Mutation Analysis Of P53,BRIP1 And PALB2 In High-risk Breast Cancer Patients Of Chinese Han Nationality And A Case-control Study On Common SNPs Of PALB2 And Its Correlation With Shanghai Female Breast Cancer

Germline mutations of the high penetrance susceptibility genes BRCA1/2 could only explain about 10%Chinese inherited breast cancers,which indicated that our population had a different hereditary background from other ethnic groups and there might exist other low penetrance genes correlated with the etiology of Chinese breast cancer.To explore the etiology of Chinese non-BRCA1/2 high-risk breast cancers,we fatherly made a mutation analysis of p53,BRIP1 and PALB2 in the potentially inherited breast cancers of Chinese Han nationality in order to get a fundamental knowledge of the prevalence of some low penetrance genes in our population,and whether there were some mutation hot-spots,hot-regions or founder mutations about these genes,and also the pathologic features of disease-related breast cancer specimens.Combining with the results of our series of studies about the high penetrance susceptibility genes BRCA1/2,we can make a suitable strategy of genetic testing among the high-risk individuals of Chinese Han nationality.At the same time, we performed a case-control study about the common single nucleotide polymorphisms of PALB2 gene and its correlation with the breast cancer susceptibility of Shanghai female breast cancer to evaluate the role of genetic variants of PALB2 in the etiology of Chinese breast cancer,and then we had identified some disease-related SNPs of PALB2 gene.Partâ… Germ line mutations in the tumor suppressor gene,p53,are known to cause Li-Fraumeni syndrome(LFS) or Li-Fraumeni-like syndrome(LFL).We sought to identify p53 germ line mutations in potential hereditary breast cancer patients without LFS/LFL phenotype,which will help us establish the genetic testing strategy for p53 in Chinese high-risk breast cancer families.We screened all coding exons and intron-exon boundaries of p53 in 240 women with early-onset breast cancer or affected relatives from four breast disease clinical centers in China by utilizing PCR-DHPLC and DNA sequencing analysis.Additionally,three cell lines(H1299, MCF-7 and MDA-MB-231) were transfected with pEGFP-N1-only or pEGFP-N1 vectors expressing either wild-type or two novel identified mutant p53.And then we performed flow cytometry analysis in the transfected cells to determine the status of cell apoptosis,and real-time PCR as well as western blot analysis to ascertain the expression of p53,p21,and p27.Two novel germ line mutations[563T＞C and 643₆60del18) were detected in two independent families.Neither of them,however, was present in the 768 normal controls.Functional assays revealed that the ability to trigger cell apoptosis and transcriptional activation of target gene under similar expression of p53 were lower in two mutants versus wild-type p53.Deleterious mutations of p53 seemed to be responsible for approximately 1%of non-BRCA1/BRCA2 hereditary breast cancer in Chinese population,and our findings suggested that p53 should be included in genetic testing of Chinese non-LFS/non-LFL high-risk breast cancer families.Partâ…¡PALB2 and BRIP1 have been identified as breast cancer susceptibility genes in western populations.To investigate the contribution of PALB2 and BRIP1 mutations to Chinese non-BRCA1/BRCA2 hereditary breast cancer,we screened all coding exons and intron-exon boundaries of PALB2 and BRIP1 in 360 Chinese women with early-onset breast cancer or affected relatives from five breast disease clinical centers in China,using PCR-DHPLC and DNA sequencing analysis.Some genetic variants identified in the cases were then studied in 864 normal controls with no personal or family history of breast cancer.Two protein-truncating PALB2 mutations,751C＞T and 1050₁051delAAinsTCT,were identified in 3 separate families,and 751C＞T was a recurrent mutation,none of them presented in the controls(p=0.025).All the truncating mutations presented in exon 4 of PALB2,and there were still 3 unclassified variants were detected in the same fragment.We counted that exon 4 accounted for 44.1%(15/34) of the person-times carrying any variant in our study.In BRIP1,we detected a novel non-synonymous variant(2971C＞G,resulting in Q944E) in two independent families compared with none in the controls.Interestingly,this variant occurs in the BRCA1 binding domain of the BACH1 protein.PALB2 mutations are responsible for approximately 1%of Chinese women with early-onset breast cancer and affected relatives,and a detection of exon 4 before the assay of the whole PALB2 gene suggests to be a cost-effective approach to screening of Chinese population, nevertheless,there is no evidence for the recommendation of BRIP1 for genetic testing in China..Partâ…¢ Germline mutations of some known susceptibility genes can explain only a small fraction of breast cancers.Single nucleotide polymorphisms were found in all the known breast cancer predisposing genes,and PALB2 was recently identified as a low penetrance gene of breast cancer,a further study is warrant to explore the effect of common SNPs of PALB2 on the increasing risk of breast cancer in Chinese population.We conducted a case-control study to validate whether there were some disease-related SNPs of PLAB2 in Shanghai female breast cancer patients.In the current study,660 cases and 756 controls were included,and we genotyped 5 common SNPs of PALB2 among 660 cases and 756 controls by SNPstream assay,and then we made a statistical analysis according to the genotyping data.Multivariate analysis showed that the age of each individuals and the postponed first birth increased the risk of Shanghai female breast cancer while the postmenopausal status was a protective factor.The PALB2 rs447529 G was present in 84.8%of the cases and 82.1%of the controls,the odd ration for rs447529 G is 0.82(95%CI 0.69-0.98). and PALB2 rs249935 G was present in 15.5%of the cases and 18.1%of the controls, the odd ration for rs249935 is 1.21(95%CI 1.02-1.43).The results indicated that common SNPs might become an independent factor which was associated with Shanghai female breast cancer susceptibility as well as the age,the postponed first birth and the postmenopausal status.