Somatic mutations in the BRCA2 gene and high frequency of allelic loss of BRCA2 in sporadic male breast cancer

The cancer genetics and pathology of male breast cancer

Male breast cancer (MBC) is an uncommon and poorly understood disease. Recent molecular studies have shown important differences from female breast cancer which are likely to influence treatment strategies from the current female-based management towards a more tailored approach. Significantly more MBCs than female breast cancers arise with an underlying germline cancer predisposition, and display a vastly different penetrance compared with females. Furthermore, the genophenotypical association of basal-like cancer with BRCA1 present in female breast cancer is not observed in male breast cancer. Differences in somatic changes between male and female breast cancer have also been reported, with particular enrichment of PIK3CA mutations and a paucity of TP53 mutations. In general, chromosomal-based changes, in particular regions of gains, are seen more frequently in male than female breast cancer and methylation is seen less frequently. Clinically, several molecular subtypes with prognostic relevance have been described, including chromosomal complex high and methylation high groups, and subgroups with profiling signatures pertaining to epithelial mesenchymal transition and hormonal therapy insensitivity. As with female breast cancer, attention to male specific multicentre trials based on the individual characteristics are needed, together with establishment of reliable preclinical models to understand more clearly the pathogenesis of male breast cancer and improve the general poor outcome of this disease.

EMSY copy number variation in male breast cancers characterized for BRCA1 and BRCA2 mutations

PURPOSE

Male breast cancer (MBC) is a rare disease that shares some similarities with female breast cancer (FBC). Like FBC, genetic susceptibility to MBC can be referred to mutations in BRCA1 and, particularly, BRCA2 genes. However, only about 10 % of MBCs are caused by BRCA1/2 germ-line mutations, while the largest part are sporadic cancers and may derive from somatic alterations. EMSY, a BRCA2 inactivating gene, emerged as a candidate gene involved in the pathogenesis of sporadic FBC, and its amplification was suggested to be the somatic counterpart of BRCA2 mutations. Considering the relevant role of BRCA2 in MBC, we aimed at investigating the role of EMSY gene copy number variations in male breast tumors.

METHODS

EMSY copy number variations were analyzed by quantitative real-time PCR with TaqMan probes in a selected series of 75 MBCs, characterized for BRCA1/2 mutations.

RESULTS

We reported EMSY amplification in 34.7 % of MBCs. A significant association emerged between EMSY amplification and BRCA1/2 mutations (p = 0.03). We identified two amplification subgroups characterized by low and high amplification levels, with BRCA2-related tumors mostly showing low EMSY amplification.

CONCLUSIONS

Our results show a high frequency of EMSY amplification in MBC, thus pointing to a role of EMSY in the pathogenesis of this disease. EMSY amplification may be a new feature that might uncover underlying molecular pathways of MBCs and may allow for the identification of MBC subgroups with potential clinical implication for targeted therapeutic approaches.

Spectrum and frequencies of BRCA1/2 mutations in Bulgarian high risk breast cancer patients

BACKGROUND

About 3885 women are diagnosed with breast cancer and 1285 die from the disease each year in Bulgaria. However no genetic testing to identify the mutations in high-risk families has been provided so far.

METHODS

We evaluated 200 Bulgarian women with primary invasive breast cancer and with personal/ family history of breast cancer for the presence of unequivocally damaging germline mutations in BRCA1/2 using Sanger sequencing.

RESULTS

Of the 200 patients, 39 (19.5 %) carried a disease predisposing mutation, including 28 (14 %) with a BRCA1 mutation and 11 (5.5 %) with a BRCA2 mutation. At BRCA1, 6 different mutations were identified, including 2 frameshifts, 1 nonsense and 1 missense that had been previously reported (c.5030_5033delCTAA, c.5263_5264insC, c.4603G > T, c.181 T > G), and 2 frameshifts, which were novel to this study (c.464delA, c.5397_5403delCCCTTGG). At BRCA2, 7 different frameshift mutations were identified, including 5 previously reported (5851_5854delAGTT, c.5946delT, c.5718_5719delCT, c.7910_7914delCCTTT,c.9098_9099insA) and 2 novel (c.8532_8533delAA, c.9682delA). A BRCA1 mutation was found in 18.4 % of women diagnosed with breast cancer at/or under the age of 40 compared to 11.2 % of women diagnosed at a later age; a BRCA2 mutation was found in 4 % of women diagnosed at/or under the age of 40 compared to 6.5 % of women diagnosed at a later age. A mutation was present in 26.8 % patients with a positive family history and in 14.4 % of women with a negative family history. The most prevalent mutation observed in 22 patients (11 %) was BRCA1 c.5263_5264insC, a known Slavic mutation with founder effect in Eastern European and AJ communities. Other recurrent mutations were BRCA2 c.9098-9099insA (2 %), BRCA1 c.181T > G (1 %) and BRCA2 c.5851_5854delAGTT (1 %). Notably, BRCA1 c.5263_5264insC represented 56 % of all mutations identified in this series. Of the 22 patients with BRCA1 c.5263_5264insC, 9 were diagnosed with early onset breast cancer, 11 with TNBCs, 4 with bilateral breast cancer, and 6 with both breast and ovarian cancer.

CONCLUSIONS

This is the first comprehensive study of the BRCA1/2 mutation spectrum in Bulgaria and will assist the establishment of efficient protocols for genetic testing and individualized risk assessment for Bulgarian breast/ovarian cancer patients and healthy individuals at a high-risk.

Mutational profiling of familial male breast cancers reveals similarities with luminal A female breast cancer with rare TP53 mutations

Background:

Male breast cancer (MBC) is still poorly understood with a large proportion arising in families with a history of breast cancer. Genomic studies have focused on germline determinants of MBC risk, with minimal knowledge of somatic changes in these cancers.

Methods:

Using a TruSeq amplicon cancer panel, this study evaluated 48 familial MBCs (3 BRCA1 germline mutant, 17 BRCA2 germline mutant and 28 BRCAX) for hotspot somatic mutations and copy number changes in 48 common cancer genes.

Results:

Twelve missense mutations included nine PIK3CA mutations (seven in BRCAX patients), two TP53 mutations (both in BRCA2 patients) and one PTEN mutation. Common gains were seen in GNAS (34.1%) and losses were seen in GNAQ (36.4%), ABL1 (47.7%) and ATM (34.1%). Gains of HRAS (37.5% vs 3%, P=0.006), STK11 (25.0% vs 0%, P=0.01) and SMARCB1 (18.8% vs 0%, P=0.04) and the loss of RB1 (43.8% vs 13%, P=0.03) were specific to BRCA2 tumours.

Conclusions:

This study is the first to perform high-throughput somatic sequencing on familial MBCs. Overall, PIK3CA mutations are most commonly seen, with fewer TP53 and PTEN mutations, similar to the profile seen in luminal A female breast cancers. Differences in mutation profiles and patterns of gene gains/losses are seen between BRCA2 (associated with TP53/PTEN mutations, loss of RB1 and gain of HRAS, STK11 and SMARCB1) and BRCAX (associated with PIK3CA mutations) tumours, suggesting that BRCA2 and BRCAX MBCs may be distinct and arise from different tumour pathways. This has implications on potential therapies, depending on the BRCA status of MBC patients.

Male breast cancer: risk factors, biology, diagnosis, treatment, and survivorship

BACKGROUND

The causes, optimal treatments, and medical/psychosocial sequelae of breast cancer in men are poorly understood.

DESIGN

A systematic review of the English language literature was conducted to identify studies relevant to male breast cancer between 1987 and 2012 and including at least 20 patients. Searches were carried out on PubMed using the title terms 'male breast cancer' or 'male breast carcinoma'.

RESULTS

Relevant published data regarding risk factors, biological characteristics, presentation and prognosis, appropriate evaluation and treatment, and survivorship issues in male breast cancer patients are presented. BRCA2 mutations, age, conditions that alter the estrogen/androgen ratio, and radiation are proven risk factors. Disease biology is distinct in men, but diagnostic approaches and treatments for men are generally extrapolated from those in women due to inadequate research in men. Survivorship issues in men may include sexual and hormonal side-effects of endocrine therapies as well as unique psychosocial impacts of the disease.

CONCLUSION

Further research is needed to address gaps in knowledge pertaining to care of male breast cancer patients and survivors.

PIK3CA mutations are frequently observed in BRCAX but not BRCA2-associated male breast cancer

INTRODUCTION

Although a substantial proportion of male breast cancers (MBCs) are hereditary, the molecular pathways that are activated are unknown. We therefore examined the frequency and clinicopathological associations of the PIK3CA/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) pathways and their regulatory genes in familial MBC.

METHODS

High resolution melting analysis and confirmatory sequencing was used to determine the presence of somatic mutations in PIK3CA (exon 9 and 20), AKT1 (exon 4), KRAS (exon 2) and BRAF (exon 15) genes in 57 familial MBCs. Further analysis of the PIK3CA/mTOR pathway was performed using immunohistochemistry for the pAKT1, pS6 and p4EBP1 biomarkers.

RESULTS

PIK3CA somatic mutations were identified in 10.5% (6 of 57) of cases; there were no AKT1, KRAS or BRAF somatic mutations. PIK3CA mutations were significantly more frequent in cancers from BRCAX patients (17.2%, 5/29) than BRCA2 (0%, 0/25) carriers (P = 0.030). Two BRCAX patients had an E547K mutation which has only been reported in one female breast cancer previously. PIK3CA mutation was significantly correlated with positive pS6 (83.3% vs. 32.0%, P = 0.024) and negative p4EBP1 (100% vs. 38.0%, P = 0.006) expression, but not pAKT expression. Expression of nuclear p4EBP1 correlated with BRCA2 mutation carrier status (68.0% vs. 38.7%, P = 0.035).

CONCLUSIONS

Somatic PIK3CA mutation is present in familial male breast cancer but absent in BRCA2 carriers. The presence of two of the extremely rare E547K PIK3CA mutations in our cohort may have specific relevance in MBCs. Further study of PIK3CA in MBCs, and in particular BRCAX patients, may contribute to further establishing the relevance of specific PIK3CA mutations in MBC aetiology and in the identification of particular patient groups most likely to benefit from therapeutic targeting with the novel PIK3CA inhibitors that are currently in development.

Fanconi anaemia: from a monogenic disease to sporadic cancer

The dissection of the molecular pathways participating in genetic instability disorders has rendered invaluable information about the mechanisms of cancer pathogenesis and progression, and is offering a unique opportunity to establish targeted anticancer therapies. Fanconi anaemia (FA) is a paradigm of cancer-prone inherited monogenic disorders. Moreover, accumulated evidence indicates that genetic and epigenetic alterations in FA genes can also play an important role in sporadic cancer in the general population. Here, we summarise current progress in the understanding of the molecular biology of FA and review the principal mechanisms accounting for a disrupted FA pathway in sporadic cancer. Additionally, we discuss the impact of these findings in the development of new anticancer therapies, particularly with DNA interstrand crosslinkers and with new inhibitors of the FA and/or alternative DNA repair pathways.

Detecting BRCA2 protein truncation in tissue biopsies to identify breast cancers that arise in BRCA2 gene mutation carriers

PURPOSE

Mutations in the BRCA2 gene are dominantly inherited but cause cancers when the wild-type allele has loss of heterozygosity (LOH) within the cancer. Because most disease-associated BRCA2 mutations are protein-truncating mutations, a test for truncated BRCA2 proteins should identify most BRCA2 hereditary cancers.

METHODS

We have developed a tissue truncation test to identify truncated BRCA2 proteins in breast cancer tissue biopsies in vivo that does not use amplification or genetic manipulations. N-terminal and C-terminal antibodies are used to visualize protein truncation by demonstrating that the beginning of the protein is present but the end (ie, terminus) is absent.

RESULTS

A quantitative C-terminal immunostaining score or a C-terminal to N-terminal truncation ratio correctly classified 20 of 21 breast cancers arising in BRCA2 mutation carriers and 57 of 58 cancers arising outside the context of a multiple-case breast cancer family. This represents a sensitivity of 95% and a specificity of 98%. Because of the presence of C-terminal BRCA2 protein and atypical clinical features of the misclassified cancer in a BRCA2 mutation carrier, we performed polymerase chain reaction and sequence analyses on this cancer. The results showed continued presence of the BRCA2 wild-type allele in the cancer, which indicated that intact BRCA2 protein was present in this cancer.

CONCLUSION

This immunohistochemistry-based test (which takes only 4 hours) appears to identify BRCA2 hereditary cancer with high accuracy. The test also appears to diagnose the biochemical loss of BRCA2 protein in cancers (ie, BRCA2-mutant genotype), which will usually but not always agree with the presence of a germline BRCA2 mutation found by susceptibility testing by DNA sequencing of blood samples.

Loss of heterozygosity in the RAD51 and BRCA2 regions in breast cancer

BACKGROUND

Loss of heterozygosity (LOH) in the 15q14-21 and 13q12-13 regions can contribute to the inactivation of RAD51 and BRCA2 genes implicated in the pathogenesis of breast cancer. We investigated allelic losses in microsatellites in the RAD51 and BRCA2 regions, and their association with clinicopathological parameters in breast cancer.

METHODS

The LOH analysis was performed by amplifying DNA by PCR, using D15S118, D15S214, D15S1006 polymorphic markers in the 15q14-21 region and D13S260, D13S290 polymorphic markers in the 13q12-13 region in 36 sporadic breast cancer cases.

RESULTS

LOH in the RAD51 region ranged from 29% to 46% and in the BRCA2 region from 38% to 43% of informative cases. Eleven percent of the breast cancer cases displayed LOH for at least one studied marker in the RAD51 region exclusively. On the other hand, 44% of cases manifested statistically significant LOH for at least one microsatellite marker concomitantly in the RAD51 and BRCA2 regions. LOH in the RAD51 region similarly as in the BRCA2 region appeared to correlate with steroid receptors content and lymph node status.

DISCUSSION

The obtained results indicate that alteration in RAD51 region may contribute to the disturbances of DNA repair involving RAD51 and/or BRCA2 penetration and thus enhance the risk of breast cancer development.

Molecular genetic analysis of the BRCA2 tumor suppressor gene region in cutaneous squamous cell carcinomas

BACKGROUND

Germ line mutations of the BRCA2 tumor suppressor gene with subsequent loss of the remaining wild-type BRCA2 allele have been identified in up to 35% of familial breast cancer cases. A high frequency of allelic loss at the BRCA2 gene locus has also been reported in a variety of sporadic epithelial tumors including oesophageal squamous cell carcinomas (SCC), and sporadic head and neck SCC.

AIM

The present study aimed to examine the integrity of the BRCA2 gene in cutaneous SCC.

MATERIALS AND METHODS

Allelic imbalance/loss of heterozygosity (AI/LOH) was examined in 22 histologically confirmed cutaneous SCC at two microsatellite markers, D13S260 (centromeric to the BRCA2 gene) and D13S267 (telomeric to the BRCA2 gene). Immunohistochemical analysis of BRCA2 protein expression was also examined in the cutaneous SCC.

RESULTS

AI/LOH at the D13S260 locus was found in eight of the 19 informative SCC, and AI/LOH at the D13S267 locus was found in 12 of the 18 informative SCC. Seven SCC showed allelic loss at both markers, and six SCC showed retention of heterozygosity at both markers. Expression of BRCA2 protein was only detected in six of the normal epidermises and three of the 21 SCC examined.

CONCLUSION

AI/LOH of the BRCA2 gene region was found to be common in the cutaneous SCC.

Links between DNA double strand break repair and breast cancer: Accumulating evidence from both familial and nonfamilial cases

DNA double strand break (DSB) repair dysfunction increases the risk of familial and sporadic breast cancer. Advances in the understanding of genetic predisposition to breast cancer have also been made by screening naturally occurring polymorphisms. These studies revealed that subtle defects in DNA repair capacity arising from low-penetrance genes, or combinations thereof, are modified by other genetically determined or environmental risk factors and correlate to breast cancer risk. Overexpression of DSB repair enzymes, absence of surveillance factors and mutation or loss of heterozygosity in any of these genes contributes to the pathogenesis of sporadic breast cancers. The results identifying DSB repair defects as a common denominator for breast cancerogenesis focus attention on functional assays in order to assess DSB repair capacity as a diagnostic tool to detect increased breast cancer risk and to enable therapeutic strategies specifically targeting the tumor.

High frequency of somatic missense mutation of BRCA2 in female breast cancer from Taiwan

Somatic mutation of BRCA2 has been thought to be rare in breast cancers, though common allelic deletions in the BRCA2 locus (13q12-q13) imply an important role of somatic mutation in these tumors. Reasons of the reported rare incidence could be related to very few studies focusing on the mutational analysis of BRCA2 in sporadic tumors. The mutational status of the BRCA2 gene in exon11, the largest exon harboring the RAD51 interacting BRC domains which are critical for BRCA2 function, was screened by polymerase chain reaction/single strand conformation polymorphism (PCR-SSCP) analysis followed by direct sequencing. Tumor and paired normal tissue sample from 175 patients unselected for family history or age were taken after mastectomy for breast cancer and evaluated. There were 20 mutations of BRCA2 gene in exon 11 in 15 cases (15/175, 8.6%). Most mutations we identified were point mutation (19/20, 95%), except for one nucleotide insertion. Furthermore, among these mutations, missense mutations comprised 80% (16/20) of the BRCA2 mutations. All mutations we found were novel mutation after searched in the BIC database. There were three recurrent mutations at codon 1904; and two recurrent mutations at 1907, 1936, 1937 and 1968, respectively. The mutations were associated with ductal carcinoma in situ (P=0.038) and borderline with low histological grade (P=0.072). Besides, there were three cases possessing multiple mutations in the region we studied and one of them demonstrated aggressive lymph node metastasis. These findings implicated that somatic mutations of BRCA2 genes may play a significant role in the pathogenesis of breast carcinoma in Taiwan. In addition, those events were associated with some early clinicopathological features.

Differential association of BRCA1 and BRCA2 genes with some breast cancer-associated genes in early and late onset breast tumors

BACKGROUND

Accumulating evidence indicating more aggressive features of breast carcinoma (BC) in young women than their older counterparts have raised the question of whether these differences are present at the genetic level.

METHODS

For this purpose, we performed a comparative analysis of the frequency of deletions of BRCA1, BRCA2, BRCAX, TP53, ATM, and RB1 and amplification of Cyclin D1 and also studied the interrelation and prognostic significance of these genetic alterations in 30 early onset (< or =40 years) and 33 late onset (>40 years) cases of BC. These gene alterations were also studied in 11 other types of breast lesions.

RESULTS

A differential pattern of alterations (deletion/amplification) was observed in the two age groups, with the sequence in younger women being BRCA1 (72%), TP53 (71%), ATM (64%), BRCA2 (62%), RB1 (60%), Cyclin D1 (43%), and BRCAX (24%) and that in the older group being TP53 (66%), RB1 (63%), BRCA1 (56%), ATM (53%), BRCA2 (45%), Cyclin D1 (24%), and BRCAX (23%). Similar, differential correlations were also seen with several clinicopathological parameters, prognosis, and combinations of alterations among these genes in the two age groups.

CONCLUSIONS

Differential frequencies and interrelationships of genetic alterations and prognoses in these two age groups indicate that the molecular pathways for the development of tumors in both age groups may not be similar, though the ultimate effect is deregulation of cell cycle checkpoints and defects in the DNA repair pathway.

Male breast cancer--an andrological disease: risk factors and diagnosis

Gynaecomastia, the enlargement of the male breast, is considered as an andrological disease. To date, a review on male breast cancer (MBC) has not been published in an andrological journal. The papers underlying this review were published from authors of different institutions: Clinical Genetics, Dermatology, Gynaecology, Internal Medicine, Oncology, Pathology, Psychiatry, Radiology and Surgery. MBC accounts for approximately 1% of breast cancer patients. A total of 182 men died of breast cancer in 1999, in Germany. In the US, 1500 new cases per year occur. MBC accounts for <5% of surgically removed breast lumps. Diseases with increased oestrogen action increase the risk of MBC. Mutations of distinct genes are estimated to account for up to roughly 10% of MBC. BRCA1 and BRCA2 gene mutations are responsible for approximately 80% of the families with hereditary breast cancer. The diagnosis of MBC is not possible without histological examination. Different diagnostic procedures such as clinical diagnosis, sonography, mammography, fine-needle biopsy and core needle facilitate the decision whether a biopsy is necessary.