title: The relationship between gene-specific DNA methylation in leukocytes and normal colorectal mucosa in subjects with and without colorectal tumors.
abstract: CpG island methylation in the promoter regions of tumor suppressor genes has been shown to occur in normal colonic tissue and can distinguish between subjects with and without colorectal neoplasms. It is unclear whether this relationship exists in other tissues such as blood. We report the relationship between estrogen receptor gene (estrogen receptor alpha) methylation in leukocyte and normal colonic tissue DNA in subjects with and without colorectal neoplasia. DNA was extracted from frozen stored whole blood samples of 27 subjects with cancer, 30 with adenoma, 16 with hyperplastic polyps, and 57 disease-free subjects. DNA methylation in seven CpG sites close to the transcription start of estrogen receptor alpha was quantitated using pyrosequencing and expressed as a methylation index (average methylation across all CpG sites analyzed). Estrogen receptor alpha methylation in leukocyte DNA was compared with estrogen receptor alpha methylation in normal colonic mucosa DNA that had been previously determined in the same subjects. Estrogen receptor alpha was partially methylated (median, 4.3%; range, 0.0-12.6%) in leukocyte DNA in all subjects, with no significant difference between disease groups (P>0.05). Estrogen receptor alpha methylation in leukocytes was 60% lower than estrogen receptor alpha methylation in normal colonic tissue (P<0.001). Estrogen receptor alpha methylation in colonic tissue (P<0.001) and smoking (P=0.016) were determinants of estrogen receptor alpha methylation in leukocytes, independent of age, body mass index, gender, and disease status. In conclusion, there was a positive relationship between estrogen receptor alpha methylation in leukocytes and colonic tissue in subjects with and without colorectal tumors. However, unlike in colonic tissue, estrogen receptor alpha methylation in leukocytes was unable to distinguish between disease groups.
authors.affiliation: Diet and Gastrointestinal Health Group, Department of Nutrition and Dietetics, King's College London, Franklin Wilkins Building, 150 Stamford Street, London SE1 9NH, United Kingdom.
authors.forename: Mina Sarah
authors.initials: MS
authors.lastname: Ally
authors.forename: Reyad
authors.initials: R
authors.lastname: Al-Ghnaniem
authors.forename: Maria
authors.initials: M
authors.lastname: Pufulete
mesh_terms: D000236:Adenoma / Q000235:genetics / Q000378:metabolism; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003111:Colonic Polyps / Q000235:genetics* / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005260:Female; D005492:Folic Acid / Q000097:blood; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D018709:Statistics, Nonparametric
chemical_list: D015415:Biomarkers; D047628:Estrogen Receptor alpha; D005492:Folic Acid