The tree shrews: useful animal models for the viral hepatitis and hepatocellular carcinoma

Hepatitis B virus (HBV)-induced hepatitis and hepatocellular carcinoma (HCC) are major diseases worldwide. HBV infection and chemical carcinogens such as aflatoxin B1 are known to be two key factors in the development of HCC. Animal models for hepatitis and HCC are very useful in the in vivo studies of mechanism involved in the development and prevention of these diseases and the pre-clinical research of drugs for the treatment of these diseases. Now, several animals, such as woodchucks, ground squirrels, chimpanzees, ducks and tree shrews, have been used to establish hepatitis and HCC models. HCC occurs in some woodchucks and ground squirrels that are infected with their own hepatitis viruses and exposed to carcinogens. Chimpanzees and ducks can be infected with human and duck hepatitis B viruses, respectively, but HCC is rarely observed in these animals. The tree shrews are non-rodent, small animals and close to primates in evolution. This review focuses on the establishment of human HBV-induced hepatitis and human HBV-associated HCC in tree shrews and their applications in the study of HCC development.