Selective downregulation of distinct circRNAs in the tissues and plasma of patients with primary hepatic carcinoma

Multiple studies have indicated that circular RNAs (circRNAs) are closely associated with malignant tumor development and metastasis. However, the significance of circRNAs in primary hepatic carcinoma (PHC), particularly in the plasma, remains largely undetermined. In the current study, circRNA expression profiles in three pairs of tumor and adjacent normal samples from patients with PHC, were examined using circRNA chip screening. A total of 80 circRNAs were upregulated, while 75 circRNAs were downregulated in PHC tissues, relative to para-tumor tissues (fold change, ≥1.5). A total of two upregulated circRNAs and three downregulated circRNAs were selected as candidates for further validation of their differential expression. This was performed using reverse transcription-quantitative PCR with 11 pairs of PHC tissues and para-tumor tissues. The results indicated that hsa_circ_0003056 exhibited reduced expression in PHC tissues. Moreover, hsa_circ_0003056 and hsa_circ_0067127 were quantified in the plasma samples of 35 PHC patients and 32 healthy donors. The results revealed that hsa_circ_0067127 was significantly downregulated in the patients' plasma. Finally, a competing endogenous RNA network was constructed, which consisted of one circRNA (hsa_circ_0003056 or has_circ_0067127), five miRNAs and miRNA-targeted genes (mRNAs). Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that differentially expressed (DE) genes were significantly enriched in the pathway associated with ‘regulation of the pluripotency of stem cells’ for hsa_circ_0003056, and ‘ubiquitin-mediated proteolysis’ and ‘prostate cancer’ for hsa_circ_0067127. Gene ontology analysis revealed that DE genes were primarily associated with the ‘modulation of kinase activity’ and ‘intracellular and transmembrane-ephrin receptor activity’ for hsa_circ_0003056, ‘artery morphogenesis activity’, ‘HOPS complex and transferase activity’ and in ‘transferring acyl groups’ for hsa_circ_0067127. This approach indicated that hsa_circ_0003056 in PHC tissue, and hsa_circ_0067127 in PHC plasma, are downregulated and may be implicated in the tumorigenesis of PHC.