高发区食管癌患者p16基因甲基化及其表达的比较研究

目的:比较p16基因甲基化在食管癌高发区河南林州(北方组)和广东揭阳(南方组)之间的异同,探讨p16基因甲基化在不同气候环境条件下的两地食管鳞癌(ESCC)发生中的作用。方法:采用甲基化特异性PCR方法(MSP)分别检测两地食管癌组织、癌旁组织和切缘组织p16基因启动子区域CpG岛甲基化状态。采用EnVision免疫组化法检测两地食管癌组织及癌旁组织的p16蛋白的表达。结果:南方组75例标本中,食管癌组织、癌旁组织和切缘组织p16基因甲基化率分别为41.3%(31/75)、13.3%(10/75)和6.67%(5/75);癌组织和癌旁组织p16蛋白的阳性表达率分别为29.3%(22/75)和56.7%(17/30);31例p16基因甲基化阳性标本中有2例(6.4%)检测到p16蛋白的表达,而44例p16基因甲基化阴性标本中有20例(45.5%)检测到p16蛋白的表达。北方组65例标本中,食管癌组织、癌旁组织、切缘组织p16基因甲基化率分别为52.3%(34/65)、16.9%(11/65)和7.69%(5/65);食管癌组织和癌旁组织p16蛋白的阳性表达率分别为32.3%(21/65)和66.7%(20/30);34例p16基因甲基化阳性标本中有4例(11.8%)检测到p16蛋白的表达,而31例p16基因甲基化阴性标本中有17例(54.8%)检测到p16基因的表达。两地组内癌组织p16甲基化率均显著高于癌旁组织和切缘组织,p16蛋白表达与p16基因甲基化呈负相关(P<0.01)。两地同类组织比较p16甲基化率和p16蛋白表达率均无显著性差异(P>0.05)。结论:p16基因异常甲基化后功能失活可能是南、北两地食管癌癌变过程的重要事件,在我国南北环境气候条件不同的两地高发区食管癌的发生中均起着重要的作用。本研究为环境因素和p16基因功能之间的生物学关联在食管癌的发生中提供了一定的证据。

Comparative study on p16 gene methylation and expression of esophageal squamous cell carcinoma in high incidence areas

Objective:To investigate hypermethylation status and expression of p16/INK4 gene in carcinogenesis of esophageal squamous cell carcinoma(ESCC)in two high incidence areas of different environment from linzhou(northern group)and jieyang(southern group)city.Methods:The hypermethylation of the p16/INK4 promoter region was detected by methylation specific polymerase chain reaction(MSP)in all esophageal cancer tissues,adjacent mucosa tissues and each corresponding edge of dissection;With EnVision Immunohistochemistry,both esophageal carcinoma tissues and their adjacent mucosa tissues were stained by using the multiclonal antibody against the human p16 protein respectively.Results:Seventy-five cases of EC in southern group,hypermethylation of the p16/INK4 promoter region was detected in 28 cases of EC tissues 37.3%(28/75),10 cases of adjacent esophageal tissues13.3%(10/75),5 cases of dissected edge tissues 6.67%(5/75).The positive rate of p16 gene expression was 29.3%(22/75)in EC tissues,56.7%(17/30)in adjacent mucosa tissues.p16 gene expression was detected in 2 of 31 cases of(6.4%)p16 methylation positive EC and 20 of 44 cases of(45.5%)p16 methylation negative EC.In addition,of 62 cases in northern group,the methylation rate of p16/INK4 gene was 52.3%(34/65)in EC tissues,16.9%(11/65)in esophageal adjacent tissues,7.69%(5/65)in dissected edge tissues.p16 gene expression rate was 32.3%(21/65)in EC tissue,66.7%(20/30)in adjacent mucosa tissues.In p16 methylation positive and negative EC,the rate of p16 gene expression was 11.8%(4/34)and 54.8%(17/31)respectively.The methylation rate in EC tissues was remarkably higher than that of either adjacent tissue or dissected edge tissue(P<0.01),There were obvious negative orrelation between p16 gene methylation and p16 gene expression(P<0.01).but no difference was found in each same kind of tissues within two groups(P>0.05).Moreover,p16 gene expression rate in p16 methylation positive EC was much lower than that of negative one in two groups.(P<0.05).Conclusion:p16 gene methylation was closely associated with the absence of p16 gene expression and might be a similar and an important mechanism in chinese northern and shouthern EC high incidence areas,which may play an significant role in pathogenesis of EC in two different climatic environmental areas which have high incidence rate of esophageal squamous cell carcinoma.Futhermore,the results provided some valuable evidence on the biological relationship of the environmental factors and p16 gene function for pathogenesis of ESCC.