Defective DNA double-strand break repair underlies enhanced tumorigenesis and chromosomal instability in p27-deficient mice with growth factor-induced oligodendrogliomas.
The tumor suppressive activities of the Kip-family of cyclin-dependent kinase (cdk) inhibitors often go beyond their role directly regulating the cell cycle. In this study, we show that p27 enhances Rad51 accumulation during repair of double-strand DNA breaks. Progression of platelet-derived growth factor (PDGF)-induced oligodendrogliomas was accelerated in mice lacking the cyclin-cdk binding activities of p27(kip1). To understand how p27 deficiency contributes, cell lines were developed from RCAS-PDGF infection of nestin-tv-a brain progenitor cells in culture. p27 deficiency did not affect cell proliferation in early passage cell lines; however, the absence of p27 affected chromosomal stability. In p27-deficient cells, the activation of Atm and Chk2 and the accumulation of gamma-H2AX was unaffected when compared with wild-type cells, and the number of phospho-histone H3 staining mitotic cells was decreased, consistent with G2/M checkpoint activation. However, the percentage of Rad51 foci-positive cells was decreased, and the kinase activity that targets the C-terminus of BRCA2, regulating BRCA2/Rad51 interactions, was increased in lysates derived from p27-deficient cells. Increased numbers of chromatid breaks in p27-deficient cells that adapted to the checkpoint were also observed. These findings suggest that Rad51-dependent repair of double-stranded breaks was hindered in p27-deficient cells, leading to chromosomal instability, a hallmark of cancers with poor prognosis.
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WL
Program in Cell Biology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021 USA.
Miller
J P
JP
Squatrito
M
M
Holland
E
E
Resh
M D
MD
Koff
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A
D000818:Animals; D001932:Brain Neoplasms / Q000139:chemically induced / Q000235:genetics / Q000401:mortality / Q000473:pathology; D002455:Cell Division; D043171:Chromosomal Instability / Q000235:genetics*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000172:deficiency* / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair; D016195:G2 Phase; D017930:Genes, Reporter; D006133:Growth Substances / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009837:Oligodendroglioma / Q000139:chemically induced / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000502:physiology; D015996:Survival Rate
D006133:Growth Substances; D010982:Platelet-Derived Growth Factor; D050760:Cyclin-Dependent Kinase Inhibitor p27