Abstract LB-147: Characterization of a Kaiso overexpressing transgenic mouse model

Introduction: The WNT signaling pathway plays critical roles during embryogenesis and maintaining homeostasis of adult tissues. However constitutive WNT signaling leads to tumorigenesis. Upon activation of the WNT pathway, the main downstream effector of the WNT pathway, s-catenin, stabilizes and translocates to the nucleus where it activates transcription of WNT target genes. Recently, our lab along with others identified the novel transcription factor Kaiso as a negative regulator of WNT target genes in mammalian cell lines and Xenopus models. However a study using a Kaiso depleted mouse model implicated Kaiso as a positive regulator of WNT signaling. Kaiso is a member of the BTB/POZ (broad-complex, tramtrack and bric-a-brac/poxvirus and zinc finger) protein family. The goal of this study is to elucidate the role of Kaiso in WNT signaling using the Apc Min/+ mouse model of intestinal cancer. Methodology: To assess the role of Kaiso in colon cancer in vivo, Kaiso overexpressing transgenic mice were created ( Kaiso Tg ). Targeted overexpression of Kaiso in Kaiso Tg mice was obtained by pronuclear injection of Kaiso cDNA under the control of the intestine-specific villin promoter. Reverse transcription PCR (RT-PCR) and Western Blot analyses were used to determine tissue specific Kaiso overexpression in Kaiso Tg mice. Immunohistochemisty (IHC) was performed on mouse intestinal tissues to examine the subcellular localization of Kaiso and assess developmental defects. Kaiso Tg mice were then mated with APC Min /+ mice models of intestinal cancer that develop polyps in the small intestine due to constitutively active -catenin. Kaiso Tg -APC Min/+ mice were examined for gross morphological phenotypes and IHC was performed on mouse intestinal tissues for Kaiso and other WNT target genes (e.g. cyclin D1) to elucidate the effects of Kaiso on the WNT pathway. Results: Western Blot analysis revealed high, moderate and low levels of Kaiso overexpression in three founder lines of the Kaiso Tg mice. RT-PCR analysis showed Kaiso overexpression limited to villin positive tissues including kidney, small and large intestines. IHC analysis of Kaiso Tg tissues showed no gross morphological differences compared to non-transgenic mice. However Kaiso Tg -APC Min/+ displayed decreased body size and weight, and had decreased life span when compared to the parentals (i.e. Kaiso Tg and APC min/+ ). IHC analysis of Kaiso Tg -APC Min/+ mouse intestines revealed increased polyp numbers with Kaiso staining concentrated near the basal surface of the polyps. These data support Kaiso9s potential role as an oncogene in mouse intestinal tissues. 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 LB-147.