Abstract 4200: Transgenic mice overexpressing a Claudin-6 tail deletion mutant are resistant to tumor formation

Abstract

Abstract Morphological and physiological observations suggest that the tight junction (TJ)-based permeability barrier is modified/disrupted during tumorigenesis. It is now also widely recognized that the Claudin (Cldn) family of four tetraspan transmembrane proteins is crucial for tight junction assembly and permeability barrier function. However, the detailed roles of the Cldn cytoplasmic tail and extracellular loop domains in these processes or their dysfunction in tumorigenesis are not yet understood. We recently demonstrated that the tail domain of Cldn6 is crucial for membrane targeting and epidermal permeability barrier (EPB) formation, by forced expression of a Cldn6 tail deletion mutant (CDelta187) via the involucrin (Inv) promoter in the suprabasal compartment of the mouse epidermis. Even though a functional barrier formed, Inv-CDelta187 mice displayed histological and biochemical abnormalities in the epidermal differentiation program leading to a thickening of the epidermis after 1 week of age that persisted throughout life. Notably, a significant amount of not only Cldn6, but also Cldn10, Cldn11, and Cldn18 remained cytoplasmically localized and the protein-unfolding pathway was activated in transgenic epidermal cells. Using a well-established two-stage chemical carcinogenesis model, we are now investigating the temporal and spatial changes in expression of these and other (Cldn1, Cldn12) Cldns that we have previously demonstrated to be important in epidermal differentiation and tumorigenesis in CDelta187 versus wild type (WT) mice. METHODS: The lower dorsal backskin of mice was treated topically with 7,12-dimethylbenz(a)anthracene (DMBA; 0.25 mg/ml in acetone) and following a 10-day incubation period, 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 25 microg/ml in acetone) was applied three times a week to the same area. Backskin samples were dissected 2, 4, 6, 8 and 12 weeks after the initiation of the experimental protocol and immunohistochemistry was performed on sections using antibodies against the following: Cldn1, Cldn6, Cldn11, Cldn12, Cldn18, Ki67 (proliferation marker) and CD3 (immune infiltration marker). Strikingly, epidermal tumor formation was inhibited in CDelta187 as compared to WT animals. This is the first demonstration that alterations in Cldn structure and homeostasis may play a protective role against DMBA/TPA-induced skin tumors. Further investigation into the molecular mechanisms underlying this protective function is underway. Supported by CIHR Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. 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 4200.