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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.

SUBMITTER: Fishler T

PROVIDER: S-EPMC7316381 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of Chk1 and p53.

Fishler T T Li Y-Y YY Wang R-H RH Kim H-S HS Sengupta K K Vassilopoulos A A Lahusen T T Xu X X Lee M-H MH Liu Q Q Elledge S-J SJ Ried T T Deng C-X CX

Oncogene 20100517 28

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 mamm ...[more]

PMID: 20473325

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Project description:BACKGROUND: Elevated expression of focal adhesion kinase (FAK) occurs in numerous human cancers including colon-, cervix- and breast cancer. Although several studies have implicated FAK in mammary tumour formation induced by ectopic oncogene expression, evidence supporting a role for FAK in spontaneous mammary tumour development caused by loss of tumour suppressor genes such as p53 is lacking. Alterations in the tumour suppressor gene p53 have been implicated in over 50% of human breast cancers. Given that elevated FAK expression highly correlates with p53 mutation status in human breast cancer, we set out to investigate the importance of FAK in p53-mediated spontaneous mammary tumour development. METHODS: To directly assess the role of FAK, we generated mice with conditional inactivation of FAK and p53. We generated female p53(lox/lox)/FAK(+/+)/WapCre, p53(lox/lox)/FAK(flox/+)/WapCre and p53(lox/lox)/FAK(flox/-)/WapCre mice, and mice with WapCre-mediated conditional expression of p53(R270H), the mouse equivalent of human p53(R273H) hot spot mutation, together with conditional deletion of FAK, P53(R270H/+)/FAK(lox/+)/WapCre and p53(R270H/+)/FAK(flox/-)/WapCre mice. All mice were subjected to one pregnancy to induce WapCre-mediated deletion of p53 or expression of p53 R270H, and Fak genes flanked by two loxP sites, and subsequently followed the development of mammary tumours. RESULTS: Using this approach, we show that FAK is important for p53-induced mammary tumour development. In addition, mice with the mammary gland-specific conditional expression of p53 point mutation R270H, the mouse equivalent to human R273H, in combination with conditional deletion of Fak showed reduced incidence of p53(R270H)-induced mammary tumours. In both models these effects of FAK were related to reduced proliferation in preneoplastic lesions in the mammary gland ductal structures. CONCLUSIONS: Mammary gland-specific ablation of FAK hampers p53-regulated spontaneous mammary tumour formation. Focal adhesion kinase deletion reduced proliferative capacity of p53 null and p53(R270H) mammary epithelial cells but did not lead to increased apoptosis in vivo. Our data identify FAK as an important regulator in mammary epithelial cell proliferation in p53-mediated and p53(R270H)-induced mammary tumour development.

Dataset Information

Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of Chk1 and p53.

Publications

Genetic instability and mammary tumor formation in mice carrying mammary-specific disruption of Chk1 and p53.

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