title: The significance of p16INK4a in cell defenses against transformation.
abstract: Human cells, including fibroblast strains that have been immortalized by telomerase, are much more resistant to transformation than rodent cells. Most of the experimental evidence suggests that transformation of human fibroblasts requires inactivation of both the retinoblastoma (pRb) and p53 tumor suppressors as well as the addition of one or more dominant oncogenes. By starting with strains of primary fibroblast (Leiden and Q34 cells) that are genetically deficient for p16INK4a, we have been able to generate anchorage independent colonies simply by addition of telomerase (hTERT) and either Ras or Myc. Importantly, the transformed cells appear to retain pRb and p53 functions and are essentially diploid. Whereas Leiden cells expressing the individual oncogenes did not form tumors in mice, the combination of hTERT, Myc and Ras enabled them to become tumorigenic, albeit at a frequency suggestive of an additional genetic event. Significantly, we have obtained karyotypically stable tumors without the need to use DNA tumor virus oncoproteins and without deliberate ablation of p53.
authors.affiliation: Cancer Research United Kingdom, London Research Institute, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Drayton
authors.forename: Sharon
authors.initials: S
authors.lastname: Brookes
authors.forename: Janice
authors.initials: J
authors.lastname: Rowe
authors.forename: Gordon
authors.initials: G
authors.lastname: Peters
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D016922:Cellular Senescence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D016271:Proto-Oncogene Proteins c-myc; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D019098:Telomerase; D018631:ras Proteins