The Epigenomic Revolution in Breast Cancer

From the first identification of aberrant DNA methylation in primary tumors in humans more than 3 decades ago, progress in cancer epigenetics research has been exponential. For many years, cancer epigenetics studies relied on the identification of DNA methylation and histone modifications at specific genes. Those studies laid the foundation for the field and revealed the epigenetic alterations as hallmarks of cancer, as well as the crucial role of epigenetic mechanisms in tumorigenesis. The introduction of next-generation sequencing and array-based technologies for analyzing epigenetic states has accelerated our understanding about cancer and have become potent tools in our fight against the disease. Findings emerging from epigenome-wide analyses have led to new discoveries with remarkable clinical applications. This review summarizes the gene-specific epigenetic alterations common in breast cancer and discusses the recent advances in breast cancer epigenomics, focusing on their contribution to diagnosis, prognosis, patient stratification, and treatment of the disease.