CNS Malignancies Research Articles

Single-cell analysis reveals diversity of tumor-associated macrophages and their interactions with T lymphocytes in glioblastoma

Glioblastoma (GBM) is an aggressive primary CNS malignancy and clinical outcomes have remained stagnant despite introduction of new treatments. Understanding the tumor microenvironment (TME) in which tumor associated macrophages (TAMs) interact with T cells has been of great interest. Although previous studies examining TAMs in GBM have shown that certain TAMs are associated with specific clinical and/or pathologic features, these studies used an outdated M1/M2 paradigm of macrophage polarization and failed to include the continuum of TAM states in GBM. Perhaps most significantly, the interactions of TAMs with T cells have yet to be fully explored. Our study uses single-cell RNA sequencing data from adult IDH-wildtype GBM, with the primary aim of deciphering the cellular interactions of the 7 TAM subtypes with T cells in the GBM TME. Furthermore, the interactions discovered herein are compared to IDH-mutant astrocytoma, allowing for focus on the cellular ecosystem unique to GBM. The resulting ligand-receptor interactions, signaling sources, and global communication patterns discovered provide a framework for future studies to explore methods of leveraging the immune system for treating GBM.

Revealing Pan-Histology Immunomodulatory Targets in Pediatric Central Nervous System Tumors.

The application of immunotherapy for pediatric CNS malignancies has been limited by the poorly understood immune landscape in this context. The aim of this study was to uncover the mechanisms of immune suppression common among pediatric brain tumors. We apply an immunologic clustering algorithm validated by The Cancer Genome Atlas Project to an independent pediatric CNS transcriptomic dataset. Within the clusters, the mechanisms of immunosuppression are explored via tumor microenvironment deconvolution and survival analyses to identify relevant immunosuppressive genes with translational relevance. High-grade diseases fall predominantly within an immunosuppressive subtype (C4) that independently lowers overall survival time and where common immune checkpoints (e.g., PDL1, CTLA4) are less relevant. Instead, we identify several alternative immunomodulatory targets with relevance across histologic diseases. Specifically, we show how the mechanism of EZH2 inhibition to enhance tumor immunogenicity in vitro via the upregulation of MHC class 1 is applicable to a pediatric CNS oncologic context. Meanwhile, we identify that the C3 (inflammatory) immune subtype is more common in low-grade diseases and find that immune checkpoint inhibition may be an effective way to curb progression for this subset. Three predominant immunologic clusters are identified across pediatric brain tumors. Among high-risk diseases, the predominant immune cluster is associated with recurrent immunomodulatory genes that influence immune infiltrate, including a subset that impacts survival across histologies.

DDEL-08. THE OMMAYA IN LEPTOMENINGEAL DISEASE AND CENTRAL NERVOUS SYSTEM MALIGNANCIES: A RESERVOIR OF THE PAST OR SOURCE OF THE FUTURE?

Abstract Advances in systemic therapies have increased survival in patients with metastatic cancer. However, such prolonged survival has been associated with increased incidence of leptomeningeal disease (LMD), a late-stage manifestation of cancer to the leptomeninges that carries a dismal prognosis. Circumvention of the blood-brain-barrier to treat LMD can be accomplished with intraventricular therapy using an Ommaya reservoir. Our objective is to determine the indications, efficacy, and future directions of the Ommaya reservoir in LMD and CNS malignancies. A systematic review of the literature was conducted. Data extracted from articles included year of publication, study design, cancer types, and findings. The search query returned 5,338 articles, of which 94 were included. Most articles (45, 47.9%) were prospective cohort studies. Forty-one (43.6%) described retrospective chart reviews, and five (5.3%) described RCTs. Ommaya was studied as a vehicle for intrathecal chemotherapy administration (76, 80.9%), an access site for CSF sampling (12, 12.8%), or a device through which to study dosimetry and pharmacokinetics of various drugs (5, 5.3%). Most studies (50, 53.2%) explored the use of Ommaya in LMD, secondary to any cancer (62%), breast cancer (20%), lung cancer (6%), glioma (6%), lymphoma (4%), and melanoma (2%). Sixteen articles (17%) focused on the use of Ommaya in malignant glioma, 11 studies (11.7%) in CNS lymphoma, and three (3, 3.2%) evaluated the efficacy of intraventricular morphine for intractable cancer pain. Since 2011, 24 studies (64.9%) reported positive outcomes with Ommaya, and two (5.4%) did not. The literature indicates that the Ommaya is a safe and reliable option for treatment of certain malignancies and LMD. The benefit appears to be most marked in the era of multi-modality treatment for cancer, particularly breast. Most recently, and perhaps most promising, is utilization of Ommaya for CSF analysis, both in tracking therapeutic response and defining pharmacokinetics in patients with LMD.

IMMU-36. PD-1KO HEMATOPOIETIC STEM CELLS RAPIDLY DIFFERENTIATE INTO GLIOMA-INFILTRATING EFFECTOR T-CELLS

Abstract INTRODUCTION We previously published that hematopoietic stem cell combination therapy (HSC+aPD1) extends survival in murine CNS malignancies, including glioma. To better understand lymphoid-specific mechanisms, we analyzed various lymphoid tissues in a murine glioma model. We hypothesize early PD-1 blockade in HSCs influences later differentiation trajectories. Transferred HSCs differentiate into T-cells within the thymus and then migrate to the intracranial tumor microenvironment as anticipated. Indeed, blocking PD-1/PD-L1 signaling during HSC differentiation significantly impacts subsequent T-cell maturation. Remarkably, TILs derived from HSCPD1KO cells were biased towards CD4+ Treg or CD8+ effector lineages, whereas HSCPD1+/+ progeny leaned toward immature/naïve cell states. METHODS HSCs were prepared from constitutive GFP-expressing (CD45.2+) and PD1KO (CD45.2+) mice and transferred into CD45.1+ hosts. Sublethal 5Gy total body irradiation was administered day 5 post-intracranial tumor implantation. The next day, 1e6 HSCs from a 1:1-GFP:PD1KO cocktail were injected intravenously. Descriptive statistics are reported as mean ± SD. Transferred HSCs engraft, expand, differentiate, tended and migrate to form approximately 25% of the TIL compartment in only 15 days. RESULTS We found that, 56.2% ± 20.3 of CD3+ TILs display an immature CD4+CD8+ (DP) phenotype in early disease, and 43.8% ± 17.4 of these DP-TILs are HSC-derived. DP-TILs were virtually absent in advanced disease 29 days after treatment, but HSC-derived TILs most commonly fell within the single-positive (SP) TIL subsets, comprising 9.8% ± 5.6 of SP-CD8+ TILs. Notably, HSCPD1KO-derived cells were 4x more abundant amongst SP-CD8 TILs when compared to HSCGFP-derived cells (6.5% vs 1.6%, p < 0.05). SP-CD8 thymocytes were similarly enriched for HSCPD1KO progeny (41.1% vs 24.7%, p < 0.05) suggesting that PD-1 blockade impacts thymopoiesis directly. CONCLUSION PD-1 signaling modulates thymic output. Blocking the PD-1/PD-L1 axis during thymopoiesis increases the abundance of HSC-derived CD8+ effectors at the tumor site. HSC+aPD1 therapy is uniquely positioned to leverage thymus-dependent anti-tumor immunity.

NIMG-89. CNS-ISOLATED RICHTER’S TRANSFORMATION: THE FALLIBILITY OF NEURO-IMAGING AND THE CRITICAL ROLE OF BRAIN BIOPSY IN A CHALLENGING DIAGNOSIS

Abstract INTRODUCTION An 81-year-old male was admitted for acute encephalopathy and failure to thrive. Workup revealed a lymphocyte-predominant leukocytosis, prominent axillary and mediastinal lymphadenopathy on CT, and multiple supra-tentorial FLAIR-hyperintense lesions that were homogenously contrast-enhancing. Axillary lymph node biopsy demonstrated small lymphocytic lymphoma (SLL), a variant of CLL. Despite concern for CNS malignancy, brain biopsy was initially deferred since the patient’s brain lesions were attributed to SLL metastasis. However on hospital day 15, he developed partial seizures, prompting stereotactic biopsy which revealed DLBCL. DATA/DISCUSSION Our case highlights the pitfalls of relying solely upon neuro-imaging to diagnose Richter’s transformation (RT) isolated to the CNS. First, MRI does not differentiate CNS metastasis of systemic lymphoma from CNS RT. A review of 35 biopsy or LP-proven cases of CNS-isolated RT showed imaging characteristics consistent with primary and metastatic CNS lymphoma. When parenchymal lesions are present, all are T2/FLAIR hyper-intense; 60% are unifocal (40% multifocal); and 95% homogenously enhance. Second, CNS-isolated RT is at least 3 times rarer than CNS metastases of CLL. Among patients with CLL, ~1% will eventually exhibit CNS metastasis but < 0.3% will develop CNS-isolated RT. In patients with known CLL and no evidence of high-grade transformation, it is reasonable to attribute brain lesions to CNS metastasis of CLL as opposed to RT, absent a definitive tissue diagnosis. CONCLUSION These data emphasize the importance of biopsy in the workup of CNS lymphoma, especially since treatment differs based on histopathological subtype. Given its chronic indolent course, SLL is typically managed expectantly, whereas the aggressive nature of DLBCL warrants more intensive chemotherapy. Our case also shows that in patients with suspicious CNS lesions, presence of systemic malignancy does not eliminate the need for brain biopsy, and that clinical deterioration should prompt biopsy if not already performed.

CTIM-34. JACOB: JOINT ADMINISTRATION OF CDNA FOR TP53, CHECKPOINT INHIBITION, AND BOOST/HYPO FRACTIONATED RADIATION. A PHASE 0/1 STUDY IN CHILDREN WITH RECURRENT, PROGRESSIVE, OR REFRACTORY CNS MALIGNANCIES

Abstract BACKGROUND Pediatric patients with recurrent, progressive, or refractory brain tumors have dismal prognoses and few therapeutic options. Due to the complex biological mechanisms of resistance in these tumors, targeted agents and immunotherapeutic approaches in isolation have yielded disappointing results. The combination of SGT-53, anti-PD-1, and hypofractionated radiation has shown encouraging results in preclinical studies. SGT-53 is a novel nanoparticle carrying cDNA encoding human wild-type human TP53; the nanoparticle uses a single-chain antibody fragment recognizing the human transferrin receptor, leading to excellent blood-brain barrier penetrance and anti-tumor targeting. TP53 therapy work synergistically with immune checkpoint inhibitors like anti-PD-1. Hypofractionated radiation provides additional synergy, increasing vascular access, cytokine production and activating tumor-specific T-cells. METHODS JACOB is a prospective, phase 0/1 clinical trial to evaluate the safety and efficacy of SGT-53 in combination with hypofractionated radiation and anti-PD-1 in children with recurrent, progressive, or refractory CNS malignancies. Inclusion criteria: patients age ≥ 3 and ≤ 21 years, measurable disease, performance status >50 and adequate organ function. The 3 + 3 de-escalation design will be used to determine the maximum tolerated dose (MTD) of SGT-53 in combination with ICI and radiation. Dose limiting toxicities will be evaluated. SGT-53 will be administered two times per week. Hypofractionated radiation will be given in week 2, and anti-PD-1 (once in 2 weeks) will begin on the second week of treatment. A maintenance phase of SGT-53 and anti-PD-1 will be continued for up to 12 months. Primary endpoints evaluate toxicities related to SGT-53 and plasma pharmacokinetics. Secondary and exploratory endpoints include best radiological response, and immunobiological markers. Twelve patients will be treated in the phase I/dose de-escalation cohort. After the MTD has been identified, a target validation/ phase 0 cohort will include up to 4 patients receiving 2 doses of SGT-53 prior to undergoing surgical resection to determine tissue-specific response.

BIOS-04. THE ROLE OF MACHINE LEARNING, PREDICTIVE MODELING, AND DEEP LEARNING IN ASSESSING METABOLIC BIOMARKERS TO IMPROVE PROGNOSTICATION IN GLIOBLASTOMA MULTIFORME

Abstract Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in the United States, accounting for approximately 56.6% of all gliomas and 47.7% of all primary malignant CNS tumors. The prognosis of GBM is notably grim, with a 1-year relative survival rate of 41.4% and a 5-year survival rate of 5.8% following diagnosis. Recent efforts to identify potential therapeutic targets have utilized tumor omics data integrated with clinical information that leverages machine learning (ML) algorithms. However, there remains a paucity of studies assessing the value of these ML models as prognostic tools in GBM. A systematic search adhering to PRISMA guidelines was conducted to identify all studies describing the use of a ML algorithm involving GBM metabolic biomarkers and each algorithm's accuracy. Ten studies were included for final analysis. They were diagnostic (n = 3, 30%), prognostic (n = 6, 60%), or both (n = 1, 10%), respectively. Most studies analyzed data from multiple databases, while 50% (n = 5) included additional original samples. At least 2,536 data samples were run through a ML algorithm. 27 ML algorithms were recorded with a mean 2.8 algorithms per study. Algorithms were supervised (n = 22, 79%) or unsupervised (n = 6, 21%), and continuous (n = 21, 75%) or categorical (n = 7, 25%). The mean reported accuracy and AUC of ROC was 95.63% and 0.779, respectively. 106 metabolic markers were identified, but only EMP3 was reported in multiple studies. Many studies have identified potential biomarkers for GBM diagnosis and prognostication. These algorithms show promise; although, a consensus on even a handful of biomarkers has not been made. An integration of ML algorithms for biomarker detection combined with radiomics-based tumor imaging will be necessary to ascertain the greatest level of accuracy and precision.

The Scope, Trends, and Challenges of Neurosurgical Research in Nigeria: A Bibliometric Review

This study investigates the scope, trends, and challenges of neurosurgical research in Nigeria since inception of the specialty in1962. A bibliometric review of the neurosurgical literature from Nigeria was performed. Variables extracted included year and journal of publication, article topic, article type, research type, study design, article focus area, and limitations. Descriptive and quantitative analyses were performed for all variables. Trends of research publications were described in three periods: pioneering (1962-1981), recession (1982-2001), and resurgent (2002-2021). Of the 1023 included articles, 10.0% were published in the pioneering period, 9.2% in the recession period, and 80.8% in the resurgent period. Papers were predominantly published in World Neurosurgery (4.5%) and Nigerian Journal of Clinical Practice (4.0%). A total of 79.9% of the 4618 authors were from Nigerian institutions; 86.3% of the articles covered clinical research and were mainly focused on service delivery and epidemiology (89.9%). The most prominent topics were traumatic brain injury (25.8%) and central nervous system malignancy (21.4%). Only 4.4% of the publications received funding, mostly from agencies in the United States (31.7%). Barriers to neurosurgical research included lack of clinical databases (18.0%), increasing burden of disease (12.5%), and diagnostic challenges (12.4%). Neurosurgical research in Nigeria continues to grow due to increased training, workforce, and infrastructural improvements. Addressing the major challenges through establishment of research databases, development of evidence-based management guidelines, and increasing research training, funding and opportunities can increase research capacity in Nigeria.

Proton Therapy for Advanced Juvenile Nasopharyngeal Angiofibroma.

To provide the first report on proton radiotherapy (PRT) in the management of advanced nasopharyngeal angiofibroma (JNA) and evaluate potential benefits compared to conformal photon therapy (XRT). We retrospectively reviewed 10 consecutive patients undergoing PRT for advanced JNA in a definitive or postoperative setting with a relative biological effectiveness weighted dose of 45 Gy in 25 fractions between 2012 and 2022 at the Heidelberg Ion Beam Therapy Center. Furthermore, dosimetric comparisons and risk estimations for short- and long-term radiation-induced complications between PRT plans and helical XRT plans were conducted. PRT was well tolerated, with only low-grade acute toxicities (CTCAE I-II) being reported. The local control rate was 100% after a median follow-up of 27.0 (interquartile range 13.3-58.0) months. PRT resulted in considerable tumor shrinkage, leading to complete remission in five patients and bearing the potential to provide partial or complete symptom relief. Favorable dosimetric outcomes in critical brain substructures by the use of PRT translated into reduced estimated risks for neurocognitive impairment and radiation-induced CNS malignancies compared to XRT. PRT is an effective treatment option for advanced JNA with minimal acute morbidity and the potential for reduced radiation-induced long-term complications.

Are Psychiatric Comorbidities in the Radiation Oncology Patient Population Under-Recognized by Providers?

Under-recognition of psychiatric comorbidities may be directly tied to potential for poorer patient outcomes. However, there is a paucity of data in radiation oncology settings. This study hypothesized that a disparity exists between the perceived prevalence of psychiatric comorbidities in patients receiving radiotherapy and the rate at which radiation oncologists screen patients for anxiety and depression. From April-July 2021 an online survey was conducted of radiation oncologist members of ASTRO with self-identified practice specializations. Randomly selected invitations were electronically sent to providers from diverse practice backgrounds and geographic locations within the United States and Canada and was conducted using an IRB-reviewed, institutionally approved Microsoft Forms platform. The questionnaire consisted of 20 items examining a broad range of factors that involved general practice demographics, patient screening practice patterns, treatment details and preferred options, and availability and referral data for specialist care for possible psychiatric comorbidities. Statistical analysis was performed using Fisher's exact test. For questions with Yes/No responses, exact binomial test was used. A total of 500online invitations were emailed with 55 responses. Of the responders, 3 did not provide consent. Therefore, 52 (10.4%) responses were included in the analysis and are the subject of this report. This response rate is consistent with other published studies of this type. 85% (p<0.001) of respondents identified the need to screen for psychiatric comorbidities in radiation oncology settings. However, 71% (p = 0.003) did not perform formal screening for psychiatric comorbidities, and of those who did screen, there was no uniformity in the screening tool utilized. Likewise, 79% (p<0.001) did not initiate treatment for psychiatric condition(s). Of providers that did initiate treatment, 91% (p = 0.012) felt that psychiatric comorbidities were under-diagnosed in their patient population. No association was made between providers who specialize in CNS malignancies as being more likely to recognize psychiatric comorbidities in their patient population versus those who do not. Importantly, 75% self-reported that they would benefit from additional training to assess psychiatric comorbidities (p<0.001). A need to screen for psychiatric comorbidities in radiation oncology settings was identified despite very little formal screening performed. Responses revealed adequate community resources exist for referral in most instances. However, providers did not routinely refer patients for treatment of psychiatric comorbidities, even when recognized. This survey identified an unmet need for improved education among providers to engage in screening and referral for psychiatric comorbidities, and to develop a care system that supports standardization of screening practices and tools in this patient population.

Spatially Resolved Whole Transcriptome Analysis of Histologically-Characterized Tissue Microarray of Patient-Matched Primary and Recurrent Glioblastomas to Identify Underlying Mechanisms of Treatment Resistance

Glioblastoma multiforme (GBM) is a lethal CNS malignancy. Radiation therapy increases overall survival, but tumors often recur in high-radiation dose regions. Additionally, recent investigations have underscored the importance of intra-tumoral heterogeneity as a driver of GBM biology. The purpose of this investigation is to characterize transcriptome differences in primary and recurrent GBM patient clinical samples using a digital spatial profiling approach to better appreciate treatment resistance mechanisms. To address the lack of understanding of molecular mechanisms of resistance in GBM, patient-matched primary and recurrent GBM pathological specimens were identified within the brain tissue biorepository and tissue cores were selected for generation of a tissue microarray (TMA). Hematoxylin and eosin staining with histomorphological (cellular tumor, pseudopalisading necrosis, invasive edge, and perivascular inflammation) scoring were performed in a blinded fashion for every core. This array was then molecularly characterized using digital spatial profiling of the transcriptome. Quality assurance including filtering of lowly expressed genes followed by downstream analyses of the data were performed using the manufacturer's recommended methods within their Bioconductor library. Gene Set Enrichment Analysis (GSEA) was then performed on the ranked gene lists. After recommended filtering, 6171 genes and 248 regions of interest remained for downstream analysis representing 22 unique patients across four different tumor histomorphological types. Significance testing revealed 679 genes that were differentially expressed between primary and recurrent tumor samples (at FDR<1%). On GSEA analysis, the chromosomal positional locus that contains genes most strongly up-regulated is 12q14, a locus that was previously identified as genomically amplified in multiple patient-derived xenograft lines after radiation selection. Additionally, recurrent tumors display a transcriptional profile more similar to the mesenchymal subtype, whereas primary tumors have a more classical transcriptional phenotype. The epithelial-to-mesenchymal transition pathway is particularly strongly up-regulated in recurrent tumors. Recurrent selection at previously identified genomic loci and molecular pathways underscores a possible conserved set of pathways for treatment resistance. This analysis has yielded a set of gene and molecular pathways that will guide future work in our lab targeting treatment resistance using novel therapeutics and radiation techniques in GBM. Future directions include assessing the feasibility of mapping these clinical samples onto our previously generated panel of comprehensively characterized patient-derived xenograft lines.

Memantine for Pediatric Patients Receiving Cranial Irradiation: A Pilot Study

While memantine has become standard in certain adults receiving brain RT to decrease the cognitive impacts of RT, it is unknown whether pediatric patients can take and tolerate memantine or experience benefit. In this prospective single-arm feasibility study, we hypothesized pediatric patients receiving brain RT would tolerate memantine with good treatment adherence. Patients aged 4-18 years with a primary CNS malignancy (excluding WHO Grade IV astrocytoma and glioblastoma) receiving intracranial RT were eligible. A 6-month course of memantine was given during and after RT. Dosing began once daily at 5 mg with up-titration in 5 mg increments over 4 weeks to a weight-based maximum (0.4 mg/kg to the closest 5 mg), not to exceed 10 mg BID. To reduce patient and clinical research associate (CRA) burden, medication adherence was tracked via the Medisafe Pill and Reminder application which study staff helped install on the patient or parent's smart phone. A paper pill diary was provided for those unable to use the app. The primary endpoint was to achieve 80% adherence rate to memantine in 80% of patients measured 1-month post-RT. Eighteen patients (14 male and 4 female, median age 11.5 years (range: 4-18)) were enrolled from 2020-2022. The study closed early after enrolling 18 of 20 planned patients to avoid competing with the phase III randomized Children's Oncology Group (COG) study AACL2031. One patient withdrew for cognition-altering substance-use, leaving 17 patients with data available for analysis. Histologies included germ cell tumor (n = 6), craniopharyngioma (n = 3), choroid plexus papilloma (n = 2), ependymoma (n = 2), glial/astrocytoma (n = 2), medulloblastoma (n = 1), and meningioma (n = 1). Thirteen had surgery, and 9 received chemotherapy. Eight received craniospinal irradiation (CSI). Median RT dose was 54 Gy (range 36-59.4) in 30 fractions (range: 20-33). At data freeze, all 17 had passed the 1-month post-RT time point. One patient discontinued memantine after a single dose due to nausea. Pill-reports were available for 14 of the remaining 16; two patients did not complete digital pill logs. For those with complete logs, all adherence rates were above 80%, with a median of 99.32% pill completion rate (range: 92.67-100). Seven (50%) took 100% of prescribed doses. Irrespective of adherence for the 2 unavailable for evaluation, the primary endpoint was still achieved. Grade 1 toxicities included headache (n = 6, 35%) and constipation (n = 1, 6%); there were no grade 2+ toxicities. At last follow-up, 15/16 have completed the full 6-month memantine course. Secondary endpoints including neurocognitive evaluations have not yet been met and will be the subject of future reports. Memantine is a feasible and well-tolerated addition to multi-modality treatment for pediatric brain tumors. Secondary endpoints of this study and results of the ongoing COG study are awaited to define the value of memantine in this population.

TUMOUR TREATING FIELDS WITH DDR INHIBITORS EFFECTIVELY LEADS TO CHEMO-/RADIO-SENSITISATION OF GLIOMAS

Abstract AIMS High grade gliomas are the most common CNS malignancies and cause ~200,000 deaths/year globally. Glioblastoma (WHO grade IV) confer the worst prognoses with their treatment being hindered by glioma stem cell-like (GSC) tumour sub-regions and high intratumoural spatio-heterogeneity. Tumour Treating Fields (TTFields) exert clinically approved alternating electric fields of intermediate frequency which induces anti-mitotic effects within concomitant deleterious effects on cellular responses to DNA damage (DDR). Therefore, treatment resistance could be overcome with TTFields with clinically developed DDR inhibitors (DDRi) to cause chemo-/radio- sensitisation. METHOD Surgically resected samples derived from the tumour core and invasive edge were processed to create GSC cell lines, offering highly clinically relevant models. These were grown in either 2D or in 3D-printed AlvetexTM scaffolds, treated with DDRi, subjected to chemo-/radio-therapy and then placed under TTFields (200 kHz, 48- 72 hrs). Survival was measured by clonogenic assays after 3 weeks. Immunofluorescence and western blot analysis were used to analyse the combination treatment effects on the DDR. RESULTS TTFields with DDRi led to significant chemo/radio-sensitisation in both 2D and 3D intratumoral core/edge GSC models. Western blot and immunofluorescence analyses revealed that DNA damage was heightened by the combination treatments with lesion resolution being impaired. CONCLUSIONS DDRi with concurrent TTFields effectively leads to significant chemo-/radio-sensitisation in clinically relevant 3D GSCs which model spatio-heterogeneity which is thought to impede treatment effcacy. Given that all the DDRi used are BBB penetrable and are either clinically approved or in clinical trials, TTFields could additionally compliment these treatment regimens in gliomas to boost their effcacy.

P10.26.B EXPLORING POTENTIAL ANTITUMOR EFFECTS OF CANNABIDIOL AND TETRAHYDROCANNABINOL IN A PATIENT-DERIVED GLIOBLASTOMA MODEL

Abstract BACKGROUND Glioblastoma (GBM) is a CNS malignancy which is in dire need of novel treatment options. Drug repurposing has become a means to circumvent major obstacles that accompany drug development for GBM. The cannabinoids cannabidiol (CBD) and tetrahydrocannabinol (THC) have garnered the interest of the scientific community for the treatment of GBM as they possess pleiotropic effects in other pathologies. In the present study we are investigating potential antitumor effects of these cannabinoids by using our patient derived GBM model which recapitulates GBM in its genetic make-up and heterogeneity. MATERIAL AND METHODS To assess potential antitumor effects in vitro, we performed a screen on 20 patient derived GBM cultures to obtain a sensitivity profile for both cannabinoids. These cultures ranged in background regarding primary/recurrence and IDH mutation. To investigate effects of these cannabinoids on GBM radio-and-chemosensitivity, combination studies with either lomustine (CCNU) or irradiation (RTx) were performed on recurrent GBM cultures. The zero-interaction potential method was used to quantify synergy between the cannabinoids. The enhancement factor was used to quantify potential radiosensitization or ratio-effects between the cannabinoids. RESULTS Screening of both cannabinoids revealed CBD to possess a higher level of cytotoxicity than THC. IC50 values of CBD ranged from 2.5 - 18.5 µM and the values of THC ranged from 7.20 - 47.60 µM. In a panel of 8 cultures, combinations of CBD with THC, CBD with CCNU and THC with CCNU was tested to gain insight in combination effects. In 1/8 cultures synergy was observed between CBD and THC. In 1/8 cultures synergy between CBD and CCNU was observed and in 4/8 cultures synergy between THC and CCNU. When combined with irradiation, no enhancement was observed in any of the 4 cultures tested. No ratio-dependent enhancement between the cannabinoids was observed when combined in a 1:1, 1:4 or 4:1 ratio of CBD:THC. CONCLUSION Screening of the cannabinoids CBD and THC revealed that CBD displays a stronger cytotoxic effect than THC. Combinations of either of the two with each other or CCNU revealed moderate additive effects in the majority of cultures and synergy in a small subset. We did not observe radiosensitizing effects in our patient derived GBM model. Relating in vitro found cytotoxic concentrations to clinically achievable concentrations, we found that CBD requires approximately 3 times higher plasma concentrations and THC &amp;gt;40 times to achieve an antitumor effect. Currently we are investigating long term treatment effects of CBD and its mechanism of action.

P04.10.A ASSESSMENT OF VDR STATUS BY IMMUNOHISTOCHEMISTRY IN CHILDHOOD MALIGNANCIES - VDR EXPRESSION PATTERN OF CNS TUMORS

Abstract BACKGROUND Childhood cancers, including CNS tumors, the second most prevalent entities after hematological malignancies cannot generally be prevented or identified through screening, the disease is often diagnosed at advanced stages, and this obviously affects patient outcomes negatively. There is an urgent need for identifying prognostic and therapeutic biomarkers. Our previous work has shown a correlation between lower vitamin D levels in children with cancer and adverse prognosis. VDR expression in childhood solid tumors has been linked to tumor characteristics and patient survival only in few studies, moreover literature found that VDR plays a role in the development of the central nervous system. METHODS For this study, 177 children with solid tumors were selected whose biopsies and tumor tissue formalin-fixed, paraffin-embedded tissue blocks were available for immunohistochemical (IHC) analysis at Semmelweis University, Budapest (Hungary). To investigate the association between the presence of VDR in the tumor tissue and outcome, tumor samples and the survival dataset of 110 children were available. RESULTS We found that minor VDR expression was associated with a significantly less favorable prognosis (p = 0.0061) in the examined childhood solid tumors. The rate of VDR expression differed significantly between tumor types (p &amp;lt;0.0001). In case of CNS tumors pathological observations on VDR expression characteristics partly not correlated with previous literature. In some ependymoma samples an utterly novel VDR pattern was observed. CONCLUSION In conclusion, VDR expression measured by IHC staining is inversely associated with aggressive characteristics in different childhood cancers. The downregulation of VDR expression in more aggressive childhood cancers suggests that functional vitamin D activity may slow or block cancer progression. The presence of VDR may have prognostic and therapeutic implications for CNS malignancies. Knowledge of the VDR status in childhood solid tumors provides clinicians with a valuable biomarker and based on this, additional therapy (vitamin D, and analogs) to use alongside conventional first-line oncotherapy.

Depression - the first symptom of a brain tumor or a consequence of the process neoplastic process - a review of the literature

Introduction and objective&#x0D; CNS malignancies account for about 1.6% of all diseases today. In people diagnosed with abrain tumor with a poor prognosis, we often see disorders from the psychiatric spectrum,most often depressive disorders. In this paper, we want to focus on whether depression occursas a sequel to cancer or perhaps is the first of the symptoms of a CNS tumor.&#x0D; Review methods&#x0D; For the analysis, the PubMed medical database was searched, and articles containing studiesand case reports of people with CNS tumor and depressive disorders that occurred eitherbefore diagnosis or at any time during the course of the disease were selected&#x0D; Abbreviated description of the state of knowledge&#x0D; CNS tumors produce symptoms such as epilepsy, visual disturbances, paresis, but alsobehavioral disorders. This is determined by the location of the tumor. Depression is a mentaldisorder manifested mainly by lowered mood. This disorder can coexist with tumorsoccurring in the frontal lobe or be present regardless of the location of the tumor, in peoplediagnosed with a tumor with a poor prognosis.&#x0D; Summary&#x0D; Analyzing the selected articles, we see that in people who were diagnosed with a tumorlocated in the frontal lobe, often the first symptom was depressive disorders, which evenpreceded neurological symptoms. When depression is diagnosed, appearing suddenly andrefractory to treatment, one should consider whether there is an underlying pathologicallesion in the CNS. Unfortunately, there are no specific guidelines for imaging studies indepressive disorders. People who suffer from malignant tumors with a poor prognosis shouldbe cared for by a psychologist, because as the disease progresses, the symptoms worsen,affecting the prognosis.

BSLD-03 MIMICKING CAFS, PIAL CELLS SUPPORTLEPTOMENINGEAL METASTASIS

Abstract Leptomeningeal metastasis (LM), the spread of cancer into cerebrospinal fluid (CSF)-filled coverings of the brain and spinal cord, is a dismal complication of cancer leading to rapid neurologic disability and death. While a diverse array of primary tumors may result in LM, recent work from our laboratory (Chi Y et al 2020 Science) demonstrates a conserved transcriptional signature, independent of primary tumor, suggesting that tumor-microenvironmental interactions play a dominant role in this pathology. We have proteomically interrogated CSF collected from breast (n = 45), lung (n = 30), and melanoma (n = 27) patients with and without LM. We detect robust expression of inflammatory cytokines in all LM+ samples, 15 of these cytokines including IL8, IL6, and CXCL1 are conserved across tumor types in the presence of LM. Because cancer cells in the CSF do not express mRNA associated with these cytokines, we hypothesized that these inflammatory cytokines may originate from the microenvironment. Within the leptomeninges, LM cells adhere to and interact with the innermost layer of the meninges, the pia mater, which contains fibroblast-like cells. Co-culture of cancer cells with pial cells induced changes in the pial cell transcriptome and secretome, leading to increased IL8, IL6, and CXCL1 production. This communication between cancer cells and pial cells is preserved in the absence of direct cell-cell contact. These pial cells support cancer cell growth in vivo, as measured by co-implantation experiments. In addition, bulk RNA sequencing of mouse pial cells shows an inflammatory signature upregulated in the presence of LM. Taken together, these observations support a cancer-associated-fibroblast like role for pial cells in the setting of LM. Our work extends the CAF phenotype beyond classical fibroblasts to include pial cells, suggesting novel therapeutic opportunities within CNS malignancies.

Systematic Review of Photodynamic Therapy in Gliomas.

Over the last 20 years, gliomas have made up over 89% of malignant CNS tumor cases in the American population (NIH SEER). Within this, glioblastoma is the most common subtype, comprising 57% of all glioma cases. Being highly aggressive, this deadly disease is known for its high genetic and phenotypic heterogeneity, rendering a complicated disease course. The current standard of care consists of maximally safe tumor resection concurrent with chemoradiotherapy. However, despite advances in technology and therapeutic modalities, rates of disease recurrence are still high and survivability remains low. Given the delicate nature of the tumor location, remaining margins following resection often initiate disease recurrence. Photodynamic therapy (PDT) is a therapeutic modality that, following the administration of a non-toxic photosensitizer, induces tumor-specific anti-cancer effects after localized, wavelength-specific illumination. Its effect against malignant glioma has been studied extensively over the last 30 years, in pre-clinical and clinical trials. Here, we provide a comprehensive review of the three generations of photosensitizers alongside their mechanisms of action, limitations, and future directions.

Cerebral delivery of redox-responsive lenalidomide prodrug plus methotrexate for primary central nerve system lymphoma combination therapy.

Primary central nervous system lymphoma (PCNSL) is an extremely malignant CNS tumor with high incidence and mortality rates. Its chemotherapy in the clinic has been restricted owing to unsatisfactory drug distribution in the cerebral tissues. In this study, a redox-responsive prodrug of disulfide-lenalidomide-methoxy polyethylene glycol (LND-DSDA-mPEG) was successfully developed for the cerebral delivery of lenalidomide (LND), and methotrexate (MTX) via subcutaneous (s.c.) administration at the neck for combined anti-angiogenesis and chemotherapy on PCNSL. Both the subcutaneous xenograft tumor model and orthotopic intracranial tumor model demonstrated that the co-delivery of LND and MTX nanoparticles (MTX@LND NPs) may significantly inhibit the growth of lymphoma and effectively prevent liver metastasis by downregulating CD31 and VEGF expression. Moreover, an orthotopic intracranial tumor model further verified that through s.c. administration at the neck, redox-responsive MTX@LND NPs could bypass the blood-brain barrier (BBB), efficiently distribute into brain tissues, and effectively inhibit lymphoma growth in the brain, as detected by magnetic resonance imaging (MRI). Taken together, this biodegradable, biocompatible, and redox-responsive nano-prodrug with highly effective targeted delivery of LND and MTX in the brain through the lymphatic vasculature may provide a facile and feasible treatment strategy for PCNSL in the clinic.

OTHR-08. MULTIDISCIPLINARY APPROACH TO PAEDIATRIC BRAIN CANCER BIO-BANKING IMPROVES ENROLLMENT, FACILITATES DISCOVERY RESEARCH, AND ENABLES BETTER ACCESS TO DIAGNOSTIC AND THERAPEUTIC STUDIES

Abstract Despite the significant progress made in the multi-modal treatment of childhood malignancies over the last four decades with a concomitantly increased cure rates, the benefit is still largely limited to patients with leukemias, lymphomas and localized non-CNS solid tumors, leaving patients with high-risk non-CNS solid tumours and most CNS malignancies with minimal advancements. More research is critical to understand what drives these cancers and to investigate the best ways to deliver curative therapies. Translational research relies on patient-derived tissue samples, animal models and cell-cultures to understand the biological, genetic, and molecular mechanisms of disease. To facilitate patient care and outcomes it is becoming increasingly important that paediatric clinical trials include tissue availability as part of eligibility criteria, making collection and storage of patient tissue a mandate of personalized medicine and a pillar of modern paediatric cancer medicine. Monash Children’s Cancer Biobank was established in 2011. Since 2017, a total of 64 patients were diagnosed with CNS malignancies across all grades, with an overall 69% of patients’ tissues being bio-banked at the time of initial diagnosis. Through the combination of an educational forum, regular multi-disciplinary meetings, and the early involvement of medical oncology and biobank staff, with our neurosurgical and clinical pathology colleagues, as part of patient management planning, the tissue acquisition for bio-banking increased from 44% to 82% over the course of 5 years. This consequently led to a 100% enrollment to tissue-enabling studies allowing for banking of both fresh-frozen tissue and living cell-line models, facilitating discovery research efforts as part of the Victorian Paediatric Cancer Consortium’s molecular analysis pipeline (https://vicpcc.org.au/dashboard). This significantly improves opportunities for identification of targetable pathways, access to targeted therapies, enrollment onto treatment clinical trials and identification of patients with cancer predisposition syndromes.