Exosomal miR-9-3p suppresses HBGF-5 expression and is a functional biomarker in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer-related death worldwide. Exosomes are secreted membrane vesicles that play important roles in various diseases by transporting proteins and RNAs, including microRNAs, between cells. However, the function of exosomal miRNA in HCC has not been fully investigated.

Exosomes were obtained from the sera by ultracentrifugation and were processed for transmission electron microscopy (TEM). Real time PCR were revealed changes of miRNA between patients and normal donors. Predicted targets of miRNA were described by bioinformatics analysis, luciferase reporter assay was used to confirmed whether miR-9-3p regulates target expression. And then miRNA were over-expressed in HCC cell line to study its function, western blotting were used to test expression of miRNA targets, Cell viability and proliferation were analyzed after over-expressed miR-9-3p using MTT and BrdU assay.

Serum exosomes from patients with HCC contained significantly lower levels of the miR-9-3p than did serum exosomes from normal donors, suggesting a potential role for this microRNA in HCC. Bioinformatics analysis identified fibroblast growth factor 5 (HBGF-5), which plays an important role in cell proliferation, as a potential miR-9-3p target mRNA. Luciferase reporter assay confirming that miR-9-3p can directly regulate HBGF-5 expression. Consistent with this finding, overexpression of miR-9-3p in three HCC cell lines significantly downregulated HBGF-5 expression at both the mRNA and protein levels. Finally, overexpression of miR-9-3p reduced HCC cell viability and proliferation, and additionally reduced ERK1/2 expression, suggesting a potential mechanism by which miR-9-3p acts.

These results provide new insight into the functions of miR-9-3p and HBGF-5 in HCC and identify miR-9-3p as a potential therapeutic target for HCC.