Viral integration drives multifocal HCC during the occult HBV infection

Abstract

Background & Aims Although the prognosis of patients with occult hepatitis B virus (HBV) infection (OBI) is usually benign, a small portion may undergo cirrhosis and subsequently hepatocellular carcinoma (HCC). We studied the mechanism of life-long Integration of virus DNA into OBI host’s genome, of which may induce hepatocyte transformation. Methods We applied HBV capture sequencing on single cells from an OBI patient who, developed multiple HCC tumors and underwent liver resection in May 2013 at Tongji Hospital in China. Despite with the undetectable virus DNA in serum, we determined the pattern of viral integration in tumor cells and adjacent non-tumor cells and obtained the details of the viral arrangement in host genome, and furthermore the HBV integrated region in cancer genome. Results HBV captured sequencing of tissues and individual cells revealed that samples from multiple tumors shared two viral integration sites that could affect three host genes, including CSMD2 on chr1 and MED30 / EXT1 on chr8. Whole genome sequencing further indicated one hybrid chromosome formed by HBV integrations between chr1 and chr8 that was shared by multiple tumors. Additional 50 poorly differentiated liver tumors and the paired adjacent non-tumors were evaluated and functional studies suggested up-regulated EXT1 expression promoted HCC growth. We further observed that the most somatic mutations within the tumor cell genome were common among the multiple tumors, suggesting that HBV associated, multifocal HCC is monoclonal in origin. Conclusion Through analyzing the HBV integration sites in multifocal HCC, our data suggested that the tumor cells were monoclonal in origin and formed in the absence of active viral replication, whereas the affected host genes may subsequently contribute to carcinogenesis. Electronic supplementary material The online version of this article (10.1186/s13046-019-1273-1) contains supplementary material, which is available to authorized users.

Occult hepatitis B infection and hepatocellular carcinoma: Epidemiology, virology, hepatocarcinogenesis and clinical significance

“…A number of studies performed in the early 80s, based on hybridisation technology, revealed the presence of integrated forms of viral DNA within the host genome of patients with HBsAg-negative HCC. 91 Subsequent studies performed with more advanced molecular approachesin particular, the PCR-based assays and, more recently, the newly developed high-throughput sequencing approaches [92][93][94][95][96] confirmed this observation, and provided further relevant information in terms of possible mechanisms by which HBV (even in the OBI phase) may contribute to hepatocyte transformation. The use of these more sensitive PCR-based methods revealed the presence of integrated HBV genomic sequences in over 60-75% of HCCs from HBsAg-negative patients, 17,94 a prevalence very similar to that reported in HBsAgpositive patients with HCC.…”

Impact of Hepatitis B Virus Genetic Variation, Integration, and Lymphotropism in Antiviral Treatment and Oncogenesis

“…In fact, many cases of cryptogenic HCC (those with no known cause) have been linked to OBI [ 155 , 156 , 157 ]. Studies have demonstrated that oncogenic viral integration is detectable and likely poses a continual risk for malignant transformation of hepatocytes [ 139 , 157 , 158 ]. In addition to HCC and liver disease, reports have suggested that the presence of occult low-level HBV are also associated with extrahepatic and hematological malignancies including leukemia and lymphoma [ 159 , 160 , 161 ].…”

High lymphocyte‑to‑monocyte ratio is associated with low α‑fetoprotein expression in patients with hepatitis B virus‑associated hepatocellular carcinoma

“…The mechanism and clinical implications of oBi are not fully understood. Previous studies have reported that oBi can potentially contribute to acute exacerbation, cirrhosis and Hcc (30)(31)(32). However, oBi prevalence and its natural course in the general population have been insufficiently investigated.…”