title: Relocalized p27Kip1 tumor suppressor functions as a cytoplasmic metastatic oncogene in melanoma.
abstract: The p27 tumor suppressor negatively regulates G1 cell cycle progression. However, human malignancies rarely select for deletion/inactivation of p27, a hallmark of tumor suppressor genes. Instead, p27 is degraded or relocalized to the cytoplasm in aggressive malignancies, supporting the notion that p27 sequestration from its nuclear cyclin:cyclin-dependent kinase (cdk) targets is critical. However, emerging cell biology data suggest a novel cdk-independent cytoplasmic function of p27 in cell migration. Here, we find cytoplasmic p27 in 70% of invasive and metastatic melanomas. In contrast, no cytoplasmic p27 was detected in noninvasive, basement membrane-confined melanoma in situ, suggesting a late oncogenic role for cytoplasmic p27 in metastasis. Targeted cytoplasmic expression of wild-type or non-cdk-binding p27 at subphysiologic levels induced melanoma motility and resulted in numerous metastases to lymph node, lung, and peritoneum. These observations point to a prominent role of cytoplasmic p27 in metastatic disease that is independent of cyclin:cdk regulation or mere nuclear loss.
authors.affiliation: Howard Hughes Medical Institute and Department of Cellular and Molecular Medicine, University of California at San Diego School of Medicine, La Jolla, California 92037-0686, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Denicourt
authors.forename: Cheryl C
authors.initials: CC
authors.lastname: Saenz
authors.forename: Brian
authors.initials: B
authors.lastname: Datnow
authors.forename: Xian-Shu
authors.initials: XS
authors.lastname: Cui
authors.forename: Steven F
authors.initials: SF
authors.lastname: Dowdy
mesh_terms: D000818:Animals; D002465:Cell Movement / Q000502:physiology; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D003593:Cytoplasm / Q000235:genetics; D016147:Genes, Tumor Suppressor; D006801:Humans; D007150:Immunohistochemistry; D008545:Melanoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008546:Melanoma, Experimental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness
chemical_list: D050760:Cyclin-Dependent Kinase Inhibitor p27