MicroRNA signatures: clinical biomarkers for the diagnosis and treatment of breast cancer.

Recognition that breast cancer is a heterogeneous disease in which each patient's tumor has specific characteristics has led to a search for biomarkers and combinations of markers (signatures) to improve the diagnosis, prognostic classification and prediction of therapeutic benefit versus toxicity for individual tumors and patients. Many microRNAs (miRNAs) are aberrantly expressed in cancer and seem to influence tumor behavior and progression. miRNAs have great potential to evolve into effective biomarkers in the clinic because of their extreme stability and ease of detection. However, there are several major technical challenges as well as numerous discrepancies among currently reported miRNA signatures. In this review, we discuss the use of miRNA signatures for breast cancer treatment and discuss the challenges in the field.