title: Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of Chk1 and p53.
abstract: Checkpoint kinase 1 (Chk1) is a key element in the DNA-damage response pathway that is required for maintaining genomic stability. To study the potential role of Chk1 in mammary tumorigenesis, we disrupted it using a Cre/loxP system. We showed that although Chk1 heterozygosity caused abnormal development of the mammary gland, it was not sufficient to induce tumorigenesis. Simultaneous deletion of one copy of p53 failed to rescue the developmental defects; however, it synergistically induced mammary tumor formation in Chk1(+/-);MMTV-Cre animals with a median time to tumor latency of about 10 months. Chk1 deficiency caused a preponderance of abnormalities, including prolongation, multipolarity, misalignment, mitotic catastrophe and loss of spindle checkpoint, that are accompanied by reduced expression of several cell cycle regulators, including Mad2. On the other hand, we also showed that Chk1 deficiency inhibited mammary tumor formation in mice carrying a homozygous deletion of p53, uncovering a complex relationship between Chk1 and p53. Furthermore, inhibition of Chk1 with a specific inhibitor, SB-218078, or acute deletion of Chk1 using small hairpin RNA killed mammary tumor cells effectively. These data show that Chk1 is critical for maintaining genome integrity and serves as a double-edged sword for cancer: although its inhibition kills cancer cells, it also triggers tumorigenesis when favorable mutations are accumulated for cell growth.
authors.affiliation: Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, MD, USA.
authors.forename: T
authors.initials: T
authors.lastname: Fishler
authors.forename: Y-Y
authors.initials: YY
authors.lastname: Li
authors.forename: R-H
authors.initials: RH
authors.lastname: Wang
authors.forename: H-S
authors.initials: HS
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Sengupta
authors.forename: A
authors.initials: A
authors.lastname: Vassilopoulos
authors.forename: T
authors.initials: T
authors.lastname: Lahusen
authors.forename: X
authors.initials: X
authors.lastname: Xu
authors.forename: M-H
authors.initials: MH
authors.lastname: Lee
authors.forename: Q
authors.initials: Q
authors.lastname: Liu
authors.forename: S-J
authors.initials: SJ
authors.lastname: Elledge
authors.forename: T
authors.initials: T
authors.lastname: Ried
authors.forename: C-X
authors.initials: CX
authors.lastname: Deng
mesh_terms: D000818:Animals; D001483:Base Sequence; D000071877:Checkpoint Kinase 1; D017931:DNA Primers; D042822:Genomic Instability; D008325:Mammary Neoplasms, Experimental / Q000235:genetics* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D011494:Protein Kinases / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D032681:Spectral Karyotyping; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D017931:DNA Primers; D016159:Tumor Suppressor Protein p53; D011494:Protein Kinases; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse
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