Discovery of an oncogenic activity in p27Kip1that causes stem cell expansion and a multiple tumor phenotype

Publisher Website
Google Scholar
Abstract
The cell cycle inhibitor p27Kip1also has cyclin–cyclin-dependent kinase (CDK)-independent functions. To investigate the significance of these functions in vivo, we generated a knock-in mouse in which four amino acid substitutions in thecdkn1bgene product prevent its interaction with cyclins and CDKs (p27CK−). In striking contrast to complete deletion of thecdkn1bgene, which causes spontaneous tumorigenesis only in the pituitary, the p27CK−protein dominantly caused hyperplastic lesions and tumors in multiple organs, including the lung, retina, pituitary, ovary, adrenals, spleen, and lymphomas. Moreover, the high incidence of spontaneous tumors in the lung and retina was associated with amplification of stem/progenitor cell populations. Therefore, independently of its role as a CDK inhibitor, p27Kip1promoted stem cell expansion and functioned as a dominant oncogene in vivo. Thus, the p27CK−mouse unveils a dual role for p27 during tumorigenesis: It is a tumor suppressor by virtue of its cyclin–CDK regulatory function, and also an oncogene through a cyclin–CDK-independent function. This may explain why thecdkn1bgene is rarely inactivated in human tumors, and the p27CK−mouse in which the tumor suppressor function is lost but the cyclin–CDK-independent—oncogenic—function is maintained may represent a more faithful model for the widespread role of p27 misregulation in human cancers than the p27 null.

This publication has 73 references indexed in Scilit: