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- Zhuang, Shi-Mei, 1965-, et al.
(författare)
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Frequent mutations of the Trp53,Hras1 and beta-catenin (Catnb) genes in 1,3-butadiene-induced mammary adenocarcinomas in B6C3F1 mice
- 2002
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Ingår i: Oncogene. - : Springer Science and Business Media LLC. - 0950-9232 .- 1476-5594. ; 21:36, s. 5643-5648
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Tidskriftsartikel (refereegranskat)abstract
- DNAs from 1,3-butadiene-induced mammary adenocarcinomas of B6C3F1 mice were examined for mutations in the Trp53 gene, the ras gene family and several components of the Wnt signaling pathway, including ▀-catenin (Catnb), Apc and Axin. Trp53 mutations were detected in 41% (7 out of 17) of tumors. Each tumor with a Trp53 mutation also exhibited loss of the wildtype Trp53 allele, supporting the importance of Trp53 inactivation during development of these tumors. Analyses of the Hras1, Kras2 and Aras proto-oncogenes revealed Hras1 mutations in 53% (9 out of 17) of tumors. Seven of these mutations were a G?C transversion in Hras1 codon 13, consistent with a 1,3-butadiene-specific Kras2 mutation previously reported in several other tumor types. Mutation screens in Catnb exon 2, the Apc mutation cluster region and the Catnb-binding domain of the Axin gene identified Catnb missense mutations in 3 out of 17 (18%) tumors. In total, mutations of the Trp53, Hras1 and/or Catnb genes were identified in 15 out of 17 1,3-butadiene-induced mammary adenocarcinomas. These results indicate that multiple genetic pathways are disrupted in chemically induced mammary tumors, and that studies in mouse models may help to understand the etiology of human breast cancers.
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| 2. |
- Zhuang, Shi-Mei, 1965-
(författare)
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Molecular genetic alterations in chemically-induced lymphomas
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lymphoma is one of the most common malignancies in humans. Its incidence has increased rapidly in the past 30 years. However, the molecular mechanisms underlying the development of lymphomas are largely unknown.Environmental carcinogens play an important role in tumorigenesis. 1,3-butadiene (BD) and 2~,3-dideoxycytidine (ddC) are two carcinogens to which humans are exposed. Cancer bioassays in mice have revealed that both BD and ddC induce high frequencies of lymphomas. The present study provides a genetic dissection of these chemically-induced lymphomas, with a focus on identification of potential turner suppressor loci and genetic alterations in genes involved in the pRb, p53 and Ras/Raf pathways. These pathways are important in the control of cell proliferation.Approximately 87% of BD-induced and 75% of ddC-induced lymphomas show allelic losses or mutations in genes examined. Similar frequencies for inactivation of the p53 pathway were observed in BD- and ddC-induced tumors, whereas disruption of the pRb pathway is more common in ddC-induced lymphomas. On the other hand, BD-induced tumors display more frequent activation of the Ras/Raf pathway. These data indicate the genotoxicity of both ddC and BD, and also confirm the carcinogenicity of these chemicals at a molecular level.This study also reveals that different genetic alterations occur in distinct stages of the development of BD-induced lymphomas. Ras mutations were detected in tumors derived from mice exposed to BD for only 26 weeks or at a rather low concentration (20 ppm), suggesting that ras mutations may occur early in tumor formation. In contrast, all six tumors with aberrations of p53 occurred in the high dose (625 ppm), continuous long-term exposure group, and these tumors appear to have a more aggressive phenotype, indicating that inactivation of p53 may be a late event, associated with progression of BD-induced lymphomas. Furthermore, two or more genetic alterations were found in 67% of tumors from the 625 ppm dose group and in only 46% of lymphomas derived from mice exposed to s312 ppm of BD. In addition, more than five genetic aberrations occurred only in the 625 ppm dose group. These results support the contention that there is a dose-dependent increase of genetic alterations in BD-induced tumors.The mutational pattern resulting from carcinogen-exposure has been observed in both human and animal turners. In the present study, the specific K-ras codon 13 CGC mutation and allelic loss of the Rafl locus on chromosome 6 were detected only in BD-induced lymphomas, while frequent allelic loss of the telomeric region of chromosome 2 was observed only in ddC-induced tumors, suggesting an agent-specific effect.The genome-wide screen of allelic losses revealed that multiple potential tumor suppressor genes contribute to the development of BD- and ddC-induced lymphomas. Moreover, most of the identified regions with frequent allelic losses carry unknown tumor suppressor genes, whose isolation and identification are of great interest for further investigation.
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| 3. |
- Zhuang, Shi-Mei, 1965-, et al.
(författare)
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Mutation analysis of the pRb pathway in 2',3'-dideoxycytidine- and 1,3-butadiene-induced mouse lymphomas
- 2000
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Ingår i: Cancer Letters. - 0304-3835 .- 1872-7980. ; 152:2, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- The pRb pathway plays a key role in controlling the G1/S transition in cell cycle progression. Aberrations of various components of the pRb pathway, such as retinoblastoma protein and its upstream actors including cyclin D1, cyclin dependence kinase-4 and p16/p15 cyclin dependent kinase inhibitors, have been reported in a variety of human tumors. Furthermore, the alterations of retinoblastoma protein and its upstream components often occur in a reciprocal manner. Previously, we have reported frequent inactivation of the Cdkn2a/Cdkn2b loci encoding p16/p15 cyclin dependent kinase inhibitors in a subset of 2',3'-dideoxycytidine- and 1,3-butadiene-induced mouse lymphomas (S.-M. Zhuang, A. Schippert, A. Haugen-Strano, R.W. Wiseman, P. Soderkvist, Inactivation of p16(INK4a)-a, p16(INK4a)-▀ and p15(INK4b) genes in 2',3'-dideoxycytidine- and 1,3-butadiene-induced lymphomas, Oncogene 16 (1998) 803-808), indicating the involvement of pRb pathway in lymphomagenesis. To investigate whether alteration of other components in pRb pathway is an alternative mechanism underlying the development of these chemically induced lymphomas, we have examined the genetic status of Rb1, Ccnd1 and Cdk4 genes that encode retinoblastoma protein, cyclin D1 and cyclin dependence kinase-4, respectively. Gross alterations of the Rb1, Ccnd1, and Cdk4 genes were not detected by Southern analysis in any of the tumors examined. In addition, single-strand conformation analysis failed to reveal point mutations in the Cdk4 amino terminal domain that is important for its association with Cdkn2a gene products. These results indicate that the mechanisms underlying the development of 2',3'-dideoxycytidine- and 1,3-butadiene-induced lymphomas involve inactivation of p16/p15 cyclin-dependent kinase inhibitors but not genomic alterations of the Rb1, Ccnd1 and Cdk4 genes. Copyright (C) 2000 Elsevier Science Ireland Ltd.
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