P12.09.B Extracellular vesicle derived-miR-146a increases melanoma brain metastasis progression via Notch signalling pathway dysregulation

Background

Melanoma has the highest tropism of any cancer to metastasize to the brain, and 40% of late-stage patients develop brain metastasis. Invasion, survival, and progression of tumors is dependent on the support of the surrounding microenvironment; therefore, modulation of neighboring cells is a key factor in metastasis. Extracellular vesicles (EVs) are important in cell-to-cell signalling, shuttling proteins, RNA and DNA to alter the surroundings into a favorable tumor microenvironment. Our aims were to investigate the role of melanoma brain metastasis (MBM) derived EVs in MBM development to find possible contributing mechanisms to cancer progression for eventual therapeutic targeting.

Material and Methods

MBM-EVs isolated via sequential ultracentrifugation were injected into mice as a pre-treatment prior to intracardial injection of MBM cells. EVs were co-cultured with normal human astrocytes (NHA) to investigate phenotypic changes. MiRNA sequencing was performed on EVs collected from MBM cells and compared to NHA and melanocytes to determine a candidate miRNA for targeting. In situ hybridization was utilized to evaluate the level of miRNA in clinical patient MBM samples. Functional in vivo validation was performed by injecting miRNA knockout MBM cells into mice. Sequencing of NHA in the presence or absence of target miRNA mimic was used to determine downstream targets.

Results

Mice primed with EVs had a significant increase in MBM tumor burden, compared to non-primed mice. Co-culture with MBM-EVs resulted in NHA activation in vitro, with increased proliferation, invasion, cytokine production, and upregulation of GFAP. MiR-146a was highly upregulated in MBM EVs, and miR-146a mimics activated NHA. Patient samples had a significant increase in miR-146a expression, compared to healthy brain controls. MiR-146a knockdown in MBM mice models reduced MBM burden and prolonged animal survival. Sequencing of NHA determined NUMB, an inhibitor of the Notch signalling pathway, as a target of miR-146a. Numb and other downstream Notch proteins expression was significantly altered in NHA in the presence of both MBM-EVs and miR-146a.

Conclusion

In conclusion, EVs are important regulators of MBM and establish tumor-supporting reactive astrocytes by delivery of miR-146a. MiR-146a alters Notch signalling in astrocytes via inhibition of the tumor suppressor gene NUMB. Elevated miR-146a levels in patients suggests a potential clinical intervention is possible via miR-146a targeting.

P13.16 Metastatic potential of systemic glioblastoma stem cell lines in vivo

BACKGROUND

Despite aggressive tumor behavior, extracranial metastases rarely develop in glioblastoma (GBM) patients. Two potential explanations have been suggested: 1) The blood-brain-barrier functions as a physical barrier that prevents the dissemination of GBM cells out of the central nervous system (CNS) or 2) that extracranial metastasis do occur, but the patients die before extracranial metastases manifest themselves. The first theory has been questioned based on the fact that circulating tumor cells (CTC) were found in blood samples of GBM patients without systemic metastases. To date it has not been proven if CTCs are able to reenter the brain and to what extent they are able to form systemic extracranial metastatic lesions. Therefore, the current study aimed at analyzing the dissemination patterns and the underlying mechanisms associated with the ability of GBM CTCs to form extracranial metastases.

MATERIAL AND METHODS

Five highly characterized human GBM stem cell (GSC) lines (P3, BG5, BG7, GG6, GG16), displaying GBM CNV patterns, were intracranially implanted in a first cohort, then transduced with a lentiviral Firefly Luciferase-eGFP vector and injected into the left cardiac ventricle of NOD/SCID mice in a second cohort. Mice were observed closely and tumor burden was assessed using in vivo as well as ex vivo bioluminescence imaging, MRI and PET. Mice were euthanized when the objective endpoint criteria (tumor burden) was met, then organs were harvested and fixed for further analysis.

RESULTS

First, a detailed characterization of the GSC line invasion patterns were assessed when grown as orthotopic xenografts in vivo dividing them into three categories: 1) Highly invasive without apparent angiogenesis (BG5) 2) Invasive with perivascular infiltration and angiogenesis (P3, BG7 and GG16) and 3) Angiogenic and highly circumscribed (GG6). Following intracardial injection, (7 out of 8) P3 animals developed extracranial and intracranial tumors with a distinctive pattern. Brain, adrenal gland, ovary and liver were amongst the organs most susceptible for tumor growth in the P3 group. For the BG5 and BG7 cell lines, no metastases were observed whereas only 1 animal out of 10 developed metastases in both groups GG16 and GG6.

CONCLUSION

Only one out of 5 GSC lines exhibited a strong metastatic potential when injected into the left cardiac ventricle. Compared to other tumors which exhibit a strong metastatic potential from the circulation, GSC lines do only to a very limited extent show this potential reflecting observations made in the clinic.

P13.08 Novel Thioridazine derivates: Antiproliferative and apoptosis-inducing activity on glioblastoma cells in vitro

BACKGROUND

Although withdrawn from the market due to cardiotoxicity, we have shown that the antipsychotic drug Thioridazine shows chemosensitizing effects in combination with Temozolomide (TMZ) for the treatment of glioblastoma multiforme (GBM). Based on our prior observations, the aim of the presented project was through medicinal chemistry, to design and synthesize new compounds based on Thioridazines tricyclic structure, and to determine their therapeutic potential.

MATERIAL AND METHODS

Fourteen compounds were synthesized where variations were made within the tricyclic side chains. The newly synthesized compounds were screened for therapeutic efficacy with or without TMZ using a WST-1 cell viability assay as well as a real-time imaging system (IncuCyte). Tests were performed on both monolayer cell cultures, as well as on glioma stem cell spheroids (GSC). The therapeutic effects were also studied on human astrocytes (NHA) as well as on rat brain organoids (BO). Annexin V/propidium iodide (PI) double staining followed by flow cytometric analysis was performed after 48 hours of treatment.

RESULTS

Following an extensive screening, we identified two novel compounds (EA01 and EA02) that at concentrations of 4 and 9.5 µM showed a strong cytotoxicity on GBM cell lines (U-87 MG p<0,0001, U251 p<0,0001, LN18 p=0,0004) as well as on glioma stem cells (GSC) (P3 p<0,0001) compared to NHA and BOs respectively. Also, when BOs were confronted with GSC spheres in an invasion assay, a selective cytotoxicity was observed in the GSCs. Mechanistically, we show that both compounds induce apoptosis in the GBM cells. Moreover, intravenous delivery of increasing concentrations of EA01 and EA02 revealed no toxicity in animals at concentrations up to 21 mg/kg.

CONCLUSION

We have developed two new tricyclic therapeutic compounds that show a strong selective cytotoxicity in GBM cells with limited systemic toxicity in animals. Ongoing studies are investigating the therapeutic potential of EA01 and EA02 in orthotopic xenografts in vivo.

P16.08 Inhibition of melanoma brain metastasis by targeting miR-146a

BACKGROUND

Melanoma has the highest propensity of any cancer to metastasize to the brain, with late-stage patients developing brain metastasis (MBM) in 40% of cases. Survival of patients with MBM is around 8 months with current therapies, illustrating the need for new treatments. MBM development is likely caused by molecular interactions between tumor cells and the brain, constituting the brain metastatic niche. miRNAs delivered by exosomes released from the primary tumor cells may play a role in niche establishment, yet the mechanisms are poorly understood. Here, the aim was to identify miRNAs released by exosomes from melanomas, which may be important in niche establishment and MBM progression.

MATERIAL AND METHODS

miRNAs in exosomes collected from human astrocytes, melanocytes, and MBM cell lines were profiled to determine differential expression. Functional in vitro validation was performed by cell growth and migration assays, cytokine arrays, qPCR and Western blots. Functional in vivo studies were performed after miR knockdown in MBM cell lines. An in silico docking study was performed to determine drugs that potentially inhibit transcription of miR-146a to impede MBM development.

RESULTS

miR-146a was the most upregulated miRNA in exosomes from MBM cells and was highly expressed in human and animal MBM samples. miR-146a mimics activated human astrocytes, shown by increased proliferation and migration, elevated expression of GFAP in vitro and in mouse brain tumor samples, and increased cytokine production. In animal studies, knockdown of miR-146 in MBM cells injected intracardially into mice reduced BM burden and increased animal survival. Based on the docking studies, deserpidine was found to be an effective inhibitor of MBM growth in vitro and in vivo.

CONCLUSION

miR-146a may play an important role in MBM development, and deserpidine is a promising candidate for clinical use.

P15.02 Loss of Williams Syndrome Transcription Factor (WSTF) leads to improved temozolomide sensitivity in human glioblastoma cells irrespective of MGMT expression

BACKGROUND

The prognosis for newly diagnosed adult glioblastoma multiforme (GBM) patients is poor even after standard therapy with a median survival of approximately 14–15 months. The DNA repair protein O 6 -methylguanine-DNA methyltransferase (MGMT) efficiently counteracts formation of the most lethal DNA adducts by temozolomide (TMZ) chemotherapy, and is thus associated with poor outcome in GBM patients. Williams Syndrome Transcription Factor (WSTF) has previously been suggested to regulate the DNA damage response pathway (DDR) in both an indirect (through chromatin remodeling together with SMARCA5 in the WICH complex) and direct manner (by phosphorylating H2AX at Tyr142). However, whether WSTF has any role in the development of resistance against chemotherapy through its ability to regulate the DDR in GBMs, is so far not known. In this study, we investigated whether loss of WSTF sensitizes different MGMT-proficient and -deficient GBM cell lines to TMZ treatment.

MATERIAL AND METHODS

We generated WSTF knockout clones from both MGMT-proficient (LN18, T98G) and -deficient GBM cell lines (U-251) using CRISPR/Cas9 gene-editing technology with lentiviral vectors. The PCR-based screening results combined with the T7 endonuclease mismatch assay for bi-allelic monoclonal knockouts were verified via sequencing and immunoblotting to identify candidate knockout clones. For each cell line, three knockout clones were chosen for further investigation. Colony formation assays were performed to determine the survival ability in response to TMZ treatment. Statistical analysis was performed using two-way ANOVA.

RESULTS

WSTF knockout clones showed a significant decrease in colony formation after TMZ-treatment compared to the corresponding WSTF-expressing control groups (non-target single guide RNA) (LN18: Clone 59 vs control: p= 0.0456, T98G: All three studied clones vs control: p <0.0001, U-251: Clone 7/35.1/70.2 vs control: p <0.0001/p= 0.0107/p= 0.0119). Furthermore, two out of three clones of T98G and U-251 (T98G Clone 13 and 128 vs control, p <0.0001, U-251 Clone 7 vs control, p= 0.0062; clone 70.2, p= 0.0052) showed significantly reduced plating efficiency compared to control cells.

CONCLUSION

WSTF is an important factor in both MGMT de- and proficient GBM cell lines for response against TMZ chemotherapy. The loss of WSTF leads to a significantly increased TMZ sensitivity in clinically relevant concentrations for all the studied cell lines. Ongoing studies are investigating the underlying mechanisms and potential alterations in the DDR pathway caused by WSTF loss.

OS06.6A Inhibition of GBM invasion by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor antagonist Perampanel

BACKGROUND

Extensive tumor cell invasion within the brain represents a major problem for effective treatment of glioblastomas (GBMs). The invasive processes can be divided into three types: Collective cell invasion, perivascular infiltration and single-cell invasion into the brain parenchyma. It has recently been shown that GBM cells have the ability to form synapses with neural cells pointing at an extensive communication network between brain cells GBM cells. This communication network can be mediated via the metabolites glutamine and glutamate both needed for GBM cell proliferation. In this context, it has been shown in preclinical models that Perampanel, an antiepileptic agent, functioning as non-competitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor antagonist, has an inhibitory effect on GBM growth. In order to delineate how Perampanel affects GBM invasion, we here utilised a highly characterized 3D GBM-brain organoid invasion model where single-cell invasion was studied in real-time following Perampanel treatment.

MATERIAL AND METHODS

A brain coculture model, consisting of rat brain organoids expressing various markers of the human adult brain, where confronted with GFP-labelled tumor cells. By using time-lapse confocal microscopy, we quantified single-cell invasion patterns and speed of invasion using two glioma stem cell models (GSCs; BG5 and BG7).

RESULTS

Perampanel treatment significantly reduces tumor cell invasion into the brain organoids with the strongest effect seen in the most invasive GBM (BG5). Here, the single-tumor cell invasion ratio was reduced by 72 % compared to the control group (p=0.0033). In contrast, collective cell invasion was reduced by 19 % (p=0.028). Statistical analysis was performed using an unpaired sample t-test.

CONCLUSION

The AMPA glutamate receptor antagonist Perampanel significantly inhibits GBM invasion, suggesting an important role of the glutamate-glutamine cycle between the GBM cells and neurons in the invasion process. Moreover, this communication and exchange of metabolites seems to be more prominent where single GBM cells invade into the brain parenchyma compared to areas where collective invasion take place.

OS6.3 The complex role of lactate dehydrogenases in glioblastoma development

BACKGROUND

Glioblastomas are among the most malignant primary brain tumors. GBMs are highly angiogenic, exhibit invasive growth, and elevated glycolysis. Under glycolytic conditions, glucose from the blood is metabolized in astrocytes into lactate by LDHA, and exported by MCT4 into the extracellular compartment, inducing a concomitant acidification of the microenvironment. LDHB, generally expressed in oligodendrocytes or neurons, metabolizes lactate into pyruvate for generating ATP in mitochondria. LDH expression was reported to be linked to phenotypic modifications in vitro in GBMs but the mechanisms and the precise role in vivo have not yet been investigated.

MATERIAL AND METHODS

We designed LDHA and LDHB Crispr-Cas9 constructs for infecting glioblastoma stem-like cells. Results: In vitro tumor cell invasion was not significantly impaired in sgLDHA glioblastoma cells, even under extreme hypoxic conditions. Tumor development was moderately impacted in terms of invasion or vascular density. We then explored the role of LDHB in these processes. LDHB knock-out cells had decreased invasive properties in vitro but surprisingly tumors were highly hemorrhagic and angiogenic, supporting a role of tumor-derived LDHB in blood vessel development. We furthermore evaluated the consequences of a double LDHA and LDHB knock-out in the glioma cells. Under hypoxic conditions, sgLDHA/B cell invasion was dramatically decreased in comparison to control cells, and apoptosis was also increased. Tumor development was dramatically impaired for LDHA/LDHB knockout tumors.

CONCLUSION

These results indicate the complex role of LDH enzymes in glioblastoma development. It constitutes the basis for further mechanistical studies linking lactate metabolism to brain tumor development and perturbation of the neuro-vascular microenvironment.

OS12.2 Targeting epigenetic pathways in the treatment of recurrent high-grade glioma

BACKGROUND

High grade glioma (HGG) patients develop resistance to standard treatment leading to disease progression and limited life expectancy. Advances in the molecular characterisation of treatment-naïve HGGs based on next-generation sequencing and DNA methylation analyses have led to a better delineation of HGG subtypes and the identification of distinct genomic abnormalities. Furthermore, using large patient cohorts of longitudinal tumor samples, comprehensive genomic profiling studies emerged to investigate therapy-associated evolution of gliomas. All together, those studies point out the need for personalised treatment strategies, where applied drugs will be adapted to the unique patient-specific genetic abnormalities.

MATERIAL AND METHODS

We collected fresh samples of more than 800 brain tumors containing almost 300 glioma specimen with approximately 100 longitudinal samples of initial and recurrent tumors from 43 matched patients. By now, we have successfully established 34 patient-derived orthotopic xenografts (PDOXs) in mice. We performed comprehensive molecular profiling using array comparative genomic hybridisation, DNA methylation analysis and targeted DNA sequencing on patient specimen and their derivatives such as 3D tumor organoids and PDOXs. The custom-design sequencing panel comprises 234 genes that reflect both established genetic identifiers for individual glioma subtype classification and novel genes encoding mainly epigenetic effector genes. Based on patient-derived material we carried out drug response screening on 3D tumor organoids using a compound library matching the majority of genes that were assessed by targeted sequencing.

RESULTS

We succeeded in generating a live biobank of HGG patient-derived xenografts and 3D organoids that neatly recapitulates the mutational spectrum including structural DNA variation and methylation-based subtypes of gliomas. A highlight is the generation of 19 PDOXs of paired initial and relapse HGGs from a total of 9 glioma patients. A detailed analysis of the paired longitudinal samples indicated that PDOX models closely recapitulate the evolutionary trajectory of the parental tumors. Targeted sequencing of longitudinal HGG PDOXs suggests that relapse tumors accumulate somatic mutations in epigenetic effectors compared with the Initial. Differential drug responses between initial and relapse tumors were observed after screening of in vitro 3D tumor organoids.

CONCLUSION

Response assessment of naïve initial gliomas and recurrences provides crucial information on the differential sensitivity between initial and relapsed HGGs and offers novel personalised therapeutic options in the relapse setting. Furthermore, in depth correlation of the profiled somatic molecular landscape with drug response will enable pharmacogenomic predictions of potential inhibitors in the clinical setting.

PL3.4 Intrinsic tumor plasticity in Glioblastoma allows for recreation of stem like-states and efficient tumor cell adaptation to new microenvironments

BACKGROUND

Cellular heterogeneity has been well established within numerous cancer types, including malignant brain tumours. Initially, cancer stem cells (CSC) have been accounted for formation of phenotypic heterogeneity and tumor progression in glioblastoma (GBM). Recent data, however, suggest that CSCs may not represent a stable entity and intrinsic plasticity plays a key role in tumor adaptation to changing microenvironments. The question arises whether CSCs are a defined subpopulation of tumor cells or whether they represent a changing entity that any cancer cell can adopt depending on the environmental conditions.

MATERIAL AND METHODS

Intra-tumoral phenotypic heterogeneity was interrogated at the single cell transcriptomic and proteomic level in GBM patient-derived orthotopic xenografts (PDOXs) and stem-like cultures. Tumor cell subpopulations were further classified based on expression of four stem cell-associated membrane markers (CD133, CD15, A2B5 and CD44). The resulting 16 subpopulations were FACS isolated and functionally analyzed. Mathematical Markov modelling was applied to calculate state transitions between cell states.

RESULTS

GBM patient biopsies, PDOXs and stem-like cell cultures display remarkable stem cell-associated intra-tumoral heterogeneity. Independent of marker expression, all analysed tumor subpopulations carried stem-cell properties and had the capacity to recreate phenotypic heterogeneity. Mathematical modeling revealed a different propensity in reforming the original heterogeneity over time, which was independent of the proliferation index but linked to tumorigenic potential. Although subpopulations varied in their potential to adapt to new environments, all were able to reach a steady state microenvironment-specific equilibrium.

CONCLUSION

Our results suggest that phenotypic heterogeneity in GBM results from intrinsic plasticity allowing tumor cells to effectively adapt to new microenvironments. Cellular states are non-hierarchical, reversible and occur via stochastic state transitions of existing populations, striving towards an equilibrium instructed by the microenvironment. Our data provides evidence that CSCs do not represent a clonal entity defined by distinct functional properties and transcriptomic signatures, but rather a cellular state that is determined by environmental conditions, which has implications for the design of treatment strategies targeting CSC-like states.

OS6.2 Loss of CYP46A1 directs altered cholesterol homeostasis and opens therapeutic opportunities for glioblastoma

BACKGROUND

Dysregulated cholesterol metabolism is a hallmark of many cancers, including glioblastoma (GBM), but its role in disease progression is not well understood. Here, we identified cholesterol 24-hydroxylase (CYP46A1), a brain-specific enzyme responsible for elimination of cholesterol through conversion of cholesterol to 24(S)-hydroxycholesterol (24OHC), as one of the most dramatically dysregulated cholesterol metabolism genes in GBM.

MATERIAL AND METHODS

Molecular and clinical data was obtained from publicly genomic databases. Immunohistochemistry was applied to assess protein levels of CYP46A1 in primary GBM samples. Lentiviral constructs expressing CYP46A1 were transduced into LN229, LN18 and primary GBM GSCs for functional assays carried out in vitro and in vivo in an orthotopic xenograft model. RNA-seq was performed to identify downstream targets of 24OHC.

RESULTS

CYP46A1 was significantly decreased in GBM samples compared to normal brain tissue. Reduced CYP46A1 expression was associated with increasing tumour grade and poor prognosis in GBM patients. Ectopic expression of CYP46A1 suppressed cell proliferation and in vivo tumour growth by increasing 24OHC levels. Treatment of GBM cells with 24OHC suppressed tumour growth through regulation of LXR and SREBP signalling. Efavirenz (EFV), an activator of CYP46A1 with BBB penetration, inhibited GBM growth in vivo.

CONCLUSION

Our findings demonstrate that CYP46A1 is a critical regulator of cellular cholesterol in GBM and that the CYP46A1/24OHC axis is a potential therapeutic target.

P11.52 Reduced expression of proteolipid protein 2 increases ER-stress-induced apoptosis and autophagy in glioblastoma

BACKGROUND

The PLP2 gene encodes for the Proteolipid protein 2 (PLP2) which is an integral ion channel membrane protein of the endoplasmic reticulum. The protein has been shown to be involved in several human cancers, but the importance of PLP2 in gliomas is poorly understood. In the present study, we therefore investigated the role of PLP2 in human glioma development.

MATERIAL AND METHODS

Immunohistochemistry was carried out for paraffin-embedded glioma samples, and changes in protein level were detected by western blot analysis. Small interfering RNA transfections were used for knockdown of specific genes. Cell viability and proliferation was then assessed by CCK-8 assay and EdU assay. Transmission electron microscopy was used to observe the ultrastructure of the cells and flow cytometry for the evaluation of apoptosis. Finally, U87 and U251 cells were treated with lentiviral transduction to obtain stably PLP2-knockdown cell lines, which were used for an in vivo study.

RESULTS

Data from publicly available datasets (Rembrandt, TCGA and CGGA) showed a correlation between up-regulation of PLP2 levels and increased malignancy. This was confirmed by IHC staining of sections from our own clinical glioma samples. Mechanistically, down-regulation of PLP2 in U87 and U251 glioma cell lines decreased the proliferation and increased apoptosis and autophagy, mediated by ER-stress. In PLP2 knockdown U87 and U251 cells, autophagy inhibition by chloroquine (CQ) augmented apoptotic cell death. Finally, orthotopic U87-shPLP2 and U251-shPLP2 intracranial xenograft models revealed that down-regulating of PLP2 inhibited glioma development in vivo.

CONCLUSION

In conclusion, the results indicate that PLP2 expression is related to glioma progression, and could be a potential target for future treatment strategies.

P11.57 A 3D brain organoid coculture system delineates the invasive cell components in glioblastoma

BACKGROUND

Glioblastoma (GBM) cell infiltration into the surrounding normal brain tissue where the blood brain barrier is intact, represents a major problem for clinical management and therapy. There is a vital need to understand the molecular mechanism that drives tumor cell invasion into the surrounding brain. We have previously developed a 3D coculture model where mature brain organoids are confronted with patient-derived glioblastoma stem-like cells (GSCs). In such a coculture system, single cell invasion into the normal brain tissue can be studied in detail. Here, we first describe in detail, by RNA-seq and proteomics, the differentiation of various neural cell lineages into mature brain organoids as well as their cellular organization. By real-time confocal microscopy and imaging analyses we also determine the speed of tumor cell invasion into the brain. Finally, we used this coculture system to delineate in detail the cellular heterogeneity within the invasive compartment and their gene expression.

MATERIAL AND METHODS

Immunohistochemistry and immunofluorescence were used to determine the expression and distribution of mature neurons, astrocytes, oligodendrocytes, and microglia within the brain organoids. Proteomics and RNA-seq were used to determine brain development ex-vivo. To assess the clonal composition of the GBM-invasive compartment, we used cellular (RGB) barcoding technology. By advanced imaging, we tracked in real time the invasion of barcoded cells into the brain organoids. Finally, we isolated invasive cells and non-invasive cells from our coculture system and used single cell sequencing to analyze their gene expression profiles and molecular phenotypes.

RESULTS

Immunohistochemistry and immunofluorescence showed that brain organoids, after 21 days of differentiation, display a highly cellular and structural organization. RNA-seq and proteomics, performed at different time points of organoid differentiation, revealed that the brain organoids develop into mature brain structures after 21 days as verified by a comparative analysis to normal rat brain development in vivo. Imaging analyses showed that multiple clones within the GBMs have the capacity to invade into the brain tissue with an average speed of ~ 20 μm/h. RNA-sec analysis of the invasive compartment revealed a strong up-regulation of genes and pathways associated with anaerobic respiration (glycolysis).

CONCLUSION

We describe a highly standardized brain organoid coculture system that can be used to delineate GBM invasion ex-vivo. We demonstrate that this platform can be used to unravel the mechanisms that drive GBM invasion into the normal brain.

A novel brain metastases model developed in immunodeficient rats closely mimics the growth of metastatic brain tumours in patients

AIMS

brain metastasis is a common cause of mortality in cancer patients, and associated with poor prognosis. Our objective was to develop a clinically relevant animal model by transplanting human biopsy spheroids derived from metastatic lesions into brains of immunodeficient rats.

METHODS

nine different patient brain metastases from four different primary cancers were implanted into brains of immunodeficient rats. The xenografts were compared with patient tumours by magnetic resonance imaging, histochemistry, immunohistochemistry and DNA copy number analysis.

RESULTS

after transplantation, tumour growth was achieved in seven out of nine human brain metastases. Spheroids derived from four of the metastases initiated in the rat brains were further serially transplanted into new animals and a 100% tumour take was observed during second passage. Three of the biopsies were implanted subcutaneously, where no tumour take was observed. The animal brain metastases exhibited similar radiological features as observed clinically. Histological comparisons between the primary tumours from the patients, the patient brain metastases and the derived xenografts showed striking similarities in histology and growth patterns. Also, immunohistochemistry showed a strong marker expression similarity between the patient tumours and the corresponding xenografts. DNA copy number analysis between the brain metastases, and the corresponding xenografts revealed strong similarities in gains and losses of chromosomal content.

CONCLUSION

we have developed a representative in vivo model for studying the growth of human metastatic brain cancers. The model described represents an important tool to assess responses to new treatment modalities and for studying mechanisms behind metastatic growth in the central nervous system.