Quantitative methylation profiling in tumor and matched morphologically normal tissues from breast cancer patients

Abstract

BackgroundIn the present study, we determined the gene hypermethylation profiles of normal tissues adjacent to invasive breast carcinomas and investigated whether these are associated with the gene hypermethylation profiles of the corresponding primary breast tumors.MethodsA quantitative methylation-specific PCR assay was used to analyze the DNA methylation status of 6 genes (DAPK, TWIST, HIN-1, RASSF1A, RARβ2 and APC) in 9 normal breast tissue samples from unaffected women and in 56 paired cancerous and normal tissue samples from breast cancer patients.ResultsNormal tissue adjacent to breast cancer displayed statistically significant differences to unrelated normal breast tissues regarding the aberrant methylation of the RASSF1A (P = 0.03), RARβ2 (P = 0.04) and APC (P = 0.04) genes. Although methylation ratios for all genes in normal tissues from cancer patients were significantly lower than in the cancerous tissue from the same patient (P ≤ 0.01), in general, a clear correlation was observed between methylation ratios measured in both tissue types for all genes tested (P < 0.01). When analyzed as a categorical variable, there was a significant concordance between methylation changes in normal tissues and in the corresponding tumor for all genes tested but RASSF1A. Notably, in 73% of patients, at least one gene with an identical methylation change in cancerous and normal breast tissues was observed.ConclusionsHistologically normal breast tissues adjacent to breast tumors frequently exhibit methylation changes in multiple genes. These methylation changes may play a role in the earliest stages of the development of breast neoplasia.

High RASSF1A promoter methylation levels are predictive of poor prognosis in fine-needle aspirate washings of breast cancer lesions

“…Although associations between gene promoter methylation and age have been reported, they are not a universal finding and results are even conflicting concerning breast tissues. Whereas some researchers found age related variations for RASSF1A, with an odd pattern of increase from 32 to 55 years with a decline thereafter [22], other studies did not find such a correlation [23]. Moreover, no correlation between age and APC or CCND2 promoter methylation has been reported thus far [22,24].…”

Quantitative assessment of the association between APC promoter methylation and breast cancer

“…Among 29 studies, there were 26 case-control studies [12, 14, 15–33, 35, 37–40] and 3 cohort studies [35, 36, 41]. Interestingly, 12 studies [12, 14, 15, 18, 19, 22, 24, 26–28, 32, 38] among 26 case-control studies also did the cohort analyses.…”

Primary tumor classification according to methylation pattern is prognostic in patients with early stage ER-negative breast cancer

“…To define the occurrence of aberrant genomic methylation in primary breast tumors, three biomarkers (RARß2, MINT17, and MINT31) were selected. These three biomarkers were chosen because they are CpG-rich genomic regions that frequently display aberrant hypermethylation during malignant transformation in solid tumors [12][13][14][15]. RARß2 is a tumor suppressor gene of which loss of expression because of hypermethylation is a significant event in breast cancer development [11,[16][17][18].…”