Epidemiological Studies on Biliary Tract Cancer in Niigata, Japan

在过去的十年里，人们对胆道癌(BTC)进行了流行病学研究，其原因是我们居住的新泻县的死亡率是日本最高的。本研究是BTC流行病学研究的一部分，其目的是利用动物模型检验多因素因果关系假说。在多因素致病假说的基础上，我们设计了一个方案，给金黄地鼠一种可疑的化学物质氯硝芬(CNP)，这些金黄地鼠的胆囊会发生“实验性胆结石”。共设5个实验组：第1组：胆结石+正常饮食；第2组：胆结石+CNP(5000ppm)；第3组：阳性致癌物，3-甲基胆菲(3-MC)+正常饮食；第4组：3-MC+CNP(5000ppm)；第5组(对照组)：假手术+正常饮食。每组均选用20只雌性金黄地鼠(出生时9~10周)。实验1、2、5组为72周，3、4组为17周。实验2组在实验第17周停止CNP治疗，其余时间给予正常饮食，与对照组相比体重增加，在72周实验过程中，1、2、5组各死亡3只。在第3组和第4组中，17周内无一人死亡。处死时(1、2、5组72周，3、4组17周)，1组和2组分别有1例和2例肝内增生性结节。至于胆囊癌的发生，目前正在进行组织病理学检查，具体结果将在其他地方公布。

Epidemiological studies of biliary tract cancer(BTC) have been conducted over the last decade, the rationale being that the deaths rates in Niigata Prefecture where we live were found to be the highest in Japan. The present study was conducted as a part of the epidemiological studies on BTC.The aim of the present study is to test a multifactorial causation hypothesis by making use of an animal model. In details, we designed a protocol on the basis of multifactorial causation hypothesis where a suspected chemical, chlornitrfen(CNP) is given to golden hamsters whose gallbladders are surgically operated to have "experimental gallstone".Five experimental groups were established as follows ; Group 1 : gallstone + normal diet, Group 2 : gallstone + CNP(5000ppm), Group 3 : positive carcinogen, 3-methylcholanthrene (3-MC) + nomal diet, Group 4 : 3-MC + CNP(5000ppm), Group 5(Control Group) : sham-oparation + nomal diet. Twenty female golden hamsters (9-10 weeks age at the time of initiation were used in each group. The periods of experiments were 72 weeks in the groups of 1,2 and 5, and 17 weeks in the groups of 3 and 4. CNP treatment in the group 2 was stopped at the 17th weeks and normal diet was introduced in the rest of the experimental period, since the body weight increase was affected as compared with the control group.During the course of experiment for 72 weeks in the groups of 1,2 and 5, three animals each were dead. In the groups of 3 and 4, none of them died for 17 weeks. At the time of sacrifice(72 weeks in groups of 1,2 and 5, and 17 weeks in the groups of 3 and 4), 1 and 2 cases of hyperplastic nodules in the liver were found in the groups of 1 and 2, respectively. In regards to the occurence of gallbladder cancer, the histopathological examination was being conducted and the details of the findings will be appeared elsewhere.