Methylation profile of human breast cancer: A posible biomarker for the detection of circulating tumor cells.

MARZESE, DIEGO; GAGO, FRANCISCO; VARGAS ROIG, LAURA; ROQUÉ, MARÍA

Orange County Convention Center, Orlando, FL, Estados Unidos

Congreso; ASCO Annual Meeting 2009; 2009

American Society of Clinical Oncology

Background: Genetic and epigenetic events are complementary mechanisms involved in breast carcinogenesis. One of the most common epigenetic mechanisms by which genes are silenced is the aberrant methylation of their promoter CpG islands, i.e. hypermethylation in promoters of Tumor Suppressor Genes. The identification of circulating tumor cells (CTCs) in the blood of cancer patients, based on their aberrant methylation profile, appears as a potential tool for early detection and provides therefore the promise of a non-invasive and affordable cancer detection test. Methods: The methylation status of 26 cancer-related regions was studied, using Methyl Specific-Multiplex Ligation dependent Probe Amplification (MS-MLPA) assay in invasive breast tumors (n=24), axillary lymph nodes (n= 5), and normal breast tissue (n=2). A nested-Methyl Specific PCR (Nested-MSP) was designed for one of the methylated regions in the tumor suppressor gene rassf1A, to identify CTCs in peripheral blood samples. Blood samples from non tumor individuals were used as control. Results:We observed aberrant methylation of one or more of the 26 studied gene regions in all the breast cancer samples. The profiles were specific for each tumor. The more frequently aberrant methylated genes were: rassf1A promoter (62.5%), esr1 (54.17%), apc (54.17%) and rassf1A exon 1 (50%). Absence of aberrant methylation was confirmed in normal breast tissues. The specific methylation profile of tumors could be used to identify the metastasis origin in a patient with a left-sided breast tumor and bilateral tumor invasion of axillary lymph nodes. MS-MLPA revealed identical aberrant methylation patterns in both lymph nodes, revealing a left-sided origin of the right-sided lymph node. For the detection of CTCs in blood, a Nested-MSP on rassf1A was designed. This method allowed the detection of CTCs in the peripheral blood of a cancer patient by their aberrant rassf1A methylation. A healthy age-matched control blood sample revealed absence of CTCs. Conclusions: The identification of the methylation profile of the tumor by MS-MLPA allowed to establish the metastasis origin of invaded axillary lymph nodes and to detect CTCs in peripheral blood of a cancer patient.