Differential Effects of p19Arfand p16Ink4aLoss on Senescence of Murine Bone Marrow-Derived preB Cells and Macrophages

• Published in: Proceedings of the National Academy of Sciences - PNAS 2001-08, Vol.98 (17), p.9654-9659
• Main Authors: Randle, David H., Zindy, Frederique, Sherr, Charles J., Roussel, Martine F.
• Format: Article
• Language: English
• Subjects: B lymphocytes; Biological Sciences; Cell growth; Cell lines; Cells; Cellular senescence; Cultured cells; Diploidy; L cells; Macrophages; Mice
• ISSN: 0027-8424

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 p19Arfis encoded by the Ink4a-Arf locus, which also specifies a second tumor suppressor protein, the cyclin D-dependent kinase inhibitor p16Ink4a. 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 p16Ink4a. 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 p16Ink4a. Wild-type bone marrow-derived macrophages initially expressed both p16Ink4aand p19Arfbut exhibited an extended life span when p16Ink4aexpression 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, p16Ink4aprovides an effective barrier to immortalization of bone marrow-derived macrophages.