Research On Genetic Susceptibility Of Han Chinese Breast Cancer Patients

This is one part report of the collaborating screening program from Sep 2005 to July 2006.219 consecutive unrelated pedigrees of hereditary breast cancer from three districts in China were recruited.All exons of BRCA1 and BRCA2 were analyzed using DHPLC followed by direct sequencing.Three widely-used models,Penn,Myriad and BRCApro, were employed to predict the probability of BRCA1 and/or BRCA2 mutations in the 104 cases with breast cancer family history.For Penn,Myriad and BRCApro models had limited value in the pre-test probability of BRCA1/2 mutations,especially on predicting the BRCA2 mutation status,a modified model targeted to Han Chinese hereditary breast cancer patients was guaranteed.Then the family history as well as individual information of 200 unrelated probands who had completed BRCA1 and BRCA2 mutation screening was analyzed to assess the likelihood of a pathogenic mutation.A model was developed by Logistic statistic method,which was better than BRCApro validated by a separated cohort.In addition to the deleterious mutations in BRCA1/2,we also did a case-control study of BRCA1 coding SNPs(single nucleotide polymorphism) with sporadic female breast cancer risk of Shanghai population.1.BRCA1/2 Deleterious Mutations in Han Chinese Hereditary Breast Cancer Patients:A Report of a Multicenter BRCA Mutation Screening ProgramEstablishing a BRCA1 and BRCA2 mutation profile in Han Chinese and evaluating the performance of three models(PennⅡ,Myriad and BRCApro) on the assisting in pre-test counseling.A consecutive series of 219 unrelated probands of hereditary breast cancer families from three districts in China were recruited.All exons of BRCA1 and BRCA2 were analyzed using DHPLC followed by direct sequencing.Three widely-used models, Penn,Myriad and BRCApro,were employed to predict the probability of BRCA1 and/or BRCA2 mutations.The speculative probabilities from these models were compared to the outcomes of genetic testing by ROC analysis.A total of 23 deleterious mutations were identified with 7 in BRCA1 and 16 in BRCA2.The frequency of BRCA1/2 mutation varied from 42.8%(3/7) in HBOC group and 10%(10/100) in early onset breast cancer group to 9.3%(9/97) in HBC group and 6.7%(1/15) in bilateral breast cancer group. Prevalence of BRCA2 mutations was higher than that of BRCA1,especially in non-early-onset breast cancer patients with family history(n=77,7.8%vs 0%,P=0.03). Since no founder mutation had been identified in Han Chinese population then entire region of BRCA1 and BRCA2 should be detected in high risk individuals.But testing for BRCA1 and BRCA2 mutations is expensive,and a positive outcome can affect a person's life in important ways.The considerably high costs of BRCA1/2 mutation screening, together with the expanding request for inherited breast and/or ovarian cancer counseling and genetic testing,prompted the development of tools that might help in the selection of the appropriate candidates for the analysis.Penn,Myriad and BRCApro model are three widely used models on the genetic risk assessment in the world.Penn and BRCApro models are derived from the analysis of breast and/or ovarian cancer families ascertained from the USA,and the MyriadI and MyriadⅡmodels largely from North USA and Europe.It's not clear whether these models could be used in clinical practice in China to predict an individual's probability of carrying BRCA1/2 germline mutations.Here we compared the pre-test probability predicted by models with the genetic detection results in 104 cases with breast cancer and/or ovarian cancer family history.For BRCA1 mutation carrier predictions,the sensitivity of Penn,Myriad or BRCApro model was the same of 0.67;the specificity was 0.81,0.78,0,70,respectively;the PPV was 0.09,0.08, 0.06 and their NPV was 0.99.The sensitivity of BRCApro for the probability of BRCA2 mutation was 0.33,the specificity was 0.82,its PPV was 0.15 and the NPV was 0.93. When the analysis of BRCA1 and BRCA2 mutations was combined,the sensitivity of MyriadⅡand BRCApro models were 0.67 and 0.58,their specificity were the same of 0.64,the PPV were 0.19 and 0.18,and their NPV were 0.94 and 0.92.The areas under ROC curves were 0.769 of Penn,0.744 of Myriad and 0.702 of BRCApro for BRCA1; 0.672 of BRCApro for BRCA2;0.697 of MyriadⅡand 0.695 of BRCApro for BRCA1/2 combination.PennⅡ,Myriad and BRCApro models showed limited value in the pre-test probability of BRCA1/2 mutations on the presence of AUCs(area under ROC curve) of three models were lower than 0.750.So the clinical decision of genetic screening in Han Chinese population could be generally made according to the early age at diagnosis and a family history of breast and ovarian cancer.2.Models for Predicting BRCA1 and BRCA2 Mutations in Han Chinese Familial Breast and/or Ovarian Cancer PatientsOur aim was to find an appropriate method to estimate the likelihood that a family history of cancer was a result of a mutation in the BRCA1 or BRCA2 genes.We also compared the performance of the established method with three different methods(Couch,Sh-E and BRCApro) to identify an alternative strategy for genetic council targeted to the specified population.The family history as well as individual information of two hundred unrelated probands who had completed BRCA1 and BRCA2 mutation screening was analyzed to assess the likelihood of a pathogenic mutation.A model was developed by empirical method.The performance of this model was validated in a separate patient cohort compared with BRCApro.Several factors were associated with mutations in univariate analysis and a logistic model was devised to estimate the probability for a proband of harboring a mutation in BRCA1 and/or BRCA2.Using a greater than 10% probability threshold,the highest accuracy was achieved by the established model when compared to other three models,presenting the highest sensitivity,PPV,NPV and area under ROC curve.The empirical model showed a better ROC curve compared to BRCApro in the verification cohort.A probability model targeted to Han Chinese population should be a useful tool in the genetic counseling for the specified ethnic.Its ability to predict BRCA2 mutation carriers needs to be improved.3.A Case-control Study of Coding SNPs in BRCA1 with Shanghai Female Sporadic Breast CancerIn the decade since BRCA1(MIM 113705)~1 and BRCA2(MIM 600185)~2were identified as susceptibility genes for breast and ovarian cancer,genetic testing of these genes has become part of clinical practice.A lot of single nucleotide substitutions have been identified during the mutation screening,while most of them classified unverified variation in the Breast Cancer Information Core(BIC,http://research.nhgri.nih.gov/bic/). The single nucleotide substitution which frequency is more than 0.01 is SNP.The effect of SNPs of BRCA1 on the breast cancer risk remains unknown.This study was aim to validate and genotype polymorphisms in the BRCA1gene and assessed whether these single nucleotide polymorphisms(SNPs),or the imputed haplotypes,were associated with breast cancer risk.We dumped the BRCA1 SNP data of Asia panel from the HapMap website and our interesting was focus on the coding SNPs of BRCA1.Seven coding SNPs were validated and five SNPs in exons 11 of BRCA1 were in complete linkage disequilibrium.BRCA1 rs16942 in exon11 as well as rs1060915 in exon13 and rs1799966 in exon16 were targeted as tagSNP by Haploview software.We genotyped three haplotype-tagging SNPs(rs16942A/G,rs1060915C/T,rs1799966A/G) and two additional SNPs(c.300T/G and c.1303C/T) in an age matched case-control study of breast cancer(cases 464,controls 455).Multivariate analysis showed that the age of the individual and the postponed first birth increased the risk of Shanghai female sporadic breast cancer while postmenopausal status was the protective factor of brease cancer.The rs1060915 allele C was present in 0.366 of the eases and 0.2987 of the controls,which increased 2.36 in the risk of breast cancer(95%CI 1.35-4.14).The rs1060915 CC was present in 0.147 of the eases and 0.099 of the controls,and the odd ratio was 4.3 in the risk of breast cancer(95%CI 1.23-14.9).Linkage disequilibrium showed rs16942A/G, rs1060915C/T and rs1799966A/G were high linkage disequilibrium(r~2=0.808) and four common(＞3%frequency) haplotypes consisted of these SNPs accounted for 90%of the chromosomes at this locus.BRCA1 haplotype GCG was present in 0.341 of the cases and 0.285 of the controls,the odd ratio was 1.13(95%CI 0.98-1.37).Our study showed that BRCA1 rs1060915 C,rs1060915 CC and the haplotype GCG were the independent factors which were associated with Shanghai female breast cancer susceptibility as well as the age,the postponed first birth and the postmenopausal status.In summary,this study initiated a BRCA1 and BRCA2 mutation screening in 219 hereditary breast cancer patients as the biggest part of China multiple-center mutation screening program.And then established an empirical model based on the entire database of the mutation screening program after got an unfavorable conclusion from comparing the genetic results with the pre-test probability predicted by Penn,Myriad and BRCApro. At last,a case-control study about the BRCA1 coding SNPs and the risk of sporadic breast cancer was finished in 464 female breast cancer patients and 445 age-matched healthy controls from Shanghai district.We found that BRCA1 coding SNP rs 1060915 C, rs1060915 genotype CC and one haplotype of BRCA1 increased the risk of Shanghai female breast cancer.So our study showed that not only the deleterious mutations in BRCA1 and BRCA2 were high linked to the hereditary breast cancer,but also the common variations of BRCA1 were associated with the sporadic breast cancer in Shanghai.However,the functional variant was not clear and additional studies are warranted to confirm these findings.