Mutation-associated Breast Cancer Research Articles

A systematic review of racial disparity in pivotal poly (ADP-ribose) polymerase (PARP) inhibitor trials.

e13737 Background: Breast cancer is the most common cancer diagnosed worldwide. Breast cancer related mortality has decreased in the US, however this did not extend equally to African American women (AAW). According to CDC mortality rate from breast cancer in AAW is 20% higher than other ethnic groups. Younger age at diagnosis in AAW, higher incidence of triple negative breast cancer (TNBC), and higher incidence of AA males with breast cancer suggest genetic predisposition plays an important role in the disparate outcomes based on race. In an unbiased analysis of TNBC cases, the prevalence of pathogenic germline BRCA 1 & 2 mutations are twice as high as in breast cancer overall. Poly (ADP-ribose) polymerase (PARP) inhibitors have proven to be effective in germline BRCA 1 and BRCA 2 mutation associated breast cancer. However, data regarding the enrollment of racial and ethnic minorities in these pivotal trials that lead to the approval of these drugs is limited. Methods: We examined the demographic data reporting in Phase II/ III clinical trials of PARP inhibitors in breast cancer from 2016 to 2023. In order to highlight the disparities in the enrollment of minority groups we calculated an enrollment percentage of various racial groups in these trials. We conducted a systematic review of Phase II/III clinical trials of PARP inhibitors in BRCA 1 & 2 mutated breast cancer reported studies with sources from PubMed, Embase, Scopus, Clinicaltrials.gov, CENTRAL and Cochrane. 56 full text studies were identified, out of which 14 met inclusion criteria. The total number of patients included was N=5,067. Five trials did not include racial data. Results: Among trials that reported race and ethnicity (N=4004), the enrollment percentage was lowest for racial and ethnic minorities. AA: 3.4%, N=136. Non- Hispanic Whites were the most common to be enrolled: 71.05%, N=2845, Asians were 16.53% N= 662, Hispanics 2.03 %; N=83 and other 6.17%, N=247. Conclusions: Racial minorities are consistently underrepresented in all the pivotal PARP inhibitor trials and contributing to the race-based disparities in breast cancer. [Table: see text]

Perspectives and possibilities of preserving reproductive function in patients receiving antitumor treatment. Clinical observation

Currently, treatment of patients with early primary operable BRCA mutation-associated breast cancer requires integrative approach. A mutation in BRCA1/2 genes is a prognostically unfavorable factor increasing the risk of cancer of the contralateral breast, as well as ovaries, pancreas, fallopian tubes, and primary peritoneal cancer. In this clinical observation, an integrative multidisciplinary approach to treatment of a young patient with luminal B breast cancer is described which allowed to preserve the patient’s fertility and achieve pregnancy using assisted reproductive technologies.High effectiveness of the chosen treatment tactics in the framework of integrative approach in a specialized medical facility with experience in treatment of oncological diseases and preservation of reproductive function confirmed by clinical data and results of laboratory and instrumental exams is demonstrated.

Triple Negative Breast Cancer: Tumour Biology and Optimisation of Clinical Outcome

Triple negative breast cancer are breast cancer types that are difficult to treat because they lack expression of the estrogen receptor (ER), progesterone receptor (PR) and Human Epidermal Receptor 2 (HER2) gene amplification. Intensive research, analysis by the Cancer Genome Atlas (TCGA) Research Network and the advent of high-throughput technology tools has expanded the classification of TNBC tumors into subgroups according to its gene expression profiles in order to identify the different molecular subtypes, novel TNBC biomarkers that can play both predictive and prognostic roles and enhance therapeutic strategies. The “immune-activated,” subtype or tumours with defective BRCA pathway are amongst initial TNBC group with established genetic vulnerabilities that has allowed the addition of promising therapeutic approaches, including DNA-damaging agents (PARP inhibitors, platinum) as well as immunotherapy. The treatment of metastatic NBC (mTNBC) is currently transforming rapidly with better outcomes observed in clinical trials. The recent success with immune checkpoint inhibitors (ICIs) targeting the programmed cell death receptor 1 and programmed death ligand 1 (PD-L1) and PARP inhibitors for germline BRCA mutation-associated breast cancers as well as other novel strategies in mTNBC treatment will change the course of this unique cancer subtype in the future.

Breast conserving surgery in BRCA1, BRCA2, CHEK2- mutation associated breast cancer

Nowadays, the success of chemotherapy for breast cancer demonstrates high sensitivity and effectiveness, and therefore it has become possible to increasingly use breast conserving surgery treatment. Genetically associated breast cancer patients it is a separate clinical group, the treatment of which should take into account the carriage of mutations in the BRCA1, BRCA2, CHEK2 genes. Until now, the possibility of breast conserving surgery in such patients remains debatable. After all, we often talk in such patients not only about the need to perform a mastectomy, but also about a prophylactic mastectomy from the contralateral side to minimize the risks of cancer. Is it acceptable to perform breast conserving treatment in such patients? This article analyzes the experience of well-known foreign oncologists, as well as analyzes their own experience of the Department of Oncology and Radiology RUDN University, Head of the Department of Oncology and Reconstructive Surgery of the Mammary Gland and Skin, P. Hertsen Moscow Oncology Research Institute — Branch of the National Medical Research Radiological Centre of the Ministry of Health of the Russian Federation.

Abstract ES6-4: Parp inhibitors for brca1/2mutation associated breast cancer

Abstract More than 15 years ago we and others showed the use of potent PARP1 inhibitors (PARPi), that both inhibit the catalytic activity of the PARP1 enzyme and trap PARP1 onto DNA, generate a “synthetic lethal” interaction with the malignant cell specific loss of function of genes crucial for homologous recombination (HR) gene function. This phenomenon has now been exploited with therapeutic intent in several contexts leading to approved single agent PARPi treatments for advanced forms of ovarian, prostate, pancreatic and breast cancers. These approvals have in large part been associated a biomarker requirement for evidence of loss of function of HR. Recently a number of trials have investigated PARPi in a (neo)adjuvant breast cancer treatment (NACT) setting in patients with (or enriched for) HR deficiency. These have included phase II neoadjuvant PARPi studies such as the NeoTALA study using single agent talazoparib in germline BRCA1 and BRCA2 mutation carriers and the combination chemotherapy and olaparib therapy studies GeparOLA and PARTNER, enriched for HR deficient breast cancer, that have reported important signals with regard efficacy and tolerability. Two recent phase III trials have influenced recent early breast cancer treatment guidelines. These are the BrighTNess trial in the neoadjuvant setting and OlympiA in the post-(neo)adjuvant setting. BrighTNess recruited patients with biologically heterogeneous triple negative breast cancer (TNBC) and used the weak PARP1 trapping PARPi veliparib and OlympiA restricted eligibility to patients with the germline “pathogenic” or “likely pathogenic” mutation in BRCA1 or BRCA2 but included patients with hormone receptor positive breast cancer. BrighTNess did not show convincing evidence of benefit to the addition of veliparib to standard of care in TNBC NACT but has shown the benefit to the addition of carboplatin to sequential paclitaxel-AC NACT with significant improvements in event free survival (HR 0.57 ) compared to sequential paclitaxel-AC alone. OlympiA has reported following an interim analysis showing 12 months of olaparib in the post-(neo)adjuvant chemotherapy setting improves both invasive disease free and distant disease free survival by approximately 40% with highly statistically significant hazard ratios of 0.58 and 0.57 respectively that met pre-specified early stopping boundaries. The publication of results for OlympiA has led to rapid updates of both genetic testing and treatment international guidelines for BRCA1 and BRCA2 mutation associated breast cancer to include use of olaparib in patients meeting the eligibility criteria for the trial. The lecture will both explore the data and the implications for practice of the adoption of these guidelines and some of the ongoing questions to be addressed by ongoing clinical trial and translational research initiatives. Citation Format: ANJ Tutt. Parp inhibitors for brca1/2mutation associated breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES6-4.

Effect and Safety of Therapeutic Regimens for Patients With Germline BRCA Mutation-Associated Breast Cancer: A Network Meta-Analysis

PurposeBreast cancer type 1 susceptibility (BRCA) mutations not only increase breast cancer (BC) risk but also result in poor survival and prognosis for BC patients. This study will analyze the effect and safety of therapeutic regimens for the treatment of BC patients with germline BRCA (gBRCA) mutations by network meta-analysis.MethodsPublic databases were searched from inception to 29 April 2021. Frequentist network meta-analysis was conducted to analyze the benefit of chemotherapy and targeted drug-related strategies.ResultsSeventeen articles were included in the analysis. For progression-free survival (PFS), olaparib (hazard ratio (HR): 0.58; 95% confidence interval (CI): 0.43 – 0.79), platinum (HR: 0.45; 95% CI: 0.22 – 0.89), and talazoparib (HR: 0.54; 95% CI: 0.41 – 0.71) were significantly better than platinum-free chemotherapy (Chemo). The results based on indirect comparisons showed that veliparib (Vel) + platinum + Chemo was also significantly better than Chemo (HR: 0.37; 95% CI: 0.20 – 0.69). For overall survival (OS), olaparib was significantly better than Chemo only in the population who did not receive prior chemotherapy. For pathologic complete response (pCR), bevacizumab+Chemo had a significant advantage over platinum agents (OR: 3.64; 95% CI: 1.07 - 12.39). Olaparib and talazoparib both showed significantly higher objective response rates (ORRs) than Chemo.ConclusionThe PFS results suggested that olaparib, talazoparib, and Vel+platinum agent+Chemo were ideal regimens for overall, TNBC, and advanced BC patients with gBRCA mutations. Whether PARPis are suitable for patients with gBRCA mutations who have received prior platinum therapy still needs to be clarified.

Twenty-one-gene recurrence score (RS) in germline (g)CHEK2 mutation-associated versus sporadic breast cancers (BC): A multi-site case-control study.

10531 Background: Genomic assays, such as RS, are used to determine chemotherapy benefit in early-stage, estrogen receptor (ER)- and/or progesterone receptor (PR)-positive, HER2 negative BC patients (pts). Currently, guidelines to use pts’ germline genetic testing results to guide adjuvant therapy are lacking. Several reports have indicated worse outcomes for BC pts with g CHEK2 pathogenic variants (PV). We investigated whether PV in CHEK2 were associated with increased RS. Methods: Patient-level clinical data and RS were derived from electronic medical records of seven medical centers between years 2013-17. Confirmation of RS using the Genomic Health provider portal was performed. 38 pts with germline PV in CHEK2 (15 pts/39.5% with c.1100delC mutation) and RS score (cases) were matched with BC pts whose genetic testing did not identify PV (controls) using a 1:2 matching schema. Pts were matched based on age at diagnosis and lymph node (LN) status. LN negative pts were further matched based on T-stage. A multivariate random intercept linear mixed model of CHEK2 mutation status on RS was performed, adjusting for PR. A secondary ordinal univariate analysis was conducted that categorized RS into low, intermediate and high risk ( < 18, 18-30, and > 30, respectively). P-values were reported based on a null hypothesis of no effect against a two-sided alternative. Results: The median RS for cases was 19.5 (interquartile range [IQR]: 15 to 25) and the median RS for controls was 18 (IQR: 12 to 22). A greater proportion of cases were categorized as high risk (10.5%) compared to controls (5.6%), and a smaller proportion of cases were categorized as low risk (36.8%) compared to controls (49.3%). Cases had higher grade and increased proportion of PR-negative BC as compared with controls (grade 1: 12.1% of cases versus 32.4% of controls; PR-negative: 7.9% of cases versus 5.6% of controls). The variables used to match cases and controls (age, lymph node status, and T-stage) had similar summary statistics. The RS was 1.97-point higher in pts with g CHEK2 PV compared to controls, after adjusting for PR (95% confidence interval [CI]: 1.02-point lower to 4.96-point higher; p = 0.194). The secondary analysis of CHEK2 mutation status on an ordinal RS risk group yielded comparable results; on average, the odds of being high risk compared to the combined intermediate/low risk groups was 1.72 times higher in cases compared to controls (95% CI: 0.77 to 3.80; p = 0.181), but these differences were not significant. Conclusions: Our case-control study did not show a statistically higher RS for BC that develops in pts with g CHEK2 PV. Further studies are warranted to evaluate the association between type of CHEK2 PV (frameshift versus missense) and other modifying genetic variables and RS.

A phase II clinical trial of talazoparib monotherapy for PALB2 mutation-associated advanced breast cancer.

TPS1109 Background: PALB2 (Partner and Localizer of BRCA2) plays a critical role in the maintenance of genomic integrity through its role in the Fanconi anemia and homologous recombination DNA repair pathways. Our recently reported phase II clinical trial (Gruber, et al. JCO 2019) showed that talazoparib monotherapy was associated with single agent activity in germline PALB2 (gPALB2) mutation-associated advanced breast cancers. Of 5 patients with a germline PALB2 mutation, all 5 had reduction in target lesions > 20% with 3 of 5 achieving a RECIST 1.1 response. All patients had visceral metastases and were heavily pretreated; one response occurred in a patient with 8 prior lines of therapy for metastatic breast cancer. Clinical activity of the PARP inhibitor olaparib was also demonstrated in breast cancer patients with gPALB2 mutations in the Olaparib Expanded trial (TBCRC 048). Thus, we believe there is significant value in generating additional PARP inhibitor monotherapy data in subjects with advanced PALB2 mutation-associated breast cancer. We propose this phase II trial to better estimate the rate of RECIST 1.1 objective response in this patient population. Methods: This is a single-arm, two-stage, non-randomized study to assess the objective response rate (ORR) of talazoparib monotherapy in patients with PALB2 mutation-associated advanced breast cancer. Eligible subjects will be adults with inoperable locally advanced or metastatic breast cancer with a germline or somatic PALB2 mutation with 0-3 prior therapies for advanced disease. Eligible patients must have a deleterious or suspected deleterious mutation in PALB2 on a CLIA approved commercial germline or next generation sequencing tumor assay. Study treatment is talazoparib 1 mg PO daily. In stage 1, ORR will be assessed after 15 patients; if at least 2 responses are observed then an additional 15 patients will be enrolled; if less than 2 responses are observed the study will be terminated. The primary objective is to evaluate whether talazoparib monotherapy can induce a 30% ORR in subjects with advanced breast cancer associated with a PALB2 mutation. Response will be assessed by RECIST 1.1. Secondary objectives include safety, PFS, clinical benefit rate, and patient-reported quality-of-life. Exploratory endpoints will assess for the presence of PALB2 loss-of-heterozygosity, biallelic mutations, correlation of ctDNA profile with treatment response and the correlation of germline versus somatic mutations with response rate. This trial is currently activated and enrolling at Stanford Cancer Center and it is expected that 4 additional sites will be added. Conclusion: This trial will evaluate gPALB2 as a biomarker for PARP inhibitor monotherapy in advanced or metastatic HER2- breast cancer. Clinical trial information: pending .

A review of current progress in triple-negative breast cancer therapy.

Triple-negative breast cancer (TNBC) is a particularly aggressive subtype known for its extremely high drug resistance, progression, poor prognosis, and lack of clear therapeutic targets. Researchers are aiming to advance TNBC treatment worldwide. In the past 2–3 years, more positive results have emerged in the clinical research on TNBC treatment. Based on the results, several impressive drugs have been approved to benefit patients with TNBC, including the PARP inhibitors olaparib and talazoparib for germline BRCA mutation-associated breast cancer (gBRCAm-BC) and immunotherapy using the checkpoint inhibitor atezolizumab in combination with nab-paclitaxel for programmed cell death-ligand 1-positive (PD-L1+) advanced TNBC. Although neoadjuvant therapy has focused on combinations of systemic agents to optimize pathologically complete response, metastatic TNBC still has a poor prognosis. Innovative multidrug combination systemic therapies based on neoadjuvants and adjuvants have led to significant improvements in outcomes, particularly over the past decade.

Abstract 2500: Copy number variation in recurrent BRCA1/2 germline mutation-associated breast and ovarian cancers

Abstract Carriers of pathogenic germline mutations in BRCA1/2 are highly predisposed to breast and ovarian cancers. Although their primary tumors respond to DNA-damaging agents, such as platinum-based chemotherapy and poly (ADP-ribose) polymerase inhibitors (PARPi), these malignancies often return as therapy-resistant recurrences. To identify genetic mechanisms of therapeutic resistance, we performed whole exome sequencing on 41 pairs of matched primary/recurrent breast and ovarian tumors from 27 BRCA1/2 mutation carriers. The cohort consisted of 14 ovarian cancer patients (nine BRCA1, five BRCA2) and 13 breast cancer patients (nine BRCA1, four BRCA2). Five patients received PARPi, 17 patients received platinums, and all patients received some type of chemotherapy prior to recurrence. First, we performed a segmentation analysis to assess copy number variation (CNVs) in each tumor. We calculated homologous recombination deficiency (HRD) scores for each tumor, but found no significant differences between matched primary/recurrent pairs. We noted that primary tumors had a relatively high average HRD score (55/100), which remained high in recurrences (52/100). Next, we totaled arm-level CNVs to generate aneuploidy scores for each tumor. Using a Wilcoxon signed rank test, we found that aneuploidy scores were significantly higher in recurrences than in matched primary tumors (p=0.007). This finding suggests that recurrences have more arm-level CNVs than primary tumors, but that acquired genomic abnormalities are not caused by HRD per se. Instead, arm-level CNVs indicate that replication errors or genome doubling events are more common in recurrences than in primary tumors. Lastly, we annotated all tumors' CNVs with genes to interrogate potential effects on signaling pathways, including CNVs exclusive to each recurrence. Using Gene Set Enrichment Analysis with Hallmark gene sets, we identified pathways significantly (FDR q<0.30) affected by losses (CN≤1) and gains (CN≥4) from primary tumor CNVs, recurrent tumor CNVs, and recurrence-exclusive CNVs. All three CNV sets showed gains encompassing interferon gamma response genes and losses of Hedgehog signaling genes. Primary tumor losses were enriched for reactive oxygen species and cholesterol homeostasis genes. Recurrent tumor and recurrence-exclusive gains were enriched for UV-responsive and MTORC1 signaling gene sets, which may enhance survival in the presence of DNA-damaging or cytotoxic chemotherapies. These findings suggest that CNVs encompass different genes in recurrences compared to matched primary tumors. Further, differences in gene dosage and downstream signaling could represent novel therapeutic targets for recurrent tumors. Ultimately, we found that CNVs grant insights into the genomic and signaling processes that underlie acquired therapeutic resistance in BRCA1/2 mutation-associated cancers. Citation Format: Jennifer Brady Shah, Bradley Wubbenhorst, John Pluta, Caitlin Feltcher, Lauren Schmucker, Kurt D'Andrea, Heather Symecko, Catherine Ruan, Anupma Nayak, Kara N. Maxwell, Susan Domchek, Katherine L. Nathanson. Copy number variation in recurrent BRCA1/2 germline mutation-associated breast and ovarian cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2500.

Abstract ES12-1: Clinical indications of PARP1 inhibitors and other targets

Abstract Two PARP1 inhibitors, olaparib and talazoparib, garnered regulatory approvals for the treatment of advanced HER2-negative breast cancer associated with a germline BRCA1 or BRCA2 mutation in 2018. The approvals were based on a prolongation of progression-free survival with PARP inhibitor monotherapy compared to non-DNA damaging single agent chemotherapy in the 1st - 4th line metastatic setting. While the availability of these therapies has increased therapeutic options for this group of patients, median progression-free survival ranged from 7 - 8.6 months and no overall survival advantage has been observed to date. While response rates with PARP inhibitor monotherapy are high, development of resistance remains a significant clinical problem. Further, how PARP inhibitor monotherapy compares with platinum-based chemotherapy in this group of patients has been unclear. The recently reported phase III BROCADE 3 clinical trial examining carboplatin and paclitaxel with the addition of veliparib or placebo added important insights. This was the first phase III trial in patients with advanced germline BRCA1 and BRCA2 mutation-associated HER2-negative breast cancer that examined the use of a PARP inhibitor combined with DNA damaging chemotherapy in the 1st-3rd line setting followed by blinded monotherapy after discontinuation of chemotherapy. The median progression-free survival was significantly prolonged with the addition of veliparib (14.5 versus 12.6 months) with 26% of patients in the veliparib arm remaining progression-free at 36 months. Median overall survival was 33.5 months in the veliparib arm compared to 28.2 months in placebo with 44% of patients in the placebo arm crossing over to receive veliparib after disease progression. While important differences exist between these three trials, BROCADE 3 has reported the longest progression-free and overall survival to date with PARP inhibitor therapy in advanced germline BRCA1 and BRCA2 mutation-associated breast cancer. Beyond BRCA1 and BRCA2, PARP inhibitors are also being investigated in homologous recombination deficient advanced breast cancer in a number of clinical trials. In the Talazoparib Beyond BRCA study, high clinical activity was noted in germline PALB2 mutation carriers. The Olaparib Expanded trial is ongoing. Citation Format: ML Telli. Clinical indications of PARP1 inhibitors and other targets [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr ES12-1.

Targeted Therapies for Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a particularly aggressive subtype of breast cancer. TNBC is a heterogenous subtype of breast cancer that is beginning to be refined by its molecular characteristics and clinical response to a targeted therapeutic approach. Until recently the backbone of therapy against TNBC has been cytotoxic chemotherapy. However, the breast oncology community is now seeing encouraging clinical activity from molecularly targeted approaches to TNBC. Recently, we have seen 3 newly approved targeted therapies for TNBC, including the PARP inhibitors olaparib and talazoparib for germline BRCA mutation associated breast cancer (gBRCAm-BC) and most recently the checkpoint inhibitor, atezolizumab in combination with nab-paclitaxel for programmed death-ligand 1 (PD-L1+) advanced TNBC. Improved biomarkers are needed to inform better patient selection for treatment with checkpoint inhibition. Higher response rates are seen when checkpoint inhibitors are combined with chemotherapy in the first-line setting and the use of these agents at an earlier stage of the disease does show promise. Antibody-drug conjugates are generating much excitement and may allow re-examination of prior cytotoxics that failed in development due to toxicity. Tumor sequencing is identifying potential molecular targets and ongoing studies are evaluating novel small molecule agents in this field such as AKT inhibition and many others. The treatment paradigm of chemotherapy as "one size fits all" approach for management of TNBC is changing based on molecular subtyping. Soon, the term TNBC may no longer be appropriate, as this heterogenous subtype of breast cancer is further refined by its molecular characteristics and clinical response to a targeted therapeutic approach.

Latest development of PARP inhibitors in ovarian cancer

Abstract Ovarian cancer is a highly lethal gynecologic malignancy. Approximately 10000 new cases of ovarian cancers are diagnosed annually in Japan and 5,000 patients die per year. Almost half of patients are diagnosed as stage III or IV at the time of initial diagnosis, and despite the first-line aggressive treatment with surgery and platinum-based combination chemotherapy, the 5-year survival rate of stage III and IV is less than 25%. The improvement of new treatment for advanced ovarian cancer is of paramount importance. BRCA 1/2 gene is engaged in homologous recombination (HR), which is a major double-stranded DNA repair pathway. About 20% of high-grade serous ovarian carcinoma (HGSOC) harbor germline BRCA1/2 mutations, and about 50% of high-grade serous adenocarcinoma have somatic or germline mutations or epigenetic change in genes of HR DNA repair such as RAD51C, ATM, ATR, and FANCD2. Olaparib is an oral poly (ADP-ribose) polymerase inhibitor (PARPi) that inhibits single-stranded DNA damage repair. Olaparib has a significant clinical activity in BRCA1/2 mutation-associated breast and ovarian cancer, and also has activity in ovarian cancer. In the Study 19, maintenance therapy with olaparib significantly prolonged progression-free survival (PFS) versus placebo in patients with platinum-sensitive recurrent serous ovarian cancer. Moreover, subsequent phase 3 clinical trials show major improvement of prognosis in maintenance therapy by incorporating olaparib in a recurrent setting and recently in a first-line setting among patients with BRCA1/BRCA2 mutations. Furthermore, various combination treatment strategies such as other DNA damage response inhibitors such as ATR inhibitors, immune checkpoint inhibitors and molecular-targeted therapies such as VEGF inhibitors, has been examined to enhance the efficacy of PARP inhibitors. In this symposium, we discuss the current status and future perspectives of PARP inhibitors for ovarian cancer.

Abstract P3-11-06: HRD (homologous recombination deficiency) score and its clinicopathological features in neoadjuvant chemotherapy treated sporadic breast cancers

Abstract [Purpose]Homologous Recombination Deficiency (HRD) score has been developed to evaluate the DNA double-strand break repair function. BRCA1/2 germline mutation-associated breast cancers are known to show a high HRD score and a high sensitivity to platinum-based chemotherapy as well as PARP inhibitor. HRD can be theoretically induced by not only the dysfunction of BRA1/2 but also the dysfunction of the other molecules involved in homologous recombination, and, actually, high HRD score is reported to be seen in a significant proportion of sporadic breast tumors without BRCA1/2 mutation. The aim of the present study was to elucidate the clinicopathological characteristics of sporadic breast tumors with high HRD score as well as their sensitivity to sequential paclitaxel and FEC chemotherapy (P-FEC). [Methods]Tumor tissues obtained by Mammotome from 132 sporadic breast cancer patients (stage II-III) before neoadjuvant chemotherapy with P-FEC were subjected to assay for HRD score using Oncoscan CNV kit®. HRD score was a simple sum of NtAI, LOH, and LST (cutoff, 42), and were also subjected to the gene expression analysis using the Affymetrix microarray (U133 plus 2.0). BRCA1 promoter methylation was assayed by methylation specific real-time PCR. [Result]Of the 132 breast tumors, 32% showed a high HRD score which were significantly associated with high histological grade (P=0.001), negative progesterone receptor (P=0.023) and high Ki67 index (P=0.004). Triple negative breast cancer (TNBC)(n=19) showed a significantly (P<0.001) higher HRD score than the other subtypes (HR+/HER2-(n=73), HR+/HER2+(n=12), HR-/HER2+(n=18)). BRCA1 promoter methylation was significantly associated with a high HRD score. There was no significant correlation between HRD score and pCR to P-FEC when all tumors were considered but tumors with a high HRD score showed a significantly (P=0.020) lower pCR rate when only TNBC were considered. In TNBC, majority of tumors showed a high HRD score in five subtypes (BL1, BL2, IM, M, MSL) but no tumor showed a high HRD score in LAR (luminal androgen receptor) subtype. [Conclusion]Approximately one third of sporadic breast tumors show a high HRD score, indicating the presence of homologous recombination dysfunction, and they are most often seen in TNBC with BRCA1 promoter methylation and never in LAR subtype. Interestingly, breast tumors with a high HRD score were less sensitive to P-FEC. Citation Format: Imanishi S, Naoi Y, Shimazu K, Shimoda M, Kagara N, Tanei T, Miyake T, Kim SJ, Noguchi S. HRD (homologous recombination deficiency) score and its clinicopathological features in neoadjuvant chemotherapy treated sporadic breast cancers [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-11-06.

NADP+ is an endogenous PARP inhibitor in DNA damage response and tumor suppression

ADP-ribosylation is a unique posttranslational modification catalyzed by poly(ADP-ribose) polymerases (PARPs) using NAD+ as ADP-ribose donor. PARPs play an indispensable role in DNA damage repair and small molecule PARP inhibitors have emerged as potent anticancer drugs. However, to date, PARP inhibitor treatment has been restricted to patients with BRCA1/2 mutation-associated breast and ovarian cancer. One of the major challenges to extend the therapeutic potential of PARP inhibitors to other cancer types is the absence of predictive biomarkers. Here, we show that ovarian cancer cells with higher level of NADP+, an NAD+ derivative, are more sensitive to PARP inhibitors. We demonstrate that NADP+ acts as a negative regulator and suppresses ADP-ribosylation both in vitro and in vivo. NADP+ impairs ADP-ribosylation-dependent DNA damage repair and sensitizes tumor cell to chemically synthesized PARP inhibitors. Taken together, our study identifies NADP+ as an endogenous PARP inhibitor that may have implications in cancer treatment.

Differential Claudin 3 and EGFR Expression Predicts BRCA1 Mutation in Triple-Negative Breast Cancer

BRCA-1 mutation-associated triple-negative breast cancer (TNBC) has been hypothesized to exhibit a phenotype that is distinct from non-mutation carriers. We have analyzed immunohistochemically detected cytokeratins 5 and 14, epidermal growth factor receptor (EGFR), claudin (CLDN) 3, 4, and 7, and E-cadherin in 57 TNBC (32 BRCA1 and 8 BRCA2 tumors, 17 WT tumors). Positive staining of CLDN3 and negative EGFR expression in TNBC are associated with a BRCA1 mutation. EGFR and CLDN3 expression was able to predict the presence of BRCA1 mutation (area under curve 0.802, p < 0.001). This could help in guiding the decision for BRCA testing.

Abstract A22: Homologous recombination deficiency negatively predicts for immune infiltration and antitumor immune activity in breast tumors with BRCA1/2 alterations

Abstract Tumors with germline or somatic BRCA1 or BRCA2 alterations are sensitive to DNA-damaging agents but often develop therapeutic resistance. Breast cancers associated with BRCA1/2 alterations have a relatively high mutational load, defined as the number of nonsynonymous single nucleotide mutations, relative to BRCA1/2 wild-type tumors, leading to suggestions that patients with BRCA1/2 mutations are possible candidates for immune checkpoint blockade. However, immune infiltration can range widely in tumors with BRCA1/2 alterations, and molecular determinants that account for this variability remain unclear. Our goal was to delineate the molecular features associated with immunogenicity in breast cancers associated with germline or somatic BRCA1/2 alterations through genetic/genomic and histopathologic analyses in 115 tumors from the TCGA (n=89) and Penn (n=26). In the TCGA dataset, we found that the level of homologous recombination deficiency (HRD), as measured by the copy number-based HRD score (high vs. low, dichotomized by median), correlated positively with neoantigen load in BRCA1/2 tumors (p=0.02), but unexpectedly inversely with immunogenicity as measured by cytolytic index (p=0.04) (geometric mean of PRF1 and GZMA expression) and immune ESTIMATE (p=0.002), an RNA-seq-based measure of immune cell infiltration. In prior studies, we had found that a surprisingly high percentage of BRCA1 and BRCA2 germline mutation-associated breast cancers lacked allele-specific loss of heterozygosity (LOH), 10% and 46%, respectively. We thus evaluated whether allele-specific LOH of germline BRCA2 mutations and somatic BRCA1/2 mutation clonality were drivers of the negative association between HRD level and cytolytic index/immune ESTIMATE. We found that allele-specific LOH was associated with higher HRD score (p=0.015) but lower enrichment of the Type II IFN signaling immune metagene (p=0.01), lower cytolytic index (p=0.04), and lower immune ESTIMATE score (p=0.01); tumors with clonal somatic BRCA1/2 mutations had significantly higher HRD score (p=2.4E-07) and mutational burden (p=0.05) but lower cytolytic index (p=0.003) and immune ESTIMATE scores (p=5E-05) than tumors with subclonal somatic BRCA1/2 mutations. Stratifying by both hormone receptor expression and median HRD score, we found that triple-negative breast cancers with low HRD were the most immunogenic and hormone receptor-positive tumors with high HRD the least (p=0.001). We confirmed these TCGA findings by histopathology in tumors associated with germline mutations in BRCA1/2 from Penn. We found that CD45+ leukocyte (p=0.03) and CD8+ cytotoxic T-cell infiltration (p=0.03) as well as expression of the immune effector PRF1 (p=0.048) were significantly lower with high HRD. Further, tumors with allele-specific LOH of the germline BRCA1/2 mutation had significantly lower PRF1 staining (p=0.004), lower membrane levels of the immune checkpoint protein PDL1 (p=0.05), and lower CD8+ (p=0.001), FoxP3+ (p=0.03), and CD20+ (p=0.04) immune cells, suggesting an immunosuppressive role for allele-specific LOH leading to high HRD. These data are consistent with a prior pan-TCGA analysis demonstrating that increased tumor chromosome/arm level copy number alterations suppress immunogenicity. We have found, for the first time, that genomic instability in BRCA1/2 tumors is associated with lower antitumor immune activity, and that the immunogenicity of BRCA1/2 mutation-associated breast cancers is directly related to their HRD level (driven by allele-specific LOH and clonality) and receptor status, both clinically evaluable biomarkers. These findings have immediate implications for the stratification of patients with BRCA1/2 mutation-associated breast cancer for checkpoint blockade therapy. Citation Format: Adam A. Kraya, Kara N. Maxwell, Bradley Wubbenhorst, Brandon M. Wenz, John Pluta, Andrew J. Rech, Nicole Lunceford, Amanda Barrett, Nandita Mitra, Jennifer J.D. Morrissette, Anupma Nayak, Michael Feldman, Susan M. Domchek, Robert H. Vonderheide, Katherine L. Nathanson. Homologous recombination deficiency negatively predicts for immune infiltration and antitumor immune activity in breast tumors with BRCA1/2 alterations [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A22.

SYK expression level distinguishes control from BRCA1-mutated lymphocytes.

BackgroundAbout 5%–10% of breast cancer and 10%–15% of ovarian cancer are hereditary. BRCA1 and BRCA2 are the most common germline mutations found in both inherited breast and ovarian cancers. Once these mutations are identified and classified, a course of action to reduce the risk of developing either ovarian or breast cancer – including surveillance and surgery – is carried out.PurposeThe purpose of the current research is to characterize the gene expression differences between healthy cells harboring a mutation in BRCA1/2 genes and normal cells. This will allow detection of candidate genes and help identify women who carry functional BRCA1/2 mutations, which cannot always be detected by the available sequencing methods, for example, carriers of mutations found in regulatory sequences of the genes.Materials and methodsOur cohort consisted of 50 healthy women, of whom 24 were individuals with BRCA1 or BRCA2 heterozygous mutations and 26 were non-carrier controls. RNA purified from non-irradiated lymphocytes of nine BRCA1/2 mutation carriers versus four control mutation-negative individuals was utilized for RNA-Seq analysis. The selected RNA-Seq transcripts were validated, and the levels of spleen tyrosine kinase (SYK) mRNA were measured by using real-time quantitative polymerase chain reaction.ResultsDifferences in gene expression were found when comparing untreated lymphocytes of BRCA1/2 mutation carriers and controls. Among others, the SYK gene was identified as being differently expressed for BRCA1/2 mutation carriers. The expression level of SYK was significantly higher in untreated healthy lymphocytes of BRCA1 heterozygote carriers compared with controls, regardless of irradiation. In contrast to normal tissues, in cancerous breast tissues, the expression levels of the BRCA1 and SYK genes were not intercorrelated.ConclusionCollectively, our observations demonstrate that SYK may prove to be a good candidate for better diagnosis, treatment, and prevention of BRCA1 mutation-associated breast cancer.

Abstract MS1-2: New clinical approaches for TNBC

Abstract Over the last decade, triple-negative breast cancer (TNBC) has been the subject of intense clinical investigation. Importantly, an improved understanding of the critical role of DNA damage repair deficiency in TNBC has led to effective therapeutic strategies to target BRCA1 and BRCA2 mutation-associated TNBCs with platinum chemotherapy agents and PARP inhibitors. A major area of increasing clinical relevance focuses on the treatment of BRCA1 and BRCA2 mutation-associated breast cancers after the development of resistance to platinum and PARP inhibitor therapy. Lurbinectedin, a novel marine derived DNA damaging agent, has shown activity in BRCA1 and BRCA2 mutation-associated cancers, including those with platinum resistance. While therapeutic strategies for TNBC patients with BRCA1 and BRCA2 mutations have increased, most TNBC patients lack an underlying germline mutation in these genes and continue to have high unmet clinical need. Multiple lines of investigation are currently underway. Androgen receptor (AR) blockade has shown preliminary proof-of-concept in AR expressing TNBCs. While monotherapy with PD-1/PD-L1 checkpoint inhibitors has shown modest activity in metastatic TNBC, multiple studies are exploring the role of these agents in combination with chemotherapy, targeted therapies and other immunotherapeutic agents. Given the high prevalence of TP53 mutations in TNBC, strategies to target additional cell cycle checkpoints including ATR, ATM, Wee1 and others may hold promise. Antibody-drug conjugates targeting Trop-2, LIV-1 and GPNMB expressing TNBCs have also shown clinical activity and are advancing in clinical development. Citation Format: Telli M. New clinical approaches for TNBC [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr MS1-2.

Homologous recombination deficiency (HRD) status predicts response to standard neoadjuvant chemotherapy in patients with triple-negative or BRCA1/2 mutation-associated breast cancer.

Defects in the homologous recombination (HR) DNA repair pathway sensitize tumors to therapeutics that target this pathway. A significant proportion of triple-negative breast cancers (TNBC) carry HR defects. The HRD assay is highly associated with sensitivity to neoadjuvant platinum-based chemotherapy in TNBC. Standard chemotherapy consists of some combination of an anthracycline, cyclophosphamide, and taxane. This study assesses the association of HR deficiency status with response to standard neoadjuvant chemotherapy in TNBC or BRCA1/2 mutation-associated breast cancer. Tumor samples were retrospectively obtained from 45 TNBC patients and 2 BRCA1/2 mutant, hormone receptor-positive/HER2-negative breast cancer patients who received anthracycline- and/or taxane-based neoadjuvant chemotherapy at Stanford University or Cedars-Sinai Medical Centers. The HRD score and tumor BRCA1/2 mutation status were determined from baseline tumor biopsies. HR deficient tumors were those with a HRD score of ≥ 42 or a tumor BRCA1/2 mutation. Response was categorized by the residual cancer burden (RCB) index. HR deficient patients were more likely to achieve a pathologic complete response (pCR) compared with non-deficient patients (OR 13.06, CI 1.52-11.241, p=0.0028). Among BRCA1/2 mutation wild-type patients, HR deficient patients were more likely to achieve a pCR (OR 16, 95% CI 1.65-160.41, p=0.0041) compared with HR non-deficient patients. Further, HRD scores were highly concordant pre- and post-therapy (Spearman correlation>99%). HR deficiency status is significantly associated with response to standard neoadjuvant chemotherapy in TNBC. This observation is consistent with the mechanisms of action of doxorubicin and cyclophosphamide as DNA damaging agents.