Abstract 196: Functional role of death-associated protein 3 in high grade gliomas of childhood

Abstract

Abstract Background: High grade gliomas (HGG) are highly invasive tumors and respond poorly to conventional treatments. Although significant progress has been made in understanding the molecular pathways that lead to the development of HGG in adults, comparatively few data is available for gliomas of childhood. The death-associated protein 3 (DAP3) is localized on the chromosomal region 1q21-22 that has been previously described as a region of frequent chromosomal gain associated with poor outcome in HGG. Moreover, DAP3 has been reported to be overexpressed and to play anti-apoptotic role in invasive glioblastoma cells. Methods: In the current study to investigate the functional role of DAP3 in pediatric versus adult HGG, we suppressed the endogenous DAP3 protein using DAP3-specific short hairpin RNA (shRNA) or chemical inhibitors of protein kinase C, and analyzed the phenotypic effect on glioma cell proliferation, migration, mitochondrial morphology and apoptosis. Results: We found that knockdown of DAP3 by shRNA induced mitochondrial fragmentation and apoptosis in pediatric glioma cell lines while in adult glioma cell lines it suppressed cell proliferation and reduced mitochondrial potential without inducing mitochondrial fragmentation. Specific chemical inhibition of the two classical PKC isoforms (PKCα and PKCβ) significantly reduced the expression of DAP3 protein in both pediatric and adult glioma cell lines. The inhibition of PKCα changed cell morphology, mitochondrial status and significantly suppressed proliferation and migration of both pediatric and adult glioma cell lines without associated caspase activation indicating that DAP3 may mediate nonapoptotic form of cell death in HGG. The suppression of PKCβ rendered pediatric glioma cells more sensitive to the apoptotic effect of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) through a caspase-dependent process as compared with adult glioma cells suggesting a possible implication of DAP3 in intrinsic and extrinsic pathways for apoptosis in pediatric HGG. Conclusion: Our findings confirmed the anti-apoptotic role of DAP3 in glioma cell biology suggesting that specific PKC isoforms mediated the DAP3 suppression of apoptosis in HGG and pointed out the specific functional role of this protein in mitochondrial maintenance. DAP3 may represent a novel target for the treatment of gliomas. 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 196. doi:10.1158/1538-7445.AM2011-196