Abstract 1322: Sensitizing radiation-induced integrin β-1 signaling by targeting uPAR in medulloblastoma cells

Abstract

Abstract Although radiation is an effective therapy, it has several adverse effects, including the induction of secondary (new) tumor within the irradiated field. Several studies have reported this effect with medulloblastoma despite effective radiotherapy during the initial stages. Here, we attempt to capitalize on the radiation-induced aggressive behavior of medulloblastoma cells by examining migration, cell adhesion and matrigel invasion properties. Comparison at the mRNA levels between the matrigel-invading and non-invading cells (with and without radiation) clearly demonstrates the aggressiveness of irradiated medulloblastoma cells. RT-PCR analysis confirmed the increased expression of uPA, uPAR, focal adhesion kinase (FAK), N-Cadherin, and integrins like α3, α5, β1 and β6 in irradiated cells. Increased expression of uPAR and integrin β-1 in irradiated cells was also confirmed by immunofluorescence and immunoprecipitation assays. The interaction between uPAR and integrin β-1 and subsequent downstream signaling is a key process in malignant progression and metastasis and has been recently reported in mediating resistance to radiation. With this view, we aimed to study the effect of siRNA-mediated knockdown of uPAR on cell migration and adhesion in irradiated and non-irradiated medulloblastoma cells. Downregulation of uPAR not only reduced cell migration and adhesion, but also reduced the increased migration and adhesiveness associated with irradiated cells. Apart from specific knockdown of uPAR in siRNA-transfected cells, the increased expression of uPAR and integrin β-1 upon radiation were also reduced both at the transcript and protein levels. Studies of the uPAR/integrin β-1 downstream signaling cascade have shown that uPAR knockdown reduces both the expression and phosphorylation of FAK, paxillin, p130Cas and Rac-1, which are known to be actively involved in coordinating tyrosine kinase based signaling related to cell migration and adhesion. Our in vitro results demonstrate that targeting uPAR might sensitize the radiation-induced aggressiveness of medulloblastoma cells by affecting the uPAR/integrin β-1 signaling pathway. 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 1322.