MicroRNA 146a suppresses tumor progression and enhances therapeutic sensitivity by targeting the EGFR pathway in BRCA1-associated basal-like breast cancers

Background: Most breast cancers arising in BRCA1-mutation carriers are triple negative (TN). Therefore, it has been suggested that TN status is intrinsic to BRCA1-mutated tumors. However, 10 to 20% of BRCA1-associated breast cancers are estrogen receptor positive (ER+). As these tumors arise more often in older patients, and have less aggressive tumor characteristics, it has been suggested that these tumors are ‘sporadic’ and not related to BRCA1 deficiency. With the introduction of targeted treatments specific for tumors with a non-functioning BRCA1 or BRCA2 gene (i.e. PARP-inhibitors), the question whether the BRCA genes are impaired in the tumor, is highly relevant. Therefore, we performed a genomic analysis of a series of BRCA1-associated ER+ tumors, and compared them with BRCA1-associated TN tumors, as well as BRCA2-associated and sporadic breast cancers. Material and Methods: Genomic profiling of 18 BRCA1-associated ER+ tumors was performed using Nimblegen 135K arrays. We previously developed a BRCA1-like and BRCA2-like genomic profile, containing specific copy number alterations for respectively BRCA1-associated and BRCA2-associated breast cancer. These genomic profiles were applied on the current series. In addition, the BRCA1 promoter methylation status was determined, and LOH analysis was performed to assess if the wildtype or mutant allele was lost in the tumor. Results were compared with BRCA1 associated ER- tumors, BRCA2 associated tumors, and sporadic ER+ and TN tumors. Results: Only 2 out of 18 ER+ BRCA1 associated tumors showed a BRCA1-like genomic profile, while 90% of all ER- BRCA1-associated tumors show this genomic profile. Interestingly, 11 out of 18 ER+ BRCA1-associated tumors showed a BRCA2-like genomic profile. BRCA1 promoter methylation was absent in ER+ BRCA1-associated tumors, similar to TN BRCA1-associated tumors. LOH analysis was possible in 12 tumors, loss of the wildtype BRCA1 allele was shown in 10 out of 12 ER+ BRCA1-mutated tumors. One sample showed loss of the mutant allele, while another sample did not show loss at the BRCA1 locus. The genomic profiles of ER+ BRCA1-associated tumors were more similar to BRCA2-associated breast cancers and sporadic ER+ breast tumors than to BRCA1-associated TN tumors. Conclusion: The majority of BRCA1-associated ER+ tumors did not show a BRCA1-like genomic profile, even though LOH analysis indicated that loss of the wildtype BRCA1 allele was a frequent event. Therefore, it is likely that the complete loss of the BRCA1 gene plays a crucial role in tumorgenesis in this group of breast tumors. Remarkably, a BRCA2-like genomic profile was observed in the majority of ER+ BRCA1 associated tumors in this series. A clinical consequence of our findings is that ER+ BRCA1-associated breast tumors are probably highly sensitive to PARP inhibitors, similar to TN BRCA1-associated breast cancers. However, as ER+ BRCA1-mutated tumors clearly have different tumor characteristics compared to TN BRCA1-mutated tumors, they should be considered as a special group, and response to therapies exploiting the BRCA1 gene defect should be specifically monitored in this subgroup. Citation Format: Esther H. Lips, Rashmie Debipersad, Esther Scheerman, Lennart Mulder, Lizet E. van der Kolk, Jelle Wesseling, Frans B.L. Hogervorst, Petra M. Nederlof. The genomic profile of BRCA1-associated estrogen-receptor positive breast cancer does not resemble BRCA1-associated triple negative cancers, but is more similar to BRCA2-associated breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A27.

Targeted Chemotherapy? Platinum in <i>BRCA1</i>-Dysfunctional Breast Cancer

Introduction: Checkpoint kinase 2 (CHEK2) is a tumor suppressor gene, which regulates cell cycle in response to DNA damage response. Selected CHEK2 germline mutations have been shown to confer an increased risk of breast cancer development. Multiple founder mutations in CHEK2 have been identified, and meta analyses have shown that CHEK2 truncating variants confer a higher breast cancer risk than missense variants. Here, we assessed the phenotype and repertoire of genetic alterations of breast cancers from 33 patients with CHEK2 pathogenic germline variants. Materials and methods: We performed targeted capture massively parallel sequencing (≥410 genes) of tumor and normal samples from 13 patients with CHEK2 pathogenic germline variants, and retrieved whole exome sequencing (WES) data (BAM files) of tumor and normal samples from 20 patients with CHEK2 germline pathogenic variants included in the TCGA breast cancer study. In addition, we retrieved WES data of BRCA1, BRCA2 and ATM associated breast cancers from TCGA and Weigelt et al. (JNCI 2018). Somatic mutations, copy number alterations, mutational signatures and large-scale transitions (LSTs) were defined using state-of-the-art bioinformatics algorithms. Results: Of the 33 CHEK2-associated breast cancers included in this study, 21 had missense and 12 had loss-of-function (LoF) germline mutations, and 81% were ER-positive and 12% HER2-positive. CHEK2-associated breast cancers statistically significantly less frequently displayed an ER-negative/HER2-negative phenotype (0%) than BRCA1- (80%) or BRCA2-associated (33%) breast cancers (BRCA1, p&amp;lt;0.0001 for both comparisons), but were similar to ATM-associated breast cancers. Biallelic inactivation of CHEK2 through loss of heterozygosity (LOH) of the wild-type allele was present in 17 of 33 samples (52%). LOH of the CHEK2 wild-type allele was significantly more frequent in tumors with LOF mutations than in those with missense mutations (78% vs 36%, respectively; p=0.0394). PIK3CA (36%) and GATA3 (33%) were the two most recurrently mutated genes in these samples. TP53 somatic mutations were detected in five cases, four of which harbored missense CHEK2 germline mutations. Unlike BRCA1- and BRCA2-associated breast cancers, but akin to ATM-associated breast cancers, CHEK2-associated breast cancers lacked the mutational signature associated with homologous recombination (HR) DNA repair defects (i.e. signature 3) and only five cases displayed high LST scores. Conclusion:CHEK2-associated breast cancers are phenotypically and genetically distinct from BRCA1- and BRCA2-associated breast cancers, but similar to ATM-associated breast cancers. Akin to ATM-associated breast cancers, CHEK2-associated breast cancers are preferentially ER-positive, lack genomics features consistent with defective HR, and have a repertoire of somatic genetic alterations similar to those of non-BRCA1/2 ER-positive breast cancers. Our results suggest that either CHEK2 germline mutations contribute to an increased risk of breast cancer independently of the HR DNA repair defects or that the mutational signatures caused by CHEK2 pathogenic germline mutations differ from those caused by pathogenic germline mutations affecting bona fide HR-related genes (e.g. BRCA1, BRCA2 and PALB2). Citation Format: Kumar R, Pei X, Selenica P, Wen HY, Powell S, Robson M, Riaz N, Reis-Filho JS, Weigelt B, Mandelker D. The landscape of somatic genetic alterations in breast cancers from CHEK2 germline mutation carriers [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-04-01.

Background: Most invasive breast cancers (IBC) in BRCA1 mutation carriers are ER negative (-) and have a basal-like phenotype by expression array analysis. These tumors also have a characteristic constellation of histologic features including high grade, high mitotic rate, prominent lymphoid infiltrate, circumscribed or pushing margins, and geographic necrosis or a central fibrotic focus and typically lack ER, PR and HER2 expression (triple negative). ER positive (+) breast cancers also occur in women with germline BRCA1 mutations, but these tumors are less frequent and less well characterized. We previously reported that ER+ BRCA1-associated IBC show a wider spectrum of histologic types and grades than ER- cancers that occur in these patients. We raised the possibility that at least some ER+ BRCA1-associated IBC may be sporadic rather than mutation-related. However, it is not known how the features of these ER+ BRCA1-associated IBC compare with those of sporadic ER+ IBC.Design: To address this issue, we performed a case-control study of 60 ER+ BRCA1-associated IBC (cases) matched on age and year of diagnosis with 174 ER+ sporadic breast cancers (controls). Histologic sections of cases and controls were reviewed and the pathologic features were compared with each other as well with those of 85 ER- IBC that developed in BRCA1 mutation carriers.Results: Histologic features are summarized in the Table. When compared with ER+ controls, ER+ BRCA1-associated IBC were significantly more likely to be invasive ductal carcinomas (78% vs 58%;p=0.005), histologic grade 3 (47% vs 27%;p=0.006), and to have a high mitotic rate (29% vs 9%;p=0.0003). However, all of these features were significantly less frequent in ER+ BRCA1-associated IBC than in ER- BRCA1-associated IBC (p&amp;lt;0.001 for all comparisons). ER+ BRCA1-associated IBC and ER+ controls were not significantly different from each other with regard to the frequency of moderate-severe lymphoid infiltrate, the presence of geographic necrosis or the presence of a fibrotic focus, but the frequency of all of these features in both groups was significantly lower than in ER- BRCA1-associated IBC (p&amp;lt;0.01 for all comparisons). ER+ ControlsER+ BRCA1ER- BRCA1 N=174N=60N=85Histologic Type Invasive Ductal58%78%96%Other42%22%4%Histologic Grade 327%47%96%1 or 273%53%4%Mitotic Rate ≥10/10 HPF9%29%93%&amp;lt;10/10 HPF91%71%7%Tumor Margin Invasive96%90%37%Pushing/Circumscribed4%10%63%Lymphoid Infiltrate Moderate-Severe16%7%30%Other84%93%70%Fibrotic Focus Present7%12%56%Absent93%88%44%Geographic Necrosis Present2%5%50%Absent98%95%50% Conclusions: ER+ breast cancers arising in women with BRCA1 germline mutations appear to be pathologically "intermediate" between ER- BRCA1-associated breast cancers and ER+ sporadic breast cancers. This raises the possibility that some ER+ BRCA1-associated invasive breast cancers are mutation-related and others are sporadic or that there is a unique mechanism by which ER+ cancers develop in mutation carriers. Immunophenotypic and molecular studies are in progress to further characterize this interesting group of tumors.This work was supported by a grant from the Breast Cancer Research Foundation. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5162.

Introduction:Pathogenic and/or founder germline variants in the ataxia-telangiectasia mutated (ATM) gene confer an increased breast cancer (BC) risk. The protein kinase ATM plays a central role inDNA double-strand break-repair and in the activation of downstream targets such as p53 and BRCA1. We sought to define the repertoire of somatic genetic alterations of BCs from patients with pathogenic germline ATM mutations and whether somatic loss of heterozygosity (LOH) of ATM would be present in these cancers. Methods: 21 BCs from ATM germline mutation carriers were microdissected. Tumor and normal DNA samples were subjected to whole-exome sequencing (WES, n=12) or massively parallel sequencing targeting all coding regions and selected intronic and regulatory regions of 410 key cancer genes (n=9). Somatic mutations, copy number alterations, cancer cell fractions, large-scale state transitions (LSTs) and mutational signatures were defined using state-of-the-art bioinformatics algorithms. ABSOLUTE and FACETS were employed to assess LOH of the wild-type allele of ATM. Results: Of the patients included in this study, 71%, 24% and 5% of cases harbored ATM missense (all but one p.V2424G), frame-shift and nonsense germline mutations, respectively. All tumors were ER-positive and four (19%) were HER2-positive. The median age of the patients was 46 years (32–79 years). Our analyses revealed biallelic inactivation of ATM through LOH of the wild-type allele in 16 of 21 cases (76%), and second somatic ATM mutations were not found. The median number of non-synonymous somatic mutations was 38 (range 15-113) and 2 (range 0-8)in tumors subjected to WES and targeted sequencing, respectively. The repertoire of somatic genetic alterations of ATM-associated BCs was found to be heterogeneous, including clonal PIK3CA mutations (24%), GATA3 mutations (19%), FANCI amplifications (19%) and CCND1 amplifications (14%). Importantly, however, no somatic mutations affecting TP53 were found. Analysis of the WES data revealed that 5 (42%) ATM-associated BCs displayed high LST scores, all of which harbored bi-allelic ATM inactivation. In contrast to BRCA1- and BRCA2-associated BCs, which frequently display the mutational signature 3 associated with defective homologous recombination DNA repair, the ATM-associated BCs studied displayed the ageing mutational signature (i.e. signature 1). Comparison of the mutational profiles of the ATM--associated BCs subjected to WES (n=12) with those of BRCA1- (n=11) and BRCA2-associated (n=10) BCs from The Cancer Genome Atlas revealed that TP53 was more frequently mutated in BCs from BRCA1 germline mutation carriers (0% vs 72%, P&amp;lt;0.001), while no differences with BRCA2-associated BCs were found. Conclusion: ATM-associated BCs frequently display bi-allelic ATM inactivation through LOH of the wild-type allele and a subset of these cases displayed high levels of LSTs. These findings suggest that at least in a subset of ATM-associated BCs, biallelic inactivation of ATM rather than a dominant negative effect of the germline mutation may be the mechanism of inactivation of this tumor suppressor gene. The repertoire of somatic genetic alterations of ATM-associated BCs is heterogeneous, with a noticeable lack of TP53 somatic mutations. Citation Format: Weigelt B, Bi R, Kumar R, James PA, Thorne H, Couch FJ, Eccles DM, Blows F, Geyer FC, Li A, Selenica P, Lim RS, Blecua P, Shen R, Wen H, Robson ME, Reis-Filho JS, Chenevix-Trench G. The landscape of somatic genetic alterations in breast cancers from ATM germline mutation carriers [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD1-15.

Survival and prognostic factors in BRCA1-associated breast cancer

Patients with BRCA-associated triple negative breast cancer (TNBC) have few effective treatment options. PARP inhibitors are promising, and we recently showed they induce an influx of white blood cells, including CD8+ T-cells and macrophages into the tumor. The influx of CD8+ cells, mediated by activation of the STING pathway in tumor cells, contributes substantially to efficacy of PARP inhibition in mice. Strikingly, in these studies, the greatest infiltration of immune cells into the tumor was macrophages. Given objective responses to PARP inhibition have been observed in clinical trials but the benefits are transitory, we hypothesized that this was presumably due to a suppressive tumor microenvironment, driven by tumor macrophages. To better understand the molecular basis of resistance to PARP inhibitors, we used high dimensional single-cell immune profiling on human TNBC. We observed a ≥10-fold increase in TAMs in BRCA-associated TNBC compared to BRCA-wildtype TNBC. Using a pre-clinical model of BRCA1-deficient triple-negative breast cancer, we found that PARP inhibitors not only further increased TAM abundance but also induced functional and phenotypic changes associated with STING pathway activation, antigen presentation, and chemokine and cytokine signaling. PARP inhibitors increased the frequency of TAMs expressing co-stimulatory molecules CD80 and CD86 as well as the activation and maturation marker CD40, which are indicative of an anti-tumor phenotype. We also identified a novel negative feedback mechanism which limits the functionality of the anti-tumor TAMs, and is consistent with induction of an immune suppressive macrophage population. Utilizing transcriptomic, proteomic and metabolic profiling of ex vivo cultured human myeloid cells, we identified multiple biological processes associate with PARP inhibition, showing that these drugs directly affect macrophage states and phenotypes. Remarkably, in the pre-clinical BRCA1-deficient TNBC model, the novel combination of PARP inhibition with macrophage modulation significantly extended remissions obtained with PARP inhibitor therapy only, and this advantage persisted when treatment was discontinued, suggestive of a durable reprogramming of the tumor microenvironment. Moreover, CD8+ cells were required for the extension of PARP inhibitor-induced remissions, suggesting that targeting macrophages lifted the constraints imposed by pro-tumor macrophages on CD8+ T cell-mediated tumor cell killing. We identify mechanisms related to macrophage and T-cell activation that increase PFS and provide evidence that TAMs may serve as targets for new therapeutic interventions designed to overcome PARP inhibitor resistance in BRCA-associated TNBC. Citation Format: Jennifer L Guerriero, Anita K Mehta, Emily M Cheney, Jessica A. Castrillon, Jia-Ren Lin, Mateus de Oliveira Taveira, Olmo Sonzogni, Constantia Pantelidou, Christina A Hartl, William M Oldham, Nathan T Johnson, Sarah A Boswell, Marian Kalocsay, Matthew J Berberich, Sholin Mei, Dan Wang, Shawn Johnson, Brett Gross, Deborah A Dillon, Mikel Lipschitz, Evisa Gjini, Scott Rodig, Sandro Santagata, Judy E Garber, Nadine Tung, Peter Sorger, Geoffrey I Shapiro, Gerburg M Wulf, Elizabeth A Mittendorf. PARP inhibition modulates the infiltration, phenotype and function of tumor-associated macrophages (TAMs) in BRCA-associated breast cancer and can be augmented by harnessing the anti-tumor potential of TAMs [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-04-01.

Patients with BRCA-associated triple-negative breast cancer (TNBC) have few effective treatment options. PARP inhibitors are promising, and we recently showed they induce an influx of white blood cells, including CD8+ T cells and macrophages into the tumor. The influx of CD8+ cells, mediated by activation of the STING pathway in tumor cells, contributes substantially to efficacy of PARP inhibition in mice. Strikingly, in these studies the greatest infiltration of immune cells into the tumor was macrophages. Given that objective responses to PARP inhibition have been observed in clinical trials but the benefits are transitory, we hypothesized that this was due to a suppressive tumor microenvironment, driven by tumor macrophages. To better understand the molecular basis of resistance to PARP inhibitors, we used high-dimensional single-cell immune profiling on human TNBC. We observed a ≥10-fold increase in TAMs in BRCA-associated TNBC compared to BRCA-wild-type TNBC. Using a preclinical model of BRCA1-deficient triple-negative breast cancer, we found that PARP inhibitors not only further increased TAM abundance but also induced functional and phenotypic changes associated with STING pathway activation, antigen presentation, and chemokine and cytokine signaling. PARP inhibitors increased the frequency of TAMs expressing costimulatory molecules CD80 and CD86 as well as the activation and maturation marker CD40, which are indicative of an antitumor phenotype. We also identified a novel negative feedback mechanism that limits the functionality of the anti-tumor TAMs and is consistent with induction of an immune-suppressive macrophage population. Utilizing transcriptomic, proteomic, and metabolic profiling of ex vivo cultured human myeloid cells, we identified multiple biologic processes associated with PARP inhibition, showing that these drugs directly affect macrophage states and phenotypes. Remarkably, in the preclinical BRCA1-deficient TNBC model, the novel combination of PARP inhibition with macrophage modulation significantly extended remissions obtained with PARP inhibitor therapy only, and this advantage persisted when treatment was discontinued, suggestive of a durable reprogramming of the tumor microenvironment. Moreover, CD8+ cells were required for the extension of PARP inhibitor-induced remissions, suggesting that targeting macrophages lifted the constraints imposed by protumor macrophages on CD8+ T cell-mediated tumor cell killing. We identify mechanisms related to macrophage and T-cell activation that increase PFS and provide evidence that TAMs may serve as targets for new therapeutic interventions designed to overcome PARP inhibitor resistance in BRCA-associated TNBC. Citation Format: Anita K. Mehta, Emily M. Cheney, Jessica A. Castrillon, Jia-Ren Lin, Mateus de Oliveira Taveira, Christina A. Hartl, Nathan T. Johnson, William M. Oldham, Marian Kalocsay, Sarah A. Boswell, Olmo Sonzogni, Constantia Pantelidou, Brett P. Gross, Shawn Johnson, Deborah A. Dillon, Sandro Santagata, Judy E. Garber, Nadine Tung, Elizabeth A. Mittendorf, Gerburg M. Wulf, Geoffrey I. Shapiro, Peter K. Sorger, Jennifer L. Guerriero. PARP inhibition modulates the infiltration, phenotype, and function of tumor-associated macrophages (TAMs) in BRCA-associated breast cancer and can be augmented by harnessing the antitumor potential of TAMs [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A105.

1539 Background: Hispanic women with BC present at a younger age, have a higher frequency of BRCA mutations and show a worse incidence-to-mortality ratio than non-Hispanic women. Information regarding the characteristics of BRCA-associated BC in Hispanics is limited. Here, we assess differences in BRCA-associated BC between Hispanic patients in the US and in LatAm. Methods: Hispanic patients from the US and LatAm (Mexico, Colombia, Peru, and Puerto Rico) with a history of BRCA-associated BC enrolled in the Clinical Cancer Genomics Community Research Network registry were included. We compared the genetic, demographic, clinical and pathologic characteristics between Hispanics from the US and LatAm using Fisher’s exact test and x2statistics. Results: Between 1997 and 2016, 3670 Hispanic patients with a history of BC from LatAm (n = 1341) and the US (n = 2329) were identified, of which 490 (13.3%) had a deleterious BRCA mutation. The frequency of BRCA mutations was similar in Hispanics from LatAm (13.8%, n = 185) and the US (13.1%, n = 305). No significant differences were found in the frequency of BRCA1 vs BRCA2 mutations between patients from LatAm (BRCA1 68%, BRCA2 31.8%) and the US (BRCA1 61.3%, BRCA2 39%) (p = .12). The most frequent mutations found in BRCA1 were: ex 9-12del (LatAm n = 24, US n = 15), 185delAG (LatAm n = 13, US n = 18) and 943ins10 (LatAm n = 3, US n = 8), and in BRCA2 3492insT (LatAm n = 3, US n = 28). Mean age at BC diagnosis was 39.1 (SD 9.5) in LatAm and 41.7 (SD 10.6) in the US (p = 0.01). US patients were significantly more likely to present with Stage 0-II BC than those from LatAm (77.1% vs. 47.6%, p &lt; .001). We found no differences in the proportion of hormone receptor positive tumors between patients from LatAm (45%) and the US (47%) (p = .78). Conclusions: The frequency of BRCA-associated BC was similar between Hispanics in LatAm and the US. Women from LatAm with BRCA mutations present at a younger age, as seen for sporadic BC; the causes for this finding warrant further research. Women with BRCA-associated BC in LatAm are more likely to have advanced BC at presentation, which may be a reflection of disparities and barriers in access to care.

Breast carcinoma is common in women and forms an integral part of the BRCA familial cancer syndromes. As breast cancer is considered a heterogeneous disease, clinicians have traditionally relied on clinical and morphologic findings, as well as hormone receptor/HER-2 status for prognostic and predictive categorisation of tumours. Recently, breast cancer subclassification has been aided by the discovery of various gene expression profiles, compiled after simultaneous examination of multiple tumour biomarker genes. Basal-like breast cancer was delineated using this methodology and demonstrates significant overlap with so-called triple negative and BRCA1-associated breast carcinomas. This article describes the pathology and biology of these three groups of tumours and examines the relationship between them. Therapeutic implications are also briefly discussed.

9648 Background: to evaluate the clinical features and outcomes of Breast Cancer (BC) patients with genetic susceptibility to this disease and to investigate the contribution of BRCA1 germline mutation to the phenotype of these tumors. Methods: we reviewed clinical and pathological records of 144 women with autosomal dominant inheritance of breast (+/- ovarian) cancer risk. All women underwent full genetic counseling. Of these, 101 selected patients with high probability of having a germ-line mutation were tested for BRCA1 mutation analysis. Exon 11 was screened for BRCA1 mutations using Protein Truncation Test; mutations detected were confirmed by Direct Sequencing. All the other exons were analyzed by DS. Results: the two different risk groups had similar clinical outcomes. Of the 57 patients with completed mutation analysis, 44 (77%) patients had wild type BRCA1, 8 (14%) had variants of unclear significance, 5 (8%) had deleterious mutations in BRCA1. With regard to entry criteria for BRCA1 genetic testing, mutations were detected in 5% (1/20), 2,5% (1/41), 16% (2/12) and 16% (1/6) of women with family history, early onset BC (< 40 years), Breast-Ovarian Cancer (BOC) and early onset plus Bilateral Breast Cancer, respectively. BRCA1 Associated Breast Cancers (BABC) were more likely to have histological grade 3 and high proliferation rate than negative cases (40% v 27%; 60% v 45%). These differences were not statistically significant. BABC were significantly more likely to be estrogen receptor-negative (67% v 16%, P = .04). Though not significant, all valuable tumors with BRCA1 mutations were HER-2/neu negative. In the entire cohort, there were no significant differences between BABC and non-BABC in 5 year relapse free survival (60% v 78%, P = not significant [NS]), 5 year event free survival (60% v 66%, P = NS), or 5 year overall survival. Conclusions: BABC seem to present with adverse molecular and histopathologic features when compared with cases not associated with BRCA1 mutations. However, the prognosis of BABC appears to be similar to that of non associated cancer. No significant financial relationships to disclose.

9648 Background: to evaluate the clinical features and outcomes of Breast Cancer (BC) patients with genetic susceptibility to this disease and to investigate the contribution of BRCA1 germline mutation to the phenotype of these tumors. Methods: we reviewed clinical and pathological records of 144 women with autosomal dominant inheritance of breast (+/- ovarian) cancer risk. All women underwent full genetic counseling. Of these, 101 selected patients with high probability of having a germ-line mutation were tested for BRCA1 mutation analysis. Exon 11 was screened for BRCA1 mutations using Protein Truncation Test; mutations detected were confirmed by Direct Sequencing. All the other exons were analyzed by DS. Results: the two different risk groups had similar clinical outcomes. Of the 57 patients with completed mutation analysis, 44 (77%) patients had wild type BRCA1, 8 (14%) had variants of unclear significance, 5 (8%) had deleterious mutations in BRCA1. With regard to entry criteria for BRCA1 genetic testing, mutations were detected in 5% (1/20), 2,5% (1/41), 16% (2/12) and 16% (1/6) of women with family history, early onset BC (< 40 years), Breast-Ovarian Cancer (BOC) and early onset plus Bilateral Breast Cancer, respectively. BRCA1 Associated Breast Cancers (BABC) were more likely to have histological grade 3 and high proliferation rate than negative cases (40% v 27%; 60% v 45%). These differences were not statistically significant. BABC were significantly more likely to be estrogen receptor-negative (67% v 16%, P = .04). Though not significant, all valuable tumors with BRCA1 mutations were HER-2/neu negative. In the entire cohort, there were no significant differences between BABC and non-BABC in 5 year relapse free survival (60% v 78%, P = not significant [NS]), 5 year event free survival (60% v 66%, P = NS), or 5 year overall survival. Conclusions: BABC seem to present with adverse molecular and histopathologic features when compared with cases not associated with BRCA1 mutations. However, the prognosis of BABC appears to be similar to that of non associated cancer. No significant financial relationships to disclose.

Loss of Nuclear BRCA1 Expression in Breast Cancers Is Associated with a Highly Proliferative Tumor Phenotype

Since BRCA1 associated breast cancers are frequently classified as hormone receptor negative or even triple negative, the application of endocrine therapies is rather limited in these patients. Like hormone receptors that bind to estrogen or progesterone, thyroid hormone receptors (TRs) are members of the nuclear hormone receptor superfamily. TRs might be interesting biomarkers - especially in the absence of classical hormone receptors. The current study aimed to investigate whether TRs may be specifically expressed in BRCA1 associated cancer cases and whether they are of prognostic significance in these patients as compared to sporadic breast cancer cases. This study analyzed TRα and TRβ immunopositivity in BRCA1 associated (n = 38) and sporadic breast cancer (n = 86). Further, TRs were studied in MCF7 (BRCA1 wildtype) and HCC3153 (BRCA1 mutated) cells. TRβ positivity rate was significantly higher in BRCA1 associated as compared to sporadic breast cancers (p = 0.001). The latter observation remained to be significant when cases that had been matched for clinicopathological criteria were compared (p = 0.037). Regarding BRCA1 associated breast cancer cases TRβ positivity turned out to be a positive prognostic factor for five-year (p = 0.007) and overall survival (p = 0.026) while TRα positivity predicted reduced five-year survival (p = 0.030). Activation of TRβ resulted in down-modulation of CTNNB1 while TRα inhibition reduced cell viability in HCC3153. However, only BRCA1 wildtype MCF7 cells were capable of rapidly degrading TRα1 in response to T3 stimulation. Significantly, this study identified TRβ to be up-regulated in BRCA1 associated breast cancer and revealed TRs to be associated with patients’ prognosis. TRs were also found to be expressed in triple negative BRCA1 associated breast cancer. Further studies need to be done in order to evaluate whether TRs may become interesting targets of endocrine therapeutic approaches, especially when tumors are triple-negative.

Background. According to the literature, BRCA1-associated breast cancer (BC) most often belongs to the triple negative (TNBC) molecular subtype. The data on the contribution of other molecular subtypes to this group of patients differ among different studies.The study objective is to evaluate the frequency of different tumor molecular subtypes in BC patients with BRCA1 gene mutation treated in N. N. Blokhin National Medical Research Center of Oncology in the period from 2017 to 2020.Materials and methods. The study included BC patients with a mutation in the BRCA1 gene (n = 209) identified as a result BRCA1 mutation screening of patients with BC. DNA diagnostics was carried out on blood samples of patients using the real-time polymerase chain reaction method. After analyzing the patients primary documentation clinical and morphological data were taken into account: the age of diagnosis, the stage of the disease, the results of immunohistochemical studies (estrogen receptor status, progesterone receptor status, HER2 expression, Ki-67 proliferation index). The assignment to the particular molecular tumour subtypes was performed according to estrogen receptor status, progesterone receptor status, HER2 status and Ki67 value.Results. Clinical and pathomorphological data of 209 patients with BRCA1-associated BC were analyzed. The age at diagnosis ranged from 23 to 72 years, the median age was 40 years, the mean age was 41.46 ± 9.82 years. BC associated with BRCA1 was found to be TNBC in 71.3 % and luminal B, HER2 negative (LumB–) in 19.1 % of the cases. Other tumour subtypes were much less common: luminal B, HER2 positive (LumB+) in 7.2 %, luminal A (LumA) in 1 % and HER2-positive (HER2+) in 1.4 % of the cases. The frequency of subtypes was estimated in different age groups (1st – patients 23–34 (n = 53), 2nd – 35–49 (n = 111), and 3rd – 50–72 (n = 45) years old). TNBC frequency was 81.1 % in the 1st group, 73.9 % in the 2nd and 53.4 % in the 3rd group; LumB– frequency was 15.1, 15.3 and 33.3 % respectively. Using the Fisher test it was shown that the differences in frequencies were statistically significant between groups 1st and 3 rd, as well as between groups 2 nd and 3 rd (p &lt;0.05).Conclusion. TNBC was the main molecular subtype in all age groups of BC patients with BRCA1 germinal mutation, TNBC frequency was lower in the older age group. LumB– subtype was also common in BRCA1-associated tumors especially in older women.