Abstract 318: Microglia promote glioma cell migration through a Pyk2 signaling pathway

Abstract

Abstract Glioblastoma multiforme is the most common and most malignant form of glioma. Despite the non-metastatic nature of gliomas, prognosis is poor because tumor cell invasion into surrounding brain leads to recurrence even after radical surgery. Microglia infiltrate most glioma tumors and, therefore, make up an important component of the glioma microenvironment. Microglia may release factors which stimulate signaling pathways and promote glioma cell dispersal and cell invasion. The purpose of the present study was to test the hypothesis that glioma and microglial cells are involved in a reciprocal interaction in the tumor microenvironment where they modulate functions and abilities of each other in order to promote tumor progression and invasion. We hypothesize that microglial cells release soluble factors which promote migration of glioma cells through a Pyk2 signaling pathway. In the present study, we used three different human glioma cell lines with varying levels of invasiveness: A172, U-87MG and HS683, as well as, an immortalized human microglial cell line. We used three experimental groups of glioma cells: group 1 were control glioma cells, group 2 were glioma cells treated with microglia conditioned medium (MCM), and group 3 were glioma cells treated with conditioned medium from microglia that were pretreated with glioma conditioned medium (AMCM). Group 3 simulates the cross-talk between microglia and glioma cells which occurs in the brain. Using a matrigel invasion assay and a wound healing assay, we demonstrated that factors released from microglia significantly increased migration/invasion of glioma cells. The effect was stronger when glioma cells were exposed to microglia activated by glioma conditioned medium (AMCM) to simulate “cross-talk” between glioma and microglial cells as compared to the effect of resting microglia (MCM). To examine potential intracellular pathways that are involved in the process of activation of glioma migration and invasion by microglia, we used a antibody microarray targeting cell signaling proteins. We found upregulation of phosphorylated Tyr579/580 Pyk2 protein in glioma cells treated with MCM and with AMCM. These data were confirmed by Western Blot of rat C6 glioma cells and of A172, U87, HS683 human glioma cell lines demonstrating a common effect of soluble factors released from microglial cells on upregulation of the Pyk2 intracellular pathway in different glioma cell lines. Pyk2 has previously been shown to increase glioma cell migration and invasion. Taken together, these data indicate that microglial cells activate glioma cell migration/dispersal. Furthermore, these interactions activate the pro-migratory-Pyk2 signaling pathway in glioma cells. 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 318. doi:1538-7445.AM2012-318