucuronosyltransferase (UGT) enzymes UGT2B17 and UGT2B28, which are 2 of the most commonly deleted genes in the genome.
Irinotecan toxicity in colorectal cancer is more common in patients with reduced-activity UGT1A alleles, resulting in excessive exposure to the potent SN-38 metabolite.