Paulino, Vincent M.

Abstract Glioblastoma is the most common and lethal type of primary brain tumor. Despite recent therapeutic advances in other cancers, the treatment of glioblastomas remains ineffective and essentially palliative due the highly invasive nature of the disease. To discern molecular mechanisms that drive GBM migration, we investigated the potential role of differential expression of microRNAs (miRNA) by comparing the matched large-scale, genome-wide miRNA expression profiles of migrating and migration-restricted human glioma cells. Using a radial migration assay, migrating and non-migrating populations from seven well-established glioma cell lines were isolated and utilized for miRNA expression analysis. Statistical analyses revealed 22 miRNAs common to all seven glioma cell lines were down-regulated in the migrating cell population (p < 0.0005) relative to cells in the non-migratory population. Specifically, we report here that the expression level of miR-23b was markedly down-regulated in migrating glioma cells as compared to migration-restricted cells. Over-expression of miR-23b significantly inhibited glioma cell migration and invasion. A bioinformatics search revealed a conserved target site within the 3’untranslated region (UTR) of Pyk2, a non-receptor tyrosine kinase that has been previously implicated in the regulation of glioma cell migration and invasion. Increased expression of miR-23b reduced the expression level of Pyk2 in glioma cells indicating that miR-23b targets Pyk2. Notably, increased expression of miR-23b did not alter the expression level of the related focal adhesion kinase FAK indicating that miR-23b specifically inhibits the expression Pyk2. Taken together, our study demonstrates that reduced expression of miR-23b facilitates the enhancement of glioma cell migration and invasion via modulation of Pyk2 expression. Thus, these data suggest that certain miRNAs may regulate glioma migration and invasion to influence the progression of this disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3994. doi:10.1158/1538-7445.AM2011-3994

Abstract A critical problem in the treatment of malignant gliomas is the extensive infiltration of individual tumor cells into adjacent brain tissues. This invasive phenotype severely limits all current therapies, and to date, no treatment is available to control the spread of this disease. Members of the tumor necrosis factor (TNF) ligand superfamily and their cognate receptors regulate various cellular responses including proliferation, migration, differentiation, and apoptosis. Specifically, the TNFRSF19/TROY gene encodes a type I cell surface receptor that is expressed on migrating or proliferating progenitor cells of the hippocampus, thalamus, and cerebral cortex. Here, we show that levels of TROY mRNA expression directly correlate with increasing glial tumor grade. Among malignant gliomas, TROY expression correlates inversely with overall patient survival. In addition, we show that TROY overexpression in glioma cells activates Rac1 signaling in a Pyk2-dependent manner to drive glioma cell invasion and migration. Pyk2 coimmunoprecipitates with the TROY receptor, and depletion of Pyk2 expression by short hairpin RNA interference oligonucleotides inhibits TROY-induced Rac1 activation and subsequent cellular migration. These findings position aberrant expression and/or signaling by TROY as a contributor, and possibly as a driver, of the malignant dispersion of glioma cells. Mol Cancer Res; 8(11); 1558–67. ©2010 AACR.