Ovarian Cancer-Derived Exosomal Fibronectin Induces Pro-Inflammatory IL-1β

Abstract

The tumour microenvironment is characterized by pro-inflammatory profiles, including interleukin-1β (IL-1β). This profile is generated by infiltrating macrophages following interactions with tumours or their components. The objectives of this study were to identify whether tumour exosomes could induce macrophage IL-1β production and the mechanism involved. Exosomes were isolated from ovarian cancer patients and ovarian tumour cells by chromatography and ultracentrifugation. Specific exosomal proteins were defined by mass spectrometry (MS) and confirmed by Western immunoblotting. Using macrophage-like THP-1 cells, induction of IL-1β release was investigated by ELISA. RGD peptides were used to block fibronectin binding by THP-1 α5β1 integrin. Exosomes isolated from ovarian cancer patients and from ovarian cancer cells were demonstrated, by MS and immunoblotting, to express fibronectin. Incubation of THP-1 cells with these exosomes induced pro-inflammatory cytokines, in particular IL-1β. Blocking of THP-1 binding of exosomal fibronectin with RGD peptides abrogated exosome-mediated IL-1β production and down-stream phosphorylation of Akt and c-Jun. Although cancer patients generally exhibit increased levels of IL-1β, the underlying mechanism is unclear. Here, tumour-derived exosomes are demonstrated to induce pro-inflammatory cytokine in macrophages including IL-1β, whose induction is mediated by fibronectin.