Hepatitis B virus full-length genomic mutations and quasispecies in hepatocellular carcinoma

Abstract

Background and aim: Hepatitis B virus (HBV) full-length genomic mutations and quasispecies characteristics in hepatocellular carcinoma (HCC) were investigated.

Methods: Hepatitis B virus DNA was extracted from the tumor and non-tumor tissues of 16 HCC patients. Overlapping DNA fragments covering the entire HBV genome were amplified and sequenced. To study HBV sequence at the quasispecies level, the preS region was amplified and clonally sequenced. HBV mutation profiles, quasispecies complexity and diversity, and phylogenetic characteristics were assessed.

Results: Fourteen patients had full-length HBV amplification. Hot-spot mutations at HBx aa130-131 and pre-S deletions were detected in 13 (93%) and 6 (43%) patients, respectively. Deletions in the X/preC/C regions were more frequently detected in the tumor than in the non-tumor tissues (P = 0.031). Compared with the non-tumor tissues, the tumor tissues had a lower quasispecies complexity (P = 0.014 and 0.043, at the nucleotide and amino acid levels, respectively) and diversity (P = 0.048 and 0.022, at the nucleotide and amino acid levels, respectively). Phylogenetic analysis showed that HBV sequences derived from tumor and non-tumor tissues were separately clustered, suggesting the occurrence of compartmentalization, which was confirmed by the correlation coefficient testing on both the number and length of branches of viral populations (all P < 0.02).

Conclusions: Hepatitis B virus mutation patterns in HCC tumor tissues and non-tumor tissues were different. HBV quasispecies within the preS region were compartmentalized, and tumor tissues had a lower genome complexity and diversity. Our study suggests HBV evolution is conditioned by the differential host cellular environment in HCC tumors.

Keywords: full-length genome sequencing; hepatitis B virus; hepatocellular carcinoma; mutation; quasispecies.