Oncology Central

Epigenetic study of breast cancer reveals two epigenetic subtypes

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An international team of researchers studying DNA methylation-based signatures associated with breast cancer have identified two new epigenetic subtypes of the disease. The work, published recently in Molecular Oncology, is thought to have clinical relevance, including in the development of treatment plans.

As the most common cancer in women, breast cancer will affect one in nine women throughout their lifetime. While significant progress has been made in increasing life expectancy for breast cancer patients, via prevention and early detection alongside the use of adjuvant chemotherapy, much remains to be done.

Identifying patients with breast cancers with a high risk of recurrence is vital in anticipating whether surgical removal of the tumor will be sufficient or whether additional chemotherapy will be required to ensure eradication of the cancer cells.

Although the expression patterns and genetic mutations of breast cancer are now largely known, the genetics of this disease have remained elusive. Thanks to this recently published study, new progress seems to have been made in the uncovering the genetics of the disease. The researchers involved in the study recorded findings that detail the epigenetic patterns of breast cancer as well as their clinical consequences.

The team analyzed DNA methylation in 500 tumor samples and compared the resultant patterns to the clinical manifestations of corresponding cancer types. As a result, two new subtypes of breast cancer were identified, Epi-Basal and Epi-Luminal B.

Investigator Manel Estellar (Bellvitge Biomedical Research Institute, Spain) further explained the results: “We note that there are two subgroups of breast tumors by epigenome: one which we have called Epi-Basal, characterized by loss of epigenetic mark causing the 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.”

Estellar went on to highlight the clinical significance of this work: “The subtype Epi-Luminal B behaves particularly aggressively…and is associated with reduced survival of patients.” Such knowledge may be useful to clinicians, allowing them to advise that these tumors have a higher risk of recurrence and that adjuvant chemotherapy would most likely be necessary. By contrast, in those tumors with a more benign epigenetic pattern, surgery alone could be curative, thus patients may not need to experience the side effects of chemotherapy.”

Sources: Stefansson OA, Moran S, Gomez A et al. A DNA methylation-based definition of biologically distinct breast cancer subtypes. Mol. Oncol. doi: 10.1016/j.molonc.2014.10.012. (2014) [Epub ahead of print]; Bellvitge Biomedical Research Institute (IDIBELL) press release

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