Prophylactic window therapy with the clinical poly(ADP‐ribose) polymerase inhibitor olaparib delays BRCA1‐deficient mammary tumour formation in mice

Women with heterozygous germline mutations in the BRCA1 tumour suppressor gene are strongly predisposed to developing early‐onset breast cancer through loss of the remaining wild‐type BRCA1 allele and inactivation of TP53. Although tumour prevention strategies in BRCA1‐mutation carriers are still limited to prophylactic surgery, several therapeutic strategies have been developed to target the DNA repair defects (also known as ‘BRCAness’) of BRCA1‐deficient tumours. In particular, DNA‐damaging agents such as platinum drugs and poly(ADP‐ribose) polymerase (PARP) inhibitors show strong activity against BRCA1‐mutated tumours. However, it is unclear whether drugs that target BRCAness can also be used to prevent tumour formation in BRCA1‐mutation carriers, especially as loss of wild‐type BRCA1 may not be the first event in BRCA1‐associated tumourigenesis. We performed prophylactic treatments in a genetically engineered mouse model in which de novo development of BRCA1‐deficient mammary tumours is induced by stochastic loss of BRCA1 and p53. We found that prophylactic window therapy with nimustine, cisplatin or olaparib reduced the amount and size of mammary gland lesions, and significantly increased the median tumour latency. Similar results were obtained with intermittent prophylactic treatment with olaparib. Importantly, prophylactic window therapy with nimustine and cisplatin resulted in an increased fraction of BRCA1‐proficient mammary tumours, suggesting selective survival and malignant transformation of BRCA1‐proficient lesions upon prophylactic treatment with DNA‐damaging agents. Prophylactic therapy with olaparib significantly prolonged mammary tumour‐free survival without any significant increase in the fraction of BRCA1‐proficient tumours, warranting the evaluation of this PARP inhibitor in prophylactic trials in BRCA1‐mutation carriers. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

A tissue reconstitution model to study cancer cell‐intrinsic and ‐extrinsic factors in mammary tumourigenesis

The contribution of cancer cell‐intrinsic and ‐extrinsic factors to metastatic breast cancer is still poorly understood, hampering development of novel therapeutic strategies that decrease breast cancer mortality. Cre/loxP‐based conditional mouse models of breast cancer present unique opportunities to study sporadic tumour formation and progression in a controlled setting. Unfortunately, the generation of mouse strains carrying multiple mutant alleles needed for such studies is very time‐consuming. Moreover, conditional mouse tumour models do not permit independent manipulation of tumour cell‐intrinsic and ‐extrinsic factors. Although the latter can be achieved by cleared fat‐pad transplantation of mouse mammary epithelial cells (MMECs) from tumour suppressor gene (TSG) knockouts into wild‐type or mutant recipients, this procedure is not possible for mutations that cause embryonic lethality or preclude mammary gland development. Here we show that cleared fat‐pad transplantations with MMECs isolated from K14cre;Cdh1^F/F; Trp53^F/F mice expressing Cre recombinase under control of the cytokeratin‐14 promoter and carrying conditional null alleles for p53 and E‐cadherin (Cdh1) first resulted in the formation of phenotypically normal mammary glands, followed by the development of invasive metastatic mammary tumours. Tumour formation in the recipients mimicked tumour latency, spectrum, morphology, immunophenotype, and metastatic characteristics of the original mammary tumour model. This transplantation system, which can be expanded to other conditional TSG knockouts, permits independent genetic analysis of stromal factors and testing of additional cancer cell‐intrinsic mutations that would otherwise be embryonic lethal or require intensive breeding. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

A mouse model of basal-like breast carcinoma with metaplastic elements

Breast cancers arising in carriers of germline BRCA1 mutations frequently have a basal-like phenotype. Basal-like cancers are characterized by high histological grade, central necrotic areas, foci with metaplastic differentiation, lack of hormone receptor and HER2 (ErbB2) expression, and consistent positivity for basal markers, including CK5/6, CK14, and EGFR. We have used germline manipulation to generate a conditional mouse model of Brca1 deficiency. Transgenic expression of Cre recombinase in the mammary gland of these mice results in deletion of exons encoding the C-terminus of Brca1 and leads to tumour formation when combined with heterozygosity for a p53 mutation. Histologically, these mammary gland tumours were characterized by high histological grade, central necrotic areas, and presence of homologous metaplastic elements. These metaplastic elements consisted of neoplastic spindle cells or squamous cell differentiation in the form of keratin pearls or individual cell keratinization. Immunohistochemical analysis revealed expression of basal-like markers in all cases. The tumour phenotype generated in our mouse model was compared with published data on human basal-like breast carcinomas and also with metaplastic breast cancers with a basal-like phenotype; the comparison showed that we have generated a mouse model of basal-like breast cancer, which should prove useful in testing new and targeted treatments for this type of breast cancer.     

Loss of Rad51c accelerates tumourigenesis in sebaceous glands of Trp53‐mutant mice

Germline mutations in RAD51C predispose to breast and ovarian cancers. However, the mechanism of RAD51C‐mediated carcinogenesis is poorly understood. We previously reported a first‐generation Rad51c‐knock‐out mouse model, in which a spontaneous loss of both Rad51c and Trp53 together resulted in a high incidence of sebaceous carcinomas, particularly in preputial glands. Here we describe a second‐generation mouse model, in which Rad51c is deleted, alone or together with Trp53, in sebaceous glands, using Cre‐mediated recombination. We demonstrate that deletion of Rad51c alone is not sufficient to drive tumourigenesis and may only cause keratinization of preputial sebocytes. However, deletion of Rad51c together with Trp53 leads to tumour development at around 6 months of age, compared to 11 months for single Trp53‐mutant mice. Preputial glands of double‐mutant mice are also characterized by increased levels of cell proliferation and DNA damage and form multiple hyperplasias, detectable as early as 2 months of age. Our results reveal a critical synergy between Rad51c and Trp53 in tumour progression and provide a predictable in vivo model system for studying mechanisms of Rad51c‐mediated carcinogenesis. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Genomic signature of BRCA1 deficiency in sporadic basal‐like breast tumors

About 10–20% of all breast carcinomas show a basal‐like phenotype, while ～ 90% of breast tumors from BRCA1‐mutation carriers are of this subtype. There is growing evidence that BRCA1‐mutated tumors are not just a specific subset of the basal‐like tumors, but that (the majority of) basal‐like tumors show a dysfunctional BRCA1 pathway. This has major treatment implications, because emerging regimens specifically targeting DNA repair mechanisms would then be most effective against these tumors. To further understand the involvement of BRCA1 deficiency in sporadic basal‐like tumors, we investigated 41 basal‐like tumors for BRCA1 mRNA expression by quantitative real‐time polymerase chain reaction, BRCA1 promoter methylation, their genomic profile by array‐CGH, and gene expression levels by whole genome expression arrays. Array‐CGH results were compared to those of 34 proven BRCA1‐mutated tumors. Basal‐like tumors were subdivided into two equal groups: deficient and proficient in BRCA1 gene expression. The chromosomal makeup of BRCA1 deficient sporadic basal‐like tumors was similar to that of BRCA1‐mutated tumors. BRCA1 proficient sporadic basal‐like tumors were more similar to nonbasal‐like tumors. Only half of the basal‐like breast tumors are actually deficient in BRCA1 expression. Gain of chromosome arm 3q is a marker for BRCA1 deficiency in hereditary and sporadic breast tumors. © 2010 Wiley‐Liss, Inc.     

Androgen receptor expression in breast cancer patients tested for BRCA1 and BRCA2 mutations

Pristauz G, Petru E, Stacher E, Geigl J B, Schwarzbraun T, Tsybrovskyy O, Winter R & Moinfar F
(2010) Histopathology 57, 877–884 Androgen receptor expression in breast cancer patients tested for BRCA1 and BRCA2 mutations Aim: To assess the expression of receptors for androgen (AR), oestrogen (ER) and progesterone (PR) as well as human epidermal growth factor receptor type 2 (Her‐2/neu) status of breast carcinomas in breast cancer susceptibility gene (BRCA) BRCA1/2 mutation carriers and BRCA1/2 negative tested women. Methods: One hundred and thirty‐five breast cancers in women tested for BRCA1/2 mutations. Screening for BRCA1 and BRCA2 mutations was performed by direct sequencing of all BRCA1 and BRCA2 exons as well as the surrounding intronic sequences. Additionally, BRCA genes were analysed with multiplex ligation‐dependent probe amplification. Consecutive paraffin sections were examined immunhistochemically for AR, ER, PR and Her‐2/neu. Results: Of the 135 tumours, 43 (32%) were BRCA1‐related, 18 (13%) were BRCA2‐related and 74 (55%) were BRCA1/2‐negative. Seventy‐two per cent of the BRCA1‐related, 22% of the BRCA2‐related and 12% of the BRCA1/2‐negative tumours were triple (ER, PR, Her2neu)‐negative. Eighty‐four per cent of BRCA1 mutated cancers were high‐grade (G3) tumours. ARs were expressed in 30% (13 of 43) of BRCA1‐related, in 78% (14 of 18) in BRCA2‐related tumours and in 76% (56 of 74) in BRCA1/2 negative tumours. Twenty‐one per cent of ER‐negative BRCA1‐related tumours expressed androgen receptors. Conclusion: Approximately one in five BRCA1 mutated breast cancers negative for ER and PR express androgen receptors. Modulation of AR might open a new avenue for treating these high‐risk cancers.     

Tumor formation in Brca1 conditional mutant mice

BRCA1 is the first breast cancer-associated gene, whose mutation predisposes women to breast and ovarian cancers. Targeted mutations of Brca1 in the mouse result in embryonic lethality primarily attributed to cellular proliferation defects, raising questions about the mechanisms by which Brca1 represses tumor formation. To overcome the early lethality, we engineered Brca1 by flanking its exon 11 with loxP sites. We showed that deletion of the exon by EIIA-Cre, which expresses Cre in the germline, causes p53-dependent lethality at late gestation. On the other hand, MMTV-Cre, which expresses Cre in mammary epithelium, resulted in tumorigenesis at low frequency after a long latency, accompanied by increased epithelial cell apoptosis and abnormal ductal development. Mammary tumor formation was significantly accelerated in a p53(+/-) genetic background; however, it still appeared in a stochastic fashion, suggesting the involvement of additional factors. Notably, the tumors were highly diverse in histopathology and displayed extensive genetic/molecular alterations, including overexpression of ErbB2, c-Myc, p27, and Cyclin D1, and downregulation of p16 in the majority of tumors. This observation suggests roles for these proteins in Brca1-associated tumorigenesis.     

βhCG mediates immune suppression through upregulation of CD11b+Gr1+ myeloid derived suppressor cells,CD206+ M2 macrophages,and CD4+FOXP3+ regulatory T-cells in BRCA1 deficient breast cancers

BRCA1 mutation is reported in about 70% of all triple negative breast cancers (TNBC), while BRCA1 defect due to promoter hypermethylation is seen in about 30%–60% of sporadic breast cancers. Although PARP inhibitors and platinum-based chemotherapy are used to treat these cancers, more efficient therapeutic approaches are required to overcome the resistance to treatment. Our previous findings have reported elevated βhCG expression but not αhCG in BRCA1 deficient breast cancers. As βhCG causes immune suppression in pregnancy, this study explored the immunomodulatory effect of βhCG in BRCA1mutated/deficient TNBC. We observed that Th1, Th2, and Th17 cytokines are upregulated in the presence of βhCG in BRCA1 defective cancers. In NOD-SCID and syngeneic mouse models, βhCG increases the frequency of Myeloid-derived suppressor cells in tumour tissues and contributes to macrophage reprogramming from antitumor M1 to pro-tumour M2 phenotype. βhCG reduces the CD4⁺T-cell infiltration while increasing the density of CD4⁺CD25⁺FOXP3⁺regulatory T-cell in BRCA1 deficient tumour tissues. In contrast, xenograft tumours with βhCG knocked down TNBC cells did not show these immune suppressive effects. We have also shown that βhCG upregulates pro-tumorigenic markers arginase1(Arg1), inducible nitric oxide synthase, PD-L1/PD-1, and NFκB in BRCA1 defective tumours. Thus, for the first time, this study proves that βhCG suppresses the host antitumor immune response and contributes to tumour progression in BRCA1 deficient tumours. This study will help develop new immunotherapeutic approaches for treating BRCA1 defective TNBC by regulating βhCG.     

High incidence of mammary intraepithelial neoplasia development in Men1‐disrupted murine mammary glands

Mutations of the MEN1 tumour suppressor gene predispose patients to the development of multiple endocrine neoplasia type 1 (MEN1) syndrome, which is characterized by multiple endocrine tumours, including prolactinomas. The recent findings of the interaction between menin, encoded by the MEN1 gene, and the oestrogen receptor, as well as the observation of rare cases of mammary carcinomas in our heterozygous Men1 mutant mice, led us to investigate a putative tumour suppressor function of the Men1 gene in mouse mammary cells by disrupting the gene in luminal epithelial cells. A significantly higher incidence of mammary intraepithelial neoplasia (MIN) was observed in mutant WapCre‐Men1^F/F mice (51.5%) than in WapCre‐Men1^+/+ (0%) or Men1^F/F (7.1%) control mice. The majority of MIN observed in the mutant mice displayed complete menin inactivation. Because of the leakage of WapCre transgene expression, prolactinomas were observed in 83.3% of mutant mice, leading to premature death. As there was no correlation between MIN development and elevated serum prolactin levels, and phospho‐STAT5 expression was decreased in mammary lesions, the increased incidence of MIN lesions was most likely due to Men1 disruption rather than to prolactinoma development. Interestingly, in MIN lesions, we found a decrease in membrane‐associated E‐cadherin and beta‐catenin expression, the latter of which is a menin partner. Finally, reduced menin expression was found in a large proportion of two independent cohorts of patients with breast carcinomas. Taken together, the current work indicates a role of Men1 inactivation in the development of mammary pre‐cancerous lesions in mice and a potential role in human mammary cancer.     

Identification of cellular and genetic drivers of breast cancer heterogeneity in genetically engineered mouse tumour models

The heterogeneous nature of mammary tumours may arise from different initiating genetic lesions occurring in distinct cells of origin. Here, we generated mice in which Brca2, Pten and p53 were depleted in either basal mammary epithelial cells or luminal oestrogen receptor (ER)‐negative cells. Basal cell‐origin tumours displayed similar histological phenotypes, regardless of the depleted gene. In contrast, luminal ER‐negative cells gave rise to diverse phenotypes, depending on the initiating lesions, including both ER‐negative and, strikingly, ER‐positive invasive ductal carcinomas. Molecular profiling demonstrated that luminal ER‐negative cell‐origin tumours resembled a range of the molecular subtypes of human breast cancer, including basal‐like, luminal B and ‘normal‐like’. Furthermore, a subset of these tumours resembled the ‘claudin‐low’ tumour subtype. These findings demonstrate that not only do mammary tumour phenotypes depend on the interactions between cell of origin and driver genetic aberrations, but also multiple mammary tumour subtypes, including both ER‐positive and ‐negative disease, can originate from a single epithelial cell type. This is a fundamental advance in our understanding of tumour aetiology. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Cdkn2a suppresses metastasis in squamous cell carcinomas induced by the gain‐of‐function mutant p53R172H

p53 (TP53) is the most frequently mutated gene in squamous cell carcinomas (SCCs) of the skin and head and neck. Certain p53 mutations are oncogenic and promote invasion and metastasis in SCCs. However, it is unclear how the oncogenic function of mutant p53 is modulated by other molecular alterations that co‐exist in SCCs. Here, we show that deletion of the p53 gene and activation of an endogenous p53^R172H gain‐of‐function mutation in the skin induce carcinomas with similar kinetics and penetrance. Deletion of p53 induced primarily well‐differentiated SCCs. However, most of the tumours induced by p53^R172H were poorly differentiated SCCs, the only metastatic tumours in this model. These tumours expressed higher levels of cyclin D1 than the well‐differentiated SCCs and spindle carcinomas that developed in these mice. Unexpectedly, metastasis was not observed in mice that developed spindle carcinomas, which expressed high levels of the tumour suppressors p16^Ink4a and p19^Arf, encoded by Cdkn2a, a gene frequently deleted in human SCCs. Remarkably, deletion of the Cdkn2a gene in p53^R172H‐induced SCCs promoted a dramatic increase in metastasis rates and a shorter survival in mice that developed these tumours, compared with those observed in mice with tumours in which Cdkn2a was deleted in the presence of a p53 loss‐of‐function mutation or wild‐type p53. Accordingly, the survival of patients with head and neck SCCs bearing co‐occurring high‐risk p53 mutations and CDKN2A homozygous deletions was much shorter than that of patients with tumours in which high‐risk p53 mutations did not contain CDKN2A homozygous deletions, or that of patients with tumours in which homozygous CDKN2A deletions co‐existed with either low‐risk p53 mutations or potential loss‐of‐function mutations in p53. These findings genetically identify a population of SCC patients with worst outcomes and will help to predict outcomes according to the p53 status and alterations in CDKN2A. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Molecular analysis of PALB2‐associated breast cancers

PALB2 is established as the most clinically important moderate to high penetrance breast cancer predisposition gene after BRCA1 and BRCA2. Mutations in classical familial cancer predisposition genes are presumed to be recessive at the cellular level and therefore a second inactivating somatic mutation is required in the tumour tissue. However, from the limited data that exist, PALB2 may be an example of a cancer predisposition gene that does not conform to Knudson's ‘two hit’ paradigm. We conducted genome‐wide copy number analysis and targeted sequencing of PALB2 and other breast cancer driver genes in 15 invasive breast cancers from individuals carrying pathogenic germline mutations in PALB2. The majority of cancers showed clear evidence of bi‐allelic inactivation of PALB2 (10/15) either as loss of heterozygosity involving the wild‐type allele (six tumours) or as somatic point mutations (four tumours). All PALB2‐null cancers had high homologous recombination deficiency (HRD) scores consistent with a homologous recombination repair deficiency. Interestingly, all but one of the PALB2 heterozygous cancers also had high HRD scores, suggesting that alternative mechanisms of PALB2 functional loss might be operating in these cancers. Our findings demonstrate that PALB2 does undergo bi‐allelic inactivation in the majority of breast cancers from PALB2 germline mutation carriers. This feature has implications for the discovery of new moderate to high penetrance breast cancer predisposition genes as it supports using the existence of a ‘second hit’ and mutation signatures as important search criteria. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Cloning, chromosomal mapping and expression pattern of the mouse Brca2 gene

A proportion of human breast cancers result from an inherited predisposition to the disease. Mutations in the BRCA2 gene confer a high risk of breast cancer and are responsible for almost half of these cases. The recent cloning of the human BRCA2 gene has revealed that it encodes a large protein having little significant homology to known proteins. Here we describe the mouse Brca2 gene. The gene maps to mouse chromosome 5, consistent with its location on human chromosome 13q12. We have sequenced cDNA for the entire 3329 amino acid Brca2 protein and this has revealed that, like Brca1, Brca2 is relatively poorly conserved between humans and mice. Brca2 is transcribed in a diverse range of mouse tissues, and the pattern of expression is strikingly similar to that of Brca1. Taken together, our data highlight some intriguing similarities between two genes involved in inherited breast cancer susceptibility.      

Notch pathway regulation of neural crest cell development in vivo

Background : The function of Notch signaling in murine neural crest–derived cell lineages in vivo was examined. Results : Conditional gain (Wnt1Cre;Rosa^Notch) or loss (Wnt1Cre;RBP‐J^f/f) of Notch signaling in neural crest cells (NCCs) in vivo results in craniofacial, cardiac, and trunk abnormalities. Severe craniofacial malformations are apparent in Wnt1Cre;Rosa^Notch embryos, while less severe skull abnormalities are evident in Wnt1Cre;RBP‐J^f/f mice. Deficient cardiac neural crest migration, resulting in cardiac outflow tract malformations, occurs with increased or decreased Notch signaling in NCCs. Smooth muscle cell differentiation also is impaired in pharyngeal NCC derivatives in both Wnt1Cre;Rosa^Notch and Wnt1Cre;RBP‐J^f/f embryos. Neurogenesis is absent and gliogenesis is increased in the dorsal root ganglia of Wnt1Cre;Rosa^Notch embryos, while neurogenesis is increased and gliogenesis is decreased in Wnt1Cre;RBP‐J^f/f embryos. Conclusions : Together, these studies demonstrate essential cell‐autonomous roles for appropriate levels of Notch signaling during NCC migration, proliferation, and differentiation with critical implications in craniofacial, cardiac, and neurogenic development and disease. Developmental Dynamics 241:376–389, 2012. © 2011 Wiley Periodicals, Inc.     

Oestrogen‐mediated phosphorylation and stabilization of BRCA2 protein in breast

Disease‐associated BRCA2 mutations typically result in protein truncations that delete the phosphorylation‐regulated S3291 BRCA2 domain that interacts with Rad51. BRCA2 hereditary breast cancers are usually ER⁺, differing from BRCA1 hereditary cancers, which are usually ER^?. We studied BRCA2 protein expression and S3291 phosphorylation in normal breast tissues and in sporadic breast cancers and observed that BRCA2 is expressed and phosphorylated in normal breast and 10 ER⁺ breast cancers but not in 10 ER^? breast cancers. In order to study this correlation between ER and BRCA2 expression, we studied ER⁺ breast cancer cell lines. We found that a rapid increase in BRCA2 S3291 phosphorylation occurs following 17‐β‐oestradiol (E2) treatment. This increase seen in BRCA2 total and phospho‐S3291 protein levels was found to be unaffected with cycloheximide pre‐treatment, but decreased following tamoxifen, ICI 182,780 or roscovitine treatment. This suggests a requirement for ER and cdk (cyclin‐dependent kinase) in mediating the increased protein levels. MCF7 cell cycle distribution analysis following E2, in both the presence and absence of roscovitine (a cdk inhibitor), did not demonstrate any changes during an 8 h period, which further supports our hypothesis that mitogenic effects of E2 are not predominant at early time points. Studies with MG132 proteasome inhibitor and siRNA to skp2 support a model in which skp2‐mediated proteasomal degradation of BRCA2 rapidly degrades BRCA2 protein in the absence of hormone treatment, which likely inhibits this pathway. E2 was shown to improve survival of MCF7 cells upon radiation treatment and roscovitine partially reversed this effect. We have demonstrated that BRCA2 protein is specifically expressed in ER⁺ breast cancers and are investigating a pathway that may show a link between E2 action and BRCA2 protein function in breast cancer. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

BRCA1 Germ‐Line Mutations and Tumor Characteristics in Eastern Chinese Women with Familial Breast Cancer

Although several studies detected the BRCA1 germ‐line mutations in Chinese women with familial breast cancer, most of them did not employ conventional full gene sequencing, especially in eastern China. In addition, the clinicopathological features of BRCA1‐associated breast cancer in Chinese women were not well investigated. In this study, we screened the complete coding regions and exon‐intron boundaries of BRCA1 by polymerase chain reaction (PCR)‐sequencing assay. Immunohistochemistry analyses were performed on tumor samples to detect the expression of estrogen receptor (ER), progesterone receptor (PR), P53, and human epidermal growth factor receptor‐2 (HER‐2). Breast cancer patients having one or more affected relatives referred from the Zhejiang Cancer Hospital, eastern China during 2008–2011 were selected for the study. A total of 62 familial breast cancer patients received the BRCA1 germ‐line mutation screening. Five deleterious mutations were detected in this cohort. The mutation rate was 11.3% (7/62). We found two novel mutations (3414delC and 5,280 C > T) and two recurrent mutations (5,273 G > A and 5589del8). BRCA1 mutation tumors tended to be negative for ER, PR, and HER‐2, and exhibited high histological grade compared with tumors without BRCA1 mutations. Our study suggests that recurrent mutations may exist in eastern Chinese women with familial breast cancer and PCR‐sequencing assay is a useful tool to screen these mutations. It also suggests that BRCA1‐associated breast cancers in Chinese women exhibit an aggressive phenotype. Anat Rec, 2013. © 2012 Wiley Periodicals, Inc.     

Frequent IDH2 R172 mutations in undifferentiated and poorly‐differentiated sinonasal carcinomas

Sinonasal undifferentiated carcinoma (SNUC) is a high‐grade malignancy with limited treatment options and poor outcome. A morphological spectrum of 47 sinonasal tumours including 17 (36.2%) SNUCs was analysed at genomic level. Thirty carcinomas (cohort 1) were subjected to a hybridization exon‐capture next‐generation sequencing assay (MSK‐IMPACT^TM) to interrogate somatic variants in 279 or 410 cancer‐related genes. Seventeen sinonasal tumours (cohort 2) were examined only for the presence of IDH1/2 exon 4 mutations by Sanger sequencing. IDH2 R172 single nucleotide variants were overall detected in 14 (82.4%) SNUCs, in two (20%) poorly‐differentiated carcinomas with glandular/acinar differentiation, and in one of two high‐grade neuroendocrine carcinomas, large cell type (HGNECs). No IDH2 mutation was detected in any of five olfactory neuroblastomas or in any of five SMARCB1‐deficient carcinomas. Among 12 IDH2‐mutated cases in cohort 1, five (41.7%) harboured co‐existing TP53 mutations, four (33.3%) CDKN2A/2B loss‐of‐function alterations, four (33.3%) MYC amplification, and three (25%) had concurrent SETD2 mutations. AKT1 E17K and KIT D816V hotspot variants were each detected in one IDH2‐mutated SNUC. The vast majority of SNUCs and variable proportions of other poorly‐differentiated sinonasal carcinomas may be amenable to IDH2‐targeted therapy. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Frequent incidence of BARD1‐truncating mutations in germline DNA from triple‐negative breast cancer patients

Triple‐negative breast cancer (TNBC) accounts for 10–20% of all breast cancers (BCs), and conventional chemotherapy is the only effective systemic treatment. Germline BRCA1/2 mutations are found in approximately 15% of TNBC patients. In the past, we have documented pathogenic mutations in BARD1, a BRCA1 interacting protein, in families at high risk for BC. In this study, we have analyzed germline DNA from 61 estrogen receptor negative patients (of which 42 were TNBC) for the presence of mutations in the BRCA1, BRCA2 and BARD1 gene. BRCA1/2 mutations were found in 8 out of 42 (19%) TNBC patients, but not in the ER?/HER2+ cohort. We also found four good candidate pathogenic BARD1 mutations in the TNBC cohort, including two protein‐truncating mutations (p.Gln564Ter and p.Arg641Ter). Our data suggest that TNBC patients are enriched for pathogenic BARD1 germline mutations as compared to control samples and high BC risk families. Ten of the 42 investigated TNBC patients carry a BRCA pathway mutation (in BRCA1, BRCA2 or BARD1) rendering them susceptible to homologous recombination deficiency. These patients should become eligible for exploring the efficacy of poly (ADP‐ribose) polymerase (PARP) inhibitors.