Mammalian cell transformation test

The in vitro mammalian cell transformation test EU Annex V B.21... 

Positive results from the in vitro mammalian cell transformation test indicate that the test substance produces phenotypic changes in cultured mammalian cells associated with malignant transformation in vivo. None of the in vitro test endpoints has an established mechanistic link with cancer. Some of the test systems are capable of detecting tumor promoters. 

In most instances the specimens will be self-evident (e.g., samples of blood, plasma, serum, urine, spinal fluid, aqueous humor, organs, tissues, and tissue fractions that are taken from a test system with the intention of performing an examination or analysis). In other instances the definition may not be as clear. For example, the assay plates used in the mammalian cell transformation assay and the mammalian point mutation assay are considered specimens even though they bear many of the attributes of a test system. For these assays, the originally plated cells plus media and excipients are the test system. After treatment with the test or... 

This usually means that the system should detect three major classes of mutation—genic, chromosomal, and genomic. Only with additional justification would other end points, such as chemical damage to DMA and mammalian cell transformation (neoplastic transformation), be recommended as part of a mutagenicity test battery. Such systems can be validated by demonstrating that they predict mutation. 

Quercetin, a flavonoid component of St. John s wort and several other medicinal plants, has been implicated as a mutagen. However, St. John s Wort aqueous ethanolic extract showed no mutagenic effects in mammalian cells. Tests used included the HGPRT (hypoxanthine guanidine phosphoribosyl transferase) test, the UDS (unscheduled DNA synthesis) test, the cell transformation test uring Syrian hamster embryo cells, the mouse fur spot test, and the chromosome aberration test using Chinese hamster bone marrow cells (Okpanyi et al., 1990). 

Safrole was positive in the following short-term tests for mutagenesis mammalian cell transformation in culture, Rabin s test of degranulation of rough endoplasmic reticulum... 

Ethylbenzene was non-mutagenic in bacteria, yeast and insects. In mammalian cells, it was inactive in inducing sister chromatid exchanges in Chinese hamster embryo cells but very weakly positive in cultured human l5miphocytes. It did not induce micronuclei in vivo, although it was positive in Syrian hamster embryo cells in vitro. It also caused cell transformation in these cells. Ethylbenzene induced mutations in the mouse lymphoma assay, but only at the highest non-lethal concentration tested. 

Stage B Short-term in vitro tests 1. mammalian cell DNA repair 2. bacterial mutagenesis (Ames test) 3. mammalian mutagenesis 4. chromosome tests (sister chromatid exchange) 5. cell transformation... 

In cultured mammalian cells, acrylonitrile induced DNA strand breakage, gene mutation, sister chromatid exchanges and chromosomal aberrations, but not aneuploidy or unscheduled DNA synthesis in rat hepatocytes, at least if the silver grain counting method was used. [Studies using the less reliable scintillation counting method have not been summarized.] Cell transformation was induced in several test systems and gap-junctional intercellular communication was inhibited in one study with Chinese hamster V79 cells. 

Several bacterial and mammalian short-term tests for genetic toxicity as well as their biochemical and genetic rationale are described in Chapter 21 on toxicity testing. They include the salmonella assay, the Chinese hamster ovary cell/hypoxanthine-guanine phosphoribosyl transferase assay, the mouse lymphoma assay, the mammalian transformation assay, sister chromatid exchange, and the chromosome aberration assay. 

Nitromethane has given consistently negative results in bacterial mutagenicity assays, and in vitro mammalian tests for sister chromatid exchanges and chromosomal aberrations. It was not mutagenic in Drosophila. It did not induce micronuclei in vitro in Syrian hamster embryo cells or in vivo in mice. However, nitromethane did show a positive response at high concentration in a cell transformation assay in Syrian hamster embryo cells. The results of shortterm tests on nitromethane do not indicate that the compound has genotoxic activity. 

E. purpurea gave negative results in mammalian cells and bacteria in vitro and in vivo in mice mutagenicity tests. Hamster embryo cell carcinogenicity studies revealed no morphological transformations (25). 

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