Circulating cell-free DNA species affect the risk of hepatocellular carcinoma in treated chronic hepatitis B patients

Hepatocellular carcinoma (HCC) may still develop in chronic hepatitis B (CHB) patients even under effective long-term oral antiviral therapy, but its pathogenesis in the setting of long-standing inhibition of viral replication has not been completely elucidated. We investigated whether species of circulating cell-free DNA (cfDNA) may be involved in the process of hepatocarcinogenesis in treated CHB patients. Serum samples were obtained from HBeAg-negative CHB patients with (HCC cases, n = 37) or without HCC development during the first 5 years of oral antiviral therapy (controls, n = 74). HCC cases and controls were matched 1:2 for age, sex and platelets. Determination of different circulating cfDNA species (before HCC diagnosis in HCC cases) including total cfDNA quantity, levels of Alu repeat DNA and RNase P coding DNA, copies of mitochondrial DNA and levels of 5-methyl-2′-deoxycytidine as an indicator of DNA methylation was performed. HCC cases compared with controls had higher median levels of Alu247 (123 vs 69 genomic equivalent, p =.042) and RNase P coding DNA (68 vs 15 genomic equivalent, p <.001). In contrast, median cfDNA concentration, Alu115 levels, Alu247/Alu115 ratio as an index of DNA integrity and mitochondrial DNA copies did not differ significantly between HCC cases and controls. Receiver operating characteristic curve analysis showed that levels RNase P coding DNA offered good prediction of subsequent HCC development (c-statistic: 0.80, p <.001). In conclusion, serum levels of RNase P coding DNA are increased years before HCC diagnosis and could be potentially helpful in the prediction of the HCC risk in treated HBeAg-negative CHB patients.