CircRNAs have a covalently closed loop structure without 5′–3′polarity and polyadenylation tails, making they are more stable than linear RNA and less susceptible to RNA exonuclease or RNase R. Here, RNA samples obtained from HCC cell lines were digested by RNase R and the linear mRNA and circRNA of CSPP1 before and after treatment were detected. Here, CSPP1 is linked to hepatocellular carcinoma.