<div>Abstract<p>Glial tumors progress to malignant grades by heightened proliferation and relentless dispersion throughout the central nervous system. Understanding genetic and biochemical processes that foster these behaviors is likely to reveal specific and effective targets for therapeutic intervention. Our current report shows that the fibroblast growth factor-inducible 14 (Fn14), a member of the tumor necrosis factor (TNF) receptor superfamily, is expressed at high levels in migrating glioma cells <i>in vitro</i> and invading glioma cells <i>in vivo</i>. Forced Fn14 overexpression stimulates glioma cell migration and invasion, and depletion of Rac1 by small interfering RNA inhibits this cellular response. Activation of Fn14 signaling by the ligand TNF-like weak inducer of apoptosis (TWEAK) stimulates migration and up-regulates expression of Fn14; this TWEAK effect requires Rac1 and nuclear factor-κB (NF-κB) activity. The Fn14 promoter region contains NF-κB binding sites, which mediate positive feedback causing sustained overexpression of Fn14 and enduring glioma cell invasion. Furthermore, <i>Fn14</i> gene expression levels increase with glioma grade and inversely correlate with patient survival. These results show that the Fn14 cascade operates as a positive feedback mechanism for elevated and sustained Fn14 expression. Such a feedback loop argues for aggressive targeting of the Fn14 axis as a unique and specific driver of glioma malignant behavior. (Cancer Res 2006; 66(19): 9535-42)</p></div>
Supplementary Data 3 from Increased Fibroblast Growth Factor-Inducible 14 Expression Levels Promote Glioma Cell Invasion via Rac1 and Nuclear Factor-κB and Correlate with Poor Patient Outcome
Glioblastoma (GBM) is the most common primary malignant brain tumor in adults, with few effective treatments. EGFR alterations, including expression of the truncated variant EGFRvIII, are among the most frequent genomic changes in these tumors. EGFRvIII is known to preferentially signal through STAT5 for oncogenic activation in GBM, yet targeting EGFRvIII has yielded limited clinical success to date. In this study, we employed patient-derived xenograft (PDX) models expressing EGFRvIII to determine the key points of therapeutic vulnerability within the EGFRvIII-STAT5 signaling axis in GBM. Our findings reveal that exogenous expression of paralogs STAT5A and STAT5B augments cell proliferation and that inhibition of STAT5 phosphorylation in vivo improves overall survival in combination with temozolomide (TMZ). STAT5 phosphorylation is independent of JAK1 and JAK2 signaling, instead requiring Src family kinase (SFK) activity. Saracatinib, an SFK inhibitor, attenuates phosphorylation of STAT5 and preferentially sensitizes EGFRvIII+ GBM cells to undergo apoptotic cell death relative to wild-type EGFR. Constitutively active STAT5A or STAT5B mitigates saracatinib sensitivity in EGFRvIII+ cells. In vivo, saracatinib treatment decreased survival in mice bearing EGFR WT tumors compared to the control, yet in EGFRvIII+ tumors, treatment with saracatinib in combination with TMZ preferentially improves survival.
Abstract Diffuse gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, the loss of CDKN2A/B in IDH-mutant astrocytoma confers an aggressive high grade phenotype and is the strongest implicated molecular alteration associated poor clinical survival, thus is now sufficient to define a grade 4 tumor regardless of histologic grade. However, there remains no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with RNA sequencing data and found the increased expression of regulators of embryonic nervous system development and signaling concurrent with CDKN2A/B loss. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and cell-lines harboring CDKN2A/B homozygous deletion, we stably re-expressed p14ARF, p15INK4B, and p16INK4A using a Tet-inducible system. IDH-mutant cell lines with re-expression of p14, p15, or p16 displayed differential transcription factor activation, impaired neurosphere capability, decreased colony formation, and lower neurosphere proliferation. Intriguingly, RNA-seq data revealed CUX2, a transcription factor known to control neuronal precursor behavior, as the likely candidate regulating the differential expression profile across CDKN2A/B status. We observed increased CUX2 expression in cell lines stably re-expressing p14, p15, and p16. We validated the CUX2 signature across publicly available datasets of IDH-mutant astrocytoma where CUX2 expression negatively correlated with loss of CDKN2A/B in patient tumors. Together our work suggests CUX2 deficiency in IDH-mutant astrocytoma with CDKN2A/B deletion enables an increased neuronal stem-like phenotype in these grade 4 tumors.
Molecular testing (MT) is utilized in neuro-oncology with increasing frequency. The aim of this study was to determine clinical practice patterns to acquire this information, interpret and utilize MT for patient care, and identify unmet needs in the practical clinical application of MT.We conducted a voluntary online survey of providers within the Society for Neuro-Oncology (SNO) membership database between March and April 2019.We received 152 responses out of 2022 SNO members (7.5% of membership). 88.8% of respondents routinely order MT for newly diagnosed gliomas. Of those who do not, testing is preferentially performed in younger patients or those with midline tumors. 82.8% use MT in recurrent gliomas. Other common indications included: metastatic tumors, meningioma, and medulloblastoma. Many providers utilize more than one resource (36.0%), most frequently using in-house (41.8%) over commercially available panels. 78.1% used the results for clinical decision-making, with BRAF, EGFR, ALK, and H3K27 mutations most commonly directing treatment decisions. Approximately, half (48.5%) of respondents have molecular tumor boards at their institutions. Respondents would like to see SNO-endorsed guidelines on MT, organized lists of targeted agents available for specific mutations, a database of targetable mutations and clinical trials, and more educational programs on MT.This survey was marked by several limitations including response rate and interpretation of MT. Among respondents, there is routine use of MT in Neuro-Oncology, however, there remains a need for increased guidance for providers to effectively incorporate the expanding genomic data resulting from MT into daily Neuro-Oncology practice.
Abstract High-grade gliomas represent the most common type of primary adult malignant brain tumor historically diagnosed and graded from histologic criteria alone. Gliomas harboring isocitrate dehydrogenase (IDH) 1 or 2 mutations are associated with lower grade tumors and portend a favorable prognosis relative to IDH-wildtype glioma. However, molecular profiling has identified additional alterations in lower grade gliomas that confer an aggressive high-grade phenotype and a worse clinical prognosis. Of these, the loss of CDKN2A/B in IDH-mutant astrocytoma is the strongest implicated alteration and is sufficient to define a grade 4 tumor regardless of histologic grade. However, there remain no effective therapies targeted at molecular subgroups in aggressive gliomas to date. Here, we sought to elucidate the biologic pathways and functional outcomes associated with the acquisition of high-grade behavior under loss of CDKN2A/B in IDH-mutant astrocytoma to inform future therapeutic strategies. We analyzed a cohort of patient IDH-mutant astrocytomas with whole exome and RNA sequencing data and found several candidate genes/pathways regulated concurrent with CDKN2A/B loss, including regulators of embryonic development, extracellular matrix organization and regulation of vascular processes. Moreover, we identified 1 tumor that displayed intratumoral heterogeneity of CDKN2A/B expression across biopsies. Using grade 4 IDH-mutant astrocytoma patient-derived (PDX) and established cell-lines harboring CDKN2A/B homozygous deletion, we then stably re-expressed cell cycle regulators p14, p15, and p16 using a Tet-inducible lentiviral system and confirmed their decreased proliferation as compared to parental lines. IDH-mutant cell lines with re-expression of p14, p15 or p16 were characterized by differential transcription factor activation and distinct vascular formation patterns as compared to parental lines. These lines also displayed an increased cell migration and invasive potential and were associated with enhanced integrin signaling through integrin beta-3. Together, our work supports a hypothesis of regional tumor evolution with distinct biologic phenotypes across IDH-mutant gliomas.
Abstract Glioblastoma multiforme (GBM) is the most malignant of all primary adult brain tumors, histopathologically characterized by the infiltrative capacity of glioma cells to diffuse into the surrounding normal brain. There are currently no anti-invasion therapies available, and thus the identification and functional understanding of genes that mediate malignant tumor cell dispersion could lead to the discovery of molecular targets which have the potential to respond to therapeutics. We have previously shown that several guanine nucleotide exchange factors for Rho family small GTPases are overexpressed in GBM tumors and play important roles in glioma invasion. Here we report a role for SGEF, a guanine nucleotide exchange factor (GEF) for RhoG, in mediating glioma invasion. SGEF mRNA expression increases in correlation with glioma grade and, within GBM tumors, levels of SGEF expression inversely correlate with patient survival. siRNA-mediated depletion of SGEF decreases in vitro glioma cell migration and ex vivo glioma cell invasion. In addition, genome-wide determination of NF-κB controlled genes in temozolomide-resistant primary GBM xenografts (GBM14-TMZ-R) revealed an increased occupancy of NF-κB on the SGEF gene promoter region via ChIP-on-chip analysis as compared to the parent primary line. In fact, increased phosphorylation of IkBa was detected in GBM-14-TMZ-R. Moreover, inhibition of NF-κB in GBM14-TMZ-R significantly decreases SGEF gene expression, and activation of the NF-κB pathway by TWEAK in GBM cells induces SGEF mRNA expression. Furthermore, siRNA-mediated depletion of SGEF expression enhances chemotherapy-induced cell death in glioma cells. Understanding the role of SGEF in promoting cell motility and chemotherapeutic resistance may direct the development of novel targeted therapeutics for GBM. 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 3846. doi:10.1158/1538-7445.AM2011-3846
Glioblastoma (GBM) is among the most genetically heterogeneous, treatment resistant, and lethal of all human cancers. A significant hurdle to effective treatment of GBM is the aggressive invasion of tumor cells into surrounding healthy brain tissue that invariably leads to tumor recurrence, brain injury, and patient death. These invasive cells preclude complete surgical resection and exhibit marked resistance to chemotherapeutics. As invasion is a universal property of GBM, studies focused on the invasive cell population and on the development of therapies that target them are greatly needed in order to significantly improve the survival of GBM patients. We have previously showed that SGEF (ARHGEF26), a RhoG-specific guanine exchange factor is overexpressed in high-grade brain tumors and correlates with poor patient survival. Here we report that SGEF is critical for promoting GBM invasion and survival by modulation of the DNA repair mechanism. Upon TMZ treatment, SGEF accumulated in the nucleus and mediated BRCA1 binding to γH2AX, and knockdown of SGEF expression in GBM cells impaired the phosphorylation of BRCA1 and CHK1. In addition, GBM cells with stable knockdown of SGEF expression showed enhanced susceptibility to TMZ induced cell death. Re-expression of SGEF in these cells rescued BRCA1 phosphorylation and glioma cell resistance to TMZ. Thus, our data showed an important role for SGEF in mediating GBM cell survival.
