Identification of circRNAs involved in the development of hepatocellular carcinoma after insufficient radiofrequency ablation

Previous studies have reported that circular RNAs (circRNAs) play a key role in the pathogenesis and progression of various diseases. In the present study, we aimed to identify potential circRNAs associated with the progression of hepatocellular carcinoma (HCC) after insufficient radiofrequency ablation (IRFA). A xenograft mouse IRFA model was initially established, and immunohistochemical staining (IHC) and polymerase chain reaction (PCR) were performed to confirm the expression of programmed cell death-ligand 1 (PD-L1) and vascular endothelial growth factor receptor-1 (VEGFR-1). CircRNA expression alterations were screened by next-generation sequencing (RNA-seq). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted to predict the function of genes coding differentially expressed circRNAs. The selected circRNAs were validated utilizing PCR and Sanger sequencing. The relationships between circRNAs, microRNAs, PD-L1, and VEGFR-1 were predicted by bioinformatics. Overall, a total of 612 circRNAs were differentially expressed in IRFA-treated subcutaneous tumorigenesis tissue. Among them, 435 circRNAs were significantly upregulated and 177 circRNAs were downregulated. GO and KEGG analyses were employed to predict the functions of these circRNAs. Thereafter, quantitative reverse transcription PCR (qRT-PCR) assays determined that these seven circRNAs were overexpressed in the IRFA group, which was consistent with the RNA-seq results. Based on the bioinformatic analysis, seven circRNAs confirmed by Sanger sequencing were predicted to likely regulate PD-L1 and VEGFR-1 expression levels by functioning as sponges for microRNAs (miRNAs) and forming a circRNA-miRNA-PD-L1/VEGFR-1 regulatory network. Finally, IHC and qRT-PCR of PD-L1 and VEGFR-1 confirmed the activation of this pathway. Taken together, we report that differentially expressed circRNAs might simultaneously regulate PD-L1 and VEGFR-1 in the IRFA tissues, which provides a novel view of circRNAs in HCC progression after the IRFA procedure.