Abstract 5004: NG2 upregulation and its defective asymmetric distribution in pediatric brainstem glioma and diffuse intrinsic pontine glioma.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Introduction: Pediatric brainstem glioma (BSG) is one of the most difficult cancers to treat accounting for 10-20% of all pediatric central nervous system (CNS) tumors. BSGs may occur throughout the brainstem and are categorized into two main groups: diffuse intrinsic pontine gliomas (DIPGs) and focal brainstem gliomas. DIPGs represent about 80% of BSG and have a peak onset of six to nine years of age. DIPGs invade throughout the pons and may spread to other portions of brainstem. To better understand the pathophysiology of the disease, a genetically engineered (PDGFα-expressing) BSG mouse and a xenograft model have been established. Results: We recently reported proteome profiling of DIPG CSF and formalin fixed specimens. To expand our molecular studies of the disease, we generated complete protein profiles of specimens obtained from BSG mouse tumor and aged-matched healthy controls. Neuroglia 2 (NG2), also known as chondroitine sulfate proteoglycan 4 (CSPG4) was selected for further analysis based on its exclusive expression in BSG specimens. Although NG2 has been previously implicated in adult gliomas, its role in pediatric gliomas has not been investigated and currently there are no publications on the role of NG2 in DIPGs. Recently, NG2 expression has been shown to play a significant role in neoplastic transformation of glioma precursor cells. Gliomas are thought to originate from cells including astrocytes, stem cells, and glioma progenitor cells. Glial progenitor cells are specifically important since several groups have reported detection of oligodendrocyte markers including NG2, PDGFRα, and Olig-2 in gliomas. Our preliminary data shows high expression of NG2 in murine model of brainstem glioma as well as 80% of pediatric DIPG specimens tested. We show that shRNA-mediated knockdown of NG2 reduces cellular migration in vitro. NG2 expression is defective (symmetric) in dividing cells in vitro and in vivo. The defective NG2 expression is consistent with a recent observation in adult high grade gliomas. Injection of NG2 expressing neurospheres (NS) into brainstems of 2 day old mice (P2) results in highly aggressive brainstem tumors resulting in death within 3-7 weeks post-injection. Therefore the NS injected mouse model of brainstem glioma provides a solid model for testing therapeutics and evaluating interventions. Furthermore, we show selective delivery of liposomal nanoparticles to brainstem of our robust BSG mouse model. We also show that nanoparticle-mediated delivery of doxorubicin will induce apoptosis in tumor and not the adjacent normal region. Conclusion: We introduce a robust murine model of brainstem glioma that is developed using NG2 expressing cells. High expression of NG2 in a subset of DIPGs and its defective expression may provide novel approaches for treating DIPGs and BSGs. Citation Format: Sridevi Yadavilli, Madhuri Kambhampati, Oren J. Becher, Tobey MacDonald, Ravi Bellamkonda, Roger J. Paker, Javad Nazarian. NG2 upregulation and its defective asymmetric distribution in pediatric brainstem glioma and diffuse intrinsic pontine glioma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5004. doi:10.1158/1538-7445.AM2013-5004