Banchob Sripa

Liver Fluke Induces Cholangiocarcinoma

The authors discuss the molecular pathogenesis of opisthorchiasis and associated cholangiocarcinogenesis, particularly nitrative and oxidative DNA damage and the clinical manifestations of cholangiocarcinoma.

Cholangiocarcinoma: Lessons from Thailand

Purpose of review To present the background of liver fluke-associated cholangiocarcinoma in Thailand focusing on recent epidemiological data and pathogenesis of this bile duct cancer. Recent findings More systematic tumor registration in Thailand nowadays uncovers new high-incidence areas that are confined to not only the northeastern part but also some provinces in northern Thailand. The link between the liver fluke, Opisthorchis viverrini, and cholangiocarcinoma, particularly in terms of cellular and molecular pathogenesis, is further elucidated. Summary Thailand is still the country with the highest incidence of cholangiocarcinoma in the world. Liver fluke induces chronic inflammation leading to oxidative DNA damage of the infected biliary epithelium and malignant transformation. Eradication of the fluke and identification of high-risk populations are urgently needed.

Epidemiology of cholangiocarcinoma: an update focusing on risk factors.

(Cancer Sci 2010; 101: 579–585)

Exome sequencing of liver fluke-associated cholangiocarcinoma

Opisthorchis viverrini–related cholangiocarcinoma (CCA), a fatal bile duct cancer, is a major public health concern in areas endemic for this parasite. We report here whole-exome sequencing of eight O. viverrini–related tumors and matched normal tissue. We identified and validated 206 somatic mutations in 187 genes using Sanger sequencing and selected 15 genes for mutation prevalence screening in an additional 46 individuals with CCA (cases). In addition to the known cancer-related genes TP53 (mutated in 44.4% of cases), KRAS (16.7%) and SMAD4 (16.7%), we identified somatic mutations in 10 newly implicated genes in 14.8–3.7% of cases. These included inactivating mutations in MLL3 (in 14.8% of cases), ROBO2 (9.3%), RNF43 (9.3%) and PEG3 (5.6%), and activating mutations in the GNAS oncogene (9.3%). These genes have functions that can be broadly grouped into three biological classes: (i) deactivation of histone modifiers, (ii) activation of G protein signaling and (iii) loss of genome stability. This study provides insight into the mutational landscape contributing to O. viverrini–related CCA.

The tumorigenic liver fluke Opisthorchis viverrini – multiple pathways to cancer

Liver fluke infection caused by Opisthorchis viverrini is a major public health problem in Thailand and adjacent countries. In addition to infection-associated morbidity, infection with O. viverrini and the related Clonorchis sinensis are unarguable risk factors for cholangiocarcinoma (CAA, bile-duct cancer). Here we review the pathogenesis of opisthorchiasis and the association between O. viverrini infection and bile-duct cancer, focusing on the molecular parallels between wound healing, chronic inflammation, and cancer development. We review a schema for human disease progression from fluke infection, chronic opisthorchiasis, advanced periductal fibrosis, and cholangiocarcinogenesis, and present a rationale for biomarker discovery to facilitate early intervention. We conclude by addressing post-genomic advances with a view to developing new control strategies to combat this infectious cancer.

Opisthorchiasis and Opisthorchis-associated cholangiocarcinoma in Thailand and Laos

Liver fluke infection caused by Opisthorchis viverrini is a major public health problem in Thailand and the Lao Peoples Democratic Republic (Lao PDR; Laos). Currently, more than 600 million people are at risk of infection with these fish-borne trematodes and/or their close relatives. Opisthorchiasis has been studied extensively in Thailand, where about 8 million people are infected with the liver fluke. Here we review the pathogenesis, control and re-emergence of O. viverrini infection, in particular in Thailand and, to a lesser extent in Lao PDR given the contiguous geographical range of O. viverrini through these two regions. We also review the association of O. viverrini infection and cholangiocarcinoma, bile duct cancer, and highlight new findings on pathogenesis of liver fluke-induced cholangiocarcinogenesis. Last, we comment on national control strategies in Thailand for the control of O. viverrini infection aimed at reduction in the prevalence of O. viverrini-associated liver cancer in the longer term.

A Research Agenda for Helminth Diseases of Humans: Intervention for Control and Elimination

Recognising the burden helminth infections impose on human populations, and particularly the poor, major intervention programmes have been launched to control onchocerciasis, lymphatic filariasis, soil-transmitted helminthiases, schistosomiasis, and cysticercosis. The Disease Reference Group on Helminth Infections (DRG4), established in 2009 by the Special Programme for Research and Training in Tropical Diseases (TDR), was given the mandate to review helminthiases research and identify research priorities and gaps. A summary of current helminth control initiatives is presented and available tools are described. Most of these programmes are highly dependent on mass drug administration (MDA) of anthelmintic drugs (donated or available at low cost) and require annual or biannual treatment of large numbers of at-risk populations, over prolonged periods of time. The continuation of prolonged MDA with a limited number of anthelmintics greatly increases the probability that drug resistance will develop, which would raise serious problems for continuation of control and the achievement of elimination. Most initiatives have focussed on a single type of helminth infection, but recognition of co-endemicity and polyparasitism is leading to more integration of control. An understanding of the implications of control integration for implementation, treatment coverage, combination of pharmaceuticals, and monitoring is needed. To achieve the goals of morbidity reduction or elimination of infection, novel tools need to be developed, including more efficacious drugs, vaccines, and/or antivectorial agents, new diagnostics for infection and assessment of drug efficacy, and markers for possible anthelmintic resistance. In addition, there is a need for the development of new formulations of some existing anthelmintics (e.g., paediatric formulations). To achieve ultimate elimination of helminth parasites, treatments for the above mentioned helminthiases, and for taeniasis and food-borne trematodiases, will need to be integrated with monitoring, education, sanitation, access to health services, and where appropriate, vector control or reduction of the parasite reservoir in alternative hosts. Based on an analysis of current knowledge gaps and identification of priorities, a research and development agenda for intervention tools considered necessary for control and elimination of human helminthiases is presented, and the challenges to be confronted are discussed.

Genetic and environmental determinants of risk for cholangiocarcinoma via Opisthorchis viverrini in a densely infested area in Nakhon Phanom, northeast Thailand

Infection with Opisthorchis viverrini (OV) is associated with cholangiocarcinoma. OV is common in northeast Thailand, but less than 10% of the inhabitants develop cholangiocarcinoma. Animal experiments suggest that OV infection alone does not cause cholangiocarcinoma, and thus other environmental and genetic factors may play a role in causation. We conducted a population‐based case‐control study in which sex, age and place of residence were matched individually. Polymorphisms of GSTM1 and GSTT1 alone were not associated with risk for cholangiocarcinoma, while an elevated level of antibodies against OV (ELISA) ≥0.200 was the strongest risk indicator (odds ratio as compared to that <0.200 = 27.09 [95% confidence interval (CI): 6.30–116.57]. Compared to subjects who had a normal antibody range and the wild‐type GSTM1 gene, those who had elevated antibodies had higher odds ratios of 12.32 (95% CI: 1.60–94.85) for wild‐type GSTM1 and 23.53 (95% CI: 4.25–130.31) for the null variant thereof, respectively. Past and current regular drinkers of alcohol had higher risk [odds ratio = 5.39 (95% CI: 1.11–26.06) and 4.82 (95% CI: 1.29–18.06), respectively]. Eating fermented products was an independent risk factor. Smokers or consumers of fermented fish had substantially increased risk if they were past or current drinkers. Infection with OV correlates strongly with cholangiocarcinoma, susceptibility to which may be possibly associated with GSTM1 polymorphism. Alcohol may affect metabolic pathways of endogenous and exogenous nitrosamines.

Localisation of parasite antigens and inflammatory responses in experimental opisthorchiasis.

The time course localisation of parasite antigens and related host pathology were studied in hamsters infected with 100 metacercariae of Opisthorchis viverrini for up to 6 months. Parasite antigens, as detected by immunofluorescence and/or immunoperoxidase-staining, were first observed in the flukes and the biliary epithelium of the intrahepatic and extrahepatic bile ducts as early as day 3 p.i. Antigens increased as the parasite matured, both in tissues in direct contact with the flukes and those surrounding the infection. Opisthorchis antigens were also observed in the first order bile ducts (small bile ducts) of the liver, which are not normally inhabited by flukes. In addition, they were found in damaged liver cells, Kupffer cells, macrophages, and within epithelioid and giant cells in the egg granuloma. The presence of the antigens was associated with heavy inflammatory cell infiltration, particularly with mononuclear cells. The results strongly support the role of fluke-associated antigens and local parasite-specific immune responses in the pathogenesis of opisthorchiasis.

Unlocking the Transcriptomes of Two Carcinogenic Parasites, Clonorchis sinensis and Opisthorchis viverrini

The two parasitic trematodes, Clonorchis sinensis and Opisthorchis viverrini, have a major impact on the health of tens of millions of humans throughout Asia. The greatest impact is through the malignant cancer ( = cholangiocarcinoma) that these parasites induce in chronically infected people. Therefore, both C. sinensis and O. viverrini have been classified by the World Health Organization (WHO) as Group 1 carcinogens. Despite their impact, little is known about these parasites and their interplay with the host at the molecular level. Recent advances in genomics and bioinformatics provide unique opportunities to gain improved insights into the biology of parasites as well as their relationships with their hosts at the molecular level. The present study elucidates the transcriptomes of C. sinensis and O. viverrini using a platform based on next-generation (high throughput) sequencing and advanced in silico analyses. From 500,000 sequences, >50,000 sequences were assembled for each species and categorized as biologically relevant based on homology searches, gene ontology and/or pathway mapping. The results of the present study could assist in defining molecules that are essential for the development, reproduction and survival of liver flukes and/or that are linked to the development of cholangiocarcinoma. This study also lays a foundation for future genomic and proteomic research of C. sinensis and O. viverrini and the cancers that they are known to induce, as well as novel intervention strategies.