DNA methylation is the best characterised epigenetic change so far. However, its role in
breast cancer metastasis has not as yet been elucidated. The aim of this study was to investigate the differences between the methylation profiles characterising primary tumours and their corresponding positive or negative for
metastasis lymph nodes (LN) and correlate these with tumour metastatic potential. Methylation signatures of
Caveolin-1, CXCR4, RAR-β,
Cyclin D2 and Twist gene promoters were studied in 30
breast cancer primary lesions and their corresponding
metastasis-free and tumour-infiltrated LN with Methylation-Specific PCR. CXCR4 and
Caveolin-1 expression was further studied by immunohistochemistry. Tumours were typified by methylation of RAR-β and hypermethylation of Cyclin-D2 and Twist gene promoters. Tumour patterns were highly conserved in tumour-infiltrated LN. CXCR4 and
Caveolin-1 promoter methylation patterns differentiated between node-negative and metastatic tumours. Nodal
metastasis was associated with tumour and lymph node profiles of extended methylation of
Caveolin-1 and lack of CXCR4 hypermethylation. Immunodetection studies verified CXCR4 and
Caveolin-1 hypermethylation as gene silencing mechanism. Absence of
Caveolin-1 expression in stromal cells associated with tumour aggressiveness while strong
Caveolin-1 expression in tumour cells correlated with decreased 7-year disease-free survival. Methylation-mediated activation of CXCR4 and inactivation of
Caveolin-1 was linked with nodal
metastasis while intratumoral
Caveolin-1 expression heterogeneity correlated with
disease progression. This evidence contributes to the better understanding and, thereby, therapeutic management of
breast cancer metastasis process.