Epigenetic and Breast Cancer Sub-types

Recent work by Dedeurwaerder et al. has shown that epigenetics really does play a major role in development of breast cancer sub-types. This discovery came through the study of DNA methylation’s level and the associated breast cancer subtype. It was previously known that epigenetic mechanisms such as histone methylation play an important role in development of tumors and that DNA methylation is usually found in regions of the genome that are functionally silenced. We know there are genes called estrogen-receptor on breast tissues and when estrogen binds to them, they stimulate cell proliferation, which could subsequently lead to mutations and cancer development. As a result, estrogen-receptor genes are usually over expressed in majority of breast tumors. Until this study, the details of existing various sub-types of tumors that were as a result of DNA methylation were not yet known. The study was performed on numerous independent breast tissue samples known to be cancerous by assaying for the level of DNA methylation. They found two distinct types of tumors, positive and negative for estrogen receptor, and each with different levels of DNA methylation. Further analysis revealed that the level of DNA methylation was inversely related to the activation of

estrogen-receptor genes and DNA methylation was acting to negatively regulate the expression of these genes, i.e. DNA was highly methylated when the estrogen-receptor genes were not expressed. This revelation could redefine our current understanding of cancer, and perhaps open doors for research on the role of epigenetic on other diseases. Most importantly, this discovery could potentially lead to improved and more efficient cancer diagnosis and treatment based on the sub-type of cancer.

S. Dedeurwaerder et al. Epigenetic Portraits Of Human Breast Cancers. Annals of

Oncology, 2011; 22: Supplement 2

Retrieved May 26, 2011, from

http://annonc.oxfordjournals.org/content/22/suppl_2.toc