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


METHODS
A quantitative methylation-specific PCR assay was used to analyze the DNA methylation status of 6 genes (DAPK, TWIST, HIN-1, RASSF1A, RARbeta2 and APC) in 9 normal breast tissue samples from unaffected women and in 56 paired cancerous and normal tissue samples from breast cancer patients.


RESULTS
Normal tissue adjacent to breast cancer displayed statistically significant differences to unrelated normal breast tissues regarding the aberrant methylation of the RASSF1A (P = 0.03), RARbeta2 (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 < or = 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.


CONCLUSIONS
Histologically 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.
Translational Cancer Research Group (Laboratory of Pathology, University of Antwerp/University Hospital Antwerp; Oncology Centre, General Hospital St-Augustinus), 2610 Antwerp, Belgium.
Ilse
I
Van der Auwera
Catherine
C
Bovie
Cecilia
C
Svensson
Xuan B
XB
Trinh
Ridha
R
Limame
Peter
P
van Dam
Steven J
SJ
van Laere
Eric A
EA
van Marck
Luc Y
LY
Dirix
Peter B
PB
Vermeulen
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000502:physiology / Q000601:surgery; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D016022:Case-Control Studies; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004273:DNA, Neoplasm