Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents

Chapman, K. E.; Doak, S. H.; S., G. J.; Jenkins, Gareth; Doak, Shareen; Chapman, Katherine

doi:10.1093/toxsci/kfv004

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Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents

K. E. Chapman, S. H. Doak, G. J. S. Jenkins, Gareth Jenkins

, Shareen Doak

, Katherine Chapman

Toxicological Sciences, Volume: 144, Issue: 2, Pages: 357 - 365

Swansea University Authors: Gareth Jenkins , Shareen Doak , Katherine Chapman

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DOI (Published version): 10.1093/toxsci/kfv004

Abstract

Risk assessment of human exposure to chemicals is crucial for understanding whether such agents can cause cancer. The current emphasis on avoidance of animal testing has placed greater importance on in vitro tests for the identification of genotoxicants. Selection of an appropriate in vitro dosing r...

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Published in:	Toxicological Sciences
ISSN:	1096-6080 1096-0929
Published:	2015
Online Access:	Check full text
URI:	https://cronfa.swan.ac.uk/Record/cronfa20121

first_indexed	2015-04-23T02:06:01Z
last_indexed	2019-07-02T19:34:31Z
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spelling	2019-07-02T13:49:14.6947955 v2 20121 2015-02-03 Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents a44095d26187304e903da7ca778697b6 0000-0002-5437-8389 Gareth Jenkins Gareth Jenkins true false 8f70286908f67238a527a98cbf66d387 0000-0002-6753-1987 Shareen Doak Shareen Doak true false 19e7d85eec17117858d867ec0c9f575e 0000-0001-6668-0705 Katherine Chapman Katherine Chapman true false 2015-02-03 MEDS Risk assessment of human exposure to chemicals is crucial for understanding whether such agents can cause cancer. The current emphasis on avoidance of animal testing has placed greater importance on in vitro tests for the identification of genotoxicants. Selection of an appropriate in vitro dosing regime is imperative in determining the genotoxic effects of test chemicals. Here, the issue of dosing approaches was addressed by comparing acute and chronic dosing, uniquely using low-dose experiments. Acute 24h exposures were compared with equivalent dosing every 24h over 5-day, fractionated treatment periods. The In Vitro Micronucleus Assay was used to measure clastogenicity induced by methyl methanesulphonate (MMS) and N-methyl-N-nitrosourea (MNU) in human lymphoblastoid cell line, TK6. Quantitative RT-PCR was used to measure mRNA level induction of DNA repair enzymes. Lowest observed genotoxic effect levels (LOGELs) for MMS were obtained at 0.7μg/ml for the acute study and 1.0μg/ml for the chronic study. For acute MNU dosing, a LOGEL was observed at 0.46μg/ml, yet genotoxicity was completely removed following the chronic study. Interestingly, acute MNU dosing demonstrated a statistically significant decrease at 0.009μg/ml. Levels of selected DNA repair enzymes did not change significantly following doses tested. However, p53-deficiency (using the TK6-isogenic cell line, NH32) increased sensitivity to MMS during chronic dosing, causing this LOGEL to equate to the acute treatment LOGEL. In the context of the present data for two alkylating agents, chronic dosing could be a valuable in vitro supplement to acute dosing and could contribute to reduction of unnecessary in vivo follow-up tests Journal Article Toxicological Sciences 144 2 357 365 1096-6080 1096-0929 30 4 2015 2015-04-30 10.1093/toxsci/kfv004 COLLEGE NANME Medical School COLLEGE CODE MEDS Swansea University 2019-07-02T13:49:14.6947955 2015-02-03T10:46:40.3159713 Faculty of Medicine, Health and Life Sciences Swansea University Medical School - Medicine K. E. Chapman 1 S. H. Doak 2 G. J. S. Jenkins 3 Gareth Jenkins 0000-0002-5437-8389 4 Shareen Doak 0000-0002-6753-1987 5 Katherine Chapman 0000-0001-6668-0705 6 0020121-21122017102233.pdf 20121.pdf 2017-12-21T10:22:33.1730000 Output 1181008 application/pdf Accepted Manuscript true 2015-02-27T00:00:00.0000000 true eng
title	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents
spellingShingle	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents Gareth Jenkins Shareen Doak Katherine Chapman
title_short	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents
title_full	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents
title_fullStr	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents
title_full_unstemmed	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents
title_sort	Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents
author_id_str_mv	a44095d26187304e903da7ca778697b6 8f70286908f67238a527a98cbf66d387 19e7d85eec17117858d867ec0c9f575e
author_id_fullname_str_mv	a44095d26187304e903da7ca778697b6_*_Gareth Jenkins 8f70286908f67238a527a98cbf66d387__Shareen Doak 19e7d85eec17117858d867ec0c9f575e_**_Katherine Chapman
author	Gareth Jenkins Shareen Doak Katherine Chapman
author2	K. E. Chapman S. H. Doak G. J. S. Jenkins Gareth Jenkins Shareen Doak Katherine Chapman
format	Journal article
container_title	Toxicological Sciences
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container_start_page	357
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institution	Swansea University
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doi_str_mv	10.1093/toxsci/kfv004
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description	Risk assessment of human exposure to chemicals is crucial for understanding whether such agents can cause cancer. The current emphasis on avoidance of animal testing has placed greater importance on in vitro tests for the identification of genotoxicants. Selection of an appropriate in vitro dosing regime is imperative in determining the genotoxic effects of test chemicals. Here, the issue of dosing approaches was addressed by comparing acute and chronic dosing, uniquely using low-dose experiments. Acute 24h exposures were compared with equivalent dosing every 24h over 5-day, fractionated treatment periods. The In Vitro Micronucleus Assay was used to measure clastogenicity induced by methyl methanesulphonate (MMS) and N-methyl-N-nitrosourea (MNU) in human lymphoblastoid cell line, TK6. Quantitative RT-PCR was used to measure mRNA level induction of DNA repair enzymes. Lowest observed genotoxic effect levels (LOGELs) for MMS were obtained at 0.7μg/ml for the acute study and 1.0μg/ml for the chronic study. For acute MNU dosing, a LOGEL was observed at 0.46μg/ml, yet genotoxicity was completely removed following the chronic study. Interestingly, acute MNU dosing demonstrated a statistically significant decrease at 0.009μg/ml. Levels of selected DNA repair enzymes did not change significantly following doses tested. However, p53-deficiency (using the TK6-isogenic cell line, NH32) increased sensitivity to MMS during chronic dosing, causing this LOGEL to equate to the acute treatment LOGEL. In the context of the present data for two alkylating agents, chronic dosing could be a valuable in vitro supplement to acute dosing and could contribute to reduction of unnecessary in vivo follow-up tests
published_date	2015-04-30T06:39:54Z
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Acute Dosing and p53-Deficiency Promote Cellular Sensitivity to DNA Methylating Agents

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