A Small Interfering RNA Targeting Vascular Endothelial Growth Factor Inhibits Ewing's Sarcoma Growth in a Xenograft Mouse Model

Abstract

Angiogenesis plays an essential role in tumor growth and metastasis and is a promising therapeutic target for cancer. Vascular endothelial growth factor (VEGF) is a key regulator in vasculogenesis as well as in angiogenesis.TC71human Ewing's sarcoma cells overexpressVEGF, with a shift in isoform production from membrane-bound VEGF 189 to the more soluble VEGF 165 . Transfection of TC71cells with a vector-based VEGF targeted small interfering RNA expression system (VEGFsi) inhibited VEGF 165 expression by 80% and VEGF 165 protein production by 98%, with no alteration in VEGF 189 expression. Human microvascular endothelial cell proliferation and migration induced by conditioned medium from VEGFsi-transfected TC71 cells was significantly less than that induced by conditioned medium fromTC71cells and control vector-transfected TC71cells. Furthermore, after s.c. injection into athymic nu/nu mice, the tumor growth of VEGFsi-expressingTC71 cells was significantly less than that of parental or control vector-transfected cells.Vessel density as assessed by CD31 immunohistochemical analysis and VEGF 165 expression as assessed by Northern blotting were also decreased. Intratumor gene therapy with polyethylenimine/VEGFsi also resulted in tumor growth suppression.When inoculated into the tibias of nude mice,VEGFsiexpressingTC71cells induced osteolytic bone lesions that were less severe than those induced by control groups. These data suggest that targeting VEGF 165 may provide a therapeutic option for Ewing's sarcoma.

VEGF165 expression in the tumor microenvironment influences the differentiation of bone marrow-derived pericytes that contribute to the Ewing’s sarcoma vasculature

“…Using the GFP-transplant and i.v. lectin infusion schema described above, we first established that TC/siVEGF 7-1 tumors contained small, discontinuous lectin-marked vessels, which was consistent with our previous findings [2,3]. Despite this disruption in vessel size/morphology, multiple areas contained clusters of BM-derived cells surrounding perfused tumor vessels (Fig.…”

“…To determine whether the migration of Tie2 − BM cells into Ewing's tumors and their subsequent differentiation into Tie2 + vascular smooth muscle cells was specifically mediated by VEGF 165 within the tumor microenvironment, we repeated all of the above experiments using a VEGF 165 siRNA-inhibited TC71 clone (TC/siVEGF 7-1 ) [3]. Using the GFP-transplant and i.v.…”

“…We previously demonstrated that bone marrow (BM) cells participate in the formation of blood vessels that support the growth of Ewing's sarcoma tumors [1,2]. We further demonstrated that BM cells that migrate into Ewing's sarcoma tumors differentiate into endothelial cells that colocalize with these blood vessels and that this process is controlled by vascular endothelial growth factor 165 (VEGF 165 ) [1][2][3]. Others have also shown direct incorporation of BMderived endothelial progenitor cells into the expanding vascular networks that are essential for tumor growth [4][5][6].…”

Experimental anti‐angiogenesis causes upregulation of genes associated with poor survival in glioblastoma

“…Knock down of VEGF by RNA interference (RNAi) strongly slow tumor growth and angiogenesis of in various animal tumor models. 7,[13][14][15][16][17] We have previously shown that U87 glioma cells deposited on the chick chorio-allantoic membrane (CAM) form highly vascularized tumors in a VEGF-dependent manner, and recapitulate key features of glioblastoma in patients on a morphological and molecular level. 18 To generate a defined anti-angiogenic in vivo environment we transfected U87 glioma cells with short-interfering RNAs (siRNAs) targeting all isoforms of VEGF-A and implanted them on the CAM.…”

siRNA-mediated knockdown of VEGF-A, VEGF-C and VEGFR-3 suppresses the growth and metastasis of mouse bladder carcinoma in vivo

“…previous studies have demonstrated that VEGF-c-targeting rnai effectively suppresses the lymphatic metastasis of human breast cancer cells (17) and that, by inhibiting angiogenesis, VEGF-targeted rnai suppresses retinoblastoma and Ewing's sarcoma (18,19). in this study, we designed and selected sirnas targeting VEGF-a, VEGF-c and VEGFr-3, which effectively reduced target gene expression in bladder cancer cells in vitro.…”