Inhibition of Metabolic Cooperation in V79 Cells: Potential Correlations with Tumor Promotion.
Elmore-E; Langenbach-R; Bohrman-JS
Tumor Promoters: Biological Approaches for Mechanistic Studies and Assay Systems, Raven Press, New York 1988:149-159
The results of a study that evaluated the Chinese-hamster V79 cell metabolic cooperation assay were presented. This in-vitro assay detected carcinogens and other toxicants that promoted tumors through epigenetic mechanisms. Tumor promoters acted by the inhibition of cell to cell communication. In the V79 assay, the amount of cell killing that occurred when toxic 6-thioguanine (154427) (6-TG) monophosphate from wild type cells was transferred to 6-TG resistant cells, was an indication of cell to cell communication inhibition. Five concentrations of each test chemical were used in the metabolic cooperation assay. The culture medium for the assay contained 3 percent fetal bovine serum, 100 6-TG resistant cells and 4x10(5) 6-TG wild type cells. Fifteen minutes after the test chemicals were added, 6-TG was added to the culture medium to a final concentration of 10 microgram per milliliter (microg/ml). After 3 days, the culture medium was replaced with fresh 10microg/ml 6-TG without test chemical. On the sixth or seventh day, the mediums were stained and counted. A parallel cytotoxicity assay was also run without the 6-TG wild type cell. All laboratories showed phorbol ester (17673255) promotional activity. Phenobarbital (50066) produced varying results. Butylated-hydroxyanisol (25013165), butylated-hydroxytoluene (128370), D(+)tryptophan (153946), sodium-cyclamate (139059) and sodium-saccharin (128449) produced weak responses. The peroxides were found to be inactive. N-dodecane (112403) and 1-phenyldodecane (123013) were generally inactive. Phenol (108952), catechol (154234) and pyrogallol (87661) exhibited some activity. A negative response was found for 2,4-dinitrofluorobenzene (70348). Ethyl- phenylpropriolate (2216946) produced a weakly positive result. Agreement among the testing labs and agreement with in-vivo data was compared. The authors conclude that since the promotion of tumors is complex and largely unknown, more experimentation is needed to understand the role of cell to cell communication and the usefulness of the metabolic cooperation assay.
Carcinogens; Tumors; Phenols; In-vitro-studies; Cell-metabolism; Cytotoxicity;
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Tumor Promoters: Biological Approaches for Mechanistic Studies and Assay Systems, Raven Press, New York