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Highlights of topic “Etiology and epidemiology of cholangiocarcinoma”

Cholangiocarcinoma (CCA) is one of the representative cancers refractory to any therapeutic approach. Since CCA develops and progresses towards malignancy with multiple steps like many other human cancers, elucidation of the biological and molecular characteristics in each step is important for prevention, early diagnosis and early treatment of CCA. For this purpose, it would be quite useful to compare CCA in Thailand, which is associated with the infection of a liver fluke, Opisthorchis viverrini (Ov), with that in Japan without association of Ov-infection. As the first topic of a series of review articles on CCA, this issue focuses on the etiological analyses of the multistep tumorigenesis of CCA and its application to prevention, paying special attention to Ov-infection. On the other hand, the current topic on cholangiocarcinoma triggered by chemical agents among offset color proof-printing workers is not included in this review because the critical issues of the study have not been published yet. Readers are recommended to follow the topic of this occupational CCA by original papers to be published soon. The first article by Sithithaworn et al. [1] describes the roles of liver fluke infection as risk factors for CCA from the view point of parasitology and epidemiology. In addition to the well summarized knowledge of the pathobiology of Ov and the incidence of Ov-infection and CCA, readers will understand the impact of the challenge to control Ov-infection that were started about 30 years ago in northeast Thailand by public health education and mass drug administration in decreasing the incidence of CCA in the several recent years (Figs 1,2). Primary prevention of CCA by Ov-control is really the most ideal approach to overcome CCA in the endemic area in Thailand. The second article by Yongvanit et al. [2] summarizes the potential biomarkers for the risk assessment of CCA in the carriers of Ov-infection and the challenge for chemoprevention. Based on the privilege of investigating the early stages of CCA using a unique hamster model of CCA with Ov-infection that the authors themselves have established, the authors demonstrate the critical roles of the oxidative stress induced by Ov-infection. Readers will learn a series of alterations caused by oxidative stress, such as periductal fibrosis in histopathology and altered gene expression in molecular profiling, as potential biomarkers for risk assessment of CCA. Although Ov-infection is a serious risk factor of CCA, it also provides important information about the high risk population of CCA development to be followed up by various medical approaches. The third article by Chamadol et al. [3] reports the ongoing projects in Khon Kaen Y. Murakami (*) Division of Molecular Pathology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan e-mail: ymurakam@ims.u-tokyo.ac.jp Fig. 1 Temporal profile of Opisthorchis viverrini in northeast Thailand