Quantification of hepatitis B virus covalently closed circular DNA in patients with hepatocellular carcinoma

Background/Aims This study aimed to measure the intrahepatic total hepatitis B virus (HBV) DNA and covalently closed circular DNA (cccDNA) levels in tumor and non-tumor tissues in hepatocellular carcinoma (HCC) patients. Methods Intrahepatic total HBV DNA and cccDNA were measured in 25 HCC patients (21 hepatitis B surface antigen [HBsAg]-positive and 4 HBsAg-negative) by the Invader® assay. Results A low level of intrahepatic HBV DNA was detectable in all HBsAg-negative patients. For HBsAg-positive patients, the intrahepatic total HBV DNA levels in the tumor and non-tumor tissues were comparable (P = 0.903). However, the tumor tissues had significantly higher levels of cccDNA (0.35 vs. 0.16 copies/cell, P = 0.030) and higher proportion of intrahepatic HBV DNA in the form of cccDNA (100% vs. 84%, P = 0.004) than the non-tumor tissues. Seventeen out of 21 (81%) tumor tissues had intrahepatic HBV DNA solely in cccDNA form. Analysis of HBV mRNA expression indicated that HBV replication appeared to be lower in the tumor tissues than the non-tumor tissues. Conclusions Compared to the non-tumor tissues, the levels of HBV replication in the tumor tissues appeared to be lower, and cccDNA was the predominant form of HBV DNA in the tumor tissues.