Anna Niwińska

Germline mutations 657del5 of the NBS1 gene contribute significantly to the incidence of breast cancer in Central Poland

Recent studies have demonstrated that heterozygous carriers of the NBS1 657del5 mutation have an increased risk for familial and bilateral breast cancer, but similar studies in consecutive breast cancer patients were inconclusive. Here, in a study of 562 nonselected breast cancer patients from Central Poland, we found 11 (1.96%) 657del5 mutation carriers vs. 3.47 expected (OR 3.21, 95%CI: 1.36–7.61, p = 0.0107) and only 9 (1.6%) carriers of the 5382insC mutation of the BRCA1 gene, most frequently found among breast cancer patients in Poland. No carriers of R215W, another pathogenic mutation of the NBS1 gene, were found in the present study. All carriers of the 657del5 mutation had sporadic breast tumors while 5 of 9 5382insC carriers had a family history of breast/ovarian cancer or bilateral breast carcinoma. In the pooled group of patients from the present and our previous study, carried out also in patients from Central Poland, we obtained the following risk estimates (OR) for 657del5 carriers, as related to the age at breast cancer diagnosis: <40 years: 8.36; (95%CI: 2.57–27.27) p = 0.0003; <50 years: 4.27 (95%CI: 1.67–10.89) p = 0.003; ≥50 years: 2.40 (95%CI: 0.91–6.35) p = 0.1250; all ages: 3.13 (95% CI: 1.40–7.00) p = 0.0066. These findings demonstrate conclusively that NBS1 657del5 mutation carriers have a significantly, though moderately increased, age‐related risk of breast cancer, and imply that in populations with a high 657del5 carrier frequency this mutation may contribute substantially to the overall incidence of breast cancer, particularly in younger age groups.

A novel germline PALB2 deletion in Polish breast and ovarian cancer patients

BackgroundPALB2 protein was recently identified as a partner of BRCA1 and BRCA2 which determines their proper function in DNA repair.MethodsInitially, the entire coding sequence of the PALB2 gene with exon/intron boundaries was evaluated by the PCR-SSCP and direct sequencing methods on 70 ovarian carcinomas. Sequence variants of interest were further studied on enlarged groups of ovarian carcinomas (total 339 non-consecutive ovarian carcinomas), blood samples from 334 consecutive sporadic and 648 consecutive familial breast cancer patients, and 1310 healthy controls from central Poland.ResultsTen types of sequence variants were detected, and among them four novel polymorphisms: c.2996+58T>C in intron 9; c.505C>A (p.L169I), c.618T>G (p.L206L), both in exon 4; and c.2135C>T (A712V) in exon 5 of the PALB2 gene. Another two polymorphisms, c.212-58A>C and c.2014G>C (E672Q) were always detected together, both in cancer (7.5% of patients) and control samples (4.9% of controls, p = 0.2). A novel germline truncating mutation, c.509_510delGA (p.R170fs) was found in exon 4: in 2 of 339 (0.6%) unrelated ovarian cancer patients, in 4 of 648 (0.6%) unrelated familial breast cancer patients, and in 1 of 1310 controls (0.08%, p = 0.1, p = 0.044, respectively). One ovarian cancer patient with the PALB2 mutation had also a germline nonsense mutation of the BRCA2 gene.ConclusionsThe c.509_510delGA is a novel PALB2 mutation that increases the risk of familial breast cancer. Occurrence of the same PALB2 alteration in seven unrelated women suggests that c.509_510delGA (p.R170fs) is a recurrent mutation for Polish population.

Prevalence of the most frequent BRCA1 mutations in Polish population

The purpose of our study was to establish the frequency and distribution of the four most common BRCA1 mutations in Polish general population and in a series of breast cancer patients. Analysis of the population frequency of 5382insC (c.5266dupC), 300T >G (p.181T >G), 185delAG (c.68_69delAG) and 3819del5 (c.3700_3704del5) mutations of the BRCA1 gene were performed on a group of respectively 16,849, 13,462, 12,485 and 3923 anonymous samples collected at birth in seven Polish provinces. The patient group consisted of 1845 consecutive female breast cancer cases. The most frequent BRCA1 mutation in the general population was 5382insC found in 29 out of 16,849 samples (0.17%). 300T >G and 3819del5 mutations were found in respectively 11 of 13,462 (0.08%) and four of 3923 (0.1%) samples. The population prevalence for combined Polish founder 5382insC and 300T >G mutations was 0.25% (1/400). The frequencies of 5382insC and 300T >G carriers among consecutive breast cancer cases were, respectively, 1.9% (35/1845) and 1.2% (18/1486). Comparing these data with the population frequency, we calculated the relative risk of breast cancer for 5382insC mutation at OR = 17 and for 300T >G mutation at OR = 26. Our results, based on large population studies, show high frequencies of founder 5382insC and 300T >G BRCA1 mutations in Polish general population. Carriage of one of these mutations is connected with a very high relative risk of breast cancer.

High frequency of BRCA1 founder mutations in Polish women with nonfamilial breast cancer

Possession of a BRCA1/2 mutation increases risk of contralateral breast and ovarian cancer recurrence and may have an impact on health management decisions, such as imaging screening, preventive surgical interventions and systemic therapies. A hospital-based study was conducted to assess the frequency and spectrum of pathogenic germline BRCA1 and BRCA2 mutations in Polish women with familial and nonfamilial breast cancer. Genomic DNA was extracted from 1581 women with breast cancer and from 2225 healthy individuals. For genotyping BRCA1 (5382insC, T300G, 3819del5, 185delAG, C5370T, 3875del4, 3896delT, 4153delA, 4184del4, 4160delAG, G5332A) mutations and BRCA2 (G1408T, 5467insT, 6174delT, 6192delAT, 6675delTA, 8138del5, 9152delT, C9610T, 9630delC) mutations, a Custom TaqMan (Applied Biosystems) PCR-based technology was adopted. A BRCA1 mutation was found in 26 and 12.5xa0% of women with familial breast cancer and in 13 and 8.3xa0% nonfamilial (sporadic) breast cancer, diagnosed before or after 50xa0years of age, respectively. A much lower frequency of BRCA2 mutation was observed. The predominance of seven BRCA1 mutations (5382insC, T300G, 3819del5, 185delAG, C5370T, 3875del4, 4153delA) studied in the Masovian voivodeship population confirmed a strong founder effect for BRCA1 mutations in the Polish population, and the results of BRCA2 testing confirmed a high diversity in the studied pathogenic mutations in BRCA2 gene. We propose offering inexpensive testing for the presence of BRCA1 founder mutations to all Polish women at the time of initial breast cancer diagnosis, regardless of the patient’s family history or age of disease onset.

Limited significance of family history for presence of BRCA1 gene mutation in Polish breast and ovarian cancer cases

It is estimated that about 5–10% of ovarian and 2–5% of all breast cancer patients are carriers of a germline BRCA1 or BRCA2 gene mutation. Most families with detected BRCA1 or BRCA2 gene mutation are qualified for molecular testing on the basis of family history of breast or ovarian cancers. The purpose of our study was to establish the frequency of positive family history of cancer in a series of Polish consecutive breast and ovarian cancer patients in two groups, with and without the BRCA1 gene mutations. We analysed the prevalence of four of the most common BRCA1 mutations: 5382insC (c.5266dupC), 300T>G (p.181T>G), 185delAG (c.68_69delAG) and 3819del5 (c.3700_3704del5). The patient group consisted of 1,845 consecutive female breast and 363 ovarian cancer cases. 19 out of 37 (51%) of BRCA1-positive ovarian cancer patients and 21 out of 55 (39%) BRCA1-positive breast cancer had negative family history of breast and/or ovarian cancer among first- and second-degree relatives. In ovarian cancer patients, negative family history was more frequent in those with 300T>G BRCA1 gene mutation than in 5382insC carriers. This finding indicates the necessity of searching for 300T>G mutation in families with a single diagnosis of ovarian cancer in family. The high frequency of mutations detected in breast cancer patients lacking obvious family history shows that breast cancer patients should be qualified for genetic testing on the basis of wide clinical and pathological criteria.

Common low-penetrance risk variants associated with breast cancer in Polish women

BackgroundBreast cancer is the most common type of cancer and the second leading cause of cancer-death among women in Poland. The known high-risk mutations account for 25% of familial aggregation cases and 5% of total breast cancer predisposition. Genome-wide association studies have identified a number of common low-penetrance genetic variants, but their contribution to disease risk differs between populations.MethodsTo verify selected associations with breast cancer susceptibility among Polish women, the replication study was performed, included 1424 women with breast cancer and 1788 healthy persons. Sixteen single-nucleotide polymorphisms (SNPs) were analyzed using TaqMan SNP Genotyping Assays. Allele frequency differences were tested using chi2-test implemented in PLINK v1.07 and Cochran-Armitage trend test was performed using R software.ResultsSignificant differences (Bonferroni corrected p-valuecor ≤ 0.0197) in the frequency of alleles distribution between all cancer and control subjects were observed for four (rs2736098, rs13281615, rs1219648, rs2981582) out of 16 SNPs. The same result was obtained for group of patients without high-risk BRCA1/2 mutations. The rs1219648 (p-valuecor ≤ 6.73E-03) and rs2981582 (p-valuecor ≤ 6.48E-03) SNPs showed significant association with both familial and sporadic cancers. Additionally, rs2736098 (p-valuecor ≤ 0.0234) was associated with only sporadic cancers; also in group without carriers of high-risk mutation. All these associations revealed their significance also in Cochran-Armitage trend test. Opposite to other SNPs, rs2736098 was associated with a decreased risk of breast cancer.ConclusionThe association of four known susceptibility SNPs, representing three individual loci, with breast cancer risk in Polish women was confirmed. One of them (rs2736098) seems to be specific for the Polish population. Due to the population differences in allele frequencies, identification of general genetic risk factors requires sets of association studies conducted on different populations.

Novel germline mutations in BRCA2 gene among breast and breast-ovarian cancer families from Poland

Identification of mutations in the BRCA2 gene and estimation of their clinical consequences for women and men treated in the Maria Sklodowska-Curie Memorial Cancer Center Warsaw, Poland in the years 1998–2008. The probands (97 women and 8 men) had a family history of breast and ovarian cancer (median age 46). The presence of molecular changes was examined in DNA isolated from peripheral blood lymphocytes. Germline mutations in 27 exons of the BRCA2 gene were screened by ‘touchdown’ PCR amplification, DHPLC and sequencing. Missense mutations were classified by multiple-sequences alignments of orthologous BRCA2 protein sequences with T-Coffee software. 39 molecular changes (8 novel) were identified in the BRCA2 gene in 105 investigated patients. In 12 patients the following pathogenic mutations were identified: 5467insT, 6174delT, 6192delAT, 6675delTA, 8141del5, 9152delT, 9326insA, 9631delC, IVS23-2Axa0>xa0G and E394X. The presence of 10 missense type mutations was detected including the following: D1420O, T1915xa0M, N3124I. The determination of pathogenic status of molecular variants detected in BRCA2 gene, described in the BIC mutation database as ‘UV’ depends on many parameters. Important is the assessment of the evolutionary conservation of their protein sequences and studying of the frequency of molecular variants detected in breast cancer patients and in population. A high diversity was found of the pathogenic mutations detected in BRCA2 gene in the Polish population.

Age at Onset of Bilateral Breast Cancer, the Presence of Hereditary BRCA1, BRCA2, CHEK2 Gene Mutations and Positive Family History of Cancer

Background: Our research focused on the relations between the age at onset of bilateral breast cancer and the prevalence of selected hereditary BRCA1, BRCA2 and CHEK2 gene mutations with reference to their positive family history of cancer. Methods: The DNA of peripheral blood lymphocytes of patients was examined for the presence of selected hereditary mutations in the BRCA1, BRCA2 and CHEK2 genes, using molecular biology techniques. The family history of neoplasms was also analyzed. Results: The following mutations in the BRCA1 gene were identified: 185delAG, C61G, 5382insC, 3875 del11ins7, and R1751X. In the BRCA2 gene, the 9631delC and A9599T mutations were found. In the CHEK2 gene, the 1100delC and I157T mutations were identified. BRCA1/2 gene mutations were identified in 19.4% of patients and CHEK2 gene mutations in 7%. Conclusions: It was shown that the presence of the mutations in the BRCA1/2 genes among patients with bilateral breast cancer is associated with an earlier occurrence of the first and the second breast cancer than in patients without hereditary mutations in these genes (a difference of 7.2–8.4 years). In patients with CHEK2 gene mutations, breast cancer occurred 2.1–3.8 years earlier than in patients without mutations in the CHEK2 gene.

Association of the BRCA1 promoter polymorphism rs11655505 with the risk of familial breast and/or ovarian cancer

Germline mutations in the BRCA1 tumor suppressor gene predispose affected individuals to breast cancer; however, incomplete cancer penetrance and the presence of phenocopies in BRCA1 families also indicate genetic and environmental modifiers of breast cancer risk. In this study, we have tested the single nucleotide polymorphism rs1655505 of the BRCA1 promoter, as candidate for the modifier of breast cancer risk. The polymorphic variants were genotyped in BRCA1-negative (729), familial breast and/or ovarian cancer cases (FBOC), including cases with a reported maternal history (154), nonfamilal (sporadic) cases (600), hereditary breast/ovarian cases with BRCA1 mutations (190) and population controls (1,590) from Central Poland. An association with the risk of FBOC was observed for the minor (T) allele and (TT) genotype (T: pxa0=xa00.006, ORxa0=xa01.40, 95xa0% CIxa0=xa01.10–1.79; TT: pxa0=xa00.001, ORxa0=xa02.23, 95xa0% CIxa0=xa01.37–3.62) in female cases with a reported maternal history, specifically in women with the onset of disease after 50xa0years of age (T: pxa0=xa00.004, ORxa0=xa01.77, 95xa0% CIxa0=xa01.20–2.62; TT: pxa0=xa00.001, ORxa0=xa03.7, 95xa0% CIxa0=xa01.62–8.46). The presented evidence suggests a need to conduct larger studies on the association between genetic variations at the BRCA1 promoter and the breast cancer risk, according to maternal/paternal lineage.