Abstract LB-345: Hypoxia-induced reprogramming cause normal glia to mimic tumor-associated glial cells.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Cancer-associated fibroblasts (CAFs) have been shown to foster tumor growth in several solid cancers. In the brain, the stroma is mainly composed of glial cells such as astrocytes and oligodendrocytes whose role in brain tumor-stroma interactions are poorly characterized. We have previously identified a unique gene expression profile of tumor-associated glial cells (TAGs) by fluorescence activated cell sorting (FACS) of glial cells from GFP/Nod Scid mice engrafted with human glioblastoma biopsies. Little is known about the mechanisms mediating these expression changes, but both direct tumor cell-glial cell contact and environmental stress such as hypoxia are external cues that may induce these changes. Thus, we investigated how hypoxia impacted on the phenotype of glial cells from normal mouse brains. Briefly, mouse brains were enzymatically digested to obtain single cell suspensions, and then glial cells were isolated by FACS with simultaneous removal of immune cells (CD11b+) and endothelial cells (CD31+). These cells were then seeded at a density of 50,000 cells/well in a 48-well plate and incubated under either normoxic (21% oxygen) or hypoxic (0.5% oxygen) conditions for seven days. Notably, glial cells upregulated Sox2, HIF-2a, Nestin and Vimentin in hypoxia compared to normoxic conditions. In addition glial cells also upregulated angiogenic factors such as VEGF, Angiopoietin 2 and FGF2. Furthermore, cell cycle analysis revealed a significantly higher fraction of cycling cells in hypoxia than in normoxia. To investigate how glial cells and tumor cells interact, we made co-cultures of glial cells isolated from DsRed+ mice and GFP-transfected human glioma cells. Fluorescence imaging of the co-cultures show that these two cell types establish cell contacts in vitro, and that the glial cells alter their morphology in co-cultures compared to monocultures of glial cells alone. These changes strongly resembled the changes observed in tumor-associated glial cells, suggesting that hypoxia is a major contributor to the phenotype of tumor-associated glial cells. Furthermore direct physical contact between tumor cells and glial cells may lead to phenotypical changes in the glial cells. Ongoing work aims at further characterizing the TAG population to reveal its cell composition and address the role of various subpopulations of glial host cells. Citation Format: Lina Leiss, Ivana Manini, Marta Calderon, Per Oyvind Enger. Hypoxia-induced reprogramming cause normal glia to mimic tumor-associated glial cells. [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 LB-345. doi:10.1158/1538-7445.AM2013-LB-345