title: Differential effects of p19(Arf) and p16(Ink4a) loss on senescence of murine bone marrow-derived preB cells and macrophages.
abstract: Establishment of cell lines from primary mouse embryo fibroblasts depends on loss of either the Arf tumor suppressor or its downstream target, the p53 transcription factor. Mouse p19(Arf) is encoded by the Ink4a-Arf locus, which also specifies a second tumor suppressor protein, the cyclin D-dependent kinase inhibitor p16(Ink4a). We surveyed bone marrow-derived cells from wild-type, Ink4a-Arf-null, or Arf-null mice for their ability to bypass senescence during continuous passage in culture. Unlike preB cells from wild-type mice, those from mice lacking Arf alone could be propagated indefinitely when placed onto stromal feeder layers engineered to produce IL-7. The preB cell lines remained diploid and IL-7-dependent and continued to express elevated levels of p16(Ink4a). By contrast, Arf-null bone marrow-derived macrophages that depend on colony-stimulating factor-1 for proliferation and survival in culture initially grew at a slow rate but gave rise to rapidly and continuously growing, but still growth factor-dependent, variants that ceased to express p16(Ink4a). Wild-type bone marrow-derived macrophages initially expressed both p16(Ink4a) and p19(Arf) but exhibited an extended life span when p16(Ink4a) expression was extinguished. In all cases, gene silencing was accompanied by methylation of the Ink4a promoter. Therefore, whereas Arf loss alone appears to be the major determinant of establishment of murine fibroblast and preB cell lines in culture, p16(Ink4a) provides an effective barrier to immortalization of bone marrow-derived macrophages.
authors.affiliation: Department of Tumor Cell Biology and Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Randle
authors.forename: F
authors.initials: F
authors.lastname: Zindy
authors.forename: C J
authors.initials: CJ
authors.lastname: Sherr
authors.forename: M F
authors.initials: MF
authors.lastname: Roussel
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects; D001854:Bone Marrow Cells / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects; D002461:Cell Line, Transformed; D019070:Cell Lineage; D002472:Cell Transformation, Viral; D016922:Cellular Senescence / Q000502:physiology*; D018920:Coculture Techniques; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D019175:DNA Methylation; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation; D020868:Gene Silencing; D019942:Genes, p16; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013539:Simian virus 40 / Q000502:physiology; D014158:Transcription, Genetic; D025803:Tumor Suppressor Protein p14ARF
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D018076:DNA, Complementary; D011506:Proteins; D025803:Tumor Suppressor Protein p14ARF