Epigenetic changes are critical for development and progression of cancers, 
including breast cancer. Significant progress has been made in the basic 
understanding of how various epigenetic changes such as DNA methylation, histone 
modification, miRNA expression, and higher order chromatin structure affect gene 
expression. The present review will focus on methylation and demethylation of 
histones. While the acetylation of histones has been at the forefront of 
well-characterized post-translational modifications of histones, including the 
development of inhibitors targeting de-acetylating enzymes, the past few years 
have witnessed a dramatic increase in knowledge regarding the role of histone 
methylation/demethylation. This is an exciting and rapidly evolving area of 
research, with much promise for potential clinical intervention in several 
cancers including breast cancer. We also summarize efforts to identity DNA 
methylation signatures that could be prognostic and/or predictive markers in 
breast cancer, focusing on recent studies using genome-wide approaches. Finally, 
we briefly review the efforts made by both the National Institutes of Health 
Epigenome Project and The Cancer Genome Atlas, especially highlighting the study 
of breast cancer epigenetics, exciting technological advances, potential 
roadblocks, and future directions.