The role of gene-environment interaction in the aetiology of human cancer:examples from cancers of the large bowel, lung and breast

It has become increasingly clear that cancer can be considered neither pure ly genetic nor purely environmental. A relatively new area of cancer resear ch has focused on the interaction between genes and environment in the same causal mechanism. Primary candidates for gene-environment interaction stud ies have been genes that encode enzymes involved in the metabolism of estab lished cancer risk factors. There are common variant forms of these genes ( polymorphisms), which may alter metabolism and increase or decrease exposur e to carcinogens, thus impacting the risk of cancer. We present an overview of enzymes involved in carcinogen metabolism, present epidemiological tool s to evaluate gene-environment interactions, and provide examples from canc ers of the breast, lung and large bowel.