Eimorn Mairiang

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.

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.

Liver fluke infection and cholangiocarcinoma : Model of endogenous nitric oxide and extragastric nitrosation in human carcinogenesis

Cancers arising during bacterial, viral and parasitic infection provide useful models to investigate the link between inflammation and carcinogenesis. Because the inflammatory agent is known, relationships between immune responses, the production of DNA-damaging agents, such as nitric oxide, oxygen radicles and N-nitroso compounds, and cancer risk can be explored. This paper first describes the close relationship between infection with the liver fluke, Opisthorchis viverrini, and cholangiocarcinoma in humans. Data are then presented which demonstrate an elevation in levels of salivary nitrite and urinary and plasma nitrate among men with moderate and heavy liver fluke infections compared to uninfected controls which was absent 4 months after the parasites were cleared with praziquantel. Because of the strict control over subject selection and dietary intake plus the absence of the increase following treatment, we conclude that the higher levels of nitrate and nitrite reflect endogenous generation of nitric oxide resulting from liver fluke infection. Excess nitric oxide generation in the inflamed tissue is likely to lead directly to the formation of N-nitroso compounds mediated by activated macrophages. Further work will attempt to demonstrate a link between this increase and both parasite-specific immune responses and the risk of cancer.

Advanced periductal fibrosis from infection with the carcinogenic human liver fluke Opisthorchis viverrini correlates with elevated levels of interleukin‐6

More than 750 million people are at risk of infection with foodborne liver flukes. Opisthorchis viverrini is considered among the most important of these parasites, due to its strong association with cholangiocarcinoma (CCA). O. viverrini infection results in a chronic inflammatory challenge to the host, which can lead to advanced, pathogen‐specific disease sequelae including obstructive jaundice, hepatomegaly, cholecystitis, as well as CCA. However, before disease sequelae are apparent, important inflammatory changes to the liver can be detected early during O. viverrini infection. In a case‐control study involving 328 men and women with O. viverrini infection, we determined the presence of advanced periductal fibrosis in asymptomatic, O. viverrini‐infected individuals and then measured cytokine responses to O. viverrini excretory/secretory products (ES). In the 200 participants with advanced periductal fibrosis (cases), levels of interleukin‐6 (IL‐6) to O. viverrini ES were 8 times higher than levels of the 128 O. viverrini‐infected individuals without advanced periductal fibrosis (controls). Moreover, elevated IL‐6 to parasite ES was associated with increased risk of advanced periductal fibrosis by 63% in a model adjusted for sex and age. The risk of advanced periductal fibrosis was also found to increase with higher levels of IL‐6: individuals in the third quartile of IL‐6‐ES production had a 127% higher risk of developing advanced periductal fibrosis than individuals in the first quartile of IL‐6 production. O. viverrini‐infected individuals with advanced periductal fibrosis showed other hepatobiliary abnormalities, including reduced gallbladder contractility and the presence of gallbladder sludge. Conclusion: These data strongly implicate a role for parasite‐specific IL‐6 in the pathogenesis of advanced periductal fibrosis in opisthorchiasis, with possible links to other hepatobiliary abnormalities, including CCA. (HEPATOLOGY 2009.)

A high frequency of hepatobiliary disease and suspected cholangiocarcinoma associated with heavy Opisthorchis viverrini infection in a small community in north-east Thailand

A group of 87 adults from a small village in north-east Thailand was chosen to undergo ultrasound investigation based on their intensity of infection with the liver fluke, Opisthorchis viverrini, or clinical status (history of jaundice, current hepatomegaly). From this group, 8 cases of suspected early cholangiocarcinoma were found, and the diagnostic features of 6 of the 8 were confirmed by computerized tomography scan and endoscopic retrograde cholangiopancreatography. In addition, several cases of mild gall-bladder disease, chronic cholecystitis, cholelithiasis and parenchymal liver disease were detected. A highly significant positive relationship between the intensity of liver fluke worm burden and the severity of biliary tract disease within individuals is reported. These results indicate that Opisthorchis is associated with moderate to severe hepatobiliary disease in a considerable proportion of infected individuals.

Relationship between intensity of Opisthorchis viverrini infection and hepatobiliary disease detected by ultrasonography

Twenty‐four locality‐, age‐ and sex‐matched groups of village residents with no light, moderate and heavy Opisthorchis viverrini infection were examined by ultransonography. Highly significant differences were observed between the groups in the relative size of the left lobe of the liver and the fasting and post‐meal size of the gall‐bladder. In addition, indistinct gall‐bladder wall, the presence of gall‐bladder sludge and strongly enhanced portal vein radicle echoes were most frequently observed in the heavily infected group. Two suspected cases of cholangiocarcinoma were identified from the heavy group. The results highlight the importance of intensity of infection on the frequency and severity of fluke‐associated hepatobiliary disease.

Ultrasonography assessment of hepatobiliary abnormalities in 3359 subjects with Opisthorchis viverrini infection in endemic areas of Thailand

A cross sectional study on hepatobiliary abnormalities in opisthorchiasis was performed in 8936 males and females aged from 20 to 60 years from 90 villages of Khon Kaen province, Northeast Thailand. All were stool-examined for Opisthorchis viverrini infection by standard quantitative formalin/ethyl acetate concentration technique. Of these, 3359 participants with stool egg positive underwent ultrasonography of the upper abdomen. The hepatobiliary abnormalities detected by ultrasound are described here. This study found a significantly higher frequency of advanced periductal fibrosis in persons with chronic opisthorchiasis (23.6%), particularly in males. Risks of the fibrosis included intensity of infection, and age younger than 30 years. Height of left lobe of the liver, cross-section of the gallbladder dimensions post fatty meal, sludge, and, interestingly, intrahepatic duct stones were significantly associated with the advanced periductal fibrosis. Eleven suspected cholangiocarcinoma (CCA) cases were observed. This study emphasizes the current status of high O. viverrini infection rate and the existence of hepatobiliary abnormalities including suspected CCA in opisthorchiasis endemic areas of Thailand.

Immune responsiveness and parasite-specific antibody levels in human hepatobiliary disease associated with Opisthorchis viverrini infection.

Opisthorchis viverrini infection is associated with human hepatobiliary disease and cholangiocarcinoma, but the role of the immune response in the pathogenesis of infection is unclear. Here ultrasonography was used to examine the biliary tracts of residents from an endemic community. Delayed‐type hypersensitivity responses to unrelated antigens, and fluke‐specific IgG and IgA levels in serum of this group were also examined. Relationships between immunological parameters, intensity of infection and radiologically measured variables are reported. Immune responsiveness to unrelated antigens did not vary with intensity of parasite infection or disease status. Of all the variables, IgG levels were most markedly elevated in disease cases compared with normal subjects and were closely associated with gall bladder size and dysfunction. This is consistent with the hypothesis that an immunopathologic mechanism is involved in opisthorchiasis and suggests that antibody levels may be useful in screening populations for fluke‐associated hepatobiliary disease.

Biliary parasitic diseases including clonorchiasis, opisthorchiasis and fascioliasis

AbstractParasitic infection of the biliary tree is caused by liver flukes, namely Clonorchis sinensis and Opisthorchis viverrini. These flukes reside in the peripheral small bile ducts of the liver and produce chronic inflammation of the bile duct, bile duct dilatation, mechanical obstruction, and bile duct wall thickening. On imaging, peripheral small intrahepatic bile ducts are dilated, but the large bile ducts and extrahepatic bile ducts are not dilated or slightly dilated. There is no visible caused of obstruction. Sometimes, in heavy infection, adult flukes are demonstrated on sonography, CT or MR cholangiography as small intraluminal lesions. The flukes in the gallbladder may appear as floating, small objects on sonography. Chronic infection may result in cholangiocarcinoma of the liver parenchyma or along the bile ducts. Human infection of Fasciola hepatica, a cattle flukes, may occur inadvertently, and the flukes migrate in the liver (hepatic phase) and reside the bile ducts (biliary phase). Image findings in the hepatic phase present with multiple, small, clustered, necrotic cavities or abscesses in the peripheral parts of the liver, showing “tunnels and caves” sign, reflecting parasite migration in the liver parenchyma. In the biliary phase, the flukes are demonstrated in the intra- and extrahepatic bile ducts and the gallbladder as small intraluminal flat objects, sometimes moving spontaneously. Bile ducts are dilated.