Hepatitis B virus-related intrahepatic cholangiocarcinoma originates from hepatocytes.

Background: Hepatitis B virus (HBV) infection is one of the most common risk factors for intrahepatic cholangiocarcinoma (ICC). However, there is no direct evidence of a causal relationship between HBV infection and ICC. In this study, we attempted to prove that ICC may originate from hepatocytes through a pathological study involving ICC tissue-derived organoids.

Method: The medical records and tumor tissue samples of 182 patients with ICC after hepatectomy were collected. The medical records of 182 patients with ICC were retrospectively analyzed to explore the prognostic factors. A microarray of 182 cases of ICC tumor tissue and 6 cases of normal liver tissue was made, and HBsAg was stained by immunohistochemistry (IHC) to explore the factors closely related to HBV infection. Fresh ICC tissues and corresponding adjacent tissues were collected to make paraffin sections and organoids. Immunofluorescence (IF) staining of factors including HBsAg, CK19, CK7, Hep-Par1 and Albumin (ALB) was performed on both fresh tissues and organoids. In addition, we collected adjacent nontumor tissues of 6 patients with HBV (+) ICC, from which biliary duct tissue and normal liver tissue were isolated and RNA was extracted respectively for quantitative PCR assay. In addition, the expression of HBV-DNA in organoid culture medium was detected by quantitative PCR and PCR electrophoresis.

Results: A total of 74 of 182 ICC patients were HBsAg positive (40.66%, 74/182). The disease-free survival (DFS) rate of HBsAg (+) ICC patients was significantly lower than that of HBsAg (-) ICC patients (p = 0.0137). IF and IHC showed that HBsAg staining was only visible in HBV (+) ICC fresh tissues and organoids, HBsAg expression was negative in bile duct cells in the portal area. Quantitative PCR assay has shown that the expression of HBs antigen and HBx in normal hepatocytes were significantly higher than that in bile duct epithelial cells. Combined with the IF and IHC staining, it was confirmed that HBV does not infect normal bile duct epithelial cells. In addition, IF also showed that the staining of bile duct markers CK19 and CK7 were only visible in ICC fresh tissue and organoids, and the staining of hepatocyte markers Hep-Par1 and ALB was only visible in normal liver tissue fresh tissue. Real-time PCR and WB had the same results. High levels of HBV-DNA were detected in the culture medium of HBV (+) organoids but not in the culture medium of HBV (-) organoids.

Conclusion: HBV-related ICC might be derived from hepatocytes. HBV (+) ICC patients had shorter DFS than HBV (-) ICC patients.