Breast cancer epigenetics

Alterations in gene expression due to modifications in histone acetylation and DNA methylation at promoter regions of genes are the essence of what we refer to as epigenetics. These alterations are not modifications in primary nucleotide sequences but rather control what is transcribed. The impact of these alterations has been shown to drive both the initiation and progression of breast cancer as well as the control of responses within the tumor microenvironment which drive these processes, and as such, have become an active area of investigation for novel therapeutics. Several drugs that target epigenetic alterations, including inhibitors of histone deacetylase and DNA methyltransferase, are currently approved for treatment of hematological malignancies and are under investigation both preclinically and clinically in solid tumors. In this chapter, we review the critical role of epigenetics in breast cancer including the potential for modulation of known epigenetic instances affecting breast cancer progression and epigenetic alterations as biomarkers determining breast cancer prognosis and response to therapy. We highlight initial promising results to date with use of epigenetic modifiers in patients with breast cancer and the ongoing challenges involved in the successful establishment of these agents for the treatment of breast cancer.