Mutational Analysis Of BRCA1/2 Genes In Breast Cancer Family And Serum MiR-21 Expression

Objective: This study aims to detect the mutations of BRCA1/2 genes in familial breast cancers and their first-degree relatives in Guangdong area population,in order to enrich the BRCA1/2 mutation spectrum.In the meanwhile, detecting differences of serum mi R-21 expression in breast cancer to further clarify the role of mi R-21 in the pathogenesis of Guangdong area familial and triple negative breast cancers.Methods:1.The cases which from Guangdong area familial breast cancers and immediate relatives of them(high risk of breast cancer) were collected. These objects were analyzed by means of multiplex ligation-dependent probe amplification(MLPA) and direct sequence analysis to collect their BRCA1/2 gene mutation informations. 2.The sera of healthy female volunteers,different types of breast cancer patients and high risk volunteers for breast cancer in Guangdong area were collected. The expression levels of mi R-21 in sera from 77 patients or volunteers were determined by fluorescence quantitative PCR.And Cel-mi R-39 was used as exogenous internal reference. And the association between serum mi R-21 expression level and clinical pathological parameters of breast cancer was investigated.Results:1. One mutation of familial breast cancer in exon2 of BRCA1 by MLPA was identified.Direct sequencing analysis of the BRCA1/2 genes,17 objects revealed the presence of 21 mutations. 7 variants happened in BRCA1 and 14 in BRCA2. In the coding region,10 missense mutations and 3 nonsense mutations were found. In the non-coding region,8 intronic variants were detected. Among the 21 variants, 5 missense mutations in familial breast cancer group including 26T>C、1954T>C、824C>T in BRCA1 and 943T>A、440A>G in BRCA2 were found for the first time.In the meanwhile,1 of 3 nonsense mutations is also novel in high risk group,namely 123A>G.2.The relative expression level of serum mi R-21 was significantly higher in familial breast cancer groups、triple negative breast cancer group and high risk group than that in healthy control group or other breast cancer group(P<0.01). The expression of serum mi R-21 was associated with lymph node metastasis and ki67 expression level(P<0.01).The results showed that serum mi R-21 of patients with familial and triple-negative breast cancer was revelant with lymph node metastasis and Ki67 expression.Conclusion: 1. Five new BRCA1 / 2 gene missense mutation types in Guangdong familial breast cancer and their first-degree relatives were discovered, considered as pathogenic mutations. BRCA2 gene mutation,rather than BRCA1,occurred more frequently in high risk group.2. Sera mi R-21 expression level in Guangdong triple negative breast cancer, familial breast cancer and their first-degree relatives was higher than those of healthy group. The expression level was revelant with lymph node metastasis and Ki67 expression of breast cancer,and as well as may be associated with hereditary,the degree of malignancy and determination of prognosis.