Abstract 3323: Neural stem cells expressing TRAIL as therapeutic modality for treatment of experimental malignant glioma

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Introduction. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising agent with apoptotic activity against cancer cells. However, many of human glioblastoma multiforme (GBM) have been shown to be resistant to treatment with soluble TRAIL. Neural stem cells (NSCs) possess an ability to migrate to the main tumor and its satellites. NSCs engineered to express membrane bound TRAIL (NSC-TRAIL) may help to overcome resistance of glioma cells to soluble TRAIL. Therefore, the aim of this study was to investigate if treatment with NSCs-TRAIL is a feasible therapeutic approach for experimental glioma alone or in combination with proteasome inhibitors. Methods. Full size TRAIL cDNA was cloned from mRNA obtained from Jurkat cells by PCR amplification and subsequently sub-cloned in lentiviral vector. NSCs were modified to express membrane bound TRAIL by infection with lentiviral particles encoding TRAIL. Membrane integrity assay was used to evaluate toxicity of soluble TRAIL and proteasome inhibitors in glioma cells. Immunocytochemistry and flow cytometry were used to analyze apoptosis in glioma cells. Intracranial glioma xenograft model in nude mice was utilized for evaluation of therapeutic properties of NSCs-TRAIL alone or in combination with proteasome inhibitors. Results. Glioma cell lines were resistant to treatment with soluble TRAIL and proteasome inhibitors alone. Sensitivity of glioma cells to TRAIL was significantly increased in combined treatment with proteasome inhibitors in vitro. Up-regulation of TRAIL receptor 2 (DR5) in glioma cells exposed to proteasome inhibitors was recorded in time dependent manner. Co-culture with NSCs-TRAIL alone were able to induce apoptosis in glioma cells. The apoptotic effect of NSCs-TRAIL was magnified by treatment with proteasome inhibitor, bortezomib. Animals, received intracranial injection of glioma cells with NSCs-TRAIL at 1:0.5 and 1:1 ratio demonstrated 20 and 80% survival over 3 month, respectively. The survival of animals was improved to 40% and 100% in control NSCs and NSCs-TRAIL experimental groups which received bortezomib therapy. No up-regulation of DR5 was observed in the tumor samples from animals treated with bortezomib. Mice with established intracranial glial xenografts treated with NSCs-TRAIL alone and in combination with bortezomib showed improvement in survival in comparison with animals bearing tumor alone or injected with control NSCs. Conclusion. This study demonstrates that NSCs expressing membrane bound TRAIL are able to trigger apoptosis in glioma cells in vitro and improve survival of animals in vivo. Treatment of glioma cells with proteasome inhibitors significantly increased their sensitivity to TRAIL in vitro. Proteasome inhibitor, bortezomib, improved survival of animals treated with NSCs but its effect was not specific to the NSCs-TRAIL treated mice. 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 3323. doi:10.1158/1538-7445.AM2011-3323