Effect of neuropilin-2 expression on TGF-β1-epithelial-mesenchymal transition in colorectal cancer cells.

Abstract

414 Background: Initially characterized as neuronal receptors, Neuropilins (NRPs) were also found to be expressed in endothelial cells and subsequently were shown to play a role in the development of the vascular system. NRP family consists of two genes, neuropilin-1 (NRP1) and neuropilin-2 (NRP2).The multiple functions of NRPs were recently highlighted by the identification of NRP role in oncogenesis. In this study, we first confirmed the role of NRP2 in tumor progression. We also extended the understanding of NRP2 oncogenic functions by investigating the ability of NRP2 to orchestrate epithelial-mesenchymal transition (EMT) in colorectal cancer cells. Methods: We have generated human colon cancer cell lines transfected with NRP2 transgene or siRNA to investigate NRP2 involvement in EMT. First, the oncogenic functions of NRP2 were studied in vitro by MTT, soft agar, invasion assays and in vivo using xenografts experiments. Ability of NRP2 to orchestrate EMT was then investigated by flow cytometry, immunohistochemical (IHC) staining, western-blotting and quantitative real-time PCR. Results: IHC staining revealed that NRP2 is expressed in human colon and breast carcinomas while it is not expressed in healthy tissues. Then, we confirmed that NRP2 increases tumor proliferation, colony formation, invasion and xenograft formation. Moreover, NRP2-expressing cells displayed an immunohistochemical phenotype of EMT characterized by the loss of E-Cadherin and an increase of vimentin. Furthermore, NRP2 expression promotes transforming-growth factor-β1 (TGF- β1) signaling, leading to an increased phosphorylation of the Smad2/3 complex in colorectal cancer cell lines. Specific inhibition of NRP2 using siRNA or treatment with specific TGFβRI kinase inhibitors prevented this phosphorylation and the EMT, suggesting that NRP2 cooperates with TGFRI to promote EMT in colorectal carcinoma. Conclusions: Our findings have reinforced the essential role of NRP2 in cancer progression and demonstrated that NRP2 expression confers to tumor cell lines the hallmarks of EMT. Moreover, in the current work, we present evidence for the therapeutic value of NRP2 targeting. No significant financial relationships to disclose.