Neuropilin-1 (NRP-1) upregulated by IL-6/STAT3 signaling contributes to invasion in pancreatic neuroendocrine neoplasms

Although the upregulation of Neuropilin-1 (NRP-1) is associated with many solid tumors, its role in pancreatic neuroendocrine neoplasms (pNEN) has not been well elucidated. The aim of this study was to investigate the role of NRP-1 in improving treatment and determining the prognosis of pNEN. In this study, the expression of NRP-1 in pNEN tissue samples and pNEN cell line BON1 was analyzed by Western blot, polymerase chain reaction (PCR) and immunocytochemistry upon exposure to interleukin-6 (IL-6). Additionally, pNEN cell line BON1 was transfected with small interfering RNAs against NRP-1 or signal transducer and activator of transcription 3 (STAT3) and assessed by in vitro invasion assays. The expression of NRP-1 in pNEN tissues was markedly increased compared with adjacent normal pancreatic tissues. High NRP-1 expression was strongly correlated with tumor grades (P = .026), lymph node metastasis (P = .025), and tumor-node-metastasis stages (P = .012). Furthermore, NRP-1 downregulation notably inhibited the metastatic capacity of pNEN cells, and STAT3 knockdown was found to downregulate the expression of NRP-1. BON1 cells upregulated NRP-1 expression upon stimulation with IL-6. This was accompanied by activation/phosphorylation of the AKT and STAT3 signaling pathways. Western blot of extracts of human pNENs confirmed increased NRP-1 expression, as well as AKT/STAT3 phosphorylation in tissue of pNENs with elevated expression levels of IL-6. In conclusion, our findings suggest that NRP-1 is upregulated in pNEN and is correlated with the metastatic capacity of pNEN cells, potentially via interaction with the IL-6/STAT3 signaling pathway.