Abstract 5212: Irradiation-induced uPAR promotes stemness via Wnt/β-catenin signaling in medulloblastoma cells

Abstract

Abstract Urokinase plasminogen activator receptor (uPAR) is known to promote invasion, migration and metastasis in cancer cells. In this study, we show that ionizing radiation (IR) induced uPAR has a role in Wnt/β-catenin signaling and mediates induction of cancer stem cells (CSC)-like properties in medulloblastoma cell lines UW228 and D283. We observed that IR induced the expression of uPAR, CSC markers such as CD44 and Msi-1, and activates Wnt/β-catenin signaling molecules. Overexpression of uPAR after IR treatment led to the activation of Wnt signaling, which was demonstrated by an increase in nuclear translocation of β-catenin and β-catenin-Lef/Tcf-mediated transactivation, thereby promoting cancer stemness. Quercetin, a potent Wnt/β-catenin inhibitor suppressed uPAR and uPAR-mediated Wnt/β-catenin activation. Treatment with shRNA specific for uPAR (pU) suppressed the β-catenin-Tcf/Lef-mediated transactivation both in vitro and in vivo. Further, we show that uPAR is physically associated with the Wnt effector molecule β-catenin using immunocytochemistry and immunohistochemistry; these results were confirmed by immunoprecipitation analysis. Most interestingly, we demonstrate for the first time that the localization of uPAR in the nucleus is associated with transcription factors (TF) and their specific response elements. The association of uPAR with β-catenin-Tcf/Lef complex and various other TF involved in neurogenesis during embryonic development and cancer demonstrates the receptor's possible role at generating CSC-like properties in primitive neuroectodermal tumor (PNET) cells of medulloblastoma. Considering all of the data, we conclude that uPAR is a potent activator of stemness, and the targeting of uPAR in combination with radiation has significant therapeutic implications. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5212. doi:1538-7445.AM2012-5212