Inter-individual variation in susceptibility to colorectal neoplasia: the interaction between diet, DNA damage markers and genetic polymorphisms.

ABSTRACT: Study hypothesis: CRC risk is affected by diet and by genetic polymorphisms leading to inter-individual variation in the metabolism of environmental carcinogens. Our first hypothesis is that these effects may combine to place certain individuals at greatly enhanced risk according to their diet. We shall examine how dietary factors known to affect CRC risk (including meats, fat, fruit and vegetables, cooking methods, dietary supplements and drugs) and genetic polymorphisms implicated in CRC (Glutathione S-transferase: GSTM1, GSTM3, GSTT1; N-acetyl transferase: NAT1, NAT2; and Cytochrome P450: CYP1A1, CYP2D6) combine to affect the prevalence of colorectal polyps, both adenomatous (the precursor lesion of CRC) and metaplastic. Our second hypothesis is that diets associated with increased risk (high red meat, low vegetable and low fibre consumption) may affect DNA damage markers which may be elevated in people with colorectal adenomas. We shall therefore examine the effect of diet on adduct rates (cross sectional) and adduct rates in people with and without colorectal adenomas. We shall examine malondialdehyde adduct rates in relation to anti-oxidant status and carboxymethyl adduct rates and k-ras mutation frequency in relation to meat consumption; and examine the effect of DNA repair enzyme (ATase) activity on any relationship found. In summary the aim of this population based study is to link dietary factors thought to be important in the genesis of colorectal polyps and cancer with genetic polymorphisms and DNA damage markers in rectal mucosa and in blood. Primary outcome(s): We shall perform cross-sectional and case-control analyses of the effect of diet and genetic polymorphisms on the prevalence of adenomatous and metaplastic polyps. Genetic polymorphisms will be examined in isolation and paired combinations and in groups stratified according to diet. We shall examine the effect of diet on MDA adduct rates (concentrating on foods relating to anti-oxidant status) and CBM adduct rates and k-ras mutations (concentrating on meat consumption and cooking methods) by categorical variables; and MDA and CBM adducts and k-ras mutation frequency in people with adenomatous polyps and polyp free controls (case-control). We shall examine the affect of ATase activity on any relationship found and ATase activity in people with adenomatous polyps and polyp free controls (case control). DNA will be stored for future analysis of as yet unrecognised polymorphisms which may be recognised as having a role in CRC. Samples taken from EPIC participants for adduct, ATase and k-ras measurement whose polyps are found to be metaplastic will be stored for possible future analysis: we shall investigate people with adenomatous polyps in the first instance as these are the precursors of colorectal cancer.

DISEASE(S): Colorectal Cancer

PROVIDER: 2417295 | ecrin-mdr-crc |

REPOSITORIES: ECRIN MDR