Breast Cancer Brain Metastases Research Articles

Research Progress in Brain Metastasis of Breast Cancer

Research Progress in Brain Metastasis of Breast Cancer

High expression of SULF1 is associated with adverse prognosis in breast cancer brain metastasis.

Breast cancer is the most common cancer in women, and in advanced stages, it often metastasizes to the brain. However, research on the biological mechanisms of breast cancer brain metastasis and potential therapeutic targets are limited. Differential gene expression analysis (DEGs) for the datasets GSE43837 and GSE125989 from the GEO database was performed using online analysis tools such as GEO2R and Sangerbox. Further investigation related to SULF1 was conducted using online databases such as Kaplan-Meier Plotter and cBioPortal. Thus, expression levels, variations, associations with HER2, biological processes, and pathways involving SULF1 could be analyzed using UALCAN, cBioPortal, GEPIA2, and LinkedOmics databases. Moreover, the sensitivity of SULF1 to existing drugs was explored using drug databases such as RNAactDrug and CADSP. High expression of SULF1 was associated with poor prognosis in advanced breast cancer brain metastasis and was positively correlated with the expression of HER2. In the metastatic breast cancer population, SULF1 ranked top among the 16 DEGs with the highest mutation rate, reaching 11%, primarily due to amplification. KEGG and GSEA analyses revealed that the genes co-expressed with SULF1 were positively enriched in the 'ECM-receptor interaction' gene set and negatively enriched in the 'Ribosome' gene set. Currently, docetaxel and vinorelbine can act as treatment options if the expression of SULF1 is high. This study, through bioinformatics analysis, unveiled SULF1 as a potential target for treating breast cancer brain metastasis (BM).

Nanomodulators targeting endothelial WNT and pericytes to reversibly open the blood–tumor barrier for boosted brain tumor therapy

The blood–brain barrier (BBB)/blood–tumor barrier (BTB) impedes brain entry of most brain-targeted drugs, whether they are water-soluble or hydrophobic. Endothelial WNT signaling and neoplastic pericytes maintain BTB low permeability by regulating tight junctions. Here, we proposed nitazoxanide (NTZ) and ibrutinib (IBR) co-loaded ICAM-1-targeting nanoparticles (NI@I-NPs) to disrupt the BTB in a time-dependent, reversible, and size-selective manner by targeting specific ICAM-1, inactivating WNT signaling and depleting pericytes in tumor-associated blood vessels in breast cancer brain metastases. At the optimal NTZ/IBR mass ratio (1:2), BTB opening reached the optimum effect at 48–72 h without any sign of intracranial edema and cognitive impairment. The combination of NI@I-NPs and chemotherapeutic drugs (doxorubicin and etoposide) extended the median survival of mice with breast cancer brain metastases. Targeting BTB endothelial WNT signaling and tumor pericytes via NI@I-NPs could open the BTB to improve chemotherapeutic efficiency against brain metastases.

Abstract LB175: Discovery of HP567, a highly potent, brain-penetrating, and H1047R-selective PI3Kα inhibitor for the treatment of tumors bearing H1047R mutation

Abstract The phosphoinositide 3 kinase (PI3K)-protein kinase B (PKB/AKT) is one of the most altered pathways in human cancer and its hyperactivation promotes tumor growth and survival. H1047R increases kinase activity and is the most common PI3Kα mutation with a mutation rate of 7.8% in all cancers, and 21%, 5% and 3% in breast cancer, endometrium, and ovarian cancer, respectively. Alpelisib is an FDA approved PI3Kα inhibitor targeting both wild-type (WT) and mutant PI3Kα, yet its clinical benefit is limited by the toxicities including hyperglycemia and rash (which are considered on target effects of WT- PI3Kα inhibition). Here, we report an allosteric and brain-penetrating PI3Kα inhibitor, HP567 that is 14-fold selective for PI3Kα H1047R over PI3Kα WT and is 80-fold selective over other PI3K isoforms. HP567 strongly inhibits proliferation and p-AKT (S473) in H1047R mutant cell lines with an average IC50 of 138 nM and 8 nM, respectively, and has no activity against PI3Kα WT cell lines. HP567 strongly inhibits growth of tumors bearing H1047R in multiple CDX models including breast cancers (MDA-MB-453, T47D, and CAL-148), ovarian cancer (SK-OV-3), tongue squamous cell carcinoma (CAL-33), and a brain-metastatic breast cancer (MDA-MB-453), without causing hyperglycemia or increases in plasma insulin levels. In conclusion, HP567 is a novel, potent, and brain-penetrating PI3Kα H1047R selective inhibitor. The pre-clinical data supports the clinical development of HP567 for the treatment of tumors bearing PI3Kα H1047R mutations. Structure of HP567 will not be disclosed. Citation Format: Jing Li, Lei Fan, Chengcheng Liu, Yao Luo, Xiaohui Chu, Hua Yu, Fei Wang, Xinghai Li. Discovery of HP567, a highly potent, brain-penetrating, and H1047R-selective PI3Kα inhibitor for the treatment of tumors bearing H1047R mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB175.

Abstract CT074: ELECTRA: An open-label, multicenter, phase 1b/2 study of elacestrant in combination with abemaciclib in patients with brain metastasis from estrogen receptor-positive (ER+), HER2-negative (HER2-) breast cancer (BC)

Abstract Background: Endocrine therapy (ET) + cyclin dependent kinase 4/6 inhibitor (CDK4/6i) is the mainstay for the management of ER+/HER2- mBC as 1st-line therapy. However, tumors eventually develop resistance to ET, leading to disease progression. In the EMERALD phase 3 trial, single-agent elacestrant was associated with significantly prolonged progression-free survival (PFS) and a manageable safety profile vs standard of care (SOC) ET, leading to the first oral SERD approval. Patients receiving elacestrant experienced a median PFS (mPFS) of 3.8 months vs 1.9 months with SOC (Bidard, 2022). Patients who received ≥12 months of prior CDK4/6i experienced a mPFS of 8.6 months with elacestrant vs 1.9 months with SOC (SABCS, 2022). Currently, there are no approved systemic treatments for patients with ER+/HER2- BC who have brain metastasis. The rationale for the ELECTRA study is to combine elacestrant with abemaciclib in patients with brain metastasis, given both compounds have demonstrated the ability to cross the blood-brain barrier (Conlan, 2020; Tolaney, 2020). Methods: ELECTRA (NCT05386108) is an open-label phase 1b/2, multicenter study evaluating elacestrant in combination with abemaciclib. Eligibility includes patients with ER+/HER2- locally advanced or metastatic BC and measurable brain metastasis. For phase 1b, the presence of brain metastasis is not required for eligibility. For phase 2, patients must have ≥ 1 active and measurable brain metastasis per RECIST v1.1. Patients must have received prior therapy in the metastatic setting, including ≥ 1 endocrine therapy, ≤ 2 chemotherapy regimens, and 0-2 prior CDK4/6i (excluding abemaciclib). The phase 1b primary objective is to determine the recommended phase 2 dose (RP2D); secondary objectives include safety, pharmacokinetics (PK), overall response rate (ORR), duration of response (DoR), clinical benefit rate (CBR), PFS, and overall survival (OS). The phase 2 primary objective is ORR per RECIST v1.1; secondary objectives include intracranial response rate, DoR, CBR, PFS, OS, PK, and quality of life. The phase 1b portion of the trial is actively ongoing to determine the RP2D with study sites open worldwide. Citation Format: Erika Hamilton, Sung-Bae Kim, Nancy U. Lin, Ahmad Awada, Eva Ciruelos Gil, Alessandro Di Sanzo, Bartomeu Piza Vallespir, Kathy Puyana Theall, Nuhad Ibrahim. ELECTRA: An open-label, multicenter, phase 1b/2 study of elacestrant in combination with abemaciclib in patients with brain metastasis from estrogen receptor-positive (ER+), HER2-negative (HER2-) breast cancer (BC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT074.

B7-H3 Expression in Breast Cancer and Brain Metastasis.

Brain metastasis is a significant challenge for some breast cancer patients, marked by its aggressive nature, limited treatment options, and poor clinical outcomes. Immunotherapies have emerged as a promising avenue for brain metastasis treatment. B7-H3 (CD276) is an immune checkpoint molecule involved in T cell suppression, which is associated with poor survival in cancer patients. Given the increasing number of clinical trials using B7-H3 targeting CAR T cell therapies, we examined B7-H3 expression across breast cancer subtypes and in breast cancer brain metastases to assess its potential as an interventional target. B7-H3 expression was investigated using immunohistochemistry on tissue microarrays of three clinical cohorts: (i) unselected primary breast cancers (n = 347); (ii) brain metastatic breast cancers (n = 61) and breast cancer brain metastases (n = 80, including a subset of 53 patient-matched breast and brain metastasis cases); and (iii) mixed brain metastases from a range of primary tumours (n = 137). In primary breast cancers, B7-H3 expression significantly correlated with higher tumour grades and aggressive breast cancer subtypes, as well as poorer 5-year survival outcomes. Subcellular localisation of B7-H3 impacted breast cancer-specific survival, with cytoplasmic staining also correlating with a poorer outcome. Its expression was frequently detected in brain metastases from breast cancers, with up to 90% expressing B7-H3. However, not all brain metastases showed high levels of expression, with those from colorectal and renal tumours showing a low frequency of B7-H3 expression (0/14 and 2/16, respectively). The prevalence of B7-H3 expression in breast cancers and breast cancer brain metastases indicates potential opportunities for B7-H3 targeted therapies in breast cancer management.

Abstract 1550: Identification of a novel squalene epoxidase function in breast cancer brain metastasis

Abstract Brain metastases are serious complications of breast cancer, especially in triple-negative breast cancer (TNBC) patients. There is currently no effective treatment due to the unique brain microenvironment and limitation for drugs to cross the blood-brain barrier (BBB). BBB limits access of nutrients from the circulation and thereby makes the brain hypoxic and depleted of metabolites, growth factors and proteins. However, it remains poorly understood how breast cancer cells manipulate for adaption and colonization in the brain. To probe the molecular mechanism of breast cancer brain metastasis (BCBM), we compared gene signatures in primary breast tumors and BCBM tumors, and identified that SQLE (encodes squalene epoxidase, the second rate-limiting enzyme in the cholesterol biosynthesis) could be a leading-edge gene in breast cancer brain metastasis. To explore the role of SQLE in BCBM, we established the brain metastatic TNBC MDA-MB-231 (MDA231-BrM) cell line from brain metastatic subpopulation that originated from its parental MDA-MB-231 (MDA231) cell line. We found that SQLE expression was greatly upregulated in MDA231-BrM cells compared with the parental MDA231 cells. Using MDA231-BrM and MDA231 cell lines expressing SQLE shRNAs, we evaluated the effects of SQLE loss on cancer cell migration, invasion, and stemness by wound-healing, transwell invasion/migration, and tumorsphere formation assays. While loss of SQLE greatly attenuated cell invasiveness and stemness in both MDA231 and MDA231-BrM cells, loss of SQLE could only affect the cell migration activity on MDA231 cells but not MDA231-BrM cells. Our RNA-seq data further identified a subset of SQLE-affected genes that is uniquely enriched in MDA231-BrM cells and favors brain extravasation and colonization. To explore the potential function of SQLE in brain extravasation and colonization, we established in vitro BBB models and ex vivo mouse brain slice organotypic cultures. We showed that loss of SQLE inhibited the ability of MDA231-BrM cells to across the BBB-mimic astrocyte-endothelial structures as well as impaired the co-option with blood capillaries in the mouse brain slices. Although SQLE-deficient MDA231-BrM cells could still spread on the surface of the blood vessels, they seemed to undergo apoptosis. Since the ability to invade, migrate, and penetrate is critical for invasion of cancer cells, our results strongly imply the novel function of SQLE in breast cancer cell invasion, penetration, and even colonization in the brain through blood vessel co-option. In summary, our data reveal a novel role for SQLE in two critical requisites for breast-to-brain extravasation and colonization - the ability to penetrate through BBB and to co-opt brain vessels for metastatic expansion. Our findings indicate that targeting SQLE may represent a therapeutic opportunity for breast cancer brain metastases. Citation Format: Shu-Ping Wang, Jia-Yun Yeh, Yu-Ling (Pony) Lee, Kun-Yuan Lin, Chao-Di Chang, Chih-Chieh Yang, Shan-Yun Cheng, Ya-Wen Hung, Yu-Hsien Chang, Yao-Feng Li, Yung-Lung Yu. Identification of a novel squalene epoxidase function in breast cancer brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1550.

Abstract 5551: Targeted nanoparticles co-delivering PARP inhibitor and other immune modulators overcome the immunosuppressive tumor microenvironment

Abstract Several mutations have been identified that are associated with an increased risk of triple-negative breast cancer (TNBC), including those that are deleterious in the BRCA gene. TNBC is associated with the worst prognosis and the highest incidence of brain metastasis (30%) among all subtypes of BC. Despite objective responses to poly (ADP-ribose) polymerase (PARP) inhibition and improvements in progression-free survival (PFS) compared to standard chemotherapy in patients with BRCA-mutated TNBC, benefits are transitory. Furthermore, our understanding of the effect of PARP inhibitors (PARPi) in treating breast cancer brain metastasis (BCBM) and modulating its tumor microenvironment (TME) is still lacking. To this end, we analyzed the brain TME of BRCA-mutated BCBM in the absence or presence of treatment with PARPi. Interestingly, we found that the immune TME of the brain hinder the antitumor activity of PARPi by upregulating multiple immunosuppressive molecules, including PD-L1. Furthermore, we found that BCBM overexpress P-selectin through its interaction with the tumor-associated microglia, bone marrow-derived macrophages and endothelial cells in the TME. Thus, we designed a novel nanoparticle (NP) targeting P-selectin to serve as a brain-penetrant delivery system for the treatment of BCBM. In order to target BRCA-mutated BCBM, we harnessed our novel P-selectin-targeted NPs to entrap PARPi and other immune modulators that we found to exert synergistic activity when combined. To evaluate the antitumor activity of our P-selectin-targeted NPs, we established 3-dimensional (3D) ex vivo and in vivo BRCA-mutated BCBM models. Importantly, we saw favorable effects of the P-selectin-targeted NPs in comparison to the combination of the free drugs, suggesting that out targeted-NPs overcome the TME-mediated resistance to PARPi through the modulation of the immunosuppressive microenvironment of the brain. Citation Format: Rami Khoury, Ron Kleiner, Eilam Yeini, Daniel Rodriguez Ajamil, Sahar Israeli Dangoor, Tamer Sanalla, Iris Barshack, Roni Satchi-Fainaro. Targeted nanoparticles co-delivering PARP inhibitor and other immune modulators overcome the immunosuppressive tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5551.

Abstract 2767: Exploring ADAR1 dependencies in breast cancer brain-metastases

Abstract Background: Adenosine deaminase acting on double-stranded RNA (ADAR1) is a recognized driver of epitranscriptomic (post-transcriptional) remodeling and tumor progression. Changes in amino acid sequence, mRNA splicing, and/or polyadenylation sites are only some of the adenosine-to-inosine (A-to-I) RNA editing effects. Under physiological conditions, ADAR1 activity prevents autoinflammation by inhibiting the accumulation of endogenous immunostimulatory double-stranded RNA and by suppressing the Z-RNA sensor ZBP1. Such mechanisms are exploited by cancer cells to desensitize tumor response to therapies, therefore augmenting aggressiveness. Approximately 10 to 20% of patients diagnosed with breast cancer (BC) will develop metastatic disease, which remains the leading cause of death in individuals with BC. We have hypothesized that ADAR1 and its interferon-inducible p150 isoform, play a pivotal role in promoting BC metastases since high levels of ADAR1 are associated with a worse prognosis in patients with high grade BC, especially in the triple-negative BC subgroup (TNBC), which is the most likely to develop brain metastases. Methods: We established a humanized mouse model of breast cancer brain metastases (BC-BrM) using neonatal intracerebroventricular inoculation of MDA-MD-231 TNBC cells and primary patient derived metastatic cells in Rag2−/−γc−/− mice. Before implantation, MDA-MD-231 cells were transduced with a nanoluc-GFP reporter for tracing ADAR1 enzymatic activity in the brain metastatic niche. Lentiviral shRNA knockdown vectors targeting ADAR1, combined with over-expression vectors of full-length ADAR1 or the p150 deleted isoform were adopted to detect editing changes in the metastatic model through RNA-sequencing of BC-BrM. Results: BrM derived from MDA-MD-231 implants display upregulation of ADAR1 p150 and activation of the WNT/β-catenin pathway compared to the non-implanted cell lines. Upon shRNA knockdown of ADAR1, decreased expression of BC stem cell markers was detected via FACS in MDA-MD-231 ADAR1 knocked-down versus control BC-BrM isolated cells. We are now exploring molecular pathways affected by ADAR1 loss/overexpression in establishing BrM. Future Directions: We have developed a biorepository of primary patient-derived metastatic breast cancer samples and have begun the process of tracking metastatic kinetics and ADAR1 activation with the ADAR1 reporter in an orthotopic mouse model. Overall, this study will provide new insights into the molecular role of ADAR1 deaminase activity in establishing and maintaining metastatic niches. Citation Format: Teresa Sposito, Emma E. Klacking, Antonio W. Ruiz, Jessica Pham, Catriona Jamieson. Exploring ADAR1 dependencies in breast cancer brain-metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2767.

Abstract 1557: Loss of lncRNA XIST promote brain metastasis by reshaping tumor lipid metabolism via upregulation of ACSL4

Abstract Metastatic disease is the main cause of cancer death, and the brain is one of the major sites of breast tumor metastasis. The median survival of breast cancer patients who developed brain metastases (BrM) is less than a year even with the advanced treatment such as stereotactic radiosurgery (SRS). Regardless of high clinical significance, the pathological mechanism of brain metastasis is still poorly understood. Previously, we found that loss of lncRNA XIST robustly promote metastasis and specially brain metastasis in breast cancer. However, the underlying molecular mechanism was not fully understood. In following study, we found that loss of XIST has significantly altered lipid metabolism of breast cancer cells specifically increasing lipid droplet amount and PUFA incorporation. Instead of de novo syntheses, XISTlow cancer cells acquire fatty acid by uptake from exogenous. We found that one X-linked gene, Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4) which are highly upregulated after loss of XIST is responsible for the altered lipid metabolism. ACSL4 activated the free polyunsaturated fatty acids (PUFAs) and lead to increased incorporation of PUFAs into phospholipids. On one hand, elevated ACLS4 expression leads to relative low PPAR pathway activation by decreasing the cellular free PUFA level which directly binds and activate PPAR. PPAR pathway is known to inhibit the expression of inflammatory cytokines which are important for cancer cells to establish brain metastasis. On the other hand, elevated ACSL4 expression enable cancer cells to metabolize the abundant PUFAs in the brain environment, thereby gaining survival advantage. However, increased PUFA incorporation into lipids especially phospholipids produce excess lipid ROS and sensitize cells to ferroptosis inducer such as RSL3. Our study has find out that brain microenvironment not only supports the outgrowth of XIST low cells by providing PUFAs for maintaining their metastatic properties but also sensitizes those cells to ferroptosis inducers, a potential therapy for treating this devastating disease. Citation Format: Yin Liu, Margaret R. Smith, Yuezhu Wang, Ralph D’Agostino, Jimmy Ruiz, Gregory L. Kucera, Lance D. Miller, Wencheng Li, Michael D. Chan, Michael Farris, Dawen Zhao, Fei Xing. Loss of lncRNA XIST promote brain metastasis by reshaping tumor lipid metabolism via upregulation of ACSL4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1557.

Abstract 1449: Targeting squalene epoxidase for breast cancer brain metastasis: The evaluation of a new therapeutic target for brain extravasation and colonization using animal models

Abstract Breast cancer brain metastasis is one of the most common forms of breast cancer metastasis and a major cause of morbidity and mortality. Patients who develop brain metastases tend to be associated with progressive neurologic deficits and short overall survival, which represents an unmet medical need. Extensive research has been conducted to elucidate the mechanism of cancer metastasis with limited information gained as to how cancer cells extravasate and colonize to the brain. Recently, we identified a novel mechanism by which squalene epoxidase (SQLE), the second rate-limiting enzyme in cholesterol biosynthesis, plays a critical role in the process of breast cancer metastasis to the brain. Thus, toward a better understanding of the underlying molecular mechanisms and applications of molecular target(s) for brain metastasis therapy, murine models were employed for investigation of brain extravasation and colonization with intracardiac or direct intracranial injections of GFP/FLuc-labeled human MDA-MB-231 metastatic breast carcinoma cells. The MDA-MB-231 cells were found to metastasize to the brain and other organs following intracardiac implantation into nude mice and were further isolated from each tissue. Interestingly, the isolated brain-metastasized tumor cells (MDA-MB-231-BrM) exhibited a significant upregulation of SQLE expression when compared with those that metastasized to other distal sites. The essential role of SQLE in the specific steps of the breast cancer-to-brain metastatic process was evaluated by ex vivo immunofluorescence analysis and immunohistochemistry staining of brain slices from the study subjects. Our data demonstrate that high SQLE expression is essential for MDA-MB-231-BrM to extravasate into the parenchyma, as well as the formation of micro- and macro-metastases in the brain. Interestingly, we found that blood vessel co-option and the surrounding neuronal cells play key roles in supporting MDA-MB-231-BrM to develop brain macro-metastases. In vitro blood-brain barrier (BBB) models further demonstrated the critical role of SQLE in promoting tumor cell invasion and penetration through the BBB. To verify SQLE as an oncogenic factor that can be selected as a potential therapeutic target in suppressing breast cancer brain metastasis, we evaluated the inhibitory effects of terbinafine (a SQLE inhibitor) in both the MDA-MB-231-BrM orthotopic and intracardiac mouse models. Pharmacologic inhibition of SQLE by terbinafine suppressed MDA-MB-231-BrM tumor growth at the mammary fat pad and distal metastases to the brain, suggesting that targeting SQLE represents a therapeutic opportunity for breast cancer brain metastasis. Citation Format: Pony Yu-Ling Lee, Kun-Yuan Lin, Chao-Di Chang, Shan-Yun Cheng, Ya-Wen Hung, Chih-Chieh Yang, Yu-Hsien Chang, Chien-Chang Shen, Jia-Yun Yeh, Yung-Lung Yu, Shu-Ping Wang. Targeting squalene epoxidase for breast cancer brain metastasis: The evaluation of a new therapeutic target for brain extravasation and colonization using animal models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1449.

Abstract 829: Phthalate exposure results in circadian rhythm-induced BBB dysfunction increasing the risk for breast cancer brain metastasis

Abstract Phthalates, classified as plasticizers, represent a group of chemicals pervasive in the general U.S. population, with notably higher levels in non-Hispanic Blacks compared to non-Hispanic Whites. These persistent organic pollutants (POPs) have been identified for their impact on the circadian rhythms of the brain and vascular system. Several studies indicate that phthalates can elevate neuroinflammation and reduce levels of the junctional protein ZO-1 in the hypothalamus, home to the master circadian clock known as the suprachiasmatic nucleus (SCN). The SCN regulates cellular and tissue circadian rhythms, including tight junction proteins essential for the blood-brain barrier's (BBB) main barrier function. Interestingly, experimental studies reveal that prolonged chronic circadian rhythm disruption (CRD) in mice leads to increased breast cancer metastasis. However, the effects of phthalates on CRD concerning brain cancer and metastasis remain poorly understood. Given their significant prevalence and biological impact, we hypothesize that phthalate exposure induces CRD through hypothalamic dysregulation, resulting in BBB dysfunction and an elevated risk of brain metastasis. Results. We developed an in vitro BBB model using endothelial cells and exposed them to an environmentally relevant mixture of five phthalates simulating chronic low-grade exposure. Analysis showed dysregulation of critical clock genes (Bmal1 and Clock), along with a substantial decrease in BBB tight junction proteins (claudin-5 and occludin) at the protein and mRNA levels. The tumor trans-endothelial migration assay using breast adenocarcinoma cells along with endothelial cells demonstrated an increased metastatic potential following phthalate exposure. Conclusion. These findings offer crucial insights into the molecular mechanisms underlying phthalate exposure, suggesting potential targets for future brain metastasis treatments. Additionally, they hold implications for the future regulation and management of phthalate usage and policy. This work was supported by the University of Miami U-LINK Resilience Challenge grant. Citation Format: Destiny Tiburcio, Sarah Adolphe, Ijeoma B. Akpu, Timea Teglas, Oandy Naranjo, Sophia H. George, Michal J. Toborek. Phthalate exposure results in circadian rhythm-induced BBB dysfunction increasing the risk for breast cancer brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 829.

Abstract 3157: The crosstalk between STAT3 and p53/ERK signaling regulates brain metastasis

Abstract Brain metastasis (BM) affects approximately 10% of cancer patients with metastatic disease, representing a major cause of morbidity and mortality. BM is a complex multi-step process involving various immune checkpoint proteins. Mitogen-activated protein kinase (MAPK), particularly extracellular signal-regulated kinases 1/2 (ERK1/2), and signal transducer and activator of transcription 3 (STAT3) are implicated in tumorigenesis and are critical upstream regulators of Programmed Death Ligand 1 (PD-L1) expression, a common immunotherapy target. Tumor suppressor p53 is shown to regulate STAT3 and ERK1/2 signaling, which are dysregulated in various malignancies. We hypothesize that p53 along with STAT3 and ERK1/2 play a critical role in the initiation and maintenance of BM. Twenty-six BM tumors with various primary sites of origin were used following IRB guidelines. pSTAT3Tyr705, pERK1/2Thr202/Tyr204, mutant p53 (p53mt), and PD-L1 expression was determined by immunohistochemistry. Gene expression analysis of BM was performed on a cDNA microarray. Human brain metastatic breast cancer cells (MDA-MB-231) were treated with STAT3 inhibitor (NSC74859) or MAPK inhibitor (U0126) in regular or astrocytic media to determine cell proliferation and migration by MTT assay and scratch-wound, respectively. ERK1/2 signaling pathway status was determined by Western blotting. Results demonstrated: 1) pSTAT3Tyr705 and pERK1/2Thr202/Tyr204 were expressed profusely at tumor margins, while p53mt was uniformly expressed throughout. 81% of BM expressed p53mt while 86% and 63% expressed pERK1/2Thr202/Tyr204 and pSTAT3Tyr705, respectively. Venn analysis displayed significant overlap between expression, with 62% overlap between p53mt and pERK1/2Thr202/Tyr204 and a 50% overlap between both pSTAT3Tyr705 and pERK1/2Thr202/Tyr204 with p53mt. Expression of PD-L1 was seen in a majority of BM tumors. 2) Gene expression analysis demonstrated alterations in 32 STAT3- and MAPK-associated genes; these included upregulation of stathmin-1 and stathmin-like 3, which control microtubule dynamics in STAT3-related cell migration, and changes in cytokine-related genes, suggesting altered immune responses. 3) Cell proliferation showed augmented growth in astrocytic media (p≤0.05) and was significantly decreased following treatment with NSC74850 or U0126 (p≤0.01). While migration showed a trend towards significance in reduction following NSC74859 (p=0.08), migration stagnated following U0126 treatment in astrocytic media (p≤0.01). 4) pERK1/2Thr202/Tyr204 expression was reduced following U0126 or NSC74859 treatment. These findings suggest activation of STAT3 and ERK1/2 promote BM and suppression of these pathways may lead to a reduction in cell viability and motility. Therefore, this provides compelling evidence for the use of STAT3 and ERK1/2 along with p53 as potential targets for immunotherapy in brain metastatic disease. Citation Format: Sabrina L. Zeller, Eris Spirollari, John V. Wainwright, Simon J. Hanft, Chirag D. Gandhi, Meena Jhanwar-Uniyal. The crosstalk between STAT3 and p53/ERK signaling regulates brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3157.

O257: A Transcriptome Analysis of Primary Breast Cancer with Discordant Brain Metastasis Subtype

Abstract Introduction Brain metastasis (BM) occurs in 15-30% of breast cancer (BC) cases. In the era of personalised medicine, knowledge of the BM subtype is of increasing importance. However, there is often discordance between breast primary (BP) subtype and its BM. Improvements in stereotactic radiosurgery and neuroradiology have greatly reduced the number patients undergoing surgical resection. Therefore, identifying BM subtype poses a therapeutic challenge. Methods This study included 116 patients with breast cancer brain metastasis on CTRIAL-IE 09/07. Clinical subtype was evaluated using immunohistochemistry (IHC) results for oestrogen receptor (ER), progesterone receptor (PR) and HER2. 63 BP RNA sequencing (RNA-Seq) samples were analysed to identify differentially expressed genes in ER positive (ER+) primaries that subsequently lost ER in BM vs. ER+ primaries that retained ER. Results 34 (29.3%) of BPs were ER+/HER2- vs. 19 (16.4%) brain metastases, 50 (43.1%) BPs were HER2+ vs. 60 (51.7%) metastases, 32 (27.6%) BPs were TNBC vs. 37 (31.9%) metastases. The most common receptor switches were loss of ER 20/62 (32.36%), loss of PR 17/30 (56.7%) and gain of HER2 11/65 (16.9%). RNA-Seq differential expression analysis of ER+ primary/ER- BM vs. ER+ primary/ER+ BM found ALB, CPA1, GOLGA8G were significantly underexpressed in patients that subsequently lost ER, conversely MUC2, AREG and HSPB1 were significantly overexpressed. Conclusion This study profiles receptor discordance between primary BC and its matched BM. Future studies of differentially expressed genes at a transcript level may predict BM subtype using primary RNA-Seq data and allow for a more tailored treatment approach.

Protecting the Brain: Novel Strategies for Preventing Breast Cancer Brain Metastases through Selective Estrogen Receptor β Agonists and In Vitro Blood-Brain Barrier Models.

Breast cancer brain metastasis (BCBM) is a challenging condition with limited treatment options and poor prognosis. Understanding the interactions between tumor cells and the blood-brain barrier (BBB) is critical for developing novel therapeutic strategies. One promising target is estrogen receptor β (ERβ), which promotes the expression of key tight junction proteins, sealing the BBB and reducing its permeability. In this study, we investigated the effects of 17β-estradiol (E2) and the selective ERβ agonist diarylpropionitrile (DPN) on endothelial and cancer cells. Western blot analysis revealed the expression patterns of ERs in these cell lines, and estrogen treatment upregulated claudin-5 expression in brain endothelial cells. Using in vitro models of the BBB, we found that DPN treatment significantly increased BBB tightness about suppressed BBB transmigration activity of representative Her2-positive (BT-474) and triple-negative (MDA-MB-231) breast cancer cell lines. However, the efficacy of DPN treatment decreased when cancer cells were pre-differentiated in the presence of E2. Our results support ERβ as a potential target for the prevention and treatment of BCBM and suggest that targeted vector-based approaches may be effective for future preventive and therapeutic implications.

Design and Structural Investigation of a Series of Prodigiosin and 1,10-Phenanthroline Derivatives as Novel and Highly Potent Anticancer Therapeutic Drugs or Active Pharmaceutical Ingredients

Breast cancer is considered as a leading cancer type with the secondary highest possibility of brain metastasis. Most research in breast cancer is currently directed into the mortality of brain metastatic breast cancer. However, there is no effective treatment or anticancer therapeutics specifically for this cancer type. Hence, development of effective and novel anticancer therapeutic drugs/APIs to inhibit HDAC and mTOR, playing very important role on modulating breast cancer progression is an increasing demand. In this study, the structure-activity relationship and in silico modeling of a series of prodigiosin and 1,10-phenanthroline derivatives as highly potent anticancer therapeutic drugs/APIs against mTOR and HDAC enzymes have been investigated. Compared to the natural product Ps, 20 of the highly potent ligands, especially 2a, 6b, 13 and 13a, have exhibited very promising binding energies ranging from –9.4 to –7.1 kcal/mol and inhibition constants ranging from 225 to 569 nM against HDAC1 and/or mTOR enzymes. Ligands 2a, 5, 6b, 7b and 13 in particular show effective dual action against both enzymes. The findings from the in silico modeling studies have also been supported with MD simulations and ADMET study with Lipinski’s rule of five, providing outstanding therapeutic potential for the breast cancer brain metastasis.

O-Glycome Profiling of Breast Cancer Cell Lines to Understand Breast Cancer Brain Metastasis.

Breast cancer is the second leading cause of cancer-related death among women and a major source of brain metastases. Despite the increasing incidence of brain metastasis from breast cancer, the underlying mechanisms remain poorly understood. Altered glycosylation is known to play a role in various diseases including cancer metastasis. However, profiling studies of O-glycans and their isomers in breast cancer brain metastasis (BCBM) are scarce. This study analyzed the expression of O-glycans and their isomers in human breast cancer cell lines (MDA-MB-231, MDA-MB-361, HTB131, and HTB22), a brain cancer cell line (CRL-1620), and a brain metastatic breast cancer cell line (MDA-MB-231BR) using nanoLC-MS/MS, identifying 27 O-glycan compositions. We observed significant upregulation in the expression of HexNAc1Hex1NeuAc2 and HexNAc2Hex3, whereas the expression of HexNAc1Hex1NeuAc1 was downregulated in MDA-MB-231BR compared to other cell lines. In our isomeric analysis, we observed notable alterations in the isomeric forms of the O-glycan structure HexNAc1Hex1NeuAc1 in a comparison of different cell lines. Our analysis of O-glycans and their isomers in cancer cells demonstrated that changes in their distribution can be related to the metastatic process. We believe that our investigation will contribute to an enhanced comprehension of the significance of O-glycans and their isomers in BCBM.

Abstract B004: Clinico-genomic characteristics of breast cancer brain metastasis: A multi-institutional analysis from AACR Project GENIE BPC

Abstract Purpose: The presence of Her2 amplification is associated with an increased risk of developing brain metastases. Brain metastases in breast cancer can be particularly challenging and have significant implications for prognosis and treatment. Common Her2-targeted therapies and small tyrosine kinase inhibitors have demonstrated the ability to penetrate the blood brain barrier and be effective in treating brain metastases. We investigated the clinico-genomic characteristics and the prognosis of brain metastasis in patients with breast cancer. Experimental design: Patients with breast cancer whose tumors underwent targeted sequencing from 2013-2018 at age 56 years old or younger at three institutions from the American Association of Cancer Research Genomics Evidence Neoplasia Information Exchange Biopharma Collaborative (AACR Project GENIE BPC) registry were selected for data curation. The PRISSMM data model was used for real world outcomes including overall survival. We analyzed clinical and genomic characteristics, treatment, and clinical outcome data among patients with and without brain metastases, stratified by Her2 amplification and hormone-receptor status (Her2+ vs. Her2-/HR+ vs. triple-negative breast cancer (TNBC)). We explored the top 20 most frequently altered genes that were included on at least 20% of sequencing panels. Results: A total of 1019 patients with breast cancer along with their receptor subtype information were included in the study (110 patients were excluded due to either post- mortem sequencing or unknown receptor subtype). Among them, 336 (33%) patients were identified to have developed brain metastasis (n=87 with Her2+; n=181 with Her2-/HR+; and n=68 with TNBC). At time of advanced disease, the brain was the first and only distant site of disease in 41/336 (12%) and detected with extracranial sites of disease in 22/336 (7%) patients. For patients presenting with stage I-III breast cancer, the cumulative incidence of brain metastasis at 5 years from breast cancer diagnosis was higher in those with TNBC (35%; 95% CI: 25, 50) as compared to 24% (95% CI: 16, 37) and 21% (95% CI: 15, 29) for those with Her2+ and Her2-/HR+ subtypes, respectively. Median overall survival from brain metastasis was significantly longer (log-rank p<0.001) for those with Her2+ disease (19m, 95% CI: 13, 36) compared to those with Her2-/HR+ (8.9m, 95% CI: 6.3, 15) or TNBC (7.4m, 95% CI: 4.6, 11). Among patients who ever developed brain metastases, IKZF3 alterations occurred in 71% (20/28) of Her2+ patients but did not occur in either Her2- subtype. Additionally, frequencies of CDK12, MYC, and PTEN alterations differed across subtypes. Conclusions: Brain involvement at metastatic presentation conferred a higher risk of death than brain-sparing metastases. Triple negative and Her2+ histologies were associated with higher risk of brain involvement at metastasis presentation. Further exploration by treatment received across receptor subtypes and genomic alterations will be presented. Citation Format: Samantha Brown, Hannah E. Fuchs, Jessica A. Lavery, Katherine S. Panageas, Nelson S. Moss. Clinico-genomic characteristics of breast cancer brain metastasis: A multi-institutional analysis from AACR Project GENIE BPC [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B004.

Abstract A041: Vascular normalization improves the delivery and efficacy of CAR-T cells in mouse brain cancers

Abstract Introduction: Chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment of hematological malignancies, but its efficacy in patients with glioblastoma (GBM) and other solid tumors is limited due to poor tumor infiltration and an immunosuppressive tumor microenvironment (TME). We have previously shown that blocking vascular endothelial growth factor (VEGF) signaling can normalize tumor vessels, convert the immunosuppressive TME into an immunostimulatory environment, and enhance the efficacy of immunotherapy. This study aimed to investigate whether combining anti-VEGF therapy (B20) with EGFRvIII-targeting CAR-T cell treatment could improve delivery and effectiveness in immunocompetent orthotopic GBM mouse models. Methods: The study utilized two syngeneic mouse GBM cell lines (CT2A and GSC005) engineered to express EGFRvIII, a common neoantigen in human GBM. CAR-T cells were designed to target EGFRvIII. GBM-bearing mice were treated with B20[LS1] followed by EGFRvIII-CAR-T injection. Intravital imaging using two-photon microscopy was employed to track CAR-T cell infiltration into the tumor, while flow cytometry was used to measure the number and function of CAR-T and other immune cells. Results: The combination of B20 and CAR-T cell treatment significantly prolonged the survival of GBM-bearing mice compared to CAR-T cell therapy alone. Intravital imaging revealed that B20 normalized tumor vasculature, leading to a four-fold increase in the number of infiltrated CAR-T cells compared to CAR-T therapy without B20. Flow cytometry analysis showed an increased population of IL-2+ or IFN-γ+ CAR-T cells, indicating that B20 enhanced the anti-tumor function of injected CAR-T cells. Additionally, B20 therapy increased the population of endogenous lymphocytes, specifically Granzyme B+ TNF-α+ CD8 T cells (Cytotoxic T lymphocytes; CTLs) while decreasing FoxP3+ CD4 T cells (Regulatory T cells; Tregs). This indicated that the TME was remodeled to enhance the effect of CAR-T therapy. Conclusions: Our study demonstrated that combining B20 with CAR-T therapy improved their efficacy in GBM mouse models by enhancing CAR-T cell infiltration and reprogramming the TME to activate CAR-T cells and effector T cells. These findings provide compelling evidence for clinically evaluating the combination of anti-VEGF agents with CAR-T cells in GBM patients. We are now building on this approach to enhance CAR-T therapy for breast cancer brain metastasis. We are testing TNBC-targeting CAR-T therapy in murine TNBC-BrM[LS2] using a similar approach. Our hypothesis is that similar to the GBM results, anti-VEGF therapy and adoptive transfer of TNBC-targeting CAR-T cells [LS3] will improve CAR-T cell infiltration, delay tumor growth and prolong survival. This strategy has the potential to enhance emerging cellular immunotherapies' effectiveness in the brain tumor microenvironment. Citation Format: Vasiliki Salameti, Xinyue Dong, Jun Ren, Zohreh Amoozgar, Somin Lee, Meenal Datta, Sylvie Roberge, Mark Duquette, Dai Fukumura, Rakesh K. Jain. Vascular normalization improves the delivery and efficacy of CAR-T cells in mouse brain cancers [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr A041.

A Biodegradable Nanosuspension Locally Used for Inhibiting Postoperative Recurrence and Brain Metastasis of Breast Cancer.

Addressing the urgent need to prevent breast cancer postoperative recurrence and brain metastasis, Fe-metal organic framework (MOF)-coated hollow mesoporous organosilica nanoparticles (HMON) with tumor microenvironment dual-responsive degradability were prepared to encapsulate doxorubicin (DOX), formulating a tissue-adhesive nanosuspension for perioperative topical medication. This nanosuspension can not only retain the sustainably released drug in the postoperative residual tumor sites but also enhance the intracellular oxidative stress of tumors for remarkable tumor ferroptosis. Interestingly, the nanosuspension can act as an immune amplifier, which could not only stimulate DC cells to secrete chemokines for T cell recruitment but also elevate antigen exposure to facilitate the antigen presentation in lymph nodes. Thus, this nanosuspension could significantly activate antitumor immune responses in both in situ tumors and metastatic encephaloma for enhanced immunotherapy. In conjunction with the clinical PD-1 antibody, the locally administered nanosuspension could achieve an advanced therapeutic outcome for inhibiting postoperative recurrence and metastasis.