The APOBEC3B c.783delG Truncating Mutation Is Not Associated with an Increased Risk of Breast Cancer in the Polish Population.

The APOBEC3B gene belongs to a cluster of DNA-editing enzymes on chromosome 22 and encodes an activation-induced cytidine deaminase. A large deletion of APOBEC3B was associated with increased breast cancer risk, but the evidence is inconclusive. To investigate whether or not APOBEC3B is a breast cancer susceptibility gene, we sequenced this gene in 617 Polish patients with hereditary breast cancer. We detected a single recurrent truncating mutation (c.783delG, p.Val262Phefs) in four of the 617 (0.65%) hereditary cases by sequencing. We then genotyped an additional 12,484 women with unselected breast cancer and 3740 cancer-free women for the c.783delG mutation. The APOBEC3B c.783delG allele was detected in 60 (0.48%) unselected cases and 19 (0.51%) controls (OR = 0.95, 95% CI 0.56-1.59, p = 0.94). The allele was present in 8 of 1968 (0.41%) familial breast cancer patients from unselected cases (OR = 0.80, 95% CI 0.35-1.83, p = 0.74). Clinical characteristics of breast tumors in carriers of the APOBEC3B mutation and non-carriers were similar. No cancer type was more frequent in the relatives of mutation carriers than in those of non-carriers. We conclude the APOBEC3B deleterious mutation p.Val262Phefs does not confer breast cancer risk. These data do not support the hypothesis that APOBEC3B is a breast cancer susceptibility gene.

Variants in ATRIP are associated with breast cancer susceptibility in the Polish population and UK Biobank.

Several breast cancer susceptibility genes have been discovered, but more are likely to exist. To identify additional breast cancer susceptibility genes, we used the founder population of Poland and performed whole-exome sequencing on 510 women with familial breast cancer and 308 control subjects. We identified a rare mutation in ATRIP (GenBank: NM_130384.3: c.1152_1155del [p.Gly385Ter]) in two women with breast cancer. At the validation phase, we found this variant in 42/16,085 unselected Polish breast cancer-affected individuals and in 11/9,285 control subjects (OR = 2.14, 95% CI = 1.13-4.28, p = 0.02). By analyzing the sequence data of the UK Biobank study participants (450,000 individuals), we identified ATRIP loss-of-function variants among 13/15,643 breast cancer-affected individuals versus 40/157,943 control subjects (OR = 3.28, 95% CI = 1.76-6.14, p < 0.001). Immunohistochemistry and functional studies showed the ATRIP c.1152_1155del variant allele is weakly expressed compared to the wild-type allele, and truncated ATRIP fails to perform its normal function to prevent replicative stress. We showed that tumors of women with breast cancer who have a germline ATRIP mutation have loss of heterozygosity at the site of ATRIP mutation and genomic homologous recombination deficiency. ATRIP is a critical partner of ATR that binds to RPA coating single-stranded DNA at sites of stalled DNA replication forks. Proper activation of ATR-ATRIP elicits a DNA damage checkpoint crucial in regulating cellular responses to DNA replication stress. Based on our observations, we conclude ATRIP is a breast cancer susceptibility gene candidate linking DNA replication stress to breast cancer.

Common Variant in ALDH2 Modifies the Risk of Breast Cancer Among Carriers of the p.K3326* Variant in BRCA2.

PURPOSE: The BRCA2 p.K3326* variant is considered a low-penetrance variant for breast cancer. Aldehydes that accumulate in cells under insufficient aldehyde oxidation were most recently shown to trigger carcinogenesis by promoting depletion of BRCA2 protein. Allele T of the common variant rs10744777 in the ALDH2 gene was associated with reduced expression of aldehyde dehydrogenase, the main enzyme in aldehyde oxidation. We hypothesized that this allele could modify breast cancer risk in women with the BRCA2 p.K3326* low-penetrance variant through reduced function of ALDH2, increased accumulation of cellular aldehydes, and depletion of BRCA2 protein. MATERIALS AND METHODS: We genotyped 11,873 Polish women diagnosed with breast cancer and 7,615 ethnically matched controls for these two variants. Next, we extended our analysis of rs10744777 to 231 carriers of pathogenic BRCA2 mutations. RESULTS: BRCA2 p.K3326* variant was associated with significant increase in breast cancer risk only in those who were homozygous for the T allele of the ALDH2 rs10744777 variant (odds ratio = 1.72; 95% CI, 1.19 to 2.48; P = .003). The BRCA2 p.K3326* variant did not increase the risk of breast cancer among those who were heterozygous or homozygous for the C allele of the ALDH2 rs10744777 variant (odds ratio = 1.05; 95% CI, 0.73 to 1.51; P = .81). In the carriers of high-risk BRCA2 mutations, the TT genotype of rs10744777 conferred a modest (18%) and not significant increase in breast cancer risk. CONCLUSION: Our results suggest that BRCA2 p.K3326* variant, which is low-penetrance by itself, confers increased breast cancer risk on the background of the TT genotype of the ALDH2 rs10744777 variant in the Polish population.

Frequency of BRCA1 and BRCA2 mutations in ovarian cancer patients in South-East Poland.

BACKGROUND: Mutations in BRCA1 and BRCA2 genes are well-established risk factors of breast and ovarian cancer. In our former study, we observed that approximately 6% of unselected ovarian cancer patients in the region of Podkarpacie (South-East Poland) carry BRCA1 causative founder variants, which is significantly lower than in other regions of Poland. Therefore, it is deeply justified to do research based on the sequencing of whole BRCA1 and BRCA2 genes. METHODS: We examined 158 consecutive unselected cases of ovarian cancer patients from the region of Podkarpacie. We performed BRCA1 and BRCA2 genes Next-Generation Sequencing study in all cases. RESULTS: Altogether, in 18 of 158 (11.4%) ovarian cancer patients with BRCA1 or BRCA2 pathogenic mutations were found. BRCA1 pathogenic variants were detected in 11 of the 158 (7.0%) ovarian cancer cases. 10 of 11 (91%) detected BRCA1 mutations were founder mutations, detectable with the standard test used in Poland. BRCA2 pathogenic variants were found in 7 of the 158 (4.4%) cases. No BRCA2 pathogenic variants were founder mutations. The median age of patients at the diagnosis of the 18 hereditary ovarian cancers was 57.5 years. CONCLUSIONS: The frequency of BRCA1 or BRCA2 gene mutation carriers among patients with ovarian cancer from the Podkarpacie region is comparable to other regions of Poland. However, a significantly higher percentage of BRCA2 gene mutations was observed, that were not detectable with a standard test for detection of founder mutations. Diagnostics based only on testing the BRCA1/2 Polish founder mutations is characterized by relatively low sensitivity in the case of ovarian cancer patients from South-East Poland and should be supplemented by NGS study, in particular of the BRCA2 gene.

Risk of Second Primary Thyroid Cancer in Women with Breast Cancer.

The goal of this study was to estimate the risk of thyroid cancer following breast cancer and to identify therapeutic and genetic risk factors for the development of thyroid cancer after breast cancer. We followed 10,832 breast cancer patients for a mean of 14 years for new cases of thyroid cancer. All women were genotyped for three Polish founder mutations in BRCA1 (C61G, 4153delA, 5382insC) and four mutations in CHEK2 (1100delC, IVS2 + 1G/A, del5395, I157T). Information was collected on chemotherapy, radiotherapy, hormonal therapies, and oophorectomy. Of the 10,832 women, 53 (0.49%) developed a second primary thyroid cancer. Based on Polish population statistics, the expected number was 12.4 (SIR = 4.3). The ten-year risk of developing thyroid cancer was higher in women who carried a CHEK2 mutation (1.5%) than in women who carried no mutation (0.9%). The age-adjusted hazard ratio for developing thyroid cancer was 1.89 (0.46-7.79; p = 0.38) for those with a CHEK2 protein-truncating mutation and 2.75 (1.29-5.85; p = 0.009) for those with a CHEK2 missense mutation.

Whole-Exome Sequencing Identifies a Novel Germline Variant in PTK7 Gene in Familial Colorectal Cancer.

Colorectal cancer (CRC) is the third most frequently diagnosed malignancy worldwide. Only 5% of all CRC cases are due to germline mutations in known predisposition genes, and the remaining genetic burden still has to be discovered. In this study, we performed whole-exome sequencing on six members of a Polish family diagnosed with CRC and identified a novel germline variant in the protein tyrosine kinase 7 (inactive) gene (PTK7, ENST00000230419, V354M). Targeted screening of the variant in 1705 familial CRC cases and 1674 healthy elderly individuals identified the variant in an additional familial CRC case. Introduction of this variant in HT-29 cells resulted in increased cell proliferation, migration, and invasion; it also caused down-regulation of CREB, p21 and p53 mRNA and protein levels, and increased AKT phosphorylation. These changes indicated inhibition of apoptosis pathways and activation of AKT signaling. Our study confirmed the oncogenic function of PTK7 and supported its role in genetic predisposition of familial CRC.

Do BARD1 Mutations Confer an Elevated Risk of Prostate Cancer?

The current cancer testing gene panels tend to be comprehensive rather than site-specific. BARD1 is one of the genes commonly included in the multi-cancer testing panels. Mutations in BARD1 confer an increase in the risk for breast cancer, but it is not studied whether or not they predispose to prostate cancer. To establish if BARD1 mutations also predispose to prostate cancer, we screened BARD1 in 390 Polish patients with hereditary prostate cancer. No truncating mutations were identified by sequencing. We also genotyped 5715 men with unselected prostate cancer, and 10,252 controls for three recurrent BARD1 variants, including p.Q564X, p.R658C and p.R659=. Neither variant conferred elevated risk of prostate cancer (ORs between 0.84 and 1.15, p-values between 0.57 and 0.93) nor did they influence prostate cancer characteristics or survival. We conclude that men with a BARD1 mutation are not at elevated prostate cancer risk. It is not justified to inform men about increased prostate cancer risk in case of identification of a BARD1 mutation. However, a female relative of a man with a BARD1 mutation may benefit from this information and be tested for the mutation, because BARD1 is a breast cancer susceptibility gene.

Genetic predisposition to male breast cancer in Poland.

BACKGROUND: Breast cancer in men accounts for fewer than 1 % of all breast cancer cases diagnosed in men and women. Genes which predispose to male breast cancer include BRCA1 and BRCA2. The role of other genes is less clear. In Poland, 20 founder mutations in BRCA1, BRCA2, CHEK2, PALB2, NBN, RECQL are responsible for the majority of hereditary breast cancer cases in women, but the utility this genes panel has not been tested in men. METHODS: We estimated the prevalence of 20 alleles in six genes (BRCA1, BRCA2, CHEK2, PALB2, NBN, RECQL) in 165 Polish male breast cancer patients. We compared the frequency of selected variants in male breast cancer cases and controls. RESULTS: One of the 20 mutations was seen in 22 of 165 cases (13.3%). Only one BRCA1 mutation and two BRCA2 mutations were found. We observed statistically significant associations for PALB2 and CHEK2 truncating mutations. A PALB2 mutation was detected in four cases (OR = 11.66; p < 0.001). A CHEK2 truncating mutation was detected in five cases (OR = 2.93;p = 0.02). CONCLUSION: In conclusion, we recommend that a molecular test for BRCA1, BRCA2, PALB2 and CHEK2 recurrent mutations should be offered to male breast cancer patients in Poland.

PALB2 mutations and prostate cancer risk and survival.

BACKGROUND: The objective of this study was to establish the contribution of PALB2 mutations to prostate cancer risk and to estimate survival among PALB2 carriers. METHODS: We genotyped 5472 unselected men with prostate cancer and 8016 controls for two Polish founder variants of PALB2 (c.509_510delGA and c.172_175delTTGT). In patients with prostate cancer, the survival of carriers of a PALB2 mutation was compared to that of non-carriers. RESULTS: A PALB2 mutation was found in 0.29% of cases and 0.21% of controls (odds ratio (OR) = 1.38; 95% confidence interval (CI) 0.70-2.73; p = 0.45). PALB2 mutation carriers were more commonly diagnosed with aggressive cancers of high (8-10) Gleason score than non-carriers (64.3 vs 18.1%, p < 0.0001). The OR for high-grade prostate cancer was 8.05 (95% CI 3.57-18.15, p < 0.0001). After a median follow-up of 102 months, the age-adjusted hazard ratio for all-cause mortality associated with a PALB2 mutation was 2.52 (95% CI 1.40-4.54; p = 0.0023). The actuarial 5-year survival was 42% for PALB2 carriers and was 72% for non-carriers (p = 0.006). CONCLUSION: In Poland, PALB2 mutations predispose to an aggressive and lethal form of prostate cancer.

Recurrent Mutations in BRCA1, BRCA2, RAD51C, PALB2 and CHEK2 in Polish Patients with Ovarian Cancer.

The aim of the study was to analyze the frequency and magnitude of association of 21 recurrent founder germline mutations in BRCA1, BRCA2, PALB2, RAD51C, and CHEK2 genes with ovarian cancer risk among unselected patients in Poland. We genotyped 21 recurrent germline mutations in BRCA1 (9 mutations), BRCA2 (4 mutations), RAD51C (3 mutations), PALB2 (2 mutations), and CHEK2 (3 mutations) among 2270 Polish ovarian cancer patients and 1743 healthy controls, and assessed the odds ratios (OR) for developing ovarian cancer for each gene. Mutations were detected in 369 out of 2095 (17.6%) unselected ovarian cancer cases and 117 out of 1743 (6.7%) unaffected controls. The ovarian cancer risk was associated with mutations in BRCA1 (OR = 40.79, 95% CI: 18.67-114.78; p = 0.29 × 10-15), in BRCA2 (OR = 25.98; 95% CI: 1.55-434.8; p = 0.001), in RAD51C (OR = 6.28; 95% CI 1.77-39.9; p = 0.02), and in PALB2 (OR 3.34; 95% CI: 1.06-14.68; p = 0.06). There was no association found for CHEK2. We found that pathogenic mutations in BRCA1, BRCA2, RAD51C or PALB2 are responsible for 12.5% of unselected cases of ovarian cancer. We recommend that all women with ovarian cancer in Poland and first-degree female relatives should be tested for this panel of 18 mutations.

Recurrent PALB2 mutations and the risk of cancers of bladder or kidney in Polish population.

INTRODUCTION: The role of PALB2 in carcinogenesis remains to be clarified. Our main goal was to determine the prevalence of PALB2 (509_510delGA and 172_175delTTGT) mutations in bladder and kidney cancer patients from Polish population. MATERIALS AND METHODS: 1413 patients with bladder and 810 cases with kidney cancer and 4702 controls were genotyped for two PALB2 variants: 509_510delGA and 172_175delTTGT. RESULTS: Two mutations of PALB2 gene were detected in 5 of 1413 (0.35%) unselected bladder cases and in 10 of 4702 controls (odds ratio [OR], 1.7; 95% CI 0.56-4.88; p = 0.52). Among 810 unselected kidney cancer cases two PALB2 mutations were reported in two patients (0,24%) (odds ratio [OR], (OR = 1.2; 95% CI 0.25-5.13; p = 0.84). In cases with mutations in PALB2 gene cancer family history was negative. CONCLUSION: We found no difference in the prevalence of recurrent PALB2 mutations between cases and healthy controls. The mutations in PALB2 gene seem not to play a major role in bladder and kidney cancer development in Polish patients.

Prevalence of germline TP53 variants among early-onset breast cancer patients from Polish population.

BACKGROUND: The objective of this study was to determine spectrum and prevalence of germline mutations in TP53 gene among Polish women with early-onset breast cancer (BC), which has not been determined until now. METHODS: A cohort of 100 females with BC diagnosed ≤ 30 years of age and with a positive family history of cancer was used as a discovery cohort. 1880 women with BC ≤ 45 years old and a control group of 2000 healthy women were genotyped as a replication phase of this study. RESULTS: Four heterozygous pathogenic missense mutations were detected in a group of 100 patients with early-onset breast cancer. On the basis of software prediction and available literature data, all these variants were defined as pathogenic. None of these TP53 variants were detected among 1880 breast cancer patients and 2000 healthy controls. No large mutations were found among early-onset cases using MLPA reaction. CONCLUSION: Germline pathogenic TP53 variants were found in 4% early-onset Polish BC patients. No founder mutations were identified in Polish population. To improve the treatment and surveillance screening, the search for germline TP53 pathogenic variants is recommended for all female BC cases diagnosed ≤ 30 years old.

Mutations in ATM, NBN and BRCA2 predispose to aggressive prostate cancer in Poland.

In designing national strategies for genetic testing, it is important to define the full spectrum of pathogenic mutations in prostate cancer (PCa) susceptibility genes. To investigate the frequency of mutations in PCa susceptibility genes in Polish familial PCa cases and to estimate gene-related PCa risks and probability of aggressive disease, we analyzed the coding regions of 14 genes by exome sequencing in 390 men with familial prostate cancer and 308 cancer-free controls. We compared the mutation frequencies between PCa cases and controls. We also compared clinical characteristics of prostate cancers between mutation carriers and noncarriers. Of the 390 PCa cases, 76 men (19.5%) carried a mutation in BRCA1, BRCA2, NBN, ATM, CHEK2, HOXB13, MSH2 or MSH6 genes. No mutations were found in BRIP1, PTEN, TP53, MLH1, PMS2 and SPOP. Significant associations with familial PCa risk were observed for CHEK2, NBN, ATM, and HOXB13. High-grade (Gleason 8-10) tumors were seen in 56% of BRCA2, NBN or ATM carriers, compared to 21% of patients who tested negative for mutations in these genes (OR = 4.7, 95% CI 2.0-10.7, P = .0003). In summary, approximately 20% of familial prostate cancer cases in Poland can be attributed to mutations in eight susceptibility genes. Carriers of mutations in BRCA2, NBN and ATM develop aggressive disease and may benefit from intensified screening and/or chemotherapy.

Prevalence of Recurrent Mutations Predisposing to Breast Cancer in Early-Onset Breast Cancer Patients from Poland.

There are twenty recurrent mutations in six breast-cancer-predisposing genes in Poland (BRCA1, BRCA2, CHEK2, PALB2, NBN, and RECQL). The frequencies of the twenty alleles have not been measured in a large series of early-onset breast cancer patients from Poland unselected for family history. We genotyped 2464 women with breast cancer diagnosed below age 41 years for twenty recurrent germline mutations in six genes, including BRCA1, BRCA2 CHEK2, PALB2, NBN, and RECQL. A mutation in one of the six genes was identified in 419 of the 2464 early-onset breast cancer cases (17%), including 22.4% of those cases diagnosed below age 31. The mutation frequency was 18.8% for familial breast cancer cases and 6% for non-familial cases. Among women with breast cancer below age 31, the mutation frequency was 23.6% for familial cases and 17.4% in non-familial cases. The majority of mutations (76.2%) were seen in BRCA1 and BRCA2. In Poland, a panel of twenty recurrent mutations in six genes can identify a genetic basis for a high percentage of early-onset cases and testing is recommended for all women with breast cancer at age 40 or below.

The effect of sample size on polygenic hazard models for prostate cancer.

We determined the effect of sample size on performance of polygenic hazard score (PHS) models in prostate cancer. Age and genotypes were obtained for 40,861 men from the PRACTICAL consortium. The dataset included 201,590 SNPs per subject, and was split into training and testing sets. Established-SNP models considered 65 SNPs that had been previously associated with prostate cancer. Discovery-SNP models used stepwise selection to identify new SNPs. The performance of each PHS model was calculated for random sizes of the training set. The performance of a representative Established-SNP model was estimated for random sizes of the testing set. Mean HR98/50 (hazard ratio of top 2% to average in test set) of the Established-SNP model increased from 1.73 [95% CI: 1.69-1.77] to 2.41 [2.40-2.43] when the number of training samples was increased from 1 thousand to 30 thousand. Corresponding HR98/50 of the Discovery-SNP model increased from 1.05 [0.93-1.18] to 2.19 [2.16-2.23]. HR98/50 of a representative Established-SNP model using testing set sample sizes of 0.6 thousand and 6 thousand observations were 1.78 [1.70-1.85] and 1.73 [1.71-1.76], respectively. We estimate that a study population of 20 thousand men is required to develop Discovery-SNP PHS models while 10 thousand men should be sufficient for Established-SNP models.

A Genetic Risk Score to Personalize Prostate Cancer Screening, Applied to Population Data.

BACKGROUND: A polygenic hazard score (PHS), the weighted sum of 54 SNP genotypes, was previously validated for association with clinically significant prostate cancer and for improved prostate cancer screening accuracy. Here, we assess the potential impact of PHS-informed screening. METHODS: United Kingdom population incidence data (Cancer Research United Kingdom) and data from the Cluster Randomized Trial of PSA Testing for Prostate Cancer were combined to estimate age-specific clinically significant prostate cancer incidence (Gleason score ≥7, stage T3-T4, PSA ≥10, or nodal/distant metastases). Using HRs estimated from the ProtecT prostate cancer trial, age-specific incidence rates were calculated for various PHS risk percentiles. Risk-equivalent age, when someone with a given PHS percentile has prostate cancer risk equivalent to an average 50-year-old man (50-year-standard risk), was derived from PHS and incidence data. Positive predictive value (PPV) of PSA testing for clinically significant prostate cancer was calculated using PHS-adjusted age groups. RESULTS: The expected age at diagnosis of clinically significant prostate cancer differs by 19 years between the 1st and 99th PHS percentiles: men with PHS in the 1st and 99th percentiles reach the 50-year-standard risk level at ages 60 and 41, respectively. PPV of PSA was higher for men with higher PHS-adjusted age. CONCLUSIONS: PHS provides individualized estimates of risk-equivalent age for clinically significant prostate cancer. Screening initiation could be adjusted by a man's PHS. IMPACT: Personalized genetic risk assessments could inform prostate cancer screening decisions.

Inherited Variants in BLM and the Risk and Clinical Characteristics of Breast Cancer.

Bloom Syndrome is a rare recessive disease which includes a susceptibility to various cancers. It is caused by homozygous mutations of the BLM gene. To investigate whether heterozygous carriers of a BLM mutation are predisposed to breast cancer, we sequenced BLM in 617 patients from Polish families with a strong family history of breast cancer. We detected a founder mutation (c.1642C>T, p.Gln548Ter) in 3 of the 617 breast cancer patients (0.49%) who were sequenced. Then, we genotyped 14,804 unselected breast cancer cases and 4698 cancer-free women for the founder mutation. It was identified in 82 of 14,804 (0.55%) unselected cases and in 26 of 4698 (0.55%) controls (OR = 1.0; 95%CI 0.6-1.6). Clinical characteristics of breast cancers in the BLM mutation carriers and non-carriers were similar. Loss of the wild-type BLM allele was not detected in cancers from the BLM mutation carriers. No cancer type was more common in the relatives of mutation carriers compared to relatives of non-carriers. The BLM founder mutation p.Gln548Ter, which in a homozygous state is a cause of Bloom syndrome, does not appear to predispose to breast cancer in a heterozygous state. The finding casts doubt on the designation of BLM as an autosomal dominant breast cancer susceptibility gene.

Inherited variants in XRCC2 and the risk of breast cancer.

BACKGROUND: XRCC2 participates in homologous recombination and in DNA repair. XRCC2 has been reported to be a breast cancer susceptibility gene and is now included in several breast cancer susceptibility gene panels. METHODS: We sequenced XRCC2 in 617 Polish women with familial breast cancer and found a founder mutation. We then genotyped 12,617 women with breast cancer and 4599 controls for the XRCC2 founder mutation. RESULTS: We identified a recurrent truncating mutation of XRCC2 (c.96delT, p.Phe32fs) in 3 of 617 patients with familial breast cancer who were sequenced. The c.96delT mutation was then detected in 29 of 12,617 unselected breast cancer cases (0.23%) compared to 11 of 4599 cancer-free women (0.24%) (OR = 0.96; 95% CI 0.48-1.93). The mutation frequency in 1988 women with familial breast cancer was 0.2% (OR = 0.84, 95% CI 0.27-2.65). Breast cancers in XRCC2 mutation carriers and non-carriers were similar with respect to age of diagnosis and clinical characteristics. Loss of the wild-type XRCC2 allele was observed only in one of the eight breast cancers from patients who carried the XRCC2 mutation. No cancer type was more common in first- or second-degree relatives of XRCC2 mutation carriers than in relatives of the non-carriers. CONCLUSION: XRCC2 c.96delT is a protein-truncating founder variant in Poland. There is no evidence that this mutation predisposes to breast cancer (and other cancers). It is premature to consider XRCC2 as a breast cancer-predisposing gene.

Allelic modification of breast cancer risk in women with an NBN mutation.

BACKGROUND: NBN 657del5 founder mutation predisposes to breast and prostate cancer. Recently, it has been reported that the pathogenicity of this mutation with regard to prostate cancer risk is modified by a missense variant of the same gene (E185Q). METHODS: To evaluate the interaction of the 657del5 and E185Q founder alleles of NBN on breast cancer risk in Poland, 4964 women with breast cancer and 6152 controls were genotyped for these two recurrent variants of NBN (657del5 truncating variant and E185Q missense variant). RESULTS: The NBN 657del5 mutation was detected in 57 of 4964 unselected cases and in 35 of 6152 controls (OR = 2.0, p = 0.001). The E185Q GG genotype was detected in 2167 of 4964 unselected cases and in 2617 of 6152 controls (OR = 1.04, p = 0.3). In carriers of the 657del5 deletion, the elevated cancer risk was restricted to women with the GG genotype of the E185Q variant (OR = 3.6, 95% CI 1.9-6.6; p < 0.0001). Among women with other E185Q genotypes, the OR associated with 657del5 was 1.0 (95% CI 0.5-1.8; p = 0.9). The interaction between the two alleles was statistically significant (homogeneity p = 0.003). CONCLUSION: In Poland, the pathogenicity of the NBN 657del5 mutation is restricted to women with a homozygous GG genotype of missense variant of the same gene (E185Q). This is the first clear example whereby a moderate penetrance breast cancer gene is impacted by a genetic modifier.

The spectrum of mutations predisposing to familial breast cancer in Poland.

To optimize genetic testing, it is necessary to establish the spectrum of breast cancer-predisposing mutations in particular ethnic groups. We studied 1,018 women with a strong family history for breast cancer (families with hereditary breast cancer; HBC) from genetically homogenous population of Poland, which is populated by ethnic Slavs, for mutations in 14 cancer susceptibility genes. Additionally, we compared the frequency of candidate pathogenic variants in breast cancer cases and controls. Germline mutations were detected in 512 of 1,018 probands with breast cancer (50.3%), including BRCA1/2 mutations detected in 420 families and non-BRCA mutations seen in 92 families. Thirteen BRCA1/2 founder mutations represented 84% of all BRCA1/2-positive cases. Seven founder mutations of CHEK2, PALB2, NBN and RECQL represented 73% of all non-BRCA-positive cases. Odds ratios for hereditary breast cancer were 87.6 for BRCA1, 15.4 for PALB2, 7.2 for CHEK2, 2.8 for NBN and 15.8 for RECQL. Odds ratios for XRCC2, BLM and BARD1 were below 1.3. In summary, we found that 20 founder mutations in six genes (BRCA1/2, CHEK2, PALB2, NBN and RECQL) are responsible for 82% of Polish hereditary breast cancer families. A simple test for these 20 mutations will facilitate genetic testing for breast cancer susceptibility in Poland. It may also facilitate genetic testing for breast cancer susceptibility in other Slavic populations and women of Slavic descent worldwide.