Abstract
Hepatocellular carcinoma (HCC) is the most predominant type of liver cancer and is frequently fatal. Alpha-fetoprotein, alpha-fetoprotein-L3, and protein induced by vitamin K absence or antagonist-II are used as biomarkers to diagnose HCC. However, these biomarkers are not highly specific, especially for early-stage HCC diagnosis; therefore, more specific biomarkers are needed. Recently, circular RNA (circRNA) biomarkers have been used to diagnose several intractable diseases. In this study, we sought to identify circRNA biomarkers for the specific diagnosis of HCC. To this end, we compared the expression levels of circRNAs in primary HCC and normal tissues using publicly available RNA-seq data. Our analysis revealed that the expression levels of eight circRNAs were altered in primary HCC tissues compared with normal tissues. To confirm our findings, we examined the expression levels of selected circRNAs in HCC cell lines and normal hepatocytes. The expression level of hsa_circ_0001438, a circRNA that was downregulated in primary HCC, was lower in poorly and well-differentiated HCC cell lines than in normal hepatocytes. By contrast, the expression level of hsa_circ_0000417, which was increased in primary HCC, was strongly upregulated in a well-differentiated HCC cell line compared with normal hepatocytes. Thus, hsa_circ_0001438 and hsa_circ_0000417 might be potential biomarkers for the specific diagnosis of HCC. The experimental strategy described here, using publicly available RNA-seq data, is a useful and cost-effective method of identifying circRNA biomarkers.