Study On Single Nucleotide Polymorphisms Of BRCA1 - Associated Gene And Susceptibility To Triple - Negative Breast Cancer

Part Ⅰ Association Between Single Nucleotide Polymorphisms of BRCA1-Interacting Genes and Susceptibility of Triple-Negative Breast CancerAimsBreast Cancer is one of the commonest female malignancies. Breast cancer type1susceptibility protein (BRCA1) is a well-investigated oncogene. Certain variations of the BRCA1gene lead to an increased risk for breast cancer. The mutation of BRCA1is reported to be linked to the onset of triple negative breast cancer (TNBC). Recent studies have identified genes that encode proteins that interact with BRCA1as modifiers of BRCA1-associated breast cancer. The aim of this study was to investigate the association between TNBC and single nucleotide polymorphisms (SNPs) of BRCA1-associated breast cancer.MethodsTotally414patients with TNBC treated in Fudan University Shanghai Cancer Center and354healthy women were recruited in this study. The DNA from their peripheral blood were obtained. Thirty-seven SNPs from five BRCA1-associated genes (Abraxas, BRE, Rap80, BABAM1, BRCC36) were detected by Massarray system.ResultsFor SNPs located in gene Abraxas, BRE, Rap80, BRCC36, there’re no significant difference of MAF among patients and control. The MAF of rs7250266(a SNP located on the promoter of BABAM1) in patients were significantly lower than that in control (P<0.01). Three genotypes were detected in rs7250266, the frequencies of CC, GC and GG genotypes in the patients and control were significantly different.(P=0.03). Compared with CC genotype, women with the GC genotype (OR=0.70,95%CI (0.51-0.97)) and GG genotype (OR=0.48,95%CI (0.21-1.07)) had a lower risk of developing TNBC. Haplotype analysis showed a difference risk of developing TNBC among different haplotypes of BAB AMI.Conclusions The risk of developing TNBC was associated with genotype of rs7250266. The mutation carrier had a lower chance of developing TNBC than wild type carrier. The haplotype analysis also demonstrated the difference of risk among different haplotypes of BABAM1.Part Ⅱ Analysis to germline and somatic mutation of the BAB AMI gene in women with breast cancer and the interaction between rs8170and BRCA1A complexAimsThe previous part of research had revealed that BABAM1was related to the risk of developing TNBC. We investigated the germline and somatic mutation of the BABAM1gene in women with breast cancer. We also tried to reveal the interaction between rs8170and BRCA1A complex.MethodsA total of140women with primary breast cancer were recruited in this study. Frozen fresh tumor tissues were available in one hundred patients of them. Genomic DNA was isolated from peripheral blood for germline mutation screening and DNA from tumor tissue was isolated for somatic mutation screening. All the coding exons, exon/intron boundaries,5’UTR and3’UTR of the BAB AMI gene were targeted and sequenced after PCR amplifying. Cells were transiently transfected by plasmids carrying wildtype and mutant BABAM1. Immunoprecipitates were analyzed by Western blot to show the binding of BABAM1with other proteins.ResultsTwo unreported germline mutation were detected, one located on Exon2, the other on3’UTR. Meanwhile, a somatic mutation was detected on Exon7. Lacking C-terminal299-329aa of BABAM1lead to disappear of binding with other BRCA1A complex protein. Rs8170was located in that region.In silico analysis showed it might interfere with the splicing of mRNA which might be the reason of affecting protein binding.Conclusions C-terminal299-329aa of BABAM1is the binding site of Rap80, BRE, BRCC36and Abraxas. Its mutation might change the function of BRCA1complex A.Part Ⅲ A Comparison of the Proliferation Index and Survival in Two Cohorts of Node Negative Breast Cancers in China from1980’s and2000’sAimsTo investigate whether proliferation, other prognostic biomarkers, body weight and survival in axillary lymph node (ALN) negative invasive breast cancer patients have changed since1990and if this relates to survival.MethodsWe compared194consecutive operable ALN negative invasive breast cancers in1983-1986(n=89) and2002-2003(n=105). Clinico-pathologic features, Estrogen Receptor (ER), Progestin Receptor (PR), Cytokeratin5/6(CK5/6) and Human Epithelial Growth Factor Receptor2(HER2) were assessed. The proliferation biomarkers mitotic activity index (MAI), phosphohistone-3(PPH3) and Ki67were measured after immunohistochemistry staining.ResultsWith median follow-up time of79months, there’s no difference in relapse free survival rates among the two cohorts. There was no difference in age, tumor diameter, number of nodes detected, CK5/6and HER2, but the following parameters were higher in2002-2003than in1983-1986:body weight, Ki67, PPH3and MAI, while PR negative cancers were more frequent. Ki67is correlated with body weight.ConclusionsProliferation index was higher in ALN negative invasive breast cancer patients in2002-2003than in1983-1986. However, the finding didn’t lead to any survival difference.