亚硝胺对人食管上皮中癌基因的作用

ALTERATIONS OF ONCOGENES IN HUMAN FETAL ESOPHAGEAL EPITHELIUM INDUCED BY N METHYLBENZYLNITROSAMINE(NMBzA)

用甲基苄基亚硝胺（ＮＭＢｚＡ）诱导胎儿食管上皮（ＨＦＥ）组织，通过Ｓｏｕｔｈｅｒｎ杂交和免疫组织化学分析发现：ＮＭＢｚＡ诱导２４小时的ＨＦＥ中即有ＥＧＦｒ基因的扩增和高表达；随着诱导时间的延长，在ＮＭＢｚＡ诱导１周和３周的ＨＦＥ中分别发现ｃ—ｍｙｃ和ｉｎｔ—２基因的扩增，组织学观察可发现这些组织中有局部乳头状增生；在ＮＭＢｚＡ诱导的胎儿食管上皮癌中发现Ｒｂ基因的完全丢失及Ｐ５３基因的部分丢失和高表达。将ＮＭＢｚＡ体外诱导３周的ＨＦＥ组织接种至裸鼠体内，连续观察５个月未发现接种处有肿瘤形成，病理切片亦未找到恶性细胞。提示仅有ＥＧＦｒ、ｃ—ｍｙｃ或ｉｎｔ—２等少数几种癌基因的改变尚不足以导致食管癌完全恶性状态的形成，食管癌的最后形成可能还需Ｐ５３和Ｒｂ等抗癌基因的丢失和失活。

Abstract Epidemiological investigation showed that N methylbenzylnitrosamine(NMBzA)has been associ-ated with increased incidence of esophageal cancer(EC)in Linxian count,a high incidence area.In present study, our results indicate that NMBzA acn induce amplification and and over-expression ofEGFr gene in human fetal esophageal epithelium (HFE) treated with NMBzA for 24 hours as shown by southern blot assay and immunohistochemistry. The papillary hyperplasia was induced in HFEs that cultured with NMBzA for l to 3 weeks, Amplification of c myc and int 2 gene inHFEs treated by NMBzA for 1 week 3 weeks was found, respectively ,Deletions of P53 and Rb gene were found in human fetal esophagcal careinomas induced by NMBzA. Overexprssion of p53 protein in humanfetal esophageal carcinomas detectedk by immunohistochemical methods indi-cates that p53 gene mutation(s)may be occured , The HFE explants treated in vitro with NMBzAfor 3 weeks were inoculated subcutanously into balb/c nude mice . No tumor was found in 5 monthsafter inoculation,suggesting that only changes of oncogene(s)are insufficient to induce fulltransformation. Other genetic alterations (such as functional inactivation of Rb or/and p53 tumorsuppressor genes) may be necessary in the further progression of malignant lesions