Temporal and regional expression changes and co-staining patterns of metabolic and stemness-related markers during glioblastoma progression

Glioblastomas (GBMs) are characterized by high heterogeneity, involving diverse cell types, including those with stem-like features contributing to GBM's malignancy. Moreover, metabolic alterations promote growth and therapeutic resistance of GBM. Depending on the metabolic state, antimetabolic treatments could be an effective strategy. Against this background, we investigated temporal and regional expression changes and co-staining patterns of selected metabolic markers [pyruvate kinase muscle isozyme 1/2 (PKM1/2), glucose transporter 1 (GLUT1), monocarboxylate transporter 1/4 (MCT1/4)] in a rodent model and patient-derived samples of GBM. To understand the cellular sources of marker expression, we also examined the connection of metabolic markers to markers related to stemness [Nestin, Krüppel-like factor 4 (KLF4)] in a regional and temporal context. Rat tumour biopsies revealed a temporally increasing expression of GLUT1, higher expression of MCT1/4, Nestin and KLF4, and lower expression of PKM1 compared to the contralateral hemisphere. Patient-derived tumours showed a higher expression of PKM2 and Nestin in the tumour centre vs. edge. Whereas rare co-staining of GLUT1/Nestin was found in tumour biopsies, PKM1/2 and MCT1/4 showed a more distinct co-staining with Nestin in rats and humans. KLF4 was mainly co-stained with GLUT1, MCT1 and PKM1/2 in rat and human tumours. All metabolic markers yielded individual co-staining patterns among themselves. Co-staining mainly occurred later in tumour progression and was more pronounced in tumour centres. Also, positive correlations were found amongst markers that showed co-staining. Our results highlight a link between metabolic alterations and stemness in GBM progression, with complex distinctions depending on studied markers, time points and regions.

Tumor associated microglia/macrophages utilize GPNMB to promote tumor growth and alter immune cell infiltration in glioma

Tumor-associated microglia and blood-derived macrophages (TAMs) play a central role in modulating the immune suppressive microenvironment in glioma. Here, we show that GPNMB is predominantly expressed by TAMs in human glioblastoma multiforme and the murine RCAS-PDGFb high grade glioma model. Loss of GPNMB in the in vivo tumor microenvironment results in significantly smaller tumor volumes and generates a pro-inflammatory innate and adaptive immune cell microenvironment. The impact of host-derived GPNMB on tumor growth was confirmed in two distinct murine glioma cell lines in organotypic brain slices from GPNMB-KO and control mice. Using published data bases of human glioma, the elevated levels in TAMs could be confirmed and the GPNMB expression correlated with a poorer survival.

Classification of Brain Tumors by Nanopore Sequencing of Cell-Free DNA from Cerebrospinal Fluid

BACKGROUND

Molecular brain tumor diagnosis is usually dependent on tissue biopsies or resections. This can pose several risks associated with anesthesia or neurosurgery, especially for lesions in the brain stem or other difficult-to-reach anatomical sites. Apart from initial diagnosis, tumor progression, recurrence, or the acquisition of novel genetic alterations can only be proven by re-biopsies.

METHODS

We employed Nanopore sequencing on cell-free DNA (cfDNA) from cerebrospinal fluid (CSF) and analyzed copy number variations (CNV) and global DNA methylation using a random forest classifier. We sequenced 129 samples with sufficient DNA. These samples came from 99 patients and encompassed 22 entities. Results were compared to clinical diagnosis and molecular analysis of tumor tissue, if available.

RESULTS

110/129 samples were technically successful, and 50 of these contained detectable circulating tumor DNA (ctDNA) by CNV or methylation profiling. ctDNA was detected in samples from patients with progressive disease but also from patients without known residual disease. CNV plots showed diagnostic and prognostic alterations, such as C19MC amplifications in embryonal tumors with multilayered rosettes or Chr.1q gains and Chr.6q losses in posterior fossa group A ependymoma, respectively. Most CNV profiles mirrored the profiles of the respective tumor tissue. DNA methylation allowed exact classification of the tumor in 22/110 cases and led to incorrect classification in 2/110 cases. Only 5/50 samples with detected ctDNA contained tumor cells detectable through microscopy.

CONCLUSIONS

Our results suggest that Nanopore sequencing data of cfDNA from CSF samples may be a promising approach for initial brain tumor diagnostics and an important tool for disease monitoring.

[Retrocochlear diagnostics for acute hearing loss and successful therapy]

A 41-year-old female patient presented due to acute onset of unilateral hearing loss 3 months previously and persistent since then. Systemic therapy with oral glucocorticoids in decreasing doses had been performed beforehand, but did not lead to any improvement. In the course of audiological diagnostics, based on subjective and objective methods, a retrocochlear hearing disorder was suspected. A meningioma was diagnosed by diagnostic imaging. Subsequent surgical removal achieved a significant hearing improvement.

Venous 3D Phase Contrast Magnetic Resonance Angiography Increases Diagnostic Certainty in Children with Ventriculoperitoneal Shunt and Suspected Shunt Failure

BACKGROUND

Clinical symptoms in children with suspected malfunction of ventriculoperitoneal shunt may not be specific and difficult to interpret. The presence or absence of ventricular enlargement on magnetic resonance imaging (MRI) does not reliably predict raised intracranial pressure (ICP) in these patients. Therefore, the aim was to investigate the diagnostic utility of 3D venous phase-contrast MR angiography (vPCA) in these patients.

MATERIALS

The MR studies of two groups of patients at two different examination dates were retrospectively analyzed; one group without clinical symptoms on both examinations and one with symptoms of shunt dysfunction on one examination receiving surgery. Both MRI examinations had to have been performed including axial T2 weighted (T2-w) images and 3D vPCA. Two (neuro)radiologists evaluated T2-w images alone and in combination with 3D vPCA in terms of suspected elevated ICP. Interrater reliability, sensitivity and specificity were assessed.

RESULTS

Compression of venous sinuses was seen significantly more often in patients with shunt failure (p = 0.00003). Consequently, evaluation of 3D vPCA and T2-w images increases sensitivity to 0.92/1.0 compared to T2-w images alone with 0.69/0.77, the interrater agreement for the diagnosis of shunt failure rises from κ = 0.71 to κ = 0.837. Concerning imaging markers, three groups could be identified in children with shunt failure.

CONCLUSION

In accordance with the literature, the results show that ventricular morphology alone is an unreliable marker for elevated ICP in children with shunt malfunction. The findings confirmed 3D vPCA as a valuable supplemental diagnostic tool improving diagnostic certainty for children with unchanged ventricular size in cases of shunt failure.

Surgical approach for convexity meningiomas: An analysis of the preoperative clinical signs, radiological features and surgical outcomes of these tumors

BACKGROUND

Convexity meningiomas (CM) can be successfully treated with neurosurgery. However, clinical complications due to CM have been reported. Moreover, systematic investigations of CM with respect to all relevant clinical factors are currently lacking.

METHODS

We performed a systematic investigation in 210 patients with supratentorial CM considering all relevant clinical and radiological factors, with a follow-up time of 19.5 years.

RESULTS

Among 812 patients with intracranial meningiomas treated in our department (2003-2020), 28.2 % of intracranial meningiomas were located over the supratentorial convexity, and the patients had a median age of 62 years (95 % CI:59-64). The median follow-up was 30.4 months (95 % CI:21.6-37.1). Tumor-related symptoms were observed in 88.1 % of patients. The most common preoperative symptom was headache (28.1 %), followed by seizure (19.5 %). Symptomatic patients had significantly higher tumor volumes than asymptomatic patients (p = 0.0003; 24.5 cm3 and 6.98 cm3, respectively). Complete tumor resection was achieved in 92.9 % of patients. The most common postoperative complication was bleeding (7.1 %) in the approach area. Of all bleedings, only three were intracerebral hemorrhages and did not require surgical intervention. The second most common complication was postoperative seizure (4.7 %). The multiple logistic regression analyses showed that tumor volume (OR:1.007; 95 % CI:1.001-1.013; p = 0.02) and brain infiltration by the tumor (OR:1.961; 95 % CI:1.028-3.741; p = 0.04) had a significant impact on postoperative complications. The postoperative and final KPS scores significantly improved (p < 0.001). The tumor recurrence rate was 6.2 %, with a median time of 38 months. No surgery-related deaths occurred.

CONCLUSION

A large tumor volume and brain infiltration by the tumor were significant factors for postoperative complications. The clinical conditions significantly improved postoperatively and further during the follow-up period.

Insights into Gene Regulation under Temozolomide-Promoted Cellular Dormancy and Its Connection to Stemness in Human Glioblastoma

The aggressive features of glioblastoma (GBM) are associated with dormancy. Our previous transcriptome analysis revealed that several genes were regulated during temozolomide (TMZ)-promoted dormancy in GBM. Focusing on genes involved in cancer progression, Chemokine (C-C motif) Receptor-Like (CCRL)1, Schlafen (SLFN)13, Sloan-Kettering Institute (SKI), Cdk5 and Abl Enzyme Substrate (Cables)1, and Dachsous Cadherin-Related (DCHS)1 were selected for further validation. All showed clear expression and individual regulatory patterns under TMZ-promoted dormancy in human GBM cell lines, patient-derived primary cultures, glioma stem-like cells (GSCs), and human GBM ex vivo samples. All genes exhibited complex co-staining patterns with different stemness markers and with each other, as examined by immunofluorescence staining and underscored by correlation analyses. Neurosphere formation assays revealed higher numbers of spheres during TMZ treatment, and gene set enrichment analysis of transcriptome data revealed significant regulation of several GO terms, including stemness-associated ones, indicating an association between stemness and dormancy with the involvement of SKI. Consistently, inhibition of SKI during TMZ treatment resulted in higher cytotoxicity, proliferation inhibition, and lower neurosphere formation capacity compared to TMZ alone. Overall, our study suggests the involvement of CCRL1, SLFN13, SKI, Cables1, and DCHS1 in TMZ-promoted dormancy and demonstrates their link to stemness, with SKI being particularly important.

Establishment of a Rodent Glioblastoma Partial Resection Model for Chemotherapy by Local Drug Carriers-Sharing Experience

Local drug delivery systems (LDDS) represent a promising therapy strategy concerning the most common and malignant primary brain tumor glioblastoma (GBM). Nevertheless, to date, only a few systems have been clinically applied, and their success is very limited. Still, numerous new LDDS approaches are currently being developed. Here, (partial resection) GBM animal models play a key role, as such models are needed to evaluate the therapy prior to any human application. However, such models are complex to establish, and only a few reports detail the process. Here, we report our results of establishing a partial resection glioma model in rats suitable for evaluating LDDS. C6-bearing Wistar rats and U87MG-spheroids- and patient-derived glioma stem-like cells-bearing athymic rats underwent tumor resection followed by the implantation of an exemplary LDDS. Inoculation, tumor growth, residual tumor tissue, and GBM recurrence were reliably imaged using high-resolution Magnetic Resonance Imaging. The release from an exemplary LDDS was verified in vitro and in vivo using Fluorescence Molecular Tomography. The presented GBM partial resection model appears to be well suited to determine the efficiency of LDDS. By sharing our expertise, we intend to provide a powerful tool for the future testing of these very promising systems, paving their way into clinical application.

Sequential Treatment with Temozolomide Plus Naturally Derived AT101 as an Alternative Therapeutic Strategy: Insights into Chemoresistance Mechanisms of Surviving Glioblastoma Cells

Glioblastoma (GBM) is a poorly treatable disease due to the fast development of tumor recurrences and high resistance to chemo- and radiotherapy. To overcome the highly adaptive behavior of GBMs, especially multimodal therapeutic approaches also including natural adjuvants have been investigated. However, despite increased efficiency, some GBM cells are still able to survive these advanced treatment regimens. Given this, the present study evaluates representative chemoresistance mechanisms of surviving human GBM primary cells in a complex in vitro co-culture model upon sequential application of temozolomide (TMZ) combined with AT101, the R(-) enantiomer of the naturally occurring cottonseed-derived gossypol. Treatment with TMZ+AT101/AT101, although highly efficient, yielded a predominance of phosphatidylserine-positive GBM cells over time. Analysis of the intracellular effects revealed phosphorylation of AKT, mTOR, and GSK3ß, resulting in the induction of various pro-tumorigenic genes in surviving GBM cells. A Torin2-mediated mTOR inhibition combined with TMZ+AT101/AT101 partly counteracted the observed TMZ+AT101/AT101-associated effects. Interestingly, treatment with TMZ+AT101/AT101 concomitantly changed the amount and composition of extracellular vesicles released from surviving GBM cells. Taken together, our analyses revealed that even when chemotherapeutic agents with different effector mechanisms are combined, a variety of chemoresistance mechanisms of surviving GBM cells must be taken into account.

A biopolymeric mesh enriched with PLGA microparticles loaded with AT101 for localized Glioblastoma treatment

Current treatment strategies for glioblastoma (GBM) including surgical resection and adjuvant radio/chemotherapy result in a limited progression-free survival time of patients due to rapidly occurring tumor recurrences. The urgent need for more effective treatments has led to the development of different approaches for localized drug delivery systems (DDS) offering the advantages of reduced systemic side effects. A promising candidate for the treatment of GBMs is AT101, the R-(-)-enantiomer of gossypol due to its ability to induce apoptosis or trigger autophagic cells death in tumor cells. Here, we present an alginate-based drug-releasing mesh ladened with AT101-loaded PLGA microspheres (AT101-GlioMesh). The AT101-loaded PLGA microspheres were fabricated using an oil-in-water emulsion solvent evaporation method obtaining a high encapsulation efficiency. The drug-loaded microspheres enabled the release of AT101 over several days at the tumor site. The cytotoxic effect of the AT101-loaded mesh was evaluated using two different GBM cell lines. Strikingly, encapsulation of AT101 in PLGA-microparticles and subsequent embedding in GlioMesh resulted in a sustained delivery and more efficient cytotoxic effect of AT101 on both GBM cell lines. Thus, such a DDS holds promise for GBM therapy likely by preventing the development of tumor recurrences.

Impact of peritumoral brain edema on pre- and postoperative clinical conditions and on long-term outcomes in patients with intracranial meningiomas

BACKGROUND

Peritumoral brain edema (PTBE) is a common complication related to intracranial meningiomas. In several studies, researchers have investigated the pathogenesis of PTBE, and the factors involved in its development in patients with intracranial meningiomas have been reported. However, very little is known about the clinical effect of PTBE on patients with intracranial meningiomas; therefore, a systematic examination of this matter is necessary.

METHODS

In this study, we performed a systematic examination of 696 patients with primary intracranial meningiomas to assess the effect of preoperative PTBE on preoperative symptoms, neurological deficits and postoperative complications, and long-term outcomes with a follow-up period of 16.8 years. We performed a univariate analysis and multiple regression for specific outcomes and adjusted for other relevant clinical factors.

RESULTS

A total of 627 (90.1%) patients were symptomatic preoperatively. One hundred eighty-eight (90.8%) patients with small to moderate PTBE and 125 (98.4%) patients with severe PTBE presented with symptoms significantly more often than the 314 (86.7%) patients without PTBE (p < 0.001, univariate analysis). Cognitive deficits, palsy and seizure were significantly more present, preoperatively, in patients with PTBE than in patients without PTBE (p < 0.001, univariate analysis). Two hundred fifty-five (36.6%) patients experienced surgical and systemic complications postoperatively. The complication rate was significantly higher in patients with PTBE; 41.5% for patients with small to moderate PTBE and 52.8% for patients with severe PTBE, compared to 28.2% of patients without PTBE (p < 0.001, univariate analysis). Furthermore, pre- and postoperative KPS scores were significantly lower in patients with PTBE (p < 0.001). Patients with PTBE required additional medical support significantly more often (p < 0.001) and had a significantly longer hospital stay (p < 0.001). The mortality rate was higher in patients with PTBE immediately after surgery and in the follow-up period; however, the difference was not significant. The neurological condition of all patients improved in the follow-up and did not show significant differences between patients with and without preoperative PTBE (p = 0.6361). Multiple logistic regression analyses revealed a significant association between PTBE and the presence of preoperative cognitive deficits, the incidences of seizure and postoperative complications, and low pre- and postoperative KPS scores.

CONCLUSIONS

Preoperative PTBE significantly increased the incidences of specific preoperative symptoms, neurological deficits and postoperative complications in patients with intracranial meningiomas. After surgery, patients with preoperative PTBE required medical support significantly more often than patients without PTBE. However, all patients had favorable outcomes after surgery.

Reappraisal of Intracerebral Hemorrhages and Intracerebral Hemorrhage Grading Scale Score in Surgically and Medically Managed Cerebellar Intracerebral Hemorrhage

BACKGROUND

As compared with supratentorial intracerebral hemorrhages (ICH), bleeds that occur within the cerebellum require special consideration given the nature of the posterior fossa.

OBJECTIVE

To validate ICH and ICH grading scale (ICH-GS) scores in patients with cerebellar hemorrhage and examine the outcomes of patients managed surgically as compared with those who underwent conservative treatment.

METHODS

This observational multicenter study included 475 patients with cerebellar hemorrhage from 9 different neurosurgical departments in Germany between 2005 and 2021. The prognostic accuracy of ICH and ICH-GS scores were calculated by the area under the curve of the receiver operating characteristic curves. Analyzed outcomes were the in-hospital mortality, mortality at 6 months, in-hospital outcome, and outcome at 6 months.

RESULTS

Of 403 patients, 252 patients (62.5%) underwent surgical treatment and 151 patients (37.5%) conservative treatment. Both ICH and ICH-GS scores demonstrated good prognostic accuracy regarding both overall mortality and functional outcomes. In those patients presenting with severe cerebellar hemorrhages, ie, ICH score >3 and ICH-GS score >11, overall mortality was significantly lower in surgically treated patients. Mortality was significantly higher in those patients managed surgically who presented with ICH scores ≤3; in such patients, improved outcomes were noted when the hematoma was treated conservatively.

CONCLUSION

ICH and ICH scores are useful tools for prediction of survival and outcome in patients with cerebellar ICH. Surgical management may be beneficial for those who present with severe cerebellar ICH as reflected by ICH scores >3, while conservative management seems reasonable in patients with lower ICH scores.

Sustainability of large-scale implementation of shared decision making with the SHARE TO CARE program

Introduction

SHARE TO CARE (S2C) is a comprehensive implementation program for shared decision making (SDM). It is run at the University Hospital Schleswig-Holstein (UKSH) in Kiel, Germany, and consists of four combined intervention modules addressing healthcare professionals and patients: (1) multimodal training of physicians (2) patient activation campaign including the ASK3 method, (3) online evidence-based patient decision aids (4) SDM support by nurses. This study examines the sustainability of the hospital wide SDM implementation by means of the Neuromedical Center comprising the Departments of Neurology and Neurosurgery.

Methods

Between 2018 and 2020, the S2C program was applied initially within the Neuromedical Center: We implemented the patient activation campaign, trained 89% of physicians (N = 56), developed 12 patient decision aids and educated two decision coaches. Physicians adjusted the patients' pathways to facilitate the use of decision aids. To maintain the initial implementation, the departments took care that new staff members received training and decision aids were updated. The patient activation campaign was continued. To determine the sustainability of the initial intervention, the SDM level after a maintenance phase of 6-18 months was compared to the baseline level before implementation. Therefore, in- and outpatients received a questionnaire via mail after discharge. The primary endpoint was the "Patient Decision Making" subscale of the Perceived Involvement in Care Scale (PICS_PDM). Secondary endpoints were an additional scale measuring SDM (CollaboRATE), and the PrepDM scale, which determines patients' perceived health literacy while preparing for decision making. Mean scale scores were compared using t-tests.

Results

Patients reported a significantly increased SDM level (PICS_PDM p = 0.02; Hedges' g = 0.33; CollaboRATE p = 0.05; Hedges' g = 0.26) and improved preparation for decision making (PrepDM p = 0.001; Hedges' g = 0.34) 6-18 months after initial implementation of S2C.

Discussion

The S2C program demonstrated its sustainability within the Neuromedical Center at UKSH Kiel in terms of increased SDM and health literacy. Maintaining the SDM implementation required a fraction of the initial intensity. The departments took on the responsibility for maintenance. Meanwhile, an additional health insurance-based reimbursement for S2C secures the continued application of the program.

Conclusion

SHARE TO CARE promises to be suitable for long-lasting implementation of SDM in hospitals.

TMIC-76. HUMANIN RELEASE FROM TUMOR ASSOCIATED MYELOID CELLS PROMOTES GLIOMA CHEMORESISTANCE

Transcriptomic screens of brain tumor (glioblastoma; GBM) parenchymal cells indicated tumor supporting traits of the GBM microenvironment, but largely excluded mitochondrially enriched gene-sets. Here, we show that a mitochondrial transcript of GBM parenchymal cells contributes to therapy resistance. We inspected the non-coding transcriptome of human GBM associated myeloid cells (GAM) and observed an upregulation of the mitochondrial ribosomal subunit MT-RNR2, which contains an open reading frame for the signaling peptide humanin. Immunohistology disclosed that humanin was preponderant in GAM. In vitro assays with a range of human stem-like GBM cells (GSCs) revealed that nanomolar concentrations of humanin can drive tumor cell expansion and chemoresistance to temozolomide. A series of genetic, pharmacological and Western blotting experiments showed that extracellular humanin increased GSC viability via stimulation of the GP130/IL6ST receptor and MAPK (Erk) activation. Humanin responsiveness was subject to inter-individual heterogeneity and predominated in GSC with high expression levels of the IL6ST subunit. Mechanistically, humanin promoted the ATR-dependent DNA-repair machinery in GSCs via induction of the DNA-clamp component HUS1. A slice culture model containing human microglia and GSCs confirmed these observations. Humanin is absent from the mouse brain. Exogenous delivery of humanin into orthotopic GBM mouse models or over-expression specifically of a secreted humanin variant recapitulated the in vitro findings. Blockade of the trimeric interleukin receptor with the brain permeant, FDA-approved drug bazedoxifene blocked humanin-mediated chemoresistance in vitro and in vivo. Overall, we identified a clinically applicable compound together with a predictive marker to prevent chemoresistance in a human-specific GBM model.

PATH-45. INTRAEPIGLIOM - RAPID SEQUENCING-BASED DIAGNOSIS OF BRAIN TUMORS

The intraoperative diagnosis of brain tumors remains a clinical challenge despite recent technological advances. The current clinical practice differentiates non-surgical brain tumors from those preferably treated with cytoreductive surgery employing intraoperative frozen section diagnostics. A detailed molecular diagnosis required for this classification task within the timeframe of a routine neurosurgical procedure is currently unavailable. We have analyzed a clinical cohort of several brain tumor entities using Nanopore long-read sequencing on two Oxford Nanopore Technologies sequencing platforms (MinION, PromethION). Since currently available molecular cancer classifiers such as the DKFZ methylation profiling classifier cannot be readily adapted to real-time sequencing analysis, we implemented a novel algorithm (MethyLYZR) to predict the underlying cancer type. Publicly available Illumina Infinium array data were used to train the classifier to distinguish 91 brain tumor classes. For validation of classification accuracy, we conducted a comprehensive validation strategy. Both nanopore platforms could sequence more than 5,000 pre-selected CpG within less than 20 minutes for most of our samples. When combining an optimized library preparation protocol with the time used for sequencing the minimal number of CpGs needed for classification, we saw sample-to-answer times of less than 1 hour – in many cases within 45 minutes - from receiving a fresh biopsy to a robust cancer type prediction. Comparing actual and predicted diagnoses resulted in a favorable error rate, indicating potentially highly clinical validity. Our real-time based molecular diagnostic algorithm enables, in most cases, a reliable diagnostic call within the timeframe of a typical neuro-oncological surgery. MethyLYZR as a predictive tool may allow us to adjust the surgical strategy and deliver the prognosis to our patients right after surgery, thus allowing for as-of-yet unexplored opportunities for the intraoperative application of individualized therapeutic modalities.

OS10.7.A Activation of the CCR8-ACP5 axis by human microglia/macrophage derived CCL18 promotes glioma growth

Background

Glioblastoma multiforme is a highly malignant primary brain tumor with an average survival of 14 months and very limited therapeutic options. Glioma associated microglia and macrophages (GAMs) foster tumor growth by releasing several cytokines, which have only partly been identified. Here, we studied the chemokine (C-C motif) ligand 18 (CCL18), a chemokine which is only expressed in human, but not rodent GAMs, in a novel ex-vivo brain slice model including transplantation of human induced pluripotent stem cells (iPSC) derived human microglia (iMGL) and human glioma cells in to murine brain slices, which had been depleted of intrinsic murine microglia before.

Material and Methods

After establishing the humanized ex-vivo brain slice model, we performed immunohistochemical analysis (IHC) of growth and invasiveness, qrtPCR on glioma cells isolated by magnetic-activated cell sorting (MACS), functional assays measuring invasiveness, proliferation, migration and colony formation of glioma cells in vitro and in slice experiments. Corresponding studies on tumor growth and invasiveness were performed after treatment with a CCL18 neutralizing antibody, a CCR8 neutralizing antibodies and knockdown of CCR8, ACP5 (Acid Phosphatase 5) and PITPNM3 with small interfering RNA (siRNA) and short hairpin RNA (shRNA). QrtPCR, IHC and Westernblot analysis were performed on primary glioma specimens. We also conducted bioinformatic analyses, based on the TCGA GBM, GLIOVIS and GEPIA databases.

Results

We observed that CCL18 was highly expressed in GAMs, whereas CCR8 was only expressed in glioma cells. We identified the chemokine (C-C motif) receptor 8 (CCR8) as a functional receptor for CCL18 and ACP5 as an important down-stream signaling component in glioma cells. Activation of the CCL18/CCR8/ACP5 signaling pathway in human glioblastoma was associated with enhanced tumor growth and invasiveness.

Conclusion

GAMs derived CCL18 promoted glioma growth by activation of the CCR8/ACP5 axis in human glioma cells and therefore is a potential therapeutic target.

P11.13.B Long-term outcome of patients with WHO grade 3 glioma treated with radiotherapy and temozolomide or radiotherapy alone

Background

For a long time, for patients with WHO grade 3 glioma the gold-standard after surgical treatment has been radiotherapy (RT). Since the combined radio-chemotherapy became the standard as a postoperative therapy for patients with glioblastoma in 2005, the role of radio-chemotherapy with temozolomide (RT/TMZ) for patients with WHO grade 3 glioma has long been controversial. Evidence is growing that RT/TMZ provides advantages in progression-free survival (PFS) and overall survival (OS) in WHO grade 3 gliomas as well. The aim of this study was to compare RT/TMZ (after 2005) and RT alone (before or after 2005) for patients with WHO grade 3 glioma in the long term.

Material and Methods

167 adult patients with first diagnosis of a WHO grade 3 glioma between 1994 and 2019 and treatment with surgery and either RT/TMZ (after 2005) or RT (before or after 2005) were included. Clinical and sociodemographic parameters as well as IDH1/2-mutation-, MGMT-promotor methylation- and 1p/19q-codeletion-status of the patient’s FFPE-tumor-tissue have been retrospectively investigated. Primary outcome was PFS and OS depending on postoperative treatment with RT before 2005 (n = 75) vs. RT after 2005 (n = 33) vs. RT/TMZ after 2005 (n = 48). Therefore, Kaplan-Meier analysis has been performed.

Results

RT before 2005 showed a significant advantage over RT/TMZ after 2005 and RT after 2005 regarding the PFS (p &lt; 0.05) and OS (p &lt; 0.001). Median PFS was 3.34 years (95%-CI = 1.08 - 5.59) for RT before 2005 vs. 1.96 years (95%-CI = 0.89 - 3.02) for RT/TMZ after 2005 and 1.22 years (95%-CI = 0.00 - 2.50) for RT after 2005. RT/TMZ after 2005 showed a significant advantage over RT after 2005 regarding the OS (p &lt; 0.05). Median OS was not reached for RT before 2005 vs. 4.90 years (95%-CI = 2.14 - 7.66) for RT/TMZ after 2005 and 1.60 years (95%CI = 0.43 - 2.78) for RT after 2005. To measure the variability of the therapy groups, a stratified risk analysis of risk factors including IDH1/2-mutation-, MGMT-promotor-methylation- and 1p/19q-codeletion-status, extent of resection, initial Karnofsky Performance Score, Ki67-score, age, gender, tumor entity and dose in gray has been performed by using the Kruskal-Wallis test and Fisher-Freeman-Halton test. There has been a significant difference in IDH1/2-mutation- and MGMT-promotor-methylation-status and dose in gray. Single risk analysis of that parameters resulted in superiority of the RT before 2005 over RT/TMZ after 2005 and RT after 2005 regarding the OS.

Conclusion

There have been several limitations in this study, for example the retrospective setting or the missing randomization of the patients. RT before 2005 resulted in the best long-term outcome, what has to be further investigated. However, RT/TMZ after 2005 showed a significant benefit for the OS in the long term vs. RT after 2005, supporting recent findings regarding the role of RT/TMZ in the therapy of WHO grade 3 gliomas.

The Association of Neurosurgeons in the German Democratic Republic and its First Congresses in Divided Germany

The German Society of Neurosurgery (DGNC) was founded in Bonn in 1950 and saw itself as the all-German representation of neurosurgeons. The development of neurosurgery in divided Germany was different in each case as part of a system and was not unaffected by the confrontation between the two blocs (cold war), which also had a negative impact on the field of science. Thus, early on, restrictions on intra-German travel from the East made normal relations difficult. But travel restrictions also came from the West, where an Allied Travel Office in West Berlin decided whether an East German could enter a North Atlantic Treaty Organization (NATO) country. Nevertheless, it was possible that Georg Merrem from Leipzig took over the second chairmanship of the board of the DGNC of the election period from 1960 to 1962 and eight individual memberships of German Democratic Republic (GDR) neurosurgeons were still tolerated by the state side. The construction of the Berlin Wall on August 13, 1961 meant that these connections also collapsed. Merrem, at that time the only full professor of neurosurgery in the GDR, founded the "Association of Neurosurgeons in the GDR" in 1962 in agreement with the state authorities. With the foundation of a GDR neurosurgeons' society, the demarcation from the DGNC desired by the state was visibly accomplished. There were no official relations between the two neurosurgical societies. During the period of its existence until 1990, the entire work of the East German society was under the guidance and control of state institutions, which in turn derived their work from the guidelines of the party and the decisions of the council of ministers. Using the example of the congress activities of the first 5 years after the Wall was built, we show this dependence on state institutions. It extends from congress planning to reporting. With available figures of participating speakers from West Germany and other countries, it is demonstrated for the individual congresses in Leipzig, Magdeburg, and Erfurt that the German-German connection was continued despite all adverse circumstances. The presence of West German colleagues, who were not deterred from attending the congress even by the construction of the Berlin Wall, can be seen as a visible expression of an unbroken togetherness. However, already in 1967, the party and the council of ministers passed the resolution "On the organization of work in the field of science and culture of the GDR to West Germany as well as West Berlin." This regulated membership, the associated travel, and the conditions for publications in West German journals. Among other things, this directive prohibited membership in scientific societies, including the DGNC, based in West Germany. The organization of its own congresses took on a special significance because a congress visit from East to West was regulated by the state and thus only possible in isolated cases.

Microglia/macrophage-derived human CCL18 promotes glioma progression via CCR8-ACP5 axis analyzed in humanized slice model

Factors released from glioma-associated microglia/macrophages (GAMs) play a crucial role in glioblastoma multiforme (GBM) progression. Here, we study the importance of CCL18, a cytokine expressed in human but not in rodent GAMs, as a modulator of glioma growth. Since CCL18 signaling could not be studied in classical mouse glioma models, we developed an approach by transplanting induced pluripotent stem cell-derived human microglia and human glioma cells into mouse brain slices depleted of their intrinsic microglia. We observe that CCL18 promotes glioma cell growth and invasion. Chemokine (C-C motif) receptor 8 (CCR8) is identified as a functional receptor for CCL18 on glioma cells, and ACP5 (acid phosphatase 5) is revealed as an important part of the downstream signaling cascade for mediating glioma growth. We conclude, based on the results from an in vitro, ex vivo humanized glioma model and an in vivo GBM model that microglia/macrophage-derived CCL18 promotes glioma growth.

Differential Diagnosis in Hypophysitis: First Report on a Spindle Cell Rhabdomyosarcoma of the Pituitary Gland

Pituitary gland metastases are very rare. Most patients with pituitary gland metastases are asymptomatic; therefore, most cases of this disease are diagnosed during autopsies. Moreover, the four most common primary tumors that metastasize to the pituitary gland are breast, lung, thyroid, and renal carcinomas. We present a very rare case of pituitary metastasis of spindle cell rhabdomyosarcoma (RMS). Our patient presented with headache, visual disorder, panhypopituitarism, and diabetes insipidus. Due to tumor expansion, resection was not possible, so diagnosis was confirmed by biopsy, and chemotherapy and irradiation were administered. Our patient showed widespread spindle cell RMS, which harbors a mutation of myogenic differentiation 1 (MYOD1) and is associated with a poor prognosis. Even high-risk patients can show a remission after chemotherapy and irradiation. In the cases with indistinct lesions in the sella region, pituitary metastasis should always be considered.

Fetal and perinatal expression profiles of proinflammatory cytokines in the neuroplacodes of rats with myelomeningoceles: A contribution to the understanding of secondary spinal cord injury in open spinal dysraphism

The cellular and molecular mechanisms that presumably underlie the progressive functional decline of the myelomeningocele (MMC) placode are not well understood. We previously identified key players in posttraumatic spinal cord injury cascades in human MMC tissues obtained during postnatal repair. In this study we conducted experiments to further investigate these mediators in the prenatal time course under standardized conditions in a retinoic-acid-induced MMC rat model. A retinoic acid MMC model was established using time-dated Sprague-Dawley rats, which were gavage-fed with all-trans retinoic acid (RA; 60 mg/kg) dissolved in olive oil at E10. Control animals received olive oil only. Fetuses from both groups were obtained at E16, E18, E22. The spinal cords (SCs) of both groups were formalin-fixed or snap-frozen. Tissues were screened by real-time RT-PCR for the expression of cytokines and chemokines known to play a role in the lesion cascades of the central nervous system after trauma. MMC placodes exhibited inflammatory cells and glial activation in the later gestational stages. At the mRNA level, IL-1b, TNFa, and TNF-R1 exhibited significant induction at E22. IL1-R1 mRNA was induced significantly at E16 and E22. Double labeling experiments confirmed the costaining of these cytokines and their receptors with Iba1 (i.e., inflammatory cells), Vimentin, and Nestin in different anatomical SC areas and NeuN in ventral horn neurons. CXCL12 mRNA was elevated in control and MMC animals at E16 compared to E18 and E22. CX3CL1 mRNA was lower in MMC tissues than in control tissues on E16. The presented findings contribute to the concept that pathophysiological mechanisms, such as cytokine induction in the neuroplacode, in addition to the "first hit", promote secondary spinal cord injury with functional loss in the late fetal time course. Furthermore, these mediators should be taken into consideration in the development of new therapeutic approaches for open spinal dysraphism.

P16.05 Implementation of a novel ex-vivo brain slice model to study human glioblastoma and glioma-associated microglia

BACKGROUND

Glioblastoma multiforme is a highly malignant brain tumor with a devastating prognosis. Resection followed by radio-chemotherapy leads to an overall survival of only 15 months. Up to 40% of the tumor mass consist of tumor-associated microglia and macrophages (TAMs). These cells were shown to promote tumor growth and invasiveness in many murine glioma models. The interaction between TAMs and tumor cells is crucial for tumor progression and includes several known pathways. Still, murine glioma models only partially mirror the human tumor microenvironment. Several known genes, which are highly upregulated in human glioma and TAMs are only expressed in human tissue and not in mice. To further investigate some of these genes, we aimed at establishing a humanized ex-vivo brain slice model, in which human TAMs and human glioma cells can be studied in a standardized manner.

MATERIAL AND METHODS

We used 250 micrometer thick murine brain slices, which were depleted of intrinsic microglia by applying clodoronated liposomes. Next, we inoculated human glioma cells (originating from the cell lines mCherryU87, mCherryU251MG, mCherryLN229 and several patient derived cells lines) with or without human microglia derived from induced pluripotent stem cells (iPSCs). Slices were cultivated for 7 to 14 days. Next, we performed a detailed analysis of microglia morphology (sphericity, cell body volume, process length and branching pattern) and tumor volume.

RESULTS

Clodronation efficacy was high, depending on duration of treatment and length of cultivation. iPSCs and tumor cells integrated into the slice very well. The presence of tumor cells led to an increased sphericity of iPSC-dervied microglia and to an increased cell body volume. Branching pattern and process length did not differ between both conditions. Tumor volume was significantly larger when iPSC-derived microglia were present. This was found in various glioma cells lines and also in patient derived cells.

CONCLUSION

The newly established humanized ex-vivo brain slice system was shown to be feasible. The method successfully allows to study the interaction between human TAMs and tumor cells. Microglia foster tumor growth not only in murine glioma models, but also in a human paradigm. The humanized ex-vivo brain slice model therefore is the optimal basis to study the role human-specific genes in TAM-glioma interaction.

Risks and neurological benefits of meningioma surgery in elderly patients compared to young patients

Introduction

While surgery is the primary treatment choice for intracranial meningiomas in young patients, surgery in elderly patients, especially those with pre-existing comorbidities, has been the subject of repeated discussion. This study investigated the postoperative risks and neurological benefits of meningioma surgery in elderly patients compared to young patients.

Methods

In total, 768 patients were included and divided into two main groups: group I (age: ≤ 64 years; 484 young patients) and group II (age: ≥ 65 years; 284 elderly patients). Group II was subdivided into: IIa (age: 65–69 years), IIb (age: 70–79 years); and IIc (age: ≥ 80 years).

Results

The total tumor resection rate was higher in the elderly cohort than in the young cohort (84.5 and 76.2%, respectively). 154 young patients (31.8%) and 132 elderly patients (46.5%) developed postoperative morbidities, with the three most common being bleeding (12.9%), cranial nerve disorder (10%) and CSF fistula (8.1%). Postoperative bleeding, palsy, speech disorder, pneumonia and renal insufficiency were dependent on age (r = 0.123, p = 0.001; r = 0.089, p = 0.014; r = 0.100, p = 0.006; r = 0.098, p = 0.007 and r = 0.084, p = 0.020) and presented more often in elderly patients. 6 young and 15 elderly patients died during the 17.4-year observation period. Most patients showed a significant improvement in postoperative KPS (p < 0.001), except those over 80 years old (p = 0.753). The KPS at the last follow-up was significantly improved in all patients (p < 0.001).

Conclusion

Meningioma surgery is associated with a higher rate of postoperative complications in elderly patients than in young patients. Most elderly patients, similar to young patients, show a significant improvement in neurological status postoperatively.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11060-021-03832-5.

OMRT-1. Cannabidiol converts NFKB into a tumor-suppressor in glioblastoma with defined antioxidative properties

Background

The transcription factor NFKB drives neoplastic progression of many cancers including primary brain tumors (glioblastoma; GBM). Precise therapeutic modulation of NFKB-activity can suppress central oncogenic signalling pathways in GBM, but clinically applicable compounds to achieve this goal have remained elusive.

Methods

In a pharmacogenomics study with a panel of transgenic glioma cells we observed that NFKB can be converted into a tumor-suppressor by the non-psychotropic cannabinoid Cannabidiol (CBD). Subsequently, we investigated the anti-tumor effects of CBD, which is used as an anticonvulsive drug (Epidiolex) in pediatric neurology, in a larger set of human primary GBM stem-like cells (hGSC). For this study we performed pharmacological assays, gene-expression profiling, biochemical and cell-biological experiments. We validated our findings using orthotopic in vivo models and bioinformatics-analysis of human GBM-datasets.

Results

We found that CBD promotes DNA-binding of the NFKB-subunit RELA and simultaneously prevents RELA-phosphorylation on serine-311, a key residue which permits genetic transactivation. Strikingly, sustained DNA-binding by RELA lacking phospho-serine 311 was found to mediate hGSC-cytotoxicity. Widespread sensitivity to CBD was observed in a cohort of hGSC defined by low levels of reactive oxygen-species (ROS), while high ROS-content in other tumors blocked CBD induced hGSC-death. Consequently, ROS-levels served as predictive biomarker for CBD-sensitive tumors.

Conclusions

This evidence demonstrates how a clinically approved drug can convert NFKB into a tumor-suppressor and suggests a promising repurposing option for GBM-therapy.

Influence of Simulated Deep Brain Stimulation on the Expression of Inflammatory Mediators by Human Central Nervous System Cells In Vitro

Deep brain stimulation (DBS) seems to modulate inflammatory processes. Whether this modulation leads to an induction or suppression of inflammatory mediators is still controversially discussed. Most studies of the influence of electrical stimulation on inflammation were conducted in rodent models with direct current stimulation and/or long impulses, both of which differ from the pattern in DBS. This makes comparisons with the clinical condition difficult. We established an in-vitro model that simulated clinical stimulation patterns to investigate the influence of electrical stimulation on proliferation and survival of human astroglial cells, microglia, and differentiated neurons. We also examined its influence on the expression of the inflammatory mediators C-X-C motif chemokine (CXCL)12, CXCL16, CC-chemokin-ligand-2 (CCL)2, CCL20, and interleukin (IL)-1β and IL-6 by these cells using quantitative polymerase chain reaction. In addition, protein expression was assessed by immunofluorescence double staining. In our model, electrical stimulation did not affect proliferation or survival of the examined cell lines. There was a significant upregulation of CXCL12 in the astrocyte cell line SVGA, and of IL-1β in differentiated SH-SY5Y neuronal cells at both messenger RNA and protein levels. Our model allowed a valid examination of chemokines and cytokines associated with inflammation in human brain cells. With it, we detected the induction of inflammatory mediators by electrical stimulation in astrocytes and neurons.

Local progenitor cells shape the neoplastic vasculature and promote brain tumor growth

e14044

Background: Aggressive brain tumors like glioblastoma depend on support by their local environment. While the role of tumor-associated myeloid cells on glioblastoma progression is well-documented, we have only partial knowledge of the pathological impact of glioblastoma -parenchymal progenitor cells. Methods: We investigated the glioblastoma microenvironment with transgenic lineage-tracing models ( nestin-creER2, R26-tdTomato and sox2-creER2,R26-tdTomato), intravital imaging, single-cell transcriptomics, immunofluorescence and flow-cytometry as well as histopathology and characterized a previously unknown tumor-associated progenitor cell. In functional experiments, we studied the knockout of the transcription factor SOX2 in these tumor-associated cells. Results: Lineage-traced cells from mouse glioblastoma were obtained by flow-cytometry and single cell transcriptomes compared to established gene expression data from brain tumor parenchymal cells. The traced tumor-associated cells had a transcriptomic profile largely resembling myeloid cells and expressed microglia-/macrophage-markers on the protein-level. However, transgenic models and bone-marrow chimera revealed that the traced cells were clearly distinct from microglia or macrophages. The traced tumor associated cells with a myeloid expression profile derived from a SOX2-dependent progenitor cell. Consequently, conditional Sox2-knockout ablated the entire myeloid-like cell population. Remarkably, this tumor-associated cell population had a large impact on disease-progression causing significant reduction of glioblastoma –vascularization to 53%, changing vascular function and leading to a decrease in tumor volume to 42% as compared to controls. The myeloid-like progenitor cells were identified in human brain tumors by immunofluorescence and in scRNA-seq data. Conclusions: We identified a previously unacknowledged population of tumor-associated progenitor cells with a myeloid-like expression profile that transiently appeared during glioblastoma growth. These progenitors have strong impact on glioblastoma progression and point towards a new and promising therapeutic target in order to support anti-angiogenic regimen in glioblastoma.

Cannabidiol converts NFκB into a tumor suppressor in glioblastoma with defined antioxidative properties

Background

The transcription factor NF-κB drives neoplastic progression of many cancers including primary brain tumors (glioblastoma [GBM]). Precise therapeutic modulation of NF-κB activity can suppress central oncogenic signaling pathways in GBM, but clinically applicable compounds to achieve this goal have remained elusive.

Methods

In a pharmacogenomics study with a panel of transgenic glioma cells, we observed that NF-κB can be converted into a tumor suppressor by the non-psychotropic cannabinoid cannabidiol (CBD). Subsequently, we investigated the anti-tumor effects of CBD, which is used as an anticonvulsive drug (Epidiolex) in pediatric neurology, in a larger set of human primary GBM stem-like cells (hGSC). For this study, we performed pharmacological assays, gene expression profiling, biochemical, and cell-biological experiments. We validated our findings using orthotopic in vivo models and bioinformatics analysis of human GBM datasets.

Results

We found that CBD promotes DNA binding of the NF-κB subunit RELA and simultaneously prevents RELA phosphorylation on serine-311, a key residue that permits genetic transactivation. Strikingly, sustained DNA binding by RELA-lacking phospho-serine 311 was found to mediate hGSC cytotoxicity. Widespread sensitivity to CBD was observed in a cohort of hGSC defined by low levels of reactive oxygen species (ROS), while high ROS content in other tumors blocked CBD-induced hGSC death. Consequently, ROS levels served as a predictive biomarker for CBD-sensitive tumors.

Conclusions

This evidence demonstrates how a clinically approved drug can convert NF-κB into a tumor suppressor and suggests a promising repurposing option for GBM therapy.

Effects of the Anti-Tumorigenic Agent AT101 on Human Glioblastoma Cells in the Microenvironmental Glioma Stem Cell Niche

Glioblastoma (GBM) is a barely treatable disease due to its profound chemoresistance. A distinct inter- and intratumoral heterogeneity reflected by specialized microenvironmental niches and different tumor cell subpopulations allows GBMs to evade therapy regimens. Thus, there is an urgent need to develop alternative treatment strategies. A promising candidate for the treatment of GBMs is AT101, the R(-) enantiomer of gossypol. The present study evaluates the effects of AT101, alone or in combination with temozolomide (TMZ), in a microenvironmental glioma stem cell niche model of two GBM cell lines (U251MG and U87MG). AT101 was found to induce strong cytotoxic effects on U251MG and U87MG stem-like cells in comparison to the respective native cells. Moreover, a higher sensitivity against treatment with AT101 was observed upon incubation of native cells with a stem-like cell-conditioned medium. This higher sensitivity was reflected by a specific inhibitory influence on the p-p42/44 signaling pathway. Further, the expression of CXCR7 and the interleukin-6 receptor was significantly regulated upon these stimulatory conditions. Since tumor stem-like cells are known to mediate the development of tumor recurrences and were observed to strongly respond to the AT101 treatment, this might represent a promising approach to prevent the development of GBM recurrences.

Erroneous expression of NKG2D on granulocytes detected by phycoerythrin-conjugated clone 149810 antibody

BACKGROUND

The activating Natural killer group 2 member D (NKG2D) receptor is typically expressed on NK cells, CD8 T lymphocytes, γδ T cells and small subsets of CD4 T lymphocytes. During the course of an extensive flow cytometry phenotyping of immune cells in the peripheral blood of patients with glioblastoma multiforme (GBM) we noticed an unexpected expression of NKG2D receptor on granulocytes using the phycoerythrin (PE)-conjugated clone 149810 antibody.

METHODS

Peripheral blood samples from 35 patients with GBM and 22 age-matched healthy control (HC) donors were analyzed using flow cytometry, imaging cytometry and real-time quantitative reverse transcription PCR to validate the observed expression of NKG2D receptor on myeloid cells.

RESULTS

Reactivity with PE-149810 was mostly observed on granulocytes from GBM patients on dexamethasone treatment where it correlated with inferior survival rates. Surprisingly, such NKG2D expression on granulocytes was not observed using the allophycocyanin (APC)-conjugate of the same clone 149810 antibody or an indirect staining procedure with unconjugated clone 149810 antibody. Moreover, the PE-conjugate of a different anti-NKG2D clone (1D11) also did not stain granulocytes. Imaging cytometry indicated cell surface and intracellular localization of PE-149810 but not of PE-1D11 in granulocytes.

CONCLUSION

Our results uncover an erroneous and false positive reactivity of PE-labeled (but not of APC-labeled or unconjugated) anti-NKG2D antibody 149810 on granulocytes from dexamethasone-treated GBM patients and raise a note of caution for studies of NKG2D expression on non-lymphoid cells.

Can Deep Brain Stimulation Withdrawal Syndromes Be Avoided by Removing Infected Implanted Pulse Generator and Cables with Contralateral Replacement in the Same Session?

OBJECTIVE

Infections are feared complications following deep brain stimulation in 1.9 to 17.6% of cases. These infections can necessitate the removal of implants, which carries the risk of life-threatening withdrawal syndromes, especially in patients suffering from Parkinson's disease. In this report, we describe our procedure of removing an infected implanted pulse generator (IPG) and cables with contralateral replacement in the same session.

METHODS

We retrospectively analysed all patients with transpositions of an IPG and cables between 2017 and 2020 in a single-centre, university hospital setting. Medical records of all patients undergoing this particular surgical procedure were systematically reviewed. The shortest follow-up time was 12 months.

RESULTS

Between 2017 and 2020, we had 6 patients with a high risk of withdrawal syndrome in whom an infected IPG with cables was removed and replaced on the opposite side in the same session. There were postoperative complications in 2 patients: in one, the generator had to be re-affixed, and in the second, a skin transplant was required over one electrode because of skin necrosis. No case of invasive infection was seen, and the stimulation therapy was not interrupted.

CONCLUSION

One-session removal of an IPG and cables with contralateral replacement seems to be an effective therapy for patients at high risk of withdrawal syndrome.

TAMEP are brain tumor parenchymal cells controlling neoplastic angiogenesis and progression

Aggressive brain tumors like glioblastoma depend on support by their local environment and subsets of tumor parenchymal cells may promote specific phases of disease progression. We investigated the glioblastoma microenvironment with transgenic lineage-tracing models, intravital imaging, single-cell transcriptomics, immunofluorescence analysis as well as histopathology and characterized a previously unacknowledged population of tumor-associated cells with a myeloid-like expression profile (TAMEP) that transiently appeared during glioblastoma growth. TAMEP of mice and humans were identified with specific markers. Notably, TAMEP did not derive from microglia or peripheral monocytes but were generated by a fraction of CNS-resident, SOX2-positive progenitors. Abrogation of this progenitor cell population, by conditional Sox2-knockout, drastically reduced glioblastoma vascularization and size. Hence, TAMEP emerge as a tumor parenchymal component with a strong impact on glioblastoma progression.

Evaluation of a Brown Seaweed Extract from Dictyosiphon foeniculaceus as a Potential Therapeutic Agent for the Treatment of Glioblastoma and Uveal Melanoma

Ingredients of brown seaweed like fucoidans are often described for their beneficial biological effects, that might be interesting for a medical application. In this study, we tested an extract from Dictyosiphon foeniculaceus (DF) to evaluate the effects in glioblastoma and uveal melanoma, looking for a possible anti-cancer treatment. We investigated toxicity, VEGF (vascular endothelial growth factor) secretion and gene expression of tumor and non-tumor cells. SVGA (human fetal astrocytes), the human RPE (retinal pigment epithelium) cell line ARPE-19, the tumor cell line OMM-1 (human uveal melanoma), and two different human primary glioblastoma cultures (116-14 and 118-14) were used. Tests for cell viability were conducted with MTS-Assay (3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium), and the proliferation rate was determined with cell counting. VEGF secretion was assessed with ELISA (enzyme-linked immunosorbent assay). The gene expression of VEGF receptor 1 (VEGFR1), VEGF receptor 2 (VEGFR2) and VEGF-A was determined with real-time qPCR (quantitative polymerase chain reaction). DF lowered the cell viability of OMM-1. Proliferation rates of ARPE-19 and OMM-1 were decreased. The VEGF secretion was inhibited in ARPE-19 and OMM-1, whereas it was increased in SVGA and 116-14. The expression of VEGFR1 was absent and not influenced in OMM-1 and ARPE-19. VEGFR2 expression was lowered in 116-14 after 24 h, whereas VEGF-A was increased in 118-14 after 72 h. The extract lowered cell viability slightly and was anti-proliferative depending on the cell type investigated. VEGF was heterogeneously affected. The results in glioblastoma were not promising, but the anti-tumor properties in OMM-1 could make them interesting for further research concerning cancer diseases in the human eye.

AT101-Loaded Cubosomes as an Alternative for Improved Glioblastoma Therapy

Introduction

AT101, the R-(-)-enantiomer of the cottonseed-derived polyphenol gossypol, is a promising drug in glioblastoma multiforme (GBM) therapy due to its ability to trigger autophagic cell death but also to facilitate apoptosis in tumor cells. It does have some limitations such as poor solubility in water-based media and consequent low bioavailability, which affect its response rate during treatment. To overcome this drawback and to improve the anti-cancer potential of AT101, the use of cubosome-based formulation for AT101 drug delivery has been proposed. This is the first report on the use of cubosomes as AT101 drug carriers in GBM cells.

Materials and Methods

Cubosomes loaded with AT101 were prepared from glyceryl monooleate (GMO) and the surfactant Pluronic F-127 using the top-down approach. The drug was introduced into the lipid prior to dispersion. Prepared formulations were then subjected to complex physicochemical and biological characterization.

Results

Formulations of AT101-loaded cubosomes were highly stable colloids with a high drug entrapment efficiency (97.7%) and a continuous, sustained drug release approaching 35% over 72 h. Using selective and sensitive NMR diffusometry, the drug was shown to be efficiently bound to the lipid-based cubosomes. In vitro imaging studies showed the high efficiency of cubosomal nanoparticles uptake into GBM cells, as well as their marked ability to penetrate into tumor spheroids. Treatment of GBM cells with the AT101-loaded cubosomes, but not with the free drug, induced cytoskeletal rearrangement and shortening of actin fibers. The prepared nanoparticles revealed stronger in vitro cytotoxic effects against GBM cells (A172 and LN229 cell lines), than against normal brain cells (SVGA and HMC3 cell lines).

Conclusion

The results indicate that GMO-AT101 cubosome formulations are a promising basic tool for alternative approaches to GBM treatment.

Surgery for Diffuse WHO Grade II Gliomas: Volumetric Analysis of a Multicenter Retrospective Cohort From the German Study Group for Intraoperative Magnetic Resonance Imaging

BACKGROUND

In diffuse WHO grade II gliomas (LGG), the extent of resection (EOR) required to achieve significant survival benefits remains elusive.

OBJECTIVE

To evaluate the association of residual volume (RV) and EOR with progression-free survival (PFS) or overall survival (OS) in LGG in a retrospective, multicenter series by the German study group of intraoperative MRI (GeSGIM).

METHODS

Consecutive cases were retrospectively assessed from 5 centers. Tumors were volumetrically quantified before and after surgery, and clinical data were analyzed, including IDH mutations and neurologic deficits. Kaplan-Meier estimates, accelerated failure time models (AFT), and multivariate Cox regression models were calculated to identify determinants of survival.

RESULTS

A total of 140 cases were analyzed. Gross total resection (GTR) was associated with significantly longer PFS compared to any incomplete resection (P = .009). A significant survival disadvantage was evident even for small (>0-5 ml) residuals and increased for moderate (>5-20 ml) and large remnants (>20 ml) P = .001). Accordingly, PFS increased continuously for 20% incremental steps of EOR (P < .001). AFT models supported the notion of a continuous association of RV and EOR with PFS. Multivariate Cox regression models confirmed RV (P = .01) and EOR (P = .005) as continuous prognosticators of PFS. Univariate analysis showed significant associations of RV and EOR with OS.

CONCLUSION

Our data support the hypothesis of a continuous relationship of RV and EOR with survival for LGG with superiority seen for GTR. Hence, GTR should be achieved whenever safely feasible, and resections should be maximized whenever tumor has to be left behind to spare function.

Correction: CD95 maintains stem cell-like and non-classical EMT programs in primary human glioblastoma cells

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

Purpose

Circumferential enhancement on MR vessel wall imaging has been proposed as a biomarker of a higher risk of rupture in intracranial aneurysms. Focal enhancement is frequently encountered in unruptured aneurysms, but its implication for risk stratification and patient management remains unclear. This study investigates the association of focal wall enhancement with hemodynamic and morphological risk factors and histologic markers of wall inflammation and degeneration.

Methods

Patients with an unruptured middle cerebral artery aneurysm who underwent 3D rotational angiography and 3T MR vessel wall imaging showing focal wall enhancement were included. Hemodynamic parameters were calculated based on flow simulations and compared between enhanced regions and the entire aneurysm surface. Morphological parameters were semiautomatically extracted and quantitatively associated with wall enhancement. Histological analysis included detection of vasa vasorum, CD34, and myeloperoxidase staining in a subset of patients.

Results

Twenty-two aneurysms were analyzed. Enhanced regions were significantly associated with lower AWSS, lower maxOSI, and increased LSA. In multivariate analysis, higher ellipticity index was an independent predictor of wall enhancement. Histologic signs of inflammation and degeneration and higher PHASES score were significantly associated with focal enhancement.

Conclusion

Focal wall enhancement is colocalized with hemodynamic factors that have been related to a higher rupture risk. It is correlated with morphological factors linked to rupture risk, higher PHASES score, and histologic markers of wall destabilization. The results support the hypothesis that focal enhancement could serve as a surrogate marker for aneurysm instability.

O-Vanillin Attenuates the TLR2 Mediated Tumor-Promoting Phenotype of Microglia

Malignant gliomas are primary brain tumors with poor prognoses. These tumors are infiltrated by brain intrinsic microglia and peripheral monocytes which promote glioma cell invasion. In our previous studies, we discovered that the activation of Toll-like receptor 2 (TLR2) on microglia/brain macrophages converts them into a protumorigenic phenotype through the induction of matrix metalloproteinases (MMP) 9 and 14. In the present study, we used in vitro and in situ microglia-glioma interaction experimental models to test the impact of a novel inhibitor of TLR 2, ortho vanillin (O-Vanillin) to block TLR2 mediated microglia protumorigenic phenotype. We demonstrate that O-Vanillin inhibits the TLR2 mediated upregulation of MMP 9, MMP 14, IL 6 and iNOS expression. Similarly, the glioma supernatant induced MMP 9 and MMP 14 expression in murine and human microglia is abrogated by O-Vanillin treatment. O-Vanillin is not toxic for microglia, astrocytes or oligodendrocytes. Glioma growth in murine brain slice cultures is significantly reduced after treatment with O-Vanillin, and this reduced glioma growth depends on the presence of microglia. In addition, we also found that O-Vanillin inhibited the glioma induced proliferation of murine primary microglia. In summary, O-Vanillin attenuates the pro-tumorigenic phenotype of microglia/brain macrophages and thus qualifies as a candidate for glioma therapy.

ETV in infancy and childhood below 2 years of age for treatment of hydrocephalus

PURPOSE

Age and etiology play a crucial role in success of endoscopic third ventriculostomy (ETV) as a treatment of obstructive hydrocephalus. Outcome is worse in infants, and controversies still exist whether ETV is superior to shunt placement. We retrospectively analyzed 70 patients below 2 years from 4 different centers treated with ETV and assessed success.

METHODS

Children < 2 years who received an ETV within 1994-2018 were included. Patients were classified according to age and etiology; < 3, 4-12, and 13-24 months, etiologically; aqueductal stenosis, post-hemorrhagic-hydrocephalus (PHH), tumor-related, fourth ventricle outflow obstruction, with Chiari-type II and following CSF infection. We investigated statistically the predictors for ETV success through computing Kaplan-Meier estimates using patient's follow-up time and time to ETV failure.

RESULTS

We collected 70 patients. ETV success rate was 41.4%. The highest rate was in tumor-related hydrocephalus and fourth ventricle outlet obstruction (62.5%, 60%) and the lowest rate was in Chiari-type II and following infection (16.7%, 0%). The below 3 months age group showed relatively lower success rate (33.3%) in comparison to older groups which showed similar results (46.4%, 46.6%). Statistically, a previous VP shunt was a predictor for failure (p value < 0.05).

CONCLUSION

Factors suggesting a high possibility of failure were age < 3 months and etiology such as Chiari-type II or following infection. Altered CSF dynamics in patients with PHH and under-developed arachnoid villi may play a role in ETV failure. We do not recommend ETV as first line in children < 3 months of age or in case of Chiari II or following infection.

Dormancy and NKG2D system in brain metastases: Analysis of immunogenicity

Patients with breast cancer (BC) and lung cancer (LC) are prone to developing brain metastases, which are associated with devastating prognoses. Dormant tumor cells, a population of non-apoptotic quiescent cells and immunological escape mechanisms, including the Natural Killer Group 2 member D (NKG2D) receptor-ligand system, represent potential mechanisms of tumor recurrence. To date, the immunological characteristics of dormant tumor cells concerning the NKG2D system in cerebral malignancies are mostly unknown. In the present study, an extensive characterization of dormant and NKG2D ligand (NKG2DL)⁺ cells in cerebral metastases was performed. The expression profiles and localization patterns of various NKG2DL and several dormancy markers were analyzed in solid human brain metastases from patients with BC and LC using immunostaining and reverse transcription-quantitative polymerase chain reaction analyses. Statistical analysis was performed using Student's t-test and Bravais-Pearson correlation analysis. Not only 'peripheral', but also 'central' dormancy markers, which had been previously described in primary brain tumors, were identified in all cerebral metastases at detectable levels at protein and mRNA levels. Notably, the majority of NKG2DL⁺ cells were also positive for 'central' dormancy markers, but not 'peripheral' dormancy markers in both patient groups. This cell population may represent a promising future therapeutic target.

Combined treatment of AT101 and demethoxycurcumin yields an enhanced anti-proliferative effect in human primary glioblastoma cells

PURPOSE

Glioblastoma multiforme (GBM) is a poorly curable disease due to its profound chemoresistance. Despite recent advances in surgery, radiotherapy and chemotherapy, the efficient treatment of GBMs is still a clinical challenge. Beside others, AT101, the R-(-) enantiomer of gossypol, and demethoxycurcumin (DMC), a curcumin-related demethoxy compound derived from Curcuma longa, were considered as possible alternative drugs for GBM therapy.

METHODS

Using different human primary GBM cell cultures in a long-term stimulation in vitro model, the cytotoxic and anti-proliferative effects of single and combined treatment with 5 µM AT101 and 5 µM or 10 µM DMC were investigated. Furthermore, western blots on pAkt and pp44/42 as well as JC-1 staining and real-time RT-PCR were performed to understand the influence of the treatment at the molecular and gene level.

RESULTS

Due to enhanced anti-proliferative effects, we showed that combined therapy with both drugs was superior to a single treatment with AT101 or DMC. Here, by determination of the combination index, a synergism of the combined drugs was detectable. Phosphorylation and thereby activation of the kinases p44/42 and Akt, which are involved in proliferation and survival processes, were inhibited, the mitochondrial membrane potential of the GBM cells was altered, and genes involved in dormancy-associated processes were regulated by the combined treatment strategy.

CONCLUSION

Combined treatment with different drugs might be an option to efficiently overcome chemoresistance of GBM cells in a long-term treatment strategy.

ANGI-03. PHARMACOLOGICAL TARGETING OF APELIN/APLNR SIGNALING BLUNTS THERAPY RESISTANCE TO VEGFA/VEGFR2 ANTI-ANGIOGENIC TREATMENT IN GLIOBLASTOMA

Anti-angiogenic therapy of glioblastoma with bevacizumab, a vascular endothelial growth factor-A (VEGFA) blocking antibody, may accelerate tumor cell invasion and induce alternative angiogenic pathways. We investigated the roles of the pro-angiogenic receptor APLNR and its cognate ligand apelin in VEGFA/VEGFR2 anti-angiogenic therapy against distinct subtypes of glioblastoma. In proneural glioblastoma, apelin levels were downregulated by VEGFA or VEGFR2 blockade by use of bevacizumab or ramucirumab, respectively. A central role for apelin/APLNR in controlling glioblastoma vascularization was corroborated in a serial implantation model of the angiogenic switch that occurs in human glioblastoma. Apelin and APLNR are broadly expressed in human glioblastoma, and knockdown or knockout of APLN in orthotopic models of proneural or classical glioblastoma subtypes massively reduced glioblastoma vascularization as compared with controls. What is more, direct infusion of the bioactive peptide apelin-13 was able to rescue this vascular loss-of-function phenotype, demonstrating the specific control of tumor vascularization by apelin/APLNR signaling. While high levels of apelin correlated with reduced tumor cell invasiveness, the reduction in apelin expression led to accelerated glioblastoma cell invasion. Analysis of stereotactic glioblastoma biopsies from patients as well as from in vitro and in vivo experiments revealed increased dissemination of APLNR-positive tumor cells when apelin levels were reduced. Most interestingly, application of apelin-F13A, a mutant APLNR ligand, blocked both tumor angiogenesis and glioblastoma cell invasion. Furthermore, co-targeting VEGFR2 and APLNR synergistically improved survival of mice bearing proneural glioblastoma. In summary, we show that apelin/APLNR signaling controls glioblastoma angiogenesis and invasion directly, and that both pathological features are blunted by apelin-F13A. We suggest that apelin-F13A can improve the efficiency and reduce the side effects of established anti-angiogenic treatments for distinct glioblastoma subtypes.

DDIS-35. RelA-ACTIVITY IS ESSENTIAL FOR CANNABIDIOL-MEDIATED CYTOTOXICITY IN AN IDENTIFIED SUBSET OF GLIOBLASTOMA

Glioblastoma (GBM) therapy could strongly profit from simplified procedures for personalized medicine. Cannabidiol (CBD) is explored for GBM-patients, but the mode of drug-action is largely unknown and stratification markers are missing. We investigated CBD-induced cytotoxicity in a panel of human primary GBM cells as well as transgenic mouse gliomas and in different orthotopic or transgenic in vivo models. We observed therapeutic efficiency of CBD in a subset of GBM, obtained genetic markers indicating CBD-sensitive GBM and found that the p53 status segregated cell-death modes. Genome wide loss of function screening, transcription factor binding studies and knockout-models indicated a central for role for NFkB (RelA) in CBD-initiated GBM-death. CBD mediated nuclear import of RelA lacking an essential post-translational modification and reduced RelA-activity. CBD altered redox levels specifically in drug-sensitive GBM and ROS-levels in unstimulated GBM predicted therapeutic response. Hence, quantifying ROS in GBM represents a simple bioassay to identify individuals potentially profiting from CBD-application in neurooncology.

TMIC-30. MICROGLIA/BRAIN MACROPHAGES PROMOTE GLIOMA GROWTH BY EXPRESSING GLYCOPROTEIN NMB

BACKGROUND

Glioma-associated microglia and blood-derived macrophages (GAMs) promote tumor growth in experimental mouse glioma models. Using microarray and RNA sequencing, we have previously shown that GAMs upregulate the expression of Glycoprotein NMB/Osteoactivin (GPNMB) when compared to naïve microglia. GPNMB is a type 1 transmembrane glycoprotein expressed intracellularly under healthy conditions. Malignancies such as glioma induce a translocation into the plasma membrane where the extracellular domain can be cleaved and released.

METHODS

We used qRT-PCR, immunocytochemistry, Western Blot and flow cytometry to determine the cellular localization of GPNMB expression in human and mouse glioblastoma. To test the impact of microenvironment-derived GPNMB on glioma growth, we inoculated GL261 and RCAS-PDGFb glioblastoma cells into organotypic brain slices obtained from wildtype and GPNMB-/- mice. In addition, we quantified glioma growth after injection of RCAS-PDGFb cells into wildtype and GPNMB-/- mice. The soluble extracellular domain of GPNMB was used to stimulate primary human glioblastoma and RCAS-PDGFb cells in vitro. SRB assays were performed to assess proliferation.

RESULTS

Our data indicate that GAMs are the predominant source of GPNMB in both human and mouse glioblastoma and that the levels of expression in GAMs in the tumor microenvironment is higher than in naïve microglia. In the organotypic brain slice model we found that tumors were significantly smaller in slices derived from GPNMB-/- mice as compared to wildtype. The tumor growth in vivo was nearly completely blocked in the absence of GPNMB. Stimulation of glioma cells with the extracellular domain of GPNMB did not increase proliferation.

CONCLUSION

Our results show that GPNMB is predominantly expressed in GAMs of human and murine samples. Loss of GPNMB impaired tumor growth ex vivo and glioblastoma progression in vivo. GPNMB seems to play a crucial role in the pro-tumorigenic activity of microglia and blood-derived macrophages in the tumor microenvironment.

P10.05 NKG2DL expression and dormancy in cerebral metastases: impact of chemotherapeutic treatment

Background: Cerebral metastases are common intracranial lesions and have enormous prognostic impact. In many cases, brain metastases seem to be insensitive to chemotherapeutic treatment and are often source of recurrence. To date, the reasons for this are not entirely known. Dormant tumor cells are a population of non-apoptotic, low proliferating cells, which have the ability to be reactivated and can be the source of recurrence. Another mechanism of tumor cell survival are immunological escape mechanisms, involving the Natural Killer Group 2, member D (nkg2d) receptor-ligand system. In a previous study we were able to show that human brain metastases of pulmonary and breast cancer harbor a significant amount of dormant tumor cells, which often coexpress NKG2D ligands. We now wanted to investigate, whether chemotherapeutic treatment has an effect on expression of dormancy markers and nkg2d ligands.

Materials and Methods: The murine breast cancer cell line E0771 and the murine pulmonary cancer cell line LLC were treated with ascending doses of cisplatin and cyclophosphamid, two chemotherapeutics which are also used in humans, for 2 to 10 days in comparison to negative controls. We performed a cytotoxicity assay. Expression of the dormancy-associated markers pdgf, fgf2, hif1alpha, epha5, h2bk and igfbp5 and the nkg2d ligands mult1, h60a, h60b, h60c and raet1b were analyzed by qrtPCR and immunocytochemistry (IHC).

Results: Cytotoxicity assay revealed, that cells from both lines died significantly after treatment with Cisplatin in comparison to control conditions. Whereas cyclophosphamide had no effect on dormancy marker and nkg2dl expression, treatment with cisplatin led to a significant upregulation of many nkg2dl and dormancy marker expression in LLC and E0771 in a dose and time dependent manner. Results were confirmed via IHC.Conclusions: Although chemotherapy with cisplatin leads to death of many cells in culture, the surviving cells show a high expression of dormancy markers and of certain nkg2d ligands. Not only acquisition of dormancy but also nkg2d ligand expression might play an important role in chemoresistance of brain metastases. Markers from both groups could therefore be effective therapeutic targets.

A multicenter, open-label, controlled trial on acceptance, convenience, and complications of rechargeable internal pulse generators for deep brain stimulation: the Multi Recharge Trial

OBJECTIVE

Rechargeable neurostimulators for deep brain stimulation have been available since 2008, promising longer battery life and fewer replacement surgeries compared to non-rechargeable systems. Long-term data on how recharging affects movement disorder patients are sparse. This is the first multicenter, patient-focused, industry-independent study on rechargeable neurostimulators.

METHODS

Four neurosurgical centers sent a questionnaire to all adult movement disorder patients with a rechargeable neurostimulator implanted at the time of the trial. The primary endpoint was the convenience of the recharging process rated on an ordinal scale from "very hard" (1) to "very easy" (5). Secondary endpoints were charge burden (time spent per week on recharging), user confidence, and complication rates. Endpoints were compared for several subgroups.

RESULTS

Datasets of 195 movement disorder patients (66.1% of sent questionnaires) with Parkinson's disease (PD), tremor, or dystonia were returned and included in the analysis. Patients had a mean age of 61.3 years and the device was implanted for a mean of 40.3 months. The overall convenience of recharging was rated as "easy" (4). The mean charge burden was 122 min/wk and showed a positive correlation with duration of therapy; 93.8% of users felt confident recharging the device. The rate of surgical revisions was 4.1%, and the infection rate was 2.1%. Failed recharges occurred in 8.7% of patients, and 3.6% of patients experienced an interruption of therapy because of a failed recharge. Convenience ratings by PD patients were significantly worse than ratings by dystonia patients. Caregivers recharged the device for the patient in 12.3% of cases. Patients who switched from a non-rechargeable to a rechargeable neurostimulator found recharging to be significantly less convenient at a higher charge burden than did patients whose primary implant was rechargeable. Age did not have a significant impact on any endpoint.

CONCLUSIONS

Overall, patients with movement disorders rated recharging as easy, with low complication rates and acceptable charge burden.

To treat or not to treat? A retrospective multicenter assessment of survival in patients with IDH-mutant low-grade glioma based on adjuvant treatment

OBJECTIVE

The level of evidence for adjuvant treatment of diffuse WHO grade II glioma (low-grade glioma, LGG) is low. In so-called "high-risk" patients most centers currently apply an early aggressive adjuvant treatment after surgery. The aim of this assessment was to compare progression-free survival (PFS) and overall survival (OS) in patients receiving radiation therapy (RT) alone, chemotherapy (CT) alone, or a combined/consecutive RT+CT, with patients receiving no primary adjuvant treatment after surgery.

METHODS

Based on a retrospective multicenter cohort of 288 patients (≥ 18 years old) with diffuse WHO grade II gliomas, a subgroup analysis of patients with a confirmed isocitrate dehydrogenase (IDH) mutation was performed. The influence of primary adjuvant treatment after surgery on PFS and OS was assessed using Kaplan-Meier estimates and multivariate Cox regression models, including age (≥ 40 years), complete tumor resection (CTR), recurrent surgery, and astrocytoma versus oligodendroglioma.

RESULTS

One hundred forty-four patients matched the inclusion criteria. Forty patients (27.8%) received adjuvant treatment. The median follow-up duration was 6 years (95% confidence interval 4.8-6.3 years). The median overall PFS was 3.9 years and OS 16.1 years. PFS and OS were significantly longer without adjuvant treatment (p = 0.003). A significant difference in favor of no adjuvant therapy was observed even in high-risk patients (age ≥ 40 years or residual tumor, 3.9 vs 3.1 years, p = 0.025). In the multivariate model (controlled for age, CTR, oligodendroglial diagnosis, and recurrent surgery), patients who received no adjuvant therapy showed a significantly positive influence on PFS (p = 0.030) and OS (p = 0.009) compared to any other adjuvant treatment regimen. This effect was most pronounced if RT+CT was applied (p = 0.004, hazard ratio [HR] 2.7 for PFS, and p = 0.001, HR 20.2 for OS). CTR was independently associated with longer PFS (p = 0.019). Age ≥ 40 years, histopathological diagnosis, and recurrence did not achieve statistical significance.

CONCLUSIONS

In this series of IDH-mutated LGGs, adjuvant treatment with RT, CT with temozolomide (TMZ), or the combination of both showed no significant advantage in terms of PFS and OS. Even in high-risk patients, the authors observed a similar significantly negative impact of adjuvant treatment on PFS and OS. These results underscore the importance of a CTR in LGG. Whether patients ≥ 40 years old should receive adjuvant treatment despite a CTR should be a matter of debate. A potential tumor dedifferentiation by administration of early TMZ, RT, or RT+CT in IDH-mutated LGG should be considered. However, these data are limited by the retrospective study design and the potentially heterogeneous indication for adjuvant treatment.