Abstract 2526: Regulation of angiogenic factors in glioblastoma progression

Abstract

Abstract Background & Purpose: Glioblastoma is the most malignant primary brain tumor in humans and has a very low survival rate. The aggressiveness of this cancer can be attributed to the presence of glioblastoma stem cells (GSC), which are highly invasive and therapy resistant. Increased aggressiveness of GSCs is attributed to the release of angiogenic factors, which promotes the formation of new blood vessels that enhances tumor cell survival and proliferation. The neovascularization also provides a scaffold for tumor cells to migrate, enabling metastasis. Therefore, identifying the altered expression of angiogenic factors is of clinical importance. In this study, we examined the changes in the expression of pro-angiogenic factors in GSCs as compared to the original tumor from which they were derived. We also determined if differentiation of GSC towards a less invasive phenotype decreased the levels of these pro-angiogenic factors. Methods: GBM tumor cells were grown in complete media containing 10% Fetal Calf Serum (FCS) and GSCs were grown in media containing B27, heparin, EGF, and FGF. GSCs were differentiated by growing them in media containing 10% FCS and B27 with vitamin A, for about one week. We examined the expression of a panel of pro-angiogenic factors in GSCs (33-GSC) and in the original tumor cells (33-T) from which GSCs were derived. We then examined if differentiation of 33-GSC decreased the levels of these pro-angiogenic factors. Changes in protein levels were evaluated by immunofluorescence staining. The mRNA levels were quantitated using real time Q-PCR. Results: Immunofluorescence staining showed that the GSCs express higher levels of pro-angiogenic factors examined (11 out of 16). GSCs were successfully differentiated into astrocytes as indicated by morphology and GFAP expression. The differentiation of GSCs into astrocytes was sufficient to cause decreased expression of VEGF and c-MYC. Our data showed 27 fold increase in VEGF mRNA levels, 63 fold increase in MMP2 mRNA levels, 11 fold increase in MMP9 mRNA levels, and 2 fold increase in c-MYC mRNA levels in GSCs compared to the tumor line, indicating the regulation of these pro-angiogenic factors at transcriptional level. Conclusions: Increased expression of pro-angiogenic factors in GSCs may render these cells to be more aggressive and invasive, and suggests that differential expression of angiogenic factors in GSC cells may play an important role in the GBM progression, and therapy resistance. Citation Format: Carolina Larrain, Umadevi V. Wesley, Paul Clark, John S. Kuo, Robert Dempsey. Regulation of angiogenic factors in glioblastoma progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2526.