MicroRNAs (miRNA) and Their Relationship with Diseases

Taking part in the noncoding RNA group, microRNAs (miRNAs) are approximately 22 nucleotides in length RNA molecules. The first studies on miRNAs focused on Caenorhabditis elegans, and the first miRNA gene lin-4 was discovered. To date, there are more than 5000 identified miRNAs, which are involved in the transcription and post-transcription regulation of gene expression and also play a role in several important biological events such as metabolism, cell differentiation, proliferation, and apoptosis. The increases and decreases in the levels of miRNAs have been associated with cancer, autoimmune, neurodegenerative, cardiovascular, and some respiratory diseases. In recent years, experimental studies have indicated that they act as oncogens or tumor suppressor genes in cancer development and that miRNAs in the bloodstream can be a good biomarker for cancer diagnosis and prognosis. In this review, the diagnostic–therapeutic uses of miRNAs and their relationship with diseases have been summarized.