Circular RNA expression and association with the clinicopathological characteristics in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. Circular RNAs (circRNAs) are a novel class of RNAs, with higher stability and tissue specificity, which may be of value as novel clinical markers. High‑throughput RNA sequencing was used to profile the expression of circRNAs in 5 pairs of cancer and normal tissues, and reverse transcription‑quantitative PCR (RT‑qPCR) analysis was employed to verify the results of the RNA sequencing in 45 cases of PTC. The dysregulated circRNA expression and clinicopathological characteristics were assessed and the potential roles of circRNAs in the cellular miRNA and mRNA network were predicted using bioinformatics analysis. The results demonstrated that, compared with normal tissues, a total of 53 circRNAs were dysregulated in tumour tissues, and 8 circRNAs were validated at the mRNA level (P<0.001 and P<0.01). Among those, the expression of chr5:161330882‑161336769‑ (P=0.015), chr9:22046750‑22097364+ (P=0.041) and chr8:18765448‑18804898‑ (P=0.036) were obviously associated with the BRAFV600E mutation, chr12:129699809‑129700698‑ was associated with capsular invasion (P=0.025) and chr5:38523418‑38530666‑ was associated with pT stage (P=0.037) and lymph node metastasis (P=0.002). Therefore, some dysregulated circRNAs were found to be associated with BRAFV600E mutation, capsular invasion, advanced pT stage and lymph node metastasis of PTC, indicating that circRNAs may be involved in tumourigenesis and cancer progression, and they may be putative biomarkers for the diagnosis and evaluation of progression of PTC.