Identification and extensive analysis of inverted-duplicated HBV integration in a human hepatocellular carcinoma cell line

Re-analysis of hepatitis B virus integration sites reveals potential new loci associated with oncogenesis in hepatocellular carcinoma

BACKGROUND

Hepatitis B virus (HBV) is a major cause of hepatocellular carcinoma (HCC). HBV DNA can get integrated into the hepatocyte genome to promote carcinogenesis. However, the precise mechanism by which the integrated HBV genome promotes HCC has not been elucidated.

AIM

To analyze the features of HBV integration in HCC using a new reference database and integration detection method.

METHODS

Published data, consisting of 426 Liver tumor samples and 426 paired adjacent non-tumor samples, were re-analyzed to identify the integration sites. Genome Reference Consortium Human Build 38 (GRCh38) and Telomere-to-Telomere Consortium CHM13 (T2T-CHM13 (v2.0)) were used as the human reference genomes. In contrast, human genome 19 (hg19) was used in the original study. In addition, GRIDSS VIRUSBreakend was used to detect HBV integration sites, whereas high-throughput viral integration detection (HIVID) was applied in the original study (HIVID-hg19).

RESULTS

A total of 5361 integration sites were detected using T2T-CHM13. In the tumor samples, integration hotspots in the cancer driver genes, such as TERT and KMT2B, were consistent with those in the original study. GRIDSS VIRUSBreakend detected integrations in more samples than by HIVID-hg19. Enrichment of integration was observed at chromosome 11q13.3, including the CCND1 pro-moter, in tumor samples. Recurrent integration sites were observed in mitochondrial genes.

CONCLUSION

GRIDSS VIRUSBreakend using T2T-CHM13 is accurate and sensitive in detecting HBV integration. Re-analysis provides new insights into the regions of HBV integration and their potential roles in HCC development.

HBV integrated genomic characterization revealed hepatocyte genomic alterations in HBV-related hepatocellular carcinomas

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies that is closely associated with the Hepatitis B virus (HBV). HBV integration into host genomes can induce instability and the aberrant expression of human genomic DNA. To directly assess HBV integration breakpoints at whole genome level, four small sequencing libraries were constructed and the HBV integration profiles of four patients with HCC were characterized. In total, the current study identified 11,800,974, 11,216,998, 11,026,546 and 11,607,842 clean reads for patients 1-3 and 4, respectively, of which 92.82, 95.95, 97.21 and 97.29% were properly aligned to the hybrid reference genome. In addition, 220 HBV integration events were detected from the tumor tissues of four patients with HCC and an average of 55 breakpoints per sample was calculated. The results indicated that HBV integration events may be implicated in HCC physiologies and diseases. The results acquired may also provide insight into the pathogenesis of HCC, which may be valuable for future HCC therapy.

How did hepatitis B virus effect the host genome in the last decade?

The principal reason of chronic liver disease, cirrhosis and hepatocellular carcinoma is chronic viral hepatitis all over the world. Hepatitis B virus (HBV) has some mutagenic effects on the host genome. HBV may be exhibiting these mutagenic effects through integrating into the host genome, through its viral proteins or through some epigenetic mechanisms related with HBV proteins. This review aims to summarize the molecular mechanisms used by HBV for effecting host genome determined in the last decade. The focus will be on the effects of integration, HBV proteins, especially HBV X protein and epigenetic mechanisms on the host genome. These interactions between HBV and the host genome also forms the underlying mechanisms of the evolution of hepatocellular carcinoma.