Two subgroups of breast tumors have been identified based on epigenetic alterations. These findings were published in Molecular Oncology (2014; doi:10.1016/j.molonc.2014.10.012).

The identification of patients with high-risk breast cancer is key to knowing whether a patient will require only the removal of the tumor by surgery or if she will need additional chemotherapy to ensure removal of all breast cancer cells. Currently, known genetic mutations and expression patterns are determined, but the puzzle of the genetics of the disease remains a large unfinished part.

This study of the epigenetic patterns of breast cancer and its clinical consequences was led by Manel Esteller, MD, PhD, director of the Program Epigenetics and Cancer Biology (PEBC) at Bellvitge Biomedical Research Institute (IDIBELL), Professor of Genetics at the University of Barcelona, and researcher at the  Institucio Catalana de Recerca i Estudis Avançats (ICREA) in Spain.

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“We’ve analyzed epigenetic alterations, namely the chemical signal called DNA methylation in 500 breast tumors and have compared the patterns obtained with the clinical behavior of these cancers,” said Esteller.

“We note that there are two subgroups of breast tumors by epigenome: one which we have called epi-basal, characterized by loss of epigenetic marks causing breakage of chromosomes and the other that we have called epi-luminal B, that presents epigenetic inactivation of genes that should protect us from cancer and these altered cells can no longer do it.”

The researcher pointed out that the epi-luminal B subtype behaves as a particularly aggressive disease, and is associated with reduced survival of patients. This information can be useful in recommending that these tumors not be conformed to surgery, as it will probably be necessary to administer adjuvant chemotherapy. In other words, surgery alone may be curative in tumors with a more benign epigenetic pattern thus avoiding the side effects of chemotherapy, Esteller explained.

Their study concluded that a few selected proxy markers can detect the distinct DNA methylation-based subtypes, and that can provide valuable information on the patients’ prognosis.