Neuropilin-1 regulated by miR-320 contributes to the growth and metastasis of cholangiocarcinoma cells.

Background & Aims: Neuropilin-1 (NRP-1) activates signalling pathways as multifunctional co-receptors in cancer cells. However, its role and how it is regulated by miRNAs in cholangiocarcinoma (CCA) have not yet been investigated.

Methods: The expression of NRP-1, miR-320 and key molecules involved in cell proliferation, migration and related signalling pathways were detected by immunohistochemistry, immunoblotting and qRT-PCR. Stable transfectants depleted of NRP-1 were generated. The regulatory effect of miR-320 on NRP-1 was evaluated by luciferase reporter assays. Cell proliferation, cell cycle distribution and migration were examined. Xenograft tumour models were established to assess tumourigenesis, tumour growth and lung metastasis.

Results: Cholangiocarcinoma tissues expressed higher levels of NRP-1 than adjacent normal biliary tissues, and its expression negatively correlated with miR-320. NRP-1 depletion inhibited cell proliferation and induced cell cycle arrest in the G1/S phase by upregulating p27, and downregulating cyclin E and cyclin-dependent kinase 2; and reduced cell migration by inhibiting the phosphorylation of focal adhesion kinase. NRP-1 depletion suppressed tumourigenesis, tumour growth and lung metastasis by inhibiting cell proliferation and tumour angiogenesis in experimental animals. Depletion of NRP-1 inhibited the activation of VEGF/VEGFR2, EGF/EGFR and HGF/c-Met pathways stimulated by respective ligands. MiR-320 negatively regulated the expression of NRP-1 by binding to the 3'-UTR of NRP-1 promoter, and miR-320 mimics inhibited cell proliferation and migration, and the growth of established tumours in animals by downregulating NRP-1.

Conclusions: The present results indicate that NRP-1 is negatively regulated by miR-320, and both of them may be potentially therapeutic targets for CCA.