An Inhibitory Ligand of Neuropilin 2 Blocks Pancreatic Cancer Progression and Impedes Tumor Angiogenesis

Abstract

The proliferation and branching pattern of blood vessels and nerves is mediated during development, in part, by the interaction between the Neuropilin‐2 (NRP2) receptor and its endogenous secreted ligand, Semaphorin‐3F (SEMA3F). This interaction induces a repulsive signal, which participates in the guidance of both neuronal axons and blood vessels (veins and capillaries). Furthermore, upon binding vascular endothelial growth factor‐A (VEGFA), NRP2 forms a complex with the VEGF Receptor‐2 (VEGFR2), which mediates a potent pro‐angiogenic signal. Although NRP2 expression is dormant in adult endothelial tissue, its expression is upregulated in a variety of physiological and pathological conditions. Interestingly, pancreatic ductal adenocarcinoma (PDAC) induces the over‐expression of NRP2 in endothelial cells and in the pancreatic cancer cells themselves. Consequently, this project is aimed at studying the anti‐angiogenic and repulsive effects of SEMA3F in order to inhibit the growth of the primary tumor and the incidence of liver metastases, respectively, in PDAC. Our preclinical trials utilized an orthotopic, syngeneic luciferase‐labelled mouse pancreatic cancer xenograft model in C57BL/6J mice. The delivery of SEMA3F was performed through a systemic intravenous injection of SEMA3F‐encoding adenovirus. Next, we performed a series of three independent preclinical trials, in which we compared the disease progression of PDAC in SEMA3F‐virus treated mice (n=5) compared to control‐virus treated mice (n=5). In the Prevention Trial, the mice received the virus injection three days prior to receiving the PDAC implantation. The Experimental Prevention Trial followed the same timeline, but the PDAC cells were injected into the spleen in order to accelerate the incidence of liver metastases. Lastly, in the Intervention Trial the SEMA3F‐encoding virus was injected after PDAC tumors were established in order to simulate a more realistic clinical setting. Tumorigenicity was monitored during the trials via bioluminescence imaging following systemic luciferin injection. Mice were euthanized and necropsied 20 days after tumor injection, and livers and pancreata were weighed to asses primary tumor growth as well as metastatic burden. Furthermore, the tumors were stained with antibodies directed against CD31 and KI67, in order to quantify tissue microvessel density and cell proliferation respectively. Qualitative analysis of the livers consisted in staining them with antibodies directed against PDX1 and NRP2, in order to confirm that the metastases are of pancreatic origin and that they retain their NRP2 expression after migrating to the liver. Our results indicate a potent anti‐angiogenic effect of SEMA3F compared to control across all experimental groups. Furthermore, a reduced incidence of metastases to the liver supports the chemorepulsive effects of SEMA3F. Overall, SEMA3F shows great potential as a novel therapy in PDAC.Support or Funding InformationNIH CA155728This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.