| p53 Induction as a Genotoxic Test for Twenty-Five Chemicals Undergoing in Vivo Carcinogenicity Testing Penelope J. Duerksen-Hughes, Jun Yang, and Ozan Ozcan Department of Biology, Georgia State University, Atlanta, Georgia, USA Abstract
In vivo carcinogenicity testing is an expensive and time-consuming process, and as a result, only a relatively small fraction of new and existing chemicals has been tested in this manner. Therefore, the development and validation of alternative approaches is desirable. We previously developed a mammalian in vitro assay for genotoxicity based on the ability of cells to increase their level of the tumor-suppressor protein p53 in response to DNA damage. Cultured cells are treated with various amounts of the test substances, and at defined times following treatment, they are harvested and lysed. The lysates are analyzed for p53 by Western blot and/or enzyme-linked immunosorbent assay analysis. An increase in cellular p53 following treatment is interpreted as evidence for DNA damage. To determine the ability of this p53-induction assay to predict carcinogenicity in rodents and to compare such results with those obtained using alternate approaches, we subjected 25 chemicals from the predictive toxicology evaluation 2 list to analysis with this method. Five substances (citral, cobalt sulfate heptahydrate, D&C Yellow No. 11, oxymetholone, and t-butylhydroquinone) tested positive in this assay, and three substances (emodin, phenolphthalein, and sodium xylenesulfonate) tested as possibly positive. Comparisons between the results obtained with this assay and those obtained with the in vivo protocol, the Salmonella assay, and the Syrian hamster embryo (SHE) cell assay indicate that the p53-induction assay is an excellent predictor of the limited number of genotoxic carcinogens in this set, and that its accuracy is roughly equivalent to or better than the Salmonella and SHE assays for the complete set of chemicals. Key words: assay development, carcinogenicity, genotoxicity, p53, PTE2. Environ Health Perspect 107:805-812 (1999) . [Online 1 September 1999] http://ehpnet1.niehs.nih.gov/docs/1999/107p805-812duerksen-hughes/ abstract.html Address correspondence to P.J. Duerksen-Hughes, Department of Biology, Georgia State University, PO Box 4010, Atlanta, GA 30302 USA. Telephone: (404) 651-0987. Fax: (404) 651-2509. E-mail: biopjd@panther.gsu.edu We acknowledge the assistance and advice of D. Bristol and R. Tennant at the NIEHS, the help of T. Poole and V. Rehder for the statistical analysis, and the contributions of M. Kale and M. Zaki during the early stages of this project. This work was supported in part by NSF grant MCB 9513527 to P.J. Duerksen-Hughes. Received 7 April 1999 ; accepted 11 May 1999.
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