1
|
Thorne D, Leverette R, Breheny D, Lloyd M, McEnaney S, Whitwell J, Clements J, Bombick B, Gaca M. Genotoxicity evaluation of tobacco and nicotine delivery products: Part One. Mouse lymphoma assay. Food Chem Toxicol 2019; 132:110584. [PMID: 31228600 DOI: 10.1016/j.fct.2019.110584] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 05/06/2019] [Accepted: 06/13/2019] [Indexed: 10/26/2022]
Abstract
Conduct of the mouse lymphoma assay (MLA) is underpinned by Organisation for Economic Co-operation and Development (OECD) Test Guideline 490 and International Conference on Harmonisation S2(R1) guidance and is a recognised in vitro genotoxicity test battery assay. It has been used on a limited number of occasions for the assessment of some tobacco and nicotine products, such as e-cigarettes and tobacco heating products (THP). The aim of this study was to assess the suitability of the MLA for genotoxicity testing with a variety of tobacco and nicotine products. Total particulate matter (TPM) from a 3R4F cigarette was compared against a commercial electronic cigarette liquid (e-liquid), electronic cigarette (e-cigarette) aerosol matter captured from the same e-liquid, and TPM from a commercial THP. Treatment conditions included 3 h exposures with and without metabolic activation and a longer 24 h exposure without metabolic activation (-S9) at concentrations up to 500 μg/mL. Under all treatment conditions, 3R4F produced a clear positive response with regard to induction of mutation. In contrast, no marked induction of mutation was observed for the e-liquid, e-cigarette aerosol or THP. Additionally, data are presented as a function of nicotine equivalents for comparisons between these different tobacco products and test matrices.
Collapse
Affiliation(s)
- David Thorne
- British American Tobacco, R&D, Southampton, Hampshire, SO15 8TL, UK.
| | - Robert Leverette
- RAI Services Company, 401 N. Main Street, Winston-Salem, NC, 27101, USA
| | - Damien Breheny
- British American Tobacco, R&D, Southampton, Hampshire, SO15 8TL, UK
| | - Mel Lloyd
- Covance Laboratories Ltd., Otley Road, Harrogate, North Yorkshire, HG3 1PY, UK
| | - Stephen McEnaney
- Covance Laboratories Ltd., Otley Road, Harrogate, North Yorkshire, HG3 1PY, UK
| | - James Whitwell
- Covance Laboratories Ltd., Otley Road, Harrogate, North Yorkshire, HG3 1PY, UK
| | - Julie Clements
- Covance Laboratories Ltd., Otley Road, Harrogate, North Yorkshire, HG3 1PY, UK
| | - Betsy Bombick
- RAI Services Company, 401 N. Main Street, Winston-Salem, NC, 27101, USA
| | - Marianna Gaca
- British American Tobacco, R&D, Southampton, Hampshire, SO15 8TL, UK
| |
Collapse
|
2
|
Guo X, Pan B, Seo JE, Chen Y, Yan J, Mei N, Chen T. Whole genome sequencing analysis of small and large colony mutants from the mouse lymphoma assay. Arch Toxicol 2018; 92:3585-3595. [DOI: 10.1007/s00204-018-2318-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 09/19/2018] [Indexed: 11/25/2022]
|
3
|
Wang J, Sawyer JR, Chen L, Chen T, Honma M, Mei N, Moore MM. The Mouse Lymphoma Assay Detects Recombination, Deletion, and Aneuploidy. Toxicol Sci 2009; 109:96-105. [DOI: 10.1093/toxsci/kfp037] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
|
4
|
Wang J, Chen T, Honma M, Chen L, Moore MM. 3'-azido-3'-deoxythymidine induces deletions in L5178Y mouse lymphoma cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2007; 48:248-57. [PMID: 17358034 DOI: 10.1002/em.20263] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
3'-Azido-3'-deoxythymidine (AZT), a nucleoside analogue used for the treatment of acquired immunodeficiency syndrome (AIDS), induced a significant dose-related increase in the thymidine kinase (Tk) mutant frequency (MF) in L5178Y/Tk(+/-) 3.7.2C mouse lymphoma cells. Treatment with 1 mg/ml (3,742 muM) AZT for 24 hr resulted in a MF of 407 x 10(-6) compared to a control MF of 84 x 10(-6). The MFs of the large and small colony mutants resulting from AZT exposure were 142 x 10(-6) and 265 x 10(-6), respectively. One hundred and fifty mutants from the 1 mg/ml (3,742 muM) AZT-treated culture and sixty-nine mutants from independent untreated cultures were isolated and analyzed. LOH analysis using a heteromorphic microsatellite locus located in the Tk gene was performed to determine the presence or absence of the Tk(+) allele. Eight other microsatellite markers spanning the entire mouse chromosome 11 also were examined for heterozygosity to determine the extent of LOH. In addition, Tk gene dosage analysis was conducted using Real-Time PCR in those mutants showing LOH at the Tk locus. The presence of only one Tk allele based on Real-Time PCR indicated that the mutant resulted from deletion while the presence of two alleles was consistent with a recombination event. More mutants from the AZT-treated culture showed Tk LOH than did independent mutants from the untreated cultures (91% vs. 64%) and the induced mutants also showed distinct chromosome 11 LOH patterns. The mutation spectrum of mutants from AZT-treated cells was also significantly different from that of spontaneous mutants. More deletions and fewer intragenic mutations were observed in the mutants from the AZT-treated culture than independent mutants from the untreated control. Our data indicate that AZT primarily induced LOH mutations in L5178Y mouse lymphoma cells and a large number of LOH mutations resulted from deletions.
Collapse
Affiliation(s)
- Jianyong Wang
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
| | | | | | | | | |
Collapse
|
5
|
Mortelmans K, Rupa DS. Current Issues in Genetic Toxicology Testing for Microbiologists. ADVANCES IN APPLIED MICROBIOLOGY 2004; 56:379-401. [PMID: 15566986 DOI: 10.1016/s0065-2164(04)56012-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Kristien Mortelmans
- Toxicology and Pharmacology Laboratory Biosciences Division, SRI International Menlo Park, California 94025, USA.
| | | |
Collapse
|
6
|
Chen T, Harrington-Brock K, Moore MM. Mutant frequency and mutational spectra in the Tk and Hprt genes of N-ethyl-N-nitrosourea-treated mouse lymphoma cellsdagger. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2002; 39:296-305. [PMID: 12112381 DOI: 10.1002/em.10075] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The mouse lymphoma assay (MLA) utilizing the Tk gene is widely used to identify chemical mutagens. The autosomal location of the Tk gene allows for the detection of a wide range of mutational events, from point mutations to chromosome alterations. However, chemically induced point mutation spectra in the Tk gene of mouse lymphoma cells have not been characterized. In this study, we determined and compared the mutagenicity and mutational spectra of N-ethyl-N-nitrosourea (ENU) in the Tk and Hprt genes of mouse lymphoma cells. Treatment of L5178Y mouse lymphoma cells with 100 microg/ml ENU induced a Tk mutant frequency of 756 x 10(-6) and an Hprt mutant frequency of 311 x 10(-6). Sequence analysis of Tk and Hprt mutant cDNAs showed a similar overall mutation pattern in the two genes with base-pair substitutions accounting for 83% of non-loss of heterozygosity mutations in the Tk gene and 75% of all mutations in the Hprt gene. The most common point mutation induced by ENU was G:C --> A:T transition (36 and 28% of independent mutations detected in the Tk and Hprt genes, respectively). The mutation spectra induced by ENU in both the Tk and Hprt genes were different from the respective patterns produced in mutants from untreated cells. About 9% of Tk and 7% of Hprt mutations from control cells were in-frame deletions, whereas no such mutations were found among the ENU-induced Tk and Hprt mutations. Our results indicate that ENU produces a chemical-specific point mutational profile in the Tk gene of mouse lymphoma cells that is remarkably similar to that found in the X-linked Hprt gene. This study provides evidence that the MLA can be used not only to detect point mutagens but also for analysis of mutational spectra.
Collapse
Affiliation(s)
- Tao Chen
- Division of Genetic and Reproductive Toxicology, FDA/National Center for Toxicological Research, Jefferson, Arkansas 72079, USA.
| | | | | |
Collapse
|
7
|
Honma M, Momose M, Sakamoto H, Sofuni T, Hayashi M. Spindle poisons induce allelic loss in mouse lymphoma cells through mitotic non-disjunction. Mutat Res 2001; 493:101-14. [PMID: 11516720 DOI: 10.1016/s1383-5718(01)00167-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Aneuploidy is an important contributor to reproductive failure and tumor development. It arises spontaneously or as a result of exposure to aneugenic agents through non-disjunction. Two spindle poisons, colchicine (COL) and vinblastine (VBL) are mutagenic in the mouse lymphoma assay (MLA), a gene mutation assay that targets the heterozygous thymidine kinase (tk) gene on chromosome 11 in mouse lymphoma L5178Y tk+/- 3.7.2c cells. To investigate the mechanisms of spindle poison mutagenesis, we analyzed the COL- and VBL-induced TK mutants at the molecular and cytogenetic level. Loss of heterozygosity (LOH) analysis employing a microsatellite region within the tk locus revealed that almost all mutants had lost the functional tk allele. To determine the extent of the LOH, we further examined LOH mutants for heterozygosity at nine microsatellite loci spanning the entire chromosome 11. Interestingly, every microsatellite marker showed LOH in all COL- and VBL-induced LOH mutants, suggesting that these mutants were generated by loss of the whole chromosome 11 through mitotic non-disjunction. Chromosome painting analysis supported this hypothesis; there were no mutants showing structural changes such as deletions or translocations involving chromosome 11. In contrast, spontaneous TK mutants followed from point mutations, deletions and recombinational events as well as whole chromosome loss. Our present study indicates that spindle poisons induce mutations through mitotic non-disjunction without structural DNA changes and supports a possible mechanism in which a recessive mutation mediated by aneuploidy may develop tumors.
Collapse
Affiliation(s)
- M Honma
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.
| | | | | | | | | |
Collapse
|
8
|
Abstract
In this paper, the current status of the protocol for the Mouse Lymphoma Assay is discussed. A brief history describes the events leading to current protocol recommendations. Areas for further development such as cytotoxicity, 24-h treatments, acceptability criteria and statistical analysis are also considered. Recent guidelines are reviewed, and consensus issues from the Mouse Lymphoma workgroup assembled as part of the International Workshop on Genotoxicity Test Procedures (IWGTP) are included. There are two versions of the assay - soft agar and microwell - and both will be discussed. For assay procedures, the emphasis will be on a typical microwell protocol but an attempt will be made to highlight protocol variations between laboratories and between the microwell and agar versions of the assay.
Collapse
Affiliation(s)
- J Clements
- Covance Laboratories Limited, Otley Road, North Yorkshire, HG3 1PY, Harrogate, UK.
| |
Collapse
|
9
|
Caspary WJ, Stopper H, Hozier JC, Liechty MC, Davis LM. Mechanisms leading to the expression of recessive alleles: the use of polymorphic microsatellites and whole-chromosome painting probes to analyze mouse tumors, mutants, and micronuclei. Recent Results Cancer Res 1997; 143:161-182. [PMID: 8912418 DOI: 10.1007/978-3-642-60393-8_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- W J Caspary
- Laboratory of Environmental Carcinogenesis and Mutagenesis, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | | | | | | | | |
Collapse
|
10
|
Liechty MC, Crosby H, Murthy A, Davis LM, Caspary WJ, Hozier JC. Identification of a heteromorphic microsatellite within the thymidine kinase gene in L5178Y mouse lymphoma cells. Mutat Res 1996; 371:265-71. [PMID: 9008728 DOI: 10.1016/s0165-1218(96)90115-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The objective of this work is to identify a heteromorphism within the thymidine kinase (Tk1) gene which can be used to assay for allele loss by means of PCR. Intron F of mouse Tk1 contains two (CA)n microsatellite sequences separated by 107 bp of non-repetitive sequence. We tested this region for heteromorphism in L5178Y mouse lymphoma cells. A PCR primer pair designated Agl1 yielded products of 396 and 194 bp from L5178Y tk+/- genomic DNA. The 194-bp product resulted from a secondary binding site between the two (CA)n repeats for the forward Ag11 primer and was not produced from tk-/- mutants that had lost the functional Tk1b allele. Agl2 primers produced two PCR products of 523 and approximately 440 bp and Agl3 primers produced products of 579 and approximately 500 bp. In both these cases, the difference in product size was approximately equal, indicating that Intron F is approximately 80 bp shorter in the non-functional Tk1a allele than in Tk1b. This heteromorphism forms the basis for an assay for allele loss by means of PCR. Agl1 and Agl3 primers yielded additional products of 91 and 274 bp, respectively, consistent with sizes expected from the mouse Tk1 pseudogenes (Tk1-ps). Our conclusions drawn from an analysis of 122 mutants for Tk1b loss using Agl2 primers agreed with previous analysis of the NcoI heteromorphism. Thus, a simple PCR-based analysis can identify Tk1b loss in the L5178Y mouse lymphoma cells.
Collapse
Affiliation(s)
- M C Liechty
- Applied Genetics Laboratories, Inc., Melbourne, FL 32901, USA
| | | | | | | | | | | |
Collapse
|
11
|
McGregor D, Riach C, Cattanach P, Edwards I, Shepherd W, Caspary W. Mutagenic responses of L5178Y mouse cells at the tk and hprt loci. Toxicol In Vitro 1996; 10:643-7. [DOI: 10.1016/s0887-2333(96)90030-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/1996] [Indexed: 11/15/2022]
|
12
|
Zhang LS, Honma M, Matsuoka A, Suzuki T, Sofuni T, Hayashi M. Chromosome painting analysis of spontaneous and methyl methanesulfonate-induced trifluorothymidine-resistant L5178Y cell colonies. Mutat Res 1996; 370:181-90. [PMID: 8917664 DOI: 10.1016/s0165-1218(96)00069-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Spontaneous and methyl methanesulfonate-induced trifluorothymidine-resistant mutants in mouse lymphoma L5178Y cells were analyzed using fluorescence in situ hybridization with mouse probes specific for chromosome 11, on which the tk gene is located, and chromosome 3, as the control. 76.5% (13/17) of small-colony mutants (thought to be the result of chromosomal mutation) and 28.6% (4/14) of large-colony mutants (thought to be the result of gene mutation) showed rearranged chromosome 11. Of the mutants with abnormal chromosome 11 painting pattern, 5 small- and 2 large-colony mutants carried clonal aberrations, while the remaining 8 small- and 2 large-colony mutants showed mosaic aberrations. Most abnormalities in the small-colony mutants involved the distal region of one painted chromosome 11, where the tk+ gene maps. An increase, rather than a decrease, in chromosome 11 material was found in a majority of abnormally painted mutants. On the contrary, no rearrangements involving chromosome 3 were found in any small- and large-colony mutants analyzed except one large-colony mutant, which showed chromosome rearrangements involving both chromosome 11 and 3. The present study confirms that the majority of small-colony mutants in L5178Y cells have chromosome 11 rearrangements that can be detected by chromosome painting and that the majority of the chromosomal abnormalities in TFT-resistant mutants involved complex rearrangements.
Collapse
Affiliation(s)
- L S Zhang
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tokyo, Japan
| | | | | | | | | | | |
Collapse
|
13
|
Spencer DL, Caspary WJ. In situ and suspension protocols for chemically-induced mutation at the tk locus in L5178Y MOLY cells: dose response and colony size distribution. Mutat Res 1994; 322:291-300. [PMID: 7523923 DOI: 10.1016/0165-1218(94)90105-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We used EMS up to concentrations of 0.25 microliters/ml (292 micrograms/ml) to induce mutations at the tk locus in L5178Y MOLY cells, measured the cellular response by the in situ mutation assay protocol and compared these results to those obtained in a concomitant suspension assay. EMS induced mutagenic responses with both protocols. The mutant fraction for the solvent control was 89 mutants per million viable colonies for the suspension protocol and 426 mutations per million viable cells plated for the in situ protocol. These numbers increase to 447 and 2073 respectively, with 0.25 microliter/ml EMS treatment. Sizing curves indicated that the in situ protocol detected a greater proportion of smaller colonies than did the suspension protocol. Not only were the number of small colonies greater than large colonies in the in situ protocol, but their rate of increase was also slightly higher than that of the large colonies. The in situ protocol also reduces the time and cost of experimentally performing the assay compared to the suspension protocol. In this paper we compare the use of the suspension and in situ protocols to measure chemically-induced mutations and demonstrate that the latter method detects a larger fraction of induced mutations at the tk locus in L5178Y MOLY cells.
Collapse
Affiliation(s)
- D L Spencer
- Laboratory of Environmental Carcinogenesis and Mutagenesis, National Institutes of Health, Research Triangle Park, NC 27709
| | | |
Collapse
|
14
|
Spencer DL, Hines KC, Caspary WJ. An in situ protocol for measuring the expression of chemically-induced mutations in mammalian cells. Mutat Res 1994; 312:85-97. [PMID: 7510835 DOI: 10.1016/0165-1161(94)90013-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The generation of expression curves and the evaluation of mutagenic responses of mammalian cells using standard mutagenesis assays can be inaccurate because mutant and wild-type cells are usually mixed during the expression phase. If some mutant progenitors or mutants grow more slowly than the wild-type cells during the expression period, there will be a decrease in the mutant to wild-type ratio with time and the mutant fraction will not accurately represent the number of mutational events that occurred. The mutant fraction may also inaccurately assess the number of mutations if these mutations are expressed over a number of generations during the time before selection. We previously showed that recovery of L5178Y mouse cell mutants is not complete when mutations are allowed to express in suspension because slowly growing mutants and/or mutant progenitors are diluted out during this time (Rudd et al., 1990). In order to more accurately quantitate the mutagenic response of the cells, we developed an in situ procedure which segregates and immobilizes cells during expression. Because of this immobilization, slowly growing mutant progenitors and mutants expressed at different times will have an equal probability of being scored as mutants. Thus, one mutation leads to one mutant colony and the measurement of the mutagenic response of the cells to the chemical accurately reflects the mutational events that occurred. We plated L5178Y tk+/- mouse cells in semisolid medium immediately after treatment. As the cells grew and formed microcolonies, the selective agent TFT was added as an overlay at specified times, permitting only TFTr cells to survive. In this procedure, each mutation was captured as an individual colony; consequently, the measured mutation fraction accurately reflected the mutational events that occurred at the selected locus. In addition, the induced mutant colonies arising in the agar are the result of independent mutational events. We previously described the in situ protocol for L5178Y cells and showed that the spontaneous mutation rate measured was 50-fold greater than when the cells expressed the phenotype in suspension (Rudd et al., 1990). From this we concluded that the slow growth phenotype was expressed before TFT resistance. In the present paper, we evaluate the effect of chemical treatment on the mutation fraction as a function of the time to TFT addition. Using the in situ protocol, we generated expression curves for three nucleotide analogs, 5-azacytidine, TFT and AraC. The numbers of TFTr colonies produced at various times after treatment indicated that chemically-treated cultures had higher mutation fractions than the solvent controls.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- D L Spencer
- Laboratory of Environmental Carcinogenesis and Mutagenesis, National Institutes of Health, Research Triangle Park, NC 27709
| | | | | |
Collapse
|
15
|
Oberly TJ, Huffman DM, Scheuring JC, Garriott ML. An evaluation of 6 chromosomal mutagens in the AS52/XPRT mutation assay utilizing suspension culture and soft agar cloning. Mutat Res 1993; 319:179-87. [PMID: 7694139 DOI: 10.1016/0165-1218(93)90077-q] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The AS52/XPRT mutation assay was examined for sensitivity in the detection of chromosomal mutagens. 6 compounds identified as chromosomal mutagens in the mouse lymphoma assay (MLA) were tested for mutagenicity in AS52 cells using suspension treatment and soft agar cloning. The 6 compounds were benzo[a]pyrene (BAP), 2-acetylaminofluorene (2AAF), methylmethanesulfonate (MMS), methyl acrylate (MCR), benzoin (BZ), and p-aminophenol (AM). BAP, 2AAF and MMS were mutagenic. The mutagenic responses for BAP, 2AAF and MMS included small colony mutants which have been shown to correlate with chromosomal mutation in the MLA. Colonies ranged from approximately 0.2 to 1.5 mm in size. The mutant frequency (MF) for the AS52 cells treated with BAP and 2AAF exceeded that previously reported for the MLA by 2-fold. In contrast, the MF for AS52 cells treated with MMS was one-third that reported in the MLA. The MF obtained in AS52 cells exceeded that reported for the CHO/HGPRT mutation assay for all 3 compounds. MCR, which produces almost entirely small colonies in the MLA, was negative in AS52 cells as were the MLA chromosomal mutagens AM and BZ. However, AM and BZ have only been reported mutagenic in the MLA. Both are considered nongenotoxic and noncarcinogenic. The results with the latter 3 compounds suggest that the AS52 assay is not as sensitive as the MLA for the detection of compounds identified as chromosomal mutagens.
Collapse
Affiliation(s)
- T J Oberly
- Toxicology Research Laboratories, Lilly Research Laboratories, Division of Eli Lilly and Company, Greenfield, IN 46140
| | | | | | | |
Collapse
|
16
|
Oberly TJ, Michaelis KC, Rexroat MA, Bewsey BJ, Garriott ML. A comparison of the CHO/HGPRT+ and the L5178Y/TK+/- mutation assays using suspension treatment and soft agar cloning: results for 10 chemicals. Cell Biol Toxicol 1993; 9:243-57. [PMID: 8299003 DOI: 10.1007/bf00755603] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The mouse lymphoma assay (MLA) and Chinese hamster ovary (CHO) cell assay are sensitive indicators of mutagenicity. The CHO assay has been modified technically to permit treatment in suspension and soft agar cloning comparable to the MLA. This methodology eliminates the risk of metabolic cooperation and the trauma of trypsinization. In addition, a larger population of cells can be treated and cloned for mutant selection. In order to compare the effectiveness of the test systems, 10 chemicals were evaluated for the induction of forward mutations in the CHO and MLA. Several of these chemicals have been reported as clastogenic; therefore, abbreviated colony sizing was performed to gauge the extent of genetic damage to the MLA cells. Both test systems detected benzo[a]pyrene, mitomycin C, acridine orange, and proflavin, and, with the exception of proflavin, more large colonies were present than small colonies. The suspect clastogen, phenytoin, was not mutagenic in the MLA and produced inconclusive results in the CHO. Ethidium bromide, a clastogen and a bacterial mutagen, was not mutagenic in either the MLA or CHO. Four compounds (p-aminophenol, benzoin, methoxychlor, and pyrene) were positive in the MLA, generally inducing a large number of small colonies, while demonstrating no mutagenic activity in the CHO assay. They have also been shown to be generally nongenotoxic in other test systems. Overall, the modified CHO assay did not appear to be better than the MLA for the detection of mutagenic agents. However, the MLA does appear to have lower specificity.
Collapse
Affiliation(s)
- T J Oberly
- Toxicology Research Laboratories, Lilly Research Laboratories, Greenfield, IN 46140
| | | | | | | | | |
Collapse
|
17
|
Stopper H, Pechan R, Schiffmann D. 5-azacytidine induces micronuclei in and morphological transformation of Syrian hamster embryo fibroblasts in the absence of unscheduled DNA synthesis. Mutat Res 1992; 283:21-8. [PMID: 1380659 DOI: 10.1016/0165-7992(92)90117-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
It is known that 5-azacytidine (5-AC) induces tumors in several organs of rats and mice. The mechanisms of these effects are still poorly understood although it is known that 5-AC can be incorporated into DNA. Furthermore, it can inhibit DNA methylation. The known data on its clastogenic and/or gene mutation-inducing potential are still controversial. Therefore, we have investigated the kinds of genotoxic effects caused by 5-AC in Syrian hamster embryo (SHE) fibroblasts. Three different endpoints (micronucleus formation, unscheduled DNA synthesis (UDS) and cell transformation) were assayed under similar conditions of metabolism and dose at target in this cell system. 5-AC induces morphological transformation of SHE cells, but not UDS. Therefore, 5-AC does not seem to cause repairable DNA lesions. Furthermore, our studies revealed that 5-AC is a potent inducer of micronuclei in the SHE system. Immunocytochemical analysis revealed that a certain percentage of these contain kinetochores indicating that 5-AC may induce both clastogenic events and numerical chromosome changes.
Collapse
Affiliation(s)
- H Stopper
- Institute of Pharmacology and Toxicology, University of Würzburg, Germany
| | | | | |
Collapse
|
18
|
Abstract
The phenotypic stability of over 2000 large- and small-colony trifluorothymidine-resistant (TFTres) variants of L5178Y/tk(+/-)-3.7.2C cells has been examined. All except 4 of 488 spontaneously arising small-colony variants analyzed (0.8%) retained the TFTres phenotype when rechallenged with TFT after growth for several generations in its absence. All of 558 spontaneous large-colony variants, and 440 small-colony or 487 large-colony variants arising from 13 different mutagens showed similar stability. These results attest to the completeness of TFT selection in the mouse-lymphoma assay when used at 1 microgram/ml in Fischer's medium supplemented with heat-inactivated serum and, together with previous cytogenetic and molecular studies, justify considering essentially all such TFTres variants as stable mutants. The implications of these results for those versions of the mouse lymphoma assay that fail to optimize the recovery and scoring of small-colony mutants is discussed.
Collapse
Affiliation(s)
- D Clive
- Burroughs Wellcome Co., Research Triangle Park, NC 27709
| | | |
Collapse
|
19
|
Clive D, Glover PL. Temperature sensitivity of small-colony TFTres variants of L5178Y mouse lymphoma cells may be due to fastidious growth requirements of macromutations. Mutat Res 1991; 260:401-5, 407. [PMID: 1714543 DOI: 10.1016/0165-1218(91)90026-i] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
20
|
Clive D, Glover P, Krehl R, Poorman-Allen P. Mutagenicity of 2-amino-N6-hydroxyadenine (AHA) at three loci in L5178Y/tk+/- mouse lymphoma cells: molecular and preliminary cytogenetic characterizations of AHA-induced tk-/- mutants. Mutat Res 1991; 253:73-82. [PMID: 1651447 DOI: 10.1016/0165-1161(91)90347-b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
2-Amino-N6-hydroxyadenine (AHA) is a remarkably efficient and specific inducer of point mutations in Neurospora, with few or no larger scale events being detected (de Serres et al., 1985). In the present studies, AHA is shown to be a potent point mutagen at the tk +/-, hprt+ and Na+/K+ ATPase loci in L5178Y/tk (+/-)-3.7.2C mouse lymphoma cells. Both large and small colony tk-/- mutants were analyzed at the molecular level and a preliminary assessment was made of small colony mutant karyotypes (230 bands/haploid metaphase cell; large colony mutants typically have normal karyotypes and were not analyzed). AHA induced greatly delayed (7-9 cell doublings) cytotoxicity, suggestive of a mutational mechanism (e.g., base-pair substitution) requiring DNA replication prior to its phenotypic expression. Approximately one-third of the tk -/- mutants formed small colonies, a phenotype which is typically associated with alterations to chromosome 11b, the site of the functional tkb allele in the parental cells. However, banded karyotypes have provided convincing evidence for alterations chromosome 11b in only 2 of the 7 small colony mutants analyzed. Southern blot analysis showed that 78% (21/27) of these small colony mutants have retained the Nco-1 6.3-kb band, which is diagnostic of the tkb allele. This makes AHA unique among the mutagens examined so far in inducing small colony mutants without inducing large losses of tkb DNA. Although a dose-dependent increase in the proportion of small colony mutants was noted, no significant dose-dependent differences were seen at the molecular level in the relatively few mutants analyzed. The majority of AHA-induced tk -/- mutants formed large colonies. Southern blot analysis showed that 86% (25/29) of these had retained the Nco-1 6.3-kb band which is diagnostic of the tkb allele. It is concluded that AHA induces primarily micromutations (less than 100 base pairs), probably through a base-pair substitution mechanism, at the tk, hprt and Na+/K+ ATPase loci in this system, with some larger scale damage (kilobases of DNA at the molecular level; chromosome 11b damage at the cytogenetic level) also occurring.
Collapse
Affiliation(s)
- D Clive
- Wellcome Research Laboratories, Research Triangle Park, NC 27709
| | | | | | | |
Collapse
|