Experimental investigation of opisthorchiasis-associated cholangiocarcinoma induction in the Syrian hamster - pointers for control of the human disease.

Appropriate animal models for specific diseases in man can facilitate elucidation of mechanisms underlying tumour development and allow potential interventions and therapeutic regimens to be tested in vivo before consideration for use in the human situation. In the North-east of Thailand exceptionally high levels of cholangiocellular carcinomas (CCCs) are encountered, related to infestation with Opisthorchis viverrini liver flukes. The Syrian hamster can also be infected with metacercariae of the fluke and heavy loads of parasites cause the development of cirrhotic livers. While the presence of flukes alone does not give rise to neoplasms, large yields of cholangiofibrotic lesions and CCCs can be readily induced with additional carcinogenic insult. While removal of the parasite with the antihelminthic drug Praziquantel can protect against carcinogenesis, this is dependent on the timing of the drug administration and the efficacy of application to the human situation remains to be confirmed. The available information would suggest that interest needs to be concentrated on potential chemopreventive agents which could be administered to individuals at high risk. Furthermore, understanding of the genesis of CCCs and the characteristics of preneoplastic lesions, again as assessed in the animal model, might allow novel approaches to identification of early stage cases and effective surgical intervention.