Abstract: Objective To construct the regulatory network of survival-related onco-miRNAs and their target genes in hepatocellular carcinoma (HCC) and verify the interactions between the key miRNAs and their targets. Methods We screened survival-related miRNAs in HCC in OncomiR and Oncolnc databases, predicted their target genes using miRNet, and conducted survival and expression analysis using GEPIA2 and Ualcan, respectively. The miRNA-target gene co-expression analysis was performed and the miRNA-target network was constructed. Enrichment analysis was performed in Enrichr and protein-protein interaction analysis in STRING database. We tested the effects of transfection with the mimic or inhibitor of hsa-miR-1226-3p or hsa-miR-221-5p on proliferation of HepG2 cells using CCK8 assay and examined the changes in the expressions of the target genes using RT-qPCR. The effect of transfection with hsa-miR-221-5p mimic or inhibitor on protein expressions of the target genes was examined using Western blotting in. A dual luciferase reporter assay was used to test the interaction between hsa-miR-221-5p and its potential target gene GCDH. We further examined the effect of transfection with hsa-miR-221-5p mimic and pEGFP N1-GCDH, alone or in combination, on proliferation, migration and invasion of HepG2 cells. Results We identified 223 survival-related miRNAs in HCC from OncomiR and 146 miRNAs from Oncolnc with an intersection of 131 miRNAs, and 48 miRNAs were identified as onco-miRNAs in HCC after survival and expression analysis. Twenty-seven eligible target genes were identified after miRNA-mRNA co-expression analysis. The constructed miRNA-target gene network consisted of 25 miRNAs and 27 target genes. The most enriched term was fatty acid metabolism for the target genes. In HepG2 cells, transfection with the mimic or inhibitor of hsa-miR-1226-3p or hsa-miR-221-5p caused significant changes of the mRNA and protein levels of their respective target genes (P<0.05). The results of dual luciferase reporter assay confirmed the targeting relationship between hsa-miR-221-5p and GCDH gene (P<0.05). Transfection with hsa-miR-221-5p mimic significantly suppressed the proliferation, migration and invasion of HepG2 cells, but this effect was obviously relieved by co-transformation with pEGFP N1-GCDH (P<0.05). Conclusion Fatty acid metabolism might be one of the most crucial pathways that mediate the effect of the onco-miRNAs in HCC, and the hsa-miR-221-5p/GCDH axis is an important molecular mechanism for HCC progression.

Key words: hepatocellular carcinoma; onco-miRNA; regulatory network; bioinformatic analysis