CircRNA expression profiling of PBMCs from patients with hepatocellular carcinoma by RNA-sequencing

Circular RNAs (circRNAs) are differentially expressed in various cancer types. The present study aimed to investigate the expression and clinical implication of circRNAs in hepatocellular carcinoma (HCC) and to evaluate the potential of circRNAs as diagnostic biomarkers for HCC. CircRNA expression was profiled in 19 patients with HCC and 19 normal controls using ribosomal RNA-depleted RNAs. Differentially expressed circRNAs (DE-circRNAs) between HCC and controls were identified using CIRI2 and distinct circRNA expression signatures were screened. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes were used to predict the potential functions of these DE-circRNAs and the circRNA-miRNA-mRNA regulatory networks were then constructed. Several DE-circRNAs were selected and confirmed by RT-qPCR. A total of 40 DE-circRNAs (27 upregulated and 13 downregulated) were identified between patients with HCC and controls. Functional annotation indicated that these DE-circRNAs were involved in cellular components, molecular functions and cancer-associated pathways related to HCC. These included pathways in cancer, TNF signaling pathway, hepatitis B, hepatitis C and hepatocyte differentiation. The circRNA-miRNA-mRNA regulatory network was generated based on 11 candidate circRNAs. Receiver operating characteristic curve analysis indicated that Homo sapiens (hsa)_circ_0073239, hsa_circ_007090, hsa_circ_0008304, hsa_circ_0017586, hsa_circ_0000369 and hsa_circ_0001181 may serve as potential biomarkers for HCC. Results from Cell Counting Kit-8 assay suggested that small interfering RNA targeting hsa_circ_0001181 reduced the proliferation of HepG2 cells, which implicated it as a potential therapeutic target for HCC. Therefore, in the present study, the differential expression pattern and important role of circRNAs in HCC were determined. The present results highlight the diagnostic potential of circRNAs in HCC and provide novel insight into the development of and treatment approaches for HCC.