Abstract B5: A BMP7 variant inhibits angiogenesis in vitro and in vivo in part by downregulating VEGFR2 and FGFR1 expression in endothelial cells.

Abstract

Abstract Glioblastoma multiforme (GBM), the most aggressive glioma, requires active angiogenesis for growth and survival. Bone morphogenetic proteins (BMPs), members of the TGF-β superfamily, have numerous biological activities including control of growth, differentiation, and vascular development. Previously, we demonstrated the use of a BMP7 variant (BMP7v) to differentiate glioblastoma stem-like cells (GSLCs) and significantly reduce their tumorigenic potential (Tate and Pallini et al. 2012). Using an in vitro co-culture endothelial cord formation assay, a surrogate of angiogenesis, and its cognate in vivo model, we investigated the role of BMP7v in VEGF, basic FGF (bFGF), tumor-driven angiogenesis. Furthermore, we explored the effect of BMP7v on angiogenesis in GSLC Matrigel plugs to further establish the relevance of the BMP7 effect in a pathological setting. BMP7v treatment resulted in disruption of neo-endothelial cord formation and regression of existing bFGF established cords in vitro. In addition, pre-treatment of endothelial cells with BMP7v led to a significant reduction in their cord forming ability, indicating a direct effect of BMP7v on endothelial cell function. While BMP7v activated the canonical Smad signaling pathway in endothelial cells, targeted gene knockdown using shRNA directed against Smad 4 suggested this pathway is not required to mediate the anti-angiogenic effect of BMP7v. BMP7v decreased endothelial cell migration and down regulated expression of the receptor tyrosine kinases involved in VEGF and FGF angiogenic signaling, VEGFR2 and FGFR1, respectively. Importantly, in an in vivo angiogenic plug assay that serves as a measurement of functional angiogenesis, BMP7v significantly decreased hemoglobin content. In addition, BMP7v significantly decreased angiogenesis in GSLC Matrigel plugs indicating efficacy in a more relevant cancer setting. These data support BMP7v as a potent anti-angiogenic molecule, and the reduction in GSLC tumorigenicity may be due in part to reduced angiogenesis upon BMP7v treatment. Future experiments will attempt to further define the mechanism underlying BMP7v's anti-angiogenic effect. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B5. Citation Format: Courtney Tate, Jacquelyn McEntire, Roberto Pallini, Lisa Wyss, Wayne Blosser, Eliza Vakana, Giorgio D'Alessandris, Liliana Morgante, Stefano Giannetti, Luigi Larocca, Giorgio Stassi, Antonina Benfante, Maria Colorito, Ruggero De Maria, Scott Rowlinson, Louis Stancato. A BMP7 variant inhibits angiogenesis in vitro and in vivo in part by downregulating VEGFR2 and FGFR1 expression in 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 B5.