Breast cancer brain metastases

Brain metastases: Comparing clinical radiological differences in patients with lung and breast cancers treated with surgery

Purpose

Brain metastases (BMs) most frequently originate from the primary tumors of the lung and breast. Survival in patients with BM can improve if they are detected early. No studies attempt to consider all potential surgical predictive factors together by including clinical, radiological variables for their recognition.

Methods

The study aims to simultaneously analyze all clinical, radiologic, and surgical variables on a cohort of 314 patients with surgically-treated BMs to recognize the main features and differences between the two histotypes.

Results

The two groups consisted of 179 BM patients from lung cancer (Group A) and 135 patients from breast cancer (Group B). Analysis showed that BMs from breast carcinoma are more likely to appear in younger patients, tend to occur in the infratentorial site and are frequently found in patients who have other metastases outside of the brain (46 %, p = 0.05), particularly in bones. On the other hand, BMs from lung cancer often occur simultaneously with primitive diagnosis, are more commonly cystic, and have a larger edema volume. However, no differences were found in the extent of resection, postoperative complications or the presence of decreased postoperative performance status.

Conclusion

The data presented in this study reveal that while the two most prevalent forms of BM exhibit distinctions with respect to clinical onset, age, tumor location, presence of extra-cranial metastases, and lesion morphology from a strictly surgical standpoint, they are indistinguishable with regard to outcome, demonstrating comparable resection rates and a low risk of complications.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

This study, through bioinformatics analysis, unveiled SULF1 as a potential target for treating breast cancer brain metastasis (BM).

Breast adenocarcinoma cells adhere stronger to brain pericytes than to endothelial cells

Most of the malignancies detected within the brain parenchyma are of metastatic origin. As the brain lacks classical lymphatic circulation, the primary way for metastasis relies on hematogenous routes. Dissemination of metastatic cells to the brain implies attachment to the luminal surface of brain endothelial cells, transmigration through the vessel wall, and adhesion to the brain surface of the vasculature. During this process, tumor cells must interact with brain endothelial cells and later on with pericytes. Physical interaction between tumor cells and brain vascular cells might be crucial in the successful extravasation of metastatic cells through blood vessels and later in their survival within the brain environment. Therefore, we applied single-cell force spectroscopy to investigate the nanoscale adhesive properties of living breast adenocarcinoma cells to brain endothelial cells and pericytes. We found target cell type-dependent adhesion characteristics, i.e. increased adhesion of the tumor cells to pericytes in comparison to endothelial cells, which underlines the existence of metastatic potential-related nanomechanical differences relying partly on membrane tether dynamics. Varying adhesion strength of the tumor cells to different cell types of brain vessels presumably reflects the transitory adhesion to endothelial cells before extravasation and the long-lasting strong interaction with pericytes during survival and proliferation in the brain. Our results highlight the importance of specific mechanical interactions between tumor cells and host cells during metastasis formation.

Current indications and future perspectives for antibody-drug conjugates in brain metastases of breast cancer

Breast cancer is one of the main cause of cerebral and leptomeningeal metastases, the prognosis of which remains poor to this day. Most studies excluded patients with active brain metastases (BM) and particularly with leptomeningeal metastases (LM) explaining the lack of therapeutic innovation in this area. Currently, the standard management of patients with BM of breast cancer is based on the combination of surgery, radiotherapy and systemic treatments. Recently, third-generation of Antibody-Drug Conjugates (ADCs), have revolutionized the management of metastatic breast cancer. Trastuzumab deruxtecan and Sacituzumab govitecan have indeed shown significant improvements of survival outcomes and can now be used in a wide range of breast cancer subtypes. However, few data are available on the efficacy of third-generation ADCs on BM and LM of breast cancer. As the field of ADCs is rapidly evolving, with new constructs entering the late clinical development, in this review we describe the efficacy of approved and novel promising conjugates on patients with BM and LM of breast cancer.

Breast cancer brain metastasis: from etiology to state-of-the-art modeling

Currently, breast carcinoma is the most common form of malignancy and the main cause of cancer mortality in women worldwide. The metastasis of cancer cells from the primary tumor site to other organs in the body, notably the lungs, bones, brain, and liver, is what causes breast cancer to ultimately be fatal. Brain metastases occur in as many as 30% of patients with advanced breast cancer, and the 1-year survival rate of these patients is around 20%. Many researchers have focused on brain metastasis, but due to its complexities, many aspects of this process are still relatively unclear. To develop and test novel therapies for this fatal condition, pre-clinical models are required that can mimic the biological processes involved in breast cancer brain metastasis (BCBM). The application of many breakthroughs in the area of tissue engineering has resulted in the development of scaffold or matrix-based culture methods that more accurately imitate the original extracellular matrix (ECM) of metastatic tumors. Furthermore, specific cell lines are now being used to create three-dimensional (3D) cultures that can be used to model metastasis. These 3D cultures satisfy the requirement for in vitro methodologies that allow for a more accurate investigation of the molecular pathways as well as a more in-depth examination of the effects of the medication being tested. In this review, we talk about the latest advances in modeling BCBM using cell lines, animals, and tissue engineering methods.

The tumor-nerve circuit in breast cancer

It is well established that innervation is one of the updated hallmarks of cancer and that psychological stress promotes the initiation and progression of cancer. The breast tumor environment includes not only fibroblasts, adipocytes, endothelial cells, and lymphocytes but also neurons, which is increasingly discovered important in breast cancer progression. Peripheral nerves, especially sympathetic, parasympathetic, and sensory nerves, have been reported to play important but different roles in breast cancer. However, their roles in the breast cancer progression and treatment are still controversial. In addition, the brain is one of the favorite sites of breast cancer metastasis. In this review, we first summarize the innervation of breast cancer and its mechanism in regulating cancer growth and metastasis. Next, we summarize the neural-related molecular markers in breast cancer diagnosis and treatment. In addition, we review drugs and emerging technologies used to block the interactions between nerves and breast cancer. Finally, we discuss future research directions in this field. In conclusion, the further research in breast cancer and its interactions with innervated neurons or neurotransmitters is promising in the clinical management of breast cancer.

Metastatic Breast Cancer: Review of Emerging Nanotherapeutics

Metastases of breast cancer (BC) are often referred to as stage IV breast cancer due to their severity and high rate of mortality. The median survival time of patients with metastatic BC is reduced to 3 years. Currently, the treatment regimens for metastatic BC are similar to the primary cancer therapeutics and are limited to conventional chemotherapy, immunotherapy, radiotherapy, and surgery. However, metastatic BC shows organ-specific complex tumor cell heterogeneity, plasticity, and a distinct tumor microenvironment, leading to therapeutic failure. This issue can be successfully addressed by combining current cancer therapies with nanotechnology. The applications of nanotherapeutics for both primary and metastatic BC treatments are developing rapidly, and new ideas and technologies are being discovered. Several recent reviews covered the advancement of nanotherapeutics for primary BC, while also discussing certain aspects of treatments for metastatic BC. This review provides comprehensive details on the recent advancement and future prospects of nanotherapeutics designed for metastatic BC treatment, in the context of the pathological state of the disease. Furthermore, possible combinations of current treatment with nanotechnology are discussed, and their potential for future transitions in clinical settings is explored.

Brain metastasis in breast cancer: focus on genes and signaling pathways involved, blood-brain barrier and treatment strategies

Breast cancer (BC) is one of the most prevalent types of cancer in women. Despite advancement in early detection and efficient treatment, recurrence and metastasis continue to pose a significant risk to the life of BC patients. Brain metastasis (BM) reported in 17-20 percent of BC patients is considered as a major cause of mortality and morbidity in these patients. BM includes various steps from primary breast tumor to secondary tumor formation. Various steps involved are primary tumor formation, angiogenesis, invasion, extravasation, and brain colonization. Genes involved in different pathways have been reported to be associated with BC cells metastasizing to the brain. ADAM8 gene, EN1 transcription factor, WNT, and VEGF signaling pathway have been associated with primary breast tumor; MMP1, COX2, XCR4, PI3k/Akt, ERK and MAPK pathways in angiogenesis; Noth, CD44, Zo-1, CEMIP, S0X2 and OLIG2 are involved in invasion, extravasation and colonization, respectively. In addition, the blood-brain barrier is also a key factor in BM. Dysregulation of cell junctions, tumor microenvironment and loss of function of microglia leads to BBB disruption ultimately resulting in BM. Various therapeutic strategies are currently used to control the BM in BC. Oncolytic virus therapy, immune checkpoint inhibitors, mTOR-PI3k inhibitors and immunotherapy have been developed to target various genes involved in BM in BC. In addition, RNA interference (RNAi) and CRISPR/Cas9 are novel interventions in the field of BCBM where research to validate these and clinical trials are being carried out. Gaining a better knowledge of metastasis biology is critical for establishing better treatment methods and attaining long-term therapeutic efficacies against BC. The current review has been compiled with an aim to evaluate the role of various genes and signaling pathways involved in multiple steps of BM in BC. The therapeutic strategies being used currently and the novel ones being explored to control BM in BC have also been discussed at length.

Brain metastases: It takes two factors for a primary cancer to metastasize to brain

Brain metastasis of a cancer is a malignant disease with high mortality, but the cause and the molecular mechanism remain largely unknown. Using the samples of primary tumors of 22 cancer types in the TCGA database, we have performed a computational study of their transcriptomic data to investigate the drivers of brain metastases at the basic physics and chemistry level. Our main discoveries are: (i) the physical characteristics, namely electric charge, molecular weight, and the hydrophobicity of the extracellular structures of the expressed transmembrane proteins largely affect a primary cancer cell’s ability to cross the blood-brain barrier; and (ii) brain metastasis may require specific functions provided by the activated enzymes in the metastasizing primary cancer cells for survival in the brain micro-environment. Both predictions are supported by published experimental studies. Based on these findings, we have built a classifier to predict if a given primary cancer may have brain metastasis, achieving the accuracy level at AUC = 0.92 on large test sets.

Natural Bioactive Compounds Targeting Histone Deacetylases in Human Cancers: Recent Updates

Cancer is a complex pathology that causes a large number of deaths worldwide. Several risk factors are involved in tumor transformation, including epigenetic factors. These factors are a set of changes that do not affect the DNA sequence, while modifying the gene’s expression. Histone modification is an essential mark in maintaining cellular memory and, therefore, loss of this mark can lead to tumor transformation. As these epigenetic changes are reversible, the use of molecules that can restore the functions of the enzymes responsible for the changes is therapeutically necessary. Natural molecules, mainly those isolated from medicinal plants, have demonstrated significant inhibitory properties against enzymes related to histone modifications, particularly histone deacetylases (HDACs). Flavonoids, terpenoids, phenolic acids, and alkaloids exert significant inhibitory effects against HDAC and exhibit promising epi-drug properties. This suggests that epi-drugs against HDAC could prevent and treat various human cancers. Accordingly, the present study aimed to evaluate the pharmacodynamic action of different natural compounds extracted from medicinal plants against the enzymatic activity of HDAC.

The antimetastatic breast cancer activity of the viral protein-derived peptide vCPP2319 as revealed by cellular biomechanics

The incidence of metastatic breast cancer (MBC) is increasing and the therapeutic arsenal available to fight it is insufficient. Brain metastases, in particular, represent a major challenge for chemotherapy as the impermeable nature of the blood-brain barrier (BBB) prevents most drugs from targeting cells in the brain. For their ability to transpose biological membranes and transport a broad spectrum of bioactive cargoes, cell-penetrating peptides (CPPs) have been hailed as ideal candidates to deliver drugs across biological barriers. A more ambitious approach is to have the CPP as a drug itself, capable of both killing cancer cells and interacting with the blood/brain interface, therefore blocking the onset of brain metastases. vCPP2319, a viral protein-derived CPP, has both properties as it: (a) is selective toward human breast cancer cells (MDA-MB-231) and increases cell stiffness compared to breast epithelial cells (MCF 10A) hindering the progression of metastases; and (b) adsorbs at the surface of human brain endothelial cells potentially counteracting metastatic cells from reaching the brain. Overall, the results reveal the selective anticancer activity of the peptide vCPP2319, which is also able to reside at the blood-brain interface, therefore counteracting brain penetration by metastatic cancer cells.

HER2-low breast cancer could be associated with an increased risk of brain metastasis

PURPOSE

The HER2-low breast cancer is a newly recognized entity with the clinical characteristics is yet to be defined. We hypothesized that HER2-low breast cancer could lead to an increased rate of brain metastases in patients with localized breast cancer. We tested this hypothesis in a large cohort of breast cancer patients with long follow-up.

METHODS

We included 2686 adult breast cancer patients followed up in Hacettepe University Cancer Center. Patients with 1 + positive HER2 expression and 2 + HER2 expression with a negative FISH were categorized as HER2-low disease. We evaluated the brain metastasis risk with binary logistic regression analyses and reported odds ratios (OR) with 95% confidence intervals (CI).

RESULTS

During a median 95.4 (IQR 72.6-123.1) month follow-up, 184 patients developed brain metastasis (6.9%). The brain metastases were developed in 5.1% of the patients with HER2-negative disease, 8.5% of the patients with HER2-low disease, and 10.1% of the patients with HER2-positive disease. A multivariable binary logistic regression model demonstrated an increased risk of brain metastasis in patients with HER2-low disease (OR: 1.611, 95% CI 1.055-2.460, p = 0.027) and in HER2-positive patients (OR: 1.837, 95% CI 1.308-2.580, p < 0.001). Additionally, HR + -HER2-low disease was associated with a decreased DFS compared to HR + -HER2-negative disease (p = 0.008).

CONCLUSION

In this study, we observed an increased risk of brain metastasis in localized breast cancer patients with HER2-low disease. We think that a high level of vigilance and a low threshold for brain imaging could benefit HER2-low breast cancer patients similar to the patients with HER-positive disease.

Blood-Brain Barrier, Cell Junctions, and Tumor Microenvironment in Brain Metastases, the Biological Prospects and Dilemma in Therapies

Brain metastasis is the most commonly seen brain malignancy, frequently originating from lung cancer, breast cancer, and melanoma. Brain tumor has its unique cell types, anatomical structures, metabolic constraints, and immune environment, which namely the tumor microenvironment (TME). It has been discovered that the tumor microenvironment can regulate the progression, metastasis of primary tumors, and response to the treatment through the particular cellular and non-cellular components. Brain metastasis tumor cells that penetrate the brain–blood barrier and blood–cerebrospinal fluid barrier to alter the function of cell junctions would lead to different tumor microenvironments. Emerging evidence implies that these tumor microenvironment components would be involved in mechanisms of immune activation, tumor hypoxia, antiangiogenesis, etc. Researchers have applied various therapeutic strategies to inhibit brain metastasis, such as the combination of brain radiotherapy, immune checkpoint inhibitors, and monoclonal antibodies. Unfortunately, they hardly access effective treatment. Meanwhile, most clinical trials of target therapy patients with brain metastasis are always excluded. In this review, we summarized the clinical treatment of brain metastasis in recent years, as well as their influence and mechanisms underlying the differences between the composition of tumor microenvironments in the primary tumor and brain metastasis. We also look forward into the feasibility and superiority of tumor microenvironment-targeted therapies in the future, which may help to improve the strategy of brain metastasis treatment.

At the Bench: Pre-clinical evidence for multiple functions of CXCR4 in cancer

Signaling through chemokine receptor, C-X-C chemokine receptor type 4 (CXCR4) regulates essential processes in normal physiology, including embryogenesis, tissue repair, angiogenesis, and trafficking of immune cells. Tumors co-opt many of these fundamental processes to directly stimulate proliferation, invasion, and metastasis of cancer cells. CXCR4 signaling contributes to critical functions of stromal cells in cancer, including angiogenesis and multiple cell types in the tumor immune environment. Studies in animal models of several different types of cancers consistently demonstrate essential functions of CXCR4 in tumor initiation, local invasion, and metastasis to lymph nodes and distant organs. Data from animal models support clinical observations showing that integrated effects of CXCR4 on cancer and stromal cells correlate with metastasis and overall poor prognosis in >20 different human malignancies. Small molecules, Abs, and peptidic agents have shown anticancer efficacy in animal models, sparking ongoing efforts at clinical translation for cancer therapy. Investigators also are developing companion CXCR4-targeted imaging agents with potential to stratify patients for CXCR4-targeted therapy and monitor treatment efficacy. Here, pre-clinical studies demonstrating functions of CXCR4 in cancer are reviewed.

H-Ferritin nanoparticle-mediated delivery of antibodies across a BBB in vitro model for treatment of brain malignancies

Brain cancers are a group of neoplasms that can be either primary, such as glioblastoma multiforme (GBM), or metastatic, such as the HER2+ breast cancer brain metastasis. The brain represents a sanctuary for cancer cells thanks to the presence of the blood brain barrier (BBB) that controls trafficking of molecules, protecting the brain from toxic substances including drugs. Considering that GBM and HER2+ breast cancer brain metastases are characterized by EGFR and HER2 over-expression respectively, CTX- and TZ-based treatment could be effective. Several studies show that these monoclonal antibodies (mAbs) exert both a cytostatic activity interfering with the transduction pathways of EGFR family and a cytotoxic activity mainly through the immune system activation via the antibody dependent cell-mediated cytotoxicity (ADCC). Since the major limitation to therapeutic mAbs application is the presence of the BBB, here we use a recombinant form of human apoferritin (HFn) as a nanovector to promote the delivery of mAbs to the brain for the activation of the ADCC response. Using a transwell model of the BBB we proved the crossing ability of HFn-mAb. Cellular uptake of HFn-mAb by human cerebral microvascular endothelial cells (hCMEC/D3) was demonstrated by confocal microscopy. Moreover, after crossing the endothelial monolayer, HFn-conjugated mAbs retain their biological activity against targets, as assessed by MTS and ADCC assays. Our data support the use of HFn as efficient carrier to enhance the BBB crossing of mAbs, without affecting their antitumoral activity.

Ulcerated breast cancer with single brain metastasis: A combined surgical approach. Clinical presentation at one year follow up - A case report

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Solitary brain metastasis of breast cancer in a patient with neurological symptoms as first presentation is a rare complication.

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Simultaneously perform a metastasectomy surgery plus right mastectomy, right axillary dissection and immediate breast reconstruction is unusual event.

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Successful combined surgical approach in a stage IV de novo breast cancer patient with single site brain metastasis at one year follow-up.

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Combined surgical approach offers the opportunity to treat two different oncological urgencies, reducing the unnecessary repeated surgical and anesthesiologic trauma.

Introduction

Breast cancer is the most common malignancy in woman. Approximately 5–10% of breast cancer occurs as de novo stage IV and some studies have shown that from 10% to 30% of those patients presents Brain Metastasis.

Presentation of case

In this study, we report a case of solitary brain metastasis of breast cancer in a 63-year-old Italian Caucasian woman with neurological symptoms as first clinical presentation. After the correct diagnosis and multidisciplinary meeting it was decided to simultaneously perform a metastasectomy surgery plus right mastectomy, right axillary dissection and immediate breast reconstruction. In our clinical practice we report a successful combined surgical approach in a stage IV de novo breast cancer patient with single site brain metastasis at one year follow-up.

Discussion

Metastasectomy plus mastectomy provided neurological control of acute complication of metastatic disease and complete breast cancer local control. One-time operation could be the best option when diagnosis of breast cancer is made thanks to the onset of oncological emergency like intracranial hypertension due to single brain metastasis.

Conclusion

Combined surgical approach offers the opportunity to treat two different oncological urgencies, reducing the unnecessary repeated surgical and anesthesiologic trauma.

VCAM-1 targeted alpha-particle therapy for early brain metastases

BACKGROUND

Brain metastases (BM) develop frequently in patients with breast cancer. Despite the use of external beam radiotherapy (EBRT), the average overall survival is short (6 months from diagnosis). The therapeutic challenge is to deliver molecularly targeted therapy at an early stage when relatively few metastatic tumor cells have invaded the brain. Vascular cell adhesion molecule 1 (VCAM-1), overexpressed by nearby endothelial cells during the early stages of BM development, is a promising target. The aim of this study was to investigate the therapeutic value of targeted alpha-particle radiotherapy, combining lead-212 (212Pb) with an anti-VCAM-1 antibody (212Pb-αVCAM-1).

METHODS

Human breast carcinoma cells that metastasize to the brain, MDA-231-Br-GFP, were injected into the left cardiac ventricle of nude mice. Twenty-one days after injection, 212Pb-αVCAM-1 uptake in early BM was determined in a biodistribution study and systemic/brain toxicity was evaluated. Therapeutic efficacy was assessed using MR imaging and histology. Overall survival after 212Pb-αVCAM-1 treatment was compared with that observed after standard EBRT.

RESULTS

212Pb-αVCAM-1 was taken up into early BM with a tumor/healthy brain dose deposition ratio of 6 (5.52e108 and 0.92e108) disintegrations per gram of BM and healthy tissue, respectively. MRI analyses showed a statistically significant reduction in metastatic burden after 212Pb-αVCAM-1 treatment compared with EBRT (P < 0.001), translating to an increase in overall survival of 29% at 40 days post prescription (P < 0.01). No major toxicity was observed.

CONCLUSIONS

The present investigation demonstrates that 212Pb-αVCAM-1 specifically accumulates at sites of early BM causing tumor growth inhibition.

Systemic high-dose intravenous methotrexate in patients with central nervous system metastatic breast cancer

Background

Infusion of high-dose intravenous methotrexate (MTX) has been demonstrating to penetrate the blood-brain barrier. The aim of this present study was to assess the efficacy and safety of high dose MTX in patients with central nervous system (CNS) metastases of breast cancer.

Methods

Twenty-two patients with CNS metastases treated by MTX (3 g/m2) between April 2004 and October 2009 were enrolled. Clinical response rate, time to progression (TTP), overall survival (OS), and safety were assessed.

Results

In terms of brain metastases, 2 patients (9%) achieved a partial response, 10 patients (45%) had disease stabilization, and 10 patients (45%) had disease progression. In others metastatic sites, 7 patients (39%) achieved a disease stabilization, and 11 patients (61%) had disease progression. TTP and OS were 2.1 (95%CI 1.4–2.9) and 6.3 (95%CI 1.8–10) months, respectively.

Conclusion

High-dose MTX demonstrated a moderate activity at 3 g/m². Nonetheless, the favorable toxicity profile should suggest the possibility to increase the dosage and further study are planned.

Interaction of tumor cells and astrocytes promotes breast cancer brain metastases through TGF-β2/ANGPTL4 axes

Metastatic outcomes depend on the interactions of metastatic cells with a specific organ microenvironment. Our previous studies have shown that triple-negative breast cancer (TNBC) MDA-MB-231 cells passaged in astrocyte-conditioned medium (ACM) show proclivity to form brain metastases, but the underlying mechanism is unknown. The combination of microarray analysis, qPCR, and ELISA assay were carried out to demonstrate the ACM-induced expression of angiopoietin-like 4 (ANGPTL4) in TNBC cells. A stable ANGPTL4-knockdown MDA-MB-231 cell line was generated by ANGPTL4 short-hairpin RNA (shRNA) and inoculated into mice via left ventricular injection to evaluate the role of ANGPTL4 in brain metastasis formation. The approaches of siRNA, neutralizing antibodies, inhibitors, and immunoprecipitation were used to demonstrate the involved signaling molecules. We first found that ACM-conditioned TNBC cells upregulated the expression of ANGPTL4, a secreted glycoprotein whose effect on tumor progression is known to be tumor microenvironment- and tumor-type dependent. Knockdown of ANGPTL4 in TNBC MDA-MB-231 cells with shRNA decreased ACM-induced tumor cell metastatic growth in the brain and attributed to survival in a mouse model. Furthermore, we identified that astrocytes produced transforming growth factor-beta 2 (TGF-β2), which in part is responsible for upregulation of ANGPTL4 expression in TNBC through induction of SMAD signaling. Moreover, we identified that tumor cells communicate with astrocytes, where tumor cell-derived interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) increased the expression of TGF-β2 in astrocytes. Collectively, these findings indicate that the invading TNBC cells interact with astrocytes in the brain microenvironment that facilitates brain metastases of TNBC cells through a TGF-β2/ANGPTL4 axis. This provides groundwork to target ANGPTL4 as a treatment for breast cancer brain metastases.

OSM-induced CD44 contributes to breast cancer metastatic potential through cell detachment but not epithelial-mesenchymal transition

Background

Hormone receptor status in human breast cancer cells is a strong indicator of the aggressiveness of a tumor. Triple negative breast cancers (TNBC) are aggressive, difficult to treat, and contribute to high incidences of metastasis by possessing characteristics such as increased tumor cell migration and a large presence of the transmembrane protein, cluster of differentiation 44 (CD44) on the cell membrane. Estrogen receptor-positive (ER+) cells are less aggressive and do not migrate until undergoing an epithelial-mesenchymal transition (EMT).

Methods

The relationship between EMT and CD44 during metastatic events is assessed by observing changes in EMT markers, tumor cell detachment, and migration following cytokine treatment on both parental and CD44 knockdown human breast tumor cells.

Results

ER+ T47D and MCF-7 human breast cancer cells treated with OSM demonstrate increased CD44 expression and CD44 cleavage. Conversely, ER- MDA-MB-231 human breast cancer cells do not show a change in CD44 expression nor undergo EMT in the presence of OSM. In ER+ cells, knockdown expression of CD44 by shRNA did not prevent EMT but did change metastatic processes such as cellular detachment and migration. OSM-induced migration was decreased in both ER+ and ER- cells with shCD44 cells compared to control cells, while the promotion of tumor cell detachment by OSM was decreased in ER+ MCF7-shCD44 cells, as compared to control cells. Interestingly, OSM-induced detachment in ER- MDA-MB-231-shCD44 cells that normally don't detach at significant rates.

Conclusion

OSM promotes both EMT and tumor cell detachment in ER+ breast cancer cells. Yet, CD44 knockdown did not affect OSM-induced EMT in these cells, while independently decreasing OSM-induced cell detachment. These results suggest that regulation of CD44 by OSM is important for at least part of the metastatic cascade in ER+ breast cancer.

Current state of clinical trials in breast cancer brain metastases

Background

Breast cancer brain metastases (BCBM) are the final frontier in neuro-oncology for which more efficacious therapies are required. In this work, we explore clinical trials in BCBM, and determine the shortcomings in the development of new BCBM therapies to shed light on potential areas for enhancement.

Methods

On July 9, 2018, we searched ClinicalTrials.gov for all interventional and therapeutic clinical trials involving BCBM, without limiting for date or location. Information on trial characteristics, including phase, status, start and end dates, study design, primary endpoints, selection criteria, sample size, experimental interventions, results, and publications were collected and analyzed.

Results

Fifty-three trials fulfilled the selection criteria. Median trial duration across phases ranged between 3 and 6 years. More than half of the trials were conducted in the United States. Although 94% of the trials were in early phases (I-II), 20% of patients were in phase III trials. Two phase III trials were anteceded by phase II trials that were non-randomized; one reported positive results. Approximately one-third of the trials were completed, whereas 23% of trials were terminated early; mostly due to inadequate enrollment. Only 13% of all trials and 22% of completed trials had published results directly linked to their primary outcomes.

Conclusions

The low number of trials and accrual numbers, the lack of diversity, and the scarcity of published results represent the main troubles in clinical BCBM research. Optimization of BCBM trials is necessary to achieve effective therapies.

Identification of hub genes to regulate breast cancer metastasis to brain by bioinformatics analyses

Breast cancer with metastasis especially brain metastasis represents a significant cause of morbidity and mortality in patients. In this study, we aimed to investigate the hub genes and potential molecular mechanism in brain metastasis breast cancer. Expression profiles of the genes were extracted from the Gene Expression Omnibus (GEO) database. GO and KEGG pathway enrichment analyses were conducted at Database for Annotation, Visualization, and Integrated Discovery. Protein-protein interaction (PPI) network was established by STRING database constructed by Cytoscape software. Hub genes were identified by the molecular complex detection (MCODE) plugin and the CytoHubba plugin. The transcription factor (TF) that regulates the expression of hub genes was analyzed using the NetworkAnalyst algorithm. Kaplan-Meier curve was used to analyze the effects of hub genes on overall survival. Two GEO databases (GSE100534 and GSE52604) were downloaded from GEO databases. A total of 102 overlapped genes were identified, and the top five KEGG pathways enriched were pathways in cancer, HTLV-I infection, focal adhesion, ECM-receptor interaction, and protein digestion and absorption. By combing the results of MCODE and CytoHubba, a total of 10 hub genes were selected. Kaplan-Meier curve showed that ANLN, BUB1, TTK, and SKA3 were closely associated with the overall survival of breast cancer patients. TF analysis results showed that E2F4, KDM5B, and MYC were crucial regulators for these four hub genes. The current study based on the GEO database provided novel understanding regarding the mechanism of breast cancer metastasis to brain and may provide novel therapeutic targets.

Apparent diffusion coefficient histogram in breast cancer brain metastases may predict their biological subtype and progression

Our aims for this study were to investigate the relationship between diffusion weighted image (DWI) parameters of brain metastases (BMs) and biological markers of breast cancer, and moreover, to assess whether DWI parameters accurately predict patient outcomes. DWI data for 34 patients with BMs from breast cancer were retrospectively reviewed. Apparent diffusion coefficient (ADC) histogram parameters were calculated from all measurable BMs. Two region of interest (ROI) methods are used for the analysis: from the largest BM or from all measurable BMs per one patient. ADC histogram parameters were compared between positive and negative groups depending on ER/PR and HER2 statuses. Overall survival analysis after BM (OSBM) and BM-specific progression-free survival (BMPFS) was analyzed with ADC parameters. Regardless of ROI methods, 25th percentile of ADC histogram was significantly lower in the ER/PR-positive group than in the ER/PR-negative group (P < 0.05). Using ROIs from all measurable BMs, Peak location, 50th percentile, 75th percentile, and mean value of ADC histogram were also significantly lower in the ER/PR-positive group than in the ER/PR-negative group (P < 0.05). However, there was no significant difference between HER2-postive and negative group. On univariate analysis, using ROIs from all measurable BMs, lower 25th percentile, 50th percentile and mean of ADC were significant predictors for poor BMPFS. ADC histogram analysis may have a prognostic value over ER/PR status as well as BMPFS.

Investigational chemotherapy and novel pharmacokinetic mechanisms for the treatment of breast cancer brain metastases

In women, breast cancer is the most common cancer diagnosis and second most common cause of cancer death. More than half of breast cancer patients will develop metastases to the bone, liver, lung, or brain. Breast cancer brain metastases (BCBM) confers a poor prognosis, as current therapeutic options of surgery, radiation, and chemotherapy rarely significantly extend life and are considered palliative. Within the realm of chemotherapy, the last decade has seen an explosion of novel chemotherapeutics involving targeting agents and unique dosage forms. We provide a historical overview of BCBM chemotherapy, review the mechanisms of new agents such as poly-ADP ribose polymerase inhibitors, cyclin-dependent kinase 4/6 inhibitors, phosphatidyl inositol 3-kinaseinhibitors, estrogen pathway antagonists for hormone-receptor positive BCBM; tyrosine kinase inhibitors, antibodies, and conjugates for HER2+ BCBM; repurposed cytotoxic chemotherapy for triple negative BCBM; and the utilization of these new agents and formulations in ongoing clinical trials. The mechanisms of novel dosage formulations such as nanoparticles, liposomes, pegylation, the concepts of enhanced permeation and retention, and drugs utilizing these concepts involved in clinical trials are also discussed. These new treatments provide a promising outlook in the treatment of BCBM.

Synergistic tumor microenvironment targeting and blood-brain barrier penetration via a pH-responsive dual-ligand strategy for enhanced breast cancer and brain metastasis therapy

Cancer associated fibroblasts (CAFs) which shape the tumor microenvironment (TME) and the presence of blood brain barrier (BBB) remain great challenges in targeting breast cancer and its brain metastasis. Herein, we reported a strategy using PTX-loaded liposome co-modified with acid-cleavable folic acid (FA) and BBB transmigrating cell penetrating peptide dNP2 peptide (cFd-Lip/PTX) for enhanced delivery to orthotopic breast cancer and its brain metastasis. Compared with single ligand or non-cleavable Fd modified liposomes, cFd-Lip exhibited synergistic TME targeting and BBB transmigration. Moreover, upon arrival at the TME, the acid-cleavable cFd-Lip/PTX showed sensitive cleavage of FA, which reduced the hindrance effect and maximized the function of both FA and dNP2 peptide. Consequently, efficient targeting of folate receptor (FR)-positive tumor cells and FR-negative CAFs was achieved, leading to enhanced anti-tumor activity. This strategy provides a feasible approach to the cascade targeting of TME and BBB transmigration in orthotopic and metastatic cancer treatment.

Medical management of brain metastases and leptomeningeal disease in patients with breast carcinoma

Breast cancer is the most common malignancy among women and accounts for the second highest number of cancer-related deaths. With patients surviving longer due to advances in systemic control, the incidence of CNS involvement is increasing; however, the management of CNS metastases has not undergone parallel advancements. The blood–brain barrier limits the efficacy of most systemic chemotherapies, and the utilization of surgery and radiation beyond first-line therapy is limited. We will explore the recent developments in the medical management of breast cancer brain metastasis. Beyond traditional chemotherapy, we will also discuss targeted therapies and immunotherapies which may provide a survival benefit to this population and thus, offer further treatment options and a path for future research and treatment advances.

Incidental Detection of Asymptomatic Brain Metastases on 18F-fluoride Positron Emission Tomography/Computed Tomography and 68Ga DOTANOC Positron Emission Tomography/Computed Tomography in a Patient with Concomitant Breast Carcinoma and a Pancreatic Neuroendocrine Tumor

A 54-year-old female treated for locally advanced ductal breast carcinoma was also diagnosed with a pancreatic neuroendocrine tumour. A staging 68Ga DOTANOC positron emission tomography/computed tomography (PET/CT) demonstrated somatostatin receptor-positive foci within the brain parenchyma. A whole body 18F-fluoride PET/CT also demonstrated several foci of low-grade tracer uptake in the brain. Magnetic resonance imaging confirmed several cerebral and cerebellar metastases. This case highlights the need to be aware of each tumor's metastatic profile and the careful attention required for thoroughly evaluating imaging in the presence of multiple pathologies. Furthermore, such incidental findings can have significant treatment and prognostic implications.

Challenging metastatic breast cancer with the natural defensin PvD1

Metastatic breast cancer is a very serious life threatening condition that poses many challenges for the pharmaceutical development of effective chemotherapeutics. As the therapeutics targeted to the localized masses in breast improve, metastatic lesions in the brain slowly increase in their incidence compromising successful treatment outcomes overall. The blood-brain-barrier (BBB) is one important obstacle for the management of breast cancer brain metastases. New therapeutic approaches are in demand for overcoming the BBB's breaching by breast tumor cells. In this work we demonstrate the potential dual role of a natural antimicrobial plant defensin, PvD₁: it interferes with the formation of solid tumors in the breast and concomitantly controls adhesion of breast cancer cells to human brain endothelial cells. We have used a combination of techniques that probe PvD₁'s effect at the single cell level and reveal that this peptide can effectively damage breast tumor cells, leaving healthy breast and brain cells unaffected. Results suggest that PvD1 quickly internalizes in cancer cells but remains located in the membrane of normal cells with no significant damage to its structure and biomechanical properties. These interactions in turn modulate cell adhesiveness between tumor and BBB cells. PvD₁ is a potential template for the design of innovative pharmacological approaches for metastatic breast cancer treatment: the manipulation of the biomechanical properties of tumor cells that ultimately prevent their attachment to the BBB.

Probing Cell Adhesion Profiles with a Microscale Adhesive Choice Assay

In this work, we introduce, to our knowledge, a new set of adhesion-based biomarkers for characterizing mammalian cells. Mammalian cell adhesion to the extracellular matrix influences numerous physiological processes. Current in vitro methods to probe adhesion focus on adhesive force to a single surface, which can investigate only a subcomponent of the adhesive, motility, and polarization cues responsible for adhesion in the 3D tissue environment. Here, we demonstrate a method to quantify the transhesive properties of cells that relies on the microscale juxtaposition of two extracellular matrix-coated surfaces. By multiplexing this approach, we investigate the unique transhesive profiles for breast cancer cells that are adapted to colonize different metastatic sites. We find that malignant breast cancer cells readily transfer to new collagen I surfaces, and away from basement membrane proteins. Integrins and actin polymerization largely regulate this transfer. This tool can be readily adopted in cell biology and cancer research to uncover, to our knowledge, novel drivers of adhesion (or de-adhesion) and sort cell populations based on complex phenotypes with physiological relevance.

Clinical outcome of brain metastases differs significantly among breast cancer subtypes

Brain metastases in patients with breast cancer are associated with a poor survival rate. A small number of studies have challenged this premise, suggesting that survival times following brain metastasis differ significantly between breast cancer subtypes. In the current study, overall survival (OS), brain metastases-free survival (BMFS) and survival following brain metastases (SFBM) were found to be associated with the intrinsic breast cancer subtype. A total of 1,147 patients with invasive breast cancer who were treated at the Hannover Medical School between January 2004 and December 2010 were included, from which 54 patients with brain metastases were identified. The Kaplan-Meier method or Cox regression analyses were performed for analysis of survival. OS was found to differ significantly between breast cancer subtypes: OS was significantly shorter in patients with triple-negative (TN) cancer compared with patients with human epidermal growth factor receptor (HER2)-enriched tumors (P<0.001). In addition, median BMFS times differed significantly between luminal (1,003 days), HER2-enriched (514 days) and TN breast cancer patients (460 days) (P=0.045). The median durations of SFBM were 386 days in luminal, 310 days in HER2-enriched and 147 days in TN breast cancer patients (P=0.029). The results suggested that patients with luminal breast cancer have a lower risk of brain metastases and the most favorable outcome with regard to BMFS, whereas patients with HER2-positive or TN breast cancer have a significantly higher risk of developing brain metastases. Compared with TN breast cancer, the duration of SFBM was doubled in HER2-enriched cancers. These findings may have important implications for treatment and follow-up strategies in patients with breast cancer.

Cooperation of neurotrophin receptor TrkB and Her2 in breast cancer cells facilitates brain metastases

BACKGROUND

Patients with primary breast cancer that is positive for human epidermal growth factor receptor 2 (Her2+) have a high risk of developing metastases in the brain. Despite gains with systemic control of Her2+ disease using molecular therapies, brain metastases remain recalcitrant to therapeutic discovery. The clinical predilection of Her2+ breast cancer cells to colonize the brain likely relies on paracrine mechanisms. The neural niche poses unique selection pressures, and neoplastic cells that utilize the brain microenvironment may have a survival advantage.

METHODS

Tropomyosin-related kinase B (TrkB), Her2, and downstream targets were analyzed in primary breast cancer, breast-to-brain metastasis (BBM) tissues, and tumor-derived cell lines using quantitative real-time PCR, western blot, and immunohistochemical assessment. TrkB function on BBM was confirmed with intracranial, intracardiac, or mammary fat pad xenografts in non-obese diabetic/severe combined immunodeficiency mice. The function of brain-derived neurotrophic factor (BDNF) on cell proliferation and TrkB/Her2 signaling and interactions were confirmed using selective shRNA knockdown and selective inhibitors. The physical interaction of Her2-TrkB was analyzed using electron microscopy, co-immunoprecipitation, and in silico analysis. Dual targeting of Her2 and TrkB was analyzed using clinically utilized treatments.

RESULTS

We observed that patient tissues and cell lines derived from Her2+ human BBM displayed increased activation of TrkB, a neurotrophin receptor. BDNF, an extracellular neurotrophin, with roles in neuronal maturation and homeostasis, specifically binds to TrkB. TrkB knockdown in breast cancer cells led to decreased frequency and growth of brain metastasis in animal models, suggesting that circulating breast cancer cells entering the brain may take advantage of paracrine BDNF-TrkB signaling for colonization. In addition, we investigated a possible interaction between TrkB and Her2 receptors on brain metastatic breast cancer cells, and found that BDNF phosphorylated both its cognate TrkB receptor and the Her2 receptor in brain metastatic breast cancer cells.

CONCLUSION

Collectively, our findings suggest that heterodimerization of Her2 and TrkB receptors gives breast cancer cells a survival advantage in the brain and that dual inhibition of these receptors may hold therapeutic potential.

External validation of a published nomogram for prediction of brain metastasis in patients with extra-cerebral metastatic breast cancer and risk regression analysis

BACKGROUND

Survival of patients with metastatic breast cancer (MBC) suffering from brain metastasis (BM) is limited and this event is usually fatal. In 2010, the Graesslin's nomogram was published in order to predict subsequent BM in patients with breast cancer (BC) with extra-cerebral metastatic disease. This model aims to select a patient population at high risk for BM and thus will facilitate the design of prevention strategies and/or the impact of early treatment of BM in prospective clinical studies.

PATIENTS AND METHODS

Nomogram external validation was retrospectively applied to patients with BC and later BM between January 2005 and December 2012, treated in our institution. Moreover, risk factors of BM appearance were studied by Fine and Gray's competing risk analysis.

RESULTS

Among 492 patients with MBC, 116 developed subsequent BM. Seventy of them were included for the nomogram validation. The discrimination is good (area under curve = 0.695 [95% confidence interval, 0.61-0.77]). Risk factors of BM appearance are: human epidermal growth factor receptor 2 (HER2) overexpression/amplification, triple-negative BC and number of extra-cerebral metastatic sites (>1). With a competing risk model, we highlight the nomogram interest for HER2+ tumour subgroup exclusively.

CONCLUSION

Graesslin's nomogram external validation demonstrates exportability and reproducibility. Importantly, the competing risk model analysis provides additional information for the design of prospective trials concerning the early diagnosis of BM and/or preventive treatment on high risk patients with extra-cerebral metastatic BC.

Cell-Penetrating Peptide-Modified Gold Nanoparticles for the Delivery of Doxorubicin to Brain Metastatic Breast Cancer

As therapies continue to increase the lifespan of patients with breast cancer, the incidence of brain metastases has steadily increased, affecting a significant number of patients with metastatic disease. However, a major barrier toward treating these lesions is the inability of therapeutics to penetrate into the central nervous system and accumulate within intracranial tumor sites. In this study, we designed a cell-penetrating gold nanoparticle platform to increase drug delivery to brain metastatic breast cancer cells. TAT peptide-modified gold nanoparticles carrying doxorubicin led to improved cytotoxicity toward two brain metastatic breast cancer cell lines with a decrease in the IC50 of at least 80% compared to free drug. Intravenous administration of these particles led to extensive accumulation of particles throughout diffuse intracranial metastatic microsatellites with cleaved caspase-3 activity corresponding to tumor foci. Furthermore, intratumoral administration of these particles improved survival in an intracranial MDA-MB-231-Br xenograft mouse model. Our results demonstrate the promising application of gold nanoparticles for improving drug delivery in the context of brain metastatic breast cancer.

Estrogen promotes the brain metastatic colonization of triple negative breast cancer cells via an astrocyte-mediated paracrine mechanism

Brain metastases (BM) are a devastating consequence of breast cancer. BM occur more frequently in patients with estrogen receptor-negative (ER−) breast cancer subtypes; HER2 overexpressing (HER2+) tumors and triple-negative (TN) (ER−, progesterone receptor-negative (PR−) and normal HER2) tumors. Young age is an independent risk factor for development of BM, thus we speculated that higher circulating estrogens in young, pre-menopausal women could exert paracrine effects through the highly estrogen-responsive brain microenvironment. Using a TN experimental metastases model, we demonstrate that ovariectomy decreased the frequency of MRI detectable lesions by 56% as compared to estrogen supplementation, and that the combination of ovariectomy and letrozole further reduced the frequency of large lesions to 14.4% of the estrogen control. Human BM expressed 4.2-48.4% ER+ stromal area, particularly ER+ astrocytes. In vitro, E2-treated astrocytes increased proliferation, migration and invasion of 231BR-EGFP cells in an ER-dependent manner. E2 upregulated EGFR ligands Egf, Ereg, and Tgfa mRNA and protein levels in astrocytes, and activated EGFR in brain metastatic cells. Co-culture of 231BR-EGFP cells with E2-treated astrocytes led to upregulation of the metastatic mediator S100 Calcium-binding protein A4 (S100A4) (1.78-fold, P<0.05). Exogenous EGF increased S100A4 mRNA levels in 231BR-EGFP cells (1.40±0.02 fold, P<0.01 compared to vehicle-control) and an EGFR/HER2 inhibitor blocked this effect, suggesting that S100A4 is a downstream effector of EGFR activation. ShRNA-mediated S100A4 silencing in 231BR-EGFP cells decreased their migration and invasion in response to E2-CM, abolished their increased proliferation in co-cultures with E2-treated astrocytes, and decreased brain metastatic colonization. Thus, S100A4 is one effector of the paracrine action of E2 in brain metastatic cells. These studies provide a novel mechanism by which estrogens, acting through ER+ astrocytes in the brain microenvironment, can promote BM of TN breast cancers, and suggests existing endocrine agents may provide some clinical benefit towards reducing and managing BM.

Identifying risk factors for brain metastasis in breast cancer patients: Implication for a vigorous surveillance program

OBJECTIVE

Brain metastasis occurs in 10-15% of metastatic breast cancer patients and is associated with poor prognosis. This study aims to identify tumor characteristics of primary breast cancer, which are related to brain metastases in Hong Kong Chinese patients.

METHODS

A retrospective study of patients with invasive breast cancer receiving treatment in a university hospital from January 2001 to December 2008 was performed. The clinicopathological factors of patients with brain metastases were analyzed and compared with those who had no brain metastasis. Risk factors for brain metastasis were identified by univariate analysis first and then by multivariate analysis.

RESULTS

A total of 912 patients with invasive breast cancer were treated during the study period. Of these, 30 patients were found to have distant metastases to brain. Patients with brain metastases had more breast tumors of higher histological grade (Grade III, 78.9% vs. 30.2%; p = 0.001). Their tumors also had a significantly higher rate of negative estrogen receptors (78.9% vs. 30.2%, p = 0.001). On multivariate analysis, only high tumor grading was found to be predictive of developing brain metastasis.

CONCLUSION

Chinese breast cancer patients with brain metastasis were more likely to have high-grade tumors and negative estrogen receptor status. A more vigorous surveillance program for the central nervous system should be considered for this group of patients.

Local control of brain metastasis: treatment outcome of focal brain treatments in relation to subtypes

Purpose

To investigate treatment options for local control of metastasis in the brain, we compared focal brain treatment (FBT) with or without whole brain radiotherapy (WBRT) vs. WBRT alone, for breast cancer patients with tumor relapse in the brain. We also evaluated treatment outcomes according to the subtypes.

Methods

We conducted a retrospective review of breast cancer patients with brain metastasis after primary surgery. All patients received at least one local treatment for brain metastasis. Surgery or stereotactic radiosurgery was categorized as FBT. Patients were divided into two groups: the FBT group received FBT±WBRT, whereas the non-FBT group received WBRT alone. Subtypes were defined as follows: hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative, HR-positive/HER2-positive, HR-negative/HER2-positive, and triple-negative (TN). We examined the overall survival after brain metastasis (OSBM), brain metastasis-specific survival (BMSS), and brain metastasis-specific progression-free survival (BMPFS).

Results

A total of 116 patients were identified. After a median follow-up of 50.9 months, the median OSBM was 11.5 months (95% confidence interval, 9.0-14.1 months). The FBT group showed significantly superior OSBM and BMSS. However, FBT was not an independent prognostic factor for OSBM and BMSS on multivariate analyses. In contrast, multivariate analyses showed that patients who underwent surgery had improved BMPFS, indicating local control of metastasis in the brain. FBT resulted in better BMPFS in patients with HR-negative/HER2-positive cancer or the TN subtype.

Conclusion

We found that patients who underwent surgery experienced improved local control of brain metastasis, regardless of its extent. Furthermore, FBT showed positive results and could be considered for better local control of brain metastasis in patients with aggressive subtypes such as HER2-positive and TN.

Molecular determinants of lung cancer metastasis to the central nervous system

Lung cancer remains the leading cause of cancer-related mortality worldwide. The propensity for metastasis to the central nervous system (CNS) is a major clinical hurdle contributing to the low five-year survival rate of advanced disease. CNS metastases significantly outnumber primary brain tumors and carry a dismal prognosis in part due to the inability of therapeutic agents to cross the blood brain barrier. Standard treatment using radiation has been largely ineffective in improving mortality, suggesting the need for new agents targeting the critical metastatic drivers. The genetic and molecular events governing CNS metastasis from the lung are poorly understood at this time. This review highlights genetic events associated with CNS dissemination from the lung and molecular mechanisms associated with CNS metastasis. In vivo model systems that faithfully recapitulate escape from the lung and colonization of the CNS are described as tools for understanding the metastatic phenotype and for testing new therapeutic agents. A deeper understanding of the mechanisms of lung cancer metastasis to the CNS is needed to elucidate novel therapeutic avenues towards the improvement of the mortality associated with advanced stage lung cancer.

Roles of the cyclooxygenase 2 matrix metalloproteinase 1 pathway in brain metastasis of breast cancer

Brain is one of the major sites of metastasis in breast cancer; however, the pathological mechanism of brain metastasis is poorly understood. One of the critical rate-limiting steps of brain metastasis is the breaching of blood-brain barrier, which acts as a selective interface between the circulation and the central nervous system, and this process is considered to involve tumor-secreted proteinases. We analyzed clinical significance of 21 matrix metalloproteinases on brain metastasis-free survival of breast cancer followed by verification in brain metastatic cell lines and found that only matrix metalloproteinase 1 (MMP1) is significantly correlated with brain metastasis. We have shown that MMP1 is highly expressed in brain metastatic cells and is capable of degrading Claudin and Occludin but not Zo-1, which are key components of blood-brain barrier. Knockdown of MMP1 in brain metastatic cells significantly suppressed their ability of brain metastasis in vivo, whereas ectopic expression of MMP1 significantly increased the brain metastatic ability of the cells that are not brain metastatic. We also found that COX2 was highly up-regulated in brain metastatic cells and that COX2-induced prostaglandins were directly able to promote the expression of MMP1 followed by augmenting brain metastasis. Furthermore, we found that COX2 and prostaglandin were able to activate astrocytes to release chemokine (C-C motif) ligand 7 (CCL7), which in turn promoted self-renewal of tumor-initiating cells in the brain and that knockdown of COX2 significantly reduced the brain metastatic ability of tumor cells. Our results suggest the COX2-MMP1/CCL7 axis as a novel therapeutic target for brain metastasis.

Value of oncogenes for the prediction of brain metastases at initial diagnosis: a review of published data

Identifying cancer patients who are at high risk of developing brain metastases at initial diagnosis and applying effective intervention or monitoring strategies is of vital importance. Recent advances in the biology of brain metastases revealed that some oncogenes from primary tumors may be potential markers for identifying cancer patients likely to metastasize to the brain. We here summarize data on the mechanisms of brain metastases supporting the involvement of oncogene changes in the brain metastatic evolution. We also review the available evidence on clinical studies of oncogenes in the prediction of cancer patients with high incidence of brain metastases.

A novel preclinical method to quantitatively evaluate early-stage metastatic events at the murine blood-brain barrier

The observation that approximately 15% of women with disseminated breast cancer will develop symptomatic brain metastases combined with treatment guidelines discouraging single-agent chemotherapeutic strategies facilitates the desire for novel strategies aimed at outright brain metastasis prevention. Effective and robust preclinical methods to evaluate early-stage metastatic processes, brain metastases burden, and overall mean survival are lacking. Here, we develop a novel method to quantitate early metastatic events (arresting and extravasation) in addition to traditional end time-point parameters such as tumor burden and survival in an experimental mouse model of brain metastases of breast cancer. Using this method, a reduced number of viable brain-seeking metastatic cells (from 3,331 ± 263 cells/brain to 1,079 ± 495 cells/brain) were arrested in brain one week postinjection after TGFβ knockdown. Treatment with a TGFβ receptor inhibitor, galunisertib, reduced the number of arrested cells in brain to 808 ± 82 cells/brain. Furthermore, we observed a reduction in the percentage of extravasated cells (from 63% to 30%) compared with cells remaining intralumenal when TGFβ is knocked down or inhibited with galunisertib (40%). The observed reduction of extravasated metastatic cells in brain translated to smaller and fewer brain metastases and resulted in prolonged mean survival (from 36 days to 62 days). This method opens up potentially new avenues of metastases prevention research by providing critical data important to early brain metastasis of breast cancer events.

Discovery, optimization, and pharmacophore modeling of oleanolic acid and analogues as breast cancer cell migration and invasion inhibitors through targeting Brk/Paxillin/Rac1 axis

Bioassay-guided fractionation of Terminalia bentzoe L. leaves methanol extract identified the known triterpene oleanolic acid (1) as its major breast cancer cell migration inhibitor. Further chemical optimization afforded five new (9-12 and 15) and seven known (4-8, 13, and 14) semisynthetic analogues. All compounds were tested for their ability to inhibit human breast cancer MDA-MB-231 cells migration, proliferation, and invasion. The results revealed that 3-O-[N-(3'-chlorobenzenesulfonyl)-carbamoyl]-oleanolic acid (11) and 3-O-[N-(5'-fluorobenzenesulfonyl)-carbamoyl]-oleanolic acid (12) were the most active hits at low μM concentration. Western blot analysis indicated the activity of 1, 11, and 12 might be related, at least in part, to the suppression of Brk/Paxillin/Rac1 signaling pathway. Pharmacophore modeling study was conducted to better understand the common structural binding epitopes important for the antimigratory activity. The sulfonyl carbamoyl moiety with an optimal bulkiness electron-deficient phenyl ring is associated with improved activity. This study is the first to discover the antimigratory and anti-invasive activities of oleanolic acid and analogues through targeting the Brk/Paxillin/Rac1 axis.

Inhibition of type I insulin-like growth factor receptor signaling attenuates the development of breast cancer brain metastasis

Brain metastasis is a common cause of mortality in cancer patients, yet potential therapeutic targets remain largely unknown. The type I insulin-like growth factor receptor (IGF-IR) is known to play a role in the progression of breast cancer and is currently being investigated in the clinical setting for various types of cancer. The present study demonstrates that IGF-IR is constitutively autophosphorylated in brain-seeking breast cancer sublines. Knockdown of IGF-IR results in a decrease of phospho-AKT and phospho-p70s6k, as well as decreased migration and invasion of MDA-MB-231Br brain-seeking cells. In addition, transient ablation of IGFBP3, which is overexpressed in brain-seeking cells, blocks IGF-IR activation. Using an in vivo experimental brain metastasis model, we show that IGF-IR knockdown brain-seeking cells have reduced potential to establish brain metastases. Finally, we demonstrate that the malignancy of brain-seeking cells is attenuated by pharmacological inhibition with picropodophyllin, an IGF-IR-specific tyrosine kinase inhibitor. Together, our data suggest that the IGF-IR is an important mediator of brain metastasis and its ablation delays the onset of brain metastases in our model system.

The proinflammatory peptide substance P promotes blood-brain barrier breaching by breast cancer cells through changes in microvascular endothelial cell tight junctions

Neuropeptide substance P (SP) has been implicated in inflammation, pain, depression and breast cancer cell (BCC) growth. Here, we examined the role of SP in trafficking of BCCs (human MDA-MB-231 and MDA-MB-231BrM2 cells) across the blood-brain barrier (BBB) and brain microvascular endothelial cells (BMECs) using in vitro and in vivo models. SP was secreted from BCCs and mediated adhesion and transmigration of BCCs across human BMECs (HBMECs) in vitro. SP induced activation of HBMECs, leading to secretion of Tumor Necrosis Factor alpha (TNF-α) and angiopoietin-2 (Ang-2) from HBMECs, resulting in changes in localization and distribution of tight junction (TJ) ZO-1 (tight junction protein zonula occludins-1) and claudin-5 structures as well as increased permeability of HBMECs. Using spontaneous breast cancer metastasis mouse model (syngeneic) of GFP-4T1-BrM5 mammary tumor cells administered into mammary fat pads of Balb/c mice, SP inhibitor spantide III inhibited in vivo changes in permeability of the BBB and BMEC-TJs ZO-1 and claudin-5 structures as well as decreased tumor cell colonization in brain. Thus, SP secreted from BCCs induces transmigration of BCCs across the BBB, leading to activation of BMECs and secretion of TNF-α and Ang-2, resulting in BBB impairment and colonization of tumor cells in brain. Therefore, therapies based on SP inhibition in combination with other therapies may prevent breaching of the BBB by BCCs and their colonization in brain.

Combined alloreactive CTL cellular therapy with prodrug activator gene therapy in a model of breast cancer metastatic to the brain

PURPOSE

Individual or combined strategies of cellular therapy with alloreactive CTLs (alloCTL) and gene therapy using retroviral replicating vectors (RRV) encoding a suicide prodrug activating gene were explored for the treatment of breast tumors metastatic to the brain.

EXPERIMENTAL DESIGN

AlloCTL, sensitized to the HLA of MDA-MB-231 breast cancer cells, were examined in vitro for antitumor functionality toward breast cancer targets. RRV encoding the yeast cytosine deaminase (CD) gene was tested in vivo for virus spread, ability to infect, and kill breast cancer targets when exposed to 5-fluorocytosine (5-FC). Individual and combination treatments were tested in subcutaneous and intracranial xenograft models with 231BR, a brain tropic variant.

RESULTS

AlloCTL preparations were cytotoxic, proliferated, and produced IFN-γ when coincubated with target cells displaying relevant HLA. In vivo, intratumorally placed alloCTL trafficked through one established intracranial 231BR focus to another in contralateral brain and induced tumor cell apoptosis. RRV-CD efficiently spread in vivo, infected 231BR and induced their apoptosis upon 5-FC exposure. Subcutaneous tumor volumes were significantly reduced in alloCTL and/or gene therapy-treated groups compared to control groups. Mice with established intracranial 231BR tumors treated with combined alloCTL and RRV-CD had a median survival of 97.5 days compared with single modalities (50-83 days); all experimental treatment groups survived significantly longer than sham-treated groups (median survivals 31.5 or 40 days) and exhibited good safety/toxicity profiles.

CONCLUSION

The results indicate combining cellular and suicide gene therapies is a viable strategy for the treatment of established breast tumors in the brain.

Co-evolution of breast-to-brain metastasis and neural progenitor cells

Brain colonization by metastatic tumor cells offers a unique opportunity to investigate microenvironmental influences on the neoplastic process. The bi-directional interplay of breast cancer cells (mesodermal origin) and brain cells (neuroectodermal origin) is poorly understood and rarely investigated. In our patients undergoing neurosurgical resection of breast-to-brain metastases, specimens from the tumor/brain interface exhibited increased active gliosis as previously described. In addition, our histological characterization revealed infiltration of neural progenitor cells (NPCs) both outside and inside the tumor margin, leading us to investigate the cellular and molecular interactions between NPCs and metastases. Since signaling by the TGF-β superfamily is involved in both developmental neurobiology and breast cancer pathogenesis, we examined the role of these proteins in the context of brain metastases. The brain-metastatic breast cancer cell line MDA-MB-231Br (231Br) expressed BMP-2 at significantly higher levels compared to its matched primary breast cancer cell line MDA-MB-231 (231). Co-culturing was used to examine bi-directional cellular effects and the relevance of BMP-2 overexpression. When co-cultured with NPCs, 231 (primary) tumor cells failed to proliferate over 15 days. However, 231Br (brain metastatic) tumor cells co-cultured with NPCs escaped growth inhibition after day 5 and proliferated, occurring in parallel with NPC differentiation into astrocytes. Using shRNA and gene knock-in, we then demonstrated BMP-2 secreted by 231Br cells mediated NPC differentiation into astrocytes and concomitant tumor cell proliferation in vitro. In xenografts, overexpression of BMP-2 in primary breast cancer cells significantly enhanced their ability to engraft and colonize the brain, thereby creating a metastatic phenotype. Conversely, BMP-2 knockdown in metastatic breast cancer cells significantly diminished engraftment and colonization. The results suggest metastatic tumor cells create a permissive neural niche by steering NPC differentiation toward astrocytes through paracrine BMP-2 signaling.

Predictive factors of brain metastasis in patients with breast cancer

The aim of this study is to determine the risk factors associated with metastasis to the brain of primary breast cancer patients and evaluate a predictive model. The clinicopathological characteristics of 206 patients with primary breast cancer were analyzed retrospectively with a univariate and multivariate logistic regression model. A predictive model was generated, and its validity evaluated with a receiver operating characteristic (ROC) curve. Independent risk factors for brain metastasis in patients with primary breast cancer were: being younger than 35 years old at the time of diagnosis, having four or more metastatic axillary nodes, being estrogen receptor-negative, and with 24 months of metastasis-free survival. The predictive value of the brain metastasis risk model, measured as the area under the ROC curve, was 0.765 ± 0.040 (95 % CI 0.688-0.842). When 0.8 was considered the cutoff point of probability calculated by the model, the sensitivity and specificity for predicting the occurrence of brain metastases in these patients were 0.769 and 0.713, respectively. The predictive model constructed in this study can be used to forecast brain metastasis in breast cancer. Patients with a predictive level ≥0.8 could be treated preventively for brain metastases.

Current advances in understanding and managing secondary brain metastasis

Metastatic brain tumors are the number one cause of intracranial neoplasms in adults and are associated with higher morbidity and mortality. The frequency of metastatic brain tumors is increasing because of improved survival in cancer patients. The molecular mechanism of brain metastasis is complex and not completely known. Vasogenic edema produced by tumor-derived VEGF is responsible for clinical symptoms. Dexamethasone remains the mainstay of medical management with not completely known mechanisms of action. Surgery and radiation are the main treatment modalities for metastatic brain tumors. Systemic chemotherapy has a very limited role in treatment of these tumors. Leptomeningeal metastasis is associated with extremely poor outcome.