hsa-miR-21-5p miREIA (microRNA, miRNA)

MicroRNAs (miRNAs) are small non-coding RNA molecules, approximately 22 nucleotides in length that regulate gene translation through silencing or degradation of target mRNAs. They are involved in multiple biological processes, including differentiation and proliferation, metabolism, hemostasis, apoptosis or inflammation, and in the pathophysiology of many diseases. Numerous studies have suggested circulating miRNAs as promising diagnostic and prognostic biomarkers of many diseases.

hsa-miR-21-5p stands out as the most representative miRNA biomarker as it belongs to the first identified miRNA molecules. hsa-miR-21-5p is a circulating miRNA, strongly conserved through evolution, which has been extensively investigated in a range of studies of various diseases, such as cancer, cardiovascular disease, pulmonary diseases, regulation of immunological processes, and many others.

hsa-miR-21-5p was identified as a typical onco-miRNA. It modulates the expression of multiple cancer-related target genes and is dysregulated in various tumors. Besides tissues, recent evidence indicates the presence of miR-21-5p in various types of extracellular fluid, such as plasma, serum, CSF, saliva, gastric juice, pancreatic juice, sputum, and pancreatic cyst fluid. Up-regulated hsa-miR-21-5p could promote tumor growth, metastasis and invasion and reduce sensitivity to chemotherapy. The evidence from published meta-analyses revealed that high expression level of hsa-miR-21-5p was a negative predictor of survival in various cancers.
hsa-miR-21-5p is involved in many types of malignancies including brain cancer, lung cancer, colorectal cancer, pancreatic cancer, breast cancer, gastric cancer, esophageal cancer and hepatocellular carcinoma.

Besides altered expression of hsa-miR-21-5p in various malignancies, this miRNA is highly expressed in the cardiovascular system. Recent studies have revealed that its expression in the heart is dysregulated under cardiovascular disease conditions such as proliferative vascular disease, cardiac hypertrophy and heart failure or ischemic heart disease. hsa-miR-21-5p has been found to play important roles in vascular smooth muscle cell proliferation and apoptosis, cardiac cell growth and death, calcific aortic valve disease and cardiac fibroblast functions.