Metabolic Reprogramming Underlying Brain Metastasis of Breast Cancer

The development of brain metastasis is a major cause of death in patients with breast cancer, characterized by rapid progression of the disease and poor prognosis, and lack of effective treatment has existed as an unresolved issue clinically. Extensive research has shown that a variety of metabolic changes associated with cellular metastasis exist in primary breast cancer or brain metastases, therefore to elucidate metabolic characteristics at each step of the metastasis cascade will provide important clues to the efficient treatment. In this review, we discuss the changes in metabolic patterns of breast cancer cells at every step of metastasis for exploring the potential therapeutic target based on metabolic reprogramming, and provide new insights on the design and development of drugs for breast cancer brain metastasis.

Total Brain Irradiation for Metastatic Lesions in Breast Cancer Patients

Purpose: Brain metastasis (BM) has a significant negative impact on the survival of breast cancer patients. An intensive search is underway for a multi-modal approach to identify the most effective methods of treating such patients. Material and methods: The study included 40 patients with breast cancer who were diagnosed with BM on magnetic resonance imaging (MRI) of the brain. Total brain irradiation (TBI) up to 30 Gy (3 Gy) was used as the main treatment method. The median age was 48 (31–70) years. In 75 % of cases, a nonluminal subtype of breast cancer was found, in 57.5 % of cases–T2 breast cancer, in 70 % of cases–N0-1. Results: The median survival after TBI was 12 months, 6-month survival rate was 70 %, and 12 – month survival rate was 47.5 %. The risk of death was significantly increased (HR=3.309; 95 % CI: 1,184 – 9,250, p=0.023) in patients whose time interval from the manifestation of 1 relapse to BM was ≤24 months. In these patients, the survival was only 9.5 months and was significantly lower (p=0.0136) than in the patients with the same time interval was >24 months – 30 months. Conclusions: It was found that the effectiveness of total brain irradiation in patients with breast cancer brain metastasis is the highest if the time interval from the moment of manifestation of first relapse to brain metastasis is more than 24 months.

Plant Derived Bioactive Compounds, Their Anti-Cancer Effects and In Silico Approaches as an Alternative Target Treatment Strategy for Breast Cancer: An Updated Overview

Cancer is one of the most common malignant diseases that occur worldwide, among which breast cancer is the second leading cause of death in women. The subtypes are associated with differences in the outcome and were selected for treatments according to the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor. Triple-negative breast cancer, one of the subtypes of breast cancer, is difficult to treat and can even lead to death. If breast cancer is not treated during the initial stages, it may spread to nearby organs, a process called metastasis, through the blood or lymph system. For in vitro studies, MCF-7, MDA-MB-231, MDA-MB-468, and T47B are the most commonly used breast cancer cell lines. Clinically, chemotherapy and radiotherapy are usually expensive and can also cause side effects. To overcome these issues, medicinal plants could be the best alternative for chemotherapeutic drugs with fewer side effects and cost-effectiveness. Furthermore, the genes involved in breast cancer can be regulated and synergized with signaling molecules to suppress the proliferation of breast cancer cells. In addition, nanoparticles encapsulating (nano-encapsulation) medicinal plant extracts showed a significant reduction in the apoptotic and cytotoxic activities of breast cancer cells. This present review mainly speculates an overview of the native medicinal plant derived anti-cancerous compounds with its efficiency, types and pathways involved in breast cancer along with its genes, the mechanism of breast cancer brain metastasis, chemoresistivity and its mechanism, bioinformatics approaches which could be an effective alternative for drug discovery.

EXTH-02. AAV MEDIATED BRAIN DELIVERY OF AN ADCC-ENHANCED ANTIBODY OBVIATES XENOGRAFT GROWTH IN MOUSE MODELS OF HER2+ BREAST CANCER BRAIN METASTASIS

BACKGROUND HER2+ tumors constitute approximately 20% of breast cancer patients and are characterized by overexpression of the growth factor receptor HER2 (ERBB2), a cell proliferation driver. Effective anti-HER2 therapies confer prolonged patient survival necessitating the need for transformative treatments targeting brain metastases, a major cause of mortality in ~30-50% of HER2+ metastatic breast cancer patients. HER2-directed antibody immunotherapy, while efficacious for peripheral disease, has limited central nervous system exposure (CNS). To overcome these challenges, we transduced CNS cells with a novel AAV vector carrying an anti-HER2 antibody payload. METHODS We assessed the biochemical equivalence and functional effectiveness of AAV vector-encoded antibodies using in vitro assays. After selecting promising vector-encoded antibody candidates, a novel, blood-brain barrier penetrant AAV capsid was administered via i.v. dosing to an orthotopic xenograft mouse model of HER2+ brain metastases. Bioluminescent imaging provided a longitudinal measure of brain tumor burden. At study termination, we measured antibody biodistribution in cerebrospinal fluid (CSF), serum, and brain homogenates with AlphaLISA assays. RESULTS Using HER2+ breast cancer cell lines, we determined that an antibody-dependent cell cytotoxicity (ADCC) enhanced anti-HER2 antibody was most effective and demonstrated that AAV-vector encoded forms of the antibody performed comparably to recombinant reference antibodies. Following i.v. administration of a HER2 antibody encoding AAV vector, we measured >1 ug/mL of the antibody in CSF. Importantly, AAV-mediated expression of the ADCC-enhanced HER2-directed antibody significantly abrogated tumor growth in orthotopic xenograft models. CONCLUSIONS Peripheral administration of an AAV vector was able to transduce brain tissue such that efficacious levels of HER2-directed antibodies were produced. This strategy was successful at preventing tumor growth in our physiologically relevant model of breast cancer brain metastases. Such a treatment modality should be further evaluated in patient derived PDX models to validate translational efficacy for human patients.

TAMI-07. TUMOR-EDUCATED PLATELETS GUIDE BREAST CANCER BRAIN METASTASIS AND PROMOTE THERAPEUTIC RESISTANCE

BACKGROUND Platelets have been shown to play an important role in systemic and local tumor modulation. Once encountered by tumor cells, platelets are educated to collect and release pro-tumor factors in the tumor/microenvironment, serving as a guiding partner for metastasis. This educational program, however, is not well understood. METHODS Wild-type platelets (WTPs) were isolated from blood of healthy humans or mice, whereas tumor-educated platelets (TEPs) were isolated from blood of breast cancer patients or from tumor-bearing donor mice. The tumorigenic and modulatory effect of these two types of platelets on breast cancer was examined in-vitro and in-vivo. RESULTS Here, we show that TEPs acquire tumor promoting functions and drive breast cancer progression, metastasis to distal sites specifically the brain, as well as therapeutic resistance. Importantly, TEPs promoted an increased pro-tumorigenic effect on metastatic breast cancer, compared to their wild-type counterpart, promoting epithelial to mesenchymal transition through NF-κB/STAT3 signaling axis via C/EBPβ transcription factor. CONCLUSION Our findings point to the important role of TEPs in breast cancer brain metastasis and therapeutic resistance, which could have a major implication in other tumor types, endorsing TEPs as a potential therapeutic target.

TAMI-04. OLFACTORY RECEPTOR 5B21 DRIVES BREAST CANCER BRAIN METASTASIS THROUGH STAT3/NFΚB/CEBPΒ PATHWAY

Olfactory receptors (ORs), responsible for the sense of smell, play an essential role in various physiological processes outside the nasal epithelium, including cancer. In breast cancer, however, the expression and function of ORs remain understudied. We established a breast cancer metastasis model by intracardiac injection of MDA-MB-231 (231P) in immunocompromised mice and produced a series of derivative cell lines from developed metastatic sites, including the brain-seeking clone (231Br). We examined the significance of ORs transcript abundance in primary and metastatic breast cancer to different tissues, including the brain, bone, and lung. While 20 OR transcripts were differentially expressed in distant metastases, OR5B21 displayed high expression in all three metastatic sites with respect to the primary tumor, especially in brain metastasis with 13 fold higher than the primary site. Metastatic clones showed distinguishing higher invasion biological characteristics compared to parental cells in vivo and in vitro. Knockdown of OR5B21 significantly decreased the invasion and migration of MDA-MB-231 Brain-seeking metastatic cell as well as metastasis to different organs, including the brain, while overexpression of OR5B21 had the opposite effect. Mechanistically, OR5B21 expression was associated with epithelial to mesenchymal transition through the STAT3/NFkB/CEBPβ signaling pathway. We propose OR5B21 (and potentially other ORs) as a novel oncogene contributing to breast cancer brain metastasis and a potential target for adjuvant therapy.

INNV-02. ACCELERATING RESEARCH FOR BREAST CANCER BRAIN METASTASIS AND LEPTOMENINGEAL DISEASE THROUGH PATIENT-LED COLLABORATIONS

PATIENT-DRIVEN INITIATIVE OF THE METASTATIC BREAST CANCER (MBC) ALLIANCE The Breast Cancer Brain Metastasis (BCBM) Initiative: Marina Kaplan Project launched in June 2020 as an official project of the MBC Alliance which includes 32 nonprofits, 12 industry partners, and 30 individual patient advocates. The project has grown to include 35 members with representation from industry, research institutions, and individual patients. Nearly one-third of the group is comprised of patients living with brain metastases or LMD. DISPARITIES FOR PATIENTS LIVING WITH BCBM & LMD In the US, approximately 200,000 new cases of brain metastases are diagnosed each year.1 Approximately 10-15% of patients with MBC will develop brain metastases, and may be as high as 30-50% for certain subtypes.2 A diagnosis of central nervous system (CNS) metastasis often accelerates an already incurable diagnosis. CNS metastasis are difficult to image and detect, tend to have poorer prognoses with lower overall survival, and are treated with invasive therapies which can have lasting side effects. Furthermore, most clinical trials exclude patients with CNS metastasis which further hinders research. VALUES & OBJECTIVES The overarching goal of this initiative is to accelerate the scope and breadth of evidence-based CNS metastasis research by targeting entities conducting clinical trials and collaborating with them to do the following: (1) Increase the quality and quantity of basic research; (2) increase the number of clinical trials in areas where research is lacking; (3) diversify the type of clinical trial interventions; (4) eliminate restrictive eligibility criteria in clinical trials; (5) Incorporate clinically meaningful trial endpoints. References Eichler, April F et al. The biology of brain metastases-translation to new therapies. Nat Rev. Clinical oncology vol. 8,6 (2011): 344-56. doi: 10.1038/nrclinonc.2011.58 Brosnan EM, Anders CK. Understanding patterns of brain metastasis in breast cancer and designing rational therapeutic strategies. Ann Transl Med. 2018;6(9):163. doi: 10.21037/atm.2018.04.35

Evolution of the Tumor Microenvironment toward Immune-Suppressive Seclusion during Brain Metastasis of Breast Cancer: Implications for Targeted Therapy

Breast cancer (BC) is the second most common solid malignant tumor that metastasizes to the brain. Despite emerging therapies such as immunotherapy, whether the tumor microenvironment (TME) in breast cancer brain metastasis (BCBM) has potential as a target of new treatments is unclear. Expression profiling of 770 genes in 12 pairs of primary BC and matched brain metastasis (BM) samples was performed using the NanoString nCounter PanCancer IO360TM Panel. Immune cell profiles were validated by immunohistochemistry (IHC) in samples from 50 patients with BCBM. Pathway analysis revealed that immune-related pathways were downregulated. Immune cell profiling showed that CD8+ T cells and M1 macrophages were significantly decreased, and M2 macrophages were significantly increased, in BM compared to primary BC samples (p = 0.001, p = 0.021 and p = 0.007, respectively). CCL19 and CCL21, the top differentially expressed genes, were decreased significantly in BM compared to primary BC (p < 0.001, both). IHC showed that the CD8+ count was significantly lower (p = 0.027), and the CD163+ and CD206+ counts were higher, in BM than primary BC (p < 0.001, both). A low CD8+ T cell count, low CD86+ M1 macrophage count, and high M2/M1 macrophage ratio were related to unfavorable clinical outcomes. BC exhibits an immunosuppressive characteristic after metastasis to the brain. These findings will facilitate establishment of a treatment strategy for BCBM based on the TME of metastatic cancer.

Identification of potential genes related to breast cancer brain metastasis in breast cancer patients

Brain metastases (BM) usually develop in breast cancer patients. Thus, the molecular mechanisms of breast cancer brain metastasis (BCBM) are of great importance in designing therapeutic strategies to treat or prevent BCBM. This study attempted to identify novel diagnostic and prognostic biomarkers of BCBM. Two datasets (GSE125989 and GSE100534) were obtained from the Gene Expression Omnibus (GEO) database to find differentially expressed genes (DEGs) in cases of breast cancer with and without brain metastasis. A total of 146 overlapping DEGs, including 103 up-regulated genes and 43 down-regulated genes, were identified. Functional enrichment analysis showed that these DEGs were mainly enriched for functions including extracellular matrix organization and collagen catabolic fibril organization. Using protein-protein interaction (PPI) and principal component analysis (PCA) analysis, we identified 10 key genes, including LAMA4, COL1A1, COL5A2, COL3A1, COL4A1, COL5A1, COL5A3, COL6A3, COL6A2, and COL6A1. Additionally, COL5A1, COL4A1, COL1A1, COL6A1, COL6A2 and COL6A3 were significantly associated with the overall survival of BC patients. Furthermore, COL6A3, COL5A1, and COL4A1 were potentially correlated with BCBM in human epidermal growth factor 2 (HER2) expression. Additionally, the miR-29 family might participate in the process of metastasis by modulating the cancer microenvironment. Based on datasets in the GEO database, several DEGs have been identified as playing potentially important roles in BCBM in BC patients.