食管癌Rb基因启动子甲基化状态和甲基苄基亚硝胺对其影响的研究

Study on the status of methylation of Rb gene promoter in human esophageal cancer and effect of NMBzA on Rb gene promoter in monkey esophageal epithelium

目的分析Ｒｂ基因表达异常原因，研究Ｒｂ基因启动子甲基化状态和甲基苄基亚硝胺（ＮＭＢｚＡ）对Ｒｂ基因启动子的影响。方法采用限制性核酸内切酶酶切和ＰＣＲ扩增方法。结果３３．３％的食管癌组织Ｒｂ基因启动子存在ＭｓｐⅠ型高甲基化，４０．０％的食管癌组织Ｒｂ基因启动子存在ＨｐａⅡ型高甲基化。１例标本存在ＭｓｐⅠ和ＨｐａⅡ两种类型的高甲基化。恒河猴１次灌喂３０ｍｇ／ｋｇＮＭＢｚＡ后１，２，３天，其食管上皮Ｒｂ基因启动子ＨｐａⅡ、ＭｓｐⅠ类型甲基化逐渐增强；第５天其Ｒｂ基因启动子ＨｐａⅡ、ＭｓｐⅠ类型甲基化程度明显下降。结论食管癌组织中Ｒｂ基因表达异常可能与启动子高甲基化有关，ＮＭＢｚＡ通过启动子甲基化对Ｒｂ基因调控产生影响。

Objective To elucidate the cause of abnormal Rb expression in esophageal cancer (EC). Methods Methylation of Rb gene promoter was examined with restriction endonuclease digestion and PCR amplification. Results Of the 30 specimens of EC, 10 (33.3%) had MspⅠ type hypermethylation of the Rb gene promoter while 12 (40.0%) had HpaⅡ type hypermethylation and one had both type of hypermethylation. In monkey fed with a single dose of NMBzA (30 mg/kg) on day 0, increasing hypermethylation of both types of the Rb gene promoter in esophageal epithelium was found on day 1,2 and 3 but reduced on day 5. Conclusion These data suggest that abnoromal expression of Rb gene may be related to hypermethylation of its promoter and carcinogen NMBzA can induce such hypermethylation in monkey esophageal epithelium.