LIN28 is thought to regulate the self-renewal of stem cells. In nematodes, the LIN28 homolog lin-28 is a heterochronic gene that determines the onset of early larval stages of developmental events in Caenorhabditis elegans, by regulating the self-renewal of nematode stem cells in the skin (called seam cells) and vulva (called VPCs) during development. In mice, LIN28 is highly expressed in mouse embryonic stem cells and during early embryogenesis.It acts as a suppressor of microRNA (miRNA) biogenesis by specifically binding the precursor let-7 (pre-let-7), a miRNA precursor. Lin28B is high expression in testis, fetal liver, placenta and in hepatocellular carcinoma (HCC).