【作者】 常志伟；

【导师】 王立东；

【作者基本信息】 郑州大学 ， 消化内科， 2005， 硕士

【摘要】 食管癌(Esophageal Cancer,EC)是世界上最常见的六大恶性肿瘤之一,而中国北方地区特别是河南省林州市(原林县)是中国乃至世界上食管癌发病率最高的地区之一。食管癌突出的流行病学特征是明显的家族聚集现象。早在70年代末对林州地区的食管癌遗传流行病学调查发现林州地区食管癌存在非常明显的家族聚集现象,食管癌高发家族成员患食管癌的危险性要远高于当地居民,且与食管癌患者血缘关系越近遗传度越大。这些现象提示遗传因素可能在食管癌发生中起重要作用。 为什么在同一地区相同生活习惯下只有少数人患食管癌?为什么有些家族中食管癌发生率明显高于其它家族?目前食管癌高发家族成员食管癌高易感性的分子基础仍不清楚。以往的研究表明高发区食管癌高发家族成员食管癌高易感性可能与染色体不稳定(特别是脆性位点)和DNA损伤修复功能异常有关。脆性位点与肿瘤发生的关系密切,它的特征为该处序列高度易变,稳定性低。在肿瘤中经常频发染色体的异常改变,而脆性部位常常位于异常改变处或附近,可能会诱发该处基因重排,断裂和缺失,这可能为相应部位抑癌基因失活或癌基因激活的发生机制之一。脆性组氨酸三联体基因(fragile histidine triad gene,FHIT)是一个已经确定的抑癌基因,所定位的3号染色体3P14.2处包含人类基因组最更多还原

【Abstract】 Esophageal cancer (EC) is one of the six most common malignant diseases worldwide, and is particularly prevalent in northern China. A remarkable epidemiological characteristic for EC is the dramatic familial aggregation. Several genetic epidemiology surveys have demonstrated that there is evident familial aggregation in Linzhou city or other high-incidence areas for EC; and the members in EC aggregation families (ECAF) have higher risk than the members in sporadic EC families (SECF), and the descendants with positive EC history have even higher tumor liability than those with negative EC history. These studies suggest that genetic factors may play an important role in esophageal carcinogenesis, and especially in those from EC aggregation families.The molecular mechanism underlying the familial aggregation for EC is not clear.Studies in the past decades have indicated that the familial EC liability may be related with the chromosome instability (especially fragile sites) and the disfunction of the DNA damage repair. The gene rearrangement, fragmentation and deletion occur frequently in these fragile sites in human malignant diseases. These fragile sites usually contain tumor suppressor genes or oncogenes, which may be the key molecular basis for human carcinogenesis. The detection rate of the fragile sites of the members in ECAF was obviously higher than these in SECF. There was a close relationship between the fragile sites (especially common fragile sites) and the familial EC liability. In some DNA repair-deficiency tumors, such as breast cancer and large intestine carcinoma, abnormal expression of FHIT obviously step up. Besides, in some cell lines with repair-deficiency, the chromosome breaks have been observed obviously to frequently generate, which indicate that the DNA repair-deficiency may contribute to the chromosome instability, and make the genes easy abnormity in fragile sites. However, the role of the chromosome instability and the disfunction of the DNA damage repair in EC with or without positive family history (ECFH+, ECFH-) and hereditary susceptibility have not been well characterized.To further elucidate the possible mechanisms of esophageal carcinogenesis and the genetic affectability in ECFH+, the present study was undertaken to analyze thealterations of FHIT, BRCA2, MLH1 and P53 in ECFH+ and ECFH-, which may provide molecular clue for high-risk subjects screening and early diagnosis.Materials and MethodsSeventy-four EC patients were enrolled in this study. Of these patients, 33 were ECFH+ with a mean age of 56 ±9 years, and 41 were ECFH- with a mean age of 56 ±9 years. ECFH+ patients come from the families that there were >2 EC patients incontinuous two generations. ECFH- patients were patients without EC and other tumors positive history. All the patients were from Linzhou City. All the surgically resected EC samples were collected from the centre hospital in Linzhou. All the specimens were fixed with 85% ethanol, and paraffin embedded, and serially sectioned for morphology and immunohistochemistry (ABC) analysis. All the EC cases were histopathologically confirmed as squamous cell carcinoma (SCC).The difference in immunoreactivity of BRCA2, MLH1, FHIT, P53 and its correlation with cancer progression and the EC familial genetic affectability was determined on the subjects from ECFH+ and ECFH- cases. The X2 test, matched-pairs chi-square test and Spearman Correlation test were used for the statistic analysis, (p<0.05 was considered significant).ResultsThe negative expression of FHIT gene was significantly higher in ECFH+ (56%, 18/33) than ECFH- (27%, 11/41, p<0.01). The negative expression of BRCA2 gene was significantly higher in EC tissue from the ECFH+ than from the ECFH- (67%, 22/33 vs. 37%, 15/41, p<0.01). The negative expression rate for MLH1 in the ECFH+ (73%, 24/33) was higher than in the ECFH- (27%, 16/41), the difference was significant, (p<0.05). Although the positive expression rate for P53 in ECFH+ (52%, 17/33) was higher than in ECFH- (46 %, 19/41), the difference was not significant, (p >0.05).The negative expression of FHIT gene in EC tissue (39%, 29/74) was much higher than in normal tissue (3%, 1/30) from the high incidence area for EC in Linzhou, (p <0.01). The negative expression of BRCA2 gene in EC tissue (50%, 37/74) was much higher than in normal tissue (13%, 4/30) from the high incidence area for EC in Linzhou,(p<0.01).The rates of concordance the negative expression of BRCA2 and FHIT, MLHl and FHIT in ECFH+ were higher than in ECFH- (39%, 36% vs. 2%, 12%, p<0.05). The rates of consistent negative expression of BRCA2 and MLHl in ECFH+ were higher than in ECFH- (45% vs. 12%, p<0.05). The disconsistent expression rates for P53 and MLHl (P53 positive, MLHl negative) in ECFH+ were higher than in ECFH-(36% vs. 15%,p<0.05).The detection rates of lymph node metastasis were higher in ECFH+ cases (39%, 16/41) than in those of ECFH- cases (18%, 6/33), (P<0.05). The negative expression rates of BRCA2 in female was higher than in those male (37%, 5/41 vs. 27%, 9/33) in ECFH-, (P<0.05).The negative expression of BRCA2, MLHl and FHIT and the positive expression of P53 did not show correlation with gender, EC differentiation, infiltration degree and lymph metastasis, (P>0.05).ConclusionsThe higher negative expression of FHIT and BRCA2 in EC tissue than in normal tissue from the high incidence area for EC in Linzhou, indicates that these molecular changes may be involved in the esophageal carcinogenesis. The higher negative expression rates of FHIT, BRCA2 and MLHl expect the positive expression of P53 in ECFH+ and ECFH- suggest that FHIT, BRCA2 and MLHl may play an important role in the EC familial hereditary susceptibility, and P53 may be an important synergistic agent in the process.The rates of concordance the negative expression of BRCA2 and FHIT, MLHl and FHIT, BRCA2 and MLHl in ECFH+ than in ECFH- and the disconsistent expression rates for MLHl and P53 (P53 positive, MLHl negative) in ECFH+ were higher thanin ECFH- indicate that there may be different molecular mechanism involved in EC carcinogenesis. However, no relationship between the abnormal expression of FHIT and the anomalous expression of BRCA2, MLH1 and P53 was observed, which indicate that these molecules may cooperate with other susceptible factors in the familial carcinogenesis.更多还原