Liver Flukes and Cancer - Research Reveals How Opisthorchis viverrini May Cause Liver Cancer

Posted by Rosemary Drisdelle Oct 22, 2009

It’s long been suspected that various flukes play a role in the development of cancers in people who harbor the parasites. Schistosoma haematobium, Clonorchis sinensis, and Opisthorchis viverrini have all been implicated. Charlatans have capitalized on the association claiming that flukes are the cause of all cancers and offering treatment—a myth with barely a grain of truth: parasites account for a very small percentage of cancers (Parkin, 3030), and we are only beginning to learn how they might do it. A paper published in PLoS Pathogens (Smout, Laha, Mulvenna et al) reports on the detection of carcinogenic protein secreted by O. viverrini.

Millions of people in Southeast Asia, notably in Thailand and Laos harbor O. viverrini in the bile ducts of the liver, acquired from raw fish in the diet. A surprising number of those infected eventually develop liver cancer—theoretically the result of a combination of inflammation, dietary nitrosamines (found in foods that contain nitrates or nitrites), and a mitogen (something secreted by the fluke that causes cell division). Smout and colleagues think that they have found the mitogen.

Opisthorchis viverrini secretes a protein called granulin, which is then found both on and in the cells of the bile duct around the parasite. A similar protein found in humans is associated with cell division and the spread of cancer cells in a number of aggressive human cancers. Similarly, the granulin from the fluke causes cell proliferation, making it more likely that a tumor will form in the bile duct. The authors speculate that this cell proliferation might benefit the parasite either by providing it with additional food, or by helping to heal the damage feeding does to the bile duct.

The authors suggest that it might be possible to develop a vaccine to the granulin produced by O. viverrini to reduce the health impact of the parasite in areas where it is prevalent. Perhaps this discovery will lead to similar findings for other flukes associated with cancer.

“A Granulin-Like Growth Factor Secreted by the Carcinogenic Liver Fluke, Opisthorchis viverrini, Promotes Proliferation of Host Cells.” (2009) Smout MJ, Laha T, Mulvenna J, Sripa B, Suttiprapa S, et al. PLoS Pathogens 5(10): e1000611. doi:10.1371/journal.ppat.1000611

“The Global Health Burden of Infection-associated Cancers in the Year 2002.” (2006) Parkin, Donald Maxwell. International Journal of Cancer: 118, 3030–3044