Cultivating Ex Vivo Patient-Derived Glioma Organoids Using a Tissue Chopper

Glioblastoma, IDH-wild type, CNS WHO grade 4 (GBM) is a primary brain tumor associated with poor patient survival despite aggressive treatment. Developing realistic ex vivo models remain challenging. Patient-derived 3-dimensional organoid (PDO) models offer innovative platforms that capture the phenotypic and molecular heterogeneity of GBM, while preserving key characteristics of the original tumors. However, manual dissection for PDO generation is time-consuming, expensive and can result in a number of irregular and unevenly sized PDOs. This study presents an innovative method for PDO production using an automated tissue chopper. Tumor samples from four GBM and one astrocytoma, IDH-mutant, CNS WHO grade 2 patients were processed manually as well as using the tissue chopper. In the manual approach, the tumor material was dissected using scalpels under microscopic control, while the tissue chopper was employed at three different angles. Following culture on an orbital shaker at 37 °C, morphological changes were evaluated using bright field microscopy, while proliferation (Ki67) and apoptosis (CC3) were assessed by immunofluorescence after 6 weeks. The tissue chopper method reduced almost 70% of the manufacturing time and resulted in a significantly higher PDOs mean count compared to the manually processed tissue from the second week onwards (week 2: 801 vs. 601, P = 0.018; week 3: 1105 vs. 771, P = 0.032; and week 4:1195 vs. 784, P < 0.01). Quality assessment revealed similar rates of tumor-cell apoptosis and proliferation for both manufacturing methods. Therefore, the automated tissue chopper method offers a more efficient approach in terms of time and PDO yield. This method holds promise for drug- or immunotherapy-screening of GBM patients.

BRMS1 in Gliomas-An Expression Analysis

The metastatic suppressor BRMS1 interacts with critical steps of the metastatic cascade in many cancer entities. As gliomas rarely metastasize, BRMS1 has mainly been neglected in glioma research. However, its interaction partners, such as NFκB, VEGF, or MMPs, are old acquaintances in neurooncology. The steps regulated by BRMS1, such as invasion, migration, and apoptosis, are commonly dysregulated in gliomas. Therefore, BRMS1 shows potential as a regulator of glioma behavior. By bioinformatic analysis, in addition to our cohort of 118 specimens, we determined BRMS1 mRNA and protein expression as well as its correlation with the clinical course in astrocytomas IDH mutant, CNS WHO grade 2/3, and glioblastoma IDH wild-type, CNS WHO grade 4. Interestingly, we found BRMS1 protein expression to be significantly decreased in the aforementioned gliomas, while BRMS1 mRNA appeared to be overexpressed throughout. This dysregulation was independent of patients' characteristics or survival. The protein and mRNA expression differences cannot be finally explained at this stage. However, they suggest a post-transcriptional dysregulation that has been previously described in other cancer entities. Our analyses present the first data on BRMS1 expression in gliomas that can provide a starting point for further investigations.

Abstract 4573: Evaluation of tumor treating fields (TTFields) effects at 200 kHz on a glioblastoma, an anaplastic ependymoma and an oligodendroglioma sample in a patient-derived ex vivo organoid model

TTFields are alternating electric fields of low intensity (1-3 V/cm) and intermediate frequency (100-500 kHz), which are effective and approved for the treatment of glioblastoma (GBM) using 200 kHz frequency. However, there is a lack of ex vivo models to evaluate effects on patients’ tumor biology or to screen patients for treatment efficacy. Therefore, we adapted patient-derived three-dimensional GBM tissue culture models to be compatible with TTFields application and recently published the feasibility of such an approach (Nickl, et al., 2022, doi: 10.3390/cancers14215177). Here, we applied one of those models, i.e. tumor-organoids cultured as microtumors on murine organotypic hippocampal slice cultures (OHSCs), to additional brain tumor entities, namely a sample of an anaplastic ependymoma (AE) patient and an oligodendroglioma patient. Organoids were generated from fresh intra-operatively obtained tumor tissue and cultured for 2 weeks. OHSCs were prepared by slicing the brains of mice 5-8 days postpartum to sections with a thickness of 350 µm using a vibratome, and culturing them for 2 weeks as well. Subsequently, organoids were placed onto the OHSCs. The inovitro™ laboratory research system was used for TTFields administration at 200 kHz and 1.5 V/cm for 72 h. Microtumor growth was evaluated on fluorescence images. Viable organoids formed from the GBM, AE and oligodendroglioma sample and grew to microtumors when placed onto OHSCs. Application of TTFields at 200 kHz led to a significant decrease of microtumor size of the GBM and AE (both p&lt;0.0001), but not the oligodendroglioma sample. This proof-of-principle investigation proved that the application of patient-derived organoids cultured on OHSCs is feasible to investigate the effects of TTFields on different kinds of brain tumors. To our knowledge, this is the first evaluation of TTFields efficacy on patient derived AE and oligodendroglioma tissue cultures. While TTFields at 200 kHz led to a decrease in the microtumor size of the AE sample, the non-responsiveness of the oligodendroglioma sample may be due to different inter-patient sensitivity to TTFields or a suboptimal TTFields frequency.

Citation Format: Vera Nickl, Ellina Schulz, Ellaine Salvador, Laureen Trautmann, Leopold Diener, Almuth F. Kessler, Camelia M. Monoranu, Ralf-Ingo Ernestus, Mario Löhr, Carsten Hagemann. Evaluation of tumor treating fields (TTFields) effects at 200 kHz on a glioblastoma, an anaplastic ependymoma and an oligodendroglioma sample in a patient-derived ex vivo organoid model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4573.

Glioblastoma-Derived Three-Dimensional Ex Vivo Models to Evaluate Effects and Efficacy of Tumor Treating Fields (TTFields)

Glioblastoma (GBM) displays a wide range of inter- and intra-tumoral heterogeneity contributing to therapeutic resistance and relapse. Although Tumor Treating Fields (TTFields) are effective for the treatment of GBM, there is a lack of ex vivo models to evaluate effects on patients' tumor biology or to screen patients for treatment efficacy. Thus, we adapted patient-derived three-dimensional tissue culture models to be compatible with TTFields application to tissue culture. Patient-derived primary cells (PDPC) were seeded onto murine organotypic hippocampal slice cultures (OHSC), and microtumor development with and without TTFields at 200 kHz was observed. In addition, organoids were generated from acute material cultured on OHSC and treated with TTFields. Lastly, the effect of TTFields on expression of the Ki67 proliferation marker was evaluated on cultured GBM slices. Microtumors exhibited increased sensitivity towards TTFields compared to monolayer cell cultures. TTFields affected tumor growth and viability, as the size of microtumors and the percentage of Ki67-positive cells decreased after treatment. Nevertheless, variability in the extent of the response was preserved between different patient samples. Therefore, these pre-clinical GBM models could provide snapshots of the tumor to simulate patient treatment response and to investigate molecular mechanisms of response and resistance.

Tumor Treating Fields (TTFields) Reversibly Permeabilize the Blood-Brain Barrier In Vitro and In Vivo

Despite the availability of numerous therapeutic substances that could potentially target CNS disorders, an inability of these agents to cross the restrictive blood-brain barrier (BBB) limits their clinical utility. Novel strategies to overcome the BBB are therefore needed to improve drug delivery. We report, for the first time, how Tumor Treating Fields (TTFields), approved for glioblastoma (GBM), affect the BBB's integrity and permeability. Here, we treated murine microvascular cerebellar endothelial cells (cerebEND) with 100-300 kHz TTFields for up to 72 h and analyzed the expression of barrier proteins by immunofluorescence staining and Western blot. In vivo, compounds normally unable to cross the BBB were traced in healthy rat brain following TTFields administration at 100 kHz. The effects were analyzed via MRI and immunohistochemical staining of tight-junction proteins. Furthermore, GBM tumor-bearing rats were treated with paclitaxel (PTX), a chemotherapeutic normally restricted by the BBB combined with TTFields at 100 kHz. The tumor volume was reduced with TTFields plus PTX, relative to either treatment alone. In vitro, we demonstrate that TTFields transiently disrupted BBB function at 100 kHz through a Rho kinase-mediated tight junction claudin-5 phosphorylation pathway. Altogether, if translated into clinical use, TTFields could represent a novel CNS drug delivery strategy.

P10.01.A Reversible blood-brain barrier (BBB) disruption by Tumor Treating Fields (TTFields) in a human 3Din vitro model

Background

Drug delivery to the central nervous system (CNS) is often impeded by the restrictive nature of the blood brain barrier (BBB). Since many therapeutic molecules are not able to traverse this barrier, the development of new methods to disrupt the BBB is of paramount importance. Tumor Treating Fields (TTFields) are alternating electric fields of low intensity (1-3 V/cm) and intermediate frequency (100-300 kHz), which are approved and effective for the treatment of glioblastoma at a frequency of 200 kHz. We recently demonstrated that TTFields at lower frequencies are able to transiently induce BBB permeability in in vitro and in vivo murine models. Here, we explored whether the transient opening of the BBB by TTFields in our murine systems also translates to a human cell-based 3D model.

Material and Methods

A three-dimensional BBB model was established by co-culturing primary human brain microvascular endothelial cells (HBMVEC) on a transwell insert together with human pericytes on the bottom of a well-plate. The model was treated with TTFields at 100-300 kHz for 2496 h using the inovitro™ TTFields Lab Bench System (Novocure®). Afterwards, the cells recovered for 24-96 h. In order to analyze the effects of TTFields on barrier integrity and compromise, transendothelial electrical resistance (TEER) of the HBMVEC monolayer was measured before the start of TTFields treatment, immediately after TTFields cessation, as well as 24-96 h after TTFields treatment. Permeability of the barrier was assessed by visualizing the movement of FITC-dextran through the HBMVEC monolayer. In addition, changes in expression and localization of the tight junction protein (TJP) claudin-5 (Cl-5) after application of TTFields were analyzed by fractionated Western-blotting and immunofluorescence (IF) staining, respectively.

Results

Application of TTFields at all investigated frequencies significantly decreased TEER across the HBMVEC monolayer after as early as 24 h, with the strongest effects seen after 72 h at a TTFields frequency of 100 kHz. TTFields treatment delocalized TJP Cl5 from the cell boundaries to the cytoplasm as evidenced by Western-blots and IF stainings. Restoration of the cell barrier was already measurable as early as 24 h after TTFields cessation and a complete recovery was evident after 48 h.

Conclusion

These results in a human 3D in vitro model confirm our previous observations from mouse models that TTFields could transiently open the BBB. These fundamental pre-clinical data demonstrate the feasibility of facilitating drug delivery to the CNS via concomitant application of TTFields. This method opens up the prospect of improved drug-based treatment of devastating CNS diseases such as GBM if these results could be translated to the clinical setting in the future.

Abstract 387: Blood brain barrier (BBB) disruption by tumor treating fields (TTFields) in a human 3D in vitro model

The clinical translatability of novel drug delivery systems begins with basic scientific breakthroughs. Our recent discovery of the ability of Tumor Treating Fields (TTFields) to potentially and transiently disrupt the blood brain barrier (BBB) using our murine in vitro and in vivo models, led us to validate our findings in a human 3D in vitro model established in our lab. The model consists of primary brain microvascular endothelial cells co-cultured with immortalized perciytes in a transwell system. TTFields are alternating electric fields of low intensity (1-3V/cm) and intermediate frequency (100-300kHz), which are effective and approved for the treatment of glioblastoma (GBM) using 200kHz frequency. Our murine data point out that TTFields could disrupt the BBB optimally at 100kHz. To investigate if TTFields exhibit similar effects in the human cell-based in vitro model, it was subjected to TTFields at various frequencies for 24-96h. Cells were afterwards made to recover for 24-96h. To assess BBB integrity and compromise, transendothelial electrical resistance (TEER) was measured before start of TTFields, immediately after end of TTFields, as well as 24-96h after TTFields. In addition, a permeability assay was performed. Finally, immunofluorescence (IF) staining visualized the effects of TTFields on tight junction protein claudin-5 localization. TTFields application of all investigated frequencies significantly decreased TEER. However, the strongest effects were observed with 100kHz after 72h. IF staining revealed delocalization of claudin-5 from the cell boundaries to the cytoplasm. Restoration of cell integrity was already evident as early as 24h, with complete recovery after 48h. Results using our human 3D in vitro model validated our previous observations from murine in vitro and in vivo models that TTFields could transiently disrupt the BBB. These findings provide fundamental pre-clinical data for translation from bench to bedside. Accordingly, TTFields demonstrate to be a promising novel approach in opening the BBB to facilitate drug delivery for improved treatment of central nervous system diseases including devastating brain tumors such as GBM.

Citation Format: Ellaine Salvador, Almuth F. Kessler, Theresa Köppl, Sebastian Schönhärl, Malgorzata Burek, Catherine Tempel Brami, Tali Voloshin, Moshe Giladi, Ralf-Ingo Ernestus, Mario Löhr, Carola Y. Förster, Carsten Hagemann. Blood brain barrier (BBB) disruption by tumor treating fields (TTFields) in a human 3D in vitro model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 387.

Case Report: A Case Series Using Natural Anatomical Gaps-Posterior Cervical Approach to Skull Base and Upper Craniocervical Meningiomas Without Bone Removal

Background: Removal of anteriorly located tumors of the upper cervical spine and craniovertebral junction (CVJ) is a particular surgical challenge. Extensive approaches are associated with pain, restricted mobility of neck and head and, in case of foramen magnum and clivus tumors, with retraction of brainstem and cerebellum.

Methods: Four symptomatic patients underwent resection of anteriorly located upper cervical and lower clivus meningiomas without laminotomy or craniotomy using a minimally invasive posterior approach. Distances of natural gaps between C0/C1, C1/C2, and C2/C3 were measured using preoperative CT scans and intraoperative lateral x-rays.

Results: In all patients, safe and complete resection was conducted by the opening of the dura between C0/C1, C1/C2, and C2/C3, respectively. There were no surgical complications. Local pain was reported as very moderate by all patients and postoperative recovery was extremely fast. All tumors had a rather soft consistency, allowing mass reduction prior to removal of the tumor capsule and were well separable from lower cranial nerves and vascular structures.

Conclusion: If tumor consistency is appropriate for careful mass reduction before removal of the tumor capsule and if tumor margins are not firmly attached to crucial structures, then upper cervical, foramen magnum, and lower clivus meningiomas can be safely and completely removed through natural gaps in the CVJ region. Both prerequisites usually become clear early during surgery. Thus, this tumor entity may be planned using this minimally invasive approach and may be extended if tumor consistency turns out to be less unfavorable for resection or if crucial structures cannot be easily separated from the tumor.

Abstract 279: Transient opening of the blood brain barrier by Tumor Treating Fields (TTFields)

Introduction Alternating electric fields of intermediate frequency and low intensity, known as Tumor Treating Fields (TTFields), are an effective and clinically approved approach for treatment of glioblastoma (GBM). The optimal frequency for treatment of glioma cells based on the cytotoxic response is at 200 kHz. Combination of TTFields with chemotherapy appears to be synergistic with further increase in overall survival of patients with GBM, beyond that with chemotherapy alone. The blood brain barrier (BBB) limits delivery of a majority of drugs to the brain thus limiting treatment options for GBM patients. Recent in vitro studies suggest that TTFields applied at 100 kHz can disturb the BBB. In this study, we investigated the potential use of TTFields to transiently disturb the BBB in animal models.

Methods BBB permeation was tested in healthy rats subsequently to 100 kHz TTFields or sham (heat) application to the rat head. BBB permeability was analyzed by several staining agents: (1) Evans Blue (EB) that was quantified at 610 nm in brain homogenates; (2) 4 kDa TRITC-dextran (TD) that was quantified based on fluorescence intensity in brain cryosections; and (3) the MRI contrast agent Gd-DTPA. Accumulation and clearance of Gd-DTPA were tracked by serial dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). In addition, brain sections were stained for claudin-5, occludin, PECAM-1 and immunoglobulin G (IgG). BBB permeation induced by TTFields was further evaluated in rats orthotopically bearing F98 glioma cells and treated with TTFields at 100 kHz in combination with the chemotherapeutic drug paclitaxel (PTX) for a duration of 72 h. Tumor cell proliferation was assessed by Ki67 staining and the tumor volume was measured by T2 weighted MRI.

Results BBB permeation of EB and TD staining agents was observed in the brains of healthy rats after TTFields application. Moreover, brain cryosections displayed delocalization of claudin-5 and occludin, but not of PECAM-1. Accumulation of IgG in the brain parenchyma was also noted. Confirming these observations, DCE-MRI post-TTFields treatment showed accumulation of Gd in the brain. Return to normal BBB integrity was detected 96 h after TTFields treatment cessation, indicating the effect was transient and reversible. In GBM-induced rats, the combination of PTX (a drug which normally does not cross the BBB) with TTFields significantly decreased tumor cell proliferation and tumor volume compared to animals treated with TTFields alone, sham alone, or sham combined with PTX.

Conclusions Administration of 100 kHz TTFields to the brain of rats led to transient alterations in BBB integrity and permeability, allowing increased uptake of combination chemotherapy. These data indicate that TTFields treatment may be a feasible, novel clinical strategy for transient opening of the BBB to allow for enhanced and more effective delivery of permeable and non-permeable anticancer drugs to the brain.

Citation Format: Catherine Tempel Brami, Ellaine Salvador, Almuth F. Kessler, Malgorzata Burek, Tali Voloshin, Moshe Giladi, Ralf-Ingo Ernestus, Mario Löhr, Carola Förster, Carsten Hagemann. Transient opening of the blood brain barrier by Tumor Treating Fields (TTFields) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 279.

Abstract 6251: Blood brain barrier opening by TTFields: a future CNS drug delivery strategy

Introduction: Although a number of effective drugs are available to treat central nervous system (CNS) disorders, their ability to breach the tight regulation of the blood brain barrier (BBB) still remains a major challenge. Recently, the use of tumor treating fields (TTFields) has become an effective treatment approach for glioblastoma. Furthermore, its combination with chemotherapy significantly improved overall patient survival. Nonetheless, how TTFields could affect the BBB has not yet been studied. Our recent findings exhibit the potential of TTFields administration to open up the BBB in vitro with an optimal frequency of 100 kHz. Consequently, in this study, we therefore aimed to validate our data in vivo.

Experimental procedures: Subsequent to 100 kHz TTFields or heat treatment for 72 h, rats were i.v. injected with Evan´s Blue (EB). Next, they were sacrificed to extract and quantify EB from the brain. In the same manner, rats were injected with TRITC-dextran (TD), after which permeation was visualized in sectioned brains. Cryosections of rat brains were also prepared post-TTFields treatment. These were stained for intercellular junction proteins claudin-5, occludin and PECAM-1 as well as immunoglobulin G (IgG) to assess vessel structure. Finally, serial dynamic contrast-enhanced (DCE) MRI with gadolinium (Gd) contrast agent was performed before and after TTFields administration.

Results: Permeation of both EB and TD was observed in the brain after TTFields application. Moreover, brain cryosections displayed claudin-5 and occludin delocalization but not PECAM-1. Accumulation of IgG in the brain parenchyma was also noted. Confirming these observations, increased Gd in the brain was shown by DCE-MRI post TTFields treatment. A reversion to normal conditions was, however, detected 96 h after end of treatment demonstrated by no difference in contrast enhancement between control and TTFields-treated rats.

Conclusions: Administration of 100 kHz TTFields in rats led to alterations in BBB integrity and permeability, which signal its opening. The subsequent recovery of the BBB at the end of treatment demonstrates transient effects, hence presenting TTFields as a possible novel clinical strategy to open the BBB for enhanced and more effective drug delivery strategy for CNS disorders.

Citation Format: Ellaine Salvador, Almuth F. Kessler, Julia Hörmann, Malgorzata Burek, Catherine T. Brami, Tali V. Sela, Moshe Giladi, Ralf-Ingo Ernestus, Mario Löhr, Carola Förster, Carsten Hagemann. Blood brain barrier opening by TTFields: a future CNS drug delivery strategy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6251.

Prognostic Value of O-(2-[18F]Fluoroethyl)-L-Tyrosine PET/CT in Newly Diagnosed WHO 2016 Grade II and III Glioma

PURPOSE

The use of [¹⁸F]fluoroethyl)-L-tyrosine ([¹⁸F]FET) positron emission tomography/computed tomography (PET/CT) has proven valuable in brain tumor management. This study aimed to investigate the prognostic value of radiotracer uptake in newly diagnosed grade II or III gliomas according to the current 2016 World Health Organization (WHO) classification.

PROCEDURES

A total of 35 treatment-naive patients (mean age, 48 ± 17 years) with histologically proven WHO grade II or III gliomas as defined by the current 2016 WHO classification were included. Static PET/CT imaging was performed 20 min after intravenous [¹⁸F]FET injection. Images were assessed visually and semi-quantitatively using regions of interest for both tumor (SUVmax, SUVmean) and background (BKGmean) to calculate tumor-to-background (TBR) ratios. The association among histological results, molecular markers (including isocitrate dehydrogenase enzyme and methylguanine-DNA methyltransferase status), clinical features (age), and PET findings was tested and compared with outcome (progression-free [PFS] and overall survival [OS]).

RESULTS

Fourteen patients presented with grade II (diffuse astrocytoma n = 10, oligodendroglioma n = 4) and 21 patients with grade III glioma (anaplastic astrocytoma n = 15, anaplastic oligodendroglioma n = 6). Twenty-seven out of the 35 patients were PET-positive (grade II n = 8/14, grade III n = 19/21), with grade III tumors exhibiting significantly higher amino acid uptake (TBR_mean and TBR_max; p = 0.03 and p = 0.02, respectively). PET-negative lesions demonstrated significantly prolonged PFS (p = 0.003) as compared to PET-positive gliomas. PET-positive disease had a complementary value in prognostication in addition to patient age, glioma grade, and molecular markers.

CONCLUSIONS

Amino acid uptake as assessed by [¹⁸F]FET-PET/CT imaging is useful as non-invasive read-out for tumor biology and prognosis in newly diagnosed, treatment-naive gliomas according to the 2016 WHO classification.

Ribosomal Protein S27/Metallopanstimulin-1 (RPS27) in Glioma-A New Disease Biomarker?

Despite its significant overexpression in several malignant neoplasms, the expression of RPS27 in the central nervous system (CNS) is widely unknown. We identified the cell types expressing RPS27 in the CNS under normal and disease conditions. We acquired specimens of healthy brain (NB), adult pilocytic astrocytoma (PA) World Health Organization (WHO) grade I, anaplastic PA WHO grade III, gliomas WHO grade II/III with or without isocitrate dehydrogenase (IDH) mutation, and glioblastoma multiforme (GBM). RPS27 protein expression was examined by immunohistochemistry and double-fluorescence staining and its mRNA expression quantified by RT-PCR. Patients’ clinical and tumor characteristics were collected retrospectively. RPS27 protein was specifically expressed in tumor cells and neurons, but not in healthy astrocytes. In tumor tissue, most macrophages were positive, while this was rarely the case in inflamed tissue. Compared to NB, RPS27 mRNA was in mean 6.2- and 8.8-fold enhanced in gliomas WHO grade II/III with (p < 0.01) and without IDH mutation (p = 0.01), respectively. GBM displayed a 4.6-fold increased mean expression (p = 0.02). Although RPS27 expression levels did not affect the patients’ survival, their association with tumor cells and tumor-associated macrophages provides a rationale for a future investigation of a potential function during gliomagenesis and tumor immune response.

ADAM9: A novel player in vestibular schwannoma pathogenesis

A disintegrin and metalloproteinase 9 (ADAM9) is a member of the transmembrane ADAM family. It is expressed in different types of solid cancer and promotes tumor invasiveness. To the best of our knowledge, the present study was the first to examine ADAM9 expression in vestibular schwannomas (VS) from patients with and without neurofibromatosis type 2 (NF2) and to associate the data with clinical parameters of the patients. The aim of the present study was to evaluate if ADAM9 could be used as prognostic marker or therapeutic target. ADAM9 mRNA and protein levels were measured in VS samples (n=60). A total of 30 of them were from patients with neurofibromatosis. Healthy peripheral nerves from autopsies (n=10) served as controls. ADAM9 mRNA levels were measured by PCR, and protein levels were determined by immunohistochemistry (IHC) and western blotting (WB). The Hannover Classification was used to categorize tumor extension and hearing loss. ADAM9 mRNA levels were 8.8-fold higher in VS compared with in controls. The levels were 5.6-fold higher in patients with NF2 and 12-fold higher in patients with sporadic VS. WB revealed two mature isoforms of the protein, and according to IHC ADAM9 was mainly expressed by S100-positive Schwann cells. There was a strong correlation between ADAM9 mRNA expression and the level of functional impairment (r~1, p=0.01). Particularly, the secreted isoform of ADAM9 was expressed in patients with higher hearing impairment. ADAM9 mRNA was overexpressed in the tumor samples relative to healthy vestibular nerves, and there was an association between higher ADAM9 expression levels and greater hearing impairment. Therefore, ADAM9 may be a prognostic marker for VS, and ADAM9 inhibition might have the potential as a systemic approach for the treatment of VS.

Changes of O6-Methylguanine DNA Methyltransferase (MGMT) Promoter Methylation in Glioblastoma Relapse-A Meta-Analysis Type Literature Review

Methylation of the O⁶-methylguanine DNA methyltransferase (MGMT) promoter has emerged as strong prognostic factor in the therapy of glioblastoma multiforme. It is associated with an improved response to chemotherapy with temozolomide and longer overall survival. MGMT promoter methylation has implications for the clinical course of patients. In recent years, there have been observations of patients changing their MGMT promoter methylation from primary tumor to relapse. Still, data on this topic are scarce. Studies often consist of only few patients and provide rather contrasting results, making it hard to draw a clear conclusion on clinical implications. Here, we summarize the previous publications on this topic, add new cases of changing MGMT status in relapse and finally combine all reports of more than ten patients in a statistical analysis based on the Wilson score interval. MGMT promoter methylation changes are seen in 115 of 476 analyzed patients (24%; CI: 0.21–0.28). We discuss potential reasons like technical issues, intratumoral heterogeneity and selective pressure of therapy. The clinical implications are still ambiguous and do not yet support a change in clinical practice. However, retesting MGMT methylation might be useful for future treatment decisions and we encourage clinical studies to address this topic.

ACTR-19. REPORT ON THE COMBINATION OF AXITINIB AND TUMOR TREATING FIELDS (TTFIELDS) IN THREE PATIENTS WITH RECURRENT GLIOBLASTOMA

OBJECTIVE

Tumor Treating Fields (TTFields) significantly improved survival of newly diagnosed glioblastoma (ndGBM) patients in the EF-14 trial. Axitinib is an orally available tyrosine kinase inhibitor which is approved for the treatment of metastatic renal cell carcinoma. It has a high affinity and specificity for vascular endothelial growth factor receptors. In phase 2 trials, Axitinib improved response rate and PFS in recurrent GBM (rGBM) patients with a manageable toxicity profile. Here, three rGBM patients treated with TTFields and Axitinib (AxiTTFields) are presented.

PATIENT SECTION

A 53-year-old male patient (#1) presented with a progressing GBM after initial surgery, radiochemotherapy followed by 4 cycles of temozolomide (TMZ) and TTFields. In a 46-year-old male patient (#2), early progress occurred after surgery, radiochemotherapy and 3 cycles of TMZ combined with TTFields. In both patients Axitinib was added to the treatment regimen to meet the urgent need of an alternative treatment. In a 61-year-old male patient (#3) with rGBM after surgery, radiochemotherapy and 6 cycles of TMZ, TTFields therapy was initiated at recurrence and the treatment regimen was adapted to AxiTTFields.

RESULTS

No additional adverse events due to the combined therapy of AxiTTFields were observed. Patients #1 and #2 were on AxiTTFields therapy for more than 8 months, presenting an improved neurological status with a partial response in the MRI 3 months after initiating AxiTTFields. #3 declined in his neurological status without any change in the MRI monitoring and died 2.4 months after initiating AxiTTFields. With an average of 77%, the TTFields usage rate was above the independent prognostic threshold of 75%, underlining the feasibility of this approach.

CONCLUSION

AxiTTFields was feasible and safe in three rGBM patients. The addition of Axitinib to TTFields therapy is a promising approach and safety/feasibility will be further investigated in a pilot trial.

EXTH-02. THE BLOOD BRAIN BARRIER (BBB) PERMEABILITY IS ALTERED BY TUMOR TREATING FIELDS (TTFIELDS) IN VIVO

OBJECTIVE

For glioblastoma patients Tumor Treating Fields (TTFields) have been established as adjuvant therapy. The blood brain barrier (BBB) tightly controls the influx of the majority of compounds from blood to brain. Therefore, the BBB may block delivery of drugs for treatment of brain tumors. Here, the influence of TTFields on BBB permeability was assessed in vivo.

METHODS

Rats were treated with 100 kHz TTFields for 72 h and thereupon i.v. injected with Evan’s Blue (EB) which directly binds to Albumin. To evaluate effects on BBB, EB was extracted after brain homogenization and quantified. In addition, cryosections of rat brains were prepared following TTFields application. The sections were stained for tight junction proteins Claudin-5 and Occludin and for immunoglobulin G (IgG) to assess vessel structure. Furthermore, serial dynamic contrast-enhanced DCE-MRI with Gadolinium contrast agent was performed before and after TTFields application.

RESULTS

TTFields application significantly increased the EB accumulation in the rat brain. In TTFields-treated rats, the vessel structure became diffuse compared to control cryosections of rat brains; Claudin 5 and Occludin were delocalized and IgG was found throughout the brain tissue. Serial DCE-MRI demonstrated significantly increased accumulation of Gadolinium in the brain, observed directly after 72 h of TTFields application. The effect of TTFields on the BBB disappeared 96 h after end of treatment and no difference in contrast enhancement between controls and TTFields treated animals was detectable.

CONCLUSION

By altering BBB integrity and permeability, application of TTFields at 100 kHz may have the potential to deliver drugs to the brain, which are unable to cross the BBB. Utilizing TTFields to open the BBB and its subsequent recovery could be a clinical approach of drug delivery for treatment of brain tumors and other diseases of the central nervous system. These results will be further validated in clinical Trials.

Abstract 252: Tumor treating fields (TTFields) affect blood brain barrier (BBB) integrity in vitro and in vivo

Background: The blood-brain barrier (BBB) may impede application of drugs to the brain for treatment of malignant brain tumors, in particular glioblastoma multiforme (GBM). Alternating electric fields with intermediate frequency and low intensity, called Tumor Treating Fields (TTFields), are an established novel adjuvant treatment modality for GBM. Here, the effect of TTFields on BBB permeability is analyzed.

Material and Methods: After TTFields treatment with a frequency of 100-300 kHz for up to 72 h, immortalized murine brain capillary endothelial cells (cerebEND) grown on cover slips and transwell inserts were stained for immunofluorescent assessment of the tight junction proteins Claudin-5 and ZO-1. Transendothelial electrical resistance (TEER) was applied to investigate BBB integrity. Moreover, BBB permeability was determined by fluorescein isothiocyanate (FITC) staining followed by flow cytometry. For in vivo analysis, the increase in vessel permeability was quantified by utilizing i.v. injected Evans Blue (EB) in rats during TTFields application to the brain (100 kHz, 72 h).

Results: The BBB was disturbed by treatment with TTFields as tight junction proteins were delocalized from the cell boundaries to the cytoplasm with maximal effects at 100 kHz. TTFields application significantly reduced the BBB integrity by 65% and significantly increased the BBB permeability for 4 kDa large molecules. Initial recovery of the cell morphology was observed 48 h post-treatment and a complete recovery could be detected after 96 h, indicating a reversibility of the TTFields effect on the BBB. Average accumulation of EB in the rat brain was significantly increased by TTFields application to the rats head.

Conclusion: In the future, TTFields could be utilized to deliver drugs generally unable to cross the BBB to the central nervous system as TTFields at a frequency of 100 kHz are potentially able to disrupt the BBB. The data presented on in vitro and in vivo application of TTFields to permeabilize the BBB may be a rationale for a phase I clinical trial and clinical application in the future.

Citation Format: Almuth F. Kessler, Clara M. Schaeffer, Malgorzata Burek, Ursula Ruschig, Catherine Tempel-Brami, Tali Voloshin, Moshe Giladi, Ellaine Salvador, Ralf-Ingo Ernestus, Mario Löhr, Carola Förster, Carsten Hagemann. Tumor treating fields (TTFields) affect blood brain barrier (BBB) integrity in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 252.

Abstract LB-155: Adherence to tumor treating fields (TTFields) in high-grade glioma patients - a single center experience

Objective: Therapy with Tumor Treating Fields (TTFields) in combination with adjuvant temozolomide following surgical resection and radiochemotherapy significantly increased survival rates in patients with newly diagnosed glioblastoma (ndGBM) in the phase III trial EF-14. The importance of a high compliance/usage rate was supported by a recently published subgroup analysis, revealing a strong correlation of adherence to TTFields therapy with prolonged overall survival (OS). A compliance rate of 75% and more was demonstrated to be a beneficial independent prognostic factor for OS. Here, TTFields therapy adherence of 36 high-grade glioma (HGG) patients is reported.

Methods: 36 patients diagnosed with HGG received TTFields therapy, amongst them 28 patients diagnosed with GBM and 8 patients with astrocytoma WHO°III. Patients were introduced to the therapy during neurooncologic consultation hours. For assessment of adherence to TTFields therapy, the compliance/usage reports generated at the monthly technical check of the device were analyzed.

Results: At initiation of therapy, the median age of HGG patients was 53.5 years (range 29-67 years). 21 of the 28 GBM patients were diagnosed with ndGBM and the remaining ones had recurrences (rGBM). In these patients, the gender distribution female to male was 1:1.15, which represents a higher ratio of female patients compared to the typical GBM population with 1:1.64. At the time point of data cut-off, ndGBM patients were on TTFields therapy for a median of 6.9 months with a median compliance/usage rate of 84.2%. Regarding therapy adherence, no significant differences were observed between female (84.3%) and male (81.1%) patients. Moreover, comparison between patients with ndGBM and recurrent GBM (rGBM) showed no significant difference in therapy adherence with a median compliance of 71.1% in rGBM patients. For patients diagnosed with astrocytoma WHO°III a compliance rate of 84.5% was reported.

Conclusion: In the reported patients receiving TTFields therapy a high median compliance to TTFields therapy was observed, irrespective of sex and diagnosis. No significant differences regarding the compliance/usage rate was detected between the different groups. TTFields therapy was well accepted by all HGG patients, in particular by female GBM patients. Across all groups, the median compliance/usage rate was substantially above the independent prognostic threshold of 75%. In conclusion, TTFields therapy can be recommended to all eligible patients with HGG.

Citation Format: Carsten Hagemann, Judith Weiland, Nadine Lilla, Thomas Linsenmann, Ralf-Ingo Ernestus, Mario Löhr, Almuth F. Kessler. Adherence to tumor treating fields (TTFields) in high-grade glioma patients - a single center experience [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-155.

Circulating MACC1 Transcripts in Glioblastoma Patients Predict Prognosis and Treatment Response

Glioblastoma multiforme is the most aggressive primary brain tumor of adults, but lacks reliable and liquid biomarkers. We evaluated circulating plasma transcripts of metastasis-associated in colon cancer-1 (MACC1), a prognostic biomarker for solid cancer entities, for prediction of clinical outcome and therapy response in glioblastomas. MACC1 transcripts were significantly higher in patients compared to controls. Low MACC1 levels clustered together with other prognostically favorable markers. It was associated with patients’ prognosis in conjunction with the isocitrate dehydrogenase (IDH) mutation status: IDH1 R132H mutation and low MACC1 was most favorable (median overall survival (OS) not yet reached), IDH1 wildtype and high MACC1 was worst (median OS 8.1 months), while IDH1 wildtype and low MACC1 was intermediate (median OS 9.1 months). No patients displayed IDH1 R132H mutation and high MACC1. Patients with low MACC1 levels receiving standard therapy survived longer (median OS 22.6 months) than patients with high MACC1 levels (median OS 8.1 months). Patients not receiving the standard regimen showed the worst prognosis, independent of MACC1 levels (low: 6.8 months, high: 4.4 months). Addition of circulating MACC1 transcript levels to the existing prognostic workup may improve the accuracy of outcome prediction and help define more precise risk categories of glioblastoma patients.

[68Ga]-Pentixafor PET/CT for CXCR4-Mediated Imaging of Vestibular Schwannomas

We have recently demonstrated CXCR4 overexpression in vestibular schwannomas (VS). This study investigated the feasibility of CXCR4-directed positron emission tomography/computed tomography (PET/CT) imaging of VS using the radiolabeled chemokine ligand [⁶⁸Ga]Pentixafor.

Methods: 4 patients with 6 primarily diagnosed or pre-treated/observed VS were enrolled. All subjects underwent [⁶⁸Ga]Pentixafor PET/CT prior to surgical resection. Images were analyzed visually and semi-quantitatively for CXCR4 expression including calculation of tumor-to-background ratios (TBR). Immunohistochemistry served as standard of reference in three patients.

Results: [⁶⁸Ga]Pentixafor PET/CT was visually positive in all cases. SUV_mean and SUV_max were 3.0 ± 0.3 and 3.8 ± 0.4 and TBR_mean and TBR_max were 4.0 ± 1.4 and 5.0 ± 1.7, respectively. Histological analysis confirmed CXCR4 expression in tumors.

Conclusion: Non-invasive imaging of CXCR4 expression using [⁶⁸Ga]Pentixafor PET/CT of VS is feasible and could prove useful for in vivo assessment of CXCR4 expression.

Primary brain amyloidoma, both a neoplastic and a neurodegenerative disease: a case report

BACKGROUND

Scattered extracellular deposits of amyloid within the brain parenchyma can be found in a heterogeneous group of diseases. Its condensed accumulation in the white matter without evidence for systemic amyloidosis is known as primary brain amyloidoma (PBA). Although originally considered as a tumor-like lesion by its space-occupying effect, this condition displays also common hallmarks of a neurodegenerative disorder.

CASE PRESENTATION

A 50-year-old woman presented with a mild cognitive decline and seizures with a right temporal, irregular and contrast-enhancing mass on magnetic resonance imaging. Suspecting a high-grade glioma, the firm tumor was subtotally resected. Neuropathological examination showed no glioma, but distinct features of a neurodegenerative disorder. The lesion was composed of amyloid AL λ aggregating within the brain parenchyma as well as the adjacent vessels, partially obstructing the vascular lumina. Immunostaining confirmed a distinct perivascular inflammatory reaction. After removal of the PBA, mnestic impairments improved considerably, the clinical course and MRI-results are stable in the 8-year follow-up.

CONCLUSION

Based on our histopathological findings, we propose to regard the clinicopathological entity of PBA as an overlap between a neoplastic and neurodegenerative disorder. Since the lesions are locally restricted, they might be amenable to surgery with the prospect of a definite cure.

Expression of activating transcription factor 5 (ATF5) is increased in astrocytomas of different WHO grades and correlates with survival of glioblastoma patients

Background

ATF5 suppresses differentiation of neuroprogenitor cells and is overexpressed in glioblastoma (GBM). A reduction of its expression leads to apoptotic GBM cell death. Data on ATF5 expression in astrocytoma WHO grade II (low-grade astrocytoma [LGA]) are scarce and lacking on recurrent GBM.

Patients and methods

ATF5 mRNA was extracted from frozen samples of patients’ GBM (n=79), LGA (n=40), and normal brain (NB, n=10), quantified by duplex qPCR and correlated with retrospectively collected clinical data. ATF5 protein expression was evaluated by measuring staining intensity on immunohistochemistry.

Results

ATF5 mRNA was overexpressed in LGA (sevenfold, P<0.001) and GBM (tenfold, P<0.001) compared to NB, which was confirmed on protein level. Although ATF5 mRNA expression in GBM showed a considerable fluctuation range, groups of varying biological behavior, that is, local/multifocal growth or primary tumor/relapse and the tumor localization at diagnosis, were not significantly different. ATF5 mRNA correlated with the patients’ age (r=0.339, P=0.028) and inversely with Ki67-staining (r=−0.421, P=0.007). GBM patients were allocated to a low and a high ATF5 expression group by the median ATF5 overexpression compared to NB. Kaplan–Meier analysis and Cox regression indicated that ATF5 mRNA expression significantly correlated with short-term survival (t,12 months, median survival 18 vs 13 months, P=0.022, HR 2.827) and progression-free survival (PFS) (12 vs 6 months, P=0.024). This advantage vanished after 24 months (P=0.084).

Conclusion

ATF5 mRNA expression could be identified as an additional, though not independent factor correlating with overall survival and PFS. Since its inhibition might lead to the selective death of glioma cells, it might serve as a potential ubiquitous therapeutic target in astrocytic tumors.

Effects of tumor treating fields (TTFields) on glioblastoma cells are augmented by mitotic checkpoint inhibition

Tumor treating fields (TTFields) are approved for glioblastoma (GBM) therapy. TTFields disrupt cell division by inhibiting spindle fiber formation. Spindle assembly checkpoint (SAC) inhibition combined with antimitotic drugs synergistically decreases glioma cell growth in cell culture and mice. We hypothesized that SAC inhibition will increase TTFields efficacy. Human GBM cells (U-87 MG, GaMG) were treated with TTFields (200 kHz, 1.7 V/cm) and/or the SAC inhibitor MPS1-IN-3 (IN-3, 4 µM). Cells were counted after 24, 48, and 72 h of treatment and at 24 and 72 h after end of treatment (EOT). Flow cytometry, immunofluorescence microscopy, Annexin-V staining and TUNEL assay were used to detect alterations in cell cycle and apoptosis after 72 h of treatment. The TTFields/IN-3 combination decreased cell proliferation after 72 h compared to either treatment alone (−78.6% vs. TTFields, P = 0.0337; −52.6% vs. IN-3, P = 0.0205), and reduced the number of viable cells (62% less than seeded). There was a significant cell cycle shift from G1 to G2/M phase (P < 0.0001). The apoptotic rate increased to 44% (TTFields 14%, P = 0.0002; IN-3 4%, P < 0.0001). Cell growth recovered 24 h after EOT with TTFields and IN-3 alone, but the combination led to further decrease by 92% at 72 h EOT if IN-3 treatment was continued (P = 0.0288). The combination of TTFields and SAC inhibition led to earlier and prolonged effects that significantly augmented the efficacy of TTFields and highlights a potential new targeted multimodal treatment for GBM.

Abstract 1860: Tumor-treating fields (TTFields) effects on glioblastoma cells are augmented by mitotic checkpoint inhibition

Introduction. Tumor Treating Fields (TTFields) supplementing the standard therapy led to a significant increase in progression free and overall survival of glioblastoma (GBM) patients. These alternating electric fields with low intensity (1-3 V/cm) and intermediate frequency (100-300 kHz) disrupt cell division through inhibition of spindle-fiber formation. The spindle assembly checkpoint (SAC) diminishes therapeutic effects of spindle damaging agents by monitoring correct sister chromatid attachment to functional spindle microtubules and ensures their equal segregation. Inhibition of its key regulator, Monopolar spindle 1 (MPS1), combined with anti-mitotic drugs, led to a synergistic effect on GBM growth in mice. Therefore, we hypothesized that MPS1 inhibition may increase the efficacy of TTFields.

Methods. TTFields were applied using the inovitro system. U87 and GaMG human GBM cells (30,000) were treated with TTFields (200 kHz, 1.7 V/cm) and/or with 4 µM of the MPS1 inhibitor MPS1-IN-3 (IN-3). Cell numbers were evaluated after 24 h, 48 h and 72 h of treatment and also at 24 h and 72 h after end of treatment (eot). Alterations of the cell cycle were detected by FACS analysis, aberrant mitotic figures and malformed nuclei by immunofluorescence microscopy and apoptosis by Annexin V staining and TUNEL-assay after 72 h of treatment.

Results. In all experiments U87 and GaMG yielded similar results. The combination of TTFields and IN-3 caused a more pronounced effect on cell proliferation (78.6% decrease of U87 cell number vs. TTFields (P = 0.0337), 52.6% vs. IN-3 (P = 0.0205) after 72 h). The number of viable cells was reduced (62% less GaMG cells than seeded) and the ratio of dead/alive cells increased. Significantly less cells re-entered the G1 phase (P &lt; 0.0001), while the number of cells in G2/M- and sub-G1-phase was increased. Very distinct mitotic figures and aberrant nuclei were visible, leading to apoptosis in 44% of the U87 cells (TTFields 14%, P = 0.0002; IN-3 4%, P &lt; 0.0001). After discontinuation of TTFields treatment alone, it took 24 h for the cells to start recovery. In contrast, the number of cells treated with IN-3 and TTFields, further decreased by 92% at 72 h after eot (P = 0.0288).

Conclusions. TTFields are an approved new treatment modality for GBM. A combination of physically damaging the spindle apparatus by TTFields and chemical inhibition of the SAC led to earlier and prolonged effects, which significantly augment TTFields efficacy and even may bridge TTFields treatment interruption, promising a new targeted multimodal treatment Option.

Citation Format: Almuth F. Kessler, Greta E. Frömbling, Franziska Gross, Mirja Hahn, Wilfrid Dzokou, Ralf-Ingo Ernestus, Mario Löhr, Carsten Hagemann. Tumor-treating fields (TTFields) effects on glioblastoma cells are augmented by mitotic checkpoint inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1860.

CXCR4: A new player in vestibular schwannoma pathogenesis

BACKGROUND

CXCR4 is a chemokine receptor that recruits blood stem cells and increases tumor cell growth and invasiveness. We examined CXCR4 expression in vestibular schwannomas (VS) from patients with and without neurofibromatosis type 2 (NF2) and correlated the levels with the patients' clinical characteristics. The aim was to determine whether CXCR4 can be used as a prognostic marker and as a target for systemic therapy.

RESULTS

Overall, CXCR4 mRNA levels were 4.6-fold higher in VS versus control; the levels were 4.9-fold higher in NF2 patients and 4.2-fold higher in sporadic VS patients. IHC and WB showed heterogeneous protein expression, and CXCR4 was expressed mainly in S100-positive Schwann cells. There was no correlation between the CXCR4 protein levels and tumor extension. However, there was a trend towards correlation between higher expression levels and greater hearing loss.

MATERIALS AND METHODS

CXCR4 mRNA and protein levels were determined in VS samples (n = 60); of these, 30 samples were from patients with NF2. Healthy nerves from autopsies served as controls. CXCR4 mRNA levels were measured by PCR, and protein levels were measured by immunohistochemistry (IHC) and Western blotting (WB). Tumor extension and hearing loss were categorized according to the Hannover Classification as clinical parameters.

CONCLUSIONS

CXCR4 mRNA was overexpressed in VS relative to healthy vestibular nerves, and there was a trend towards higher CXCR4 expression levels being correlated with greater functional impairment. Thus, CXCR4 may be a prognostic marker of VS, and CXCR4 inhibition has potential as a systemic approach for the treatment of VS.

Transcriptomic analysis of aggressive meningiomas identifies PTTG1 and LEPR as prognostic biomarkers independent of WHO grade

Meningiomas are frequent central nervous system tumors. Although most meningiomas are benign (WHO grade I) and curable by surgery, WHO grade II and III tumors remain therapeutically challenging due to frequent recurrence. Interestingly, relapse also occurs in some WHO grade I meningiomas. Hence, we investigated the transcriptional features defining aggressive (recurrent, malignantly progressing or WHO grade III) meningiomas in 144 cases. Meningiomas were categorized into non-recurrent (NR), recurrent (R), and tumors undergoing malignant progression (M) in addition to their WHO grade. Unsupervised transcriptomic analysis in 62 meningiomas revealed transcriptional profiles lining up according to WHO grade and clinical subgroup. Notably aggressive subgroups (R+M tumors and WHO grade III) shared a large set of differentially expressed genes (n=332; p<0.01, FC>1.25). In an independent multicenter validation set (n=82), differential expression of 10 genes between WHO grades was confirmed. Additionally, among WHO grade I tumors differential expression between NR and aggressive R+M tumors was affirmed for PTTG1, AURKB, ECT2, UBE2C and PRC1, while MN1 and LEPR discriminated between NR and R+M WHO grade II tumors. Univariate survival analysis revealed a significant association with progression-free survival for PTTG1, LEPR, MN1, ECT2, PRC1, COX10, UBE2C expression, while multivariate analysis identified a prediction for PTTG1 and LEPR mRNA expression independent of gender, WHO grade and extent of resection. Finally, stainings of PTTG1 and LEPR confirmed malignancy-associated protein expression changes. In conclusion, based on the so far largest study sample of WHO grade III and recurrent meningiomas we report a comprehensive transcriptional landscape and two prognostic markers.

High-Efficiency Transfection of Glioblastoma Cells and a Simple Spheroid Migration Assay

Despite international research efforts, patients with glioblastoma multiforme (GBM)-the most common malignant brain tumors in adults-exhibit a very unfavorable prognosis. Their aggressive local growth pattern and increased invasiveness, due to a high motility of the tumor cells, hamper treatment. However, the molecular mechanisms regulating glioblastoma cell migration are still elusive. Here, we describe the combination of a highly efficient cell transfection by Nucleofection^® technology and the generation of spheroids from these transfected glioblastoma cell lines. Nucleofection allows the manipulation of protein expression by overexpression and siRNA mediated protein knockdown. Transfection efficiencies >70% can be achieved with some GBM cell lines. Transfected neurospheres then can be used for migration assays (as described here in detail) and a multitude of other functional assays. In comparison to monolayer cultures, the advantage of spheroids is their resemblance with organized tissue in combination with the accuracy of in vitro methodology and marked experimental flexibility.

Implanting Glioblastoma Spheroids into Rat Brains and Monitoring Tumor Growth by MRI Volumetry

The outcome of patients suffering from glioblastoma multiforme (GBM) remains poor with a median survival of less than 15 months. To establish innovative therapeutical approaches or to analyze the effect of protein overexpression or protein knockdown by RNA interference in vivo, animal models are mandatory. Here, we describe the implantation of C6 glioma spheroids into the rats' brain and how to follow tumor growth by MRI scans. We show that C6 cells grown in Sprague-Dawley rats share several morphologic features of human glioblastoma like pleomorphic cells, areas of necrosis, vascular proliferation, and tumor cell invasion into the surrounding brain tissue. In addition, we describe a method for tumor volumetry utilizing the CISS 3D- or contrast-enhanced T1-weighted 3D sequence and freely available post-processing software.

(68)Ga-Pentixafor-PET/CT for Imaging of Chemokine Receptor 4 Expression in Glioblastoma

Chemokine receptor-4 (CXCR4) has been reported to be overexpressed in glioblastoma (GBM) and to be associated with poor survival. This study investigated the feasibility of non-invasive CXCR4-directed imaging with positron emission tomography/computed tomography (PET/CT) using the radiolabelled chemokine receptor ligand ⁶⁸Ga-Pentixafor.

15 patients with clinical suspicion on primary or recurrent glioblastoma (13 primary, 2 recurrent tumors) underwent ⁶⁸Ga-Pentixafor-PET/CT for assessment of CXCR4 expression prior to surgery. O-(2-¹⁸F-fluoroethyl)-L-tyrosine (¹⁸F-FET) PET/CT images were available in 11/15 cases and were compared visually and semi-quantitatively (SUV_max, SUV_mean). Tumor-to-background ratios (TBR) were calculated for both PET probes. ⁶⁸Ga-Pentixafor-PET/CT results were also compared to histological CXCR4 expression on neuronavigated surgical samples.

⁶⁸Ga-Pentixafor-PET/CT was visually positive in 13/15 cases with SUV_mean and SUV_max of 3.0±1.5 and 3.9±2.0 respectively. Respective values for ¹⁸F-FET were 4.4±2.0 (SUV_mean) and 5.3±2.3 (SUV_max). TBR for SUV_mean and SUV_max were higher for ⁶⁸Ga-Pentixafor than for ¹⁸F-FET (SUV_mean 154.0±90.7 vs. 4.1±1.3; SUV_max 70.3±44.0 and 3.8±1.2, p<0.01), respectively. Histological analysis confirmed CXCR4 expression in tumor areas with high ⁶⁸Ga-Pentixafor uptake; regions of the same tumor without apparent ⁶⁸Ga-Pentixafor uptake showed no or low receptor expression.

In this pilot study, ⁶⁸Ga-Pentixafor retention has been observed in the vast majority of glioblastoma lesions and served as readout for non-invasive determination of CXCR4 expression. Given the paramount importance of the CXCR4/SDF-1 axis in tumor biology, ⁶⁸Ga-Pentixafor-PET/CT might prove a useful tool for sensitive, non-invasive in-vivo quantification of CXCR4 as well as selection of patients who might benefit from CXCR4-directed therapy.

Comparison of the amino acid tracers 18F-FET and 18F-DOPA in high-grade glioma patients

High-grade gliomas (HGGs) are the most common malignant primary tumors of the central nervous system. PET probes of amino acid transport such as O-(2-(18)F-fluoroethyl)-l-tyrosine ((18)F-FET), 3,4-dihydroxy-6-(18)F-fluoro-l-phenylalanine ((18)F-DOPA), and (11)C-methionine ((11)C-MET) detect primary and recurrent tumors with a high accuracy. (18)F-FET is predominantly used in Europe, whereas amino acid transport imaging is infrequently done in the United States. The aim of this study was to determine whether (18)F-FET and (18)F-DOPA PET/CT provide comparable information in HGG.

METHODS

Thirty (18)F-FET and (18)F-DOPA PET/CT scans were obtained before surgery or biopsy in 27 patients with high clinical suspicion for primary or recurrent HGG (5 primary, 22 recurrent tumors). (18)F-FET and (18)F-DOPA PET/CT images were compared visually and semiquantitatively (maximum standardized uptake value [SUV(max)], mean SUV [SUV(mean)]). Background (SUV(max) and SUV(mean)) and tumor-to-background ratios (TBRs) were calculated for both PET probes. The degree of (18)F-DOPA uptake in the basal ganglia (SUV(mean)) was also assessed.

RESULTS

Visual analysis revealed no difference in tumor uptake pattern between the 2 PET probes. The SUV(mean) and SUV(max) for (18)F-FET were higher than those of (18)F-DOPA (4.0 ± 2.0 and 4.9 ± 2.3 vs. 3.5 ± 1.6 and 4.3 ± 2.0, respectively; all P < 0.001). TBRs for SUV(mean) but not for SUV(max) were significantly higher for (18)F-FET than (18)F-DOPA (TBR SUV(mean): 3.8 ± 1.7 vs. 3.4 ± 1.2, P = 0.004; TBR SUV(max): 3.3 ± 1.6 and 3.0 ± 1.1, respectively; P = 0.086). (18)F-DOPA uptake by the basal ganglia was present (SUV(mean), 2.6 ± 0.7) but did not affect tumor visualization.

CONCLUSION

Whereas visual analysis revealed no significant differences in uptake pattern for (18)F-FET and (18)F-DOPA in patients with primary or recurrent HGG, both SUVs and TBRs for SUV(mean) were significantly higher for (18)F-FET. However, regarding tumor delineation, both tracers performed equally well and seem equally feasible for imaging of primary and recurrent HGG. These findings suggest that both PET probes can be used based on availability in multicenter trials.

Long-term tumor control of spinal dissemination of cerebellar glioblastoma multiforme by combined adjuvant bevacizumab antibody therapy: a case report

Background

Glioblastoma multiforme located in the posterior fossa is extremely rare with a frequency up to 3.4%. Compared with glioblastoma of the hemispheres the prognosis of infratentorial glioblastoma seems to be slightly better. Absence of brainstem invasion and low expression rates of epidermal growth factor receptor are described as factors for long-time survival due to the higher radiosensitivity of these tumors.

Case presentation

In this case study, we report a German female patient with an exophytic glioblastoma multiforme arising from the cerebellar tonsil and a secondary spinal manifestation. Furthermore, the tumor showed no O (6)-Methylguanine-DNA methyltransferase promotor-hypermethylation and no isocitrate dehydrogenase 1 mutations. All these signs are accompanied by significantly shorter median overall survival. A long-term tumor control of the spinal metastases was achieved by a combined temozolomide/bevacizumab and irradiation therapy, as part of a standard care administered by the treating physician team.

Conclusion

To our knowledge this is the first published case of a combined cerebellar exophytic glioblastoma with a subsequent solid spinal manifestation. Furthermore this case demonstrates a benefit undergoing this special adjuvant therapy regime in terms of overall survival. Due to the limited overall prognosis of the disease, spinal manifestations of glioma are rarely clinically relevant. The results of our instructive case, however, with a positive effect on both life quality and survival warrant treating future patients in the frame of a prospective clinical study.

Bone chips, fibrin glue, and osteogeneration following lateral suboccipital craniectomy: a case report

Background

Suboccipital craniectomy is a conventional approach for exploring cerebellopontine angle lesions. A variety of techniques have been successfully employed to reconstruct a craniectomy. This is the first report about the histological findings after performing a cranioplasty by using a mixture of autologous bone chips and human allogenic fibrin glue.

Case presentation

A 53-year-old German woman underwent left lateral suboccipital retrosigmoidal craniectomy for treatment of trigeminal neuralgia in 2008. Cranioplasty was perfomed by using a mixture of autologous bone chips and human allogenic fibrin glue. Due to recurrent neuralgia, a second left lateral suboccipital craniectomy was performed in 2012. The intraoperative findings revealed a complete ossification of the former craniotomy including widely mature trabecular bone tissue in the histological examination.

Conclusion

A mixture of autologous bone chips and human allogenic fibrin glue seems to provide sufficient bone-regeneration revealed by histological and neuroradiological examinations.

Impact of MACC1 on human malignant glioma progression and patients' unfavorable prognosis

BACKGROUND

Metastasis-associated in colon cancer 1 (MACC1) has been established as an independent prognostic indicator of metastasis formation and metastasis-free survival for patients with colon cancer and other solid tumors. However, no data are available concerning MACC1 expression in human astrocytic tumors. Glioblastoma multiforme (GBM) is the most prevalent primary brain tumor of adulthood, and due to its invasive and rapid growth, patients have unfavorable prognoses. Although these tumors rarely metastasize, their invasive and migratory behavior is similar to those of metastatic cells of tumors of different origin. Thus, we hypothesized that MACC1 may be involved in progression of human gliomas.

METHODS

We performed real-time measurements of proliferation and migration in MACC1-transfected GBM cell lines (U138, U251) and evaluated tumor formation in organotypic hippocampal slice cultures of mice. Semiquantitative and quantitative real-time reverse transcription PCR analyses were performed for MACC1 and for its transcriptional target c-Met in human astrocytoma of World Health Organization grade II (low-grade astrocytoma) and GBM biopsies. Data were validated by MACC1 immunohistochemistry in independent matched samples of low-grade astrocytoma and GBM.

RESULTS

MACC1 increases the proliferative, migratory, and tumor-formation abilities of GBM cells. The c-Met inhibitor crizotinib reduced MACC1-induced migration and tumor formation in organotypic hippocampal slice cultures of mice. Analyzing patients' biopsies, MACC1 expression increased concomitantly with increasing World Health Organization grade. Moreover, MACC1 expression levels allowed discrimination of dormant and recurrent low-grade astrocytomas and of primary and secondary GBM. Strong MACC1 expression correlated with reduced patient survival.

CONCLUSIONS

MACC1 may represent a promising biomarker for prognostication and a new target for treatment of human gliomas.

Effects of the selective MPS1 inhibitor MPS1-IN-3 on glioblastoma sensitivity to antimitotic drugs

BACKGROUND

Glioblastomas exhibit a high level of chemotherapeutic resistance, including to the antimitotic agents vincristine and taxol. During the mitotic agent-induced arrest, glioblastoma cells are able to perform damage-control and self-repair to continue proliferation. Monopolar spindle 1 (MPS1/TTK) is a checkpoint kinase and a gatekeeper of the mitotic arrest.

METHODS

We used glioblastoma cells to determine the expression of MPS1 and to determine the effects of MPS1 inhibition on mitotic errors and cell viability in combination with vincristine and taxol. The effect of MPS1 inhibition was assessed in different orthotopic glioblastoma mouse models (n = 3-7 mice/group). MPS1 expression levels were examined in relation to patient survival.

RESULTS

Using publicly available gene expression data, we determined that MPS1 overexpression corresponds positively with tumor grade and negatively with patient survival (two-sided t test, P < .001). Patients with high MPS1 expression (n = 203) had a median and mean survival of 487 and 913 days (95% confidence intervals [CI] = 751 to 1075), respectively, and a 2-year survival rate of 35%, whereas patients with intermediate MPS1 expression (n = 140) had a median and mean survival of 858 and 1183 days (95% CI = 1177 to 1189), respectively, and a 2-year survival rate of 56%. We demonstrate that MPS1 inhibition by RNAi results in sensitization to antimitotic agents. We developed a selective small-molecule inhibitor of MPS1, MPS1-IN-3, which caused mitotic aberrancies in glioblastoma cells and, in combination with vincristine, induced mitotic checkpoint override, increased aneuploidy, and augmented cell death. MPS1-IN-3 sensitizes glioblastoma cells to vincristine in orthotopic mouse models (two-sided log-rank test, P < .01), resulting in prolonged survival without toxicity.

CONCLUSIONS

Our results collectively demonstrate that MPS1, a putative therapeutic target in glioblastoma, can be selectively inhibited by MPS1-IN-3 sensitizing glioblastoma cells to antimitotic drugs.

The cohesin-interacting protein, precocious dissociation of sisters 5A/sister chromatid cohesion protein 112, is up-regulated in human astrocytic tumors

Glioblastoma multiforme (GBM) is the most prevalent, highly malignant, invasive and difficult-to-treat primary brain tumor in adults. At the genetic level, it is characterized by a high degree of chromosomal instability and aneuploidy. It has been shown that defects in the mitotic spindle checkpoint could lead to the development of aneuploidy as well as tumorigenesis. Additional proteins regulating sister chromatid cohesion could also be involved in maintaining the fidelity of chromosome segregation. One such protein is the precocious dissociation of sisters 5A (Pds5A), also known as sister chromatid cohesion protein 112. It is a nuclear protein, expressed from the S right through to the mitotic phase. It is highly conserved from yeast to man and plays a role in the establishment, maintenance and dissolution of sister chromatid cohesion. The mutation of Pds5A orthologs in lower organisms results in chromosome missegregation, aneuploidy and DNA repair defects. It is considered that such defects can cause either cell death or contribute to the development of cancer cells. Indeed, altered expression levels of Pds5A have been observed in tumors of the breast, kidney, oesophagus, stomach, liver and colon. Malignant gliomas, however, have not been analysed so far. Herein, we report on the cloning of Rattus norvegicus Pds5A and on the analysis of its expression pattern in rat tissue. We also show that Pds5A is significantly overexpressed at both the mRNA and protein level and that this overexpression correlates positively with the WHO grade of human gliomas. However, functional assays show that the siRNA-mediated knockdown of Pds5A affects sister chromatid cohesion but does not influence mitotic checkpoint function or the proliferation and survival of GBM cells. Although the mechanism by which Pds5A functions in GBM cells remains unclear, its overexpression in high grade gliomas implies that it could play a pivotal role during the development and progression of astrocytic tumors.