MicroRNAs mediate therapeutic and preventive effects of natural agents in breast cancer

MicroRNAs (miRNAs) are a set of non-coding small RNA molecules that play a critical role in regulation of protein coding genes in cells. MiRNAs have been extensively studied as novel biomarkers, therapeutic targets, and new drugs in various human diseases. Breast cancer is a one of the leading tumor types significantly affecting women health worldwide. Over the past decade, a number of natural agents, such as paclitaxel and curcumin, have been applied for treatment and prevention of breast cancer due to their relatively low toxicity. However, the mechanisms of action have not been completely understood. Investigation on miRNAs is able to potentially provide a novel insight into better understanding the anticancer activities of these natural products. Given that a single miRNA can target multiple genes, theoretically, those genes involved in a certain phenotype can be clustered with one or a few miRNAs. Therefore, pleiotropic activities of natural agents should be interpreted by interactions between selected miRNAs and their targets. In this review, we summarize the latest publications related to the alterations of miRNAs by two natural agents (paclitaxel and curcumin) that are currently used in intervention of breast cancer, and conclude that the mechanism involving the regulation of miRNA expression is one of the keys to understand pleiotropic activities of natural agents.