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Effects of GSK3beta inhibition on the formation of invadopodium-like microstructures and matrix degradation by U251 cells.

Source and working dilutions of the primary antibodies used for Western blotting, immunofluorescence and immunohistochemical staining and pull-down assay.

Putative molecular pathway through which GSK3beta promotes glioblastoma cell migration and invasion.

Effect of GSK3beta inhibition on phosphorylation of glycogen synthase in a mouse model of glioblastoma.

Effect of GSK3beta RNA interference on migration and invasion of glioblastoma cells.

Sequence of the primers for quantitative RT-PCR.

ffect of GSK3beta inhibition on morphology, subcellular localization of F-actin and Rac1 and lamellipodia formation in glioblastoma cells.

Effect of GSK3beta inhibition on expression of ECT2, Vav3 and integrins mRNA in glioblastoma cells.

Purpose: Glioblastoma represents the malignant brain tumor that is most refractory to treatment and in which the identification of molecular target(s) is urgently required. We investigated the expression, activity, and putative pathologic role of glycogen synthase kinase 3β (GSK3β), an emerging therapeutic target for neurodegenerative diseases, in human glioblastoma.Experimental Design: The active fraction of GSK3β that is phosphorylated at the tyrosine 216 residue (pGSK3βY216) was identified in glioblastoma cell lines. GSK3β activity for phosphorylating its substrate was detected in these cells by nonradioisotopic in vitro kinase assay.Results: Higher expression levels of GSK3β and pGSK3βY216 were frequently detected in glioblastomas compared with nonneoplastic brain tissues. Inhibition of GSK3β activity by escalating doses of a small-molecule inhibitor (AR-A014418) or inhibition of its expression by RNA interference induced the apoptosis and attenuated the survival and proliferation of glioblastoma cells in vitro. Inhibition of GSK3β was associated with increased expression of p53 and p21 in glioblastoma cells with wild-type p53 and with decreased Rb phosphorylation and expression of cyclin-dependent kinase 6 in all glioblastoma cell lines. Administration of AR-A014418 at a low dose significantly sensitized glioblastoma cells to temozolomide and 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea, chemotherapeutic agents used in the clinical setting, as well as to ionizing radiation.Conclusion: These results indicate that GSK3β exerts a pathologic role by promoting the survival and proliferation of glioblastoma cells and by protecting them from apoptosis via the inactivation of p53- and/or Rb-mediated pathways. Consequently, we propose that GSK3β provides a potential therapeutic target in glioblastoma.

Supplementary Data from Potential Therapeutic Effect of Glycogen Synthase Kinase 3β Inhibition against Human Glioblastoma

The failure of current treatment options for glioblastoma stems from their inability to control tumor cell proliferation and invasion. Biologically targeted therapies offer great hope and one promising target is glycogen synthase kinase-3β (GSK3β), implicated in various diseases, including cancer. We previously reported that inhibition of GSK3β compromises the survival and proliferation of glioblastoma cells, induces their apoptosis, and sensitizes them to temozolomide and radiation. Here, we explore whether GSK3β also contributes to the highly invasive nature of glioblastoma. The effects of GSK3β inhibition on migration and invasion of glioblastoma cells were examined by wound-healing and Transwell assays, as well as in a mouse model of glioblastoma. We also investigated changes in cellular microarchitectures, cytoskeletal components, and proteins responsible for cell motility and invasion. Inhibition of GSK3β attenuated the migration and invasion of glioblastoma cells in vitro and that of tumor cells in a mouse model of glioblastoma. These effects were associated with suppression of the molecular axis involving focal adhesion kinase, guanine nucleotide exchange factors/Rac1 and c-Jun N-terminal kinase. Changes in cellular phenotypes responsible for cell motility and invasion were also observed, including decreased formation of lamellipodia and invadopodium-like microstructures and alterations in the subcellular localization, and activity of Rac1 and F-actin. These changes coincided with decreased expression of matrix metalloproteinases. Our results confirm the potential of GSK3β as an attractive therapeutic target against glioblastoma invasion, thus highlighting a second role in this tumor type in addition to its involvement in chemo- and radioresistance. Mol Cancer Ther; 14(2); 564–74. ©2014 AACR.

Purpose: Glioblastoma represents the malignant brain tumor that is most refractory to treatment and in which the identification of molecular target(s) is urgently required. We investigated the expression, activity, and putative pathologic role of glycogen synthase kinase 3β (GSK3β), an emerging therapeutic target for neurodegenerative diseases, in human glioblastoma. Experimental Design: The active fractionof GSK3β that is phosphorylated at the tyrosine 216 residue (pGSK3βY216) was identified in glioblastoma cell lines. GSK3β activity for phosphorylating its substrate was detected in these cells by nonradioisotopic in vitro kinase assay. Results: Higher expression levels of GSK3β and pGSK3βY216 were frequently detected in glioblastomas compared with nonneoplastic brain tissues. Inhibition of GSK3β activity by escalating doses of a small-molecule inhibitor (AR-A014418) or inhibition of its expression by RNA interference induced the apoptosis and attenuated the survival and proliferation of glioblastoma cells in vitro. Inhibition of GSK3β was associated with increased expression of p53 and p21 in glioblastoma cells with wild-type p53 and with decreased Rb phosphorylation and expression of cyclin-dependent kinase 6 in all glioblastoma cell lines. Administration of AR-A014418 at a low dose significantly sensitized glioblastoma cells to temozolomide and 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea, chemotherapeutic agents used in the clinical setting, as well as to ionizing radiation. Conclusion: These results indicate thatGSK3β exerts a pathologic role by promoting the survival and proliferation of glioblastoma cells and by protecting them from apoptosis via the inactivation of p53- and/or Rb-mediated pathways (Clin Cancer Res 2009;15:887-97). Consequently, we propose that GSK3β provides a potential therapeutic target in glioblastoma (Minamoto T, inventor; National University Corporation Kanazawa University; assignee. Suppression of cancer and method for evaluating anticancer agent based on the effect of inhibiting GSK3β. International patent WO2006/073202. 2006 Jul 13. United States patent US 11/794,716. 2006 Jan 4. European patent EP1845094 2007 Oct 17. Japan patent 2006-550915 2007 Jun 21). 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 1617.