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BRCA1-mutated breast cancer is associated with basal-like disease; however, it is currently unclear if the presence of a BRCA1 mutation depicts a different entity within this subgroup. In this study, we compared the molecular features among basal-like tumors with and without BRCA1 mutations. Fourteen patients with BRCA1-mutated (nine germline and five somatic) tumors and basal-like disease, and 79 patients with BRCA1 non-mutated tumors and basal-like disease, were identified from the cancer genome atlas dataset. The following molecular data types were evaluated: global gene expression, selected protein and phospho-protein expression, global miRNA expression, global DNA methylation, total number of somatic mutations, TP53 and PIK3CA somatic mutations, and global DNA copy-number aberrations. For intrinsic subtype identification, we used the PAM50 subtype predictor. Within the basal-like disease, we observed minor molecular differences in terms of gene, protein, and miRNA expression, and DNA methylation variation, according to BRCA1 status (either germinal or somatic). However, there were significant differences according to average number of mutations and DNA copy-number aberrations, and four amplified regions (2q32.2, 3q29, 6p22.3, and 22q12.2), which are characteristic in high-grade serous ovarian carcinomas, were observed in both germline and somatic BRCA1-mutated breast tumors. These results suggest that minor, but potentially relevant, baseline molecular features exist among basal-like tumors according to BRCA1 status. Additional studies are needed to better clarify if BRCA1 genetic status is an independent prognostic feature, and more importantly, if BRCA1 mutation status is a predictive biomarker of benefit from DNA-damaging agents among basal-like disease.

Neurofibromatosis type 1 (NF1) is a common dominant autosomal disorder caused by mutations in the NF1 gene. The main manifestations of NF1 are café-au-lait spots, neurofibromas, intertriginous freckling, Lisch nodules, and malignancy, including peripheral nerve sheath tumors, central nervous system gliomas, and a variety of other tumors not so clearly defined. The association between NF1 and breast cancer or other gynecologic malignancies seems uncommon and has been scarcely referred in the literature. We describe a family with two females affected by both NF1 and early-onset breast cancer, and a male with NF1. We evaluated whether the concomitance of both disorders could be attributed to a NF1 mutation and its supposed increased risk of breast cancer or to the concurrence of two NF1 and BRCA1/2 germline mutations. Mutation analyses identified a frameshift mutation in BRCA1 and a nonsense mutation in NF1. Our findings stress the importance of considering all phenotypic features in families with both NF1 and breast tumors. To offer a specific risk assessment and management of both conditions, NF1 and BRCA1/2 cancer predisposing genes should be analyzed.

Large genomic rearrangements (LGRs) at the BRCA2 locus explain a non-negligible proportion of hereditary breast and ovarian cancer (HBOC) syndromes. The multiplex ligation and probe amplification (MLPA) assay has permitted in recent years to identify several families carrying LGRs at this locus, but very few such alterations have been fully characterized at the molecular level. Yet, molecular characterization is essential to identify recurrent alterations, to analyze the genetic mechanisms underlying such alterations, or to investigate potential genotype/phenotype relationships. We have used MLPA to identify BRCA2 LGRs in 7 out of 813 Spanish HBOC families previously tested negative for BRCA1 and BRCA2 small genomic alterations (substitutions and indels) and BRCA1 LGRs. We used a combination of long-range PCR, restriction mapping, and cDNA analysis to characterize the alterations at the molecular level. We found that Del Exon1-Exon2, Del Exon12-Exon16 and Del Exon22-Exon24 explain one family each, while Del Exon2 appears to be a Spanish founder mutation explaining four independent families. Finally, we have combined our data with a comprehensive review of the literature to reevaluate the genetic mechanisms underlying LGRs at the BRCA2 locus. Our study substantially increases the spectrum of BRCA2 LGRs fully characterized at the molecular level. Further on, we provide data to suggest that non-allelic homologous recombination has been overestimated as a mechanism underlying these alterations, while the opposite might be true for microhomology-mediated events.

It has been demonstrated that monoallelic PALB2 (Partner and Localizer of BRCA2) gene mutations predispose to familial breast cancer. Some of the families reported with germline PALB2 mutations presented male breast cancer as a characteristic clinical feature. Therefore, we wanted to investigate the contribution of germline PALB2 mutations in a set of 131 Spanish BRCA1/BRCA2-negative breast/ovarian cancer families with at least one male breast cancer case. The analysis included direct sequencing of all coding exons and intron/exon boundaries as well as a Multiplex Ligation-dependent Probe Amplification-based analysis of genomic rearrangements. For the first time we have identified a genomic rearrangement of PALB2 gene involving a large deletion from exon 7 to 11 in a breast cancer family. We have also identified several PALB2 variants, but no other obvious deleterious PALB2 mutation has been found. Thus, our study does not support an enrichment of PALB2 germline mutations in the subset of breast cancer families with male breast cancer cases. The identification of intronic and exonic variants indicates the necessity of assessing the implications of variants that do not lead to PALB2 truncation in the pathoghenicity of the PALB2 gene.

Background: There has been controversy regarding whether BRCA1 germline mutations favor female births or whether the sex imbalances observed are attributable to ascertainment bias. Our aims were to compare the sex ratios among offspring of BRCA1-positive, BRCA2-positive, and BRCA-negative families undergoing genetic testing in clinical programs, and to determine whether ascertainment bias is responsible for the observed preponderance of female offspring., Patients and Methods: A total of 145 breast and/or ovarian cancer families with mutations in BRCA1 (n = 83) or BRCA2 (n = 62), and 90 families without identifiable mutation were collected for the study from familial cancer clinics in Barcelona, Spain, and Boston, US. Sex ratio was analyzed among all births in the families and offspring of all (tested and obligate) carriers. In order to minimize the effect of family history of cancer, the analysis was also performed among offspring of the most recent generation of mutation-positive carriers who did not have affected children and compared with a control group comprised of the offspring of the most recent adult generation of non-carriers from families with a known mutation., Results: There was a statistically higher proportion of female births in all groups (BRCA1 59% (95% CI = 57-61%), BRCA2 58% (56-61%), and BRCA-negative 59% (56-61%), respectively). The female preponderance persisted in analyses limited to offspring of BRCA1 and BRCA2 carriers (61% (57-65%), and 62% (58-66%), respectively), with no differences between the two mutation groups. In contrast, the excess of female offspring disappeared when ascertainment or recall biases were minimized, 44% (37-52%), and 39% (26-53%) for BRCA1; 51% (44-58%), and 46% (33-60%) for BRCA2., Conclusions: Our findings suggest that there is no asymmetry in birth outcomes among BRCA1 or BRCA2 mutations carriers. Rather ascertainment bias in families participating in genetic testing, or in the family history information they provide is likely to account for excess of female offspring previously reported.