Study for inactivation mechanism of tumor-associated genes in sporadic colorectal cancers

散发性结直肠癌肿瘤相关基因失活机制研究

基本信息

批准号：
13671348
负责人：
HEMMI Hiromichi
金额：
$ 2.3万
依托单位：
TOHO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13671348/
关键词：
DNA mismatch repair genes hMLH1 gene hMSH2 gene histone acetylation transcription factor colorectal cancer cell lines ミスマッチ修復遺伝子ヒストンH4 転写活性アセチル化状態

项目摘要

Accumulation of mutations in oncogenes and tumor suppressor genes is essential for generation of colorectal cancer. Defect of a DNA mismatch repair (MMR) gene is known to be responding to one of the accumulated mutations in these cancer-related genes. Seven human MMR genes including hMLH1 and hMSH2 have been identified. More than half of most HNPCC and certain fraction of sporadic colorectal cancers shows abnormality in the hMLH1 and hMSH2 genes. An epigeneic modification, namely hypermethylation, in the promoter region of the hMLH1 gene has been demonstrated as one of mechanisms of gene inactivation. Since we had inactivated sporadic cases without mutation in the gene nor hypermethylation, we looked for the another mechanism of inactivation. In this study, we focused two points: one is relationship between histone acetylation status and expression of hMLH1 and hMSH2; second is a regulatory mechanism of the hMLH1 gene expression.1) Acetylation status of the hMLH1 gene promoter in human colorectal cancer cell lines was examined by a ChIP method using anti histone H4 antibody. There was no correlation between protein expression and the acetylation status. However, TSA, an inhibitor of the deacetylation enhanced gene expression, indicating that acetylation enhances the expression.2) Essential sites in the promoter region of the hMLH1 gene for transcription has been identified. Then, we screened factors binding to the one of the essential sites by a yeast one-hybrid system. As on candidate, p29 protein, of which gene located in 1p31-32 where known to be frequent loss in colorectal cancer, has been found. The detailed investigation for the role and function of p29 are required in future.

肿瘤基因和肿瘤抑制基因中突变的积累对于结直肠癌的产生至关重要。已知DNA不匹配修复（MMR）基因的缺陷正在响应这些与癌症相关基因中的累积突变之一。已经确定了七个人类MMR基因，包括HMLH1和HMSH2。大多数HNPCC的一半以上，一定比例的零星结直肠癌在HMLH1和HMSH2基因中表现出异常。在HMLH1基因的启动子区域中，一种表观态度的修饰，即高甲基化，已被证明是基因失活的机制之一。由于我们灭活了零星病例，而没有突变的基因或高甲基化，因此我们寻找了一种灭活的机制。在这项研究中，我们重点是两个点：一个是组蛋白乙酰化状态与HMLH1和HMSH2的表达之间的关系。第二是HMLH1基因表达的调节机制。1）使用抗组蛋白H4抗体的芯片方法检查了人结直肠癌细胞系中HMLH1基因启动子的乙酰化状态。蛋白质表达与乙酰化状态之间没有相关性。然而，TSA是脱乙酰化增强基因表达的抑制剂，表明乙酰化增强了表达。2）已鉴定出HMLH1基因启动子区域的必需位点进行转录。然后，我们通过酵母单杂交系统筛选了与必需位点结合的因素。与候选者一样，已经发现了p29蛋白，其中p29蛋白位于1p31-32中，已知在结直肠癌中经常丧失。将来需要对P29的作用和功能进行详细研究。