ABSTRACT
The microRNA let-7 family,functioning as a tumor suppressor,has emerged as a regulator of stem cell differentiation and tumor repression.The RNA-binding protein lin28 is a stem cell pluripotency factor,which contributes to the maintenance of stem cell characteristics and promoting cell malignant transformation.lin28 can block the maturity of let-7 by combining with the precursors of let-7 family miRNAs,which is itself able to repress lin28 by binding to the 3'-UTR of lin28 transcripts,thus forming a feedback loop.The double-negative feedback loop comprising lin28 and let-7 is involved in several biological processes such as differentiation of stem cell,tumorigenesis,invasion and metastasis,drug resistance and relapse,which couldbe a potential target for cancer therapy.