Infection with the food-borne liver fluke parasites Opisthorchis viverrini and Clonorchis sinensis is a strong risk factor for cholangiocarcinoma (CCA), bile duct cancer, in Thailand, Laos and other locations in East Asia where infection is endemic. As determined by the World Health Organization's International Agency for Research on Cancer, no stronger link exists between human malignancy and a eukaryotic pathogen than that of CCA and liver fluke infection. CCA usually presents late, is a challenge for diagnosis, metastasizes readily and has high mortality - features highlighting the necessity to understand why and how infection with a food- borne parasite leads to a devastating liver cancer. The transformation from chronic infection with O. viverrini to CCA is multi-factorial, but one importan factor appears to be secretion into the bile ducts of parasite proteins with mitogenic properties, driving local proliferation of biliary and hepatic cells and creating a tumorigenic environment. We have identified a homologue of human granulin, a potent growth factor involved in cell proliferation and wound healing, in the excretory/secretory (ES) products of the parasite. O. viverrini granulin, termed Ov-GRN-1, is widely expressed in fluke tissues, including gut and tegument. Furthermore, Ov-GRN-1 locates in situ to the surface of biliary epithelial cells of hamsters experimentally infected with O. viverrini. Recombinant Ov-GRN-1 stimulates proliferation of murine fibroblasts and human CCA cell lines at nanomolar concentrations that can be inhibited by MAPK kinase inhibitors. Antibodies to Ov-GRN-1 inhibited the ability of O. viverrini ES products to induce proliferation of mammalian cell lines in vitro, indicating that Ov-GRN-1 is the major growth factor present in O. viverrini ES. This was the first report of a secreted growth factor from a parasitic worm that induces proliferation of host cells. Significantly, these new findings support a role for this fluke protein in establishment of a tumorigenic environment that may ultimately manifest as CCA. Here we plan to test this hypothesis with a particular emphasis on the role of Ov-GRN-1 in cell cycle progression and wound repair. We propose also to characterize transcriptional and translational responses of cholangiocytes and CCA cell lines to Ov-GRN-1 using proteomic and genomic microarray approaches to understand signaling and other pathways by which liver fluke granulin drives host cell proliferation. In addition, we propose to use gene silencing and vaccination of hamsters to determine whether Ov-GRN-1 is the major, or even sole, growth factor secreted by the parasite. These studies will determine whether Ov-GRN-1 is the Achilles' heel of this parasite that could be exploited as an anti-fluke and indeed anti-cancer vaccine.
Long term infection with liver fluke - a food-borne parasitic worm - leads to cholangiocarcinoma (CCA), a form of liver cancer with a dismal prognosis. We have identified a protein from these parasites that may cause this cancer. Here we propose to investigate the role of this parasite protein (termed granulin) in cancer, which may lead to new treatments and control for fluke infection and CCA.
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