Genotoxicity testing gene mutations

Genotoxicity studies are required to identify compounds that can induce genetic damage ranging from single point gene mutations to gross alterations of chromosomal structure. Such effects are taken as indicative of the potential to cause cancer or heritable defects in humans. A standard battery of three types of test is recommended ... 

Genotoxic Effects. No studies were located regarding the genotoxic effects of hexachloroethane in humans after inhalation, oral, or dermal exposure. In vitro studies of hexachloroethane using microbial, fungal, and rodent cell assays are summarized in Table 2-4. Tests of prokaryotic cell systems failed to detect gene mutation (Haworth et al. 1983 Roldan-Arjona et al. 1991 Simmon and Kauhanen 1978 ... 

ICH guidelines specifically require three genotoxicity assays for all devices (see Table 6.2). The assays should preferably evaluate DNA effects, gene mutations and chromosomal aberrations, and two of the assays should preferably use mammalian cells. Guidance for providing tests for selection to meet these needs are the OECD guidelines, which include 8 in vitro and 7 in vivo assays. 

Acrylamide is genotoxic in a number of test systems. It induces gene mutation, structural chromosomal aberrations, sister chromatid exchange, and cell transformation. Furthermore, acrylamide forms covalent adducts with DNA in rodents and covalent adducts with hemoglobin in humans. Flemoglobin adducts have been used for biomonitoring of acrylamide. Studies indicate that the adducts are useful predictors of acrylamide-induced peripheral neuropathy. ... 

The genotoxic potency of ethyl chloride appears to be low. It was negative in in vivo micronucleus tests, but it has produced both positive and negative results in bacterial gene mutation assays. ... 

VDC was genotoxic in a number of test systems it induced chromosome aberrations and sister chromatid exchanges in cultured mammalian cells and DNA damage in mice in vivo gene mutations were observed in vitro for bacteria, yeast, and plant cells after metabolic activation. ... 

Ohno, K., Taaka-Azuma, Y, Yoneda, Y. and Yamada, T. (2005) Genotoxicity test system based on p53R2 gene expression in human cells Examination with 80 chemicals. Mutation Research, 588, 45—57. 

Fortunately, a number of in situ, short-term bioassays to detect genotoxic and related effects have become available. These include a variety of measured endpoints such as aneuploids, chromosal aberrations, DNA damage, dominant lethal mutation, gene mutation, inhibition of intercellular communication, micronuclei, mitotic recombination and gene conversions, and sister chromatid exchange and cell transformation (IARC, 1989). A detailed discussion of these tests is beyond the scope of this book. However, such tests are important from our perspective as atmospheric chemists because, as we shall see, they can be used to detect biologically active compounds in very complex mixtures, and hence serve to focus chemical analysis efforts (IARC, 1989, p. 20). We emphasize in advance the... 

Although not as frequently, several strains of Escherichia coli also are used in genotoxicity testing. E. coli WP2 and its derivatives possess a base-pair substitution in a tryptophan gene.144 Reversion to tryptophan independence can be caused by base-pair substitution mutagens and even some frameshift mutagens. DNA-repair mutations and the pkMIOl plasmid have been introduced into WP2 strains to increase sensitivity. 

Mutagenicity (genotoxicity). A bacterial mutagenicity test that demonstrates the induction of point (gene) mutations is always required. Some mutations result in the development of cancer. 

In general, genotoxicity standard assays (e.g., bacterial reverse mutation assay [Ames test], in vitro chromosomal aberration assay, mouse lymphoma gene mutation assay, and rodent micronucleus assay) may not be suitable assays because the test cells do not contain the appropriate receptors to transport the product (i.e.,not a relevant species) or because the biopharmaceutical... 

Twenty-seven out of 44 FDA-approved biopharmaceuticals have been tested in a battery of genotoxicity assays. Eighty-five different assays performed yielded negative results. The most commonly performed assays were the Ames test, the chromosomal aberration assay in human lymphocytes, the mouse lymphoma gene mutation assay, and the mammalian in vivo erythrocyte micronucleus test. Examples of the range of biopharmaceutical products tested include, domase alfa (deoxyribonuclease I-DNAse), trastuzumab (mAb to human epidermal growth factor receptor 2), alteplase (tissue plasminogen activator), infliximab (mAb to the human tumor necrosis factor a). 

There was no evidence of genotoxicity in the standard genotoxicity test battery bacteria reverse mutation (Ames) tests, forward gene mutations in mammalian (Chinese hamster ovary AS42) cells, or mouse bone marrow MN test... 

Valid information on gene mutations, structure chromosome aberrations (clastogenicity) and numerical chromosome aberrations (aneugenicity) is required. No single test is capable of detecting all relevant genotoxic agents, therefore, a battery of tests is considered appropriate. 

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