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Sasatani M, Xi Y, Daino K, Ishikawa A, Masuda Y, Kajimura J, Piao J, Zaharieva EK, Honda H, Zhou G, Hamasaki K, Kusunoki Y, Shimura T, Kakinuma S, Shimada Y, Doi K, Ishikawa‐Fujiwara T, Sotomaru Y, Kamiya K. Rev1 overexpression accelerates N-methyl-N-nitrosourea (MNU)-induced thymic lymphoma by increasing mutagenesis. Cancer Sci 2024; 115:1808-1819. [PMID: 38572512 PMCID: PMC11145157 DOI: 10.1111/cas.16159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 02/28/2024] [Accepted: 03/10/2024] [Indexed: 04/05/2024] Open
Abstract
Rev1 has two important functions in the translesion synthesis pathway, including dCMP transferase activity, and acts as a scaffolding protein for other polymerases involved in translesion synthesis. However, the role of Rev1 in mutagenesis and tumorigenesis in vivo remains unclear. We previously generated Rev1-overexpressing (Rev1-Tg) mice and reported that they exhibited a significantly increased incidence of intestinal adenoma and thymic lymphoma (TL) after N-methyl-N-nitrosourea (MNU) treatment. In this study, we investigated mutagenesis of MNU-induced TL tumorigenesis in wild-type (WT) and Rev1-Tg mice using diverse approaches, including whole-exome sequencing (WES). In Rev1-Tg TLs, the mutation frequency was higher than that in WT TL in most cases. However, no difference in the number of nonsynonymous mutations in the Catalogue of Somatic Mutations in Cancer (COSMIC) genes was observed, and mutations involved in Notch1 and MAPK signaling were similarly detected in both TLs. Mutational signature analysis of WT and Rev1-Tg TLs revealed cosine similarity with COSMIC mutational SBS5 (aging-related) and SBS11 (alkylation-related). Interestingly, the total number of mutations, but not the genotypes of WT and Rev1-Tg, was positively correlated with the relative contribution of SBS5 in individual TLs, suggesting that genetic instability could be accelerated in Rev1-Tg TLs. Finally, we demonstrated that preleukemic cells could be detected earlier in Rev1-Tg mice than in WT mice, following MNU treatment. In conclusion, Rev1 overexpression accelerates mutagenesis and increases the incidence of MNU-induced TL by shortening the latency period, which may be associated with more frequent DNA damage-induced genetic instability.
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Grants
- Network-Type Joint Usage/Research Center for Radiation Disaster Medical Science at Hiroshima University, Nagasaki University, and Fukushima Medical University
- NIFS10KOBS015 National Institute for Fusion Science Collaborative Research Program
- NIFS13KOBA028 National Institute for Fusion Science Collaborative Research Program
- NIFS20KOCA004 National Institute for Fusion Science Collaborative Research Program
- Initiative for Realizing Diversity in the Research Environment (Specific Correspondence Type), a support project for the Development of Human Resources in Science and Technology conducted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 20710043 Japan Society for the Promotion of Science, JSPS KAKENHI
- 22310037 Japan Society for the Promotion of Science, JSPS KAKENHI
- 22710055 Japan Society for the Promotion of Science, JSPS KAKENHI
- JPMX08S08080294 Nuclear Energy S&T and Human Resource Development Project
- Initiative for Realizing Diversity in the Research Environment (Specific Correspondence Type), a support project for the Development of Human Resources in Science and Technology conducted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- Japan Society for the Promotion of Science, JSPS KAKENHI
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Affiliation(s)
- Megumi Sasatani
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
| | - Yang Xi
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
- Department of Biochemistry and Molecular Biology and Zhejiang Key Laboratory of Pathophysiology, School of Basic Medical Sciences, Health Science CenterNingbo UniversityNingboChina
| | - Kazuhiro Daino
- Department of Radiation Effects ResearchInstitute for Radiological Sciences, National Institutes for Quantum Science and TechnologyChibaJapan
| | - Atsuko Ishikawa
- Department of Radiation Effects ResearchInstitute for Radiological Sciences, National Institutes for Quantum Science and TechnologyChibaJapan
| | - Yuji Masuda
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
- Department of Genome DynamicsResearch Institute of Environmental Medicine, Nagoya UniversityNagoyaJapan
- Department of Molecular Pharmaco‐BiologyNagoya University Graduate School of MedicineNagoyaJapan
| | - Junko Kajimura
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
- Biosample Research Center, Radiation Effects Research FoundationHiroshimaJapan
| | - Jinlian Piao
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
- Gastroenterological and Transplant Surgery, Graduate School of Biomedical & Health SciencesHiroshima UniversityHiroshimaJapan
| | - Elena Karamfilova Zaharieva
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
| | - Hiroaki Honda
- Institute of Laboratory Animals, Tokyo Women's Medical UniversityTokyoJapan
| | - Guanyu Zhou
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
| | - Kanya Hamasaki
- Department of Molecular BiosciencesRadiation Effects Research FoundationHiroshimaJapan
| | - Yoichiro Kusunoki
- Department of Molecular BiosciencesRadiation Effects Research FoundationHiroshimaJapan
| | - Tsutomu Shimura
- Department of Environmental HealthNational Institute of Public HealthSaitamaJapan
| | - Shizuko Kakinuma
- Department of Radiation Effects ResearchInstitute for Radiological Sciences, National Institutes for Quantum Science and TechnologyChibaJapan
| | | | - Kazutaka Doi
- Department of Radiation Regulatory Science ResearchInstitute for Radiological Sciences, National Institutes for Quantum Science and TechnologyChibaJapan
| | | | - Yusuke Sotomaru
- Natural Science Center for Basic Research and DevelopmentHiroshima UniversityHiroshimaJapan
| | - Kenji Kamiya
- Department of Experimental OncologyResearch Institute for Radiation Biology and Medicine, Hiroshima UniversityHiroshimaJapan
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2
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Sunaoshi M, Amasaki Y, Hirano-Sakairi S, Blyth BJ, Morioka T, Kaminishi M, Shang Y, Nishimura M, Shimada Y, Tachibana A, Kakinuma S. The effect of age at exposure on the inactivating mechanisms and relative contributions of key tumor suppressor genes in radiation-induced mouse T-cell lymphomas. Mutat Res 2015; 779:58-67. [PMID: 26141385 DOI: 10.1016/j.mrfmmm.2015.06.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 05/15/2015] [Accepted: 06/07/2015] [Indexed: 06/04/2023]
Abstract
Children are considered more sensitive to radiation-induced cancer than adults, yet any differences in genomic alterations associated with age-at-exposure and their underlying mechanisms remain unclear. We assessed genome-wide DNA copy number and mutation of key tumor suppressor genes in T-cell lymphomas arising after weekly irradiation of female B6C3F1 mice with 1.2Gy X-rays for 4 consecutive weeks starting during infancy (1 week old), adolescence (4 weeks old) or as young adults (8 weeks old). Although T-cell lymphoma incidence was similar, loss of heterozygosity at Cdkn2a on chromosome 4 and at Ikaros on chromosome 11 was more frequent in the two older groups, while loss at the Pten locus on chromosome 19 was more frequent in the infant-irradiated group. Cdkn2a and Ikaros mutation/loss was a common feature of the young adult-irradiation group, with Ikaros frequently (50%) incurring multiple independent hits (including deletions and mutations) or suffering a single hit predicted to result in a dominant negative protein (such as those lacking exon 4, an isoform we have designated Ik12, which lacks two DNA binding zinc-finger domains). Conversely, Pten mutations were more frequent after early irradiation (60%) than after young adult-irradiation (30%). Homozygous Pten mutations occurred without DNA copy number change after irradiation starting in infancy, suggesting duplication of the mutated allele by chromosome mis-segregation or mitotic recombination. Our findings demonstrate that while deletions on chromosomes 4 and 11 affecting Cdkn2a and Ikaros are a prominent feature of young adult irradiation-induced T-cell lymphoma, tumors arising after irradiation from infancy suffer a second hit in Pten by mis-segregation or recombination. This is the first report showing an influence of age-at-exposure on genomic alterations of tumor suppressor genes and their relative involvement in radiation-induced T-cell lymphoma. These data are important for considering the risks associated with childhood exposure to radiation.
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Affiliation(s)
- Masaaki Sunaoshi
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan; Department of Biological Sciences, College of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
| | - Yoshiko Amasaki
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Shinobu Hirano-Sakairi
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Benjamin J Blyth
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Takamitsu Morioka
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan; Radiation Effect Accumulation and Prevention Project, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Mutsumi Kaminishi
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Yi Shang
- Radiation Effect Accumulation and Prevention Project, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Mayumi Nishimura
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan; Radiation Effect Accumulation and Prevention Project, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Yoshiya Shimada
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan; Radiation Effect Accumulation and Prevention Project, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Akira Tachibana
- Department of Biological Sciences, College of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
| | - Shizuko Kakinuma
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan; Radiation Effect Accumulation and Prevention Project, Fukushima Project Headquarters, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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3
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Hirano S, Kakinuma S, Amasaki Y, Nishimura M, Imaoka T, Fujimoto S, Hino O, Shimada Y. Ikaros is a critical target during simultaneous exposure to X-rays and N-ethyl-N-nitrosourea in mouse T-cell lymphomagenesis. Int J Cancer 2013; 132:259-68. [PMID: 22684892 DOI: 10.1002/ijc.27668] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 05/21/2012] [Indexed: 11/09/2022]
Abstract
Cancer risk associated with radiation exposure is considered the result of concurrent exposure to other natural and manmade carcinogens. Available data on the molecular characteristics of cancer after simultaneous exposure to radiation and chemicals are insufficient. In our study, we used a mouse thymic lymphoma (TL) model that was synergistically induced by simultaneous exposure to X-rays and N-ethyl-N-nitrosourea (ENU) at subcarcinogenic doses and analyzed the mutation frequency and spectrum of the TL-associated genes Ikaros, Notch1, p53 and Kras. We found that the point mutation frequency in Ikaros was significantly increased to 47% for simultaneous exposure compared to 13 and 0% for X-ray and ENU exposure alone, respectively. These mutations were mostly G:C > A:T at non-CpG sites and T:A > C:G, both of which are characteristic of ENU mutagenesis. About half of the point mutations were accompanied by loss of heterozygosity (LOH), typical of X-irradiation. The remaining half did not include LOH, which suggests that they were dominant-negative mutations. In Notch1, the frequency of abnormalities was high (>58%) regardless of the treatment, suggesting that Notch1 aberration may be important for T-cell lymphomagenesis. The p53 and Kras mutation frequencies were low for all treatments (<23%). Importantly, the frequency of TLs containing mutations in multiple genes, especially both Ikaros and Notch1, increased after simultaneous exposure. Thus, after simultaneous exposure, Ikaros is a critical target and is inactivated by ENU-induced point mutations and/or X-ray-induced LOH in T-cell lymphomagenesis. Furthermore, concomitant alterations of multiple tumor-associated genes may contribute to enhanced lymphomagenesis after simultaneous exposure.
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Affiliation(s)
- Shinobu Hirano
- Radiobiology for Children's Health Program, Research Center for Radiation Protection, National Institute of Radiological Sciences, Inage-Ku, Chiba, Japan
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4
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Xi Y, Li YS, Tang HB. High mobility group A1 protein acts as a new target of Notch1 signaling and regulates cell proliferation in T leukemia cells. Mol Cell Biochem 2012; 374:173-80. [PMID: 23229232 DOI: 10.1007/s11010-012-1517-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 11/07/2012] [Indexed: 11/30/2022]
Abstract
Active mutations of Notch1 play pivotal roles during leukemogenesis, but the downstream targets and molecular mechanisms of activated Notch1 signaling have not yet been fully clarified. In this study, we detected the overexpression of the high mobility group A1 (HMGA1) and activation of Notch1 signaling in mouse thymic lymphomas. A direct regulation of Notch1 on HMGA1 transcription was demonstrated and two Notch1/RBPJ cobinding sites of T/CTCCCACA were found in HMGA1 promoter regions. It was the first time demonstrated that HMGA1 was the downstream target of Notch1 signaling. Moreover, knockdown of HMGA1 resulted in significantly impaired cell growth and decreased expressions of cyclin D and cyclin E in human T leukemia cells. The formation of complexes was also observed between HMGA1 and retinoblastoma (RB) protein indicating a mechanism of cell cycle regulation. These findings suggest that activated HMGA1 regulates cell proliferation through the Notch1 signaling pathway, which represents an important molecular pathway leading to leukemogenesis.
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Affiliation(s)
- Yang Xi
- Medical School, Ningbo University, Ningbo, 315211, China
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5
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Kim TS, Lee DH, Kim SK, Shin SY, Seo EJ, Lim DS. Mammalian sterile 20-like kinase 1 suppresses lymphoma development by promoting faithful chromosome segregation. Cancer Res 2012; 72:5386-95. [PMID: 22926556 DOI: 10.1158/0008-5472.can-11-3956] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The mammalian Hippo signaling pathway has been implicated in oncogenesis in the context of solid tumors such as hepatocellular carcinoma. Mammalian sterile 20-like kinase 1 (MST1), the core component of the Hippo signaling pathway, is highly expressed in hematopoietic cells. However, its possible impact on tumorigenesis in this setting is unknown. In this study, we provide evidence that Mst1 loss in the mouse enhances chemically and genetically induced lymphoma development by inducing chromosomal instability. Mst1 deficiency increased susceptibility to T-cell acute lymphoblastic leukemia induced by mutagen exposure. Notably, before transformation Mst1(-/-) normal thymocytes showed no changes in proliferation or apoptosis in vitro and in vivo, but they displayed elevated levels of abnormal mitotic chromosomes and aneuploidy, conditions known to promote tumorigenesis. Mst1(-/-) mice also showed accelerated formation of spontaneous lymphomas in a p53-deficient background, accompanied by severe aneuploidy. In clinical specimens of lymphoma and leukemia, we documented frequent downregulation of MST1 expression, consistent with our findings. Taken together, our findings reveal a tumor suppressive function of Mst1 based on its ability to prevent chromosomal instability in lymphocytes.
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Affiliation(s)
- Tae-Shin Kim
- Authors' Affiliations: Department of Biological Sciences, National Creative Research Initiatives Center, Graduate School of Nanoscience and Technology (WCU), Korea Advanced Institute of Science and Technology, Daejeon, Korea
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6
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Kakinuma S, Nishimura M, Amasaki Y, Takada M, Yamauchi K, Sudo S, Shang Y, Doi K, Yoshinaga S, Shimada Y. Combined exposure to X-irradiation followed by N-ethyl-N-nitrosourea treatment alters the frequency and spectrum of Ikaros point mutations in murine T-cell lymphoma. Mutat Res 2012; 737:43-50. [PMID: 22706209 DOI: 10.1016/j.mrfmmm.2012.06.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 06/04/2012] [Accepted: 06/06/2012] [Indexed: 02/04/2023]
Abstract
Ionizing radiation is a well-known carcinogen, but its potency may be influenced by other environmental carcinogens, which is of practical importance in the assessment of risk. Data are scarce, however, on the combined effect of radiation with other environmental carcinogens and the underlying mechanisms involved. We studied the mode and mechanism of the carcinogenic effect of radiation in combination with N-ethyl-N-nitrosourea (ENU) using doses approximately equal to the corresponding thresholds. B6C3F1 mice exposed to fractionated X-irradiation (Kaplan's method) followed by ENU developed T-cell lymphomas in a dose-dependent manner. Radiation doses above an apparent threshold acted synergistically with ENU to promote lymphoma development, whereas radiation doses below that threshold antagonized lymphoma development. Ikaros, which regulates the commitment and differentiation of lymphoid lineage cells, is a critical tumor suppressor gene frequently altered in both human and mouse lymphomas and shows distinct mutation spectra between X-ray- and ENU-induced lymphomas. In the synergistically induced lymphomas, we observed a low frequency of LOH and an inordinate increase of Ikaros base substitutions characteristic of ENU-induced point mutations, G:C to A:T at non-CpG, A:T to G:C, G:C to T:A and A:T to T:A. This suggests that radiation doses above an apparent threshold activate the ENU mutagenic pathway. This is the first report on the carcinogenic mechanism elicited by combined exposure to carcinogens below and above threshold doses based on the mutation spectrum of the causative gene. These findings constitute a basis for assessing human cancer risk following exposure to multiple carcinogens.
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7
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Gao M, Li Y, Sun Y, Long J, Kong Y, Yang S, Wang Y. A common carcinogen benzo[a]pyrene causes p53 overexpression in mouse cervix via DNA damage. Mutat Res 2011; 724:69-75. [PMID: 21745588 DOI: 10.1016/j.mrgentox.2011.06.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 05/05/2011] [Accepted: 06/26/2011] [Indexed: 12/13/2022]
Abstract
Benzo[a]pyrene (BaP) is cytotoxic and/or genotoxic to lung, stomach and skin tissue in the body. However, the effect of BaP on cervical tissue remains unclear. The present study detected DNA damage and the expression of the p53 gene in BaP-induced cervical tissue in female mice. Animals were intraperitoneally injected and orally gavaged with BaP at the doses of 2.5, 5, and 10mg/kg twice a week for 14 weeks. The single-cell gel electrophoresis (SCGE) assay was used to detect the DNA damage. Immunohistochemistry (IHC) and in situ hybridization (ISH) were used to detect the expression of p53 protein and p53 mRNA, respectively. The results showed that BaP induced a significant and dose-dependent increase of the number of cells with DNA damaged and the tail length as well as Comet tail moment in cervical tissue. The expression level of p53 protein and mRNA was increased. The results demonstrate that BaP may show toxic effect on the cervix by increasing DNA damage and the expression of the p53 gene.
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Affiliation(s)
- Meili Gao
- Institute of Cancer Research, Department of Biological Science and Engineering, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Xi'an Jiaotong University School of Life Science and Technology, Xi'an, Shaanxi 710049, China.
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8
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Kastner P, Chan S. Role of Ikaros in T-cell acute lymphoblastic leukemia. World J Biol Chem 2011; 2:108-14. [PMID: 21765975 PMCID: PMC3135856 DOI: 10.4331/wjbc.v2.i6.108] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Revised: 04/27/2011] [Accepted: 06/03/2011] [Indexed: 02/05/2023] Open
Abstract
Ikaros is a zinc finger transcriptional regulator encoded by the Ikzf1 gene. Ikaros displays crucial functions in the hematopoietic system and its loss of function has been linked to the development of lymphoid leukemia. In particular, Ikaros has been found in recent years to be a major tumor suppressor involved in human B-cell acute lymphoblastic leukemia. Its role in T-cell leukemia, however, has been more controversial. While Ikaros deficiency appears to be very frequent in murine T-cell leukemias, loss of Ikaros appears to be rare in human T-cell acute lymphoblastic leukemia (T-ALL). We review here the evidence linking Ikaros to T-ALL in mouse and human systems.
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Affiliation(s)
- Philippe Kastner
- Philippe Kastner, Susan Chan, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch 67400, France
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9
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Smith APL, Polley S, Wells S, Stewart M, Vizor L, Humphreys J, Warren MV, Dear N, Cheeseman MT. Analysis of breeding and pathology helps refine management practices of a large-scale N'-ethyl-N'-nitrosourea mouse mutagenesis programme. Lab Anim 2008; 43:1-10. [PMID: 18987059 DOI: 10.1258/la.2008.007072] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
N'-ethyl-N'-nitrosourea (ENU) is a powerful germline mutagen used in conjunction with phenotype-driven screens to generate novel mouse mutants. ENU also induces genetic lesions in somatic cells and dosage requires optimization between maximum germline mutation rate versus induced sterility and tumourigenesis that compromise the welfare and fecundity of the ENU-treated males. Here, we present our experience with BALB/cAnNCrl and C57BL/6J mice in terms of the pathology induced by ENU and its impact on breeding. In both mouse strains, morbidity and mortality rises with ENU dose. In more than 75% of C57BL/6J males, morbidity and mortality were attributable to the development of malignant T-lymphoblastic lymphoma. Approximately 50% of ENU-treated BALB/cAnNCrl males develop early malignant T-lymphoblastic lymphoma, but the cohort that survives develops late-onset lung carcinoma. Within strains, the latency of these clinically important tumour(s) was not dosage-dependent, but the proportion of mice developing tumours and consequently removed from the breeding programme increased with ENU dosage. The median number of offspring per ENU-treated C57BL/6J male in standard matings with C3H/HeH females decreased with increasing dosage. The two most important underlying causes for lower male fecundity were increased infertility in the highest dosage group and reduced numbers of litters born to the remaining fertile C57BL/6J males due to a higher incidence of morbidity. These findings have allowed us to refine breeding strategy. To maximize the number of offspring from each ENU-treated male, we now rotate productive males between two cages to expose them to more females. This optimizes the number of mutation carrying offspring while reducing the number of ENU-treated males that must be generated.
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Affiliation(s)
- A P L Smith
- Mary Lyon Centre, Medical Research Council, Harwell, Oxfordshire OX11 0RD, UK
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10
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Yamauchi K, Kakinuma S, Sudo S, Kito S, Ohta Y, Nohmi T, Masumura KI, Nishimura M, Shimada Y. Differential effects of low- and high-dose X-rays on N-ethyl-N-nitrosourea-induced mutagenesis in thymocytes of B6C3F1 gpt-delta mice. Mutat Res 2008; 640:27-37. [PMID: 18242641 DOI: 10.1016/j.mrfmmm.2007.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Revised: 11/30/2007] [Accepted: 12/06/2007] [Indexed: 05/25/2023]
Abstract
Carcinogenesis in humans is thought to result from exposure to numerous environmental factors. Little is known, however, about how these different factors work in combination to cause cancer. Because thymic lymphoma is a good model of research for combined exposure, we examined the occurrence of mutations in thymic DNA following exposure of B6C3F1 gpt-delta mice to both ionizing radiation and N-ethyl-N-nitrosourea (ENU). Mice were exposed weekly to whole body X-irradiation (0.2 or 1.0 Gy), ENU (200 ppm) in the drinking water, or X-irradiation followed by ENU treatment. Thereafter, genomic DNA was prepared from the thymus and the number and types of mutations in the reporter transgene gpt was determined. ENU exposure alone increased mutant frequency by 10-fold compared to untreated controls and over 80% of mutants had expanded clonally. X-irradiation alone, at either low or high dose, unexpectedly, reduced mutant frequency. Combined exposure to 0.2 Gy X-rays with ENU dramatically decreased mutant frequency, specifically G:C to A:T and A:T to T:A mutations, compared to ENU treatment alone. In contrast, 1.0 Gy X-rays enhanced mutant frequency by about 30-fold and appeared to accelerate clonal expansion of mutated cells. In conclusion, repeated irradiation with 0.2 Gy X-rays not only reduced background mutation levels, but also suppressed ENU-induced mutations and clonal expansion. In contrast, 1.0 Gy irradiation in combination with ENU accelerated clonal expansion of mutated cells. These results indicate that the mode of the combined mutagenic effect is dose dependent.
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Affiliation(s)
- Kazumi Yamauchi
- Experimental Radiobiology for Children's Health Research Group, Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555, Japan
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11
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Barbaric I, Wells S, Russ A, Dear TN. Spectrum of ENU-induced mutations in phenotype-driven and gene-driven screens in the mouse. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2007; 48:124-42. [PMID: 17295309 DOI: 10.1002/em.20286] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
N-ethyl-N-nitrosourea (ENU) mutagenesis in mice has become a standard tool for (i) increasing the pool of mutants in many areas of biology, (ii) identifying novel genes involved in physiological processes and disease, and (iii) in assisting in assigning functions to genes. ENU is assumed to cause random mutations throughout the mouse genome, but this presumption has never been analyzed. This is a crucial point, especially for large-scale mutagenesis, as a bias would reflect a constraint on identifying possible genetic targets. There is a significant body of published data now available from both phenotype-driven and gene-driven ENU mutagenesis screens in the mouse that can be used to reveal the effectiveness and limitations of an ENU mutagenesis approach. Analysis of the published data is presented in this paper. As expected for a randomly acting mutagen, ENU-induced mutations identified in phenotype-driven screens were in genes that had higher coding sequence length and higher exon number than the average for the mouse genome. Unexpectedly, the data showed that ENU-induced mutations were more likely to be found in genes that had a higher G + C content and neighboring base analysis revealed that the identified ENU mutations were more often directly flanked by G or C nucleotides. ENU mutations from phenotype-driven and gene-driven screens were dominantly A:T to T:A transversions or A:T to G:C transitions. Knowledge of the spectrum of mutations that ENU elicits will assist in positional cloning of ENU-induced mutations by allowing prioritization of candidate genes based on some of their inherent features.
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Affiliation(s)
- Ivana Barbaric
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
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Shimada Y, Nishimura M, Kakinuma S, Yamauchi K, Imaoka T, Amasaki Y, Shang Y, Kawaguchi I, Doi M. Combined Effect of Ionizing Radiation and Alkylating Agents on Cancer Induction. Genes Environ 2007. [DOI: 10.3123/jemsge.29.29] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Kakinuma S, Kodama Y, Amasaki Y, Yi S, Tokairin Y, Arai M, Nishimura M, Monobe M, Kojima S, Shimada Y. Ikaros is a mutational target for lymphomagenesis in Mlh1-deficient mice. Oncogene 2006; 26:2945-9. [PMID: 17086208 DOI: 10.1038/sj.onc.1210100] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Deficiencies in DNA mismatch repair (MMR) result in replication errors within key tumor suppressor genes or oncogenes, and cause hereditary nonpolyposis colorectal cancer (HNPCC). Hematological malignancy with microsatellite instability is also associated with defective MMR, but little is known about the target genes for MMR. Here we identified Ikaros, a master transcription factor of lymphoid lineage commitment and differentiation, as a mutational target in spontaneous and radiation-induced T-cell lymphomas in Mlh1-deficient mice. Three quarters of lymphomas lacked Ikaros protein expression, which resulted from a frameshift mutation that created a stop codon. Mononucleotide repeat sequences at 1029-1034(C)6 and 1567-1572(G)6 in Ikaros were mutational hot spots with a one-base deletion occurring with a frequency of 45 and 50%, respectively. Point mutations and splicing alterations were also observed. In total, 85% of the lymphomas showed aberrations in Ikaros. The characteristic of Mlh1-deficient lymphomas is harboring of multiple mutations simultaneously in the same tumor, displaying a combination of two frameshift mutations at different repeats, frameshift and point mutations, and/or deletion mutations. This is the first report of Ikaros mutations coupled with Mlh1 deficiency in lymphomagenesis.
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Affiliation(s)
- S Kakinuma
- Experimental Radiobiology for Children's Health Research Group, National Institute of Radiological Sciences, Chiba, Japan.
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Dumortier A, Jeannet R, Kirstetter P, Kleinmann E, Sellars M, dos Santos NR, Thibault C, Barths J, Ghysdael J, Punt JA, Kastner P, Chan S. Notch activation is an early and critical event during T-Cell leukemogenesis in Ikaros-deficient mice. Mol Cell Biol 2006; 26:209-20. [PMID: 16354692 PMCID: PMC1317628 DOI: 10.1128/mcb.26.1.209-220.2006] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Ikaros transcription factor is both a key regulator of lymphocyte differentiation and a tumor suppressor in T lymphocytes. Mice carrying a hypomorphic mutation (Ik(L/L)) in the Ikaros gene all develop thymic lymphomas. Ik(L/L) tumors always exhibit strong activation of the Notch pathway, which is required for tumor cell proliferation in vitro. Notch activation occurs early in tumorigenesis and may precede transformation, as ectopic expression of the Notch targets Hes-1 and Deltex-1 is detected in thymocytes from young Ik(L/L) mice with no overt signs of transformation. Notch activation is further amplified by secondary mutations that lead to C-terminal truncations of Notch 1. Strikingly, restoration of Ikaros activity in tumor cells leads to a rapid and specific downregulation of Notch target gene expression and proliferation arrest. Furthermore, Ikaros binds to the Notch-responsive element in the Hes-1 promoter and represses Notch-dependent transcription from this promoter. Thus, Ikaros-mediated repression of Notch target gene expression may play a critical role in defining the tumor suppressor function of this factor.
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Affiliation(s)
- Alexis Dumortier
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS-INSERM-ULP, BP 10142, 67404 Illkirch, CU Strasbourg, France
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