Background: Red and processed meat are associated with high risks of colorectal cancer due to the endogenous formation of O<sup>6</sup>-carboxymethyl guanine (O<sup>6</sup>CMG), a potent carcinogen. The aim of our research is to develop liquid chromatography tandem mass spectrometry (LC-MS/MS) analytical methods for the measurement of the DNA adducts, such as O<sup>6</sup>CMG and its nucleoside O<sup>6</sup>-carboxymethyl deoxyguanosine (O<sup>6</sup>CMdG), in urine samples and correlate it to different diets.
Methods: Urine samples were collected from volunteers on three different diets (vegetarian as the control, with red and processed meat as the experimental group) over a period of 15 days at the Medical Research Council, Cambridge. Samples were analysed by LC-MS/MS either by direct injection or using a column-switching system with an on-line solid phase extraction (SPE) column.
Results: An LC-MS/MS method was developed and used initially to monitor and quantify O<sup>6</sup>CMdG and O<sup>6</sup>CMG using standards in synthetic urine. O<sup>6</sup>CMG elutes at 4.7 min and have a limit of detection (LOD) of 0.3ng/mL, and O<sup>6</sup>CMdG elutes at 14.1 min and have a LOD of 0.03ng/mL. The LC-MS/MS direct injection analysis of the clinical samples showed low sensitivity and the need for sample clean-up.
Conclusions: An efficient method for the separation and quantification of O<sup>6</sup>CMdG and O<sup>6</sup>CMG was developed. An on-line SPE column system is under development to allow an efficient and rapid processing of a large number of clinical urine samples.
Da Pieve, Chiara ; Moore, Sharon and Velasco, Maria (2010). Screening for colorectal cancer risk biomarkers related to diet. In: Nutrition, Physical Activity & Cancer Prevention: Current Challenges, New Horizons, 12-13 Sep 2010, Royal College of Physicians, London, UK.