Thinking Small: Circulating microRNAs as Novel Biomarkers for Diagnosis, Prognosis, and Treatment Monitoring in Breast Cancer

Abstract

Cancer initiation and progression are governed by both genetic and epigenetic events. Epigenetic alterations which include changes in DNA methylation, histone modifications, and noncoding RNA-mediated gene silencing are reversible and heritable. Aberrant epigenetic modifications are believed to be essential players in cancer initiation and progression. Recent advances in epigenetics have offered not only a deeper understanding of the underlying mechanisms of carcinogenesis but also new avenues for identification of clinically relevant putative biomarkers for the early detection, prognosis, monitoring of treatment response, and risk stratification of cancer patients. Following identification of cell-free nucleic acids in systematic circulation, cumulating evidences have demonstrated the potential of cell-free epigenetic biomarkers in the body fluids for cancer. Recently, the emergence of microRNAs as biomarkers has added an extra dimension to the “molecular signatures” of breast cancer. In this chapter, we summarize the currently published state-of-the-art research on the role of the circulating microRNAs in clinical utility for breast cancer, the most common cancer in women. In addition, we also discuss the current obstacles that have limited the routine use of epigenetic biomarkers and provide future perspectives, so that these novel cancer biomarkers can be readily developed for significant clinical improvement in the management of breast cancer patients.