Fig. 1

Identification and characteristics of circUCK2(2,3) in HCC. A Heat map of upregulated circRNAs in five HCC tissues compared to matched normal tissues (the top five upregulated circRNAs are highlighted with a red rectangle box). B Schematic showing the generation of circUCK2(2,3) from exon 2 and exon 3 of UCK2. The nucleotide sequence of the back-splicing site of circUCK2(2,3) was confirmed by Sanger sequencing. C and D qRT–PCR assessed the resistance of circUCK2(2,3) to RNase R treatment (C), and evaluated the stability of circUCK2(2,3) after actinomycin D treatment (D). E qRT–PCR assessment of the nuclear or cytoplasmic distribution of circUCK2(2,3). F Relative expression of circUCK2(2,3) in the Jin-Ling cohort, containing 70 paired HCC and peritumor tissues. G Tumor versus peritumor expression ratio of circUCK2(2,3) in clinical samples of the Jin-Ling cohort. H and I Kaplan–Meier curve showing the association between circUCK2(2,3) expression and recurrence free survival at 5 years (H) or 1 years (I) post surgery. Survival curves were compared using the log-rank test. Data are shown as the mean ± SD. Statistical analyses were performed using paired Student’s t-tests (NS, no statistical significance; *p < 0.05; **p < 0.01; ***p < 0.001). UCK2 uridine-cytidine kinase 2, circUCK2(2,3) circRNA uridine-cytidine kinase 2, GAPDH glyceraldehyde-3-phosphate dehydrogenase, MALAT1 metastasis associated lung adenocarcinoma transcript 1, BIRC5 baculoviral IAP repeat containing 5, HCC hepatocellular carcinoma, PT peritumor, T/P tumor versus peritumor