CXC-chemokine/CXCR2 biological axis promotes angiogenesis in vitro and in vivo in pancreatic cancer

Angiogenesis is essential for tumor growth and metastasis. Although ELR⁺-CXC-chemokines and their corresponding receptor, CXC-receptor 2 (CXCR2), are known mediators of angiogenesis, little is known about their role in pancreatic cancer (PaCa). The aim of our study was to determine the role of ELR⁺-CXCchemokine/ CXCR2 biological axis in promoting PaCa angiogenesis. We prospectively collected secretin-stimulated exocrine pancreatic secretions (SSEPS) from normal individuals (NP) and PaCa patients. We showed that summed concentrations of ELR⁺-CXC-chemokines in SSEPS from PaCa patients were significantly higher than in those from NP (p = 0.002). We measured ELR⁺-CXC-chemokine levels in supernatants from multiple PaCa cell lines and confirmed that BxPC-3, Colo-357 and Panc-28 had significantly higher expression compared with an immortalized human pancreatic ductal epithelial (HPDE) cell line. After confirming lack of autocrine effects of ELR1-CXC-chemokines on PaCa cells (due to absence of CXCR2 expression), we investigated paracrine effects of these chemokines on human umbilical vein endothelial cells (HUVEC). Both recombinant ELR⁺-CXC-chemokines and co-culturing with BxPC-3 significantly enhanced proliferation, invasion, and tube formation of HUVEC (p < 0.05). These biological effects were significantly inhibited by treatment with a neutralizing antibody against CXCR2 (anti-CXCR2 Ab) (p < 0.05). Finally, anti-CXCR2 Ab significantly reduced tumor volume (p < 0.05), Ki-67 proliferation index (p = 0.043) and Factor VIII⁺ microvessel density (p = 0.004) in an orthotopic nude mouse PaCa model. Our results show that ELR⁺-CXC-chemokines promote PaCa tumor-associated angiogenesis through CXCR2, suggesting that CXCR2 is an anti-angiogenic target in PaCa.