PALB2-mutated human mammary cells display a broad spectrum of morphological and functional abnormalities induced by increased TGFß signaling.

Heterozygous mutations in any of three major genes, BRCA1, BRCA2 and PALB2, are associated with high-risk hereditary breast cancer susceptibility frequently seen as familial disease clustering. PALB2 is a key interaction partner and regulator of several vital cellular activities of BRCA1 and BRCA2, and is thus required for DNA damage repair and alleviation of replicative and oxidative stress. Little is however known about how PALB2-deficiency affects cell function beyond that, especially in the three-dimensional setting, and also about its role during early steps of malignancy development. To answer these questions, we have generated biologically relevant MCF10A mammary epithelial cell lines with mutations that are comparable to certain clinically important PALB2 defects. We show in a non-cancerous background how both mono- and biallelically PALB2-mutated cells exhibit gross spontaneous DNA damage and mitotic aberrations. Furthermore, PALB2-deficiency disturbs three-dimensional spheroid morphology, increases the migrational capacity and invasiveness of the cells, and broadly alters their transcriptome profiles. TGFß signaling and KRT14 expression are enhanced in PALB2-mutated cells and their inhibition and knock down, respectively, lead to partial restoration of cell functions. KRT14-positive cells are also more abundant with DNA damage than KRT14-negative cells. The obtained results indicate comprehensive cellular changes upon PALB2 mutations, even in the presence of half dosage of wild type PALB2 and demonstrate how PALB2 mutations may predispose their carriers to malignancy.

Exome sequencing identified rare recurrent copy number variants and hereditary breast cancer susceptibility.

Copy number variants (CNVs) are a major source of genetic variation and can disrupt genes or affect gene dosage. They are known to be causal or underlie predisposition to various diseases. However, the role of CNVs in inherited breast cancer susceptibility has not been thoroughly investigated. To address this, we performed whole-exome sequencing based analysis of rare CNVs in 98 high-risk Northern Finnish breast cancer cases. After filtering, selected candidate alleles were validated and characterized with a combination of orthogonal methods, including PCR-based approaches, optical genome mapping and long-read sequencing. This revealed three recurrent alterations: a 31 kb deletion co-occurring with a retrotransposon insertion (delins) in RAD52, a 13.4 kb deletion in HSD17B14 and a 64 kb partial duplication of RAD51C. Notably, all these genes encode proteins involved in pathways previously identified as essential for breast cancer development. Variants were genotyped in geographically matched cases and controls (altogether 278 hereditary and 1983 unselected breast cancer cases, and 1229 controls). The RAD52 delins and HSD17B14 deletion both showed significant enrichment among cases with indications of hereditary disease susceptibility. RAD52 delins was identified in 7/278 cases (2.5%, P = 0.034, OR = 2.86, 95% CI = 1.10-7.45) and HSD17B14 deletion in 8/278 cases (2.9%, P = 0.014, OR = 3.28, 95% CI = 1.31-8.23), the frequency of both variants in the controls being 11/1229 (0.9%). This suggests a role for RAD52 and HSD17B14 in hereditary breast cancer susceptibility. The RAD51C duplication was very rare, identified only in 2/278 of hereditary cases and 2/1229 controls (P = 0.157, OR = 4.45, 95% CI = 0.62-31.70). The identification of recurrent CNVs in these genes, and especially the relatively high frequency of RAD52 and HSD17B14 alterations in the Finnish population, highlights the importance of studying CNVs alongside single nucleotide variants when searching for genetic factors underlying hereditary disease predisposition.

Targeting collagen XVIII improves the efficiency of ErbB inhibitors in breast cancer models.

The tumor extracellular matrix (ECM) critically regulates cancer progression and treatment response. Expression of the basement membrane component collagen XVIII (ColXVIII) is induced in solid tumors, but its involvement in tumorigenesis has remained elusive. We show here that ColXVIII was markedly upregulated in human breast cancer (BC) and was closely associated with a poor prognosis in high-grade BCs. We discovered a role for ColXVIII as a modulator of epidermal growth factor receptor tyrosine kinase (ErbB) signaling and show that it forms a complex with ErbB1 and -2 (also known as EGFR and human epidermal growth factor receptor 2 [HER2]) and α6-integrin to promote cancer cell proliferation in a pathway involving its N-terminal portion and the MAPK/ERK1/2 and PI3K/AKT cascades. Studies using Col18a1 mouse models crossed with the mouse mammary tumor virus-polyoma virus middle T antigen (MMTV-PyMT) mammary carcinogenesis model showed that ColXVIII promoted BC growth and metastasis in a tumor cell-autonomous manner. Moreover, the number of mammary cancer stem cells was significantly reduced in the MMTV-PyMT and human cell models upon ColXVIII inhibition. Finally, ablation of ColXVIII substantially improved the efficacy of ErbB-targeting therapies in both preclinical models. In summary, ColXVIII was found to sustain the stemness properties of BC cells and tumor progression and metastasis through ErbB signaling, suggesting that targeting ColXVIII in the tumor milieu may have important therapeutic potential.

ABRAXAS1 orchestrates BRCA1 activities to counter genome destabilizing repair pathways-lessons from breast cancer patients.

It has been well-established that mutations in BRCA1 and BRCA2, compromising functions in DNA double-strand break repair (DSBR), confer hereditary breast and ovarian cancer risk. Importantly, mutations in these genes explain only a minor fraction of the hereditary risk and of the subset of DSBR deficient tumors. Our screening efforts identified two truncating germline mutations in the gene encoding the BRCA1 complex partner ABRAXAS1 in German early-onset breast cancer patients. To unravel the molecular mechanisms triggering carcinogenesis in these carriers of heterozygous mutations, we examined DSBR functions in patient-derived lymphoblastoid cells (LCLs) and in genetically manipulated mammary epithelial cells. By use of these strategies we were able to demonstrate that these truncating ABRAXAS1 mutations exerted dominant effects on BRCA1 functions. Interestingly, we did not observe haploinsufficiency regarding homologous recombination (HR) proficiency (reporter assay, RAD51-foci, PARP-inhibitor sensitivity) in mutation carriers. However, the balance was shifted to use of mutagenic DSBR-pathways. The dominant effect of truncated ABRAXAS1 devoid of the C-terminal BRCA1 binding site can be explained by retention of the N-terminal interaction sites for other BRCA1-A complex partners like RAP80. In this case BRCA1 was channeled from the BRCA1-A to the BRCA1-C complex, which induced single-strand annealing (SSA). Further truncation, additionally deleting the coiled-coil region of ABRAXAS1, unleashed excessive DNA damage responses (DDRs) de-repressing multiple DSBR-pathways including SSA and non-homologous end-joining (NHEJ). Our data reveal de-repression of low-fidelity repair activities as a common feature of cells from patients with heterozygous mutations in genes encoding BRCA1 and its complex partners.

Evaluating the role of CHEK2 p.(Asp438Tyr) allele in inherited breast cancer predisposition.

CHEK2 is a well-established breast cancer susceptibility gene. The most frequent pathogenic CHEK2 variant is 1100delC, a loss-of-function mutation conferring 2-fold risk for breast cancer. This gene also harbors other rare variants encountered in the clinical gene panels for hereditary cancer. One of these is CHEK2 c.1312 G > T, p.(Asp438Tyr) in the kinase domain of the protein, but due to its rarity its clinical significance for breast cancer predisposition has remained unclear. Here, we tested the prevalence of CHEK2 p.(Asp438Tyr) allele showing enrichment in the Northern Finnish population, in a total of 2284 breast cancer patients from this geographical region. Genotyping was performed for DNA samples extracted from peripheral blood using high-resolution melt analysis. Fourteen CHEK2 p.(Asp438Tyr) carriers were identified (14/2284, 0.6%, P = 0.67): two in the cohort of breast cancer cases with the indication of inherited disease susceptibility (2/281, 0.7%, P = 1.00) and twelve in the breast cancer cohort unselected for the family history of disease and age at disease onset (12/2003, 0.6%, P = 0.66). This frequency did not differ from the frequency in the general population (10/1299, 0.8%). No CHEK2 p.(Asp438Tyr) homozygotes were identified. Our results indicate that CHEK2 p.(Asp438Tyr) carriers do not have an increased risk for breast cancer and the classification of the CHEK2 p.(Asp438Tyr) variant can be changed from the variant of uncertain significance (VUS) to likely benign for breast cancer.

Truncating TINF2 p.Tyr312Ter variant and inherited breast cancer susceptibility.

TINF2 is a critical subunit of the shelterin complex, which protects and maintains the length of telomeres. Pathogenic missense and truncating TINF2 mutations are causative for dyskeratosis congenita (DC), a rare, dominantly inherited bone marrow failure syndrome characterized by mucocutaneous abnormalities and cancer predisposition. Recent reports indicate that specific TINF2 truncating mutations act as high penetrance cancer predisposition alleles outside DC context, including breast cancer in their tumor spectrum. Here, we have evaluated the role of germline mutations in TINF2 and other shelterin genes in inherited breast cancer susceptibility using exome sequencing data from 98 Northern Finnish breast cancer cases with indication of inherited disease predisposition as a discovery cohort. A single protein truncating variant, TINF2 p.Tyr312Ter, was identified in one of the cases (1/98), and four more carriers were observed in the subsequently genotyped unselected breast cancer cohort (4/1904). None of the carriers were reported to have DC. TINF2 p.Tyr312Ter resulted in stable short form of mRNA transcript, and normal telomere length has been indicated by a recent report. Although recurrent in cases (total of 5/2095), TINF2 p.Tyr312Ter is also present in Finnish population controls (8/12,517), and the observed 4-fold higher frequency in cases falls at most into the range of moderate breast cancer risk alleles (OR 3.74, 95% CI 1.22-11.45, p = 0.029). Current results indicate that not all TINF2 truncating variants are high cancer risk alleles and add further evidence that different TINF2 mutations can have very diverse effects on the disease phenotype.

Exome sequencing identifies a recurrent variant in SERPINA3 associating with hereditary susceptibility to breast cancer.

BACKGROUND: Breast cancer is strongly influenced by hereditary risk factors. Yet, the known susceptibility genes and genomic loci explain only about half of the familial component of the disease. To identify novel breast cancer predisposing gene defects, here we have performed massive parallel sequencing for Northern Finnish breast cancer cases. METHODS: Ninety-eight breast cancer cases with indication of hereditary disease susceptibility were exome sequenced. Data filtering strategy focused on predictably deleterious rare variants that were still enriched in the sequenced cohort. Findings were confirmed with additional, geographically matched breast cancer cohorts. RESULTS: A recurrent heterozygous splice acceptor variant, c.918-1G>C, in SERPINA3, was identified, and it was significantly enriched both in the hereditary (6/201, 3.0%, p = 0.006, OR 5.1, 95% CI 1.7-14.8) and unselected breast cancer cohort (26/1569, 1.7%, p = 0.009, OR 2.8, 95% CI 1.3-6.2). SERPINA3 c.918-1G>C carriers were also significantly more likely to have a rare tumor subtype, medullary breast cancer, than the non-carriers (4/26, 15.4%, p = 0.000014, OR 42.9, 95% CI 11.7-157.1). CONCLUSION: These findings demonstrate that c.918-1G>C germline variant in SERPINA3 gene, encoding a member of the serine protease inhibitor class, is a novel breast cancer predisposing allele.

Evaluating the role of NTHL1 p.Q90* allele in inherited breast cancer predisposition.

BACKGROUND: Rare protein truncating variants of NTHL1 gene are causative for the recently described, recessively inherited NTHL1 tumor syndrome that is characterized by an increased lifetime risk for colorectal cancer, colorectal polyposis, and breast cancer. Although there is strong evidence for breast cancer being a part of the cancer spectrum in these families, the role of pathogenic NTHL1 variants in breast cancer susceptibility in general population remains unclear. METHODS: We tested the prevalence of NTHL1 nonsense variant c.268C>T, p.Q90*, which is the major allele in NTHL1 families and also shows enrichment in the Finnish population, in a total of 1333 breast cancer patients. Genotyping was performed for DNA samples extracted from peripheral blood by using high-resolution melt analysis. RESULTS: Sixteen NTHL1 p.Q90* heterozygous carriers were identified (1.2%, p = 0.61): 5 in hereditary cohort (n = 234, 2.1%, p = 0.39) and 11 in unselected cohort (n = 1099, 1.0%, p = 0.36). This frequency is equal to that in the general population (19/1324, 1.4%). No NTHL1 p.Q90* homozygotes were identified. CONCLUSION: Our results indicate that NTHL1 p.Q90* heterozygous carriers do not have an increased risk for breast cancer and that the variant is unlikely to be a significant contributor to breast cancer risk at the population level.

Erratum: Publisher Correction: Homologous recombination DNA repair defects in PALB2-associated breast cancers.

[This corrects the article DOI: 10.1038/s41523-019-0115-9.].

BRCA1 mislocalization leads to aberrant DNA damage response in heterozygous ABRAXAS1 mutation carrier cells.

Whilst heterozygous germline mutations in the ABRAXAS1 gene have been associated with a hereditary predisposition to breast cancer, their effect on promoting tumourigenesis at the cellular level has not been explored. Here, we demonstrate in patient-derived cells that the Finnish ABRAXAS1 founder mutation (c.1082G > A, Arg361Gln), even in the heterozygous state leads to decreased BRCA1 protein levels as well as reduced nuclear localization and foci formation of BRCA1 and CtIP. This causes disturbances in basal BRCA1-A complex localization, which is reflected by a restraint in error-prone DNA double-strand break repair pathway usage, attenuated DNA damage response and deregulated G2-M checkpoint control. The current study clearly demonstrates how the Finnish ABRAXAS1 founder mutation acts in a dominant-negative manner on BRCA1 to promote genome destabilization in heterozygous carrier cells.

Homologous recombination DNA repair defects in PALB2-associated breast cancers.

Mono-allelic germline pathogenic variants in the Partner And Localizer of BRCA2 (PALB2) gene predispose to a high-risk of breast cancer development, consistent with the role of PALB2 in homologous recombination (HR) DNA repair. Here, we sought to define the repertoire of somatic genetic alterations in PALB2-associated breast cancers (BCs), and whether PALB2-associated BCs display bi-allelic inactivation of PALB2 and/or genomic features of HR-deficiency (HRD). Twenty-four breast cancer patients with pathogenic PALB2 germline mutations were analyzed by whole-exome sequencing (WES, n = 16) or targeted capture massively parallel sequencing (410 cancer genes, n = 8). Somatic genetic alterations, loss of heterozygosity (LOH) of the PALB2 wild-type allele, large-scale state transitions (LSTs) and mutational signatures were defined. PALB2-associated BCs were found to be heterogeneous at the genetic level, with PIK3CA (29%), PALB2 (21%), TP53 (21%), and NOTCH3 (17%) being the genes most frequently affected by somatic mutations. Bi-allelic PALB2 inactivation was found in 16 of the 24 cases (67%), either through LOH (n = 11) or second somatic mutations (n = 5) of the wild-type allele. High LST scores were found in all 12 PALB2-associated BCs with bi-allelic PALB2 inactivation sequenced by WES, of which eight displayed the HRD-related mutational signature 3. In addition, bi-allelic inactivation of PALB2 was significantly associated with high LST scores. Our findings suggest that the identification of bi-allelic PALB2 inactivation in PALB2-associated BCs is required for the personalization of HR-directed therapies, such as platinum salts and/or PARP inhibitors, as the vast majority of PALB2-associated BCs without PALB2 bi-allelic inactivation lack genomic features of HRD.

Machine learning identifies interacting genetic variants contributing to breast cancer risk: A case study in Finnish cases and controls.

We propose an effective machine learning approach to identify group of interacting single nucleotide polymorphisms (SNPs), which contribute most to the breast cancer (BC) risk by assuming dependencies among BCAC iCOGS SNPs. We adopt a gradient tree boosting method followed by an adaptive iterative SNP search to capture complex non-linear SNP-SNP interactions and consequently, obtain group of interacting SNPs with high BC risk-predictive potential. We also propose a support vector machine formed by the identified SNPs to classify BC cases and controls. Our approach achieves mean average precision (mAP) of 72.66, 67.24 and 69.25 in discriminating BC cases and controls in KBCP, OBCS and merged KBCP-OBCS sample sets, respectively. These results are better than the mAP of 70.08, 63.61 and 66.41 obtained by using a polygenic risk score model derived from 51 known BC-associated SNPs, respectively, in KBCP, OBCS and merged KBCP-OBCS sample sets. BC subtype analysis further reveals that the 200 identified KBCP SNPs from the proposed method performs favorably in classifying estrogen receptor positive (ER+) and negative (ER-) BC cases both in KBCP and OBCS data. Further, a biological analysis of the identified SNPs reveals genes related to important BC-related mechanisms, estrogen metabolism and apoptosis.

Rare missense mutations in RECQL and POLG associate with inherited predisposition to breast cancer.

Several known breast cancer susceptibility genes with moderate-to-high risk alleles encode proteins involved in DNA damage response (DDR). As these explain less than half of the hereditary breast cancer cases, additional predisposing alleles are likely to be discovered. Many of the previous studies utilizing massive parallel sequencing have focused on the protein-truncating variants, and the role of rare missense mutations has remained poorly addressed. To identify novel susceptibility factors, we have systematically analyzed the data from our parallel sequencing of 796 DDR genes in 189 Northern Finnish hereditary breast cancer patients for rare missense variants, predicted as deleterious. Thirty-five variants were studied here for the disease association using Finnish breast cancer case (n = 492-2,035) and control (n = 277-1,539) cohorts. As a result, two missense variants in genes involved in DNA replication, RECQL p.I156M and POLG p.L392V, the former involving genomic and the latter mitochondrial DNA replication, showed significant association with risk of breast cancer. Rare RECQL p.I156M allele was observed in breast cancer cases only (6/1,946, 0.3%, p = 0.043), whereas POLG p.L392V was two times more frequent in breast cancer cases (53/2,238, 2.4%) compared to controls (18/1,539, 1.2%, OR = 2.1, 95% CI 1.2-3.5, p = 0.010). Based on the current genetic data, both RECQL p.I156M and POLG p.L392V represent novel breast cancer predisposing alleles.

FANCM mutation c.5791C>T is a risk factor for triple-negative breast cancer in the Finnish population.

PURPOSE: The FANCM c.5101C>T nonsense mutation was previously found to associate with breast cancer in the Finnish population, especially among triple-negative cases. Here, we studied the prevalence of three other FANCM variants: c.5791C>T, which has been reported to predispose to familial breast cancer, and the c.4025_4026delCT and c.5293dupA variants recently identified in Finnish cancer patients. METHODS: We genotyped the FANCM c.5791C>T mutation in 4806 invasive breast cancer patients, including BRCA1/2 mutation negative familial cases and unselected cases, and in 2734 healthy population controls from four different geographical areas of Finland. The association of the mutation with breast cancer risk among patient subgroups was statistically evaluated. We further analyzed the combined risk associated with c.5101C>T and c.5791C>T mutations. We also genotyped 526 unselected ovarian cancer patients for the c.5791C>T mutation and 862 familial breast cancer patients for the c.4025_4026delCT and c.5293dupA variants. RESULTS: The frequency of the FANCM c.5791C>T mutation was higher among breast cancer cases than in controls (OR 1.94, 95% CI 0.87-4.32, P = 0.11), with a statistically significant association with triple-negative breast cancer (OR 5.14, 95% CI 1.65-16.0, P = 0.005). The combined analysis for c.5101C>T and c.5791C>T carriers confirmed a strong association with breast cancer (OR 1.86, 95% CI 1.32-2.49, P = 0.0002), especially among the triple-negative patients (OR 3.08, 95% CI 1.77-5.35, P = 0.00007). For the other variants, only one additional c.4025_4026delCT carrier and no c.5293dupA carriers were observed. CONCLUSIONS: These results support the role of FANCM as a breast cancer susceptibility gene, particularly for triple-negative breast cancer.

Case-control analysis of truncating mutations in DNA damage response genes connects TEX15 and FANCD2 with hereditary breast cancer susceptibility.

Several known breast cancer susceptibility genes encode proteins involved in DNA damage response (DDR) and are characterized by rare loss-of-function mutations. However, these explain less than half of the familial cases. To identify novel susceptibility factors, 39 rare truncating mutations, identified in 189 Northern Finnish hereditary breast cancer patients in parallel sequencing of 796 DDR genes, were studied for disease association. Mutation screening was performed for Northern Finnish breast cancer cases (n = 578-1565) and controls (n = 337-1228). Mutations showing potential cancer association were analyzed in additional Finnish cohorts. c.7253dupT in TEX15, encoding a DDR factor important in meiosis, associated with hereditary breast cancer (p = 0.018) and likely represents a Northern Finnish founder mutation. A deleterious c.2715 + 1G > A mutation in the Fanconi anemia gene, FANCD2, was over two times more common in the combined Finnish hereditary cohort compared to controls. A deletion (c.640_644del5) in RNF168, causative for recessive RIDDLE syndrome, had high prevalence in majority of the analyzed cohorts, but did not associate with breast cancer. In conclusion, truncating variants in TEX15 and FANCD2 are potential breast cancer risk factors, warranting further investigations in other populations. Furthermore, high frequency of RNF168 c.640_644del5 indicates the need for its testing in Finnish patients with RIDDLE syndrome symptoms.

Patient survival and tumor characteristics associated with CHEK2:p.I157T - findings from the Breast Cancer Association Consortium.

BACKGROUND: P.I157T is a CHEK2 missense mutation associated with a modest increase in breast cancer risk. Previously, another CHEK2 mutation, the protein truncating c.1100delC has been associated with poor prognosis of breast cancer patients. Here, we have investigated patient survival and characteristics of breast tumors of germ line p.I157T carriers. METHODS: We included in the analyses 26,801 European female breast cancer patients from 15 studies participating in the Breast Cancer Association Consortium. We analyzed the association between p.I157T and the clinico-pathological breast cancer characteristics by comparing the p.I157T carrier tumors to non-carrier and c.1100delC carrier tumors. Similarly, we investigated the p.I157T associated risk of early death, breast cancer-associated death, distant metastasis, locoregional relapse and second breast cancer using Cox proportional hazards models. Additionally, we explored the p.I157T-associated genomic gene expression profile using data from breast tumors of 183 Finnish female breast cancer patients (ten p.I157T carriers) (GEO: GSE24450). Differential gene expression analysis was performed using a moderated t test. Functional enrichment was investigated using the DAVID functional annotation tool and gene set enrichment analysis (GSEA). The tumors were classified into molecular subtypes according to the St Gallen 2013 criteria and the PAM50 gene expression signature. RESULTS: P.I157T was not associated with increased risk of early death, breast cancer-associated death or distant metastasis relapse, and there was a significant difference in prognosis associated with the two CHEK2 mutations, p.I157T and c.1100delC. Furthermore, p.I157T was associated with lobular histological type and clinico-pathological markers of good prognosis, such as ER and PR expression, low TP53 expression and low grade. Gene expression analysis suggested luminal A to be the most common subtype for p.I157T carriers and CDH1 (cadherin 1) target genes to be significantly enriched among genes, whose expression differed between p.I157T and non-carrier tumors. CONCLUSIONS: Our analyses suggest that there are fundamental differences in breast tumors of CHEK2:p.I157T and c.1100delC carriers. The poor prognosis associated with c.1100delC cannot be generalized to other CHEK2 mutations.

PALB2, CHEK2 and ATM rare variants and cancer risk: data from COGS.

BACKGROUND: The rarity of mutations in PALB2, CHEK2 and ATM make it difficult to estimate precisely associated cancer risks. Population-based family studies have provided evidence that at least some of these mutations are associated with breast cancer risk as high as those associated with rare BRCA2 mutations. We aimed to estimate the relative risks associated with specific rare variants in PALB2, CHEK2 and ATM via a multicentre case-control study. METHODS: We genotyped 10 rare mutations using the custom iCOGS array: PALB2 c.1592delT, c.2816T>G and c.3113G>A, CHEK2 c.349A>G, c.538C>T, c.715G>A, c.1036C>T, c.1312G>T, and c.1343T>G and ATM c.7271T>G. We assessed associations with breast cancer risk (42 671 cases and 42 164 controls), as well as prostate (22 301 cases and 22 320 controls) and ovarian (14 542 cases and 23 491 controls) cancer risk, for each variant. RESULTS: For European women, strong evidence of association with breast cancer risk was observed for PALB2 c.1592delT OR 3.44 (95% CI 1.39 to 8.52, p=7.1×10-5), PALB2 c.3113G>A OR 4.21 (95% CI 1.84 to 9.60, p=6.9×10-8) and ATM c.7271T>G OR 11.0 (95% CI 1.42 to 85.7, p=0.0012). We also found evidence of association with breast cancer risk for three variants in CHEK2, c.349A>G OR 2.26 (95% CI 1.29 to 3.95), c.1036C>T OR 5.06 (95% CI 1.09 to 23.5) and c.538C>T OR 1.33 (95% CI 1.05 to 1.67) (p≤0.017). Evidence for prostate cancer risk was observed for CHEK2 c.1343T>G OR 3.03 (95% CI 1.53 to 6.03, p=0.0006) for African men and CHEK2 c.1312G>T OR 2.21 (95% CI 1.06 to 4.63, p=0.030) for European men. No evidence of association with ovarian cancer was found for any of these variants. CONCLUSIONS: This report adds to accumulating evidence that at least some variants in these genes are associated with an increased risk of breast cancer that is clinically important.

FANCM c.5101C>T mutation associates with breast cancer survival and treatment outcome.

Breast cancer (BC) is a heterogeneous disease, and different tumor characteristics and genetic variation may affect the clinical outcome. The FANCM c.5101C > T nonsense mutation in the Finnish population associates with increased risk of breast cancer, especially for triple-negative breast cancer patients. To investigate the association of the mutation with disease prognosis, we studied tumor phenotype, treatment outcome, and patient survival in 3,933 invasive breast cancer patients, including 101 FANCM c.5101C > T mutation carriers and 3,832 non-carriers. We also examined association of the mutation with nuclear immunohistochemical staining of DNA repair markers in 1,240 breast tumors. The FANCM c.5101C > T mutation associated with poor 10-year breast cancer-specific survival (hazard ratio (HR)=1.66, 95% confidence interval (CI) 1.09-2.52, p = 0.018), with a more pronounced survival effect among familial cases (HR = 2.93, 95% CI 1.5-5.76, p = 1.80 × 10-3 ). Poor disease outcome of the carriers was also found among the estrogen receptor (ER) positive subgroup of patients (HR = 1.8, 95% CI 1.09-2.98, p = 0.021). Reduced survival was seen especially among patients who had not received radiotherapy (HR = 3.43, 95% CI 1.6-7.34, p = 1.50 × 10-3 ) but not among radiotherapy treated patients (HR = 1.35, 95% CI 0.82-2.23, p = 0.237). Significant interaction was found between the mutation and radiotherapy (p = 0.040). Immunohistochemical analyses show that c.5101C > T carriers have reduced PAR-activity. Our results suggest that FANCM c.5101C > T nonsense mutation carriers have a reduced breast cancer survival but postoperative radiotherapy may diminish this survival disadvantage.

RAD51B in Familial Breast Cancer.

Common variation on 14q24.1, close to RAD51B, has been associated with breast cancer: rs999737 and rs2588809 with the risk of female breast cancer and rs1314913 with the risk of male breast cancer. The aim of this study was to investigate the role of RAD51B variants in breast cancer predisposition, particularly in the context of familial breast cancer in Finland. We sequenced the coding region of RAD51B in 168 Finnish breast cancer patients from the Helsinki region for identification of possible recurrent founder mutations. In addition, we studied the known rs999737, rs2588809, and rs1314913 SNPs and RAD51B haplotypes in 44,791 breast cancer cases and 43,583 controls from 40 studies participating in the Breast Cancer Association Consortium (BCAC) that were genotyped on a custom chip (iCOGS). We identified one putatively pathogenic missense mutation c.541C>T among the Finnish cancer patients and subsequently genotyped the mutation in additional breast cancer cases (n = 5259) and population controls (n = 3586) from Finland and Belarus. No significant association with breast cancer risk was seen in the meta-analysis of the Finnish datasets or in the large BCAC dataset. The association with previously identified risk variants rs999737, rs2588809, and rs1314913 was replicated among all breast cancer cases and also among familial cases in the BCAC dataset. The most significant association was observed for the haplotype carrying the risk-alleles of all the three SNPs both among all cases (odds ratio (OR): 1.15, 95% confidence interval (CI): 1.11-1.19, P = 8.88 x 10-16) and among familial cases (OR: 1.24, 95% CI: 1.16-1.32, P = 6.19 x 10-11), compared to the haplotype with the respective protective alleles. Our results suggest that loss-of-function mutations in RAD51B are rare, but common variation at the RAD51B region is significantly associated with familial breast cancer risk.