Breast Cancer Develop Brain Metastases Research Articles

Cancer–stromal cell interactions in breast cancer brain metastases induce glycocalyx-mediated resistance to HER2-targeting therapies

Brain metastatic breast cancer is particularly lethal largely due to therapeutic resistance. Almost half of the patients with metastatic HER2-positive breast cancer develop brain metastases, representing a major clinical challenge. We previously described that cancer-associated fibroblasts are an important source of resistance in primary tumors. Here, we report that breast cancer brain metastasis stromal cell interactions in 3D cocultures induce therapeutic resistance to HER2-targeting agents, particularly to the small molecule inhibitor of HER2/EGFR neratinib. We investigated the underlying mechanisms using a synthetic Notch reporter system enabling the sorting of cancer cells that directly interact with stromal cells. We identified mucins and bulky glycoprotein synthesis as top-up-regulated genes and pathways by comparing the gene expression and chromatin profiles of stroma-contact and no-contact cancer cells before and after neratinib treatment. Glycoprotein gene signatures were also enriched in human brain metastases compared to primary tumors. We confirmed increased glycocalyx surrounding cocultures by immunofluorescence and showed that mucinase treatment increased sensitivity to neratinib by enabling a more efficient inhibition of EGFR/HER2 signaling in cancer cells. Overexpression of truncated MUC1 lacking the intracellular domain as a model of increased glycocalyx-induced resistance to neratinib both in cell culture and in experimental brain metastases in immunodeficient mice. Our results highlight the importance of glycoproteins as a resistance mechanism to HER2-targeting therapies in breast cancer brain metastases.

Brain metastasis-associated fibroblasts secrete fucosylated PVR/CD155 that induces breast cancer invasion

Brain metastasis cancer-associated fibroblasts (bmCAFs) are emerging as crucial players in the development of breast cancer brain metastasis (BCBM), but our understanding of the underlying molecular mechanisms is limited. In this study, we aim to elucidate the pathological contributions of fucosylation (the post-translational modification of proteins by the dietary sugar L-fucose) to tumor-stromal interactions that drive the development of BCBM. Here, we report that patient-derived bmCAFs secrete high levels of polio virus receptor (PVR), which enhance the invasive capacity of BC cells. Mechanistically, we find that HIF1α transcriptionally upregulates fucosyltransferase 11, which fucosylates PVR, triggering its secretion from bmCAFs. Global phosphoproteomic analysis of BC cells followed by functional verification identifies cell-cell junction and actin cytoskeletal signaling as modulated by bmCAF-secreted, -fucosylated PVR. Our findings delineate a hypoxia- and fucosylation-regulated mechanism by which bmCAFs contribute to the invasiveness of BCBM in the brain.

A phase 1, open-label, first-in-human study of TAS2940 in patients with advanced solid tumors.

TPS3165 Background: Aberrant expression and signaling of the ERBB family of receptor tyrosine kinases, including epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2), has a role in the pathogenesis of solid tumors such as breast cancer (BC), non–small cell lung cancer (NSCLC), and glioblastoma (GBM). Although therapies that target HER2 are effective in early and advanced HER2-overexpressing BC, many patients develop resistance despite tumor dependence on HER2 at the time of progression. Approximately 4% of patients with NSCLC have HER2 mutations, mostly presenting as exon 20 insertions (ex20ins); however, approved HER2/EGFR tyrosine kinase inhibitors (TKIs) have limited efficacy in patients with NSCLC and HER2 ex20ins. Many patients with NSCLC or BC develop brain metastases, and EGFR alterations, including EGFRvIII mutations, are common in GBM. There is therefore a need for a brain-penetrable TKI with activity against tumors harboring HER2/EGFR alterations. TAS2940 is a potent, selective, and orally bioavailable pan-ERBB inhibitor that has shown promising preclinical efficacy against cancers with a variety of HER2/EGFR mutations and amplifications. Further, TAS2940 inhibited tumor growth and induced tumor regression in a dose-dependent manner in nude mice intracranially implanted with NCI-N87, a HER2-overexpressing human gastric cancer cell line. Methods: TAS2940-101 (NCT04982926) is an open-label, phase 1, first-in-human trial to evaluate the safety, tolerability, pharmacokinetics (PK), and preliminary antitumor activity of TAS2940 in patients with advanced solid tumors and HER2/ EGFR aberrations. Eligible patients are aged ≥18 years, have non-measurable (Part 1) or measurable (Part 1 and 2) disease per RECIST 1.1 or RANO criteria, ECOG performance status 0/1, and adequate organ function. Patients with non-stable brain metastases are excluded. Part 1 (dose escalation) will use a Bayesian optimal interval design with a starting dose of 15 mg/kg orally QD (planned dose levels: 15, 30, 60, 120, 240 and 480 mg). Once the recommended phase 2 dose is determined, Part 2 (dose expansion) will enroll patients with NSCLC (Cohort A), HER2+ BC (Cohort B), recurrent/refractory GBM (Cohort C), or other solid tumors with EGFR/ HER2 aberrations (Cohort D). The primary objectives are the maximum tolerated dose of TAS2940 in Part 1 and antitumor activity in Part 2. Secondary objectives include antitumor activity in Part 1. The safety and PK profile of TAS2940 will be assessed in both parts. Approximately 142 patients will be enrolled, comprising ~42 in Part 1 and ~100 in Part 2. As of January 24, 2023, 15 patients have been enrolled. No dose-limiting toxicities have been reported with dose escalation up to 240 mg QD. Recruitment is ongoing. Clinical trial information: NCT04982926 .

An Immunohistochemical Study of Breast Cancer Brain Metastases: The Role of CD44 and AKT in the Prognosis.

Breast cancer is a major health burden, and up to one-third of patients with breast cancer develop brain metastases, which are linked to a very poor prognosis. Few biomarkers are available to predict the prognosis of patients with metastases. Assessment by immunohistochemistry may be used as a tool to predict the behavior of these tumors. A retrospective transversal study including 114 patients (diagnosed between 2000 and 2016) with breast cancer brain metastases was carried out using archival biological material from 114 patients with breast cancer brain metastases. Expression of CD44, HER2, ER, PR, CA9, PDL-1, CD133, ALDH1, PTEN, AKT, PI3K, and AR markers was assessed by immunohistochemistry. The overexpression of CD44 and AKT was associated with worse overall survival ( P =0.047 and P =0,034, respectively), on univariate analysis, in the cohort of parenchymal and bone metastases; the impact of AKT expression was also evident in the parenchymal cohort on uni ( P =0.021) and multivariate analysis ( P =0.027). The remaining markers did not exhibit a statistical correlation. Immunohistochemistry markers such as CD44 and AKT may have a prognostic impact on survival in patients with breast cancer brain metastases. The conjugation with other markers may help with the stratification of patients and therapy.

Characteristics of patients with brain metastases from human epidermal growth factor receptor 2-positive breast cancer: subanalysis of Brain Metastases in Breast Cancer Registry

BackgroundUp to 40% of patients with metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer develop brain metastases (BMs). Understanding of clinical features of these patients with HER2-positive breast cancer and BMs is vital.Patients and methodsA total of 2948 patients from the Brain Metastases in Breast Cancer registry were available for this analysis, of whom 1311 had primary tumors with the HER2-positive subtype.ResultsPatients with HER2-positive breast cancer and BMs were—when compared with HER2-negative patients—slightly younger at the time of breast cancer and BM diagnosis, had a higher pathologic complete response rate after neoadjuvant chemotherapy and a higher tumor grade. Furthermore, extracranial metastases at the time of BM diagnosis were less common in HER2-positive patients, when compared with HER2-negative patients. HER2-positive patients had more often BMs in the posterior fossa, but less commonly leptomeningeal metastases. The median overall survival (OS) in all HER2-positive patients was 13.2 months (95% confidence interval 11.4-14.4). The following factors were associated with shorter OS (multivariate analysis): older age at BM diagnosis [≥60 versus <60 years: hazard ratio (HR) 1.63, P < 0.001], lower Eastern Cooperative Oncology Group status (2-4 versus 0-1: HR 1.59, P < 0.001), higher number of BMs (2-3 versus 1: HR 1.30, P = 0.082; ≥4 versus 1: HR 1.51, P = 0.004; global P = 0.015), BMs in the fossa anterior (HR 1.71, P < 0.001), leptomeningeal metastases (HR 1.63, P = 0.012), symptomatic BMs at diagnosis (HR 1.35, P = 0.033) and extracranial metastases at diagnosis of BMs (HR 1.43, P = 0.020). The application of targeted therapy after the BM diagnosis (HR 0.62, P < 0.001) was associated with longer OS. HER2-positive/hormone receptor-positive patients showed longer OS than HER2-positive/hormone receptor-negative patients (median 14.3 versus 10.9 months; HR 0.86, P = 0.03), but no differences in progression-free survival were seen between both groups.ConclusionsWe identified factors associated with the prognosis of HER2-positive patients with BMs. Further research is needed to understand the factors determining the longer survival of HER2-positive/hormone receptor-positive patients.

P16INK4A-deficiency predicts response to combined HER2 and CDK4/6 inhibition in HER2+ breast cancer brain metastases

Approximately 50% of patients with metastatic HER2-positive (HER2+) breast cancer develop brain metastases (BCBMs). We report that the tumor suppressor p16INK4A is deficient in the majority of HER2+ BCBMs. p16INK4A-deficiency as measured by protein immunohistochemistry predicted response to combined tucatinib and abemaciclib in orthotopic patient-derived xenografts (PDXs) of HER2 + BCBMs. Our findings establish the rationale for a biomarker-driven clinical trial of combined CDK4/6- and HER2-targeted agents for patients with HER2 + BCBM.

Antiproliferative Effects of Olanzapine against MCF-7 Cells and Its Molecular Interactions with Survivin

Background: Epidemiologic findings revealed approximately one-third of patients with breast cancer develop brain metastases. Recent research has found that schizophrenia patients who take antipsychotic medications on a long-term basis have a decreased risk of cancers than normal individuals. This serendipitous anticancer action of antipsychotic medications is now being investigated by many studies. The ability of these drugs to penetrate the blood–brain barrier may target brain metastases. We investigated antiproliferative activity of antipsychotic drug. The present study aimed to determine the antiproliferative effects of olanzapine against MCF-7 cells and also to examine its molecular interactions with survivin. Methods: The antiproliferative effects of olanzapine were demonstrated using MTT assay and molecular interactions were analyzed using AutoDock Vina ver4.0 between olanzapine (PubChem CID − 135398745) and survivin (PDB ID − 1E31). These molecular interactions were also compared with tamoxifen (PubChem CID: 2733526). Results: We found that olanzapine has extensive antiproliferative effects against MCF-7 human breast cancer cells, with an IC50 of 10.9 g/mL. We also discovered that olanzapine had possible interactions with the survivin protein at Lys15, Phe86, and Val89 amino acid residues, which could be related to effects of olanzapine on MCF-7 cell viability. Conclusion: Our research establishes that olanzapine has promising anticancer properties against breast tumors, with prospective application to target brain metastases in patients with breast cancer.

Overview of Patients with Metastatic Brain Tumors from Breast Cancer at H. Adam Malik Hospital, Medan in 2017-2021

Abstract&#x0D; Introduction: The incidence of breast cancer based on Globocan in 2018, reached 2,088,849 cases (11.6%), with a mortality rate of 626,679 cases (6.6%). Breast cancer is one of the most common causes of a metastatic brain tumor. Approximately 10%-16% of patients with breast cancer develop brain metastases during the course of their disease. Current case management guidelines for patients with metastatic brain tumors from breast cancer are radiotherapy to the entire brain, with or without surgical resection, or stereotactic radiosurgery. Hormone receptor ([HR]; estrogen receptor [ER], progesterone receptor [PR]) and HER2 expression serve as predictors of response to hormone-targeted therapy and HER2, respectively.&#x0D; Method: The study was a descriptive study with a retrospective cohort design in which the researchers identified 78 patients with breast cancer brain metastases (either for diagnostic purposes or for therapeutic purposes at RSUP HAM Medan between 2017 and 2021. Data were collected from SIRS RSUP HAM Medan. Data related to clinicopathology were collected from medical records, including demographic characteristics, tumor characteristics, biomarker status, recurrence of metastatic brain tumors based on Magnetic Resonance Imaging (MRI) examination, and data on therapeutic regimens in cases of brain metastases of breast cancer. ER and PR status were determined by immunohistochemical examination. the intensity of the HER2 3+ immunohistochemical staining was considered positive&#x0D; Result: The mean age at breast cancer diagnosis was 46 years (range: 24-73 years). Most patients had invasive ductal histology (n=73, 94%). In addition, 56% of patients had T3 (n=34) T4 disease in 56% of patients (n=44) and 68% of patients (n=53) had positive axillary lymph nodes. Among patients with known HR and HER2 status, a total of 56% of tumors were ER negative (ER-; n=44), 62% were PR negative (n=48), and 44% were HER2-positive (HER2+; n= 34). With regard to the four subtypes formed by the combined values of HR and HER2 status, 21% (n=16) of tumors were HR+HER2+, 27% (n=21) were HR+HER2-, 23% (n=18) were HR+/ HER2-, and 28% (n=23) were triple negative (TN).&#x0D; Discussion: In the current study, investigators found that apart from patient age and number of brain metastases, HER2 status was a strong predictor of survival outcome after brain metastases. Patients with HER2-positive characteristics had a longer life expectancy than patients with HER2-negative disease. Considering the intracranial antitumor effect of anti-HER2 therapy, it is important to establish HER2 status not only in primary tumors but also in brain metastases to aid in consideration of the choice of therapeutic modality&#x0D; Conclusion: This study showed that younger age, brain metastases from solitary breast cancer, and HER2 positive from breast tumors were independent predictors of better survival in patients with breast cancer brain metastases

Abstract 337: p16INK4A-deficiency predicts for response to combined HER2 and CDK4/6 inhibition in HER2+ breast cancer brain metastases

Abstract Approximately 50% of patients with metastatic HER2-positive (HER2+) breast cancer develop brain metastases (BCBMs). To identify predictors of response and resistance to brain-penetrant, small molecule targeted therapies, we performed whole exome sequencing, RNAseq and quantitative immunohistochemistry of HER2+ BCBM tissues from 21 patients. We found that the tumor suppressor p16INK4A (p16) was deficient in the majority of HER2+ BCBMs. Orthotopic HER2+ BCBM patient-derived xenograft (PDX) models with p16 deficiency were resistant to the brain-penetrant HER2 inhibitor, tucatinib or the brain penetrant CDK4/6 inhibitor, abemaciclib, when used as single agents. However, p16-deficiency predicted response to combined tucatinib and abemaciclib in orthotopic HER2+ BCBM PDX models. These data establish the rationale for a biomarker-driven clinical trial of combined CDK4/6- and HER2-targeted agents for patients with HER2+ BCBM. Citation Format: Jing Ni, Sheheryar Kabraji, Shaozhen Xie, Yanzhi Wang, Peichen Pan, Xiaofang He, Zongming Liu, Henry Long, Myles Brown, Eric P. Winer, Deborah Dillon, Nancy Lin, Jean Zhao. p16INK4A-deficiency predicts for response to combined HER2 and CDK4/6 inhibition in HER2+ breast cancer brain metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 337.

Abstract LB139: VRN10, Discovery of Potent Irreversible HER2 Kinase Inhibitors with Intracranial Activity

Abstract Human epidermal growth factor receptor 2 (HER2) amplification is one of oncogenic drivers most found in breast cancer but also occurs in multiple other tumor types. Approximately 10-30% of patients with breast cancer develop brain metastases (BCBM), a devastating cause of morbidity and mortality. To address this unmet medical need, VRN10s, brain penetrant, orally bioavailable, and irreversible small molecule inhibitors were designed to target HER2 while sparing EGFR wild type. In biochemical assays VRN10s had low nanomolar potency to inhibit catalytic activity of HER2. In cell viability assays using HER2+ breast and gastric cancer cell lines, VRN10s inhibited proliferation with single-digit nanomolar potency and exhibited an exceptional selectivity for HER2 over EGFR, with an enhancement of &amp;gt; 30-fold. Neuregulin-1 (NRG-1) has been suggested to decrease the anti-tumor activity of HER2 kinase inhibitors by induction of HER3 in brain microenvironment. Two FDA-approved HER2 kinase inhibitors tucatinib and lapatinib are not only less brain permeable, but they also show significantly decreased activity in the presence of NRG-1. However, the addition of NRG-1 did not rescue the proliferation of HER2+ breast cancer cell lines treated with VRN10s. Western blot confirmed that VRN10s inhibit signal transduction downstream of HER2 and HER3 through the AKT and ERK pathways. Inhibition of HER2 is reported to cause cytotoxicity on cardiomyocytes. In spite of potent inhibition of HER2 catalytic inhibition, VRN10s did not show cardiomyocyte cytotoxicity more than other HER2 kinase inhibitors, including tucatinib and neratinib. We confirm VRN10s to have high brain exposure in several preclinical models. Consistent with our in vitro results, potent activity was observed in the xenograft and intracranial models using once daily oral administration with strong tumor growth inhibition. Based on in vitro assay, brain permeability and in vivo efficacy, VRN10s may be promising therapeutic candidates for patients with HER2+ tumors including BCBM. Citation Format: Hwan Kim, Younho Lee, Jinhee Park, Youngyi Lee, Jieun Choi, Jihye Yoo, Chanmi Park, Somi Lee, Eunhwa Ko, Jung Beom Son, Hwan Geun Choi, Nam Doo Kim, Daekwon Kim, Sunghwan Kim. VRN10, Discovery of Potent Irreversible HER2 Kinase Inhibitors with Intracranial Activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB139.

SOX2 Promotes Brain Metastasis of Breast Cancer by Upregulating the Expression of FSCN1 and HBEGF

The prognosis of breast cancer brain metastasis (BCBM) is extremely poor due to its resistance to conventional therapy. Elucidation of the molecular mechanisms of BCBM could contribute to the development of new therapeutic targets. In this study, we isolated RNA samples from primary breast cancer or BCBM, and then performed mRNA profiling. We determined that SOX2 is associated with the occurrence of BCBM and could be a predictor of BCBM. High levels of SOX2 were significantly associated with decreasing BCBM-free survival in patients. Overexpression of SOX2 in breast cancer cells enhanced cancer cell adhesion to brain microvascular endothelial cells, transendothelial migration, and in vitro blood-brain barrier (BBB) migration, whereas silencing SOX2 inhibited these events. SOX2 can increase cancer cell migration and BBB permeability by upregulating FSCN1 and HBEGF, thereby promoting BBB migration of breast cancer cells. Moreover, high levels of FSCN1 and HBEGF were significantly associated with reducing BCBM-free survival in breast cancer patients. Further study indicated that SOX2 mediates the expression of HBEGF and FSCN1 by activating AKT and β-catenin signaling pathways. Additionally, in vivo experiments showed that SOX2 promotes the development of BCBM. This study demonstrated that SOX2 promotes BCBM by upregulating the expression of FSCN1 and HBEGF.

Prognosis and Treatment Outcomes of Patients Undergoing Resection of Brain Metastases from Breast Cancer.

Brain metastases from breast cancer have poor prognosis and are a challenge to treat. Multiple treatment options are available. Descriptive and prognostic data on breast cancer brain metastases is limited. This study analyzed clinical data of patients who underwent surgical resection of one or more brain metastases. Histological and clinical characteristics, as well as treatment modalities, were analyzed. Initial tumor stage or grade was found not to correlate with the median time to developing brain metastases or survival. Human epidermal growth factor receptor 2 (HER2)-positive status was not associated with shorter median time to developing brain metastases. No correlation was found between the number of brain metastases and patient outcome. Results confirm the survival benefit of surgical resection with or without irradiation. Data showed that patients with HER2-positive and those with triple-negative breast cancer develop brain metastases at lower stages but not earlier after diagnosis, and survival is mostly dependent on treatment modality rather than histological subtype.

Abstract OT3-10-02: A breast cancer trainees research collaborative group prospective study of treatment and outcomes related to central nervous system disease secondary to breast cancer in the United Kingdom

Abstract Introduction: Breast cancer brain metastasis (BCBM) is a particular feature of HER2-positive and triple negative breast cancer (BC) and is becoming more common. This reflects the improved survival of patients living with metastatic breast cancer as well as increased cross-sectional imaging of the central nervous system with magnetic resonance imaging (1). The development of BCBM on the background of adequately controlled extracranial disease is an increasingly prevalent clinical scenario. BCBM causes significant morbidity and mortality; unfortunately the efficacy of systemic treatment is extremely limited and, at present, no systemic therapies are specifically approved for the treatment of BCBM (2). Basic and translational research to understand the pathophysiology of BCBM remains limited by a lack of access to annotated clinical material. Such research is needed if preventative and novel treatment strategies are to be developed. Moreover, there is currently a lack of basic contemporaneous information regarding the incidence and management of BCBM in the UK, how it may vary across the country and its impact on patient outcomes. Finally, clinical studies have been hampered by a lack of a central resource to aid feasibility work and to identify potentially eligible patients. Study design: PRIMROSE will use the trainee collaborative model to establish an observational prospective UK cohort of newly diagnosed BCBM. Data collected will include routine clinico-pathological information, prior adjuvant and metastatic treatment as well as BCBM-related information including presentation, management and outcome. Anonymised data will be collated in a secure central REDCap database. All hospitals in the UK will be eligible to register patients driven by trainees from all specialties via the UK Breast Cancer Trainees Research Collaborative Group (BCTRCG) network. Eligibility criteria: Inclusion criteria: male or female patients aged &amp;gt;16 years of age, with histologically and/or cytologically confirmed BC with involvement of the brain parenchyma. There are no formal exclusion criteria. Patients with leptomeningeal disease will be registered, with data being collected in a separate project (PRIMROSE-LMD). Aims: The overarching objectives include defining the prevalence, management and outcome of BCBM in the UK. Endpoints: *Primary Endpoint: Overall survival from initial diagnosis of CNS involvement. Secondary Endpoints will include: 1. Time to initial CNS involvement from initial diagnosis of MBC; 2. Therapeutic interventions for management of CNS disease; 3. Time to intracranial tumour progression (for each line of therapy given for CNS disease); 4. Overall survival from MBC diagnosis; 5. Cause of death: progressive CNS disease versus progressive disease at other sites. *Information will be presented for the whole cohort as well as by breast cancer subtype Patient accrual: Patient accrual is due to commence in July 2019 and continue will for 2 years in the first instance. There is no predefined target accrual. Contact information: Study lead: Prof Carlo Palmieri; c.palmieri@liverpool.ac.uk

Improving orthotopic mouse models of patient-derived breast cancer brain metastases by a\xa0modified intracarotid injection\xa0method\xa0

Breast cancer brain metastasis (BCBM) remains a major clinical problem. Approximately 10–16% of patients with breast cancer develop brain metastases (BCBM). However, no systemic therapy has gained regulatory approval for the specific treatment of BCBM and this remains an area of persistent, unmet medical need. Rapid, predictive and clinically-relevant animal models are critical to study the biology of brain metastases and to identify effective therapeutic approaches for patients with BCBM. Here, we describe a method for efficient establishment of orthotopic mouse models of patient-derived brain metastases via an improved intracarotid injection protocol that permits tumor cell growth in the unique brain microenvironment without compromising the blood-brain barrier (BBB). We demonstrate that our newly improved models of patient-derived brain metastases recapitulate the histologic, molecular, and genetic characteristics of their matched patient tumor specimens and thus represent a potentially powerful tool for pre-clinical and translational research.

Abstract 2174: Intracranial PDX models of breast cancer brain metastases and PET imaging for drug efficacy studies

Abstract Background: Overexpression of the human epidermal growth factor receptor 2 (HER2) is an independent risk factor for development of brain metastases. Between 37-55% of patients with HER2-positive metastatic breast cancer develop brain metastases and the incidence is increasing. A reason for the increase of brain metastases is the improved control of systemic disease by novel therapeutics such as ado-trastuzumab emtansine (T-DM1). However, the major impact of the blood-brain-barrier (BBB), BBB efflux pumps and the local microenvironment in the brain represent a challenge for treatment of brain metastases. The aim of this study was to develop a model system of HER2 positive breast cancer brain metastases for evaluation of drugs directed at brain metastases. Methods: Subcutaneous tumors from a panel of HER2-positive PDX breast cancer models designated ST340, ST1339, ST1616B, ST1360B and ST3338 were enzymatically digested and used for intracranial stereotactic injection or intra carotid injection in nude mice. Contrast-enhanced T1- and T2-weighted Magnetic Resonance Imaging (MRI) were used to determine tumor take and growth. Drug sensitivity studies to single agent T-DM1 administered intravenously were performed at confirmed tumor take in a subset of the models. Mice were treated with either saline or T-DM1, 10 mg/kg/week x4 or 2 mg/kg/week x4. Delivery of T-DM1 to the tumor site was evaluated by PET/CT imaging with 64Cu-trastuzumab. Results: Intracranial tumor growth was detected by MR imaging in all models. T-DM1 treatment of animals with intracranial ST1339 or ST3338 tumors inhibited tumor growth and prolonged survival compared to non-treated animals. A variable response within the treatment groups was observed. Delivery of T-DM1 across the BBB to the intracranial tumors was visualized by 64Cu-trastuzumab PET/CT and high tumor uptake was associated with a response to T-DM1 therapy in the ST1339 model. Conclusion: We have established a model system for evaluating drug sensitivity in HER2 positive breast cancer brain metastases. Treatment response to T-DM1 was observed in the models. 64Cu-trastuzumab PET imaging confirmed delivery of trastuzumab to the tumors, and high uptake was associated with an increased response to T-DM1 therapy. Together, the established PDX models of breast cancer and brain metastases can be used as a relevant translational platform in combination with advanced non-invasive imaging for evaluation of new drugs. Citation Format: Carsten H. Nielsen, Michael J. Wick, Mette M. Jensen, Lotte K. Kristensen, Alyssa Moriarty, Melissa Rundle, Kyriakos P. Papadopoulos, Andreas Kjaer. Intracranial PDX models of breast cancer brain metastases and PET imaging for drug efficacy studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2174.

Abstract 49: Stromal platelet derived growth factor receptor (PDGFRβ) signaling: A novel therapeutic target for breast cancer brain metastasis (BCBM)

Abstract Stromal PDGFRβ has emerged as an actionable mediator of breast tumor-stromal communication. As a receptor tyrosine kinase, PDGFRβ is activated by its ligand, PDGFB, which is released by neighboring tumor epithelium and endothelium. However, how PDGF signaling mediates breast cancer initiation, progression, and metastasis remains unclear. To evaluate PDGFRβ in this disease, we developed a mouse model of stromal-specific PDGFRβ activation using the Fsp-cre transgene previously published by our group (PDGFRβ mutant). PDGFRβ mutant mammary glands exhibit increased tertiary side-branching and epithelial proliferation confirming a stromal-specific PDGFRβ effect on neighboring epithelium. To evaluate the functional relevance of PDGFRβ activation on metastatic progression, we performed tail vein injection of PDGFB expressing murine mammary tumor cells and, surprisingly, observed brain metastases in 50% of the PDGFRβ mutant mice while no brain lesions were seen in controls. There was no difference in the incidence of lung, liver or bone metastases. Mammary tumor cells expressing low PDGFB did not exhibit a similar increase in brain metastases in mutant mice. While there is no observable difference in blood brain barrier permeability in the mutant mice, we bypassed this variable by intracranially injecting mammary tumor cells and found that larger tumors formed in the brains of PDGFRβ mutant mice versus controls. To our knowledge, this is the first example where genetic manipulation of the stroma leads to an increased incidence of BCBM. Also, our pre-clinical data suggests that primary breast tumors that express high PDGFB could preferentially metastasize to the brain. To test this in patients, we analyzed PDGFB protein expression in a tissue microarray comprised of HER2-positive and triple negative breast cancer (TNBC) primary tumors. While high PDGFB did not correlate with site-independent metastatic recurrence, it was prognostic of brain metastasis, mirroring our mouse data. Evaluation of PDGFB in a small cohort of matched primary breast tumors with associated brain (n=5) and lung metastases (n=2) revealed intense PDGFB staining in 100% of the brain metastases, but only 50% of the lung metastases. Our findings suggest high primary tumor PDGFB expression defines a subset of breast cancer patients predisposed to brain metastases. These patients may benefit from therapeutic intervention of PDGFRβ signaling. To test this pre-clinically, we treated mice harboring intracranial tumors with the PDGFR specific inhibitor, Crenolanib. Excitingly, Crenolanib treatment significantly inhibited the brain tumor burden in these mice. Combined, our findings (1) advocate that primary tumor expression of PDGFB is a novel prognostic biomarker for the development of BCBM and (2) support clinical trial evaluation of PDGFR inhibitors for the prevention and treatment of BCBM. Citation Format: Katie A. Thies, Anisha M. Hammer, B. Eason Hildreth, Luke O. Russell, Steven T. Sizemore, Anthony J. Trimboli, Raleigh D. Kladney, Chelsea M. Bolyard, Robert Pilarski, Lynn Schoenfield, Jose Otero, Arnab Chakravarti, Matthew Ringel, Balveen Kaur, Gustavo Leone, Michael C. Ostrowski, Gina M. Sizemore. Stromal platelet derived growth factor receptor (PDGFRβ) signaling: A novel therapeutic target for breast cancer brain metastasis (BCBM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 49.

Abstract ID: 36 Geant4 modeling of targeted radionuclide therapy for brain metastasis

Many patients with breast cancer develop brain metastases, which are typically treated through whole-brain irradiation. As a potential alternative treatment, targeted radionuclide therapy (TRT) could be delivered early, targeting the areas of the vasculature where tumor cells are penetrating into the brain. We have developed a Monte Carlo model representing brain vasculature to evaluate and understand a variety of potential therapeutic nuclides: (alpha emitters) Pb-212, At-211, Ac-225, Bi-213, and Tb-149; (beta/Auger electron emitters) Lu-177, Tb-161, I-124, In-111, Y-90, Zr-89, and Ga-67. The micron-scale dose distributions from all radioactive decay products were modeled in Geant4, as well as eV-scale interactions through the G4DNA models [1] . These interactions were then superimposed on an atomic-scale DNA model [2] to estimate strand break yields. Some of the alpha emitters have decay chains with multiple daughter nuclei; we investigate the change in dose profiles and biological effectiveness as a function of time. Alpha emitters have higher doses per decay, and the depth-dose profiles fall off less quickly. The general qualities of the depth-dose profiles are maintained through biologically-relevant variations in vasculature geometry.

Breast cancer subtype and stage are prognostic of time from breast cancer diagnosis to brain metastasis development.

Breast cancer brain metastasis (BCBM) is associated with high morbidity and mortality. Patients with breast cancer risk factors associated with rapid development of BCBM could potentially benefit from early brain metastasis screening. We retrospectively reviewed all BCBM patients treated with brain radiotherapy at our institution from 1997 to 2015. Interval time to BCBM was defined as date of pathologic breast cancer diagnosis to date of radiographic evidence of brain metastasis. Patients were stratified by breast cancer molecular subtype and stage at diagnosis. Kaplan Meier analysis was conducted on time to development of BCBM. Breast cancer risk factors were correlated with time to BCBM on Cox proportion hazard analysis. The study cohort comprised 121 BCBM patients, with median interval time to BCBM of 46 months. Times to BCBM for Her2+/2HR+, Her2+, Her2-/HR+, and triple-negative (TNBC) subtypes were 70, 44, 42, and 28 months respectively (p = 0.002). Time to BCBM for stages I, II, III, and IV were 70, 54, 29, and 24 months, respectively (p = 0.000). BCBM patients were further stratified by both molecular subtype (TNBC vs. non-TNBC) and stage (I, II vs. III, IV). Median times to BCBM for non-TNBC/stage I-II, TNBC/stage I-II, non-TNBC stage III-IV, and TNBC/stage III-IV were 68, 47, 29, and 6 months respectively (p = 0.000). Subtype and stage were associated with shorter time to BCBM on multivariate analysis. Subtype and initial stage are independently correlated with decreased time to development of BCBM. Patients with advanced high stage and triple negative breast cancer develop brain metastases significantly earlier.

Targeted Therapies for Brain Metastases from Breast Cancer.

The discovery of various driver pathways and targeted small molecule agents/antibodies have revolutionized the management of metastatic breast cancer. Currently, the major targets of clinical utility in breast cancer include the human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF) receptor, mechanistic target of rapamycin (mTOR) pathway, and the cyclin-dependent kinase 4/6 (CDK-4/6) pathway. Brain metastasis, however, remains a thorn in the flesh, leading to morbidity, neuro-cognitive decline, and interruptions in the management of systemic disease. Approximately 20%–30% of patients with metastatic breast cancer develop brain metastases. Surgery, whole brain radiation therapy, and stereotactic radiosurgery are the traditional treatment options for patients with brain metastases. The therapeutic paradigm is changing due to better understanding of the blood brain barrier and the advent of tyrosine kinase inhibitors and monoclonal antibodies. Several of these agents are in clinical practice and several others are in early stage clinical trials. In this article, we will review the common targetable pathways in the management of breast cancer patients with brain metastases, and the current state of the clinical development of drugs against these pathways.

Abstract 5187: PET imaging of trastuzumab emtansine (T-DM1) drug delivery to intracranial patient derived xenograft (PDX) models of breast cancer metastasis

Abstract Background: It is estimated that 10-30% of all breast cancer patients at some point develop brain metastases. Overexpression of the human epidermal growth factor receptor 2 (HER2) is a independent risk factor for development of brain metastases. Up to 37% of patients with HER2-positive metastatic breast cancer develop brain metastases and half of these patients die as a result of failure to control the intracranial disease. A reason for this is the challenge to obtain efficient drug delivery across the blood brain barrier (BBB). Subcutaneous patient derived xenograft (PDX) models are increasingly used for efficacy studies in drug development. However, when targeting brain tumors or metastases, the major impact of the BBB on drug bioavailability must be taken into consideration. Clinical PET imaging with 64Cu or 89Zr labeled trastuzumab has previously been able to visualize breast cancer brain metastases. The aim of our study was to investigate if PET imaging with 64Cu-labeled trastuzumab was predictive of the efficacy of trastuzumab emtansine (T-DM1) in a HER2 positive breast cancer PDX model established as an intracranial brain metastases model. Methods: The intracranial PDX model was established by stereotactic intracranial injection of enzymatically digested ST1339 tumor tissue. At confirmed tumor take, mice were randomized into two arms: control and T-DM1 (10 mg/kg/week x4). Treatment response was monitored by contrast-enhanced T1- and T2-weighted Magnetic Resonance Imaging (MRI) and positron emission tomography (PET) with the amino acid radiotracer O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET). PET/CT imaging with 64Cu-trastuzumab was performed in animals with confirmed intracranial ST1339 tumors prior to treatment with T-DM1 (10 mg/kg/week x4). Results: T-DM1 treatment with 10 mg/kg/week x4 of mice with intracranial tumors inhibited tumor growth and prolonged survival compared to non-treated animals. A variable response within the treatment group was observed. Forty percent had tumor shrinkage while 60% exhibited tumor growth within the duration of the therapy. The intracranial tumors were clearly visible on the 64Cu-trastuzumab PET images co-registered with T2-weighted MR images for anatomical localization. Interestingly, the intracranial tumor uptake between the animals was rather heterogeneous. Conclusion: A treatment response to T-DM1 was observed in an intracranial ST1339 HER2 positive breast cancer PDX model. PET imaging with 64Cu-trastuzumab confirmed delivery of trastuzumab to the tumors. Further quantitative image analysis of the intracranial 64Cu-trastuzumab tumor uptake will reveal if the drug delivery measured by 64Cu-trastuzumab PET imaging is predictive of the efficacy of T-DM1 in a HER2 positive PDX breast cancer brain metastases model. Citation Format: Carsten Haagen Nielsen, Mette K. Nedergaard, Lotte K. Kristensen, Camilla S. Knudsen, Michael J. Wick, Kyri Papadopoulos, Anthony Tolcher, Andreas Kjaer. PET imaging of trastuzumab emtansine (T-DM1) drug delivery to intracranial patient derived xenograft (PDX) models of breast cancer metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5187.