DNA methylation in pre-diagnostic serum samples of breast cancer cases: results of a nested case-control study.
BACKGROUND
Promoter methylation of tumor suppressor genes is a frequent and early event in breast carcinogenesis. Paired tumor tissue and serum samples from women with breast cancer show that promoter methylation is detectable in both sample types, with good concordance. This suggests the potential for these serum markers to be used for breast cancer detection.


METHODS
The current study was a case-control study nested within the prospective New York University Women's Health Study cohort aimed to assess the ability of promoter methylation in serum to detect pre-clinical disease. Cases were women with blood samples collected within the 6 months preceding breast cancer diagnosis (n=50). Each case was matched to 2 healthy cancer-free controls and 1 cancer-free control with a history of benign breast disease (BBD).


RESULTS
Promoter methylation analysis of four cancer-related genes: -RASSF1A, GSTP1, APC and RARβ2, - was conducted using quantitative methylation-specific PCR. Results showed that the frequency of methylation was lower than expected among cases and higher than expected among controls. Methylation was detected in the promoter region of: RASSF1A in 22.0%, 22.9% and 17.2% of cases, BBD controls and healthy controls respectively; GSTP1 in 4%, 10.4% and 7.1% respectively; APC in 2.0%, 4.4% and 4.2% respectively and RARβ2 in 6.7%, 2.3% and 1.1% respectively.


CONCLUSIONS
Methylation status of the four genes included in this study was unable to distinguish between cases and either control group. This study highlights some methodological issues to be addressed in planning prospective studies to evaluate methylation markers as diagnostic biomarkers.
Brooks
Jennifer D
JD
Division of Epidemiology, Department of Environmental Medicine, New York University School of Medicine, New York, NY 10016, United States. brooksj@mskcc.org
Cairns
Paul
P
Shore
Roy E
RE
Klein
Catherine B
CB
Wirgin
Isaac
I
Afanasyeva
Yelena
Y
Zeleniuch-Jacquotte
Anne
A
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood*; D001943:Breast Neoplasms / Q000097:blood / Q000175:diagnosis / Q000235:genetics*; D016022:Case-Control Studies; D015331:Cohort Studies; D019175:DNA Methylation; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011446:Prospective Studies
D014408:Biomarkers, Tumor