Abstract C5: T11TS arrests angiogenic signaling in malignant glioma by attenuating brain endothelial cell angiopoietin-1/Tie2 expression and inducing apoptosis in glioma associated brain endothelial cells.
Authors: Bhattacharya Debanjan , Chaudhuri Swapna 
Published: August 2014

Malignant gliomas are highly aggressive primary brain tumors resistant to conventional treatments mainly because of sustained uncontrolled angiogenesis. Limited efficacies of currently available treatments necessitate development of multi-level targeted anti-angiogenic therapy for treatment of malignant glioma. Previously we reported that sheep erythrocyte membrane glycopeptide T11 target structure (T11TS) therapy in a rodent glioma model inhibits brain endothelial cell VEGF signaling and downstream PI3K/Akt/eNOS pathway. The angiopoietin-1/Tie2 signaling operative in brain endothelial cells is implicated in glioma angiogenesis but the role of T11TS therapy on pro-angiogenic Ang-1/Tie2 axis has not been determined yet. Induction of endothelial cell apoptosis is a common mechanism of action of many anti-angiogenic agents that restrict tumor progression. The purpose of the present study is to investigate the effect of T11TS therapy in regulation of angiopoietin-1/Tie2 signaling in glioma associated brain endothelial cells and to identify whether T11TS therapy triggers apoptosis in glioma associated brain endothelial cells. Additionally, the study evaluated the apoptotic pathways and proteins involved in T11TS induced apoptosis of brain endothelial cells. Primary brain endothelial cells isolated from the cerebral cortices of glioma induced rats before and after T11TS therapy were used for experiments. Expression of angiopoietin-1, Tie2, phospho-Tie2, and apoptotic pathway regulator proteins and caspases in brain endothelial cells were determined by flowcytometry, immunoblotting, immunofluorescent imaging, and immunohistochemical staining of rat cerebral sections. Flow cytometric Annexin V-PI assay and JC-1 assay were employed for detection of apoptosis in glioma associated brain endothelial cells. Our findings revealed that T11TS therapy significantly downregulates angiopoietin-1 and Tie2 receptor expression and activation in glioma associated brain endothelial cells. T11TS therapy induced apoptotic death of glioma associated brain endothelial cells as evidenced from membrane phosphatidylserine translocation and reduction of mitochondrial membrane potential. T11TS therapy stimulated both mitochondrial and extrinsic pathways of apoptosis by activating caspases 9, 3, and 8, triggering cleavage of Bid and modulating expression of apoptotic regulator proteins like p53, Bax, Bcl-2, Fas, and FasL in brain endothelial cells.

Blockage of Ang-1/Tie2 signaling in brain endothelial cells and induction of intrinsic and extrinsic pathway mediated apoptosis in glioma associated brain endothelial cells are the underlying mechanistic events contributing to the anti-angiogenic action of T11TS therapy in malignant glioma.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C5.

Citation Format: Debanjan Bhattacharya, Swapna Chaudhuri. T11TS arrests angiogenic signaling in malignant glioma by attenuating brain endothelial cell angiopoietin-1/Tie2 expression and inducing apoptosis in glioma associated brain endothelial cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C5.