Circulating Exosomal MicroRNA-1307-5p as a Predictor for Metastasis in Patients with Hepatocellular Carcinoma

SIMPLE SUMMARY: Exosomal microRNAs (exo-miRs) significantly contribute to cancer metastasis. However, few studies have investigated the role of exosomes as metastasis mediators in hepatocellular carcinoma (HCC) despite recent advancements in liquid biopsy. We aimed to identify pro-metastatic circulating exo-miRs potentially predicting metastasis onset in HCC through comprehensive and systematic integrative analyses of plasma exo-miR sequencing data and publicly available RNA expression datasets, and accordingly propose a potential mechanism of action of pro-metastatic miRs, including promoting epithelial–mesenchymal transition (EMT). We found that circulating exo-miR-1307-5p is a predictive marker for metastasis in patients with HCC, and EMT promotion through SEC14L2 and ENG downregulation could be the potential downstream pathway of miR-1307-5p. We believe that our study makes a significant contribution to the literature because our findings provide novel insights into the role of circulating exo-miRs in the pathogenesis and progression of HCC and suggest that exo-miRs are a potential treatment target in HCC. ABSTRACT: Exosomal microRNAs (exo-miRs) contribute to cancer metastasis. To identify pro-metastatic circulating exo-miRs in hepatocellular carcinoma (HCC), next-generation sequencing-based plasma exo-miR profiles of 14 patients with HCC (eight non-metastatic and six with metastasis within 1 year of follow-up) were analyzed. Sixty-one miRs were significantly overexpressed among patients with metastatic HCC. Candidate miRs were selected through integrative analyses of two different public expression datasets, GSE67140 and The Cancer Genome Atlas liver hepatocellular carcinoma (TCGA_LIHC). Integrative analyses revealed 3 of 61 miRs (miR-106b-5p, miR-1307-5p, and miR-340-5p) commonly overexpressed both in metastasis and vascular invasion groups, with prognostic implications. Validation was performed using stored blood samples of 150 patients with HCC. Validation analysis showed that circulating exo-miR-1307-5p was significantly overexpressed in the metastasis group (p = 0.04), as well as in the vascular invasion and tumor recurrence groups. Circulating exo-miR-1307-5p expression was significantly correlated with tumor stage progression (p < 0.0001). Downstream signaling pathways of miR-1307 were predicted using TargetScan and Ingenuity Pathway Analysis. On comprehensive bioinformatics analysis, the downstream pathway of miR-1307-5p, promoting epithelial–mesenchymal transition (EMT), showed SEC14L2 and ENG downregulation. Our results show that circulating exo-miR-1307-5p promotes metastasis and helps predict metastasis in HCC, and SEC14L2 and ENG are target tumor suppressor genes of miR-1307 that promote EMT.