Brain metastasis represents an ongoing clinical challenge with high morbidity and mortality despite improvements in other areas of oncology. A significant obstacle in brain metastasis research concerns the modelling of the complex tumour-brain microenvironment and there has been a recent shift to the development of more complex assays to improve translational potential. Organoids are three-dimensional tissue aggregates derived from tumour tissue or stem cells and have been utilised extensively in wider biological research. This review aims to summarise the current state of brain metastasis organoid research, with a focus on methodologies, mechanistic understanding, and clinical applicability. A narrative review of the literature was performed using MEDLINE, EMBASE, Scopus, PubMed, ScienceDirect and Web of Science and results were screened using PRISMA guidelines. Search strategies included variations of 'brain metastasis' and 'cerebral organoid' and fifteen articles were included for review. There was a clear lack of uniformity in the methodologies used in organoid production, with additionally fragmented approaches in the investigation of molecular mechanisms and drug discovery. Comparison is thus highly challenging, and this is exacerbated by small sample sizes and diverse primary tumour types. Additionally, there remains an over-reliance on the use of animal-based tissues rather than those derived from human patients. Interestingly, several studies introduced blood-brain-barrier models which show potential however remain in early stages of development. Future studies should aim to streamline organoid production techniques and establish a consensus on relevant molecular pathways of interest, while increasing cohort sizes to enhance clinical applicability. Although it remains in nascent stages, cerebral organoid research represents a field with strong potential to improve knowledge and treatment options for people living with brain metastases.

Activated Akt and loss of phosphatase and tensin homolog (PTEN) tumour suppression aid chemo- and radio-resistance in glioblastoma stem cells (GSC), contributing to treatment failure in glioblastoma. In this study, sixteen GSC lines were generated from 66 individual glioma samples, in gliomasphere culture conditions. Thirteen of 16 GSC lines expressed hyperphosphorylated Akt (Ser473); Akt phosphorylation did not correlated with EGFR expression. An LDH colorimetric assay was used to measure the in vitro cytotoxicity of eight of these lines. Akt X (20 µM) proved more effective at inducing in vitro GSC cytotoxicity (range: 22-73%) over 48 hours than triciribine (20 µM) (0-27%), although both agents inhibited Akt phosphorylation as detected by western blot analysis. A statistically significant correlation between PTEN loss (western blot) and the extent of Akt X-induced cytotoxicity was found (p = 0.03). Akt inhibition reduces in vitro proliferation of treatment-resistant GSC lines, especially in PTEN-deficient lines, warranting further translational investigation in glioblastoma.

Zymography is a technique for detecting, identifying, and quantifying enzyme activity through gel electrophoresis. Gelatin zymography is used to detect matrix metalloproteinase (MMP) activity (a class of zinc-dependent endopeptidases) such as MMP-2 and MMP-9. We describe a semiquantitative method, optimized for determining the activity of secreted gelatinases in cell culture conditioned medium via the digestion of gelatin embedded in a polyacrylamide gel. This assay can also be partnered with a quantitative "invadopodia degradation" assay, which detects the degradation of FITC-labelled gelatin by actin-rich membrane protrusions known as invadopodia. These projections are enriched in proteolytic enzymes, including MMP-2 and MMP-9 in glioblastoma cells, and are secreted to modify/degrade ECM proteins and facilitate tumor cell invasion.

Gliomas are highly malignant brain tumours that remain refractory to treatment. Treatment is typically surgical intervention followed by concomitant temozolomide and radiotherapy; however patient prognosis remains poor. Voltage gated ion channels have emerged as novel targets in cancer therapy and inhibition of a potassium selective subtype (hERG, Kv11.1) has demonstrated antitumour activity. Unfortunately blockade of hERG has been limited by cardiotoxicity, however hERG channel agonists have produced similar chemotherapeutic benefit without significant side effects. In this study, electrophysiological recordings suggest the presence of hERG channels in the anaplastic astrocytoma cell line SMA-560, and treatment with the hERG channel agonist NS1643, resulted in a significant reduction in the proliferation of SMA-560 cells. In addition, NS1643 treatment also resulted in a reduction of the secretion of matrix metalloproteinase-9 and SMA-560 cell migration. When combined with temozolomide, an additive impact was observed, suggesting that NS1643 may be a suitable adjuvant to temozolomide and limit the invasiveness of glioma.

Background:Circulating tumor DNA has emerging clinical applications in several cancers; however, previous studies have shown low sensitivity in glioma. We investigated if 3 key glioma gene mutations IDH1, TERTp, and EGFRvIII could be reliably detected in plasma by droplet digital polymerase chain reaction (ddPCR) thereby demonstrating the potential of this technique for glioma liquid biopsy.Methods:We analyzed 110 glioma patients from our biobank with a total of 359 plasma samples (median 4 samples per patient). DNA was isolated from plasma and analyzed for IDH1, TERTp, and EGFRvIII mutations using ddPCR.Results:Total cfDNA was significantly associated with tumor grade, tumor volume, and both overall and progression-free survival for all gliomas as well as the grade 4 glioblastoma subgroup, but was not reliably associated with changes in tumor volume/progression during the patients' postoperative time course. IDH1 mutation was detected with 84% overall sensitivity across all plasma samples and 77% in the preoperative samples alone; however, IDH1 mutation plasma levels were not associated with tumor progression or survival. IDH1m plasma levels were not associated with pre- or postsurgery progression or survival. The TERTp C228T mutation was detected in the plasma ctDNA in 88% but the C250T variant in only 49% of samples. The EGFRvIII mutation was detected in plasma in 5 out of 7 patients (71%) with tissue EGFRvIII mutations in tumor tissue.Conclusions:Plasma ctDNA mutations detected with ddPCR provide excellent diagnostic sensitivity for IDH1, TERTp-C228T, and EGFRvIII mutations in glioma patients. Total cfDNA may also assist with prognostic information. Further studies are needed to validate these findings and the clinical role of ctDNA in glioma.

With the application of spatial biology, the detection and identification of the diverse cell types present in the tumor microenvironment, including specific immune subsets, is possible at single cell resolution. Since spatial biology analysis of tumor tissue allows multiple biological parameters to be measured, including cell type, cell number, cell state, as well as the precise location and the spatial relationship of every cell to other cells and histopathological hallmarks, a vast amount of data is generated. The power of this is realized when correlating the spatial biology data with clinical data for each patient, from which the tissue was collected during biopsy or surgery, conducted as part of the patient's diagnosis and treatment. Aside from the enormous leap in chemistry and molecular biology technology required to develop the analytical tools for spatial biology, collection, analysis of cells in the tumor microenvironment has been possible only with the development of computational tools capable of deciphering tumor tissue complexity to predict tumor evolution and response to treatment and the role of immune cells in regulating tumor biology. Here we describe how spatial biology analysis, combined with computational analysis have been used to deconstruct the complexity of the brain tumor microenvironment and shed light on why brain tumors exhibit extreme immunosuppression. We also discuss how the understanding gained using spatial biology has shed light on how tumor immunosuppression can be overcome.

Cancers of the central nervous system (CNS) are unique with respect to their tumor microenvironment. Such a status is due to immune-privilege and the cellular behaviors within a highly networked, neural-rich milieu. During tumor development in the CNS, neural, immune and cancer cells establish complex cell-to-cell communication networks which mimic physiological functions, including paracrine signaling and synapse-like formations. This crosstalk regulates diverse pathological functions contributing to tumor progression. In the CNS, regulation of physiological and pathological functions relies on various cell signaling and transcription programs. At the core of these events lies the cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), a master transcriptional regulator in the CNS. CREB is a kinase inducible transcription factor which regulates many CNS functions, including neurogenesis, neuronal survival, neuronal activation and long-term memory. Here, we discuss how CREB-regulated mechanisms operating in diverse cell types, which control development and function of the CNS, are co-opted in CNS tumors.

Small extracellular vesicles have gained attention in neuroscience due to their role in cell-to-cell communication and their potential diagnostic and therapeutic applications. Despite progress in the field, there remains a gap in our understanding of the composition and function of extracellular vesicles with regards to brain tumours. Previous studies have primarily evaluated extracellular vesicles obtained from patient fluids or cell culture medium, rather than directly from tumour tissue. Here we successfully isolated small extracellular vesicles from surgical tissue biopsies of glioblastomas or meningiomas, marking, marking the first report of in situ extracellular vesicle isolation from brain tumours. The protein content of the tumour tissue and their extracellular vesicles was characterized using tandem mass spectrometric proteomics, revealing proteins exclusively detected or enriched in extracellular vesicles relative to the tumour tissue. While our study confirmed proteins previously identified in glioblastoma and meningioma extracellular vesicles from various sources, it also identified novel proteins and pathways associated with extracellular vesicles from these tumour types. This study underscores the benefit of analysing in situ extracellular vesicles derived directly from brain tissue for insights into tumour biology and highlights the need for further research comparing extracellular vesicles from various types and grades of brain tumours.

Abstract INTRODUCTION Brain metastases pose a significant and growing challenge in clinical practice, yet the molecular variants of this tumor type has not previously been examined comprehensively across multiple cancer types. In particular, there has been limited focus on contrasting the genetic profiles of common brain metastases originating from primary sites like lung, breast, melanoma, colorectal, and renal cancers, with those arising infrequently such as prostate and others. METHODS We have prospectively collected over 125 fresh frozen brain metastases and matching germline reference samples from 14 different primary tumor types and to date have performed WGS, RNA-Seq and Epic 850k methylation profiling on 60 of these samples spanning both common and rare brain metastases. We have employed machine learning algorithms, network analysis techniques, and integrative bioinformatics pipelines to extract meaningful insights into the biological underpinnings of brain metastasis formation. RESULTS We conducted an in-depth investigation into the genomic, transcriptomic, and epigenomic profiles of brain metastases, spanning both common and rare types. By merging these diverse datasets, we identified distinct molecular modifications linked to brain metastases with low incidence rates compared to those more frequently observed. Notably, we observed heightened alterations in the regulation of Golgi dynamics, sensing of lipid species, chromatin remodeling factors, and cytoskeletal remodeling in rare brain metastases. These changes likely influence cell migration and invasion dynamics, elucidating the potential for unique characteristics of less common brain metastasis types. CONCLUSIONS This research indicates that the molecular mechanisms driving the formation of brain metastases may vary depending on whether the primary malignancy frequently or infrequently spreads to the brain. Studies such as these, will aid in eventually driving innovations in precision oncology and ultimately improving patient outcomes.

Glioblastoma (GBM) is the most prevalent primary central nervous system tumour in adults. The lethality of GBM lies in its highly invasive, infiltrative, and neurologically destructive nature resulting in treatment failure, tumour recurrence and death. Even with current standard of care treatment with surgery, radiotherapy and chemotherapy, surviving tumour cells invade throughout the brain. We have previously shown that this invasive phenotype is facilitated by actin-rich, membrane-based structures known as invadopodia. The formation and matrix degrading activity of invadopodia is enhanced in GBM cells that survive treatment. Drug repurposing provides a means of identifying new therapeutic applications for existing drugs without the need for discovery or development and the associated time for clinical implementation. We investigate several FDA-approved agents for their ability to act as both cytotoxic agents in reducing cell viability and as 'anti-invadopodia' agents in GBM cell lines. Based on their cytotoxicity profile, three agents were selected, bortezomib, everolimus and fludarabine, to test their effect on GBM cell invasion. All three drugs reduced radiation/temozolomide-induced invadopodia activity, in addition to reducing GBM cell viability. These drugs demonstrate efficacious properties warranting further investigation with the potential to be implemented as part of the treatment regime for GBM.

Multiple sclerosis (MS) is a neurodegenerative disease marked by chronic neuroinflammation thought to be mediated by the inflammasome pathway. Connexin 43 (Cx43) hemichannels contribute to the activation of the inflammasome through the release of adenosine triphosphate (ATP) inflammasome activation signals. The objective of the study was to evaluate if the Cx43 hemichannel blocker, tonabersat, is effective in modulating the inflammatory response and reducing disability in the myelin oligodendrocyte glycoprotein 35-55-induced experimental autoimmune encephalomyelitis (MOG35-55 EAE) model of MS. Here, we show that the Cx43 hemichannel blocking drug, tonabersat, significantly reduced expression of neuroinflammatory markers for microglial activation (ionized calcium-binding adapter molecule 1 (Iba1)) and astrogliosis (glial fibrillary acidic protein (GFAP)) while preserving myelin basic protein (MBP) expression levels in the corpus callosum, motor cortex, and striatum regions of the brain in MOG35-55 EAE mice. Reduced NOD-like receptor protein 3 (NLRP3) inflammasome complex assembly and Caspase-1 activation confirmed the drug's mode of action. MOG35-55 EAE mice showed clinical signs of MS, but MOG35-55 EAE mice treated with tonabersat retained behavior closer to normal. These data suggest that clinical trial phase IIb-ready tonabersat may merit further investigation as a promising candidate for MS treatment.

A critical challenge in the treatment of glioblastoma (GBM) is its highly invasive nature which promotes cell migration throughout the brain and hinders surgical resection and effective drug delivery. GBM cells demonstrate augmented invasive capabilities following exposure to the current gold standard treatment of radiotherapy (RT) and concomitant and adjuvant temozolomide (TMZ), resulting in rapid disease recurrence. Elucidating the mechanisms employed by post-treatment invasive GBM cells is critical to the development of more effective therapies. In this study, we utilized a Nanostring® Cancer Progression gene expression panel to identify candidate genes that may be involved in enhanced GBM cell invasion after treatment with clinically relevant doses of RT/TMZ. Our findings identified thrombospondin-1 (THBS1) as a pro-invasive gene that is upregulated in these cells. Immunofluorescence staining revealed that THBS1 localised within functional matrix-degrading invadopodia that formed on the surface of GBM cells. Furthermore, overexpression of THBS1 resulted in enhanced GBM cell migration and secretion of MMP-2, which was reduced with silencing of THBS1. The preliminary data demonstrates that THBS1 is associated with invadopodia in GBM cells and is likely involved in the invadopodia-mediated invasive process in GBM cells exposed to RT/TMZ treatment. Therapeutic inhibition of THBS1-mediated invadopodia activity, which facilitates GBM cell invasion, should be further investigated as a treatment for GBM.

Metastatic cancer is responsible for the overwhelming majority of cancer-related deaths, with metastatic tumors being the most common neoplasms affecting the central nervous system. One of the major factors regulating tumor biology is the tumor microenvironment. However, little is known about the cellular and non-cellular composition of metastatic brain tumors and how tumor cell ontogeny influences the metastatic brain tumor microenvironment. By integrating multiplex immunohistochemistry and histopathological analysis to investigate composition and the spatial relationship between neoplastic cells, infiltrating and brain resident immune cells and the extracellular matrix, we demonstrate that metastatic brain tumors exhibit differences in extracellular matrix deposition, compared with the most common primary brain tumor type, glioblastoma, and that the dominant immune cell types in metastatic brain tumors are immunosuppressive macrophages, which preferentially localize to extracellular matrix-rich stromal regions.

PurposeThe therapeutic efficacy of radiotherapy/temozolomide treatment for glioblastoma (GBM) is limited by the augmented invasiveness mediated by invadopodia activity of surviving GBM cells. As yet, however the underlying mechanisms remain poorly understood. Due to their ability to transport oncogenic material between cells, small extracellular vesicles (sEVs) have emerged as key mediators of tumour progression. We hypothesize that the sustained growth and invasion of cancer cells depends on bidirectional sEV-mediated cell-cell communication.MethodsInvadopodia assays and zymography gels were used to examine the invadopodia activity capacity of GBM cells. Differential ultracentrifugation was utilized to isolate sEVs from conditioned medium and proteomic analyses were conducted on both GBM cell lines and their sEVs to determine the cargo present within the sEVs. In addition, the impact of radiotherapy and temozolomide treatment of GBM cells was studied.ResultsWe found that GBM cells form active invadopodia and secrete sEVs containing the matrix metalloproteinase MMP-2. Subsequent proteomic studies revealed the presence of an invadopodia-related protein sEV cargo and that sEVs from highly invadopodia active GBM cells (LN229) increase invadopodia activity in sEV recipient GBM cells. We also found that GBM cells displayed increases in invadopodia activity and sEV secretion post radiation/temozolomide treatment. Together, these data reveal a relationship between invadopodia and sEV composition/secretion/uptake in promoting the invasiveness of GBM cells.ConclusionsOur data indicate that sEVs secreted by GBM cells can facilitate tumour invasion by promoting invadopodia activity in recipient cells, which may be enhanced by treatment with radio-chemotherapy. The transfer of pro-invasive cargos may yield important insights into the functional capacity of sEVs in invadopodia.

Targeted therapies for cancers have improved primary tumor response rates, but concomitantly, brain metastases (BM) have become the most common brain tumors in adults and are associated with a dismal prognosis of generally less than 6 months, irrespective of the primary cancer type. They most commonly occur in patients with primary breast, lung, or melanoma histologies; however, they also appear in patients with other primary cancers including, but not limited to, prostate cancer, colorectal cancer, and renal cell carcinoma. Historically, molecular biomarkers have normally been identified from primary tumor resections. However, clinically informative genomic alterations can occur during BM development and these potentially actionable alterations are not always detected in the primary tumor leading to missed opportunities for effective targeted therapy. The molecular mechanisms that facilitate and drive metastasis to the brain are poorly understood. Identifying the differences between the brain and other extracranial sties of metastasis, and between primary tumors and BM, is essential to improving our understanding of BM development and ultimately patient management and survival. In this review, we present the current data on the genomic landscape of BM from various primary cancers which metastasize to the brain and outline potential mechanisms which may play a role in promoting the formation of the distant metastases in the brain.

Advanced prostate cancers have a poor survival rate and a lack of effective treatment options. In order to broaden the available treatments, immunotherapies have been investigated. These include cancer vaccines, immune checkpoint inhibitors, chimeric antigen receptor T cells and bispecific antibodies. In addition, combinations of different immunotherapies and with standard therapy have been explored. Despite the success of the Sipuleucel-T vaccine in the metastatic, castrate-resistant prostate cancer setting, other immunotherapies have not shown the same efficacy in this population at large. Some individual patients, however, have shown remarkable responsiveness to these therapies. Therefore, work is underway to identify which populations will respond positively to therapy via the identification of predictive biomarkers. These include biomarkers of the immunologically active tumour microenvironment and biomarkers indicative of high neoantigen expression in the tumour. This review examines the constitution of the prostate tumour immune microenvironment, explores the effectiveness of immunotherapies, and finally investigates how therapy selection can be optimised by the use of biomarkers.

Cancer stem cells are defined as low-abundance, quiescent cells and are considered a major cellular source of tumor recurrence following therapy, which identifies these cells as important therapeutic targets for difficult-to-treat cancers, including high-grade gliomas. By contrast to the highly proliferative bulk tumor cells, glioma stem cells (GSC) are slow-cycling, and therefore less sensitive to DNA damaging cytotoxic drugs. GSC are also less reliant on aerobic glycolytic metabolism, leading to inadequate clearing of GSC by chemotherapy and radiotherapy. The definition of GSC is based on the expression of specific stem cell protein markers. This method of GSC isolation is successful in isolating cell populations that can reliably recapitulate the tumor. However, cell populations that lack stem marker expression may also be capable of tumor recapitulation. Therefore, robust, reproducible methods for isolating GSC are required to identify and isolate cells with stem cell characteristics. Here, we provide a comprehensive and reproducible protocol for the isolation of slow-cycling GSC. Using this method, GSC isolated retain key characteristics of the cells in situ, including expression of genes associated with cell quiescence and invasive potential, compared to non-quiescent cell populations. Thus, isolation of GSC gated on cell proliferation offers a reliable alternative method for in vitro GSC identification, that adequately mirrors the physiological properties of GSC seen in vivo.

Purpose Tumor cells thrive by adapting to the signals in their microenvironment. To adapt, cancer cells activate signaling and transcriptional programs and migrate to establish micro-niches, in response to signals from neighboring cells and non-cellular stromal factors. Understanding how the tumor microenvironment evolves during disease progression is crucial to deciphering the mechanisms underlying the functional behavior of cancer cells. Methods Multiplex immunohistochemistry, spatial analysis and histological dyes were used to identify and measure immune cell infiltration, cell signal activation and extracellular matrix deposition in low-grade, high-grade astrocytoma and glioblastoma. Results We show that lower grade astrocytoma tissue is largely devoid of infiltrating immune cells and extracellular matrix proteins, while high-grade astrocytoma exhibits abundant immune cell infiltration, activation, and extensive tissue remodeling. Spatial analysis shows that most T-cells are restricted to perivascular regions, but bone marrow-derived macrophages penetrate deep into neoplastic cell-rich regions. The tumor microenvironment is characterized by heterogeneous PI3K, MAPK and CREB signaling, with specific signaling profiles correlating with distinct pathological hallmarks, including angiogenesis, tumor cell density and regions where neoplastic cells border the extracellular matrix. Our results also show that tissue remodeling is important in regulating the architecture of the tumor microenvironment during tumor progression. Conclusion The tumor microenvironment in malignant astrocytoma, exhibits changes in cell composition, cell signaling activation and extracellular matrix deposition during disease development and that targeting the extracellular matrix, as well as cell signaling activation will be critical to designing personalized therapy.

Glioblastoma is the most aggressive brain tumour with short survival, partly due to resistance to conventional therapy. Glioma stem cells (GSC) are likely to be involved in treatment resistance, by releasing extracellular vesicles (EVs) containing specific molecular cargoes. Here, we studied the EVs secreted by glioma stem cells (GSC-EVs) and their effects on radiation resistance and glioma progression. EVs were isolated from 3 GSCs by serial centrifugation. NanoSight measurement, cryo-electron microscopy and live imaging were used to study the EVs size, morphology and uptake, respectively. The non-GSC glioma cell lines LN229 and U118 were utilised as a recipient cell model. Wound healing assays were performed to detect cell migration. Colony formation, cell viability and invadopodium assays were conducted to detect cell survival of irradiated recipient cells and cell invasion post GSC-EV treatment. NanoString miRNA global profiling was used to select for the GSC-EVs’ specific miRNAs. All three GSC cell lines secreted different amounts of EVs, and all expressed consistent levels of CD9 but different level of Alix, TSG101 and CD81. EVs were taken up by both LN229 and U118 recipient cells. In the presence of GSC-EVs, these recipient cells survived radiation exposure and initiated colony formation. After GSC-EVs exposure, LN229 and U118 cells exhibited an invasive phenotype, as indicated by an increase in cell migration. We also identified 25 highly expressed miRNAs in the GSC-EVs examined, and 8 of these miRNAs can target PTEN. It is likely that GSC-EVs and their specific miRNAs induced the phenotypic changes in the recipient cells due to the activation of the PTEN/Akt pathway. This study demonstrated that GSC-EVs have the potential to induce radiation resistance and modulate the tumour microenvironment to promote glioma progression. Future therapeutic studies should be designed to interfere with these GSC-EVs and their specific miRNAs.

Brain tumor cells thrive by adapting to the signals in their microenvironment. Understanding how the tumor microenvironment evolves during disease progression is crucial to deciphering the mechanisms underlying the functional behavior of cancer cells. To adapt, cancer cells activate signaling and transcriptional programs and migrate to establish micro-niches, in response to signals from neighboring cells and non-cellular stromal factors. Using multiple tissue analysis approaches to identify and measure immune cell infiltration and extracellular matrix deposition in brain tumors, we show that low-grade glioma is largely devoid of infiltrating immune cells and extracellular matrix proteins, while high-grade glioma exhibits abundant immune cell infiltration and activation, as well as extensive collagen deposition. Spatial analysis shows that most T-cells are sequestered in perivascular nests, but macrophages penetrate deep into tumor cell rich regions. High-grade gliomas exhibit heterogeneous PI3K and MAPK signaling, which correlates with distinct pathological hallmarks, including tumor angiogenesis, tumor cell density and extracellular matrix deposition. Our results also provide compelling evidence that tissue remodeling is an important element in glioma progression, and that targeting the extracellular matrix will be critical to improving GBM therapy.