Clonal origin of human hepatoma determined by integration of hepatitis B virus DNA

The hepatitis B virus genome is integrated in cellular DNA of human hepatocellular carcinoma from hepatitis B surface antigen-positive patients. Using this phenomenon, we determined the clonal origin of hepatocellular carcinoma from the integration mode of hepatitis B virus DNA. The molecular size and the number of restriction fragments of integrated hepatitis B virus DNA in several parts of tumors in the same liver and in metastatic tumors were compared by Southern blot analysis. Of 14 cases of hepatoma, 13 cases were monoclonal; in one case, a different clone of hepatoma was found in one part of the tumor. In three of 13 cases of monoclonal hepatoma, metastatic tumors in lymph nodes and the lung were also examined and found to be the same clone as the liver tumors. These results indicate that hepatocellular carcinomas were usually generated from a single tumor cell even though tumor cells spread in the liver and invaded other organs for a long time. Development of different clones of tumor was apparently unusual but was observed in one case of hepatocellular carcinoma.