MicroRNAs controlling invasion and metastasis in breast cancer

MicroRNAs (miRNAs) are small non-coding RNAs of ~22 nucleotides that function as negative regulators of gene expression by either inhibiting translation or inducing degradation of messenger RNAs (mRNAs). Aberrant expression of miRNAs expression is associated with initiation and progression of breast cancer where they act as oncogenes or tumor suppressors contributing to tumorigenesis. Deregulated miRNAs represent novel prognostic tumor biomarkers and potential therapeutic targets in cancer. Recently, several miRNAs have been shown to initiate invasion and metastasis of cancer cells, and thus they have been denominated as metastamiRs. Here, we present a review of the current knowledge of metastamiRs in breast cancer.