Loss of exosomal miR-320a from cancer-associated fibroblasts contributes to HCC proliferation and metastasis

Cancer-associated fibroblasts (CAFs) play a pivotal role in regulating tumour progression. Therefore, understanding how CAFs communicate with hepatocellular carcinoma (HCC) is crucial for HCC therapy. Recently, exosomes have been considered an important messenger between cells. In this study, we performed microRNA (miRNA) sequencing of exosomes derived from CAFs and corresponding para-cancer fibroblasts (PAFs) of HCC patients. We found a significant reduction in the miR-320a level in CAF-derived exosomes. Using exogenous miRNAs, we demonstrated that stromal cells could transfer miRNA to HCC cells. In vitro and in vivo studies further revealed that miR-320a could function as an antitumour miRNA by binding to its direct downstream target PBX3 to suppress HCC cell proliferation, migration and metastasis. The miR-320a-PBX3 pathway inhibited tumour progression by suppressing the activation of the MAPK pathway, which could induce the epithelial-mesenchymal transition and upregulate cyclin-dependent kinase 2 (CDK2) and MMP2 expression to promote cell proliferation and metastasis. In xenograft experiments involving CAFs mixed with MHCC97-H cells, miR-320a over-expression in CAFs could inhibit tumourigenesis. Therefore, these data suggest that CAF-mediated HCC tumour progression is partially related to the loss of antitumour miR-320a in the exosomes of CAFs and that promoting the transfer of stromal cell-derived miR-320a might be a potential treatment option to overcome HCC progression. (C) 2017 Elsevier B.V. All rights reserved.