Regulation Of Glioma Invasion Research Articles

Abstract 510: A novel role for Olig2 in the regulation of glioma invasion

Abstract Glioblastoma multiforme (GBM) are highly infiltrative, aggressive and lethal primary brain tumors in adults that are resistant to conventional treatments. A major clinical obstacle in the treatment of GBMs is the ability of glioma cells to invade the surrounding brain parenchyma, preventing their complete surgical resection. Several studies have shown that invasive glioma stem cells (GSCs) extend beyond the surgically resected regions. These invasive cells are the cause for tumor recurrence and poor prognosis in GBM patients. The molecular and cellular mechanism involved in the regulation of the switch from proliferation to invasion/migration in GBM is poorly understood. We investigated the role of Olig2, a Central Nervous System (CNS) specific transcription factor, in promoting the switch from proliferating to invading glioma cell. Genetically relevant murine glioma model as well as patient-derived glioma stem cells (GSCs) were utilized to identify the effect of Olig2 on glioma invasion. Functionally, Olig2-mediated invasion was assessed by 3D-transwell invasion assays, organotypic slice cultures as well as PDX tumors in immunocompromised mice. In addition, murine and patient-derived GSCs were utilized to identify direct genetic targets of Olig2 involved in glioma invasion by ChIP-seq and RNA-seq. Our data demonstrate that Olig2-expressing murine glioma stem/progenitor-like cells are highly invasive as compared to Olig2 knockout cells. We further corroborated the requirement of Olig2 for glioma invasion in patient-derived GSCs by utilizing shRNA-mediated knockdown of Olig2. Olig2 depletion resulted in reduced glioma cell invasion in at least four independent human GSCs. Recent studies have shown that activation of transcription factors such as Zeb1 and Twist1 occurs in invasive high grade gliomas. We show that knockdown of Olig2 in murine as well as human GSCs leads to a significant decrease in the expression of invasion genes such as Zeb1, Vimentin, Twist1, and Stat3 as compared to control cells. In conclusion, our studies highlight a novel role for the Olig2 signalling network in promoting the switch from proliferation to invasion in GBM, and provide a plausible target for inhibiting glioma invasion. Citation Format: Shiv K. Singh, Nicole Giannonatti, Robert Kupp, Costanza Lo Cascio, Shwetal Mehta. A novel role for Olig2 in the regulation of glioma invasion. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 510. doi:10.1158/1538-7445.AM2015-510

Abstract 4999: Paracrine regulation of glioma invasion by astrocytes is mediated by glial derived neurothropic factor

Abstract Purpose: Glial cells have been shown to play a role in glioma progression. Here we investigate the mechanism by which astrocytes which are abundant in glioma tumors, promote cancer cell invasion. Experimental Design: In this study, we evaluated the effects of astrocytes on glioma biology both in vitro and in vivo and determined the downstream paracrine effect of glial derived neurotropic factor (GDNF) on tumor invasion. Results: Astrocytes conditioned media (ACM) significantly increased human and murine glioma cells migration compared to controls. This effect was inhibited when the activity of GDNF on glioma cells was blocked by RET-Fc chimera or anti-GDNF Ab and by siRNA directed against GDNF expression by astrocytes. Glioma cell incubation with ACM led to time dependent phosphorylation of the GDNF receptor, RET and downstream AKT phosphorylation. Tumor migration and GDNF-RET-AKT activation was inhibited by the RET small molecule inhibitor pyrazolopyrimidine-1 and by the AKT inhibitor LY294002. Finally, blocking of RET by pyrazolopyrimidine-1 or knockout of the RET co receptor GFRα1 in glioma cells reduced the size of brain tumors in immunocompetent mice. Conclusions: We suggest a mechanism by which astrocytes attracted to the glioma microenvironment facilitate brain invasion by secretion of GDNF and activation of RET/GFRα1 receptors expressed by the cancer cells. Note: This abstract was not presented at the meeting. Citation Format: Moran Amit, Ayelet Shabtay-Orbach, Yoav Binenbaum, Ziv Gil. Paracrine regulation of glioma invasion by astrocytes is mediated by glial derived neurothropic factor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4999. doi:10.1158/1538-7445.AM2014-4999

Abstract 5271: Ibuprofen, an inhibitor of angiogenesis, enhances radiosensitivity and suppresses glioma invasion: Role of p75NTR and VEGF

Abstract Current treatments of malignant glioma, including anti-VEGF therapy, are limited by the invasive phenotype. Ionizing radiation is known to stimulate invasion, and p75NTR is a key regulator of glioma invasion. Because angiogenic inhibitors have been proposed as radiosensitizers, we hypothesized that ibuprofen (previously shown to regulate p75NTR) would serve as a radiosensitizer of glioma cells, and we studied its effect on glioma migration, invasion, and the expression of p75NTR and VEGF. The purpose of this study was to investigate the effect of combining radiation with ibuprofen on expression of p75NTR in human (U87, U251) and murine (GL261) glioma cells, and link to radiosensitivity, migration and invasion, and angiogenesis. Methods: We determined radiosensitivity using a clonogenic assay of glioma cells, including clones that were transfected to stably overexpress p75NTR. Glioma cells transfected with empty vector (pcDNA) were used as a control. Glioma migration and invasion were determined, respectively, by a wound scratch assay and Matrigel-Boyden chamber assay. Expression levels of p75NTR and VEGF165 were determined by Western blot analysis. Results: Ibuprofen increased the radiosensitivity of glioma cells as evidenced by a decreased survival fraction in the clonogenic assay. U87+p75NTR demonstrated increased radiosensitivity compared to control (U87pcDNA). As expected, U87+p75NTR U251+p75NTR were highly invasive and migratory compared to U87pcDNA and U251pcDNA. At a dose of 10 Gy, migration was significantly inhibited (P=0.02) in pcDNA cells only. Induction of p75NTR with ibuprofen correlated to increased radiosensitivity of glioma cells. Paradoxically we found that increased expression of p75NTR by ibuprofen correlated to a reduction of invasion and migration. In addition, expression of VEGF was lower in U87+p75 compared to U87pcDNA. When U87+p75 was treated with ibuprofen alone, VEGF was undetectable, when treated with radiation alone VEGF levels were lower than control but detected, and no VEGF was detectable when the cells were treated with both ibuprofen and radiation. In contrast, expression of VEGF was increased when p75pcDNA glioma cells were treated with ibuprofen, and further increased when treated with radiation. However, adding ibuprofen and radiation resulted in undetectable VEGF. Conclusion: Our results suggest that ibuprofen could be useful clinically as a radiosensitizer and/or an agent to inhibit glioma invasion, migration and angiogenesis. Furthermore, our preliminary data suggest that there may be a “VEGF-switch” modulated by p75NTR status. The VEGF-p75NTR link could be important to drug discovery and translation to clinical control of the glioma malignant phenotype. (Supported by Dept of Defense grant USAMRAA -RX4301803, The Greg Wohrle Fund of the FBTA, the Moffitt Cancer Center Foundation, The Ben and Catherine Ivy Foundation). 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 5271.