Exosomal nidogen 1 drives liver cancer metastasis by inducing secretion of tumour necrosis factor receptor 1 from activated lung fibroblasts

Abstract

Introduction: Hepatocellular carcinoma (HCC) is an aggressive tumour with metastasis as a signature in the advanced stage. Acquisition of migratory and invasive behaviours is fundamental to cancer cells to metastasize. A supportive microenvironment for the colonization of incoming disseminated cancer cells during metastasis is also indispensable. Exosome shedding has emerged as an important channel for intercellular communication in tumour microenvironment during metastasis. Methods: Exosomes derived from HCC cell lines were functionally characterized by in vitro and in vivo assays. Proteomic profiling and expression level of exosomal proteins were analysed by mass spectrometry and enzyme-linked immunosorbent assay (ELISA), respectively. The study of interplay between exosomes, HCC cells and lung fibroblasts were carried out using functional assays, immunofluorescent staining and ELISA. Results: Exosomes derived from metastatic HCC cells augmented cell migration and invasiveness. In animal model, metastatic-exosomes promoted liver tumour formation, increased incidence of distant metastasis to lungs as well as facilitated colonization of hepatoma cells in lungs and enhanced the permeability of pulmonary vasculature. Proteomic profiling of exosomes identified nidogen 1 (NID1) as a functional component responsible for the promoting effect of metastatic-exosomes. Our data showed that suppression of exosomal NID1 (exo-NID1) significantly diminished the biological activities of metastatic-exosomes. Apart from HCC cells, exo-NID1 enhanced the growth and induced activation of lung fibroblasts. Tumour necrosis factor receptor 1 (TNFR1), found to be released by lung fibroblast pretreated with metastatic-exosomes, showed potent effect in promoting HCC cell motility. Notably, the level of exo-NID1 was well correlated with the metastatic potential of parental HCC cells. Encouragingly, the level of NID1 in circulating exosomes of HCC late stage patients was higher than those at early stage. Summary/Conclusion: Our study reveals the novel role of NID1, in the form of exosomes, in HCC metas- tasis and illuminates the expression profile of exosomal NID1 with clinical significance. Our study implicates that targeting signalling pathway mediated by exosomes of metastatic HCC as a therapeutic strategy for HCC.