HGPRT test system

It is noteworthy that antitumor active complexes (% T/C < 50), are also the two most mutagenic species as determined by the Ames and CHO/HGPRT test systems (27). The complexes are similar in that (a) through aquation the [Pt(NH3)Cl3] Ion can become a neutral molecule, cts-[Pt(NH3)(H20)Cl2] , and (b) both possess cis-reactive groups. Two Important criteria for antitumor activity to be exhibited are that complexes should be neutral and possess ois-reactlve groups. 

O Neill JP and Hsie AW (1979) The CHO/HGPRT mutation assay experimental procedure. In Hsie AW, O Neill JP, and McElhenny VK (eds.) Mammalian Cell Mutagenesis The Maturation of Test Systems, Banbury Report No. 2, pp. 55-70, 311-318, 407-420. Cold Spring Harbor, NY Cold Spring Harbor Press. 

Chinese Hamster CHO/Hgprt System. Chinese hamster ovary (CHO) cells have 21 or 22 chromosomes with one intact X chromosome and a large acrocentric marker chromosome (Natarajan and Obe, 1982). The use of these cells in mammalian mutation experiments was first reported by Hsie et al. (1975), and was refined into a quantitative assay for mutagenicity testing by O Neill. The performance of this system has been reviewed by the USA EPA Gene-Tox Program. The experimental procedure for this assay is similar to the V79/Hgprt system already described, and for more detailed descriptions the reader is referred to Li et al. (1987). 

Hsie, A.W., O Neill, J.P., Machanoff, R., Schenley, R.L. Brimer, PA. (1981) Screening for mutagenic response of four coded chemicals by the CHO/HGPRT system. In de Serres, F.J. Ashby, J., eds. Evaluation of Short-Term Tests for Carcinogens. Report of the International Collaborative Program (Progress in Mutation Research, Vol. 1). Amsterdam, Elsevier, pp.602-607... 

One system uses mouse lymphoma cells and detects mutations that cause deficiency of thymidine kinase (TK). Another uses Chinese hamster cells and detects mutations in the gene that produces hypoxanthine-guanine phosphoribosyl transferase (HGPRT). Both tests cure efficient, are widely applied, and can be completed in a few weeks. Although not as simple, rapid, and efficient as the Salmonella tests, they have the advantage of being done in a eukaryote. Mammalian-cell cultures cure also used to test for chromosomal mutation. 

For the short-term tests, we recommend a two-tier system. Tier I consists of a microbial gene-mutation test (Salmonella/microsome test), a mammalian cell-culture gene-mutation test (HGPRT or IK), and a mammalian cell-culture chromosomal-breakage test. All these cure to be done both with and without metabolic activation. If the... 

Gene mutation tests in a eukaryotic system in vitro, e.g. the Hypoxanthine - guanine - phosphoribosyl - transferase (HGPRT) gene mutation tests in hamster cells. 

O Neill, J.P., Brimer, P.A., Machanoff, R., Hirsch, G.P., Hsie, A.W. 1977. A quantitative assay of mutation induction at the hypoxanthine-quanine phosphoribosyl transferase locus in Chinese hamster ovary cells (CHO/HGPRT System) Development and definition of the system. Mutat. Res. 45 91-101. Huberman, E. 1976. Cell-mediated mutagenicity of different genetic loci in mammalian cells by carcinogenic polycyclic hydrocarbons. In Screening Tests in Chemical Carcinogenesis, eds. R. Montesano, H. Bartsch,... 

Clearly, further efforts to exploit the use of azg as a selective agent seemed unjustified. It was therefore decided to test 6-mercaptopurine (6-MP), since this substance is also known to undergo ribose phosphorylation through the action of HGPRT enzyme. After several dose-response experiments and some consternation, a standard concentration of 50 ig/ml of 6-MP was deemed suitable. As indicated by the data presented in Table 3, the coincidence survival which troubled us when azg was employed was not a problem. We then proceeded to investigate the efficacy of 6-MP as a selective agent in a forward mutational assay system at the HGPRT locus. 

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