Clinical and Pathological Characteristics and Treatment Implications of BRCA1- and BRCA2-Mutated Breast Cancer in Japanese Patients: A Single-Institution Retrospective Study

Background: Approximately 5-10% of all breast cancers are hereditary and the majority of these arise due to germline mutations in the BRCA1 and BRCA2 tumour suppressor genes. BRCA1 is involved in multiple cellular pathways including DNA damage signalling, DNA repair, cell cycle regulation, protein ubiquitination, chromatin remodelling, transcriptional regulation and apoptosis. Several distinct pathological features can be used to estimate the likelihood of the presence of a BRCA1 mutation, however, it is not yet possible to fully categorise a BRCA1 mutated tumour. BRCA1-associated breast cancers are generally defined as being ER (Estrogen Receptor) negative and indeed triple negative for ER, PR and HER2. However, approximately 10-36% of BRCA1 mutated breast cancers are, in fact, ER positive. These tumours less frequently demonstrate the characteristics more commonly associated with BRCA 1 -associated breast cancers. Initial molecular evidence also suggests that there is heterogeneity within BRCA1-associated breast tumours and this is dependent on the presence or absence of the estrogen receptor. The aims of this study are to investigate the underlying biology of BRCA1-mutated (ER positive) and BRCA1-mutated (ER negative) breast tumours. Methods: Extensive gene expression profiling and data analysis was performed on a cohort of 70 FFPE (Formalin Fixed Paraffin Embedded) derived BRCA1 mutated breast tumours and matched sporadic controls using the ALMAC Breast Cancer DSA™ research tool. Within this dataset we have generated molecular profiles of: (1) BRCA 1 -mutated ER positive and (2) BRCA1-mutated ER negative breast cancer. Functional analysis was performed using DAVID and METACORE. Validation of gene targets was performed by qRT-PCR and Western blotting. Results: A list of differentially expressed transcripts was derived from the comparison of 35 BRCA1 mutant breast tumours and 35 matched sporadic controls. Further analysis based on the presence and absence of ER identified a set of transcripts defining BRCA1-mutated (ER positive) and BRCA1-mutated (ER negative) breast cancer. Functional analysis of these two datasets has identified the main pathways and processes that are deregulated. Specifically, BRCA1-deficiency in the absence of ER was associated with deregulation of pathways implicated in immune response whereas BRCA 1 deficiency in the presence of ER was associated with pathways implicated in cell adhesion and cytoskeletal remodelling. Validation of the key genes underlying these two BRCA1-deficient breast cancer subtypes has been performed. Discussion: This approach has revealed significant heterogeneity within BRCA1 mutated breast cancer based on the presence or absence of ER. Significant differences in the transcripts and molecular processes underlying BRCA1-mutated (ER positive) and BRCA1-mutated (ER negative) breast tumours have been identified. The ability to identify BRCA 1 -deficiency by gene expression profiling from FFPE derived breast tissue may also have significant clinical application. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-14.

Inhibited, trapped or adducted: the optimal selective synthetic lethal mix for BRCAness

PARP inhibitor and chemotherapy combination trials for the treatment of advanced malignancies: does a development pathway forward exist?

Background: Individuals with an inherited BRCA1 or BRCA2 (BRCA) mutation have an elevated risk of developing breast and ovarian cancer, and this BRCA defect is also present in a subset of sporadic tumors. Tumors do not have homologous recombination repair (HRR) to repair double-stranded breaks (DSBs), but they still can use other DNA repair pathways to survive. Therefore, we hypothesized that crosstalk between DNA repair pathways complements HRR in BRCA-deficient cells, leading to tumor survival. Treatment with either a poly(ADP)ribose polymerase (PARP) inhibitor (PARPi) or a platinum drug induced BRCA-deficient cell lethality by different mechanisms. In addition, combining both drugs has been reported to be synergistic in BRCA mouse models. However, the mechanism of this synergism and whether this synergism occurs in human cells are still unclear. Moreover, not all the patients respond to a PARPi chemotherapy alone. Hence, our objectives were: 1) to study the mechanism by which a PARPi combined with a platinum drug is synthetic lethal in human BRCA1 or BRCA-deficient cells; 2) to assess PARP activity as a biomarker for chemosensitivity. Methods: We compared the cytotoxic effect of ABT-888 (a PARPi) with cisplatin or carboplatin (platinum drugs) alone versus combinations by examining Brca-proficient and -deficient mouse embryonic stem (ES) cell survival using clonogenic assays. The effect of ABT-888 and carboplatin combination treatment on human cell growth was tested in HCC1937 (a triple negative BRCA1-deficient breast cancer line) and EUFA423F (a BRCA2-deficient Fanconi anemia cell line), along with their BRCA complemented lines. Synergism, antagonistic or additive drug interactions were assessed. Drug(s)-induced DSBs, HRR and apoptosis were examined and endogenous PARP activity was determined. Results: Each monotherapy killed or inhibited more Brca/BRCA-deficient cells than the corresponding Brca/BRCA-proficient cells. In Brca-deficient cells, the ABT-888 and carboplatin combination was more synergistic than ABT-888 and cisplatin. All paired BRCA-deficient or complemented cells had the same level of DNA damage following treatment with ABT-888 and/or Carboplatin. BRCA-deficient cells lack HRR, while BRCA-proficient cells use HRR. Failure to repair DSBs in BRCA-deficient cells triggered apoptosis, which was synergistic in the BRCA1-deficient cells. Moreover, higher endogenous PARP activity in Brca/BRCA-deficient cells than their respective Brca/BRCA proficient cells correlated with increased chemosensitivity. Conclusion: Our data suggest that combining ABT-888 and carboplatin will likely be more successful than monotherapy in treating most BRCA-associated cancers. In addition, high endogenous PARP activity could be used as a marker to identify PARPi susceptible tumors. Lack of HRR combined with a strong dependence on PARP activity for repair of platinum lesions led to synthetic lethality in BRCA-deficient cells. A randomized phase II trial has recently been initiated to test this drug combination in patients with BRCA-associated breast cancer and we are currently investigating γH2AX as a pharmacodynamic marker in hair follicles. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A102.

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

Germline mutations at BRCA1 or BRCA2 genes result in susceptibility to breast and ovarian cancers. BRCA1- and BRCA2-associated tumors have distinct histologic and molecular phenotypes, as compared to sporadic breast tumors. Typically, a higher grade of malignancy is observed in BRCA-associated cancers. A number of studies have suggested that BRCA1 and BRCA2 proteins are of importance in DNA repair and maintenance of genome integrity, bringing about molecular models of tumor pathogenesis. In particular, alterations at p53 gene have been suggested to be a necessary step in the tumorigenesis of BRCA-associated carcinomas. In fact, BRCA-associated breast cancers have higher p53 mutation frequencies than sporadic ones. At present, very little is known regarding BRCA non-associated familial tumors (termed BRCAx tumors). To our knowledge no data is available on p53 alterations in this sub-group of familial tumors. In this study p53 alteration frequencies were evaluated in 13 BRCA1, 11 BRCA2 and 55 BRCAx breast tumors. Tumor samples were analyzed for p53 gene mutations by PCR-SSCP/direct sequencing, and for p53 protein overexpression by immunohistochemistry (IHC). Altogether, p53 alterations were detected in 54% of BRCAI tumors compared with 5% of BRCAx tumors. No p53 alteration was found in BRCA2 tumors. While loss of p53 checkpoint control is likely to be an important step in the molecular pathogenesis of BRCA1-associated cancers, our data seem to indicate a p53-independent molecular mechanism underlying BRCAx neoplastic transformation.

Introduction: BRCA1 or 2 (BRCA) germline mutations cause increased risks of breast and ovarian cancers. Therefore, preoperative BRCA testing could influence surgical strategies and preventive interventions for breast cancer patients with BRCA mutations. In Japan, BRCA genetic testing and risk-reducing surgeries became eligible for national health insurance coverage in 2020, previously conducted as costly private healthcare. When Japanese national insurance coverage is approved, patients' out-of-pocket expenses are reduced to 30% or less. This study aimed to investigate the impact of preoperative BRCA genetic testing and national health insurance coverage on surgical decision-making and risk-reducing surgeries among Japanese populations. Methods:Japanese women with BRCA germline pathogenic mutations and early breast cancer who underwent definitive surgery from 2004 to 2024 were retrospectively identified from institutional databases at St. Luke’s International Hospital in Tokyo, Japan. Factors including clinicopathologic information and surgical decisions were analyzed. We assessed whether undergoing BRCA testing before or after breast cancer surgery influenced the choice of surgical procedures and risk-reducing surgeries. Additionally, we examined whether approval for national health insurance coverage affected these decisions. The chi-square test was used for statistical comparisons. Results: A total of 273 breast cancer patients with germline BRCA mutations were identified (BRCA1: 120, BRCA2: 153). Among them, 167 patients (61.2%) underwent BRCA testing prior to breast cancer surgery. Surgical treatments included breast-conserving surgery (BCS) for 78 patients (28.6%) and mastectomy for 195 patients (71.4%). Among the 167 patients who learned of their BRCA mutation before breast cancer surgery, while BCS was feasible for 113 patients based on preoperative imaging, 24 patients (21.2%) chose BCS, and 89 patients (78.8%) opted for mastectomy due to their mutation results. The breast-conserving rate was 14.4% for patients with preoperative BRCA testing compared to 50.9% for those tested after surgery (p<0.0001). Risk-reducing mastectomy (RRM) was performed in 115 patients (52.0%, excluding cases with bilateral breast cancers). Among patients with preoperative testing, 94 (63.1%) underwent RRM, including 83 (55.7%) who had RRM simultaneously with breast cancer surgery. Risk-reducing salpingo-oophorectomy (RRSO) was performed in 98 patients (61.3%, excluding cases with previous non-preventive oophorectomy), including 67 (41.9%) who had RRSO simultaneously with breast cancer surgery. Patients who learned of their BRCA mutation after breast cancer surgery were subsequently less likely to undergo risk-reducing surgeries compared to those with preoperative testing: 29.2% underwent RRM and 50.5% underwent RRSO (p=0.0001 and 0.097, respectively). Before national health insurance approval, 46.6% underwent preoperative BRCA testing, 28.0% underwent RRM, and 17.5% underwent RRSO simultaneously with breast cancer surgery. After approval, these rates increased to 86.9% for preoperative BRCA testing, 51.7% for RRM, and 43.0% for RRSO (p<0.0001, 0.0004, and <0.0001, respectively, compared between before and after approval). Conclusions: Most Japanese patients who learned of their BRCA mutation before their breast cancer surgery opted for mastectomy instead of BCS due to their mutation status. Preoperative BRCA testing and national health insurance coverage significantly increased the likelihood of undergoing risk-reducing surgeries. These findings emphasize the key role of preoperative BRCA testing and national health insurance coverage in informing surgical decisions and enhancing preventive care. Citation Format: Kumiko Kida, Junko Takei, Misato Suzuki, Megumi Okawa, Risa Kasahara, Asaka Wada, Yuka Kajiura, Fumi Akitani, Kyoko Shiota, Michiko Yamanaka, Atsushi Yoshida. Impact of Preoperative BRCA Testing and National Health Insurance Coverage on Surgical and Risk-reducing Decision-making in Japanese BRCA-mutated Breast Cancer Patients [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P1-01-12.

1542 Background: Individuals with germline BRCA1 or 2 mutations are at high risk for breast cancer; studies are ongoing to determine subgroups that may be at lower risk. For BRCA1, a trend of increasing risk has been associated with increasing downstream (3′) location of mutations compared to the upstream (i.e., 5’) mutations. For BRCA2, compared with no mutation, an increased risk of breast cancer has been associated with mutations outside of the “ovarian cancer cluster region” (OCCR). We sought to determine the mutation position in BRCA- associated breast cancers and whether there was a genotype-phenotype correlation. Methods: Patients with breast cancer with BRCA1 or 2 mutations were identified by a search of a prospectively maintained database at a major cancer center. BRCA mutation site, patient and tumor characteristics were determined through retrospective review. Results: One hundred and sixty patients with BRCA1-associated breast cancers and 102 patients with BRCA2-associated breast cancer were identified. Of 160 patients with BRCA1-associated cancers, 85 (53%) had mutations in the 5’ half of the gene. There was no difference in median age, tumor size, ER/PR status and nodal status between patients with 5’ vs. 3’ mutations. Of the 102 patients with BRCA2-associated breast cancers, 37 (36%) had OCCR mutations. There was no difference in median age, tumor size, ER/PR status and nodal status between patients with OCCR vs non-OCCR mutations. Conclusions: In this single institution study, over half of BRCA1-associated breast cancers and over a third of BRCA2-associated breast cancers were associated with putative lower risk mutation positions. Although we cannot exclude that patients with mutations in these regions have a lower relative risk for breast cancer, vigilance in cancer screening and prevention remains necessary. Further studies in genotype/phenotype correlation are needed to individualize cancer prevention strategies. No significant financial relationships to disclose.

Genetically engineered mouse models (GEMMs) of human cancer not only permit us to gain a detailed insight into the specific genetic changes that drive tumor development and metastasis but also provide powerful tools to study the mechanisms underlying drug response and acquired resistance. Once these processes are understood in sufficient detail, it may be possible to design combination therapies that not only cause complete remissions but also eliminate remnant cells that elicit recurrent disease. We have developed GEMMs of E-cadherin mutated lobular breast cancer. These mice develop mammary tumors that closely resemble the lobular morphology and the metastatic spectrum of the cognate tumors in humans. Using Sleeping Beauty (SB) transposon-based insertional mutagenesis in conditional E-cadherin mutant mice, we have found that heterozygous loss of MYH9 or overexpression of hyperactive truncated forms of MYPT1/2 and ASPP2 reduces actomyosin contractility and thereby promotes malignant transformation of E-cadherin-deficient mammary epithelial cells, resulting in ILC formation in mice. This work highlights actomyosin hypercontractility induced by E-cadherin loss as a critical barrier to ILC development. We have also developed several GEMMs for somatic modeling of BRCA1-mutated triple-negative breast cancer using intraductal injection of lentiviral vectors for stable overexpression of exogenous genes and CAS9-mediated disruption or APOBEC-CAS9n-UGI (BE3)-mediated base editing of endogenous genes. We have used these GEMMs to validate RB, PTEN, PIK3CA, MYC, and MCL1 as bona fide driver genes in BRCA1-associated breast cancer. Moreover, MCL1 inhibition potentiated the in vivo efficacy of the PARP inhibitor (PARPi) olaparib, underscoring the therapeutic potential of this combination for treatment of BRCA1-associated cancer patients with poor response to PARPi monotherapy. The BRCA1-deficient mammary tumors from our mouse models are characterized by genomic instability and hypersensitivity to DNA-damaging agents, including platinum drugs and PARP inhibitors. Nevertheless, none of these drugs are curative: tumors grow back after drug treatment and eventually become resistant. We found that PARPi resistance of BRCA1-deficient GEMM tumors can be induced by several mechanisms, including activation of drug efflux transporters, type of BRCA1 mutation, and loss of components of the 53BP1-RIF1-shieldin and CST complexes that govern end-protection of DNA double-strand breaks. Citation Format: Jos Jonkers. Genetic dissection of breast cancer development and therapy resistance in mouse models [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr IA18.

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

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

A distinct morphologic and molecular phenotype has been reported for BRCA1-associated breast cancers; however, the phenotype of BRCA2-associated breast cancers is less certain. To comprehensively characterize BRCA2-associated breast cancers we performed a retrospective case control study using tumors accrued through the Breast Cancer Family Registry. We examined the tumor morphology and hormone receptor status in 157 hereditary breast cancers with germline mutations in BRCA2 and 314 control tumors negative for BRCA1 and BRCA2 mutations that were matched for age and ethnicity. Tissue microarrays were constructed from 64 BRCA2-associated and 185 control tumors. Tissue microarray sections were examined for HER2/neu protein overexpression, p53 status and the expression of basal markers, luminal markers, cyclin D1, bcl2, and MIB1 by immunohistochemistry. The majority of BRCA2-associated tumors and control tumors were invasive ductal, no special-type tumors. In contrast to control tumors, BRCA2-associated cancers were more likely to be high grade (P<0.0001) and to have pushing tumor margins (P=0.0005). Adjusting for grade, BRCA2-associated tumors were more often estrogen receptor positive (P=0.008) and exhibited a luminal phenotype (P=0.003). They were less likely than controls to express the basal cytokeratin CK5 (P=0.03) or to overexpress HER2/neu protein (P=0.06). There was no difference in p53, bcl2, MIB1, or cyclin D1 expression between BRCA2-associated and control tumors. We have demonstrated, in the largest series of BRCA2-associated breast cancers studied to date, that these tumors are predominantly high-grade invasive ductal carcinomas of no special type and they demonstrate a luminal phenotype despite their high histologic grade.

268 Background: BRCA1 and -2 germ-line mutations are associated with increased risk of PAC; approximately 5% of all cases of PAC are estimated to be due to an inherited genetic mutation (Lynch, HT, et al. Pancreatology, 2001;1(5):466-471). Other BRCA-associated cancers have demonstrated increased sensitivity to platinum chemotherapy and PARP inhibitors (PARPi) with improved clinical outcomes compared to sporadic cases (J Clin Oncol, 2008 Dec 1;26(34):5530-6). Outcomes in BRCA-associated pancreatic cancer are unknown. Methods: Patients with a known BRCA1 or -2 mutation and a diagnosis of PAC were retrospectively identified from the MSKCC Familial Pancreas Cancer Registry and via institutional database review. Outcomes and clinical characteristics were reviewed. 7 patients (1 male) with BRCA2 mutation and PAC, 4 patients (1 male) with BRCA1 mutation and PAC, were identified. Two further cases of BRCA mutation and cholangiocarcinoma were identified. Results: See Table for patient demographics. Treatment for advanced disease included a PARP inhibitor (PARPi) in 2 cases; both pts had a radiologic partial response (PR) to therapy. Five patients received platinum-based chemotherapy for advanced disease, 4 of whom had a PR. Median survival for all patients was 27.6 months. Conclusions: The use of platinum- containing chemotherapy, radiation therapy, and PARPi to target the BRCA-associated defective DNA repair mechanism is deserving of further investigation in these patients. PARPi have demonstrated promising efficacy in patients with BRCA-mutated breast and ovarian cancer and are undergoing prospective evaluation in PAC. Genetic testing in patients presenting with a personal history or strong family history of BRCA associated cancers may help to guide choice of therapy. [Table: see text] No significant financial relationships to disclose.

This study evaluated the free to total serum prostate specific antigen (f/t PSA) ratio and prostate specific antigen density (PSAD) in detecting prostate cancer in Japanese males with a PSA level between 2.5 and 20.0 ng/mL in a community-based urology practice. Twenty-six patients with clinically localized prostate cancer and 44 patients with histologically-proven benign prostatic hyperplasia (BPH) were studied. The serum levels of free PSA (fPSA) and total (t) PSA were determined using a chemiluminescent enzyme immunoassay. The f/t PSA ratio was calculated by dividing the fPSA value by the total PSA value and was compared with the PSA and PSAD via the receiver operating characteristic (ROC) curves. Patients with prostate cancer had a significantly lower f/t PSA ratio than patients with BPH. The PSAD was a superiordiagnostic tool over PSA (P< 0.01) when analyzed by ROC curves. The f/t PSA ratio was also superior to PSA, but lacked significance (P=0.12), and similarly, the PSAD was superior, but not significant, to the f/t PSA ratio. Using a cut-off value of 0.19, the PSAD had a sensitivity of 81% and a specificity of 82%. With a cut-off value of 14.0%, the f/t PSA ratio had a sensitivity of 81% and a specificity of 66%. This study showed that PSAD alone improved cancer detection significantly better than PSA. However, it is still unclear whether the f/t PSA ratio is superior to PSA or PSAD in the discrimination between BPH and prostate cancer in Japanese male patients.

Poly (ADP-ribose) polymerase (PARP) inhibitors have been approved for the treatment of germline BRCA1/2-mutated metastatic breast cancer. BRCA-associated breast cancer is associated with younger age of patients, aggressive course and higher risk of recurrence. Mutations in the BRCA genes result in loss of function of BRCA proteins. The last ones are essential in DNA repair, cell cycle control and genomic stability. In these cells, repair of double-strand DNA breaks through homologous recombination is disrupted. As a consequence, tumors with mutations in the BRCA genes are highly sensitive to DNA-damaging agents, such as platinum agents and PARP inhibitors. The recent OlympiA trial has demonstrated better disease-free and overall survival after adjuvant therapy with olaparib in high-risk HER2-negative BRCA-associated early breast cancer (EBC). It is expected that PARP inhibitors will be valuable for the treatment of EBC. In this article, we review recent clinical data and ongoing trials, as well as discuss the prospects of PARP inhibitors.