\[Abstract\]Lin28 is a highly conservative RNA-binding protein. It can bind to the terminal loop of the precursor of let-7 family miRNAs and block the maturation of let-7. Lin28/let-7 signal pathway is involved in the stem cell pluripotency and tumor development. Combined transfection of Lin28, OCT4, SOX2, and NANOG can reprogram human somatic cells into pluripotent stem cells. Tumors with high expression of Lin28/Lin28B are often poorly differentiated and have poor prognoses.