Identification of brain metastasis genes and therapeutic evaluation of histone deacetylase inhibitors in a clinically relevant model of breast cancer brain metastasis

Current preclinical models of brain metastasis

Brain metastases (BMs) represent the most prevalent intracranial malignancy within the adult. They are identified in up to 20% of patients with solid tumors and this percentage varies between tumor types and age. Due to the selective permeability of the blood-brain barrier, most anticancer drugs can't reach significant concentrations in the brain, representing a major obstacle to the patients' survival. Furthermore, intra- and inter-patient heterogeneity and the unique brain microenvironment add a layer of complexity to the clinical management of BMs. In the perspective of finding new therapeutic approaches and better understanding the molecular mechanisms involved in brain metastasis, the use of appropriate preclinical models is essential. Here, we review current in vivo, in vitro and ex vivo models for the study of brain metastasis while outlining their advantages and limitations.

The origin of brain malignancies at the blood-brain barrier

Despite improvements in extracranial therapy, survival rate for patients suffering from brain metastases remains very poor. This is coupled with the incidence of brain metastases continuing to rise. In this review, we focus on core contributions of the blood-brain barrier to the origin of brain metastases. We first provide an overview of the structure and function of the blood-brain barrier under physiological conditions. Next, we discuss the emerging idea of a pre-metastatic niche, namely that secreted factors and extracellular vesicles from a primary tumor site are able to travel through the circulation and prime the neurovasculature for metastatic invasion. We then consider the neurotropic mechanisms that circulating tumor cells possess or develop that facilitate disruption of the blood-brain barrier and survival in the brain's parenchyma. Finally, we compare and contrast brain metastases at the blood-brain barrier to the primary brain tumor, glioma, examining the process of vessel co-option that favors the survival and outgrowth of brain malignancies.

Identifying cancer-associated leukocyte profiles using high-resolution flow cytometry screening and machine learning

Background

Machine learning (ML) is a valuable tool with the potential to aid clinical decision making. Adoption of ML to this end requires data that reliably correlates with the clinical outcome of interest; the advantage of ML is that it can model these correlations from complex multiparameter data sets that can be difficult to interpret conventionally. While currently available clinical data can be used in ML for this purpose, there exists the potential to discover new "biomarkers" that will enhance the effectiveness of ML in clinical decision making. Since the interaction of the immune system and cancer is a hallmark of tumor establishment and progression, one potential area for cancer biomarker discovery is through the investigation of cancer-related immune cell signatures. Hence, we hypothesize that blood immune cell signatures can act as a biomarker for cancer progression.

Methods

To probe this, we have developed and tested a multiparameter cell-surface marker screening pipeline, using flow cytometry to obtain high-resolution systemic leukocyte population profiles that correlate with detection and characterization of several cancers in murine syngeneic tumor models.

Results

We discovered a signature of several blood leukocyte subsets, the most notable of which were monocyte subsets, that could be used to train CATboost ML models to predict the presence and type of cancer present in the animals.

Conclusions

Our findings highlight the potential utility of a screening approach to identify robust leukocyte biomarkers for cancer detection and characterization. This pipeline can easily be adapted to screen for cancer specific leukocyte markers from the blood of cancer patient.

Copper chelation suppresses epithelial-mesenchymal transition by inhibition of canonical and non-canonical TGF-β signaling pathways in cancer

BACKGROUND

Metastatic cancer cells exploit Epithelial-mesenchymal-transition (EMT) to enhance their migration, invasion, and resistance to treatments. Recent studies highlight that elevated levels of copper are implicated in cancer progression and metastasis. Clinical trials using copper chelators are associated with improved patient survival; however, the molecular mechanisms by which copper depletion inhibits tumor progression and metastasis are poorly understood. This remains a major hurdle to the clinical translation of copper chelators. Here, we propose that copper chelation inhibits metastasis by reducing TGF-β levels and EMT signaling. Given that many drugs targeting TGF-β have failed in clinical trials, partly because of severe side effects arising in patients, we hypothesized that copper chelation therapy might be a less toxic alternative to target the TGF-β/EMT axis.

RESULTS

Our cytokine array and RNA-seq data suggested a link between copper homeostasis, TGF-β and EMT process. To validate this hypothesis, we performed single-cell imaging, protein assays, and in vivo studies. Here, we used the copper chelating agent TEPA to block copper trafficking. Our in vivo study showed a reduction of TGF-β levels and metastasis to the lung in the TNBC mouse model. Mechanistically, TEPA significantly downregulated canonical (TGF-β/SMAD2&3) and non-canonical (TGF-β/PI3K/AKT, TGF-β/RAS/RAF/MEK/ERK, and TGF-β/WNT/β-catenin) TGF-β signaling pathways. Additionally, EMT markers of MMP-9, MMP-14, Vimentin, β-catenin, ZEB1, and p-SMAD2 were downregulated, and EMT transcription factors of SNAI1, ZEB1, and p-SMAD2 accumulated in the cytoplasm after treatment.

CONCLUSIONS

Our study suggests that copper chelation therapy represents a potentially effective therapeutic approach for targeting TGF-β and inhibiting EMT in a diverse range of cancers.

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.

Integrin αvβ3 Is a Master Regulator of Resistance to TKI-Induced Ferroptosis in HER2-Positive Breast Cancer

Human epidermal growth factor receptor-2 (HER2)-targeting therapies provide clinical benefits for patients with HER2-positive breast cancer. However, the resistance to monotherapies invariably develops and leads to disease relapse and treatment failure. Previous studies have demonstrated a link between the potency of HER2-targeting tyrosine kinase inhibitors (TKIs) and their ability to induce an iron-dependent form of cell death called ferroptosis. The aim of this study was to understand the mechanisms of resistance to TKI-induced ferroptosis and identify novel approaches to overcome treatment resistance. We used mouse and human HER2-positive models of acquired TKI resistance to demonstrate an intimate link between the resistance to TKIs and to ferroptosis and present the first evidence that the cell adhesion receptor αvβ3 integrin is a critical mediator of resistance to TKI-induced ferroptosis. Our findings indicate that αvβ3 integrin-mediated resistance is associated with the re-wiring of the iron/antioxidant metabolism and persistent activation of AKT signalling. Moreover, using gene manipulation approaches and pharmacological inhibitors, we show that this "αvβ3 integrin addiction" can be targeted to reverse TKI resistance. Collectively, these findings provide critical insights into new therapeutic strategies to improve the treatment of advanced HER2-positive breast cancer patients.

Target-based in-silico screening of basil polysaccharides against different epigenetic targets responsible for breast cancer

PURPOSE

Breast cancer (BC) is one of the leading types of cancer found in women. One of the causes reported for BC is improper regulation of epigenetic modifications. Various epigenetic targets such as histone deacetylases (HDAC) and histone acetyltransferases (HAT) regulate many types of cancer, including BC. Basil is known to possess anti-cancer properties; however, the role of its polysaccharides against different epigenetic targets is still not very clear. Therefore, the molecular docking method is used to find out the binding potential of the BPSs against different epigenetic targets responsible for BC.

METHODS

All the basil polysaccharides (BPSs) were screened against the diverse epigenetic targets reported for BC (HDAC1-2, 4-8, and HAT) using molecular docking studies alongwith swissADME studies to check the drug likeliness of the BPSs.

RESULTS

It was found that glucosamine ring, glucosamine linear, glucuronic acid linear, rhamnose linear, glucuronic acid ring, galactose ring, mannose, glucose, and xylose were exhibited consistent binding potential against the epigenetic targets (HDAC1, HDAC2, HDAC4, HDAC5, HDAC6, HDAC7, HDAC8, and HAT,) responsible for BC.

CONCLUSION

This is the first report where BPSs were reported against these epigenetic targets. These studies can help to understand the underlying mechanism of BPSs used against epigenetic targets for BC. These results can be further validated experimentally to confirm their potential as a promising inhibitor against the epigenetic targets (HDAC1-2, 4-8, and HAT) having a role in BC.

Benzimidazoles Against Certain Breast Cancer Drug Targets: A Review

BACKGROUND

Benzimidazoles are widely used scaffolds against various types of cancer including breast cancer. To this end, anticancer agents must be developed using the knowledge of the specific targets of BC.

OBJECTIVE

In this study, we aim to review the compounds used against some of the biomolecular targets of breast cancer. To this end, we present information about the various targets, with their latest innovative studies.

CONCLUSION

Benzimidazole ring is an important building block that can target diverse cancer scenarios since it can structurally mimic biomolecules in the human body. Additionally, many studies imply the involvement of this moiety on a plethora of pathways and enzymes related to BC. Herein, our target-based collection of benzimidazole derivatives strongly suggests the utilization of benzimidazole derivatives against BC.

Preclinical Models of Brain Metastases in Breast Cancer

Breast cancer remains a leading cause of mortality among women worldwide. Brain metastases confer extremely poor prognosis due to a lack of understanding of their specific biology, unique physiologic and anatomic features of the brain, and limited treatment strategies. A major roadblock in advancing the treatment of breast cancer brain metastases (BCBM) is the scarcity of representative experimental preclinical models. Current models are predominantly based on the use of animal xenograft models with immortalized breast cancer cell lines that poorly capture the disease’s heterogeneity. Recent years have witnessed the development of patient-derived in vitro and in vivo breast cancer culturing systems that more closely recapitulate the biology from individual patients. These advances led to the development of modern patient-tissue-based experimental models for BCBM. The success of preclinical models is also based on the imaging technologies used to detect metastases. Advances in animal brain imaging, including cellular MRI and multimodality imaging, allow sensitive and specific detection of brain metastases and monitoring treatment responses. These imaging technologies, together with novel translational breast cancer models based on patient-derived cancer tissues, represent a unique opportunity to advance our understanding of brain metastases biology and develop novel treatment approaches. This review discusses the state-of-the-art knowledge in preclinical models of this disease.

Brain Vascular Microenvironments in Cancer Metastasis

Primary tumours, particularly from major solid organs, are able to disseminate into the blood and lymphatic system and spread to distant sites. These secondary metastases to other major organs are the most lethal aspect of cancer, accounting for the majority of cancer deaths. The brain is a frequent site of metastasis, and brain metastases are often fatal due to the critical role of the nervous system and the limited options for treatment, including surgery. This creates a need to further understand the complex cell and molecular biology associated with the establishment of brain metastasis, including the changes to the environment of the brain to enable the arrival and growth of tumour cells. Local changes in the vascular network, immune system and stromal components all have the potential to recruit and foster metastatic tumour cells. This review summarises our current understanding of brain vascular microenvironments, fluid circulation and drainage in the context of brain metastases, as well as commenting on current cutting-edge experimental approaches used to investigate changes in vascular environments and alterations in specialised subsets of blood and lymphatic vessel cells during cancer spread to the brain.

Tracing bone marrow-derived microglia in brain metastatic tumors

Microglia are the resident macrophages in the central nervous system (CNS), and they constitute 15-20% of the total glial populations. They have wide developmental and protective functions during brain injury, infection and tumorigenesis. Originally thought to derive from postnatal hematopoietic progenitors, it has recently been demonstrated that microglia originate from primitive myeloid progenitor cells that arise during early development from the embryonic yolk sac. Circulating monocytes infiltrate the CNS upon inflammatory conditions, such as cancer, primarily differentiating into macrophages and dendritic cells. Both resident and recruited microglia respond to environmental cues and actively participate in pathogenic processes, albeit their transcriptomic profiles contain significant differences suggesting distinctive roles. Metastatic brain tumors are the most common intracranial neoplasm in adults, with an estimate incidence 10 times higher than all primary brain neoplasms combined, and with dismal prognosis. Microglia is a major immune population associated with brain metastatic tumors in patients. They are proposed to play multiple, and sometimes opposing roles, in tumor progression. However, our ability to evaluate individual contribution of resident and recruited populations is hindered by the fact that they express overlapping sets of surface markers. Tracking and interrogating tissue-resident vs recruited microglia in the brain tumor microenvironment becomes critical to dissect their respective roles and gain a better understanding of the mechanism governing their interaction. In this chapter, we describe the utilization of genetic reporter mice to identify recruited brain microglia, offer a comparison between the genetic method and the most widely used flow cytometric approach, and discuss potential downstream applications to interrogate BMDM function in brain metastatic disease.

Blocking c-MET/ERBB1 Axis Prevents Brain Metastasis in ERBB2+ Breast Cancer

Simple Summary

Targeted monotherapies are ineffective in the treatment of brain metastasis of ERBB2⁺ breast cancer (BC) underscoring the need for combination therapies. The lack of robust preclinical models has further hampered the assessment of treatment modalities. We report here a clinically relevant orthotopic mouse model of ERBB2⁺ BC that spontaneously metastasizes to brain and demonstrates that targeting the c-MET/ERBB1 axis with a combination of cabozantinib and neratinib decreases primary tumor growth and prevents brain metastasis in ERBB2⁺ BC.

Abstract

Brain metastasis (BrM) remains a significant cause of cancer-related mortality in epidermal growth factor receptor 2-positive (ERBB2⁺) breast cancer (BC) patients. We proposed here that a combination treatment of irreversible tyrosine kinase inhibitor neratinib (NER) and the c-MET inhibitor cabozantinib (CBZ) could prevent brain metastasis. To address this, we first tested the combination treatment of NER and CBZ in the brain-seeking ERBB2⁺ cell lines SKBrM3 and JIMT-1-BR3, and in ERBB2⁺ organoids that expressed the c-MET/ERBB1 axis. Next, we developed and characterized an orthotopic mouse model of spontaneous BrM and evaluated the therapeutic effect of CBZ and NER in vivo. The combination treatment of NER and CBZ significantly inhibited proliferation and migration in ERBB2⁺ cell lines and reduced the organoid growth in vitro. Mechanistically, the combination treatment of NER and CBZ substantially inhibited ERK activation downstream of the c-MET/ERBB1 axis. Orthotopically implanted SKBrM3⁺ cells formed primary tumor in the mammary fat pad and spontaneously metastasized to the brain and other distant organs. Combination treatment with NER and CBZ inhibited primary tumor growth and predominantly prevented BrM. In conclusion, the orthotopic model of spontaneous BrM is clinically relevant, and the combination therapy of NER and CBZ might be a useful approach to prevent BrM in BC.

Aberrant HDAC3 expression correlates with brain metastasis in breast cancer patients

BACKGROUND

Brain metastasis is an unsolved clinical problem in breast cancer patients due to its poor prognosis and high fatality rate. Although accumulating evidence has shown that some pan-histone deacetylase (HDAC) inhibitors can relieve breast cancer brain metastasis, the specific HDAC protein involved in this process is unclear. Thus, identifying a specific HDAC protein closely correlated with breast cancer brain metastasis will not only improve our understanding of the functions of the HDAC family but will also help develop a novel target for precision cancer therapy.

METHODS

Immunohistochemical staining of HDAC1, HDAC2, and HDAC3 in 161 samples from breast invasive ductal carcinoma patients, including 63 patients with brain metastasis, was performed using the standard streptavidin-peroxidase method. The relationships between HDAC1, HDAC2, and HDAC3 and overall survival/brain metastasis-free survival/post-brain metastatic survival were evaluated using Kaplan-Meier curves and Cox regression analyses.

RESULTS

HDAC1, HDAC2, and cytoplasmic HDAC3 all displayed typical oncogenic characteristics and were independent prognostic factors for the overall survival of breast cancer patients. Only cytoplasmic HDAC3 was an independent prognostic factor for brain metastasis-free survival. Cytoplasmic expression of HDAC3 was further upregulated in the brain metastases compared with the matched primary tumors, while nuclear expression was downregulated. The HDAC1, HDAC2, and HDAC3 expression levels in the brain metastases were not correlated with survival post-brain metastasis.

CONCLUSIONS

Our studies first demonstrate a critical role for HDAC3 in the brain metastasis of breast cancer patients and it may serve as a promising therapeutic target for the vigorously developing field of precision medicine.

KEY POINTS

Significant findings of the study Cytoplasmic HDAC3 is an independent prognostic factor for the overall survival and brain metastasis-free survival of breast cancer patients. What this study adds Cytoplasmic expression of HDAC3 was further upregulated in the brain metastases compared with the matched primary tumours, while nuclear expression was downregulated.

Marizomib suppresses triple-negative breast cancer via proteasome and oxidative phosphorylation inhibition

Purpose: Lacking effective targeted therapies, triple-negative breast cancer (TNBCs) is highly aggressive and metastatic disease, and remains clinically challenging breast cancer subtype to treat. Despite the survival dependency on the proteasome pathway genes, FDA-approved proteasome inhibitors induced minimal clinical response in breast cancer patients due to weak proteasome inhibition. Hence, developing effective targeted therapy using potent proteasome inhibitor is required.

Methods: We evaluated anti-cancer activity of a potent proteasome inhibitor, marizomib, in vitro using breast cancer lines and in vivo using 4T1.2 murine syngeneic model, MDA-MB-231 xenografts, and patient-derived tumor xenografts. Global proteome profiling, western blots, and RT-qPCR were used to investigate the mechanism of action for marizomib. Effect of marizomib on lung and brain metastasis was evaluated using syngeneic 4T1BR4 murine TNBC model in vivo.

Results: We show that marizomib inhibits multiple proteasome catalytic activities and induces a better anti-tumor response in TNBC cell lines and patient-derived xenografts alone and in combination with the standard-of-care chemotherapy. Mechanistically, we show that marizomib is a dual inhibitor of proteasome and oxidative phosphorylation (OXPHOS) in TNBCs. Marizomib reduces lung and brain metastases by reducing the number of circulating tumor cells and the expression of genes involved in the epithelial-to-mesenchymal transition. We demonstrate that marizomib-induced OXPHOS inhibition upregulates glycolysis to meet the energetic demands of TNBC cells and combined inhibition of glycolysis with marizomib leads to a synergistic anti-cancer activity.

Conclusions: Our data provide a strong rationale for a clinical evaluation of marizomib in primary and metastatic TNBC patients.

Pracinostat (SB939), a histone deacetylase inhibitor, suppresses breast cancer metastasis and growth by inactivating the IL-6/STAT3 signalling pathways

AIMS

Histone deacetylases inhibitors have shown favorable antitumor activity in clinical investigations. In the present study, we assessed the effects of a novel hydroxamic acid-based HDAC inhibitor, SB939, on breast cancer metastasis and tumor growth and characterized the underlying molecular mechanisms.

MAIN METHODS

MTS, Wound-healing, and Transwell chamber invasion assays were used to detect the inhibition effects of SB939 on proliferation, migration, and invasion of breast cancer cells. Western blot, cellular immunofluorescence, and EMSA were used to explore the molecular mechanism of SB939 in suppressing breast cancer metastasis. MDA-MB-231 subcutaneous tumor-bearing model of nude mice and the spontaneous metastasis model of breast cancer were both applied to verify in vivo anti-tumor growth and anti-metastatic effects.

KEY FINDINGS

Our results demonstrated that SB939 at 0.5-1 μmol/L markedly impaired the chemotactic motility of breast cancer cells. SB939 reversed epithelial-mesenchymal transition (EMT) process, as evidenced by upregulation E-cadherin expression and downregulation expressions of N-cadherin and vimentin through increasing the levels of ac-histone H3 and H4 and drecreasing the expressiongs of HDAC 5 and 4. This cascade inhibition mediated by SB939 was well interpreted by inactivating phosphorylation of STAT3, blocking its DNA-binding activity, and decreasing the expressions of STAT3-dependent target genes, including MMP2 and MMP9. Furhtermore, we found that SB939 significantly inhibited breast cancer metastasis and tumor growth in vivo and showed superior anti-tumor properties compared with SAHA in two breast cancer animal models.

SIGNIFICANCE

Our findings indicate that SB939 may be an effective therapeutic option for treating advanced breast cancer.

Bifunctional Aptamer-Doxorubicin Conjugate Crosses the Blood-Brain Barrier and Selectively Delivers Its Payload to EpCAM-Positive Tumor Cells

The prognosis for breast cancer patients diagnosed with brain metastases is poor, with survival time measured merely in months. This can largely be attributed to the limited treatment options capable of reaching the tumor as a result of the highly restrictive blood-brain barrier (BBB). While methods of overcoming this barrier have been developed and employed with current treatment options, the majority are highly invasive and nonspecific, leading to severe neurotoxic side effects. A novel approach to address these issues is the development of therapeutics targeting receptor-mediated transport mechanisms on the BBB endothelial cell membranes. Using this approach, we intercalated doxorubicin (DOX) into a bifunctional aptamer targeting the transferrin receptor on the BBB and epithelial cell adhesion molecule (EpCAM) on metastatic cancer cells. The ability of the DOX-loaded aptamer to transcytose the BBB and selectively deliver the payload to EpCAM-positive tumors was evaluated in an in vitro model and confirmed for the first time in vivo using the MDA-MB-231 breast cancer metastasis model (MDA-MB-231Br). We show that colocalized aptamer and DOX are clearly detectable within the brain lesions 75 min postadministration. Collectively, results from this study demonstrate that through intercalation of a cytotoxic drug into the bifunctional aptamer, a therapeutic delivery vehicle can be developed for specific targeting of EpCAM-positive brain metastases.

Tissue Architectural Cues Drive Organ Targeting of Tumor Cells in Zebrafish

Tumor cells encounter a myriad of physical cues upon arrest and extravasation in capillary beds. Here, we examined the role of physical factors in non-random organ colonization using a zebrafish xenograft model. We observed a two-step process by which mammalian mammary tumor cells showed non-random organ colonization. Initial homing was driven by vessel architecture, where greater numbers of cells became arrested in the topographically disordered blood vessels of the caudal vascular plexus (CVP) than in the linear vessels in the brain. Following arrest, bone-marrow- and brain-tropic clones exhibited organ-specific patterns of extravasation. Extravasation was mediated by β1 integrin, where knockdown of β1 integrin reduced extravasation in the CVP but did not affect extravasation of a brain-tropic clone in the brain. In contrast, silencing myosin 1B redirected early colonization from the brain to the CVP. Our results suggest that organ selectivity is driven by both vessel topography and cell-type-dependent extravasation.

Neoadjuvant neratinib promotes ferroptosis and inhibits brain metastasis in a novel syngeneic model of spontaneous HER2+ve breast cancer metastasis

Background

Human epidermal growth factor receptor-2 (HER2)-targeted therapies prolong survival in HER2-positive breast cancer patients. Benefit stems primarily from improved control of systemic disease, but up to 50% of patients progress to incurable brain metastases due to acquired resistance and/or limited permeability of inhibitors across the blood-brain barrier. Neratinib, a potent irreversible pan-tyrosine kinase inhibitor, prolongs disease-free survival in the extended adjuvant setting, and several trials evaluating its efficacy alone or combination with other inhibitors in early and advanced HER2-positive breast cancer patients are ongoing. However, its efficacy as a first-line therapy against HER2-positive breast cancer brain metastasis has not been fully explored, in part due to the lack of relevant pre-clinical models that faithfully recapitulate this disease. Here, we describe the development and characterisation of a novel syngeneic model of spontaneous HER2-positive breast cancer brain metastasis (TBCP-1) and its use to evaluate the efficacy and mechanism of action of neratinib.

Methods

TBCP-1 cells were derived from a spontaneous BALB/C mouse mammary tumour and characterised for hormone receptors and HER2 expression by flow cytometry, immunoblotting and immunohistochemistry. Neratinib was evaluated in vitro and in vivo in the metastatic and neoadjuvant setting. Its mechanism of action was examined by transcriptomic profiling, function inhibition assays and immunoblotting.

Results

TBCP-1 cells naturally express high levels of HER2 but lack expression of hormone receptors. TBCP-1 tumours maintain a HER2-positive phenotype in vivo and give rise to a high incidence of spontaneous and experimental metastases in the brain and other organs. Cell proliferation/viability in vitro is inhibited by neratinib and by other HER2 inhibitors, but not by anti-oestrogens, indicating phenotypic and functional similarities to human HER2-positive breast cancer. Mechanistically, neratinib promotes a non-apoptotic form of cell death termed ferroptosis. Importantly, metastasis assays demonstrate that neratinib potently inhibits tumour growth and metastasis, including to the brain, and prolongs survival, particularly when used as a neoadjuvant therapy.

Conclusions

The TBCP-1 model recapitulates the spontaneous spread of HER2-positive breast cancer to the brain seen in patients and provides a unique tool to identify novel therapeutics and biomarkers. Neratinib-induced ferroptosis provides new opportunities for therapeutic intervention. Further evaluation of neratinib neoadjuvant therapy is warranted.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1177-1) contains supplementary material, which is available to authorized users.

Remodeling the Microenvironment before Occurrence and Metastasis of Cancer

Tumorigenesis and progression of cancer are complex processes which transformed cells and stromal cells interact and co-evolve. Intrinsic and extrinsic factors cause the mutations of cells. The survival of transformed cells critically depends on the circumstances which they reside. The malignant transformed cancer cells reprogram the microenvironment locally and systemically. The formation of premetastatic niche in the secondary organs facilitates cancer cells survival in the distant organs. This review outlines the current understanding of the key roles of premalignant niche and premetastatic niche in cancer progression. We proposed that a niche facilitates survival of transformed cells is characteristics of senescence, stromal fibrosis and obese microenvironment. We also proposed the formation of premetastatic niche in secondary organs is critically influenced by primary cancer cells. Therefore, it suggested that strategies to target the niche can be promising approach to eradicate cancer cells.