Escape from premature senescence is not sufficient for oncogenic transformation by Ras.
Resistance of primary cells to transformation by oncogenic Ras has been attributed to the induction of replicative growth arrest. This irreversible 'fail-safe mechanism' resembles senescence and requires induction by Ras of p19ARF and p53 (refs 3-5). Mutation of either p19ARF or p53 alleviates Ras-induced senescence and facilitates oncogenic transformation by Ras. Here we report that, whereas Rb and p107 are each dispensable for Ras-induced replicative arrest, simultaneous ablation of both genes disrupts Ras-induced senescence and results in unrestrained proliferation. This occurs despite activation by Ras of the p19ARF /p53 pathway, identifying pRb and p107 as essential mediators of Ras-induced antiproliferative p19ARF/p53 signalling. Unexpectedly, in contrast to p19ARF or p53 deficiency, loss of Rb/p107 function does not result in oncogenic transformation by Ras, as Ras-expressing Rb-/-/p107-/- fibroblasts fail to grow anchorage-independently in vitro and are not tumorigenic in vivo. These results demonstrate that in the absence of both Rb and p107 cells are resistant to p19ARF/p53-dependent protection against Ras-induced proliferation, and uncouple escape from Ras-induced premature senescence from oncogenic transformation.
Peeper
D S
DS
Division of Molecular Carcinogenesis and Center for Biomedical Genetics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Dannenberg
J H
JH
Douma
S
S
te Riele
H
H
Bernards
R
R
D000818:Animals; D015153:Blotting, Western; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology; D005347:Fibroblasts; D005786:Gene Expression Regulation; D016161:Genes, Retinoblastoma; D011905:Genes, ras; D006131:Growth Inhibitors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107; D012190:Retroviridae / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
D006131:Growth Inhibitors; D009687:Nuclear Proteins; D011506:Proteins; C493844:RBL1 protein, human; C489485:Rbl1 protein, mouse; D050720:Retinoblastoma-Like Protein p107; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53