BRCA1基因在散发性乳腺癌中的表达及异常甲基化

Expression and abnormal methylation BRCA1 in sporadic breast cancer

目的通过检测乳腺癌易感基因1(BRCA1)基因在散发性乳腺癌中的表达情况及其启动子甲基化状态,探讨BRCA1基因与散发性乳腺癌的关系。方法应用实时荧光定量PCR的方法和免疫组织化学方法分别检测BRCA1mRNA和蛋白在60例散发性乳腺癌组织、癌旁正常乳腺组织及30例乳腺良性病变组织中的表达情况;应用重亚硫酸盐测序PCR(BPS)联合TA克隆测序方法检测上述组织中BRCA1启动子CpG岛的甲基化状态,分析BRCA1基因表达和启动子甲基化相关性。结果 BRCA1mRNA和蛋白在散发性乳腺癌组织中的相对表达水平分别低于癌旁正常组织及乳腺良性病变组织,差异有统计学意义(P<0.001)。乳腺癌组织中BRCA1蛋白的表达率为51.7%(31/60),明显低于癌旁正常乳腺组织的71.7%(43/60)及乳腺良性病变组织的66.7%(20/30),差异有统计学意义(P<0.001);散发性乳腺癌组织中BRCA1启动子甲基化率为31.7%(19/60),癌旁正常乳腺组织及乳腺良性病变组织均未检测出甲基化,差异有统计学意义(P=0.000);BRCA1蛋白表达与其启动子甲基化呈负相关(r=-0.345,P=0.007)。结论乳腺癌易感基因BRCA1启动子区CpG岛甲基化导致BRCA1基因表达显著下调,可能参与散发性乳腺癌的发生、发展。

Objective To investigate expression and promoter methylation status of BRCA1 in sporadic breast cancer .Meth-ods The expression of BRCA1 mRNA and protein were detected in 60 cases of sporadic breast cancer ,the adjacent breast tissues , and 30 cases of breast benign lesion tissue by RT-PCR and and immunohistochemical staining respectively .The methylation status of BRCA1 promoter in those tissues were detected using bisulfite genomic sequencing PCR （BSP） combined with TA clone for se-quencing .The relation between BRCA1 expression in sporadic breast cancer and promoter methylation status was analyzed .Results The expression level of BRCA1 mRNA and protein were down-regulated in sporadic breast cancer tissues compared to the corre-sponding adjacent breast tissues and breast benign lesion tissue（P〈0 .001） .The positive rates of BRCA1 protein was 51 .7% （31/60）in sporadic breast tissue ,which were significantly lower than those of in the adjacent breast tissues 71 .7% （43/60）and breast benign lesion tissue 66 .7% （20/30）（P〈 0 .001） .The methylation rate of BRCA1 promoter CpG was 31 .7% （19/60）in sporadic breast ,while it wasn′t found in adjacent breast tissues and breast benign lesion tissue（P=0 .000） .The statistical analysis showed the expression of BRCA1 had significant negative correlation with promoter methylation（r= -0 .345 ,P=0 .007） .Conclusion The hypermethylation of BRCA1 promoter could induce BRCA1 down-regulating ,which may be involved in the occurrence and develop-ment of sporadic breast cancer .