Overexpression of a dominant-negative ornithine decarboxylase in mouse skin: effect on enzyme activity and papilloma formation.

Abstract

A transgenic mouse line expressing a truncated form of the ornithine decarboxylase (ODC) dominant-negative mutant K69A/C360A under the control of the keratin 6 promoter has been established (K6/ODCdn mice). These mice were backcrossed onto both the DBA/2J and C57BL/6J backgrounds for subsequent tumorigenesis experiments utilizing an initiation/promotion protocol. In short-term experiments, expression of the ODCdn protein product was induced in the epidermis within 24 h after application of the tumor promoter tetradecanoyl phorbol acetate (TPA) to the skin, and ODC activity in the epidermis of K6/ODCdn mice was reduced by at least 75% compared with littermate controls. However, in tumorigenesis experiments utilizing a variety of initiator (7,12-dimethylbenz[a]anthracene; DMBA) and promoter (TPA) concentrations, K6/ODCdn mice formed at least as many tumors as their littermate controls regardless of background strain. In experiments utilizing chrysarobin, a tumor promoter with a different mechanism of action than TPA, again there was no significant difference in tumor formation between K6/ODCdn mice and littermate controls. Similarly, when K6/ODCdn mice were crossed with K5/ODC mice, a transgenic line described previously which forms tumors without application of a promoting agent, double transgenic mice formed as many tumors as mice expressing the K5/ODC transgene alone. Analysis of epidermis following multiple TPA applications revealed a dramatic spike in ODC activity in both K6/ODCdn mice and non-transgenic mice after six applications, and western blot analysis suggested a stabilization of endogenous wild-type ODC in K6/ODCdn transgenic mice. ODC activity, endogenous protein and polyamines were also elevated in tumors from K6/ODCdn mice. The accumulation of endogenous ODC protein is most probably the result of competition from the transgene-derived ODCdn protein for binding of antizyme, which is known to regulate ODC activity by stimulating degradation of the ODC protein.

• Authors: Lisa M Shantz, Yongjun Guo, Janet A Sawicki, Anthony E Pegg, Thomas G O'Brien
• Journal: Carcinogenesis (Carcinogenesis) Vol. 23 Issue 4 Pg. 657-64 (Apr 2002) ISSN: 0143-3334 [Print] England
• PMID: 11960919 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Anthracenes
• Carcinogens
• chrysarobin
• Ornithine Decarboxylase
• Tetradecanoylphorbol Acetate

Topics

• Animals
• Anthracenes (pharmacology)
• Blotting, Western
• Carcinogens
• Genes, Dominant
• Immunohistochemistry
• Mice
• Mice, Inbred C57BL
• Mice, Inbred DBA
• Mice, Transgenic
• Mutation
• Neoplasm Transplantation
• Ornithine Decarboxylase (biosynthesis, genetics)
• Papilloma (enzymology, genetics)
• Protein Binding
• Skin (enzymology)
• Tetradecanoylphorbol Acetate
• Time Factors