A new statistical method for evaluation of L5178Ytk+/− mammalian cell mutation data using microwell method

Omori, Takashi; Honma, Masamitsu; Hayashi, Makoto; Honda, Yoriko; Yoshimura, Isao

doi:10.1016/s1383-5718(02)00060-8

Cited by 16 publications

(8 citation statements)

References 10 publications

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“…Mutation frequencies were calculated according to the Poisson distribution [Furth et al, 1981]. The data were statistically analyzed by Omori's method, which consists of a modified Dunnett's procedure for identifying clear negative, a Simpson-Margolin procedure for detecting downturn data, and a trend test to evaluate the dose-dependency [Omori et al, 2002]. We evaluated cytotoxicity for TK6 by relative survival (RS), which is calculated from plating efficiency (PE0), and for AHH-1 and h2E1v2 by relative suspension growth (RSG), which is calculated from cell growth rate during 3 days expression period.…”

Section: Mammalian Cell Assays Measuring Gene Mutation and Chromosomementioning

confidence: 99%

Genotoxicity of acrylamide in vitro: Acrylamide is not metabolically activated in standard in vitro systems

Naoki

Yasui

Oda

et al. 2011

Environ and Mol Mutagen

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The recent finding that acrylamide (AA), a genotoxic rodent carcinogen, is formed during the frying or baking of a variety of foods raises human health concerns. AA is known to be metabolized by cytochrome P450 2E1 (CYP2E1) to glycidamide (GA), which is responsible for AA's in vivo genotoxicity and probable carcinogenicity. In in-vitro mammalian cell tests, however, AA genotoxicity is not enhanced by rat liver S9 or a human liver microsomal fraction. In an attempt to demonstrate the in vitro expression of AA genotoxicity, we employed Salmonella strains and human cell lines that overexpress human CYP2E1. In the umu test, however, AA was not genotoxic in the CYP2E1-expressing Salmonella strain or its parental strain. Moreover, a transgenic human lymphoblastoid cell line overexpressing CYP2E1 (h2E1v2) and its parental cell line (AHH-1) both showed equally weak cytotoxic and genotoxic responses to high (>1 mM) AA concentrations. The DNA adduct N7-GA-Gua, which is detected in liver following AA treatment in vivo, was not substantially formed in the in vitro system. These results indicate that AA was not metabolically activated to GA in vitro. Thus, AA is not relevantly genotoxic in vitro, although its in vivo genotoxicity was clearly demonstrated.

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Section: Mammalian Cell Assays Measuring Gene Mutation and Chromosomementioning

confidence: 99%

Genotoxicity of acrylamide in vitro: Acrylamide is not metabolically activated in standard in vitro systems

Naoki

Yasui

Oda

et al. 2011

Environ and Mol Mutagen

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“…We then refed the TFTplates with TFT and incubated them for an additional 14 days for assessing slow-growing TK mutants. We calculated mutant frequencies according to the Poisson distribution [Furth et al, 1981] and analyzed the data by the Omori method, which consists of a modified Dunnett procedure for identifying clear negative results, a Simpson-Margolin procedure for detecting downturn data, and a trend test to evaluate dose-dependency [Omori et al, 2002]. Figure 1 shows the distribution of PE0 (survival) versus PE3 (viability) for the solvent control for TK6 cells (26 data points) and WTK-1 cells (27 data points).…”

Section: Thymidine Kinase Gene Mutation Assaymentioning

confidence: 99%

Comparison of in vitro micronucleus and gene mutation assay results for p53‐competent versus p53‐deficient human lymphoblastoid cells

Honma

Hayashi²

2010

Environ and Mol Mutagen

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The high frequency of false or irrelevant positive results in in vitro mammalian cell genotoxicity tests is a critical concern for regulators. Here, we tested whether such results may be due to the mammalian cells used in the tests being deficient in p53, which is involved in the maintenance of genomic stability. We compared the in vitro responses of two human lymphoblastoid cell lines derived from the same progenitor cell-p53-competent (TK6) and p53-deficient (WTK-1) cells-in a micronucleus (MN) test and a thymidine kinase gene (TK) mutation assay. We tested 14 chemicals including three mutagens and 11 clastogens and spindle poisons. The three mutagens evoked clear positive responses in both assays in both cell lines. The responses to the clastogens and spindle poisons, on the other hand, depended on the assay endpoint and/or the cell line. Most of clastogens and spindle poisons were positive in the MN test in both cell lines. In the TK mutation assay, on the other hand, WTK-1 cells but not TK6 cells detected spindle poisons, which may have been due to the disturbance of the spindle checkpoint and lack of apoptosis in the p53-deficient cells. Some chemicals that induced chromosome aberrations in rodent cells were negative in both TK6 and WTK-1 cells, indicating that a species-specific factor rather than p53 status was associated with the response. In conclusion, the p53 status did not seriously influence the MN test results but it did influence the TK mutation assay results.

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“…For a balanced design with k ¼ 3 this approach based on P 1 j¼1 ð2 j À 1Þ contrasts can be simply demonstrated in Table 1. Omori et al (2002) use the many-to-one comparisons procedure according to Dunnett (1955) for testing an increase at any dose group as a pre-test. This is simply a pairwise contrast test versus control with the contrasts {À1 1 0 0}, {À1 0 1 0} and {À1 0 0 1} in the above example.…”

Section: A Robust Testmentioning

confidence: 99%

A robust statistical procedure for evaluating genotoxicity data

Hothorn

2004

Environmetrics

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SUMMARYThe statistical evaluation of in vitro genotoxicity data is commonly performed by dose-response analysis. Common trend tests cannot be recommended because non-monotonicity may occur due to the use of high dose levels. Several decision tree approaches using preliminary comparisons versus control and conditional eliminating of high doses were proposed. Their heuristic and conservative behavior can be overcome by multiple contrast test, which test on trend and on comparisons versus control simultaneously. Other versions of protected trend test were investigated-each sensitive to any shape of the dose-response. A simple bootstrap approach is proposed using SAS PROC MULTTEST for the analysis of real genotoxicity data.

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A new statistical method for evaluation of L5178Ytk+/− mammalian cell mutation data using microwell method

Cited by 16 publications

References 10 publications

Genotoxicity of acrylamide in vitro: Acrylamide is not metabolically activated in standard in vitro systems

Genotoxicity of acrylamide in vitro: Acrylamide is not metabolically activated in standard in vitro systems

Comparison of in vitro micronucleus and gene mutation assay results for p53‐competent versus p53‐deficient human lymphoblastoid cells

A robust statistical procedure for evaluating genotoxicity data

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