Abstract LB-066: Adenomatous polyposis coli regulates epithelial morphogenesis and migration through FAK/Src signaling

Adenomatous Polyposis Coli (APC) is a multi-functional protein that is lost or mutated in many epithelial cancers including breast, colorectal, and pancreatic cancer. Although APC is well known as a negative regulator of the Wnt/β-catenin signaling pathway, it also binds to the cytoskeleton, microtubules and polarity proteins, such as Dlg and Scribble, suggesting functions in regulation of epithelial polarity and cell migration. Our lab has previously determined that the mammary glands of ApcMin/+ mice demonstrate mis-regulation of epithelial polarity, exhibit early neoplastic changes, and develop more aggressive mammary tumors when crossed to the MMTV-PyMT model of breast cancer. Cells isolated from these tumors displayed activated FAK/Src signaling. Our lab has also shown that APC knockdown in the Madin-Darby Canine Kidney (MDCK) model altered epithelial morphogenesis, resulted in inverted polarity in 3D culture, and up-regulated gene expression of epithelial membrane protein 2 (EMP2). While restoration of the middle β-catenin binding domain was unable to rescue the phenotype, introduction of either full-length or a c-terminal fragment of APC partially restored these phenotypes. The current studies investigate the Wnt-independent mechanisms by which APC regulates these processes using the MDCK model and primary mammary epithelial cells (MECs) isolated from Apc mutant mice. We hypothesize that the c-terminal fragment of APC mediates FAK/Src signaling to regulate 3D morphogenesis, polarity, and migration. Treatment of APC knockdown MDCK cells with PP2, a Src kinase inhibitor, or AIIB2, a β1-integrin inhibitor, eliminated the drastic cyst size changes produced by APC knockdown. Furthermore, inhibition of Src partially restored the polarity phenotype in cysts with APC loss. In addition, shAPC-MDCK cells and MECs isolated from ApcMin/+ mice exhibited increased cell migration compared to control cells indicating a role for APC in cell motility. Preliminary data demonstrates that treatment of shAPC-MDCK cells with PP2, AIIB2, and a FAK inhibitor decreases migration suggesting FAK/Src signaling as a possible mechanism by which APC mediates cell migration. Interestingly, EMP2 has been shown to bind integrin to activate FAK signaling suggesting an interaction in these pathways, and preliminary studies show EMP2 expression is increased in shAPC-MDCK cells during migration. Future studies will aim to dissect the role of the c-terminal fragment and further devise the mechanism by which FAK/Src signaling and EMP2 play a role in APC regulating gene expression, cell migration, and polarity and 3D morphogenesis in MDCK cells and MECs isolated from Apc mutant mice. Investigating the interactions of APC with several targets such as those in the FAK/Src signaling pathway and EMP2 will help identify key players in the role of APC in Wnt-independent tumor development. Citation Format: Alyssa Lesko, Carolyn Ahlers, Jenifer R. Prosperi. Adenomatous polyposis coli regulates epithelial morphogenesis and migration through FAK/Src signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-066. doi:10.1158/1538-7445.AM2015-LB-066