title: Combined loss of INK4a and caveolin-1 synergistically enhances cell proliferation and oncogene-induced tumorigenesis: role of INK4a/CAV-1 in mammary epithelial cell hyperplasia.
abstract: Tumorigenesis is a multistep process that involves a series of genetic changes or "multiple hits," leading to alterations in signaling, proliferation, immortalization, and transformation. Many of the molecular factors that govern tumor initiation and progression remain unknown. Here, we evaluate the transformation suppressor potential of caveolin-1 (Cav-1) and its ability to cooperate with a well established tumor suppressor, the INK4a locus. To study the effects of loss of caveolin-1 on cellular transformation, we established immortalized primary mouse embryonic fibroblasts (MEFs) expressing and lacking caveolin-1 by interbreeding Cav-1 (+/+) and Cav-1 (-/-) mice with INK4a (-/-) mice. Analysis of these cells reveals that loss of caveolin-1 confers a significant growth advantage, as measured via cellular proliferation and cell cycle analysis. Loss of caveolin-1 in the INK4a (-/-) genetic background results in constitutive hyperactivation of the p42/44 MAP kinase cascade, decreased expression of p21(Cip1), as well as cyclin D1 and PCNA overexpression, consistent with their hyperproliferative phenotype. Importantly, in cells lacking Cav-1 expression, transformation by activated oncogenes (H-Ras(G12V) or v-Src) results in increased tumor growth in vivo (up to >40-fold). Finally, INK4a (-/-)/Cav-1 (-/-) mice demonstrate disturbed mammary epithelial ductal morphology, with hyperplasia, increased side-branching, and fibrosis. Our results provide important new evidence for the transformation suppressor properties of Cav-1 and the first molecular genetic evidence that Cav-1 cooperates with a tumor suppressor, namely the INK4a genetic locus.
authors.affiliation: Department of Molecular Pharmacology, Albert Einsten Cancer Center, Albert Einsten College of Medicine, Bronx, New York 10461, USA.
authors.forename: Terence M
authors.initials: TM
authors.lastname: Williams
authors.forename: Hyangkyu
authors.initials: H
authors.lastname: Lee
authors.forename: Michelle W-C
authors.initials: MW
authors.lastname: Cheung
authors.forename: Alex W
authors.initials: AW
authors.lastname: Cohen
authors.forename: Babak
authors.initials: B
authors.lastname: Razani
authors.forename: Puneeth
authors.initials: P
authors.lastname: Iyengar
authors.forename: Philipp E
authors.initials: PE
authors.lastname: Scherer
authors.forename: Richard G
authors.initials: RG
authors.lastname: Pestell
authors.forename: Michael P
authors.initials: MP
authors.lastname: Lisanti
mesh_terms: D000818:Animals; D015153:Blotting, Western; D051242:Caveolin 1; D022461:Caveolins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D003433:Crosses, Genetic; D019938:Cyclin D1 / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000502:physiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D018450:Disease Progression; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000473:pathology*; D005347:Fibroblasts / Q000378:metabolism; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006965:Hyperplasia; D015151:Immunoblotting; D008321:Mammary Glands, Animal / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008957:Models, Genetic; D009368:Neoplasm Transplantation; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D012190:Retroviridae; D015398:Signal Transduction; D013997:Time Factors; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; C493957:Cdkn1a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D019938:Cyclin D1; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases