The p53 Arg72Pro and Ins16bp polymorphisms and their haplotypes are not associated with breast cancer risk in BRCA-mutation negative familial cases

Background: Germline disease-causing mutations in BRCA1 and BRCA2 genes confer high risk of breast and ovarian cancer, but account approximately for only 15% of familial cases. Theoretical models and experimental observations have indicated that the remaining familial aggregations would be explained by low-penetrance alleles. Moreover, alleles acting as genetic modifiers would modulate the breast cancer risk in carriers of BRCA mutations. The Ins16bp and Arg72Pro polymorphisms of p53 were implicated in breast cancer and recently it has been shown that these polymorphisms could have an effect when combined as specific haplotypes. Here, we investigated the possible role of the Ins16bp and Arg72Pro polymorphisms and their haplotypes as low-penetrance alleles in familial breast cancer. Methods: The Ins16bp and Arg72Pro polymorphisms were genotyped in a total of 350 familial index cases affected with breast cancer and negative for mutations in BRCA genes, and 352 controls. The Ins16bp and Arg72Pro polymorphisms were studied separately, and as haplotypes and haplotypes combinations. Results: None of the performed analyses resulted statistically significant. Conclusions: These observations suggested that neither the Ins16bp or Arg72Pro polymorphisms considered separately, nor any related haplotype, were associated with breast cancer risk in BRCA-mutation negative familial cases.     

BRCA1 and BRCA2 germline mutations in 85 Iranian breast cancer patients

Breast cancer is the most common cancer in Iranian women (Mousavi et al in Asian Pac J Cancer Prev 9(2):275–278, 2008). Genetic predisposition accounts for 15% of all breast cancers and germline mutations in breast cancer susceptibility genes, BRCA1 and BRCA2 are responsible for a substantial proportion of high-risk breast and breast/ovarian cancer families (Collaborative Group on Hormonal Factors in Breast Cancer in Lancet 350:1047–1059, 1997; Lee et al in Int Nurs Rev 55:355–359, 2008; Hulka and Stark in Lancet 346:883–887, 1995; Kelsey in Epidemiol Rev 15:256–263, 1993; Tischer et al in J Biol Chem 266:11947–11954, 1991; Newman et al in: Proc Natl Acad Sci USA 85:3044–3048, 1988). Therefore, the aim of this study was to investigate mutations of BRCA1/2 in high risk Iranian families. We screened 85 patients who met our minimal criteria. The entire coding sequences and each intron/exon boundaries of BRCA1/2 genes were screened by direct sequencing. In the present study, we could detect the novel following mutations: p.Glu1735 p.Gly1140Ser, p.Ile26Val, p.Leu1418X, p.Glu23Gln, p.Leu3X, p.Asn1403His, p.Lys581X, p.Pro938Arg, p.Thr77Arg, p.Arg7Cys, p.Ser177Thr, IVS7+83(TT), IVS8−70(-CATT), IVS2+9(-GC), IVS1−20(-GA), IVS1−8(-AG), IVS2+24(AG), IVS5−8 (A–G), IVS2(35–39)TTcctatGAT in BRCA1 and p.Glu1391Gly, 1994_1995 (Ins A), IVS6-70−T>G in BRCA2. In agreement with findings in other populations, we found that family history is a good predictor of being a mutation carrier. Five pathogenic BRCA1 mutations and one pathogenic BRCA2 mutation were detected in 85 index cases.     

Loss of Heterozygosity in Bilateral Breast Cancer

Women who develop bilateral breast cancer at an early age are likely to harbour germline mutations in breast cancer susceptibility genes. The aim of this study was to test for concordant genetic changes in left and right breast cancer of young women (age <50) with bilateral breast cancer that may suggest an inherited breast cancer predisposition. Microsatellite markers were used to test for loss of heterozygosity (LOH) in left and right tumours for 31 women with premenopausal bilateral breast cancer. Markers adjacent to or within candidate genes on 17p (p53), 17q (BRCA1), 13q (BRCA2), 11q (Ataxia Telangiectasia-ATM) and 3p (FHIT) were chosen. Mutational testing for BRCA1 and BRCA2 was performed for cases where blood was available. Concordant LOH in both left and right tumours was demonstrated for at least one of the markers tested in 16/31(54%) cases. Where allelic loss was demonstrated for both left and right breast cancer, the same allele was lost on each occasion. This may suggest a common mutational event. Four cases showed concordant loss of alleles in both left and right breast cancer at D17S791 (BRCA1). BRCA1 mutations were identified in two of these cases where blood was available. Four cases showed concordant LOH at D13S155 (BRCA2). Concordant LOH was further demonstrated in seven cases for D11S1778 (ATM) and four cases for D3S1300 (which maps to the FHIT gene), suggesting a possible role for these tumour suppressor genes in this subgroup of breast cancer patients. No concordant allelic loss was demonstrated for D17S786 suggesting that germline mutations in p53 are unlikely in such cases of bilateral breast cancer.     

Novel genetic variants in microRNA genes and familial breast cancer

MicroRNA (miRNA) plays an important role in tumorigenesis, but whether miRNA is a cancer predisposition factor or not is still unknown. Considering the fact that miRNA regulates a number of tumor suppressor genes (TSGs) and oncogenes, genetic variations in miRNA genes could affect the levels of expression of TSGs or oncogenes and, thereby, cancer risk. To test this hypothesis, we screened genetic variants in 17 selected miRNA genes, which are predicted to regulate key breast cancer genes, in 42 patients with familial breast cancer. Seven novel genetic variants were observed in 7 primary or precursor miRNA genes. Among them, 1 rare variant in the precursor of miR‐30c‐1 and 1 rare variant in the primary precursor of miR‐17 were only observed in noncarriers of BRCA1/2 mutations. In functional assays, these 2 variants resulted in conformational changes in the predicted secondary structures, and consequently altered the expression of mature miR‐30c‐1 and miR‐17. In the target in vitro assay, we observed that miR‐17 could bind to the 3′UTR of BRCA1 mRNAs, which is predicted to be a target for miR‐17. Our findings suggest that functional genetic variants in miRNA genes can potentially alter the regulation of key breast cancer genes. Whether they confer genetic susceptibility to breast cancer remains to be determined. © 2008 Wiley‐Liss, Inc.     

Germline mutations in 40 cancer susceptibility genes among Chinese patients with high hereditary risk breast cancer

Multigene panel testing of breast cancer predisposition genes have been extensively conducted in Europe and America, which is relatively rare in Asia however. In this study, we assessed the frequency of germline mutations in 40 cancer predisposition genes, including BRCA1 and BRCA2, among a large cohort of Chinese patients with high hereditary risk of BC. From 2015 to 2016, consecutive BC patients from 26 centers of China with high hereditary risk were recruited (n = 937). Clinical information was collected and next-generation sequencing (NGS) was performed using blood samples of participants to identify germline mutations. In total, we acquired 223 patients with putative germline mutations, including 159 in BRCA1/2, 61 in 15 other BC susceptibility genes and 3 in both BRCA1/2 and non-BRCA1/2 gene. Major mutant non-BRCA1/2 genes were TP53 (n = 18), PALB2 (n = 11), CHEK2 (n = 6), ATM (n = 6) and BARD1 (n = 5). No factors predicted pathologic mutations in non-BRCA1/2 genes when treated as a whole. TP53 mutations were associated with HER-2 positive BC and younger age at diagnosis; and CHEK2 and PALB2 mutations were enriched in patients with luminal BC. Among high hereditary risk Chinese BC patients, 23.8% contained germline mutations, including 6.8% in non-BRCA1/2 genes. TP53 and PALB2 had a relatively high mutation rate (1.9 and 1.2%). Although no factors predicted for detrimental mutations in non-BRCA1/2 genes, some clinical features were associated with mutations of several particular genes.     

Novel germline mutations in breast cancer susceptibility genes BRCA1, BRCA2 and p53 gene in breast cancer patients from India

Mutations in breast cancer susceptibility genes, BRCA1 and BRCA2 account for more than 80% of hereditary breast and ovarian cancers. p53 tumor suppressor gene that controls cellular growth and differentiation is also known to be mutated in more than 50% of human cancers including breast cancer. We have carried out a study on BRCA1 and BRCA2 along with p53 gene mutations in both sporadic as well as familial breast cancer patients from India where breast cancer is fast emerging as a major cancer among premenopausal urban women. We examined 124 untreated primary breast cancer patients comprising 100 sporadic and 24 familial cases including 56 age-matched healthy controls for the presence of BRCA1, BRCA2 and the p53 gene mutations using PCR-SSCP and direct nucleotide sequencing. Certain frequently mutated exons such as 2, 5, 11, 13 and 20 of BRCA1, exons 2, 9, 11 (for 6174delT), 18 and 20 of BRCA2 and 4–9 exons of p53 gene were analyzed in sporadic breast cancer while all 22 coding exons of BRCA1 including its flanking intronic regions along with above mentioned exons of BRCA2 and p53 gene were analyzed in familial breast cancer patients. We identified six patients (25%) with BRCA1 mutation of which three were found to be of novel type one in exon 16 (4956insG) and two in exon 7 (Lys110Thr) (Ser114Pro) out of 24 familial breast cancer patients studied from two different geographic regions/populations of India. Two sisters from a single family (12.5%) out of eight families from Goa with Portuguese colonial origin showed presence of founder Ashkenazi Jewish BRCA1 mutation (185delAG) along with (IVS7 561–34T>C; IVS18 527166G>A). While from New Delhi, four (25%) of 16 breast cancer families showed BRCA1 mutations; a frame shift protein truncating (4956insG), a transition nonsense (Gln1395Stop) and two amino acid substitutions (Lys110Thr) and (Ser114Pro). Only one (4%) p53 mutation (Val97Ile) in its exon 4 along with BRCA1 mutation (4956insG) could be detected. No major sequence variation in BRCA2 gene was observed except for G203A at 5 UTR of exon 2, a common population polymorphism in two Goan patients who also showed silent nucleotide change for amino acid serine at codon 1436 of BRCA1 gene. None of the 100 sporadic breast cancer patients revealed any protein truncating or deleterious BRCA1 or BRCA2 gene mutation. Interestingly, three (3%) p53 mutations in its exon 5 were detected in sporadic breast cancer patients. Although three novel BRCA1 mutations including a founder Ashkenazi Jewish BRCA1 mutation were recorded in Indian women with familial breast cancer, the overall prevalence of BRCA gene mutations in Indian women with a family history of breast cancer appears to be low.     

BRCA1 and BRCA2 germline mutational spectrum and evidence for genetic anticipation in Portuguese breast/ovarian cancer families

We present the first characterisation of the mutational spectrum of the entire coding sequences and exon–intron boundaries of the BRCA1 and BRCA2 genes as well as large BRCA1 rearrangements in Portuguese families with inherited predisposition to breast/ovarian cancer. Of the 100 probands studied, pathogenic mutations were identified in 22 (24.7%) of 89 breast and/or ovarian cancer families with more than one affected member (15 in BRCA1 and seven in BRCA2), but in none of the 11 patients without family history of cancer. One (6.7%) of the BRCA1 mutations is a large deletion involving exons 11–15. Seven pathogenic point mutations are novel: 2088C>T, 2156delinsCC, and 4255_4256delCT in BRCA1 and 4608_4609delTT, 5036delA, 5583_5584insT, and 8923C>T in BRCA2. The novel 2156delinsCC was identified in three probands from different families and probably represents a founder mutation in our population. We also found a previously reported 3450_3453del4 mutation in three unrelated patients. In addition to the 22 pathogenic mutations, we identified 19 missense mutations of uncertain pathogenic significance, three of them (5241G>C in BRCA1 and IVS6+13C>T and 3731T>C in BRCA2) previously undescribed. The percentage of cases with truncating mutations in BRCA1 and BRCA2 was higher in breast/ovarian cancer (37.0%, mostly BRCA1) and male breast cancer (40%, all BRCA2) families than in families with only female breast cancer (17.5%). Interestingly, we found evidence for genetic anticipation regarding age at diagnosis of both breast and ovarian cancer in those families presenting affected members in more than one generation. These findings should be taken into consideration while planning screening and prophylactic measures in families with inherited predisposition to breast and ovarian cancer.     

Hereditary premenopausal breast cancer

Less than 1% of breast cancers occur between the age of 20 and 30 years, but more than 50% of breast cancers under the age of 30 years are hereditary. Breast cancer mainly occurs sporadically, however, in 5 to maximally 10% of cases a genetic predisposition is present. Mutations in the already sequenced tumor suppressor genes BRCA1 and BRCA2 account for 60-70% of these hereditary breast cancers. The chromosomal location of BRCA1 is 17q21 and that of BRCA2 is 13q12-13. Screening procedures and possible prevention strategies for women with mutations in the BRCA1 and BRCA2 genes are discussed. They include the use of tamoxifen.     

Genomic profiling of breast tumours in relation to BRCA abnormalities and phenotypes

Introduction  

Germline mutations in the BRCA1 and BRCA2 genes account for a considerable fraction of familial predisposition to breast cancer. Somatic mutations in BRCA1 and BRCA2 have not been found and the involvement of these genes in sporadic tumour development therefore remains unclear.     

Racial differences in genetic factors associated with breast cancer

Breast cancer in African Americans in the US is more aggressive and has a worse outcome than breast cancer in Caucasians. Although the incidence of breast cancer among US whites is higher than among blacks, the mortality rates for blacks are much higher. Breast cancer in blacks is also associated with a more advanced stage at presentation and pathologically aggressive tumors commonly exhibiting estrogen receptor negativity, higher S-phase fractions, and higher numbers of involved lymph nodes. This paper reviews some of the genetic factors that have been shown to be associated with a difference in breast cancer outcome between African Americans and Caucasians in the US such as the BRCA1 and BRCA2 genes, p53 mutations, UGT1A1 gene polymorphisms, and HER-2/neu gene amplifications/overexpression.     

Genotyping of BRCA1, BRCA2, p53, CDKN2A, MLH1 and MSH2 genes in a male patient with secondary breast cancer

Background

Some tumour suppressor genes (BRCA2) and mismatch repair genes (MSH2, MLH1) are correlated with an increased risk for male breast cancer.

Case report

Our patient developed secondary breast cancer after the treatment for Hodgkin’s disease in childhood. DNA was isolated from the patients’ blood and screened for mutations, polymorphisms and variants in BRCA1, BRCA2, p53, CDKN2A, MLH1 and MSH2 genes. We found no mutations but common polymorphisms, and three variants in mismatch repair genes.

Conclusions

Nucleotide variants c.2006-6T>C and p.G322D in MSH2 might be correlated with male breast cancer.     

A novel de novo BRCA2 mutation of paternal origin identified in a Spanish woman with early onset bilateral breast cancer

Germ line mutations in either of the two major breast cancer predisposition genes, BRCA1 and BRCA2, account for a significant proportion of hereditary breast/ovarian cancer. Identification of breast cancer patients carrying mutations in any of these genes is primarily based on a positive family history of breast/ovarian cancer or early onset of the disease. In the course of mutation screening of the BRCA1 and BRCA2 genes in a hospital based series of patients with risk factors for hereditary breast/ovarian cancer, we identified a novel germ line mutation in the BRCA2 gene (c.51dupA) in a patient with early onset bilateral breast cancer and no family history of the disease. None of her parents carried the mutation, and paternity was confirmed. Subsequent molecular analysis demonstrated that the mutation was a novel de novo germ line mutation located in the paternal allele of the BRCA2 gene.     

The RNF146 and ECHDC1 genes as candidates for inherited breast and ovarian cancer in Jewish Ashkenazi women

Only about 40% of the familial aggregation of breast cancer can be attributed to germline mutations in currently identified genes, primarily BRCA1 and BRCA2. A recent genome-wide association study focusing on Jewish Ashkenazi high risk women identified a novel locus on chromosome 6 as putatively containing breast cancer susceptibility genes, a locus that contains two seemingly novel candidate genes: RNF146 and ECHDC1. To further explore the role of these two genes in inherited predisposition to breast cancer. High risk, cancer affected Jewish Ashkenazi women, were genotyped for harboring germline mutations in the coding exons of both the RNF146 and ECHDC1 genes, using direct sequencing. All participants were Ashkenazim, of high risk families, and affected with cancer: 104 with breast cancer [age at diagnosis (mean ± SD) 51 ± 11.1 years], and one with ovarian cancer (61 years). None was a carrier of the predominant Jewish BRCA1/BRCA2 mutations. An intronic sequence alteration was detected in 4/105 genotyped patients in intron 3 of the ECHDC1 gene. No other sequence alterations were detected in the genomic regions analyzed of the RNF146 and ECHDC1 genes in any of the study participants. Mutations in the coding regions of the RNF146 and ECHDC1 genes do not contribute to the burden of inherited predisposition of breast cancer in Ashkenazi high risk women.     

BRCA1 germline mutations and tumor characteristics in Chinese women with familial or early-onset breast cancer

The data related to BRCA1 germline mutation in Chinese women with familial breast cancer is increasing. However, little is known the frequency of BRCA1 mutations in Chinese women with familial or early-onset breast cancer from Northern China, and few studies are available to investigate the clinicopathological characteristics of BRCA1 tumors in Chinese women. In this study, we detected germline mutations in BRCA1 in a cohort of 139 breast cancer patients who either have a family history of breast cancer (n = 68) or whose tumors are diagnosed at or before the age of 35 (n = 71) from Northern China. A total of 6 deleterious BRCA1 mutations were identified in this cohort, 4 of which (5587-1 del8, 3887 del AG, IVS21 + 1delG, and 2129 ins TG) are novel and one mutation (3478del5) detected in this study was only reported in Chinese population. The frequency of BRCA1 mutations in women with familial or early-onset breast cancer was 5.9% (4/68) or 2.8% (2/71) in this cohort, respectively; but the mutations were detected in 4 of 16(25.0%) familial breast cancer patients whose tumors were diagnosed before the age of 40. Moreover, BRCA1 mutation tumors tended to be high histological grade, and to be negative for ER, PgR, and Her-2 compared with tumors without BRCA1 mutations. Our study suggests that Chinese women with a family history of breast cancer whose tumors are diagnosed before age of 40 would be a suitable candidate for BRCA1 testing; and BRCA1 tumors in Chinese women exhibit an aggressive phenotype. W. Chen and K. Pan contributed equally to this study.     

No germline mutations in the histone acetyltransferase gene <Emphasis Type="Italic">EP300</Emphasis> in <Emphasis Type="Italic">BRCA1</Emphasis> and <Emphasis Type="Italic">BRCA2</Emphasis> negative families with breast cancer and gastric,pancreatic, or colorectal cancer

Introduction  

Mutations in BRCA1, BRCA2, ATM, TP53, CHK2 and PTEN account for many, but not all, multiple-case breast and ovarian cancer families. The histone acetyltransferase gene EP300 may function as a tumour suppressor gene because it is sometimes somatically mutated in breast, colorectal, gastric and pancreatic cancers, and is located on a region of chromosome 22 that frequently undergoes loss of heterozygosity in many cancer types. We hypothesized that germline mutations in EP300 may account for some breast cancer families that include cases of gastric, pancreatic and/or colorectal cancer.     

BACH1 Ser919Pro variant and breast cancer risk

Background  

BACH1 (BRCA1-associated C-terminal helicase 1; also known as BRCA1-interacting protein 1, BRIP1) is a helicase protein that interacts in vivo with BRCA1, the protein product of one of the major genes for hereditary predisposition to breast cancer. Previously, two BACH1 germ line missense mutations have been identified in early-onset breast cancer patients with and without family history of breast and ovarian cancer.     

The pathology of familial breast cancer: Immunohistochemistry and molecular analysis

Extensive studies of BRCA1- and BRCA2-associated breast tumours have been carried out in the few years since the identification of these familial breast cancer predisposing genes. The morphological studies suggest that BRCA1 tumours differ from BRCA2 tumours and from sporadic breast cancers. Recent progress in immunohistochemistry and molecular biology techniques has enabled in-depth investigation of molecular pathology of these tumours. Studies to date have investigated issues such as steroid hormone receptor expression, mutation status of tumour suppressor genes TP53 and c-erbB2, and expression profiles of cell cycle proteins p21, p27 and cyclin D₁. Despite relative paucity of data, strong evidence of unique biological characteristics of BRCA1-associated breast cancer is accumulating. BRCA1-associated tumours appear to show an increased frequency of TP53 mutations, frequent p53 protein stabilization and absence of imunoreactivity for steroid hormone receptors. Further studies of larger number of samples of both BRCA1- and BRCA2-associated tumours are necessary to clarify and confirm these observations.     

The prevalence of BRCA1 and BRCA2 germline mutations in high-risk breast cancer patients of Chinese Han nationality: two recurrent mutations were identified

To have an overview of the role of BRCA1 and BRCA2 genes among Chinese high-risk breast cancer patients, we analyzed 489 such high-risk breast cancer patients from four breast disease clinical centers in China, by using PCR-DHPLC or SSCP-DNA sequencing analysis. Allelotype analysis was done at five short tandem repeat (STR) markers in or adjacent to BRCA1 on the recurrent mutation carriers. For those analyzed both genes, 8.7% of early-onset breast cancer cases and 12.9% of familial breast cancer cases had a BRCA1 or BRCA2 mutation, as compared with the 26.1% of cases with both early-onset breast cancer and affected relatives. For those reporting malignancy family history other than breast/ovarian cancer, the prevalence of BRCA1/2 mutation is about 20.5%, and it was significantly higher than the patients only with family history of breast/ovarian cancer (P = 0.02). The family history of ovarian cancer (26.7% vs. 11.9%) and stomach cancer (23.8% vs. 11.8%) doubled the incidence of BRCA1/2, but the difference did not reach the statistical significance. Two recurrent mutations in BRCA1, 1100delAT and 5589del8, were identified. The recurrent mutations account for 34.8% BRCA1 mutations in our series. Similar allelotypes were detected in most STR status for those harboring the same mutations. The BRCA1 associated tumors were more likely to exhibit a high tumor grade, negative C-erbB-2/neu status and triple negative (ER, PgR and C-erbB-2/neu negative) status (P < 0.05). We recommended the BRCA1 and BRCA2 genetic analysis could be done for high-risk breast cancer patient in Chinese population, especially for those with both early-onset breast cancer and affected relatives. There may be some degree of shared ancestry for the two recurrent BRCA1 mutations in Chinese. Wen-Feng Li and Zhen Hu have contributed equally to this work.