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Background Angiogenesis is a critical step in the growth of pancreatic neuroendocrine tumors (PNETs) and may be a selective target for PNET therapy. However, PNETs are robustly resistant to current anti-angiogenic therapies that primarily target the VEGFR pathway. Thus, the mechanism of PNET angiogenesis urgently needs to be clarified. Methods Dataset analysis was used to identify angiogenesis-related genes in PNETs. Immunohistochemistry was performed to determine the relationship among Neuropilin 2 (NRP2), VEGFR2 and CD31. Cell proliferation, wound-healing and tube formation assays were performed to clarify the function of NRP2 in angiogenesis. The mechanism involved in NRP2-induced angiogenesis was detected by constructing plasmids with mutant variants and performing Western blot, and immunofluorescence assays. A mouse model was used to evaluate the effect of the NRP2 antibody in vivo, and clinical data were collected from patient records to verify the association between NRP2 and patient prognosis. Results NRP2, a VEGFR2 co-receptor, was positively correlated with vascularity but not with VEGFR2 in PNET tissues. NRP2 promoted the migration of human umbilical vein endothelial cells (HUVECs) cultured in the presence of conditioned medium PNET cells via a VEGF/VEGFR2-independent pathway. Moreover, NRP2 induced F-actin polymerization by activating the actin-binding protein cofilin. Cofilin phosphatase slingshot-1 (SSH1) was highly expressed in NRP2-activating cofilin, and silencing SSH1 ameliorated NRP2-activated HUVEC migration and F-actin polymerization. Furthermore, blocking NRP2 in vivo suppressed PNET angiogenesis and tumor growth. Finally, elevated NRP2 expression was associated with poor prognosis in PNET patients. Conclusion Vascular NRP2 promotes PNET angiogenesis by activating the SSH1/cofilin/actin axis. Our findings demonstrate that NRP2 is an important regulator of angiogenesis and a potential therapeutic target of anti-angiogenesis therapy for PNET.

Background Angiogenesis is a critical step in pancreatic neuroendocrine tumour (PNET) growth and may be a selective target for PNET therapy. However, PNET is robustly resistant to current antiangiogenic therapies which primarily target the VEGFR pathway. Thus, PNET angiogenesis mechanism was urgently to be clarified. Methods Dataset analysis was used to identify PNET angiogenesis related genes. Immunohistochemistry was performed to determine relation among Neuropilin 2 (NRP2), VEGFR2 and CD31. Cell proliferation, wound-healing and tube formation assay were investigated to clarify the function of NRP2 in angiogenesis. The mechanism involved in NRP2 inducing angiogenesis was detected by mutant construction, Western blot, and immunofluorescence assay. In vivo, mice model was performed to evaluate the effect of NRP2 antibody, and clinical data was recruited to verify association between NRP2 and patients prognosis. Results NRP2, a VEGFR2 co-receptor, positively correlated with vascularity rather than with VEGFR2 in PNET tissues. NRP2 promoted PNET cell medium-treated HUVEC cell migration via a VEGF/VEGFR2-independent pathway. Moreover, NRP2 induced F-actin polymerization by activating the actin-binding protein cofilin. Mechanistically, cofilin phosphatase slingshot-1 (SSH1) was highly expressed involved in NRP2-activating cofilin. Silencing SSH1 rescued NRP2-activated HUVEC cell migration and F-actin polymerization. Furthermore, blocking NRP2 in vivo suppressed PNET angiogenesis and tumour growth. High NRP2 expression was associated with poor prognosis in PNET patients. Conclusion Vascular NRP2 promotes PNET angiogenesis via activating SSH1/cofilin/actin axis. Our findings demonstrate NRP2 to be an important regulator of angiogenesis and potential therapeutic target of anti-angiogenesis therapy for PNET.