Neuropilin-1 Stimulates Tumor Growth by Increasing Fibronectin Fibril Assembly in the Tumor Microenvironment

Abstract

The tumor microenvironment, including stromal myofibroblasts and associated matrix proteins, regulates cancer cell invasion and proliferation. Here we report that neuropilin-1 (NRP-1) orchestrates communications between myofibroblasts and soluble fibronectin (FN) that promote α5β1 integrin-dependent FN fibril assembly, matrix stiffness, and tumor growth. Tumor growth and FN fibril assembly was reduced by genetic depletion or antibody neutralization of NRP-1 from stromal myofibroblasts in vivo. Mechanistically, the increase in FN fibril assembly required glycosylation of serine 612 of the extracellular domain of NRP-1, an intact intracellular NRP-1 SEA domain, and intracellular associations between NRP-1, the scaffold protein GIPC, and the nonreceptor tyrosine kinase c-Abl, that augmented α5β1 FN fibril assembly activity. Analysis of human cancer specimens established an association between tumoral NRP-1 levels and clinical outcome. Our findings indicate that NRP-1 activates the tumor microenvironment, thereby promoting tumor growth. These results not only identify new molecular mechanisms of FN fibril assembly but also have important implications for therapeutic targeting of the myofibroblast in the tumor microenvironment.

Exosome Adherence and Internalization by Hepatic Stellate Cells Triggers Sphingosine 1-Phosphate-dependent Migration

“…We hypothesized that adhesion between exosomes and HSC may require ligand/receptor interactions to facilitate chemotactic signaling. FN is a glycoprotein of the extracellular matrix that is secreted by EC during liver fibrosis (27,(35)(36)(37)42). Indeed, exosomes contained FN, as detected by FN immunogold labeling (Fig.…”

“…SK1 is an enzyme that produces the HSC chemotactic factor S1P. Additionally, active SK1 enzyme has been detected in the extracellular environment, although not specifically within an exosome fraction (24,25,27,(35)(36)(37). We therefore focused on SK1-derived S1P as a potential pathway relevant to our model of EC-HSC interaction.…”

Synectin promotes fibrogenesis by regulating PDGFR isoforms through distinct mechanisms

“…For this purpose, we overexpressed a NRP-1 mutant that lacked the SEA domain (NRP-1ΔSEA), as this protein is unable to bind synectin (9). For control purposes, we overexpressed WT NRP-1.…”

“…Synectin (also referred to in the literature as GIPC) contains a PDZ domain that mediates the binding of multiple transmembrane proteins either directly or through coreceptors, such as the glycoprotein neuropilin-1 (NRP-1) (8,9). Previous work showed that synectin, with its NRP-1 binding partner, played a key role in fibronectin fibril assembly in tumor-associated myofibroblasts (9), raising the possibility that a similar phenomenon may take place in broader pathological conditions such as liver fibrosis; this is a phenomenon, however, that awaits experimental confirmation. Moreover, the effects that synectin has on the regulation of PDGFRs and their downstream fibrogenic response have not been examined, leading us to the present study aimed at investigating the role of this protein on PDGFR signaling and cellular functions in HSC.…”

Conformational remodeling of the fibronectin matrix selectively regulates VEGF signaling

“…Emerging evidence has implicated NRPs in the regulation of integrin function (reviewed in Goel et al, 2012;Goel and Mercurio, 2013). NRP1 has been shown to promote a5b1 activation and function in both matrix assembly (Yaqoob et al, 2012) and endothelial cell adhesion to fibronectin (Valdembri et al, 2009). Our studies now present evidence that the a5b1 integrin can regulate NRP1 function, thus demonstrating the bidirectionality of integrin-NRP1 crosstalk.…”