RESUMO
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 .