On. This has made it extremely difficult 1516647 to completely eradicate a tumor by traditional treatment inhibitor modalities such as surgical resection or radiation [4,5]. As a result tumors frequently recur and none of the current treatment options are ultimately effective [6]. Also notably, although the invasiveness does not necessarily correlate with the grade of malignancy for gliomas [7], it has been shown that invasive GBM cells may have heightened resistance to the induction of apoptosis [8]. Therefore, chemotherapy is often ineffective on these cells, further contributing to GBM’s poor prognosis. Interestingly, decreasing the migratory capabilities of tumor cells can restore a certain level of sensitivity to cytotoxic reagents and increase the 
susceptibility to chemotherapeutic treatments [9,10]. These results suggest that the invasive cell population may represent a more effective treatment target for GBM. Tumor invasion is the result of a complex interaction of cancer cells with the surrounding structures. It begins with individual cell migration, a process that is driven by the cytoskeleton rearrangement and the focal adhesion assembly [11,12]. Cell migration is involved in many normal physiological processes, such asembryonic development, wound healing, and inflammatory response [13,14,15]. It is believed to be a rigidly controlled process that is under the regulation of complex mechanisms mediated by numerous genes. Cells of origin of GBM, be it astrocytes or stem/progenitor cells, are intrinsically migratory. However, the migratory capability of tumor cells varies among patients. It is possible that the enhanced motile phenotype of GBM cells is caused by the lost of one or more regulatory controls, as a direct or indirect result of the numerous somatic mutations that are frequently observed in GBM [16]. Although much has been learned about the phenotypic profile of cell migration in GBM, little is known about its causing mechanism. Characterizing the molecular mechanisms may not only provide better diagnostic and prognostic biomarkers, but also discover novel molecular therapeutic targets. To shed light on the mechanism that drives GBM tumor invasion and to identify novel molecular targets that can possibly be used for Epigenetic Reader Domain disease management, we sought to systematically characterize the genes inhibiting the migration of GBM cells. To this end we adopted a pooled genome-wide RNA interference (RNAi) screening approach [17]. RNAi knocks down the RNA target in a sequence-specific manner and greatly facilitates the study of individual genes [18,19,20]. Paired with genomic sequence data, high-throughput RNAi screening is now possible, allowing systematic functional analysis on a genome-wide scale [21,22,23]. Using this unbiased approach, we successfully identified a number of genes that were later confirmed to regulate GBM cell migration both in vitro and in vivo. Further investigation showed that two of these genes are also associated with the clinical outcome of GBM patients.GBM Cell Migration RNAi ScreeningMethods Ethics statementBrain tumor surgical specimens were obtained following the protocol approved by Methodist Hospital Institutional Review Board (IRB0907-0187). Tissue samples were obtained by The Methodist Hospital Tissue Bank from patients with signed consent forms, the samples were provided to us by the tissue bank without any of the patient’s identity information. All animal experiments were performed following the protocol approved b.On. This has made it extremely difficult 1516647 to completely eradicate a tumor by traditional treatment modalities such as surgical resection or radiation [4,5]. As a result tumors frequently recur and none of the current treatment options are ultimately effective [6]. Also notably, although the invasiveness does not necessarily correlate with the grade of malignancy for gliomas [7], it has been shown that invasive GBM cells may have heightened resistance to the induction of apoptosis [8]. Therefore, chemotherapy is often ineffective on these cells, further contributing to GBM’s poor prognosis. Interestingly, decreasing the migratory capabilities of tumor cells can restore a certain level of sensitivity to cytotoxic reagents and increase the susceptibility to chemotherapeutic treatments 
[9,10]. These results suggest that the invasive cell population may represent a more effective treatment target for GBM. Tumor invasion is the result of a complex interaction of cancer cells with the surrounding structures. It begins with individual cell migration, a process that is driven by the cytoskeleton rearrangement and the focal adhesion assembly [11,12]. Cell migration is involved in many normal physiological processes, such asembryonic development, wound healing, and inflammatory response [13,14,15]. It is believed to be a rigidly controlled process that is under the regulation of complex mechanisms mediated by numerous genes. Cells of origin of GBM, be it astrocytes or stem/progenitor cells, are intrinsically migratory. However, the migratory capability of tumor cells varies among patients. It is possible that the enhanced motile phenotype of GBM cells is caused by the lost of one or more regulatory controls, as a direct or indirect result of the numerous somatic mutations that are frequently observed in GBM [16]. Although much has been learned about the phenotypic profile of cell migration in GBM, little is known about its causing mechanism. Characterizing the molecular mechanisms may not only provide better diagnostic and prognostic biomarkers, but also discover novel molecular therapeutic targets. To shed light on the mechanism that drives GBM tumor invasion and to identify novel molecular targets that can possibly be used for disease management, we sought to systematically characterize the genes inhibiting the migration of GBM cells. To this end we adopted a pooled genome-wide RNA interference (RNAi) screening approach [17]. RNAi knocks down the RNA target in a sequence-specific manner and greatly facilitates the study of individual genes [18,19,20]. Paired with genomic sequence data, high-throughput RNAi screening is now possible, allowing systematic functional analysis on a genome-wide scale [21,22,23]. Using this unbiased approach, we successfully identified a number of genes that were later confirmed to regulate GBM cell migration both in vitro and in vivo. Further investigation showed that two of these genes are also associated with the clinical outcome of GBM patients.GBM Cell Migration RNAi ScreeningMethods Ethics statementBrain tumor surgical specimens were obtained following the protocol approved by Methodist Hospital Institutional Review Board (IRB0907-0187). Tissue samples were obtained by The Methodist Hospital Tissue Bank from patients with signed consent forms, the samples were provided to us by the tissue bank without any of the patient’s identity information. All animal experiments were performed following the protocol approved b.
