Hepatitis B Virus Covalently Closed Circular DNA Predicts Postoperative Liver Cancer Metastasis Independent of Virological Suppression

Simple Summary The quantitative assessment of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) is essential to the development of next generation antiviral therapies against hepatitis B. Here, we developed a peptide nucleic acid (PNA)-clamping qPCR method to quantify cccDNA, which was comparable to the recently proposed exonuclease-based cccDNA assays. Using this method, we showed that cccDNA levels in the para-neoplastic liver tissues were independently correlated with overall survival, as well as extrahepatic metastasis in patients with or without virological suppression. These results suggest that in HBV-related hepatocellular carcinoma, patients under antiviral suppression might further benefit from new antivirals, which are designed to reduce cccDNA. New antiviral therapies against hepatitis B virus (HBV) focus on the elimination of covalently closed circular DNA (cccDNA). However, traditional cccDNA-specific quantitative PCR (qPCR) has a narrow effective range, hindering a reliable comparison between the levels of biopsy-derived cccDNAs. Collaterally, the prognostic role of cccDNA in HBV-related hepatocellular carcinoma (HCC) cannot be clearly defined. Here, we developed a peptide nucleic acid (PNA)-clamping qPCR method to provide a wider range of specific cccDNA quantification (up to 5 logs of effective range). Extrachromosomal DNA was extracted from para-neoplastic tissues for cccDNA quantification. In total, 350 HBV-related HCC patients were included for an outcome analysis. Without differential pre-dilution, cccDNA levels in para-neoplastic liver tissues were determined, ranging from < 2 x 10(3) to 123.0 x 10(6) copies/gram. The multivariate linear regression analysis showed that cccDNA was independently correlated with the HBV e antigen (p < 0.001) and serum HBV-DNA levels (p = 0.012). The Cox proportional hazard model analysis showed that cccDNA independently predicted overall survival (p = 0.003) and extrahepatic metastasis-free survival (p = 0.001). In virologically suppressed HCC patients, cccDNA still effectively predicted intrahepatic recurrence-free (p = 0.003) and extrahepatic metastasis-free (p = 0.009) survivals. In conclusion, cccDNA independently predicted postoperative extrahepatic metastasis-free survival.

Automated summary

The study developed a PNA-clamping qPCR method to quantify cccDNA with a wider effective range, and found that cccDNA independently predicted overall survival and extrahepatic metastasis in HBV-related hepatocellular carcinoma patients.