What is miR-21-5p and what does it do in cancer?

miR-21-5p is one of the first and most extensively studied oncogenic miRNAs ever identified. It was among the first miRNAs found to be consistently overexpressed across multiple cancer types, earning the unofficial title of 'the most universally overexpressed miRNA in human cancer.' Mechanistically, miR-21-5p targets and suppresses several critical tumor suppressor genes: PTEN (a key inhibitor of the PI3K/Akt pro-growth pathway), PDCD4 (programmed cell death protein 4, an apoptosis regulator), RECK (a matrix metalloprotease inhibitor that prevents invasion), and others. By silencing these tumor suppressors, miR-21-5p allows cancer cells to proliferate without normal growth constraints, evade apoptosis, and invade surrounding tissue. In the Yenos validation, miR-21-5p achieved 93.8% per-marker accuracy (36 of 37 cancer samples correctly identified).