Epidemiologic Study of Cancer in Koreans in Japan

为了弄清日本韩国人患肝癌风险高的原因，我们开展了流行病学研究，同时重点研究了3组丙型肝炎病毒（HCV）基因型和细胞色素P-450 2E1 （CYP2E1）基因型的分布，以及HCV和CYP2E1基因型与肝细胞癌（HCC）发生的关系；在韩国的韩国人，在日本的韩国人，在日本的日本人。HCV基因3型在韩国人的HCC患者和献血者中普遍存在。另一方面，HCV基因2型在日本人和韩国人的HCC患者和献血者中普遍存在。因此，在日本的韩国人表现出与日本人相似的HCV基因型分布。接下来，我们在大阪癌症和心血管疾病医学中心和大阪大学进行了HCC发展与HCV基因型之间关系的病例对照研究。因此，发现HCV基因型2比HCV基因型3和4有更高的发生肝硬化和HCC的风险。CYP2E1是唯一能代谢n -亚硝基二甲胺的酶，n -亚硝基二甲胺是一种强效的肝癌致癌物。CYP2E1基因型与个体对二乙亚硝胺诱导的肝癌的易感性有关，并且观察到这种易感性在长期给药乙醇的情况下会加速。CYP2E1基因型在韩国和日本HCC患者中的分布没有差异。CYP2E1基因型c1/c2和c1/c2发生HCC的风险略高于CYP2E1基因型c1/c1，但差异无统计学意义。总之，HCV基因2型在日本的韩国人中普遍存在，因此可能在他们患HCC的风险增加中起作用。

In order to clarify the reasons why Koreans in Japan demonstrate a high risk for developing liver cancer, we have been carrying out epidemiological studies, while focusing on the distribution of hepatitis C virus (HCV) genotypes and cytochrome P-450 2E1 (CYP2E1) genotypes, and the relationships between the development of hepatocellular carcinoma (HCC) and the genotypes to HCV and CYP2E1 among 3 groups ; Koreans in Korea, Koreans in Japan and Japanese in this 3-year Korea-Japan Joint Study.HCV genotype 3 was found to be prevalent among HCC patients and blood donors of Koreans in Korea. On the other hand, HCV genotype 2 was prevalent among both HCC patients and blood donors of both Japanese and Koreans in Japan. Koreans in Japan thus demonstrated a similar distribution of HCV genotypes to that lof Japanese.We next conducted a case-control study on the association between the development of HCC and HCV genotypes at the Osaka Medical Center for Cancer and Cardiovascular Diseases, and Osaka University. As a result, HCV genotype 2 was found to show a higher risk for the development of liver cirrhosis and HCC than HCV genotypes 3 and 4.CYP2E1 is the only enzyme that metabolizes N-nitrosodimethylamine, a potent hepatocarcinogen. CYP2E1 genotype is related to individual susceptibility to diethlnitrosamine-induced liver cancer, and this susceptibility was observed to be accelerated by long-term administration of ethanol.No difference was observed in the distribution of CYP2E1 genotypes between HCC Koreans and Japanese patients. CYP2E1 genotype c1/c2 and c1/c2 showed a somewhat higher risk for the development of HCC than CYP2E1 genotype c1/c1, but the difference was not statistically significant.In conclusion, HCV genotype 2 was prevalent among Koreans in Japan, which may thus play a role in their increased risk for developing HCC.