Blocking SDF-1α/CXCR4 Downregulates PDGF-B and Inhibits Bone Marrow–Derived Pericyte Differentiation and Tumor Vascular Expansion in Ewing Tumors

Abstract

Bone marrow cells (BMCs) are critical to the expansion of the tumor vessel network that supports Ewing’s sarcoma growth. BMCs migrate to the tumor and differentiate into endothelial cells and pericytes. We recently demonstrated that stromal derived growth factor 1α (SDF-1α) regulates platelet derived growth factor B (PDGF-B) and that this pathway plays a critical role in BM-derived pericyte differentiation in vitro. We investigated the role of SDF-1α/PDGF-B in the tumor microenvironment in vivo in promoting BM-derived pericyte differentiation in Ewing’s tumors. The CXCR4 antagonist, AMD 3100, was used to disrupt the SDF-1α/CXCR4 axis in vivo in two xenograft Ewing’s tumor models. BMCs from green fluorescent protein (GFP+) transgenic mice were transplanted into lethally irradiated nude mice in order to track BMC migration to the tumor site. Following BMC engraftment, tumor-bearing mice received daily subcutaneous injections of either PBS or AMD 3100 for 3 weeks. Tumors were resected, and tumor sections were analyzed by immunohistochemistry. AMD 3100 inhibited BMC differentiation into desmin+ and NG2+ pericytes, affected the morphology of the tumor vasculature, decreased perfusion, and increased tumor cell apoptosis. We observed smaller vessels with tiny lumens and a decrease in the microvessel density. AMD 3100 also inhibited PDGF-B protein expression in vitro and in vivo. SDF-1α in the tumor microenvironment plays a critical role in promoting pericyte formation and Ewing’s sarcoma tumor neovascularization by regulating PDGF-B expression. Interfering with this pathway affects tumor vascular morphology and expansion.

CXCL14, CXCR7 expression and CXCR4 splice variant ratio associate with survival and metastases in Ewing sarcoma patients

“…Hence, CXCR4 signalling is a potential targetable pathway and inhibition of CXCR4 signalling in EWS in vitro and in xenografts has already been shown to reduce tumour migration growth and angiogenesis [15,27,35]. Potential drugs to treat EWS are; CXCL12 neutralising ligands, like chalcone 4, CXCR4 antagonists, like AMD3100 and CXCL14 analogues (Fig.…”

Twenty Years on: What Do We Really Know about Ewing Sarcoma and What Is the Path Forward?

“…109 CXCR4 expression has previously been associated with ES metastatic disease in patient samples, 110 and with ES angiogenesis. 111 However, links to metastasis have been disputed by others. 112 …”

Platelet‐derived growth factor (PDGF) signalling in cancer: rapidly emerging signalling landscape

“…CXCR4 antagonist AMD 3100 also considerably inhibited BMCs differentiation and induced apoptosis in xenografted mice. 54 Platelet-derived growth factor-R inhibitor nilotinib has recently been tested for efficacy in an orthotopic mouse model of human colon cancer and a model of liver metastasis. Results revealed that stromal reaction of xenografts growing in the cecal wall and liver was significantly decreased when individually treated with nilotinib.…”

“…Mice Intratumorally injected with SDF‐1 α gene expressing adenoviral vector displayed a marked increase in BM‐derived pericytes surrounding the tumour vessels. CXCR4 antagonist AMD 3100 also considerably inhibited BMCs differentiation and induced apoptosis in xenografted mice …”