Abstract 2483: Transgenic mice to evaluate the role of S-adenosylmethionine decarboxylase in skin carcinogenesis

Abstract

To evaluate the role of S-adenosylmethionine decarboxylase (AdoMetDC) and altered polyamine levels in mouse skin carcinogenesis, we utilized the tetracycline-regulated system to produce conditional expression of AdoMetDC in basal keratinocytes. AdoMetDC is a key enzyme in polyamine biosynthesis and it catalyzes the decarboxylation reaction converting AdoMet to dcAdoMet. dcAdoMet provides the aminopropyl groups for the synthesis of the higher polyamines spermidine and spermine from the precursor putrescine. Therefore, elevated AdoMetDC activity may promote the synthesis of higher polyamines at the expense of putrescine, and increased putrescine levels are tightly linked to tumor promotion in mouse skin. AdoMetDC activity is also known to be induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). To make the DNA construct for microinjection, human AdoMetDC cDNA was inserted into the TetO vector followed by an internal ribosome entry site and luciferase coding sequence. Potential founder mice were crossed to mice with skin-specific expression of tetracycline-regulated transcriptional activator (tTA) directed by bovine keratin 5 (K5) promoter elements to generate K5-tTA/TetO-AdoMetDC bitransgenic mice. Transgene expression has been characterized by in vivo bioluminescent imaging of luciferase activity, in vitro luciferase activity as well as AdoMetDC activity assay and Western blotting in 7 week old mice. In bitransgenic mice, AdoMetDC is constitutively expressed in the skin and expression can be repressed by exposure to the tetracycline analogue doxycycline (Dox). In untreated bitransgenic mice generated from two founder lines, we saw a massive increase in luciferase activity and these mice have a thin fur phenotype. Minimal transgene expression is detected in either single transgenic TetO-AdoMetDC or Dox-treated bitransgenic mice. Untreated bitransgenic mice from one founder line exhibit a 7.2- fold increase in AdoMetDC activity in epidermis, a 7.8-fold increase in dermis, and dcAdoMet levels are also elevated by 8.0-fold in dermis. Effects of AdoMetDC overexpression on TPA induced polyamine biosynthesis and susceptibility to 7,12-dimethylbenz(a)anthracene/TPA carcinogenesis are now being investigated. These mice with regulated AdoMetDC expression in the skin provide a valuable model system to evaluate the role of AdoMetDC and polyamines in skin carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2483.