BACKGROUND: Invasion and metastasis are two important hallmarks of malignant 
tumors caused by complex genetic and epigenetic alterations. The present study 
investigated the contribution of aberrant methylation profiles of cancer related 
genes, APC, BIN1, BMP6, BRCA1, CST6, ESR-b, GSTP1, P14 (ARF), P16 (CDKN2A), P21 
(CDKN1A), PTEN, and TIMP3, in the matched axillary lymph node metastasis in 
comparison to the primary tumor tissue and the adjacent normal tissue from the 
same breast cancer patients to identify the potential of candidate genes 
methylation as metastatic markers.
METHODS: The quantitative methylation analysis was performed using the 
SEQUENOM's EpiTYPER™ assay which relies on matrix-assisted laser 
desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).
RESULTS: The quantitative DNA methylation analysis of the candidate genes showed 
higher methylation proportion in the primary tumor tissue than that of the 
matched normal tissue and the differences were significant for the APC, BIN1, 
BMP6, BRCA1, CST6, ESR-b, P16, PTEN and TIMP3 promoter regions (P<0.05). Among 
those candidate methylated genes, APC, BMP6, BRCA1 and P16 displayed higher 
methylation proportion in the matched lymph node metastasis than that found in 
the normal tissue (P<0.05). The pathway analysis revealed that BMP6, BRCA1 and 
P16 have a role in prevention of neoplasm metastasis.
CONCLUSIONS: The results of the present study showed methylation heterogeneity 
between primary tumors and metastatic lesion. The contribution of aberrant 
methylation alterations of BMP6, BRCA1 and P16 genes in lymph node metastasis 
might provide a further clue to establish useful biomarkers for screening 
metastasis.