MicroRNAs and gene regulation in breast cancer.

MicroRNAs (miRs) are non-protein-coding small RNAs that control the gene expression posttranscriptionally. miRs can regulate different cellular functions as well as many pathological conditions. Dysregulated miR expression profiles have been identified in different cancer types including lung cancer, breast cancer, and prostate cancer. The expression of miRs varies according to their roles in each specific cancer type. Although many miRs and their target genes have been identified in different cancers, data are still scant to validate those target genes and the mechanistic role of these miRs. The possibility of targeting cancer-associated miRs is suggested to open a new field for cancer therapy. Therapeutic strategies targeting miRs involve neutralization of the oncogenic miRs by antagomirs using locked nucleic acid oligonucleotides, miR sponges, or the restoration/overexpression of tumor-suppressing miRs that are downregulated or depleted in cancers. Although it is suggested that therapeutic applications of miRs in different pathological conditions will make a huge revolution in gene therapy, there is still an enormous challenge in employing these strategies efficiently in cancer inhibition, seemingly, due to the complexity of cancer and the current inefficient development of delivery systems for the therapeutic miRs.