BRCA1 Research Articles

Methyl CpG binding protein MBD2 has a regulatory role on the BRCA1 gene expression and its modulation by resveratrol in ER+, PR+ & triple-negative breast cancer cells

BackgroundResveratrol has demonstrated its ability to regulate BRCA1 gene expression in breast cancer cells, and previous studies have established the binding of MBD proteins to BRCA1 gene promoter regions. However, the molecular mechanism underlying these interactions remains to be elucidated. The aimed to evaluate the impact of MBD proteins on the regulation of BRCA1, BRCA2, and p16 genes and their consequential effects on breast cancer cells.MethodsEfficacy of resveratrol was assessed using the MTT assay. Binding interactions were investigated through EMSA, ChIP, & MeIP assay. Expression analyses of MBD genes and proteins were conducted using qRT-PCR and western blotting, respectively. Functional assays, including clonogenic, migratory, and sphere formation assays were used to assess cancer cells’ colony-forming, metastatic, and tumor-forming abilities. The cytotoxicity of resveratrol on cancer cells was also tested using an apoptosis assay.ResultsThe study determined an IC50 of 30µM for resveratrol. MBD proteins were found to bind to the BRCA1 gene promoter. Resveratrol exhibited regulatory effects on MBD gene expression, subsequently impacting BRCA1 gene expression and protein levels. Higher concentrations of resveratrol resulted in reduced colony and sphere formation, decreases migration of cancer cells, and an increases number of apoptotic cells in breast cancer cells.ImpactIdentification of MBD2-BRCA1 axis indicates their significant role in the induction of apoptosis and reduction of metastasis and proliferation in breast cancer cells. Further therapy can be designed to target these MBD proteins and resveratrol could be used along with other anticancer drugs to target breast cancer.ConclusionsIn conclusion MBD2 protein interact to the BRCA1 gene promoter, and resveratrol modulates MBD2 gene expression, which in turn regulates BRCA1 gene expression, and inhibits cell proliferation, migration, and induces apoptosis in ER+, PR+ & Triple negative breast cancer cells.

Abstract PO2-10-12: The devil is in the details: Workflow analysis of breast cancer treatment decision making and implications for decision support design

Abstract While numerous decision aids have been developed to support treatment decision-making in breast cancer1, widespread implementation remains limited due to challenges integrating these tools in clinical workflows2. Given these persistent issues, we need to better understand the complex workflows and needs of decision aid users - patients, their family caregivers, and breast cancer clinicians. Previous studies have explored various aspects of breast cancer team workflows3,4. Despite this work, it is still unclear how these complex workflows support or hinder decision aid use. In this study, we conducted an in-depth analysis of breast cancer team workflow to elicit design requirements for informatics tools to support patient-centered decision-making. This study was part of a larger project aimed at designing a COMputeried PAtient-centered Collaborative Technology (COMPACT) to support personalized decision-making for breast cancer patients. We conducted observations of clinicians and patients at one breast center, using a tablet computer with smart pen to take notes on all aspects of clinic workflow. We uploaded all observation notes into a qualitative data analysis software, Dedoose. Two researchers coded the observations in an inductive, consensus-based process. We met to review our codes and identify key themes emerging in the data. We observed 95 hours and 127 patient encounters across 20 clinician-centered and 8 patient-centered observations. We identified 10 themes related to the design of decision support, which we grouped into the 4 components of workflow6 (see Table 1). We identified numerous patient-specific factors communicated from the patient to the clinical team that influenced treatment decision-making. These “decision factors” covered the broader scope of the patient’s life that was important in the decision-making process (e.g., upcoming family wedding, work). Patients were frequently “knowledge brokers” and were asked to remember and relay information across members of the care team. We identified 28 different tools and technologies used to support treatment decision-making. Patient family caregivers (e.g., aunt, husband) played an important role in treatment decision-making. Based on these findings, we developed design requirements for informatics tools to better support patients (and clinicians). Our study highlights the complexity and interdependence of breast cancer treatment decision-making. Patients frequently made treatment decisions that influenced subsequent decisions. Decision aids typically focus on one decision or one care specialty and do not support consideration of several treatment options at one time1. Future research is needed to determine if and how decision support tools could incorporate the broader scope and interdependence between decisions to support patient-centered care. We highlight the need for informatics tools to consider the diverse and unique decision factors (e.g., hobbies) that are crucial to patient-centered decision-making. Decision support could help to elicit and incorporate these factors during treatment decision-making. However, the variable nature of these patient-specific factors presents a challenge to decision support design. Further research is needed to determine how to optimally incorporate such factors into decision support tools. We found inadequate system support for clinicians’ tasks including limited feedback loops to notify clinicians of completed tasks (e.g., mammogram, genetic testing). As a result, patients were often responsible for relaying information to and between different members of the clinical team. Given that patients only remember 50% of what clinicians tell them during visits7, a better system is needed to improve the reliability of information transfer. Our design guidelines can be used to improve the design of decision support tools and ultimately improve patient-centered decision-making. Table 1. Workflow components, themes, and associated challenges to decision support design Citation Format: Megan Salwei, Carrie Reale. The devil is in the details: Workflow analysis of breast cancer treatment decision making and implications for decision support design [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-10-12.

Abstract PO5-15-01: Prospective Biomarker Assessment of Cardiotoxicity Among Ethnically Diverse Women with Early Breast Cancer

Abstract Background: Approximately 4.1 million women in the United States are living with breast cancer1. Cardiac dysfunction is a significant adverse effect of commonly used breast cancer therapies like doxorubicin (D) and trastuzumab (T). The cardiotoxicity (CTox) associated with these agents manifests as a reduction in left ventricular ejection fraction (LVEF) with or without signs and symptoms of heart failure. Purpose: The objective of this study is to evaluate serum cardiac and inflammatory biomarkers over time and their association with CTox development. Methods: A total of 133 newly diagnosed stage I-III invasive breast cancer patients were enrolled in a prospective clinical trial (2013-2017) and received standard of care T and/or D based systemic therapy. They underwent serial echocardiograms every 6 months for two years and then based on clinical need for a total of six years. CTox was defined as a >10% drop in LVEF, and/or LVEF < 50%. Biomarker data was collected at baseline, 12 and 24 months and included both cardiac biomarkers (Troponin-I, TN-I and amino terminal B-type natriuretic peptide, NT-proBNP) and measures of inflammation (C-reactive protein, CRP). Of the 32 with CTox patients, 15 had adequate serum samples and were matched with 15 patients without CTox (N=30), controlling for age, race, and treatment regimen prior to serum sample analysis. Results: The mean LVEF at baseline was similar between CTox and non-CTox patients (64% vs 62%, p=0.342). However, over the course of 12 and 24 months, CTox patients experienced a statistically significant decrease in LVEF compared to their baseline values (55% and 56%, respectively, p < 0.001). At baseline, CTox patients had higher CRP levels compared to non-CTox (13.4 mg/L vs 3.35 mg/L), however this difference did not reach statistical significance (P >0.05). Although this difference seemed to narrow at 12 months (3.88 mg/L vs 1.52 mg/L, p< 0.05) and 24 months (6.85 mg/L vs 2.36 mg/L, p< 0.05), CTox patients consistently had higher mean CRP levels. Mean TN-I levels increased at both 12 and 24 months compared to baseline (CTox 1.13 ng/L, 7.13 ng/L, 4.13 ng/L vs non-CTox 0.800 ng/L, 8.13 ng/L, 4.60 ng/L, p< 0.05) but there were no significant differences between the two groups (p >0.05). While baseline NT-proBNP levels did not differ significantly between the CTox and non-CTox patients, there were statistically significant increases in CTox patients at 12 and 24 months (205 pg/mL vs 74 pg/mL, and 200 pg/mL vs 96 pg/mL, p < 0.01, respectively). Conclusion: In a well characterized, diverse, matched subset of patients with early breast cancer who were prospectively followed with serial echocardiograms, distinct biomarker patterns were observed. Measures of inflammation (CRP) at baseline were different and these changes appeared to diminish over time. While the cardiac biomarker TN-I appeared to increase in both +CTox and -CTox group over time, only those with differential NT-proBNP elevations were associated with cardiotoxicity. 1Lisa Gallicchio, PhD and others, Estimation of the Number of Individuals Living With Metastatic Cancer in the United States, JNCI: Journal of the National Cancer Institute, Volume 114, Issue 11, November 2022, Pages 1476–1483 Citation Format: Shahzaad Jahangier, Rubina Qamar, Maharaj Singh, Vinay Thohan, James Weese, Bijoy Khandheria, Anna Kamke-Jordan. Prospective Biomarker Assessment of Cardiotoxicity Among Ethnically Diverse Women with Early Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-15-01.

Abstract PO4-09-11: Predictors of Cardiotoxicity in Early Breast Cancer Patients Treated with Doxorubicin and/or Trastuzumab: Implications of Race/Ethnicity and Insurance Status

Abstract Predictors of Cardiotoxicity in Early Breast Cancer Patients Treated with Doxorubicin and/or Trastuzumab: Implications of Race/Ethnicity and Insurance Status Shahzaad K Jahangier, MD, Yunqi Liao, MS, Maharaj Singh, PhD, James Weese, MD, Bijoy Khandheria, MD, Anna Kamke-Jordan MS, Vinay Thohan, MD, Rubina Qamar, MD Background: Approximately 4.1 million women in the United States are living with breast cancer1. Cardiac dysfunction is a significant adverse effect of commonly used breast cancer therapies like doxorubicin (D) and trastuzumab (T). The cardiotoxicity (CTox) associated with these agents manifests as a reduction in left ventricular ejection fraction (LVEF) with or without signs and symptoms of heart failure. Purpose: The objective of this study is to identify high-risk populations susceptible to developing CTox, with a focus on identifying individuals who could potentially benefit from the early initiation of empiric cardioprotective therapies. Methods: We investigated the relationship of race/ethnicity, insurance status, treatment regimen and comorbidities including hypertension (HTN), hyperlipidemia (HLD), diabetes mellitus (DM), tobacco use, BMI, age, and radiation therapy on the development of CTox from D and/or T. A total of 133 newly diagnosed stage I-III invasive breast cancer patients were enrolled in a prospective clinical trial (2013-2017) and received standard of care D and/or T based systemic therapy. Echocardiogram data was collected every 6 months for two years and then based on clinical need for a total of six years. CTox was defined as a >10% drop in LVEF, and/or LVEF < 50%. Results: Our study included a population of 133 patients comprising Black (22%), White (77%), and Hispanic (1.5%) individuals. Among these patients, 32 developed CTox (Black 41%, White 19%, Hispanic 50%). Of all patients, 29% had State insurance while 71% had Private insurance. Prevalence rates for comorbidities were as follows: HTN (41%), HLD (32%), DM (13%), and tobacco use (36%). In a univariate logistic regression model, race/ethnicity, HTN, insurance status, and tobacco use were most strongly associated with Ctox. When controlling for tobacco use and HTN, race/ethnicity was not significantly associated with Ctox. However, direct comparisons of levels of race/ethnicity showed that Black patients were more likely to develop Ctox when compared to White patients (OR 2.60, 95% CI = 1.01-6.65, P = 0.045). HTN patients were also more likely to develop Ctox, when controlling for ethnicity and tobacco use (OR 2.62, 95% CI = 1.10-6.43, P = 0.031). In a separate multivariate analysis, we examined insurance as a surrogate for socioeconomic status. Having State compared to Private insurance was associated with an increased risk of developing CTox when controlling for race/ethnicity and HTN (OR 3.73, 95% CI = 1.47-9.58, P = 0.006). Furthermore, in all models, HLD, DM, BMI, age, and radiation field were not found to be significantly associated with increased CTox. Conclusion: In our well characterized population of patients with stage I-III breast cancer, who were prospectively followed and received standard of care systemic therapy, we observed an association between insurance status with increased risk of CTox from treatment regimen. 1Lisa Gallicchio, PhD and others, Estimation of the Number of Individuals Living With Metastatic Cancer in the United States, JNCI: Journal of the National Cancer Institute, Volume 114, Issue 11, November 2022, Pages 1476–1483 Citation Format: Shahzaad Jahangier, Rubina Qamar, Vinay Thohan, Maharaj Singh, Yunqi Liao, James Weese, Bijoy Khandheria, Anna Kamke-Jordan. Predictors of Cardiotoxicity in Early Breast Cancer Patients Treated with Doxorubicin and/or Trastuzumab: Implications of Race/Ethnicity and Insurance Status [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-09-11.

Abstract PO2-04-13: TWT-203: PHASE 1b/2 STUDY OF CFI-402257 AS MONOTHERAPY IN ADVANCED SOLID TUMORS AND IN COMBINATION WITH FULVESTRANT IN PATIENTS WITH ER+/HER2- ADVANCED BREAST CANCER AFTER PROGRESSION ON PRIOR CDK4/6 INHIBITORS AND ENDOCRINE THERAPY

Abstract Background: TTK (Threonine Tyrosine Kinase also known as Monopolar spindle 1), is a dual-specificity serine-threonine kinase critical for anaphase promoting complex inhibition at the spindle assembly checkpoint and is required for chromosome alignment and error correction. TTK inhibition results in premature mitosis exiting with unattached chromosomes potentially leading to aneuploidy and cell death. High TTK tumor levels correlate with worse prognosis and contribute to the survival and proliferation of aneuploid cells. CFI-402257, a potent and selective inhibitor of TTK, inhibits the growth of a variety of human cancer-derived cell lines. A first-in-human phase 1 study of CFI-402257 (NCT02792465) demonstrated a tolerable safety profile when enrolled as a monotherapy in solid tumors, and in combination with fulvestrant in hormone receptor positive, HER2 negative (HR+/HER2-) breast cancer1. The dose for expansion was 168 mg, dose limiting toxicity was dose-dependent neutropenia which was manageable and reversible. Investigator-confirmed partial responses (cPR) were observed in 5 pts (8%) with 32 (50.8%) exhibiting disease control. In the HR+/HER2- breast cancer population previously treated with cyclin dependent kinase 4/6 inhibitors (CDK4/6i) and aromatase inhibitors (N=25), there were 4 cPR’s with a median duration of response of 223 days, with responses emerging after 2 cycles of therapy. Responses were observed with CFI-402257 as a single agent and in combination with fulvestrant. Based on these data, study TWT-203 will focus on advanced solid tumors for dose confirmation then focus on advanced HR+/HER2- breast cancers in combination with an approved endocrine therapy. Methods: In TWT-203 study, safety and clinical activity of CFI-402257 monotherapy will be evaluated in patients (pts) with advanced solid tumors (Part A) or in combination with fulvestrant in pts with HR+/HER2- advanced breast cancer (Part B). Part A will confirm the RP2D using a 3+3 design with a starting dose of 126 mg daily. Part B evaluates CFI-402257 in combination with fulvestrant in pts with HR+/HER2- advanced breast cancer following progression on prior CDK4/6i and endocrine therapy. Efficacy endpoints include overall response rate and disease control rate. Safety endpoints include incidence of treatment emergent adverse events. Exploratory objectives include characterization of protein and molecular alterations relevant to the cell cycle and CFI-402257 response. Results: At data cutoff of 11 May 2023, 14 pts were enrolled. All received monotherapy treatment. Median treatment duration was 2.1 months (range, 0.2-7.3+). Median age was 67 years (57-76). Median number of prior regimens was 3.5 (2-12). Tumor types enrolled were colorectal (n=6, 43%), breast (3, 21%), and endometrial, hepatocellular, leiomyosarcoma, pancreatic, and sarcoma (1 each, 7%). 4 dose levels, from 126 to 252 mg, were studied. Most pts (12, 86%) experienced ≥1 treatment emergent adverse event (TEAE). More than half of pts (8, 57%) experienced ≥1 treatment related TEAE. Most common TEAEs were fatigue (5, 36%) and nausea (4, 29%). 5 pts (36%) experienced TEAEs grade ≥3, most common were fatigue, neutrophil count decrease, white blood cell count decrease (2 pts each, 14.3%). 1 pt (7%) experienced a serious adverse event (hematuria), not related to study therapy. No patients discontinued treatment due to TEAE. All pts who ended treatment were due to disease progression (8, 57%). No grade 5 TEAEs occurred. No dose limiting toxicities were reported. Disease control rate (CR, PR, or SD ≥ 6 weeks from baseline) was 54.5% (6 pts/11): all achieved SD. 3 of the 6 pts remain on study. Conclusion: CFI-402257 is a potent inhibitor of TTK. It is well tolerated with manageable TEAEs, no dose limiting or treatment limiting toxicities, and no treatment related deaths. Dose expansion in the patient population of interest will commence. 1. John Hilton et al. Cancer Res 2023;83(5 Suppl): P6-10-13. Citation Format: Justin Call, Muralidhar Beeram, Alexander I. Spira, Mark Bray, Dih-Yih Chen, Long Kwei, Emily Roberts-Thomson, Trisha Denny, Roger Sidhu, Robert Wesolowski. TWT-203: PHASE 1b/2 STUDY OF CFI-402257 AS MONOTHERAPY IN ADVANCED SOLID TUMORS AND IN COMBINATION WITH FULVESTRANT IN PATIENTS WITH ER+/HER2- ADVANCED BREAST CANCER AFTER PROGRESSION ON PRIOR CDK4/6 INHIBITORS AND ENDOCRINE THERAPY [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-04-13.

Abstract PO5-06-04: EMSY amplification co-occurs with FGF/FGFR axis amplification in Metastatic Breast Cancer

Abstract Background: Amplification of FGFR and its ligands play an important role in breast cancer onset and progression and mutations of this signaling axis are emerging as mechanisms of resistance to targeted treatments. Understanding the molecular landscape of tumors that harbor aberrations in the FGF/FGFR (FGF/R) axis may help define the biology of these tumors and lead to the development of novel personalized approaches for more effective treatments in this group of patients. Using publicly available datasets, this study aimed at identifying genomic alterations co-occurring with amplification (amp) of the FGF/R axis in Metastatic Breast Cancer (mBC) patients. Methods: We utilized data from three cohorts of mBC patients. The first cohort (c1) included 176 patients with mBC from an ongoing precision medicine program sponsored by the Side-Out Foundation where genomic testing was performed, using a targeted gene panel, in real-world settings by commercial labs based predominantly on tumor specimens collected between 2019 and 2023. Whole exome sequencing data was obtained from AACR Genomics Evidence Neoplasia Information Exchange (GENIE) to establish a second cohort (c2) of 301 patients and a third cohort (c3) of 216 patients with mBC. Lastly, we included a fourth cohort (c4, n=122) of patients with early breast cancer (eBC). Chi2 test and Fisher’s Exact test were used to find significant co-occurring events. Python, pandas, and shell scripting were used for data manipulation, analysis and performing statistical tests. Results: Alterations of the FGF/R axis occurred in 26% (n=46) of patients in c1 of which 76% (n=35) were HR+ tumors and 24% (n=11) were Triple Negative Breast Cancers. Specifically, we detected amp of FGF3 (n=24, 52%), FGF4 (n=23, 50%), FGF19 (n=17, 37%), FGFR1 (n=18, 39%). In patients with alteration of the FGF/R axis, the most frequent aberrations were CCND1 (n=22, 48%), ZNF703 (n=12, 26%), MYC (n=9, 20%), and EMSY (n=8, 17%) amp, along with mutations of PIK3CA (n=17, 37%) and TP53 (n=18, 39%). EMSY amp was found in none of the patients without alterations of the FGF/R axis and co-amplified with the FGF/R axis in 8 patients(100%) (p< 0.0001). Similar results were also detected in the two independent cohorts of patients retrieved from the GENIE database. In c2, co-amp of EMSY and FGF/R axis was found in 53 of the 56 patients (95%) harboring EMSY amp (p< 0.0001). In c3, 17 patients (89%) had co-amp of EMSY and FGF/R axis of the 19 patients with EMSY amp (p< 0.0001). However, when we looked at patients with eBC in c4, of the 10 patients with EMSY amp, 7 patients (70%) had co-amp of EMSY and FGF/R axis and this association was not significant (p = 0.09). Conclusion: Amplification of EMSY has been mostly reported in ovarian (~17%) and sporadic breast cancers (~13%). EMSY has been reported to behave as an oncogene and a transcriptional repressor. It is well known that it can interact with the BRCA2 protein and potentially contributes to the “BRCAness” of tumors harboring its amp. Studies have also suggested that EMSY may act as a transcriptional repressor that modulates the expression of antimetastatic microRNAs in breast cancer. In the three mBC cohorts included in this analysis, EMSY amp was detected in 8, 56, and 19 cases, respectively. However, when the analysis was restricted to tumors harboring amps of both EMSY and FGF/R axis, EMSY was amplified in 100%, 95%, and 89% of those cases. While co-amplification of the EMSY gene with members of the FGF/R axis may be explained by its close proximity to the FGF3/4/19, and CCND1 genes on chromosome 11, in our analysis these co-amplifications were significant only in patients with metastatic disease. As dissecting the complex molecular landscape of mBC continues to be an essential step for advancing personalized treatment and better patient care, understanding the phenotypic effects of these co-amplifications may provide unique opportunities for devising combinatorial treatments for these patients. Citation Format: Deepika Prasad, Edik Blais, Rick Dunetz, Emanuel Petricoin, Mariaelena Pierobon. EMSY amplification co-occurs with FGF/FGFR axis amplification in Metastatic Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-06-04.

Evidence for persistent UV-induced DNA damage and altered DNA damage response in xeroderma pigmentosa patient corneas

Xeroderma pigmentosum (XP) is a rare genetic disorder characterized by injury to the ocular surface due to exposure to ultraviolet (UV) radiation. UV-induced damage in the cells leads to the formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 pyrimidine-pyrimidone photoproducts that are repaired by the NER (Nucleotide Excision Repair) pathway. Mutations in the genes coding for NER proteins, as reported in XP patients, would lead to sub-optimal damage repair resulting in clinical signs varying from photo-keratitis to cancerous lesions on the ocular surface. Here, we aimed to provide evidence for the accumulation of DNA damage and activation of DNA repair pathway proteins in the corneal cells of patients with XP. Corneal buttons of patients who underwent penetrating keratoplasty were stained to quantify DNA damage and the presence of activated DNA damage response proteins (DDR) using specific antibodies. Positive staining for pH2A.X and thymidine dimers confirmed the presence of DNA damage in the corneal cells. Positive cells were found in both control corneas and XP samples however, unlike normal tissues, positive cells were found in all cell layers of XP samples indicating that these cells were sensitive to very low levels of UV. pH2A.X-positive cells were significantly more in XP corneas (p < 0.05) indicating the presence of double strand breaks in these tissues. A positive expression of phosphorylated-forms of DDR proteins was noted in XP corneas (unlike controls) such as ataxia telangiectasia mutated/Rad-3 related proteins (ATM/ATR), breast cancer-1 and checkpoint kinases-1 and -2. Nuclear localization of XPA was noted in XP samples which co-localized (calculated using Pearson's correlation) with pATM (0.9 ± 0.007) and pATR (0.6 ± 0.053). The increased presence of these in the nucleus confirms that unresolved DNA damage was accumulating in these cells thereby leading to prolonged activation of the damage response proteins. An increase in pp53 and TUNEL positive cells in the XP corneas indicated cell death likely driven by the p53 pathway. For comparison, cultured normal corneal epithelial cells were exposed to UV-radiation and stained for DDR proteins at 3, 6 and 24 h after irradiation to quantify the time taken by cells with intact DDR pathway to repair damage. These cells, when exposed to UV showed nuclear translocation of DDR proteins at 3 and 6 h which reduced significantly by 24 h confirming that the damaged DNA was being actively repaired leading to cell survival. The persistent presence of the DDR proteins in XP corneas indicates that damage is being actively recognized and DNA replication is stalled, thereby causing accumulation of damaged DNA leading to cell death, which would explain the cancer incidence and cell loss reported in these patients.

The PARTNER trial of neoadjuvant olaparib with chemotherapy in triple-negative breast cancer

PARTNER is a prospective, phase II–III, randomized controlled clinical trial that recruited patients with triple-negative breast cancer1,2, who were germline BRCA1 and BRCA2 wild type3. Here we report the results of the trial. Patients (n = 559) were randomized on a 1:1 basis to receive neoadjuvant carboplatin–paclitaxel with or without 150 mg olaparib twice daily, on days 3 to 14, of each of four cycles (gap schedule olaparib, research arm) followed by three cycles of anthracycline-based chemotherapy before surgery. The primary end point was pathologic complete response (pCR)4, and secondary end points included event-free survival (EFS) and overall survival (OS)5. pCR was achieved in 51% of patients in the research arm and 52% in the control arm (P = 0.753). Estimated EFS at 36 months in the research and control arms was 80% and 79% (log-rank P > 0.9), respectively; OS was 90% and 87.2% (log-rank P = 0.8), respectively. In patients with pCR, estimated EFS at 36 months was 90%, and in those with non-pCR it was 70% (log-rank P < 0.001), and OS was 96% and 83% (log-rank P < 0.001), respectively. Neoadjuvant olaparib did not improve pCR rates, EFS or OS when added to carboplatin–paclitaxel and anthracycline-based chemotherapy in patients with triple-negative breast cancer who were germline BRCA1 and BRCA2 wild type. ClinicalTrials.gov ID: NCT03150576.

Abstract LB158: Synergistic cytotoxicity of histone deacetylase and poly-ADP ribose polymerase inhibitors and decitabine in pancreatic cancer cells: implications for novel therapy

Abstract Histone deacetylase inhibitors (HDACi) can modulate the acetylation status of proteins, influencing the genomic instability exhibited by cancer cells. Poly (ADP ribose) polymerase (PARP) inhibitors (PARPi) have a direct effect on protein poly (ADP-ribosyl)ation, which is important for DNA repair. Decitabine is a nucleoside cytidine analogue, which when phosphorylated gets incorporated into the growing DNA strand, inhibiting methylation and inducing DNA damage by inactivating and trapping DNA methyltransferase on the DNA, thereby activating transcriptionally silenced DNA loci. We explored various combinations of HDACi and PARPi +/- decitabine (hypomethylating agent) in pancreatic cancer cell lines BxPC-3 and PL45 (wild-type BRCA1 and BRCA2) and Capan-1 (mutated BRCA2). Colony formation and drug-mediated inhibition of cell proliferation in pancreatic cancer cell lines and comparison of the effects of each drug combination with the effect of the individual drugs are shown in Table. The combination of HDACi (panobinostat or vorinostat) with PARPi (talazoparib or olaparib) resulted in synergistic cytotoxicity in all cell lines tested. The addition of decitabine further increased the synergistic cytotoxicity noted with HDACi and PARPi, triggering apoptosis (evidenced by increased cleavage of caspase 3 and PARP1). The 3-drug combination treatments (vorinostat, talazoparib, and decitabine; vorinostat, olaparib, and decitabine; panobinostat, talazoparib, and decitabine; panobinostat, olaparib, and decitabine) induced more DNA damage (increased phosphorylation of histone 2AX) than the individual drugs and impaired the DNA repair pathways (decreased levels of ATM, BRCA1, and ATRX proteins). The 3-drug combinations also altered the epigenetic regulation of gene expression (NuRD complex subunits, reduced levels). This is the first study to demonstrate synergistic interactions between the aforementioned agents in pancreatic cancer cell lines and provides preclinical data to design individualized therapeutic approaches with the potential to improve pancreatic cancer treatment outcomes. Table. Colony formation and drug-mediated inhibition of cell proliferation in pancreatic cancer cell lines. Comparison of the effects of each drug combination with the effect of the individual drugs (Table shows the p-values for each comparison.) Colony formation BxPC-3 PL45 Capan-1 Pano SAHA TLZ Ola DAC Pano SAHA TLZ Ola DAC Pano SAHA TLZ Ola DAC Pano+TLZ 0.00048 0.0052 2.40E-06 2.70E-06 0.0051 0.021 Pano+Ola 0.0035 0.078 0.0011 0.00094 0.0016 0.022 SAHA+TLZ 1.80E-05 0.17 0.0029 0.012 0.0014 0.019 SAHA+Ola 0.00018 0.014 0.0016 0.0068 0.0066 0.029 Pano+TLZ+DAC 4.20E-05 0.00026 0.0015 1.70E-05 1.20E-05 2.70E-06 0.00052 0.00088 0.0064 Pano+Ola+DAC 3.40E-05 0.00049 0.0013 7.10E-07 1.70E-06 2.20E-06 0.00068 0.0028 0.0053 SAHA+TLZ+DAC 0.00016 0.00016 0.0011 1.90E-05 3.70E-06 9.30E-07 0.00018 0.00017 0.011 SAHA+Ola+DAC 4.90E-07 0.00035 0.001 0.00022 0.00026 0.00084 0.00016 0.0016 0.0035 Drug-mediated inhibition of cell proliferation Pano+TLZ+DAC 3.57E-05 3.89E-07 1.30E-07 2.91E-05 3.76E-06 1.80E-08 0.0239 ND 0.0092 Pano+Ola+DAC 7.76E-05 1.43E-07 2.52E-07 6.59E-07 1.03E-08 2.22E-07 0.0013 0.21 0.0034 SAHA+TLZ+DAC 3.04E-06 0.00034 1.17E-05 4.91E-08 4.45E-06 1.74E-07 0.0013 1.75E-01 0.007 SAHA+Ola+DAC 0.00012 0.0032 0.000068 9.64E-09 1.53E-08 9.35E-07 0.0007 0.18 0.0054 Abbreviations: DAC: decitabine; ND: not determined; Ola: olaparib; Pano: panobinostat; SAHA: vorinostat; TLZ: talazoparib P ≤ 0.05 is considered statistically significant. Citation Format: Apostolia M. Tsimberidou, Benigno C. Valdez, Bin Yuan, Yago Nieto, Mehmet Baysal, Abhijit Chakraborty, Borje S. Andersson. Synergistic cytotoxicity of histone deacetylase and poly-ADP ribose polymerase inhibitors and decitabine in pancreatic cancer cells: implications for novel therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB158.

A glycolytic metabolite bypasses “two-hit” tumor suppression by BRCA2

Knudson's "two-hit" paradigm posits that carcinogenesis requires inactivation of both copies of an autosomal tumor suppressor gene. Here, we report that the glycolytic metabolite methylglyoxal (MGO) transiently bypasses Knudson's paradigm by inactivating the breast cancer suppressor protein BRCA2 to elicit a cancer-associated, mutational single-base substitution (SBS) signature in nonmalignant mammary cells or patient-derived organoids. Germline monoallelic BRCA2 mutations predispose to these changes. An analogous SBS signature, again without biallelic BRCA2 inactivation, accompanies MGO accumulation and DNA damage in Kras-driven, Brca2-mutant murine pancreatic cancers and human breast cancers. MGO triggers BRCA2 proteolysis, temporarily disabling BRCA2's tumor suppressive functions in DNA repair and replication, causing functional haploinsufficiency. Intermittent MGO exposure incites episodic SBS mutations without permanent BRCA2 inactivation. Thus, a metabolic mechanism wherein MGO-induced BRCA2 haploinsufficiency transiently bypasses Knudson's two-hit requirement could link glycolysis activation by oncogenes, metabolic disorders, or dietary challenges to mutational signatures implicated in cancer evolution.

Abstract 6256: Prevalence of BRCA1 and BRCA2 proteins in breast cancer in a nigerian population and their relationship with different breast cancer morphological variants

Abstract Background: Breast cancer is the commonest site specific cancer in women and a leading cause of cancer death among women in Nigeria and globally. The trend in Nigeria and Africa is that breast cancers are seen in younger age groups, are of higher grades and follow an aggressive course. It has been suggested that this may largely be due to mutation in BRCA genes with the attendant alteration in function of its proteins. This study aimed at determining the prevalence of BRCA1 and BRCA2 proteins in breast cancers seen in our environment as well as to see any association between these proteins and different morphological variants. Materials and Methods: A descriptive study using tissue blocks of all histologically diagnosed breast cancer in our department between 2013 and 2017. Fresh sections were recut for histological grading and immunohistochemistry. Proteintech BRCA1 and BRCA2 polyclonal antibodies and detection kit were used. Results: One hundred and thirty (130) cases met the inclusion criteria for this study. The mean (SD) age of the patients was 44.8 (10.3) years with ages ranging from 26 to 79 years. There were more cases of breast cancer (73.1%) seen before 50 years. Two (2) Male Breast Cancer (MBC) cases were seen, giving the female to male ratio of 64:1. The commonest morphological variant encountered was Invasive Carcinoma, No Special Type at 84.6% of cases. This was followed by invasive medullary (7.8%). The least common variant was papillary cancer at 0.8%. The tumors seen were mostly grade 3 (71.2%), followed by grade 2 at 22.7% and the least was grade 1 at 6.1%. Positivity for BRCA1 and BRCA2 proteins was seen in 27.7% and 30.0% of cases respectively. One of the MBC showed reactivity for BRCA1 protein. No significant relationship was seen between BRCA 1/2 proteins expression and age or breast cancer histotypes. Conclusion: BRCA 1 and 2 proteins are an important risk factor for breast cancers seen in this environment. However, there is no association with age distribution and morphological variants of the breast cancer in our population. Citation Format: Solomon Raphael, Abdul Oluwasesan. Prevalence of BRCA1 and BRCA2 proteins in breast cancer in a nigerian population and their relationship with different breast cancer morphological variants [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6256.

Abstract 5141: Autoantibody profiling for predictive biomarkers for immune-related adverse events and clinical benefit in rare tumors treated with anti-PD-1 therapy

Abstract Background: Immune checkpoint inhibitors (ICIs) have changed the cancer treatment paradigm; however, with high frequency of immune-related adverse events (irAEs) and limited response rates in select patients. This underscores the unmet need for the development of biomarkers predictive for the development of irAEs and ICI response. Herein, we conducted autoantibody (AAb) profiling to assess baseline (BL) AAb associations with clinical benefit (CB) and irAEs in patients (pts) with rare tumors (RT) treated with programmed cell death protein 1 (anti-PD-1) therapy. Methods: AAbs against 1168 antigens were analyzed using the SeroTag antibody discovery technology. The study included 41 pts with RT who received anti-PD-1 therapy. We conducted a Significance Analysis of Microarray (SAM) to analyze the association between BL AAbs with irAEs and CB (defined as pts achieving complete response (CR), partial response (PR), or stable disease (SD) for ≥4 months by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1). AAb biomaker candidates were discovered based on filtering for SAM hits with p &amp;lt; 0.05 and a delta score |D| &amp;gt;2. Results: Table 1 outlines patients’ demographics. CB and irAEs were observed in 34% and 39% of patients, respectively. Eighteen BL AAbs were significantly associated with CB such as DNA ligase III (LIG3) and small nuclear ribonucleoprotein polypeptide (SNRPA) (p = 0.002 and p = 0.003, respectively). Likewise, 13 BL AAbs showed significant associations with any-grade irAEs, particularly AAbs to breast cancer 2 (BRCA2) DNA repair associated antigen and chromatin-modifying protein 4A (CHMP4A) (p = 0.001 and p = 0.003, respectively). Conclusion: The predictive potential of autoantibodies as biomarkers is promising. Further evaluation in larger cohorts is needed for validation of our findings and understanding the underlying mechanism. Table 1. Patients’ demographics Total patients n=41 Median age in years (range) 66 (35-84) Male n=19 Female n=22 Tumor type Carcinoma of unknown primary n=13 Squamous cell carcinoma of the skin n=9 Small cell malignancies of non-pulmonary origin n=7 Adrenocortical carcinoma n=6 Vascular sarcoma n=5 Other rare histology n=1 Clinical benefit CR, PR, or SD ≥ 4 months n=14 SD &amp;lt;4 months or progressive disease (PD) n=23 Not evaluable n=4 irAEs Yes n=16 No n=25 Citation Format: Mohamed H. Derbala, Joud Hajjar, Bettzy Stephen, Serdar A. Gurses, Evan Kwiatkowski, Petra Budde, Hans-Dieter Zucht, Manuel Bräutigam, Ann-Sophie Schubert, Behnaz Ahangarianabhari, Enedelia Rodriguez, Mohamed Gouda, Lilibeth Castillo, Abdulrazzak Zarifa, Jeffrey A. How, Justin T. Moyers, David S. Hong, Funda Meric-Bernstam, Aung Naing. Autoantibody profiling for predictive biomarkers for immune-related adverse events and clinical benefit in rare tumors treated with anti-PD-1 therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5141.

Abstract 7237: Peptide-mRNA complex mediated restoration of BRCA-1 tumor suppressor function in BRCA-1 mutated cancers as a new therapeutic strategy

Abstract BRCA1 and BRCA-2 proteins are involved in the repair of DNA damage such as double-strand breaks during S and G2 phases, by intervening in homologous recombination (HR) steps. Breast cancers arising from BRCA-1 mutation carriers (10% of BC) and from epigenetically silenced BRCA-1 (30% of sporadic BC) are associated with a lack of expression and/or function of BRCA-1, which induces genomic instability. Herein, we describe a new potent strategy combining mRNAs with a tumor selective peptide nanocarrier, to selectively rescue BRCA-1 function as potential therapeutic approach in cancers. Proprietary BRCA-1 derived mRNA were complexed with proprietary short amphipathic peptides and the resulting nanoparticles were evaluated on several breast cancer cells, harboring different BRCA-1 alterations. Sensitivity to Veliparib (PARPi) following the nanoparticle treatments were evaluated on PARPI resistant and PARPi sensitive cells. The recruitment of RAD51 to sites of double stranded DNA break was quantified by immunofluorescence. In-vivo efficacy of varying sequences of BRCA-1 mRNA-peptide nanoparticles (2.0 mg/kg, weekly, IV; ADGN-901, -902, -903) and veliparib (50mg/kg, daily, oral) were evaluated on breast cancer (HCC1937-BRCA-1 deficient, PARPi resistant) mouse xenografts. We showed that ADGN-901 inhibits the proliferation of BRCA-1 deficient cell lines from 20 to 60% depending on the type of BRCA-1 alterations. ADGN-902, specifically reduces the proliferation of cells expressing N-terminal truncated BRCA-1, by 50 to 60% and ADGN-903 inhibits proliferation &amp;gt;60% of all cells harboring defects in BRCA-1. Interestingly, ADGN-901 and ADGN-903 were able to resensitize the PARPi resistant cells to veliparib inhibition. We demonstrated that ADGN-903 restores BRCA-1 function in homologous recombination. ADGN-903 prevents RAD51 recruitment to the damage site by reducing RAD51 protein level as well as formation of RAD51 foci following irradiation. IV administration of ADGN-901 and ADGN-903 (2.0 mg/kg) had a strong inhibitory effect on HCC-1937 tumor growth while ADGN-902 and veliparib were inactive. ADGN-901 reduced tumor growth by 95% and ADGN-903 abolished tumor growth with strong tumor regressions. ADGN-901 and ADGN-903, were also evaluated on large tumors of about 500-600 mm3 and were highly effective in preventing further progression and achieving shrinkage of large tumors. ADGN-901 and ADGN-903 treatments are well tolerated, without inducing clinical toxicity. BRCA-1 mRNA-peptide nanoparticles are effective in rescuing BRCA-1 function and inducing tumor regressions in BRCA-1 altered breast cancer cells and tumors. Our study provides a proof-of-concept that restoration of wild type BRCA-1 expression could be a potent therapeutic strategy for BRCA-1 altered tumors whether or not they are PARPi resistant. Citation Format: Gilles Divita, Audrey Grunenberger, Léa Cabrera, Nathalie Durany, Neil Desai. Peptide-mRNA complex mediated restoration of BRCA-1 tumor suppressor function in BRCA-1 mutated cancers as a new therapeutic strategy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7237.

Abstract 6010: BRCA2 reversion alleles confer PARPi resistance via homology-directed repair, not fork protection

Abstract BRCA2 reversion alleles have been identified in relapsed, treatment resistant cancer patients. The reversions restore the open reading frame of the BRCA2 protein often resulting in significant sequence deletions with unknown functional consequences. No reports to date have introduced patient reversion mutations into a BRCA2 null cell model to analyze which BRCA2 functions are re-established and whether all or a subset of activities are required for PARPi resistance. Our study utilized BRCA2 reversion alleles identified through sequencing of circulating tumor DNA (ctDNA) from PARPi resistant ovarian cancer patients. We rigorously evaluated whether altered BRCA2 reversion proteins restore homology-directed repair (HDR), fork protection, or gap suppression to determine the specific activities required for PARPi resistance. We found that reverted BRCA2 proteins are functional for HDR by assessing survival response to PARPi, analyzing RAD51 foci at DSBs, DR-GFP reporter assays, RAD51 binding, and CRISPR/Cas9 gene targeting assays. Surprisingly, using the DNA fibercombing approach to assess replication fork dynamics, we identify two separation-of-function mutants, T1974 and C1654_M1890, which are deficient in fork protection, yet confer PARPi resistance. The mutations are located within the BRC 5-8 domain of BRCA2 proposed to play an important role in RAD51 nucleoprotein filament stability. Biochemical analyses of the purified proteins using single molecule FRET (smFRET) indicate reduced filament stability potentially explaining the deficit in fork protection. In conclusion, these separation-of-function BRCA2 mutations provide new mechanistic insight into the underlying biology of BRCA2 and reveal the specific functions needed to overcome PARPi-mediated cell death. Citation Format: Ryan Jensen, Gemma Moore, Sudipta Lahiri. BRCA2 reversion alleles confer PARPi resistance via homology-directed repair, not fork protection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6010.

Abstract 5596: Exploring BRCA1-Y1853ter and potential therapeutic targets in BRCA1-BRCT mutated cancers

Abstract The breast cancer gene BRCA1 plays a pivotal role as a tumor suppressor gene. Despite the use of poly (ADP-ribose) polymerase inhibitors (PARPi) in treating BRCA1 mutation carriers, the lack of response or the development of acquired drug resistance underscores the pressing need for new therapeutic targets. One intriguing BRCA1 mutation, BRCA1-Y1853ter, characterized by a minimal truncation, has been identified in multiple individuals with Hereditary Breast and Ovarian Cancer (HBOC) syndrome. We have developed a Halo Tag and adenovirus-based system where wild-type BRCA1 (WT BRCA1) and mutant BRCA1 protein complexes can be studied in multiple cell types. Here, we used this system to affinity purify BRCA1 wild-type and mutant complexes, followed by label-free quantitative proteomics to investigate the dynamic interactome variations between WT BRCA1 and BRCA1 mutant. Contrary to the assumed loss of function, our preliminary findings suggest a potential gain of function, as a significant number of candidate proteins exhibit enhanced binding affinity with the mutant BRCA1. We are currently exploring whether these distinct binding characteristics are shared among various BRCA1-BRCT mutants, which may hint at a common tumorigenesis mechanism. Our overarching hypothesis is that identifying a specific binding partner, shared among various BRCA-BRCT mutants, could unveil a novel therapeutic target with broader applicability in treating BRCA1-related malignancies. Citation Format: Jingjing Chen. Exploring BRCA1-Y1853ter and potential therapeutic targets in BRCA1-BRCT mutated cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5596.

BRCA1 deficiency enhances the aggressiveness of breast cancer cells expressing HPV16 oncoproteins.

The precise etiology of breast cancer is not completely understood, although women with BRCA1 gene mutations have a significantly increased risk of developing the disease. In addition, sporadic breast cancer is frequently associated with decreased BRCA1 gene expression. Growing evidence of Human papillomaviruses (HPVs) infections in breast tumors has raised the possibility of the involvement of HPVs in the pathogenesis of breast cancer. We investigated whether the effects of HPV oncoproteins E6 and E7 were influenced by the expression levels of BRCA1. HPV16E6E7 (prototype or E6D25E/E7N29S Asian variant type) were stably expressed in MDA-MB231 breast cancer cells, wild type for BRCA1, or with BRCA1 knocked down. Expression of HPV16E6E7 oncogenes did not affect BRCA1 levels and the abundance of HPV16E6E7 was not altered by BRCA1 knockdown. BRCA1 levels did not alter HPV16E6E7-dependent degradation of G1-S cell cycle proteins p53 and pRb. However, we found that the expression of G2-M cell cycle protein cyclin B1 enhanced by HPV16E6E7 was impacted by BRCA1 levels. Especially, we found the correlation between BRCA1 and cyclin B1 expression and this was also confirmed in breast cancer samples from a Thai cohort. We further demonstrated that the combination of HPV oncoproteins and low levels of BRCA1 protein appears to enhance proliferation and invasion. Transactivation activities of HPV16E6E7 on genes regulating cell proliferation and invasion (TGF-β and vimentin) were significantly increased in BRCA1-deficient cells. Our results indicate that a deficiency of BRCA1 promotes the transactivation activity of HPV16E6E7 leading to increase of cell proliferation and invasion. HPV infection appears to have the potential to enhance the aggressiveness of breast cancers, especially those deficient in BRCA1.

BRCA2 Polymorphisms and Breast Cancer Susceptibility: a Multi-Tools Bioinformatics Approach.

The main focus of this investigation is to identify deleterious single nucleotide polymorphisms (SNPs) located in the BRCA2 gene through in silico approach, thereby,providing an understanding of potential consequences regarding the susceptibility to breast cancer. The GenomAD database was used to identify SNPs. To determine the potential adverse consequences, our study employed various prediction tools, including SIFT, PolyPhen, PredictSNP, SNAP2, PhD-SNP, and ClinVar. The pathogenicity associated with the deleterious snSNPs was evaluated bu MutPred and Fathmm. Additionally, I-Mutant and MuPro were used to assess the stability, followed by conservation and protein-protein interaction analysis using robust computational tools. The 3D structure of BRCA2 protein was generated by SwissModel, followed by validation using PROCHECK and Errat. The GenomAD database was used to identify a total of 7, 921 SNPs, including 1940 missense SNPs. A set of 69 SNPs predicted by consensus to be damaging across all platforms was identified. Mutpred and Fathmm identified 48 and 38 SNPs, respectively to be associated with cancer. While I- Mutant and MuPro assays suggested 22 SNPs to decrease protein stability. Additionally, these 22 SNPs reside within highly conserved regions of the BRCA2 protein. Domain analysis, utilizing InterPro, pinpointed 18 deleterious mutations within crucial DNA binding domains and one in the BRC repeat region. This study establishes a foundation for future experimental validations and the creation of breast cancer-targeted treatment approaches.

BRCA1 and Its Vulnerable C-Terminal BRCT Domain: Structure, Function, Genetic Mutations and Links to Diagnosis and Treatment of Breast and Ovarian Cancer.

The BRCA1 is a tumor suppressor gene that encodes for the BRCA1 protein, which plays a vital role in DNA repair, cell cycle regulation, and the maintenance of genomic stability. The BRCA1 protein interacts with a variety of other proteins that play essential roles in gene regulation and embryonic development. It is a large protein composed of multiple domains. The C-terminal region of the BRCA1 protein consists of two BRCT domains connected by a short linker. The BRCT domains are crucial in protein-protein interactions as well as in DNA damage response and cell cycle regulation through their phosphoprotein binding modules that recognize the phosphorylated protein sequence motif of other kinases. Mutations within the BRCT domain can disrupt the normal function of BRCA1 and lead to an increased risk of developing breast and ovarian cancer. Herein, we explore the structural characteristics of BRCA1, focusing on the BRCT domain, its interactions with key cellular components, and its involvement in various cellular processes. In addition, the impact of BRCT domain mutations on breast and ovarian cancer susceptibility, prognosis, and treatment options is discussed. By providing a comprehensive understanding of the BRCT domain of BRCA1, this review aims to shed light on the role of this important domain in the pathogenesis and potential therapeutic approaches for breast and ovarian cancer.

Abstract A020: NAD+ Boosting through NRH supplementation enhances treatment efficacy in EOC

Abstract Background: Dihydronicotinamide riboside (NRH), the reduced form of nicotinamide riboside (NR), is a recently identified, naturally occurring precursor of arguably the most crucial cofactor for cellular function, Nicotinamide Adenine Dinucleotide (NAD+). Recent investigation suggests that NRH is more adept at increasing NAD+ stores than traditional NAD precursors, and such extreme NAD+ boosting via NRH supplementation induces cytotoxicity in certain cellular contexts. It has also been shown that the lack of functional BRCA protein in epithelial ovarian cancer (EOC) directly impacts intracellular NAD+ levels. Given that altered cellular metabolism and DNA repair mechanisms are central alterations in EOC, and these processes are functionally dependent on NAD+, we sought to assess whether NRH supplementation in EOC cell lines enhanced cellular cytotoxicity alone and in combination with standard therapeutic agents. Methods: We supplemented 3 ovarian cancer cell lines (SKOV3, OVCAR8 and ES2) with NRH and traditional NAD precursor, NA (nicotinic acid) alone and in combination with carboplatin, paclitaxel, combination, and olaparib. Cytotoxicity was measured via CellTiter-Glo. RNA sequencing of EOC cell lines was performed to determine the differential expression of NAD+ anabolic and catabolic enzymes. Of note, all three cell lines are known to be BRCA1 &amp;2 wildtype while OVCAR8 cells are hypermethylated and harbor loss of heterozygosity (LOH high) at the BRCA1 loci. Results: Significant cytotoxicity was noted in NRH treated cells (~40 %) with minimal cell death in the NA treated lines. Strikingly, NRH supplementation enhanced carboplatin cytotoxicity by 25-50 % depending on cell line, paclitaxel cytotoxicity by 10-25 %, and the combination by 10-35 % whereas NA supplementation had no effect on the baseline treatment induced cytotoxicity. Interestingly, the effect of NRH supplementation with olaparib differed between the ES2 and OVCAR8 cell lines, with a significant 20 % increase in cell death in ES2 vs OVCAR8 cells with a negligible increase in cell death. PARP inhibition by olaparib requires NAD+. RNA sequencing revealed an increased expression in NAMPT, an enzyme involved in the NAD+ salvage pathway in the ES2 cell line relative to the OVCAR8, suggesting that the ES2 cells harbor a baseline NAD+ deficit rendering them more vulnerable to PARP inhibition following NAD+ boosting. This is also consistent with the OVCAR8 data suggesting that hypermethylated BRCA1 results in a relative increase in NAD+ to the extent that NRH supplementation does not enhance the efficacy of PARP inhibition. Conclusions: Here we show that in the context of EOC, exploitation of the NAD+ bioenergetic phenotype through NRH supplementation is a biologically feasible strategy to enhance the response of traditional therapy with potentially minimal toxicity. This data suggests several potential mechanisms by which cellular NAD+ availability belies treatment efficacy and resistance and highlights the potential utility of NAD+ metabolomics as a biomarker to guide treatment decisions. Citation Format: Kevin Lee, Tanvi Joshi, Catherine Lyons, Mary Howard Singleton, Elizabeth Catranis, Sagar Chokshi, Luciana Madiera da Silva, Marie Migaud, Jennifer Scalici. NAD+ Boosting through NRH supplementation enhances treatment efficacy in EOC [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr A020.

A case of hereditary breast and ovarian cancer syndrome of initially presented as cancer of unknown primary with lymph node metastases unveiled by genetic analysis

Cancer of unknown primary (CUP) is a heterogeneous disease concept involving various malignant tumors. Understanding its pathophysiology is often difficult, together with its treatment. Here, we present a case of CUP with abdominal lymph node enlargement and elevated carbohydrate antigen 125 levels. It initially resembled a favorable prognosis type similar to ovarian cancer, but metastases were observed in cervical lymph nodes, indicating a somewhat atypical CUP compared to the typical ovarian cancer-like CUP. We identified a germline Breast Cancer 1 (BRCA1) p.L63* variant through a family history inquiry and BRCA analysis, indicating hereditary breast and ovarian cancer syndrome. The patient achieved near-complete remission with platinum-based therapy followed by poly (ADP-ribose) polymerase (PARP) inhibitor. The variant has shown sensitivity in both clinical and pathogenic reports in the ClinVar database of the National Institutes of Health. No clinical studies reported on the efficacy of PARP inhibitors specific to this variant, but our case demonstrated the sensitivity of platinum-based therapy followed by PARP inhibitor. Reports of CUP in hereditary breast and ovarian cancer syndrome are very rare, with only a single report in the literature.