Patient-derived circulating exosomes enhance cancer and stemness properties through polymeric immunoglobulin receptor in liver cancer

Abstract

Introduction: Hepatocellular carcinoma (HCC) is a primary malignancy of liver which often diagnosed at an advanced stage accompanied by extrahepatic metastasis. Emerging evidences have demonstrated cancer cells derived exosomes play an important role in intercellular communication in tumour microenvironment during metastasis. Thus, exosome research may solve the mystery of metastatic organotropism in HCC. Methods: Exosomes were isolated from HCC patients. The biological effects of exosomes were studied using transwell and matrigel invasion assays. The in vivo effect of exosomes were analysed in mice by intravenous injection of exosomes together with hepatoma cells. Thein vivolung pulmonary vasculature and vascular leakiness were revealed by FITC-lectin stain and presence of Texas Red-dextran, respectively. Stem-like properties were examined by spheroid assay and flow cytometry. Proteomic profiling and expression level of exosomal proteins were analysed by mass spectrometry and enzyme-linked immunosorbent assay (ELISA), respectively. Results: We recruited representative individuals of different stages of HCC development for the collection of circulating exosomes, namely, exosomes of healthy individual (Normal-Exo), patient with cirrhosis (Cirrhosis-Exo), HCC patients at early stage (E-HCC-Exo) and late stage with distant metastasis to lungs (L-HCC-Exo). Among these exosomes, L-HCC-Exo exhibited the highest effect in promoting HCC cell migration and invasionin vitro and colonization of hepatoma cells in lungs. L-HCC-Exo also modulated tumour microenvironment by enhancing pulmonary vascular permeability. Along with cancerous behaviours, L-HCC-Exo induced stem-like properties such as increased self-renewal, expressions of hepatic CSC markers and drug resistance. Elevated level and activity of β-catenin were also detected in cells stimulated by L-HCC-Exo. Proteomic profiling of exosomal proteins identified polymeric immunoglobulin receptor (pIgR) to be markedly upregulated in L-HCC-Exo when compared with exosomes of other subjects. Summary/Conclusion: HCC patient-derived circulating exosomes augment cancer and stemness properties through the activation of β-catenin signalling by exopIgR, leading to a more aggressive phenotype in HCC umourigenesis and metastasis.