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© 1988 Oxford University Press

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Presence of a functionally altered ornithine decarboxylase activity in chrysarobin-promoted mouse epidermal papillomas

Thomas G. O'Brien , Kevin O'Donnell , Francis H. Kruszewski 1 and John DiGiovanni 1

The Wistar Institute of Anatomy and Biology 36th and Spruce Streets, Philadelphia, PA 19104
1University of Texas System Cancer Center, Science Park—Research Division PO Box 389, Smithville, TX 78957, USA

Recent work from this laboratory has demonstrated the presence of a structurally and functionally different ornithine decarboxylase (ODC) in mouse epidermal tumors induced by a two-stage protocol involving initiation with 7,12-dimethylbenzanthracene (DMBA) and promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). In this report, the enzymatic properties of ODC present in DMBA-initiated chrysarobin-promoted papillomas are compared to the enzyme induced by chrysarobin in normal epidermis. Analyses of 13 individual tumor extracts indicated each had an elevated level of ODC activity compared to uninduced normal epidermis. Addition of GTP to the enzyme assay caused a marked stimulation of ODC activity in nine of 13 tumor extracts but had no effect on chrysarobin-induced epidermal ODC. Enzyme kinetic analyses indicated that GTP lowered the atypically high apparent Km values for L-orni-thine of the papilloma enzyme to values typical of epidermal ODC. The K1/2 for GTP activation of papilloma ODC was ~ 7 x 10–9 M. When a series of nucleotides was tested, only GTP, the non-hydrolysable analy GTP{gamma}S, dGTP and GDP were capable of significant activation at 1 µM, while other derivatives including GMP, ATP and CTP were less effective. The ability of the tumor enzyme to bind GTP was confirmed by the results of GTP-agarose chromatography, in which the papilloma enzyme (but not chrysarobin-induced epidermal ODC) bound to this affinity column and could be eluted by GTP. While some differences were observed in the properties of ODC from chrysarobin-promoted versus TPA-promoted papillomas, the major conclusion of this study is that both agents cause the appearance of a functionally altered ODC in the majority of papillomas produced by a two-step protocol.


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Home page
 J. Histochem. Cytochem.Home page
R. G. Schipper and A. A.J. Verhofstad
Distribution Patterns of Ornithine Decarboxylase in Cells and Tissues: Facts, Problems, and Postulates
J. Histochem. Cytochem., September 1, 2002; 50(9): 1143 - 1160.
[Abstract] [Full Text] [PDF]


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