Antagonism of Ang-Tie2 and Dll4-Notch signaling has opposing effects on tumor endothelial cell proliferation, evidenced by a new flow cytometry method

Abstract

Sustained angiogenesis is essential for tumor growth as it provides the tumor with a network of blood vessels that supply both oxygen and essential nutrients. Limiting tumor-associated angiogenesis is a proven strategy for the treatment of human cancer. To date, the rapid detection and quantitation of tumor-associated endothelial cell (TAEC) proliferation has been challenging, largely due to the low frequency of endothelial cells (ECs) within the tumor microenvironment. In this report, we address this problem using a new multiparametric flow cytometry method capable of rapid and precise quantitation of proliferation by measuring bromodeoxyuridine (BrdUrd) uptake in mouse TAECs from established human tumor xenografts. We determined the basal proliferation labeling index of TAECs in two human tumor xenografts representing two distinct histologies, COLO 205 (colorectal cancer) and U-87 (glioblastoma). We then investigated the effects of two large-molecule antiangiogenic agents targeting different biochemical pathways. Blocking angiopoietinTie2 signaling with the peptide-Fc fusion protein, trebananib (AMG 386), inhibited proliferation of TAECs, whereas blocking Dll4-Notch signaling with an anti-Dll4-specific antibody induced hyperproliferation of TAECs. These pharmacodynamic studies highlight the sensitivity and utility of this flow cytometry-based method and demonstrate the value of this assay to rapidly assess the in vivo proliferative effects of angiogenesis-targeted agents on both the tumor and the associated vasculature.

<p>The Role of DLLs in Cancer: A Novel Therapeutic Target</p>

“…[60][61][62][63] Increased DLL4/Notch expression in the large and mature vessels of gliomas promotes a quiescent vascular phenotype that reduces the density of the tumor vasculature. 61,[64][65][66] However, DLL4 in some cases is associated with high MVD and is expressed in some microvascular formations of gliomas, including delicate capillary-like, 67,68 garland-like, 68 sprouted and clustered 60,69 and glomeruloid cells. 62,68,69 These findings indicate a complex relationship between DLL4 and tumor angiogenesis.…”

Glioblastoma pharmacotherapy: A multifaceted perspective of conventional and emerging treatments (Review)

“…However, other signalling pathways and effectors may be involved in this type of malignant disease and their discovery would uncover the possibility of novel therapies in the future. The currently available therapy options for GBM (51)(52)(53)(54)(55)(56)(57)(58)(59)(60)(61)(62)(63)(64) are summarised in Table I.…”

Expression of Matrix Metalloproteinase‐9 and CD34 in Giant Cell Tumor of Bone

“…Tumor angiogenesis is closely related to the occurrence, development and prognosis of a variety of tumors. Some researchers reported that vascular endothelial cells can be labeled by lots of factors, such as FSRA/WF, cluster of differentiation (CD)31, CD34, Tie2 and TEC‐11 and so on. The marker CD34 is characterized by high reproducibility and stability in the pan‐vascular endothelial cells that are commonly used for immunohistochemical identification of different tumors.…”