Breast Cancer Susceptibility Research Articles

Survival outcomes of BRCA1/BRCA2 mutated breast cancers: Study from a tertiary care cancer centre in India.

e22546 Background: There exists a discrepancy amongst various studies over the years on survival outcomes of BRCA (Breast cancer susceptibility gene) mutated breast cancers. Prevalence of BRCA mutation varies from 10 to 18% among Indian population and there is a paucity of data on the survival outcomes of this population. Methods: This ambispective observational study assessed the survival outcomes of 71 BRCA mutated breast cancer patients, treated with uniform protocol at AIIMS New Delhi between January 2014 to December 2022, using survival analysis and cox regression methods. Results: Amongst the 71 patients, BRCA1 and BRCA2 mutated cases were 52 (73.2%) and 19 (26.8%) respectively. The median age was 39 years (24-63 years) in both the groups. Positive family history for malignancy (BRCA1- 69.2% vs BRCA2- 36.8%) and incidence of Triple negative histology (BRCA1-82.7% VS 36.8%) were more commonly associated with BRCA1 positivity. Eight patients (11.3%) had synchronous cancer, most common being a contralateral breast primary. 4 patients (5.6%) developed metachronous cancer. Eighty percent of patients were premenopausal at presentation. There was no difference in stage at presentation, incidence of synchronous and metachronous cancers across both the groups. Of 71 patients, 18 (25%) and 17 (24%) patients underwent risk reducing mastectomy and risk reducing oophorectomy respectively. Thirty five (49.3%) presented with stage I & II disease, while 28 (34.4%) and 7 (9.9%) presented with stage III and metastatic disease respectively. Forty seven patients (67.1%) received neoadjuvant chemotherapy with pathologic complete response rate of 42.5% which was uniform among both the groups. Over the study period, 10 (14.1%) patients had disease relapse with 7 (70%) being metastatic and 3 patients died of the disease. With a median follow up of 36.9 months, 3-year disease free survival (DFS) was 84.2% (BRCA1: 81.1% vs BRCA2: 93.1%) and overall survival (OS) was 94.7% for both groups. Median DFS and OS were not achieved. BRCA type, receptor status, age and menopausal status were not predictors of survival in our study. Conclusions: In our study population of BRCA1/BRCA2 mutated breast cancer, survival outcomes were comparable to historical cohorts of Indian breast cancer patients. Thus, BRCA mutation positivity doesn’t seem to have any prognostic significance in breast cancer outcome.

Prevalence of BRCA1 and BRCA2 mutations in an unselected cohort of Indian women with breast cancer.

e13004 Background: Familial breast cancer accounts for 10-15% of breast cancer cases. The prevalence of germline pathogenic mutations in breast cancer susceptibility genes 1 and 2 ( BRCA1/2) among female breast cancer patients remained variable across studies depending on the population/settings studied. The estimate varied between 8-10% of the unselected female breast cancer population. There is a lack of data regarding the prevalence of BRCA1/2 among female breast cancer patients in India. Methods: This prospective observational study included consecutive patients with breast cancer in females, registered at All India Institute of Medical Sciences (AIIMS), New Delhi, India between the period of 1st September 2022 to 25th January 2023(5 months duration). The staging description was done as per anatomic TNM staging according to AJCC 7th edition. Mutation testing was performed in all patients by a standard next-generation sequencing (NGS) assay covering the BRCA1/2 gene. The reflex multiplex ligation by probe amplification method was performed in all cases that were negative by NGS. For patients with detected germline mutations in BRCA1/2, post-test counseling was done, and family screening was also advised. Results: A total of 210 female patients with breast cancer were sequentially included in the study. Young breast cancer (less than 35 years of age) constituted 40 (19.04%) cases. Thirty-eight patients (18.09%) women had a positive significant family history. The median age of the cohort was 46 years (range 18-85 years). Synchronous breast cancer was present in 7 (3.3%) cases. The stage distribution was stage I, 11(5.23%); stage II, 73 (34.76%); stage III, 83 (39.52%); and stage IV, 43 (20.47) %. One hundred and ten patients (52.38%) were hormone-receptor-positive, whereas 66 (31.42%) patients were HER2/neu positive. Triple-negative breast cancer (TNBC) was found in 65 (30.95%) cases. Overall, the prevalence of germline BRCA1/2 mutations was 35/210 (16.6%), which included BRCA 1 and 2 mutations in 22 (10.47%) and 12 (5.71) cases respectively. One case had mutations in both BRCA 1 and BRCA2. Young ( < 35) TNBCs (22 cases/210, 10.47%) have a high propensity for detecting pathogenic BRCA1 mutation (8/22, 36.36%). Conclusions: The prevalence of pathogenic BRCA1/2 in 16.6% of our cohort of unselected consecutive breast cancer patients. It is higher than that reported in the Western population likely due to the younger population and more proportion of triple-negative breast cancer patients in our cohort.

Validation of the BOADICEA model for predicting the likelihood of carrying pathogenic variants in eight breast and ovarian cancer susceptibility genes

BOADICEA is a comprehensive risk prediction model for breast and/or ovarian cancer (BC/OC) and for carrying pathogenic variants (PVs) in cancer susceptibility genes. In addition to BRCA1 and BRCA2, BOADICEA version 6 includes PALB2, CHEK2, ATM, BARD1, RAD51C and RAD51D. To validate its predictions for these genes, we conducted a retrospective study including 2033 individuals counselled at clinical genetics departments in Denmark. All counselees underwent comprehensive genetic testing by next generation sequencing on suspicion of hereditary susceptibility to BC/OC. Likelihoods of PVs were predicted from information about diagnosis, family history and tumour pathology. Calibration was examined using the observed-to-expected ratio (O/E) and discrimination using the area under the receiver operating characteristics curve (AUC). The O/E was 1.11 (95% CI 0.97–1.26) for all genes combined. At sub-categories of predicted likelihood, the model performed well with limited misestimation at the extremes of predicted likelihood. Discrimination was acceptable with an AUC of 0.70 (95% CI 0.66–0.74), although discrimination was better for BRCA1 and BRCA2 than for the other genes in the model. This suggests that BOADICEA remains a valid decision-making aid for determining which individuals to offer comprehensive genetic testing for hereditary susceptibility to BC/OC despite suboptimal calibration for individual genes in this population.

A common variant SNP rs1937810 in the MPP7 gene contributes to the susceptibility of breast cancer in the Chinese Han population.

Breast cancer (BC) is common cancer caused by environmental factors and genetic ones. Previous evidence has linked gene MAGUK P55 Scaffold Protein 7 (MPP7) to BC, despite that there has been no research evaluating the relationship between MPP7 genetic polymorphisms and BC susceptibility. We aimed to investigate the potential association of the MPP7 gene with the susceptibility to BC in Han Chinese individuals. In total, 1390 patients with BC and 2480 controls were enrolled. For genotyping, 20 tag SNPs were chosen. The serum levels of protein MPP7 were measured in all subjects using an enzyme-linked immunosorbent assay. Genetic association analysis was performed in both genotypic and allelic modes, and the relationship between BC patients' clinical features and genotypes of relevant SNPs was examined. The functional implications of significant markers were also evaluated. After adjusting for Bonferroni correction, SNP rs1937810 was found to be significantly associated with the risk of BC (p = 1.19 × 10-4 ). The odds ratio of CC genotypes in BC patients was 49% higher than in controls (1.49 [1.23-1.81]). Serum MPP7 protein levels were significantly higher in BC patients than in controls (p < 0.001). The protein level of the CC genotype was the highest, and that of the CT and TT genotypes decreased in turn (both p < 0.001). Our results linked SNP rs1937810 to the susceptibility of BC and the clinical features of BC patients. This SNP is also proved to be significantly related to the serum level of protein MPP7 in both BC patients and controls.

Development and testing of a polygenic risk score for breast cancer aggressiveness

Aggressive breast cancers portend a poor prognosis, but current polygenic risk scores (PRSs) for breast cancer do not reliably predict aggressive cancers. Aggressiveness can be effectively recapitulated using tumor gene expression profiling. Thus, we sought to develop a PRS for the risk of recurrence score weighted on proliferation (ROR-P), an established prognostic signature. Using 2363 breast cancers with tumor gene expression data and single nucleotide polymorphism (SNP) genotypes, we examined the associations between ROR-P and known breast cancer susceptibility SNPs using linear regression models. We constructed PRSs based on varying p-value thresholds and selected the optimal PRS based on model r2 in 5-fold cross-validation. We then used Cox proportional hazards regression to test the ROR-P PRS’s association with breast cancer-specific survival in two independent cohorts totaling 10,196 breast cancers and 785 events. In meta-analysis of these cohorts, higher ROR-P PRS was associated with worse survival, HR per SD = 1.13 (95% CI 1.06–1.21, p = 4.0 × 10–4). The ROR-P PRS had a similar magnitude of effect on survival as a comparator PRS for estrogen receptor (ER)-negative versus positive cancer risk (PRSER-/ER+). Furthermore, its effect was minimally attenuated when adjusted for PRSER-/ER+, suggesting that the ROR-P PRS provides additional prognostic information beyond ER status. In summary, we used integrated analysis of germline SNP and tumor gene expression data to construct a PRS associated with aggressive tumor biology and worse survival. These findings could potentially enhance risk stratification for breast cancer screening and prevention.

Breast cancer genomes from CHEK2 c.1100delC mutation carriers lack somatic TP53 mutations and display a unique structural variant size distribution profile

BackgroundCHEK2 c.1100delC was the first moderate-risk breast cancer (BC) susceptibility allele discovered. Despite several genomic, transcriptomic and functional studies, however, it is still unclear how exactly CHEK2 c.1100delC promotes tumorigenesis. Since the mutational landscape of a tumor reflects the processes that have operated on its development, the aim of this study was to uncover the somatic genomic landscape of CHEK2-associated BC.MethodsWe sequenced primary BC (pBC) and normal genomes of 20 CHEK2 c.1100delC mutation carriers as well as their pBC transcriptomes. Including pre-existing cohorts, we exhaustively compared CHEK2 pBC genomes to those from BRCA1/2 mutation carriers, those that displayed homologous recombination deficiency (HRD) and ER− and ER+ pBCs, totaling to 574 pBC genomes. Findings were validated in 517 metastatic BC genomes subdivided into the same subgroups. Transcriptome data from 168 ER+ pBCs were used to derive a TP53-mutant gene expression signature and perform cluster analysis with CHEK2 BC transcriptomes. Finally, clinical outcome of CHEK2 c.1100delC carriers was compared with BC patients displaying somatic TP53 mutations in two well-described retrospective cohorts totaling to 942 independent pBC cases.ResultsBC genomes from CHEK2 mutation carriers were most similar to ER+ BC genomes and least similar to those of BRCA1/2 mutation carriers in terms of tumor mutational burden as well as mutational signatures. Moreover, CHEK2 BC genomes did not show any evidence of HRD. Somatic TP53 mutation frequency and the size distribution of structural variants (SVs), however, were different compared to ER+ BC. Interestingly, BC genomes with bi-allelic CHEK2 inactivation lacked somatic TP53 mutations and transcriptomic analysis indicated a shared biology with TP53 mutant BC. Moreover, CHEK2 BC genomes had an increased frequency of > 1 Mb deletions, inversions and tandem duplications with peaks at specific sizes. The high chromothripsis frequency among CHEK2 BC genomes appeared, however, not associated with this unique SV size distribution profile.ConclusionsCHEK2 BC genomes are most similar to ER+ BC genomes, but display unique features that may further unravel CHEK2-driven tumorigenesis. Increased insight into this mechanism could explain the shorter survival of CHEK2 mutation carriers that is likely driven by intrinsic tumor aggressiveness rather than endocrine resistance.

A joint transcriptome-wide association study across multiple tissues identifies candidate breast cancer susceptibility genes

Genome-wide association studies (GWASs) have identified more than 200 genomic loci for breast cancer risk, but specific causal genes in most of these loci have not been identified. In fact, transcriptome-wide association studies (TWASs) of breast cancer performed using gene expression prediction models trained in breast tissue have yet to clearly identify most target genes. To identify candidate genes, we performed a GWAS analysis in a breast cancer dataset from UK Biobank (UKB) and combined the results with the GWAS results of the Breast Cancer Association Consortium (BCAC) by a meta-analysis. Using the summary statistics from the meta-analysis, we performed a joint TWAS analysis that combined TWAS signals from multiple tissues. We used expression prediction models trained in 11 tissues that are potentially relevant to breast cancer from the Genotype-Tissue Expression (GTEx) data. In the GWAS analysis, we identified eight loci distinct from those reported previously. In the TWAS analysis, we identified 309 genes at 108 genomic loci to be significantly associated with breast cancer at the Bonferroni threshold. Of these, 17 genes were located in eight regions that were at least 1 Mb away from published GWAS hits. The remaining TWAS-significant genes were located in 100 known genomic loci from previous GWASs of breast cancer. We found that 21 genes located in known GWAS loci remained statistically significant after conditioning on previous GWAS index variants. Our study provides insights into breast cancer genetics through mapping candidate target genes in a large proportion of known GWAS loci and discovering multiple new loci.

Effect on Germline Mutation Rate in a High-Risk Chinese Breast Cancer Cohort after Compliance with The National Comprehensive Cancer Network (NCCN) 2023 v.1 Testing Criteria.

The National Comprehensive Cancer Network (NCCN) testing criteria for the high-penetrance breast cancer susceptibility genes, specifically BRCA1, BRCA2, CDH1, PALB2, PTEN, and TP53, have been recently modified in 2023 to 2023 v.1. The following criteria have been changed: (1) from a person diagnosed with breast cancer at ≤45 to ≤50; (2) from aged 45-50 of personal breast diagnosis to any age of diagnosis with multiple breast cancers; and (3) from aged ≥51 of personal breast diagnosis to any age of diagnosis with family history listed in NCCN 2022 v.2. High-risk breast cancer patients (n = 3797) were recruited from the Hong Kong Hereditary Breast Cancer Family Registry between 2007 and 2022. Patients were grouped according to NCCN testing criteria 2023 v.1 and 2022 v.2. A 30-gene panel for hereditary breast cancer was performed. The mutation rates on high-penetrance breast cancer susceptibility genes were compared. About 91.2% of the patients met the 2022 v.2 criteria, while 97.5% of the patients met the 2023 v.1 criteria. An extra 6.4% of the patients were included after the revision of the criteria, and 2.5% of the patients did not meet both testing criteria. The germline BRCA1/2 mutation rates for patients meeting the 2022 v.2 and 2023 v.1 criteria were 10.1% and 9.6%, respectively. The germline mutation rates of all 6 high-penetrance genes in these two groups were 12.2% and 11.6%, respectively. Among the additional 242 patients who were included using the new selection criteria, the mutation rates were 2.1% and 2.5% for BRCA1/2 and all 6 high-penetrance genes, respectively. Patients who did not meet both testing criteria were those with multiple personal cancers, a strong family history of cancers not listed in the NCCN, unclear pathology information, or the patient's voluntary intention to be tested. The mutation rates of BRCA1/2 and the 6 high-penetrance genes in these patients were 5.3% and 6.4%, respectively. This study provided a real-world application of the revision of NCCN guidelines and its effect on the germline mutation rate in the Chinese population. Applying the updated criteria for further genetic investigation would increase the positive detection rate, and potentially more patients would benefit. The balance between the resource and outcome requires careful consideration.

173P Diet, genetic predisposition and the risk of breast cancer: A cohort study from the UK biobank

Dietary factors have been consistently associated with breast cancer risk, but evidence for their effects in women with different genetic susceptibility of breast cancer is scarce, and little is known about their interaction with alcohol consumption. We analyzed data from 261,857 female participants in the UK Biobank. Multivariable adjusted Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for associations between dietary factors and breast cancer risk. We further assessed its interaction with alcohol consumption and polygenic risk score (PRS) for breast cancer. Only processed meat and beef intake more than once a week were associated with a higher risk of breast cancer, especially in women who took alcohol ≥1/d [HR (95% CI):1.20(1.01, 1.42) and 1.35 (1.06, 1.73), respectively]. Fresh fruit intake was associated with reduced risk of breast cancer [HR (95% CI):0.76 (0.64, 0.89)]. There was an interaction between vegetable and fresh fruit intake and alcohol consumption (P for interaction<0.05). When further stratified by PRS, fresh fruit intake with ≥4 servings/d was associated with risk of breast cancer [HR(95% CI):0.87(0.78-0.96)] in women with the highest quantile of PRS, and additive interaction was found between them.Table: 173PAssociations between diet and any breast cancer, by frequency of alcohol consumptionIn women took alcohol <1/dIn women took alcohol ≥1/dHR(95%CI)HR(95%CI)Processed meatNever1.00 (REF)1.00 (REF)<once/wk1.10(1.01-1.18)1.08(0.91-1.29)≥once/wk1.08(1.01-1.17)1.20(1.01-1.42)BeefNever1.00 (REF)1.00 (REF)<once/wk1.04(0.95-1.14)1.27(0.99-1.63)≥once/wk1.05(0.96-1.16)1.35(1.06-1.73)Fresh fruit<2 servings/d1.00 (REF)1.00 (REF)2.0-2.9 servings/d0.99(0.94-1.06)0.90(0.80-1.02)3.0-3.9 servings/d0.99(0.93-1.05)0.92(0.80-1.05)≥4 servings/d0.89(0.83-0.96)0.76(0.64-0.89) Open table in a new tab . Processed meat, vegetable and fresh fruit were associated with risk of breast cancer, and the effect was stronger in those who took alcohol ≥1/d and with high PRS for breast cancer. A combined intervention by reducing alcohol and processed meat consumption while increasing vegetable and fresh fruit intake might contribute to the prevention of breast cancer in high risk women.

81P Genetic association of ABCG2 polymorphisms on triple-negative breast cancer susceptibility and prognosis

81P Genetic association of ABCG2 polymorphisms on triple-negative breast cancer susceptibility and prognosis

Hypoxia-Inducible Factors-Based Single Nucleotide Polymorphism in Breast Cancer with More Cancer Susceptibility.

Hypoxia-inducible factors (HIFs) are a collection of transcriptional factors that engage in the regulation of oxygen homeostasis. They are hypoxia-responsive stress factors whose expression is linked to tumor growth and angiogenesis. HIF is a crucial player in the progression of breast cancer. Patients with high levels of hypoxia-inducible HIFs in their primary tumor biopsies had a higher chance of metastasis, the leading cause of breast cancer-related death. HIF polymorphisms have been shown in several epidemiological studies to influence breast cancer susceptibility. In the oxygendependent degradation domain, several short nucleotide polymorphisms (SNPs) of the HIF gene have been connected with higher HIF activity. To find SNP that make up the genetic diversity that underpins the phenotypic difference found between individuals in their susceptibility to cancer and the course of their disease, researchers used a variety of potential pathway-based approaches.

LncRNA-SNPs in a Brazilian Breast Cancer Cohort: A Case-Control Study.

Long noncoding RNAs (lncRNAs) are a class of non-coding RNAs that contain more than 200 nucleotides and exhibit a versatile regulatory capacity. Genomic alterations in lncRNAs have already been investigated in several complex diseases, including breast cancer (BC). BC is a highly heterogeneous disease and is the most prevalent cancer type among women worldwide. Single nucleotide polymorphisms (SNPs) in lncRNA regions appear to have an important role in BC susceptibility; however, little is known about lncRNA-SNPs in the Brazilian population. This study used Brazilian tumor samples to identify lncRNA-SNPs with a biological role in BC development. We applied a bioinformatic approach intersecting lncRNAs that are differentially expressed in BC tumor samples using The Cancer Genome Atlas (TCGA) cohort data and looked for lncRNAs with SNPs associated with BC in the Genome Wide Association Studies (GWAS) catalog. We highlight four lncRNA-SNPs-rs3803662, rs4415084, rs4784227, and rs7716600-which were genotyped in Brazilian BC samples in a case-control study. The SNPs rs4415084 and rs7716600 were associated with BC development at higher risk. These SNPs were also associated with progesterone status and lymph node status, respectively. The rs3803662/rs4784227 haplotype GT was associated with BC risk. These genomic alterations were also evaluated in light of the lncRNA's secondary structure and gain/loss of miRNA binding sites to better understand its biological functions. We emphasize that our bioinformatics approach could find lncRNA-SNPs with a potential biological role in BC development and that lncRNA-SNPs should be more deeply investigated in a highly heterogeneous disease population.

Advances in Electrochemical Biosensor Technologies for the Detection of Nucleic Acid Breast Cancer Biomarkers.

Breast cancer is the second leading cause of cancer deaths in women worldwide; therefore, there is an increased need for the discovery, development, optimization, and quantification of diagnostic biomarkers that can improve the disease diagnosis, prognosis, and therapeutic outcome. Circulating cell-free nucleic acids biomarkers such as microRNAs (miRNAs) and breast cancer susceptibility gene 1 (BRCA1) allow the characterization of the genetic features and screening breast cancer patients. Electrochemical biosensors offer excellent platforms for the detection of breast cancer biomarkers due to their high sensitivity and selectivity, low cost, use of small analyte volumes, and easy miniaturization. In this context, this article provides an exhaustive review concerning the electrochemical methods of characterization and quantification of different miRNAs and BRCA1 breast cancer biomarkers using electrochemical DNA biosensors based on the detection of hybridization events between a DNA or peptide nucleic acid probe and the target nucleic acid sequence. The fabrication approaches, the biosensors architectures, the signal amplification strategies, the detection techniques, and the key performance parameters, such as the linearity range and the limit of detection, were discussed.

A nomogram based on genotypic and clinicopathologic factors to predict the non-sentinel lymph node metastasis in Chinese women breast cancer patients.

Sentinel lymph node biopsy (SLNB) is the standard treatment for breast cancer patients with clinically negative axilla. However, axillary lymph node dissection (ALND) is still the standard care for sentinel lymph node (SLN) positive patients. Clinical data reveals about 40-75% of patients without non-sentinel lymph node (NSLN) metastasis after ALND. Unnecessary ALND increases the risk of complications and detracts from quality of life. In this study, we expect to develop a nomogram based on genotypic and clinicopathologic factors to predict the risk of NSLN metastasis in SLN-positive Chinese women breast cancer patients. This retrospective study collected data from 1,879 women breast cancer patients enrolled from multiple centers. Genotypic features contain 96 single nucleotide polymorphisms (SNPs) associated with breast cancer susceptibility, therapy and prognosis. SNP genotyping was identified by the quantitative PCR detection platform. The genetic features were divided into two clusters by the mutational stability. The normalized polygenic risk score (PRS) was used to evaluate the combined effect of each SNP cluster. Recursive feature elimination (RFE) based on linear discriminant analysis (LDA) was adopted to select the most useful predictive features, and RFE based on support vector machine (SVM) was used to reduce the number of SNPs. Multivariable logistic regression models (i.e., nomogram) were built for predicting NSLN metastasis. The predictive abilities of three types of model (based on only clinicopathologic information, the integrated clinicopathologic and all SNPs information, and integrated clinicopathologic and significant SNPs information) were compared. Internal and external validations were performed and the area under ROC curves (AUCs) as well as a series of evaluation indicators were assessed. 229 patients underwent SLNB followed by ALND and without any neo-adjuvant therapy, 79 among them (34%) had a positive axillary NSLN metastasis. The LDA-RFE identified the characteristics including lymphovascular invasion, number of positive SLNs, number of negative SLNs and two SNP clusters as significant predictors of NSLN metastasis. Furthermore, the SVM-RFE selected 29 significant SNPs in the prediction of NSLN metastasis. In internal validation, the median AUCs of the clinical and all SNPs combining model, the clinical and 29 significant SNPs combining model, and the clinical model were 0.837, 0.795 and 0.708 respectively. Meanwhile, in external validation, the AUCs of the three models were 0.817, 0.815 and 0.745 respectively. We present a new nomogram by combining genotypic and clinicopathologic factors to achieve higher sensitivity and specificity comparing with traditional clinicopathologic factors to predict NSLN metastasis in Chinese women breast cancer. It is recommended that more validations are required in prospective studies among different patient populations.

Increased prevalence of the founder BRCA1 c.5309G>T and recurrent BRCA2 c.1310_1313delAAGA mutations in breast cancer families from Northerstern region of Morocco: evidence of geographical specificity and high relevance for genetic counseling

BackgroundInherited mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 (BRCA1/2) confer high risks of breast and ovarian cancer. Because the contribution of BRCA1/2 germline mutations to BC in the Northeastern population of Morocco remains largely unknown, we conducted this first study to evaluate the prevalence and the phenotypic spectrum of two BRCA1/2 pathogenic mutations (the founder BRCA1 c.5309G>T and BRCA2 c.1310_1313delAAGA). This choice was also argued by the presence of an apparent specific geographical connection of these mutations and the Northeastern region of Morocco.MethodsScreening for the germline mutations c.5309G>T and BRCA2 c.1310_1313delAAGA was performed by sequencing on a total of 184 breast cancer (BC) patients originated from the Northeastern region of Morocco.The likelihood of identifying a BRCA mutation is calculated using the Eisinger scoring model. The clinical and pathologic features were compared between the BRCA-positive and BRCA-negative groups of patients. Difference in survival outcomes was compared between mutation carriers and non-carriers.ResultsBRCA1 c.5309G>T and BRCA2 c.1310_1313delAAGA are responsible for a significant proportion of all BC cases (12.5%) and at least 20% of familial BC. The screening of BRCA1/2 genes by NGS sequencing confirmed that there are no additional mutations detected among positive patients.The clinicopathological features in positive patients were in accordance with typical characteristics of BRCA pathogenic mutations. The mean features in the carriers were the early onset of the disease, familial history, triple negative status (for BRCA1 c.5309G>T) and worse prognosis in terms of overall surviving.Our study indicates that the Eisinger scoring model could be recommended to identify patients for referral to BRCA1/2 oncogenetic counseling.ConclusionOur findings suggest that BRCA1 c.5309G>T and BRCA2 c.1310_1313delAAGA mutations may have a strong founder and/or recurrent effect on breast cancer among the Northeastern Moroccan population. There contribution to breast cancer incidence is certainly substantial in this subgroup. Therefore, we believe that BRCA1 c.5309G>T and BRCA2 c.1310_1313delAAGA mutations have to be included in the array of tests aimed at revealing cancer syndrome carriers among subjects of Moroccan origin.

Detection of pathogenic variants in breast cancer susceptibility genes in bilateral breast cancer

PurposeTo investigate the frequency of germline pathogenic variants (PVs) in women with bilateral breast cancer.MethodsWe undertook BRCA1/2 and CHEK2 c.1100delC molecular analysis in 764 samples and a multigene panel in...

Triumphs and challenges in exploiting poly(ADP-ribose) polymerase inhibition to combat triple-negative breast cancer.

Poly(ADP-ribose) polymerase 1 (PARP1) regulates a myriad of DNA repair mechanisms to preserve genomic integrity following DNA damage. PARP inhibitors (PARPi) confer synthetic lethality in malignancies with a deficiency in the homologous recombination (HR) pathway. Patients with triple-negative breast cancer (TNBC) fail to respond to most targeted therapies because their tumors lack expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Certain patients with TNBC harbor mutations in HR mediators such as breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), enabling them to respond to PARPi. PARPi exploits the synthetic lethality of BRCA-mutant cells. However, de novo and acquired PARPi resistance frequently ensue. In this review, we discuss the roles of PARP in mediating DNA repair processes in breast epithelial cells, mechanisms of PARPi resistance in TNBC, and recent advances in the development of agents designed to overcome PARPi resistance in TNBC.

Abstract 5238: The functional role of promoter germline variants in breast cancer susceptibility genes

Abstract It is estimated that inherited deleterious or pathogenic germline variants in high- to moderate- penetrance breast cancer (BC) susceptibility genes such as BRCA1, BRCA2, STK11, CDH1, ATM, PALB2, and CHEK2 may explain up to 27% of the BC cases. For the remaining cases, BC develops as a result of the complex interaction between environmental and lifestyle risk factors as well as inherited familial predisposition. While low penetrance genetic variants have limited impact on BC risk when taken individually, their combined effect on polygenic risk scores may provide a risk elevated enough to justify clinical actions. Most of the previous work in hereditary breast cancer research has focused on variants located in the coding region of the genes and as a result, there is an abundance of information on the functional interpretation of such variants, while information on regulatory variants remains limited. The goal of this study was to assess the functional impact of germline variants in the promoter region of BC susceptibility genes on gene expression level. Genes evaluated include CDH1, STK11, and bidirectional promoter genes ATM/NPAT and PALB2/DCTN5. A bioinformatics approach was developed to identify and prioritize variants based on conservation level and predicted binding of transcription regulatory proteins. Selected variants will be introduced into pGL3 constructs harboring the promoter of interest using site-directed mutagenesis followed by transfection into HEK293T cells. Dual-glo luciferase expression assays are used to measure levels of promoter activities. Expression levels from promoters containing genetic variants are compared with those from constructs containing the reference sequence. The reference constructs for STK11 and CDH1 containing the genes complete promoters demonstrated functional activity. For bidirectional promoters, forwards and reverse construct were tested. Forward ATM/NPAT and PALB2/DCTN5 constructs showed luciferase expression under the influence of ATM and DCTN5 respectively. Work is on the way to assess promoter activity of the reverse complement sequence of those promoters and determine the impact of 13 candidate variants on the strength of these promoters. At the clinical level, identifying germline variants that contribute to BC risk could help better define BC risk in women with negative hereditary cancer genetic test results. Citation Format: Nelly Arlene Arroyo, Lenin J. Godoy, Julie Dutil. The functional role of promoter germline variants in breast cancer susceptibility genes. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5238.

Abstract SY17-01: The complexities of tumor associated macrophages and the key to effective targeting for anti-cancer therapy

Abstract Despite objective responses to poly(ADP-ribose) polymerase (PARP) inhibition and improvements in progression-free survival (PFS) compared to standard chemotherapy in patients with BRCA-associated triple-negative breast cancer (TNBC), benefits are transitory. Using high-dimensional single-cell profiling of human TNBC, here we demonstrate that macrophages are the predominant infiltrating immune cell type in breast cancer susceptibility (BRCA)-associated TNBC. Macrophages are an innate immune cell that play a critical role in host defense and maintaining tissue homeostasis, however their infiltration into tumors has been associated with disease progression and resistance to therapy. Tumor associated macrophages (TAMs) represent a significant proportion of solid tumors, including breast cancer. TAMs play a major role in tumorigenesis as they can enhance tumor cell growth, angiogenesis and metastasis. In addition, TAMs can inhibit anti-tumor responses of T cells. Our recent work has shown that removal or conversion of TAMs to an anti-tumor phenotype enhances chemo- and immuno-therapy establishing TAMs as targets for anti-cancer therapy. Through multi-omics profiling, we show that PARP inhibitors enhance both anti- and pro-tumor features of macrophages through glucose and lipid metabolic reprogramming, driven by the sterol regulatory element-binding protein 1 (SREBF1, SREBP1) pathway. Combining PARP inhibitor therapy with colony-stimulating factor 1 receptor (CSF1R)-blocking antibodies significantly enhanced innate and adaptive antitumor immunity and extended survival in mice with BRCA-deficient tumors in vivo, and this was mediated by CD8+ T cells. Collectively, our results uncover macrophage-mediated immune suppression as a liability of PARP inhibitor treatment and demonstrate that combined PARP inhibition and macrophage-targeting therapy induces a durable reprogramming of the tumor microenvironment (TME), thus constituting a promising therapeutic strategy for TNBC. Therefore, targeting TAMs offers great potential to enhance both chemo- and immuno-therapy. Deep analysis of TAMs in solid tumors has revealed the complexity of TAMs and revealed major gaps in our knowledge of the functional and phenotypic characterization of TAM subsets associated with cancer, before and after treatment. Here we will discuss the complexity of TAMs in solid tumors including characterizing TAM subsets, location, and crosstalk with neighboring cells, as well as novel TAM-modulating strategies and combinations that are likely to enhance current therapies and overcome chemo- and immuno-therapy resistance. Citation Format: Jennifer L. Guerriero. The complexities of tumor associated macrophages and the key to effective targeting for anti-cancer therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr SY17-01.

Abstract 6519: Haploinsufficiency for BRCA2 leads to common fragile site instability in human mammary epithelial cells

Abstract Individuals with germline heterozygous mutations of breast cancer susceptibility genes BRCA1 or BRCA2 have a 50 to 80% lifetime risk of developing breast cancer, yet the mechanisms of these cancers remain largely unknown. There is growing evidence that BRCA1 and BRCA2 heterozygosity confer haploinsufficiency in normal human mammary epithelial cells for their multiple known functions. Haploinsufficiency for BRCA1 leads to defects in differentiation, replication stress response, premature senescence and genomic instability in human mammary epithelial cells. Deficiencies in error-free DNA damage repair has been observed in genetically engineered cells as well as primary human mammary epithelial cells carrying BRCA1 heterozygous mutations. There is relatively less research on understanding the role of haploinsufficiency for BRCA2 in human mammary epithelial cells. It has been reported that haploinsufficiency for BRCA2 leads to genomic instability via unscheduled R-loops. We previously showed that accumulation of sub-chromosomal copy number variations (CNVs) and replication stress-induced DNA damage, together with attenuated checkpoint and apoptotic responses, constitute a haplo-insufficient phenotype in mammary epithelial cells of BRCA2 mutation carrier patients. Common fragile sites (CFS) are found in all individuals and represent a normal component of chromosome structure. Numerous studies have shown that CFSs are prone to deletions and rearrangements in many cancers, a situation referred as CFS instability. Importantly, Fanconi Anemia/BRCA pathway has been previously reported to have a role in regulating CFS instability. In this study, we further explored a link between BRCA2 haploinsufficiency and CFS instability. We induced replication stress with DNA polymerase inhibitor aphidicolin (APH) treatment in control and BRCA2- deficient human mammary epithelial cells. We then performed DAPI banding to map and score the cytogenic lesions in metaphase spreads cells, in the absence or presence of APH treatment. Our results demonstrated that BRCA2- deficient human mammary epithelial cells showed increased frequency of CFS regions such as FRA18B. Correspondingly, BRCA2-deficient cells exhibited a failure to activate CHK1, a central coordinator of the response to replication stress and DNA damage, in response to APH treatment, despite normal levels of total CHK1 protein. ATR/CHK1 pathway is a major regulator of CFS stability. Thus, our results provide support for BRCA2 haploinsufficiency leading to CFS instability in human mammary epithelial cells. These studies will yield unanticipated opportunities for improved risk assessment and prevention strategies in high-risk patients. Citation Format: Mihriban Karaayvaz, Kavya Vipparthi, Antony Caputo. Haploinsufficiency for BRCA2 leads to common fragile site instability in human mammary epithelial cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6519.