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Zhou G, Williams A, LeBlanc DPM, Douglas GR, Yauk CL, Marchetti F. Temporal analyses of germ cell mutations using the MutaMouse model support the recommended design in OECD test guideline 488. Arch Toxicol 2025:10.1007/s00204-025-04085-1. [PMID: 40399496 DOI: 10.1007/s00204-025-04085-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2025] [Accepted: 05/07/2025] [Indexed: 05/23/2025]
Abstract
The Organisation for Economic Co-operation and Development test guideline (TG) 488 uses transgenic rodent models to assess in vivo mutagenesis. TG 488 recommends 28 consecutive days of exposure with sampling of germ cells from seminiferous tubules 28 days post-exposure (i.e., 28 + 28d). We analyzed mutant frequencies (MF) in male germ cells up to 70 days post-exposure to determine whether designs other than 28 + 28d are necessary for assessing germ cell mutagenicity. Adult MutaMouse males received various doses of benzo(a)pyrene (BaP), N-ethyl-N-nitrosourea (ENU), isopropyl methanesulfonate (iPMS), or procarbazine (PRC) alongside vehicle controls for 28 days orally. Germ cells were collected from seminiferous tubules at + 3d, + 28d, + 42d, or + 70d post-exposure and MF quantified using the lacZ assay. Significant increases in lacZ MF were observed for all four chemicals at 28 + 28d. No further increases occurred at later sampling times. There was no significant effect with BaP at 28 + 3d, and a significantly stronger response with ENU and BaP at 28 + 28d compared to 28 + 3d. PRC produced the strongest response at 28 + 3d, while there was no impact of different sampling times for iPMS. Both these chemicals significantly reduced testis weight at 28 + 3d and 28 + 28d. Finally, benchmark dose modeling generated overlapping confidence intervals among the four sampling times for ENU, iPMS, and PRC. However, for BaP, the confidence interval was significantly greater at 28 + 3d than at the other sampling times. These results support the use of the 28 + 28d design as the recommended experimental design for germ cells in TG 488 and that later sampling times are not necessary.
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Affiliation(s)
- Gu Zhou
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, 251 Sir Frederick Banting Driveway, Ottawa, Health CanadaON, K1A 0K9, Canada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, 251 Sir Frederick Banting Driveway, Ottawa, Health CanadaON, K1A 0K9, Canada
| | - Danielle P M LeBlanc
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, 251 Sir Frederick Banting Driveway, Ottawa, Health CanadaON, K1A 0K9, Canada
| | - George R Douglas
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, 251 Sir Frederick Banting Driveway, Ottawa, Health CanadaON, K1A 0K9, Canada
| | - Carole L Yauk
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, 251 Sir Frederick Banting Driveway, Ottawa, Health CanadaON, K1A 0K9, Canada.
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Santarsieri A, Mitchell E, Pham MH, Sanghvi R, Jablonski J, Lee-Six H, Sturgess K, Brice P, Menne TF, Osborne W, Creasey T, Ardeshna KM, Baxter J, Behan S, Bhuller K, Booth S, Chavda ND, Collins GP, Culligan DJ, Cwynarski K, Davies A, Downing A, Dutton D, Furtado M, Gallop-Evans E, Hodson A, Hopkins D, Hsu H, Iyengar S, Jones SG, Karanth M, Linton KM, Lomas OC, Martinez-Calle N, Mathur A, McKay P, Nagumantry SK, Phillips EH, Phillips N, Rudge JF, Shah NK, Stafford G, Sternberg A, Trickey R, Uttenthal BJ, Wetherall N, Zhang XY, McMillan AK, Coleman N, Stratton MR, Laurenti E, Borchmann P, Borchmann S, Campbell PJ, Rahbari R, Follows GA. The genomic and clinical consequences of replacing procarbazine with dacarbazine in escalated BEACOPP for Hodgkin lymphoma: a retrospective, observational study. Lancet Oncol 2025; 26:98-109. [PMID: 39674188 DOI: 10.1016/s1470-2045(24)00598-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Revised: 10/07/2024] [Accepted: 10/18/2024] [Indexed: 12/16/2024]
Abstract
BACKGROUND Procarbazine-containing chemotherapy regimens are associated with cytopenias and infertility, suggesting stem-cell toxicity. When treating Hodgkin lymphoma, procarbazine in escalated-dose bleomycin-etoposide-doxorubicin-cyclophosphamide-vincristine-procarbazine-prednisolone (eBEACOPP) is increasingly replaced with dacarbazine (eBEACOPDac) to reduce toxicity. We aimed to investigate the impact of this drug substitution on the mutation burden in stem cells, patient survival, and toxicity. METHODS In this two-part retrospective, observational study, we first compared mutational landscapes in haematopoietic stem and progenitor cells (HSPCs) from patients with advanced-stage Hodgkin lymphoma in remission for at least 6 months who had been treated with eBEACOPDac (eBEACOPDac cohort), eBEACOPP (real-world eBEACOPP cohort), or doxorubicin-bleomycin-vinblastine-dacarbazine (ABVD); in buccal DNA from five children of a female patient with classical Hodgkin lymphoma treated with eBEACOPP before conceiving the third child; in sperm DNA from a patient with mild oligospermia treated with eBEACOPP; and in caecal adenocarcinoma and healthy colon tissue from a survivor of Hodgkin lymphoma treated with chlorambucil-vinblastine-procarbazine-prednisolone. For the second part, we analysed efficacy and toxicity data from adult patients (aged >16 years) treated with first-line eBEACOPDac (eBEACOPDac cohort) at 25 centres across UK, Ireland, and France; efficacy was compared with the German HD18 eBEACOPP trial data and toxicity with a UK real-world dataset. Participants in the German HD18 and UK real-world datasets were adults (aged >16 years) with previously untreated Hodgkin lymphoma, treated with first-line eBEACOPP. We had two co-primary objectives: to define the comparative stem-cell mutation burden and mutational signatures after treatment with or without procarbazine-containing chemotherapy (first study part); and to determine progression-free survival of patients with Hodgkin lymphoma treated with eBEACOPP or eBEACOPDac (second study part). Secondary objectives included overall survival and explored differences in specific toxicity outcomes, including transfusion requirements and measures of reproductive health (second study part). FINDINGS In the first part of the study (mutational analysis), patients treated with eBEACOPP (n=5) exhibited a higher burden of point mutations in HSPCs compared with those treated with eBEACOPDac (n=4) or ABVD (n=3; excess mutations 1150 [95% CI 934-1366] vs 290 [241-339] vs 186 [116-254]). Two novel mutational signatures, SBSA (SBS25-like) and SBSB, were identified in HSPCs and in a single neoplastic and healthy colon sample from patients who received procarbazine-containing chemotherapy. SBSB was also identified in germline DNA of three children conceived after eBEACOPP and in sperm of a male patient treated with eBEACOPP. SBSC was detected in patients treated with either ABVD or eBEACOPDac. In the second part of the study (efficacy and toxicity analysis), dacarbazine substitution did not appear to compromise efficacy or safety. 312 patients treated with eBEACOPDac (eBEACOPDac cohort; treated 2017-22, 186 [60%] male, median follow-up 36·0 months [IQR 25·2-50·1]) had a 3-year progression-free survival of 93·3% (95% CI 90·3-96·4), which was similar to the 93·3% [95% CI 92·1-94·4]) progression-free survival seen in 1945 patients in the German HD18 eBEACOPP trial (treated 2008-14, 1183 [61%] male, median follow-up 57·0 months [35·4-64·7]). Patients treated with eBEACOPDac required fewer blood transfusions (mean 1·70 units [SD 2·77] vs 3·69 units [3·89]; p<0·0001), demonstrated higher post-chemotherapy sperm concentrations (median 23·4 million per mL [IQR 11·0-632·3] vs 0·0 million per mL [0·0-0·001]; p=0·0040), and had earlier resumption of menstrual periods (mean 5·04 months [SD 3·07] vs 8·77 months [5·57]; p=0·0036) compared with 73 patients treated with eBEACOPP in the UK real-world dataset. INTERPRETATION Procarbazine induces a higher mutation burden and novel mutational signatures in patients with Hodgkin lymphoma treated with eBEACOPP and their germline DNA, raising concerns for the genomic health of survivors of Hodgkin lymphoma and hereditary consequences for their offspring. However, replacing procarbazine with dacarbazine appears to mitigate gonadal and stem-cell toxicity while maintaining similar clinical efficacy. FUNDING Addenbrooke's Charitable Trust and Wellcome Trust.
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Affiliation(s)
- Anna Santarsieri
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK; University of Cambridge, Wellcome-Medical Research Council Stem Cell Institute, Cambridge, UK; Faculty of Health, Medicine, and Social Care, Anglia Ruskin University, Cambridge, UK
| | - Emily Mitchell
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK; University of Cambridge, Wellcome-Medical Research Council Stem Cell Institute, Cambridge, UK
| | - My H Pham
- Wellcome Sanger Institute, Cambridge, UK
| | | | - Janina Jablonski
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Düsseldorf, University of Cologne, Medical Faculty and University Hospital Cologne, Cologne, Germany; German Hodgkin Study Group, Cologne, Germany
| | - Henry Lee-Six
- Wellcome Sanger Institute, Cambridge, UK; Department of Pathology, University of Cambridge, Cambridge, UK
| | - Katherine Sturgess
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Pauline Brice
- APHP Hôpital Saint-Louis, Hemato-Oncologie, Paris, France
| | - Tobias F Menne
- Department of Haematology, Freeman Hospital, Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, UK
| | - Wendy Osborne
- Department of Haematology, Freeman Hospital, Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, UK; Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Thomas Creasey
- Department of Haematology, Freeman Hospital, Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, UK
| | - Kirit M Ardeshna
- Department of Haematology, University College London Hospitals NHS Foundation Trust, London, UK
| | - Joanna Baxter
- Cambridge Blood and Stem Cell Biobank, NHS-BT Cambridge Centre, Cambridge, UK
| | - Sarah Behan
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Kaljit Bhuller
- Department of Haematology, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Stephen Booth
- Department of Haematology, Royal Berkshire Hospital, Reading, UK
| | - Nikesh D Chavda
- Department of Haematology, University Hospitals Bristol and Weston NHS Foundation Trust, Bristol, UK
| | - Graham P Collins
- Department of Haematology, Oxford University Hospitals NHS Foundation Trust, Churchill Hospital, Oxford, UK
| | | | - Kate Cwynarski
- Department of Haematology, University College London Hospitals NHS Foundation Trust, London, UK
| | - Andrew Davies
- Department of Haematology, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Abigail Downing
- Department of Haematology, Velindre Cancer Centre, Cardiff, UK
| | - David Dutton
- Department of Haematology, Great Western Hospitals NHS Foundation Trust, Swindon, UK
| | | | | | - Andrew Hodson
- Department of Haematology, Ipswich Hospital NHS Trust, Ipswich, UK
| | - David Hopkins
- Department of Haematology, Beatson West of Scotland Cancer Centre, Glasgow, UK
| | - Hannah Hsu
- Department of Haematology, University College London Hospitals NHS Foundation Trust, London, UK
| | - Sunil Iyengar
- Department of Haematology, Royal Marsden Hospital, London, UK
| | - Stephen G Jones
- Department of Haematology, Sherwood Forest Hospitals NHS Foundation Trust, Sutton-in-Ashfield, UK
| | - Mamatha Karanth
- Department of Haematology, West Suffolk NHS Foundation Trust, Bury St Edmunds, UK
| | - Kim M Linton
- Department of Haematology, University of Manchester and the Christie Hospital, Division of Cancer Sciences, Manchester, UK
| | - Oliver C Lomas
- Department of Haematology, Oxford University Hospitals NHS Foundation Trust, Churchill Hospital, Oxford, UK
| | | | - Abhinav Mathur
- Department of Haematology, Aberdeen Royal Infirmary, Aberdeen, UK
| | - Pamela McKay
- Department of Haematology, Beatson West of Scotland Cancer Centre, Glasgow, UK
| | | | - Elizabeth H Phillips
- Department of Haematology, University of Manchester and the Christie Hospital, Division of Cancer Sciences, Manchester, UK
| | - Neil Phillips
- Department of Haematology, Royal Stoke University Hospital, Stoke-on-Trent, UK
| | - John F Rudge
- Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Nimish K Shah
- Department of Haematology, Norfolk and Norwich University Hospitals NHS Foundation Trust, Norwich, UK
| | - Gwyneth Stafford
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Alex Sternberg
- Department of Haematology, Great Western Hospitals NHS Foundation Trust, Swindon, UK
| | - Rachel Trickey
- Department of Haematology, Velindre Cancer Centre, Cardiff, UK
| | - Benjamin J Uttenthal
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Natasha Wetherall
- Department of Haematology, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Xiao-Yin Zhang
- Department of Haematology, Oxford University Hospitals NHS Foundation Trust, Churchill Hospital, Oxford, UK
| | - Andrew K McMillan
- Department of Haematology, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | | | | | - Elisa Laurenti
- University of Cambridge, Wellcome-Medical Research Council Stem Cell Institute, Cambridge, UK
| | - Peter Borchmann
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Düsseldorf, University of Cologne, Medical Faculty and University Hospital Cologne, Cologne, Germany; German Hodgkin Study Group, Cologne, Germany
| | - Sven Borchmann
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Düsseldorf, University of Cologne, Medical Faculty and University Hospital Cologne, Cologne, Germany; German Hodgkin Study Group, Cologne, Germany
| | | | | | - George A Follows
- Department of Haematology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK; Faculty of Health, Medicine, and Social Care, Anglia Ruskin University, Cambridge, UK; Department of Haematology, University of Cambridge, Cambridge, UK.
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Dodge AE, LeBlanc DPM, Zhou G, Williams A, Meier MJ, Van P, Lo FY, Valentine Iii CC, Salk JJ, Yauk CL, Marchetti F. Duplex sequencing provides detailed characterization of mutation frequencies and spectra in the bone marrow of MutaMouse males exposed to procarbazine hydrochloride. Arch Toxicol 2023; 97:2245-2259. [PMID: 37341741 PMCID: PMC10322784 DOI: 10.1007/s00204-023-03527-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 05/17/2023] [Indexed: 06/22/2023]
Abstract
Mutagenicity testing is an essential component of health safety assessment. Duplex Sequencing (DS), an emerging high-accuracy DNA sequencing technology, may provide substantial advantages over conventional mutagenicity assays. DS could be used to eliminate reliance on standalone reporter assays and provide mechanistic information alongside mutation frequency (MF) data. However, the performance of DS must be thoroughly assessed before it can be routinely implemented for standard testing. We used DS to study spontaneous and procarbazine (PRC)-induced mutations in the bone marrow (BM) of MutaMouse males across a panel of 20 diverse genomic targets. Mice were exposed to 0, 6.25, 12.5, or 25 mg/kg-bw/day for 28 days by oral gavage and BM sampled 42 days post-exposure. Results were compared with those obtained using the conventional lacZ viral plaque assay on the same samples. DS detected significant increases in mutation frequencies and changes to mutation spectra at all PRC doses. Low intra-group variability within DS samples allowed for detection of increases at lower doses than the lacZ assay. While the lacZ assay initially yielded a higher fold-change in mutant frequency than DS, inclusion of clonal mutations in DS mutation frequencies reduced this discrepancy. Power analyses suggested that three animals per dose group and 500 million duplex base pairs per sample is sufficient to detect a 1.5-fold increase in mutations with > 80% power. Overall, we demonstrate several advantages of DS over classical mutagenicity assays and provide data to support efforts to identify optimal study designs for the application of DS as a regulatory test.
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Affiliation(s)
- Annette E Dodge
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Danielle P M LeBlanc
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Gu Zhou
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Matthew J Meier
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada
| | - Phu Van
- TwinStrand Biosciences Inc., Seattle, Washington, USA
| | - Fang Yin Lo
- TwinStrand Biosciences Inc., Seattle, Washington, USA
| | | | - Jesse J Salk
- TwinStrand Biosciences Inc., Seattle, Washington, USA
| | - Carole L Yauk
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
- Department of Biology, Carleton University, Ottawa, Ontario, Canada.
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, Ontario, Canada.
- Department of Biology, Carleton University, Ottawa, Ontario, Canada.
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Marchetti F, Zhou G, LeBlanc D, White PA, Williams A, Yauk CL, Douglas GR. The 28 + 28 day design is an effective sampling time for analyzing mutant frequencies in rapidly proliferating tissues of MutaMouse animals. Arch Toxicol 2021; 95:1103-1116. [PMID: 33506374 PMCID: PMC7904718 DOI: 10.1007/s00204-021-02977-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 01/04/2021] [Indexed: 12/15/2022]
Abstract
The Organisation for Economic Co-Operation and Development Test Guideline 488 (TG 488) uses transgenic rodent models to generate in vivo mutagenesis data for regulatory submission. The recommended design in TG 488, 28 consecutive daily exposures with tissue sampling three days later (28 + 3d), is optimized for rapidly proliferating tissues such as bone marrow (BM). A sampling time of 28 days (28 + 28d) is considered more appropriate for slowly proliferating tissues (e.g., liver) and male germ cells. We evaluated the impact of the sampling time on mutant frequencies (MF) in the BM of MutaMouse males exposed for 28 days to benzo[a]pyrene (BaP), procarbazine (PRC), isopropyl methanesulfonate (iPMS), or triethylenemelamine (TEM) in dose-response studies. BM samples were collected + 3d, + 28d, + 42d or + 70d post exposure and MF quantified using the lacZ assay. All chemicals significantly increased MF with maximum fold increases at 28 + 3d of 162.9, 6.6, 4.7 and 2.8 for BaP, PRC, iPMS and TEM, respectively. MF were relatively stable over the time period investigated, although they were significantly increased only at 28 + 3d and 28 + 28d for TEM. Benchmark dose (BMD) modelling generated overlapping BMD confidence intervals among the four sampling times for each chemical. These results demonstrate that the sampling time does not affect the detection of mutations for strong mutagens. However, for mutagens that produce small increases in MF, sampling times greater than 28 days may produce false-negative results. Thus, the 28 + 28d protocol represents a unifying protocol for simultaneously assessing mutations in rapidly and slowly proliferating somatic tissues and male germ cells.
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Affiliation(s)
- Francesco Marchetti
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada.
| | - Gu Zhou
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada
| | - Danielle LeBlanc
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada
| | - Paul A White
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada
| | - Andrew Williams
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada
- Department of Biology, University of Ottawa, Ottawa, ON, Canada
| | - George R Douglas
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 251 Sir Frederick Banting Driveway, Ottawa, ON, K1A 0K9, Canada
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Kirby C, Baig A, Avlasevich SL, Torous DK, Tian S, Singh P, Bemis JC, Saubermann LJ, Dertinger SD. Dextran sulfate sodium mouse model of inflammatory bowel disease evaluated for systemic genotoxicity via blood micronucleus and Pig-a gene mutation assays. Mutagenesis 2020; 35:161-167. [PMID: 32050029 DOI: 10.1093/mutage/geaa006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 01/24/2020] [Indexed: 12/31/2022] Open
Abstract
Inflammatory bowel disease (IBD) is an important risk factor for gastrointestinal cancers. Inflammation and other carcinogenesis-related effects at distal, tissue-specific sites require further study. In order to better understand if systemic genotoxicity is associated with IBD, we exposed mice to dextran sulfate sodium salt (DSS) and measured the incidence of micronucleated cells (MN) and Pig-a mutant phenotype cells in blood erythrocyte populations. In one study, 8-week-old male CD-1 mice were exposed to 0, 1, 2, 3 or 4% w/v DSS in drinking water. The 4-week in-life period was divided into four 1-week intervals-alternately on then off DSS treatment. Low volume blood samples were collected for MN analysis at the end of each week, and cardiac blood samples were collected at the end of the 4-week period for Pig-a analyses. The two highest doses of DSS were observed to induce significant increases in reticulocyte frequencies. Even so, no statistically significant treatment-related effects on the genotoxicity biomarkers were evident. While one high-dose mouse showed modestly elevated MN frequencies during the DSS treatment cycles, it also exhibited exceptionally high reticulocyte frequencies (e.g. 18.7% at the end of the second DSS cycle). In a second study, mice were treated with 0 or 4% DSS for 9-18 consecutive days. Exposure was continued until rectal bleeding or morbidity was evident, at which point the treatment was terminated and blood was collected for MN analysis. The Pig-a assay was conducted on samples collected 29 days after the start of treatment. The initial blood specimens showed highly elevated reticulocyte frequencies in DSS-exposed mice (mean ± SEM = 1.75 ± 0.10% vs. 13.04 ± 3.66% for 0 vs. 4% mice, respectively). Statistical analyses showed no treatment-related effect on MN or Pig-a mutant frequencies. Even so, the incidence of MN versus reticulocytes in the DSS-exposed mice were positively correlated (linear fit R2 = 0.657, P = 0.0044). Collectively, these results suggest that in the case of the DSS CD-1 mouse model, systemic effects include stress erythropoiesis but not remarkable genotoxicity. To the extent MN may have been slightly elevated in a minority of individual mice, these effects appear to be secondary, likely attributable to stimulated erythropoiesis.
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Affiliation(s)
| | - Ayesha Baig
- Department of Pediatrics, University of Rochester Medical Center, Rochester, NY
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6
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Beal MA, Meier MJ, LeBlanc DP, Maurice C, O'Brien JM, Yauk CL, Marchetti F. Chemically induced mutations in a MutaMouse reporter gene inform mechanisms underlying human cancer mutational signatures. Commun Biol 2020; 3:438. [PMID: 32796912 PMCID: PMC7429849 DOI: 10.1038/s42003-020-01174-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 07/24/2020] [Indexed: 02/07/2023] Open
Abstract
Transgenic rodent (TGR) models use bacterial reporter genes to quantify in vivo mutagenesis. Pairing TGR assays with next-generation sequencing (NGS) enables comprehensive mutation pattern analysis to inform mutational mechanisms. We used this approach to identify 2751 independent lacZ mutations in the bone marrow of MutaMouse animals exposed to four chemical mutagens: benzo[a]pyrene, N-ethyl-N-nitrosourea, procarbazine, and triethylenemelamine. We also collected published data for 706 lacZ mutations from eight additional environmental mutagens. We report that lacZ gene sequencing generates chemical-specific mutation signatures observed in human cancers with established environmental causes. For example, the mutation signature of benzo[a]pyrene, a carcinogen present in tobacco smoke, matched the signature associated with tobacco-induced lung cancers. Our results suggest that the analysis of chemically induced mutations in the lacZ gene shortly after exposure provides an effective approach to characterize human-relevant mechanisms of carcinogenesis and propose novel environmental causes of mutation signatures observed in human cancers.
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Affiliation(s)
- Marc A Beal
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, K1A 0K9, Canada
- Existing Substances Risk Assessment Bureau, Health Canada, Ottawa, ON, Canada
| | - Matthew J Meier
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, K1A 0K9, Canada
| | - Danielle P LeBlanc
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, K1A 0K9, Canada
| | - Clotilde Maurice
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, K1A 0K9, Canada
- Existing Substances Risk Assessment Bureau, Health Canada, Ottawa, ON, Canada
| | - Jason M O'Brien
- National Wildlife Research Centre, Environment and Climate Change Canada, Ottawa, ON, K1A 0H3, Canada
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, K1A 0K9, Canada
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, K1A 0K9, Canada.
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