Abstract 193: Antiangiogenic effect of conditioned media derived from triple negative breast cancer cells in brain microvascular endothelial cells in vitro

Abstract Breast cancer is the most common malignancy among females and is a leading cause of cancer mortality. Brain metastasis is associated with poor prognosis and reduced survival among breast cancer patients. For brain metastasis to occur, cancer cells are required to remain in direct contact with endothelial cells that line brain blood vessels. Data regarding the interaction between brain endothelial cells and breast cancer is limited. The aim of this work was to understand the interaction between breast cancer cells and brain endothelial cells. Human brain microvascular endothelial cells (hBMECs) were treated with conditioned media from MDA-MB-231 cell line and their angiogenic characteristics were evaluated. The involvement of the glycogen synthase kinase-3β (GSK-3β), vascular endothelial growth factor (VEGF), brain derived neurotrophic factor (BDNF), and thrombospondin-1 (TSP-1) was evaluated using release levels and inhibitor-based approaches. Levels of secreted proteins were assayed using ELISA. Results of the study showed that conditioned media from MDA-MB-231 breast cancer cells reduced angiogenic potential of hBMECs. Conditioned media significantly suppressed migration and tube formation of hBMECs compared to control group. In these experiments, control group represents hBMECs which were incubated with regular serum-free RPMI-1640 culture media. Inhibiting GSK-3β in conditioned media-treated hBMECs by its selective inhibitor (SB 216763; 10nM), restored the migratory potential of endothelial cells. In addition, MDA-MB-231 cells released VEGF at a rate that exceeded VEGF release from endothelial cells (6342 vs. 67.6 pg/ml). The release of VEGF from conditioned media-treated hBMECs was not altered by the high levels of VEGF presented in MDA-MB-231 cells conditioned media. GSK-3β inhibition in hBMECs significantly increased VEGF release from endothelial cells by about 1000 pg/ml compared to conditioned media-treated endothelial cells. MDA-MB-231 cells also released high levels of BDNF into the media and treating hBMECs with conditioned media from MDA-MB-231 cells did not alter the endogenous release of total BDNF from endothelial cells. GSK-3β inhibition did not alter BDNF release from endothelial cells. BDNF inhibition using TrkB-Fc (4µg/ml) did not restore the migratory potential of endothelial cells and the anti-angiogenic effect of conditioned media was maintained despite the inhibition of BDNF. Breast cancer cells released high levels of TSP-1 into the media. hBMECs treated with TSP-1 (5µg/ml) reduced wound healing by 40%, an effect that was restored by GSK-3β inhibitor. In conclusion, conditioned media from breast cancer cells induced anti-angiogenic effects in hBMECs which was found to be GSK-3β-dependent. The anti-angiogenic effect was further illustrated in terms of increased TPS-1 levels released by breast cancer cells. Citation Format: Nehad M. Ayoub, Ahmed Alhusban, Laila Alhusban. Antiangiogenic effect of conditioned media derived from triple negative breast cancer cells in brain microvascular endothelial cells in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 193.