bluuebunny/crossref_metadata_2025 huggingface dataset:
BIOM-09. MYO-INOSITOL LEVELS ON MR SPECTROSCOPY CAN PREDICT FAILURE OF ANTI-ANGIOGENIC TREATMENT IN RECURRENT GLIOBLASTOMA
Authors: El-Abtah Mohamed , Wenke Michael , Talati Pratik , Fu Melanie , Kim Daniel , Weerasekera Akila , He Julian , Vaynrub Anna , Vangel Mark , Rapalino Otto , Andronesi Ovidiu , Arrillaga-Romany Isabel , Forst Deborah , Yen Yi-Fen , Rosen Bruce , Batchelor Tracy , Gonzalez Ramon , Dietrich Jorg , Gerstner Elizabeth , Ratai Eva-Maria
Published: November 2021

BACKGROUND

Recurrent glioblastoma (rGBM) patients are often treated with anti-angiogenic agents such as bevacizumab (BEV). Despite therapeutic promise, conventional MR methods fail to determine which patients may not benefit. PURPOSE: The purpose of this study was to utilize magnetic resonance spectroscopic imaging (MRSI) with intermediate and short echo time to generate corrected Myo-inositol normalized by contralateral creatine (mI/c-Cr) in patients with rGBM treated with BEV and investigate whether it can predict survivorship prior to BEV initiation (baseline) and at 1-day, 4-weeks, and 8-weeks thereafter.

METHODS

We conducted a prospective, longitudinal study and evaluated spectroscopic data of myo-inositol (mI), a glial marker and osmoregulator within the brain, normalized to contralateral-creatine (mI/c-Cr) in the intratumoral, contralateral normal appearing white matter, and peritumoral volumes of rGBM patients. Area under the ROC curve (AUC) was calculated for all volumes at baseline, 1-day, 4-weeks, and 8-weeks after treatment to determine mI/c-Cr’s ability to predict survivorship.

RESULTS

21 participants (62 ± 12 years, 15 men) were evaluated. Lower mI/c-Cr in the tumor prior to and during BEV treatment predicted poor survivorship, with ROC analyses illustrating an AUC of 0.75 at baseline, 0.87 at 1-day, and 1 at 8 weeks. Lower levels of mI/c-Cr were also observed in the contralateral and the peritumoral volumes for shorter-term survivors. In the contralateral volume, lower mI/Cr was predictive of shorter-term survival at baseline and all other timepoints. Within the peritumoral volume, lower mI/c-Cr was predictive of shorter-term survival at baseline (AUC=0.80), 1-day (AUC=0.93), and 4-weeks (AUC=0.68).

CONCLUSIONS

Lower levels of mI/c-Cr within intratumoral, contralateral, and peritumoral volumes were predictive of poor survivorship and anti-angiogenic treatment failure as early as one month before BEV treatment. Acquiring MRSI alongside conventional MR imaging modalities can convey critical information regarding tumor microenvironment that informs management of patients with rGBM.
BIOM-10. PRECLINICAL PLATFORM FOR THE IDENTIFICATION OF DEUTERIUM MAGNETIC RESONANCE SPECTROSCOPY-BASED BIOMARKERS OF BRAIN TUMOR METABOLISM
Authors: Batsios Georgios , Tran Meryssa , Taglang Céline , Gillespie Anne Marie , Ronen Sabrina , Costello Joseph , Viswanath Pavithra
Published: November 2021

Metabolic reprogramming is a fundamental hallmark of cancer, which can be exploited for non-invasive tumor imaging. Deuterium magnetic resonance spectroscopy (2H-MRS) recently emerged as a novel, translational method of interrogating flux from 2H-labeled substrates to metabolic products. However, to date, preclinical studies have been performed in vivo, an endeavor which suffers from low-throughput and potential wastage of animal life, especially when considering studies of treatment response. Developing in vitro assays for monitoring metabolism of 2H-labeled substrates will enhance throughput, lead to the rapid evaluation of new 2H-based probes and enable identification of treatment response biomarkers, thereby allowing the best 2H-based probes to be translated for further in vivo assessment. The goal of this study was to develop a preclinical cell-based platform for quantifying metabolism of 2H-labeled probes in brain tumor models. Since the Warburg effect, which is characterized by elevated glycolytic production of lactate, is a metabolic phenotype of cancer, including brain tumors, we examined metabolism of 2H-glucose or 2H-pyruvate in patient-derived glioblastoma (GBM6) and oligodendroglioma (BT88) cells and compared to normal human astrocytes (NHACONTROL). Following incubation in media containing [6,6’-2H]glucose or [U-2H]pyruvate, 2H-MR spectra obtained from live cell suspensions showed elevated 2H-lactate production in GBM6 and BT88 cells relative to NHACONTROL. Importantly, 2H-lactate production from [6,6’-2H]glucose or from [U-2H]pyruvate was reduced in GBM6 or BT88 cells subjected to irradiation and temozolomide, which is standard of care for glioma patients, pointing to the utility of this method for detecting response to therapy. Collectively, we have, for the first time, demonstrated the ability to quantify metabolism of 2H-MRS probes in live cell suspensions and validated the utility of our assay for differentiating tumor from normal cells and assessing response to therapy. Our studies will expedite the identification of novel 2H-MRS probes for imaging brain tumors and potentially other types of cancer.
BIOM-14. METABOLIC BIOMARKERS OF TERT-TARGETED THERAPY FOR HUMAN GLIOBLASTOMA DETECTED BY MAGNETIC RESONANCE SPECTROSCOPY
Authors: Minami Noriaki , Hong Donghyun , Stevers Nicholas , Batsios Georgios , Gillespie Anne Marie , Pieper Russell , Costello Joseph , Viswanath Pavithra , Ronen Sabrina
Published: November 2021

BACKGROUND

TERT promoter mutations that result in TERT expression are observed in over 80% of GBM. Moreover, the upstream transcription factor GABPB1 was recently identified as an ideal therapeutic target for tumors with TERT promoter mutations. In that context, non-invasive reliable biomarkers that can help detect TERT expression are needed. The aim of this research was to assess the value of MRS-detectable metabolic changes as biomarkers of TERT expression and TERT-targeted therapy in GBM.

METHODS

Genetically engineered GBM cells (NHARas/TERT) treated with TERT siRNA were compared to siCtrl-treated cells, and stable TERT and GABPB1 knock down GBM cells (U251, GBM1) were compared to shCtrl. 1H-MRS and 13C-MRS metabolic data was acquired from cell extracts using a Bruker 500MHz scanner. Hyperpolarized MRS studies of live cells used a HyperSense DNP polarizer and data was acquired using a Varian 500MHz scanner. Spectra were analyzed using Mnova and Matlab software. Multivariate data analysis was performed using SIMCA software.

RESULTS

Unbiased PCA analysis of 1H-MRS metabolic data showed separation of TERT or GABPB1 knock down and control cells. VIP predictive scores revealed that lactate and GSH were the top altered metabolites with a significant drop observed in both metabolites in every model following TERT silencing. Consistent with the reduction in GSH, spectrophotometric assays showed a significant drop in NADPH and NADH. 2-13C glucose flux analysis revealed that both glycolysis and PPP-related metabolites were reduced in TERT knock down cells. Hyperpolarized [1-13C]-pyruvate flux to lactate was also reduced, confirming that the glycolytic pathway was altered following TERT knock down.

CONCLUSION

1H MRS-detectable lactate and GSH, combined with hyperpolarized 13C MRS-detectable metabolic fluxes, could serve as metabolic biomarkers of TERT-targeted therapy for human GBM with TERT promoter mutations. These biomarkers could be translated to the clinical, improve the monitoring of GBM patients and advance precision medicine.
BIOM-26. SURVIVAL OUTCOMES AND PROGNOSTIC FACTORS IN PRIMARY GLIOBLASTOMA FROM A REAL-WORLD RETROSPECTIVE STUDY
Authors: Brown Nicholas , Ottaviani Diego , Tazare John , Gregson John , Kitchen Neil , Brandner Sebastian , Fersht Naomi , Mulholland Paul
Published: November 2021

INTRODUCTION

Glioblastoma has limited therapeutic options and is associated with a poor prognosis. Treatment, clinical outcomes, and prognostic factors remain poorly characterised outside of the selected population enrolled in clinical trials.

METHODS

Demographic, tumour molecular profiles, treatment, and survival data was collated for patients who underwent a biopsy or resection diagnostic of de novo glioblastoma at our centre between July 2011 and December 2015. We used multivariate proportional hazards models to examine the association of potential prognostic markers with survival.

RESULTS

490 patients were identified: 60% were male with a median age of 59 years. 60% of patients had surgical debulking, and 40% biopsy only. Subsequently, 56% had standard chemoradiotherapy, 25% non-standard chemo/radio-therapy, and 19% no further treatment; 22% of patients who had adjuvant therapy had surgery at relapse, 37% second-line chemotherapy, and 11% third-line chemotherapy. Median survival was 9.2 months (IQR 7.9-10.3 months), with survival at 12- and 24-months 41% and 13% respectively. In multivariate analysis, longer survival was associated with debulking surgery vs biopsy alone (14.9 vs 8 months) (HR 0.54 [95%CI 0.41-0.70]); subsequent treatment after diagnosis (HR 0.12 [0.08-0.16]) (standard chemoradiotherapy [16.9 months] vs non-standard regimens [9.2 months] vs none [2.0 months]); tumour MGMT promotor methylation (HR 0.71 [0.58-0.87]); and younger age (hazard ratio vs age< 50: 1.70 [1.26-2.30] for ages 50-59; 3.53 [2.65-4.70] for ages 60-69; 4.82 [3.54-6.56] for ages 70+). IDH mutation was associated with longer survival (HR 0.64 [0.66-0.97] in univariate but not multivariate analysis.

CONCLUSION

Median survival for patients with glioblastoma is less than a year. Younger age, debulking surgery, treatment with chemoradiotherapy, and MGMT promotor methylation are independently associated with longer survival.
BIOM-31. ERK1/2 PHOSPHORYLATION PREDICTS SURVIVAL FOLLOWING ANTI-PD-1 IMMUNOTHERAPY IN RECURRENT GLIOBLASTOMA
Authors: Arrieta Víctor , Chen Andrew X , Kane J Robert , Kang Seong Jae , Kassab Cynthia , Dmello Crismita , Zhao Junfei , Burdett Kirsten , Upadhyayula Pavan , Chang Catalina , Shilati Joseph , Jaishankar Dinesh , Chen Li , Gould Andrew , Zhang Daniel , Yuan Jinzhou , Zhao Wenting , Ling Xiaoyang , Burks Jared K , Laffleur Brice , Amidei Christina , Bruce Jeffrey N , Lukas Rimas V , Yamaguchi Jonathan T , Cieremans David , Rothschild Gerson , Basu Uttiya , McCord Matthew , Brat Daniel , Zhang Hui , Cooper Lee A D , Zhang Bin , Sims Peter , Cloughesy Timothy , Prins Robert , Canoll Peter , Stupp Roger , Heimberger Amy B , Horbinski Craig , Iwamoto Fabio , Rabadan Raul , Sonabend Adam M
Published: November 2021

PD-1 checkpoint inhibition has led to remarkable clinical responses in several cancer types. Whereas PD-1 blockade has not shown an overall survival (OS) benefit for glioblastoma (GBM) patients, a subset of them exhibit long-term responses to this immunotherapy. Previously, we reported an enrichment of BRAF/PTPN11 activating mutations in 30% of recurrent GBMs that responded to PD-1 blockade, but the molecular profile of the majority of responders remained elusive. Given that BRAF and PTPN11 promote MAPK/ERK signaling, we investigated whether activation of this pathway is associated with response to PD-1 inhibitors in recurrent GBM, including patients that do not harbor BRAF/PTPN11 mutations. Immunohistochemistry for ERK1/2 phosphorylation (p-ERK), a marker of MAPK/ERK pathway activation, was performed in a discovery cohort including pre-treatment specimens of 29 recurrent GBM patients treated with adjuvant PD-1 blockade, and 33 patients who did not undergo immunotherapy. p-ERK was predictive of response and OS following PD-1 blockade. Yet p-ERK was not associated with OS in patients not treated with immunotherapy. p-ERK was also associated with OS in a validation GBM cohort treated with adjuvant anti-PD-1 therapy. Single-cell RNA-seq and multiplex-immunofluorescence analyses revealed that p-ERK was mainly localized in tumor cells and high p-ERK GBMs contained tumor-infiltrating myeloid cells and microglia with elevated expression of MHC class II and associated genes. Thus, our findings indicate that ERK1/2 activation in recurrent GBM is predictive of response to PD-1 blockade and is associated with a distinct myeloid cell phenotype.
BIOM-36. SERIAL ASSESSMENT OF MEASURABLE RESIDUAL DISEASE IN MEDULLOBLASTOMA LIQUID BIOPSIES
Authors: Liu Anthony Pak-Yin , Smith Kyle , Kumar Rahul , Paul Leena , Lin Tong , Maass Kendra , Pajtler Kristian , Bihannic Laure , Orr Brent , Ellison David , Gilbertson Richard , Onar-Thomas Arzu , Gajjar Amar , Robinson Giles , Northcott Paul
Published: November 2021

Medulloblastoma is the most common malignant brain tumor in children. Despite the use of contemporary multi-modal therapy, up to one-third of patients will succumb to disease progression. Conventional response monitoring is based on magnetic resonance imaging and cerebrospinal fluid (CSF) cytology and a marker for measurable residual disease (MRD) is lacking. In this study, we show the clinical utility of profiling CSF-derived cell-free DNA (cfDNA) as a biomarker of MRD based on a sizable cohort of children with medulloblastoma enrolled on a prospective, multi-center, risk-adapted trial (SJMB03; NCT00085202). A total of 476 CSF samples were serially collected from 123 patients by lumbar puncture at post-operative baseline, during therapy, and at regular surveillance after completion of therapy. Using low-coverage whole-genome sequencing (lcWGS), tumor-associated copy-number alterations in CSF-derived cfDNA were investigated as an MRD surrogate for correlation with clinical features and outcomes. MRD was detected in post-operative baseline CSF samples for 85% and 54% of patients with metastatic and localized disease, respectively. The number of MRD-positive patients declined with therapy, yet those with persistent MRD detected at the end of therapy (20 of 68 CSFs at this timepoint) had significantly higher risk of disease progression (hazard ratio 8.94, 95%CI 4.10-19.49; log-rank p< 0.0001). Importantly, MRD-positivity from routine surveillance samples often preceded radiographic progression by more than 3 months. Comparative analyses of copy-number variations obtained from serial CSF samples enabled identification of relapse-specific alterations and early detection of relapse-dominant clones. Overall, our findings advocate for the routine incorporation of CSF-derived liquid biopsies in future medulloblastoma trials.
BIOM-40. TARGETED GENE EXPRESSION PROFILING PREDICTS MENINGIOMA OUTCOMES AND RADIOTHERAPY RESPONSES
Authors: Chen William , Choudhury Abrar , Vasudevan Harish , Lucas Calixto , Nguyen Minh , Young Jacob , Yu Theresa , Lam Tai-Chung , Pu Jenny , Li Lai-Fung , Leung Gilberto , Chan Jason , Oberheim-Bush Nancy Ann , Villanueva-Meyer Javier , Schulte Jessica , Braunstein Steve , Butowski Nicholas , Sneed Penny , Berger Mitchel , Perry Arie , Solomon David , McDermott Michael , Magill Stephen , Raleigh David
Published: November 2021

BACKGROUND

Surgery is the mainstay of meningioma treatment, but improvements in meningioma risk stratification are needed and indications for postoperative radiotherapy are controversial. DNA methylation profiling, copy number variants (CNVs), exome sequencing, and RNA sequencing have improved understanding of meningioma biology, but have not superseded histologic grading, or revealed biomarkers for radiotherapy responses. To address these unmet needs, we optimized and validated a targeted gene expression biomarker predicting meningioma outcomes and responses to radiotherapy.

METHODS

Targeted gene expression profiling was performed on a discovery cohort of 173 meningiomas (median follow-up 8.1 years) and a validation cohort of 331 meningiomas (median follow-up 6.1 years) treated with surgery (n=504) and postoperative radiotherapy (n=73) at independent, international institutions (70% WHO grade 1, 24% WHO grade 2, 6% WHO grade 3). Optimized targeted gene expression models predicting clinical outcomes (34 genes) or radiotherapy responses (12 genes) were developed from the discovery cohort, and compared to histologic and molecular classification systems by performing DNA methylation profiling, CNV analysis, exome sequencing, and RNA sequencing on the same meningiomas.

RESULTS

Targeted gene expression profiling achieved a concordance-index of 0.75 ± 0.03 (SEM) for local freedom from recurrence (LFFR) and 0.72 ± 0.03 for overall survival (OS) in the validation cohort, outperforming WHO grade (5-year LFFR delta-AUC 0.15, 95% CI 0.076-0.229, p=0.001) and DNA methylation grouping (delta-AUC 0.075, 95% CI 0.006-0.130, p=0.01) for LFFR, disease-specific survival, and OS. The biomarker was independently prognostic after accounting for WHO grade, extent of resection, primary versus recurrent presentation, CNV status, DNA methylation group, and Ki67 labeling index, and identified meningiomas benefiting from radiotherapy (interaction p-value=0.0008), suggesting postoperative radiotherapy could be refined in 30.2% of cases.

CONCLUSIONS

Targeted gene expression profiling of 504 meningiomas improves discrimination of meningioma local recurrence, disease-specific survival, and overall survival, and predicts radiotherapy responses.
STEM-17. THE GLIOMA STEM CELL PLATELET INTERACTION DRIVES GBM ONCOGENESIS IDENTIFYING A NOVEL THERAPEUTIC APPROACH
Authors: Sloan Anthony , Hoffman Harry , Harris Peggy , Lee-Poturalski Christine , Elder Theresa , Kerstetter-Fogle Amber , Cioffi Gino , Desai Ansh , Rich Jeremy N , Barnholtz-Sloan Jill , Gupta Anirban Sen , Jankowsky Eckhard , Sloan Andrew
Published: November 2021

The effect of platelets on oncogenesis has been studied extensively in cancer metastasis, but not in glioblastoma (GBM), where metastasis is rare. Here we identify the unique crosstalk between glioma stem cells (GSCs) and platelets within GBM solid tumors that enhance disease progression. Targeting GSCs is considered a promising therapeutic approach; however, no clear method has been identified. High platelet counts have been associated with poor clinical outcome in many cancers including ovarian and endometrial cancer. While platelets are known to affect progression of other tumors, mechanisms by which platelets influence GBM oncogenesis are unknown. Immunofluorescence, qPCR, and western blot were used to evaluate the presence of GSCs and platelets and their colocalization in GBM patient tissue at University Hospitals-Seidman Cancer Center. Functional assays followed by RNA sequencing were conducted to determine the functional effect of healthy and GBM platelets on growth of patient derived, autologous GSCs. Our clinical studies suggest elevated platelet counts positively correlate with GSC proliferation and negatively correlate with overall survival in patients with GBM. Patients with high platelet counts ( >350k/µl) had a median survival time of 9 months compared to 16 months median survival for patients with normal platelet count (150-350/µl) (p<0.05). We demonstrate platelet and GSC co-localization in GBM solid tissue and platelet exposure to patient derived GSCs cell lines results in a ≥ 3-fold increase in GSC proliferation compared to GSCs not exposed to platelets (p<0.0005). Similarly we found that platelets increased the self-renewing capacity by enhancing the average sphere size (p < 0.005), and increasing the GSC “Stem-like” transcriptional pattern (P< 0.05). Conversely, pharmacologic inhibition of platelet activation reversed the effect of platelets on GSC proliferation (p ranging from 0.05-0.005). These studies suggests the platelet-GSC interactions appear to stimulate GBM oncogenesis, identifying a potential therapeutic target for the treatment of GBM.
CBIO-10. TARGETING HISTONE H4 Lys 20 MONOMETHYLATION IN THE TREATMENT OF GLIOBLASTOMA
Authors: Han Mingzhi , Li Xingang
Published: November 2021

BACKGROUND

Glioblastoma (GBM) is the most malignant primary tumor of the central nervous system, while the pathogenesis remains unclear. Protein lysine methyltransferase SETD8, which is responsible for the modification of histone H4K20me1, has been shown to play an important role in cellular transcriptional regulation and the development of a variety of tumors, yet its role in the malignant progression of GBM has not been elucidated. MATERIAL AND

METHODS

In the present study, we used primary GBM cell lines, intracranial xenograft model, transcriptome sequencing together with ChIP-sequencing, aiming to elucidate the molecular mechanism of SETD8-mediated H4K20me1 transcriptional regulation in promoting GBM progression. Furthermore, we evaluated the potential therapeutic significance in GBM using SETD8 small molecule inhibitor, UNC0379.

RESULTS

We found that SETD8 is aberrantly expressed in GBM tissues, accompanied by the dysregulation of H4K20me1 modification, which is associated with tumor pathology and prognosis. Using SETD8 inhibitor UNC0379 or knockdown of SETD8 significantly inhibited GBM cell proliferation in vitro and in vivo, and downregulated H4K20me1 modification level as well as transcriptome expression.

CONCLUSION

In summary, our work provide a novel insight into the role of SETD8/H4K20me1 axis. SETD8 overexpression mediated aberrant H4K20me1 modification act as a novel "transcriptional switch" in the malignant progression of glioma.
CBIO-11. HISTONE H3.3 G34R/V MUTATIONS STIMULATE PEDIATRIC HIGH-GRADE GLIOMA FORMATION THROUGH THE INDUCTION OF CHROMOSOMAL INSTABILITY
Authors: Day Charles , Grigore Florina , Langfald Alyssa , Hinchcliffe Edward , Robinson James
Published: November 2021

H3.3 G34R/V mutations are drivers of high-grade pediatric glioma (pHGG). H3.3 G34R/V mutations are linked to altered H3.3 K36 trimethylation (H3K36me3); implicating epigenetic gene regulation as a possible contributor to pHGG formation. Here we show that H3.3 G34R/V also induces chromosomal instability (CIN); a hallmark of pHGG. If CIN promotes pHGG formation is unknown. We observed that H3.3 G34 mutant pHGG cells have reduced mitotic H3.3 S31 phosphorylation compare to WT H3.3 cell lines. And, H3.3 G34R reduced Chk1 phosphorylation at S31 by >90% in an in vitro kinase assay. Chk1 regulates chromosome segregation through phosphorylation of pericentromeric H3.3 S31 during early mitosis. Overexpression of H3.3 G34R or non-phosphorylatable S31A in H3.3 WT, diploid cells caused a significant increase in CIN. Likewise, H3.3 G34 mutant pHGG cells have significantly elevated rates of CIN as compare to H3.3 WT pHGG cells. During normal cell division, phospho-S31 is lost in anaphase. However, following chromosome missegregation, phospho-S31 spreads and stimulates p53-induced cell cycle arrest. Here we show that WT p53 cells expressing mutant G34 fail to arrest following chromosome mis-segregation. These studies demonstrate that H3.3 G34R/V mutations are sufficient to transform normal, diploid cells into proliferating CIN cells. To determine if this process contributes to tumorigenesis, we used RCAS Nestin-TVA mice to overexpress H3.3 WT, G34R, or S31A – P2A-linked to PDGFB expression in glial precursor cells of newborn mice. Over 100 days, S31A and G34R mice had drastically reduced survival (averaging 77, 81, and 100 days for S31A, G34R, and WT). Furthermore, most G34R and S31A mice developed HGG, while H3.3 WT mice remained tumor-free. Our work implicates CIN as a driver of H3.3 G34 mutant pHGG formation. Our ongoing studies utilize K36M and double mutants to further define the contributions of S31 phosphorylation (CIN) and H3K36me3 (epigenetic gene regulation) to tumorigenesis.
CBIO-22. PARP INHIBITION SYNERGIZES WITH DNA DAMAGING DRUGS IN PEDIATRIC CNS TUMORS
Authors: Laemmerer Anna , Kirchhofer Dominik , Madlener Sibylle , Loetsch-Gojo Daniela , Jaunecker Carola , Schrempf Anna , Reisecker Johannes , Vician Petra , Gabler Lisa , Mayr Lisa , Loizou Joanna , Slavc Irene , Berger Walter , Gojo Johannes
Published: November 2021

BACKGROUND

Central nervous system (CNS) tumors are the second most common childhood cancer. Despite innovations in surgery and chemo-/radiotherapy, CNS tumors remain the major cause of cancer-related death in children. Previous sequencing analyses in a pediatric cancer cohort identified BRCA and DSB repair signatures as potentially targetable events. Based on these findings, we propose the use of PARP inhibitors (PARPi) for aggressive CNS tumor subtypes, including high-grade glioma (HGG), medulloblastoma (MB) and ependymoma (EPN).

METHODS

We tested multiple PARPi in tumor cell lines (n=8) as well as primary patient-derived models (n=11) of pediatric HGG, MB, EPN and atypical teratoid/rhabdoid tumors (ATRTs). Based on PARPi sensitivity, selected models were further exposed to a combination of PARPi and DNA-damaging/modifying agents. The mode of action was investigated using Western blot and flow cytometry.

RESULTS

We show that a fraction of pediatric MB, EPN and ATRT demonstrate sensitivity towards PARP inhibition, which is paralleled by susceptibility to the DNA damaging drugs cisplatin and irinotecan. Interestingly, talazoparib, the most potent PARPi, showed synergistic cytotoxicity with DNA-damaging/modifying drugs. In addition, cell cycle blockade and increased DNA damage combined with reduced DNA repair signaling, such as activation of the ATR/Chk1 pathway were observed. Corroboratively, talazoparib exhibited a synergistic anti-cancer effect in combination with inhibitors of ATR, a major regulator of DNA damage response.

CONCLUSION/OUTLOOK

To sum up, we demonstrate that PARP inhibition synergizes with DNA damaging anti-cancer compounds or DNA repair inhibitors and, thus, represents a promising therapeutic strategy for a defined subgroup of pediatric high-risk CNS tumors patients. More in depth characterization of the underlying molecular events will most likely allow the identification of predictive biomarkers for most efficient implementation of this strategy into clinical application.
CBIO-28. IDENTIFYING THE ROLE OF MISMATCH REPAIR IN TEMOZOLOMIDE-INDUCED ATR ACTIVATION FOR MGMT-METHYLATED GLIOBLASTOMA MULTIFORME
Authors: Ganesa Sachita , Sule Amrita , Sundaram Ranjini , Bindra Ranjit
Published: November 2021

The methylation status of the O6-methyl guanine methyltransferase (MGMT) gene promoter is a prognostic biomarker for treatment with the alkylator, temozolomide (TMZ) in many solid tumors including gliomas and colorectal cancers. It is well established that patients with a methylated MGMT promoter (MGMT-) who are treated with the TMZ have a better overall survival than patients with an unmethylated MGMT promoter (MGMT+). The enzyme produced by the MGMT gene is responsible for removing cytotoxic O6-methylguanine (O6-meG) lesions formed by TMZ. In the MGMT- setting, the O6-meG lesion activates the mismatch repair (MMR) pathway which functions to remove the damage. Published work from our group reported differential activation of the ataxia telangiectasia and RAD3 related protein (ATR) in MGMT- and MGMT+ glioblastoma multiforme (GBM) cells in response to TMZ treatment, as demonstrated through the phosphorylation of CHK1. Though it is known that MMR proteins are involved in ATR activation, the specific MMR proteins required for ATR activation by TMZ-induced alkyl lesions remain unknown in the MGMT- setting. Here, we demonstrate that specific mismatch repair proteins, including MSH2, MSH6, and PMS2 play a role in ATR activation in the presence of O6-meG lesions. We show that there is potent synergy with ATRi and TMZ in the MGMT- MMR- proficient GBM cell line, which is abrogated in an shMMR MGMT- GBM cell line. Additionally, we observe decreased levels of pCHK1 in the shMMR MGMT- setting compared to the MGMT- MMR-proficient cells, suggesting that MMR is integral in the activation of ATR upon TMZ treatment. Mechanistic understanding of how the MMR system is involved in ATR activation by TMZ can ultimately be exploited for therapeutic gain.
CSIG-03. GBP5 DRIVES MALIGNANCY OF GLIOBLASTOMA
Authors: Li Ming , Chen Clark
Published: November 2021

Guanylate binding proteins (GBPs), a family of interferon-inducible large GTPase, play a pivotal role in cell-autonomous immunity and tumor malignant transformation. Glioblastoma (GBM) is the most prevalent and lethal primary brain tumor in adults. Here we show that GBP5 was highly expressed in GBM cell lines and in clinical samples, especially in the mesenchymal subtype. The expression levels of GBP5 were negatively correlated with the prognosis of GBM patients. Overexpression of GBP5 promoted the proliferation, migration, and invasion of GBM cells in vitro and in vivo. In contrast, silencing GBP5 by RNA interference exhibited the opposite effects. Consequently, targeting GBP5 in GBM cells resulted in impaired tumor growth and prolonged survival time of mice with GBM tumors. We further identified that the Src/ERK1/2/MMP3 axis was essential for GBP5-promoted GBM aggressiveness. These findings suggest that GBP5 may represent a novel target for GBM intervention.
CSIG-14. PTEN AS A SIGNATURE OF VULNERABILITY OF GBM TO NEDDYLATION INHIBITION
Authors: Taylor Brett , Ferdosi Shayesteh , Lee Matthew , Tang Nanyun , Peng Sen , Bybee Rita , Hartman Lauren , Reid George , Garcia-Mansfield Krystine , Sharma Ritin , Pirrotte Patrick , Ma Jianhui , Parisian Alison , Furnari Frank , Dhruv Harshil , Berens Michael
Published: November 2021

Neddylation is a specific pathway within the ubiquitin/proteasome system that is overactive in GBM, and whose upregulation has been associated with glioma progression and worse survival. Pevonedistat (MLN4924) is a first-in-class small-molecule neddylation inhibitor shown to inhibit growth of GBM cells by impacting protein degradation in culture and orthotopic xenografts. However, the determinants of vulnerability are not fully understood. Because the molecular heterogeneity within and across GBM patients obscures therapeutic targets and obfuscates signals of efficacy in clinical trials, we pursue the use of molecular “signatures of vulnerability” to targeted agents in subsets of preclinical models. Selective vulnerability to pevonedistat was shown in a subset of GBM; notably, models with mutations or copy number deletions of PTEN are associated with de novo resistance to pevonedistat. Time-course studies of sensitive and non-sensitive GBM cells using transcriptomics and proteomics/phosphoproteomics uncovered additional determinants of response to pevonedistat. Our results demonstrate that in GBM, resistance to pevonedistat is driven by reduced PTEN-chromatin binding (loss-of-function or lower expression) that is also independent of PTEN’s lipid phosphatase activity (i.e., PI3K/AKT signaling). Across 25 glioma cell lines, we found that PTEN signaling, DNA replication, and chromatin instability pathways are the most significant differentiators between pevonedistat sensitive vs. non-sensitive models. In GBM models with modest to low sensitivity to pevonedistat, TOP2A expression was elevated. Combination treatment with the TOP2A inhibitor, etoposide, proved synergistic with pevonedistat. We report that PTEN status both serves as a novel biomarker for GBM sensitivity to pevonedistat and reveals a synergistic vulnerability to TOP2A inhibitors in combination with pevonedistat. Paired use of GBM PDX models of varying sensitivity with drug development testing allows the advancement of a promising agent as well as a patient-enrollment “signature of vulnerability” likely to increase the likelihood of demonstrating therapeutic efficacy in early stage clinical trials.
RADT-25. PROTON THERAPY FOR YOUNG ADULT MEDULLOBLASTOMA: ACUTE TOXICITY AND DISEASE CONTROL OUTCOMES
Authors: Liu I-Chia , Holtzman Adam , Rotondo Ronny , Indelicato Daniel , Gururangan Sridharan , Cavaliere Robert , Morris Christopher , Tavaniepour Daryoush , Rutenberg Michael
Published: November 2021

BACKGROUND

Report disease control, survival outcomes, and acute radiotherapy related toxicity among young adult medulloblastoma patients who received proton craniospinal irradiation (CSI) as part of multimodality therapy. We reports the completion rates of planned adjuvant chemotherapy.

METHODS

All adult medulloblastoma patients (≥ 22 years old) who received postoperative proton CSI +/- chemotherapy at our institution between 2008 and 2020 were included. Patient, disease, and treatment details along with prospectively obtained patient-reported acute CSI toxicities were collected (CTCAE v3 or v4). Acute hematologic data were analyzed.

RESULTS

Twenty young adult medulloblastoma patients were included. The median age at diagnosis was 27 years (range, 22–30). 45% had high-risk disease. 75% received chemotherapy, most of whom (65%) received post-CSI chemotherapy. Eight patients (40%) received concurrent vincristine with CSI. The median CSI dose was 36 GyE (range, 23.4-36) with a median tumor bed boost of 54 GyE (54-55.8). The median duration of radiotherapy was 44 days (range, 40-49). There were no acute ≥ grade 3 gastrointestinal or hematologic toxicities attributable to CSI (during or within 4 weeks after completion of RT). Grade 2 nausea and vomiting affected 25% and 5% of patients, respectively. Acute grade 2 hematologic toxicity affected 36% of patients. Among patients planned to receive adjuvant chemotherapy (n=13), 100% completed at least 4 cycles and 85% completed all planned chemo cycles. With a median follow-up of 3.1 years, 4-year actuarial local control, DFS, and OS were 90% (95% CI 53-99), 90% (95% CI 53-99), and 95% (95% CI 72-99), respectively. Two patients had disease recurrence, both with local failures in the high dose boost volume in the tumor bed.

CONCLUSIONS

Proton radiotherapy for CSI in young adult medulloblastoma patients is well tolerated and shows promising disease control and survival outcomes. These data support the standard use of proton CSI for adult medulloblastoma.
RADT-27. EFFECTIVENESS ANALYSIS OF RADIOTHERAPY FOR INTRACRANIAL RECURRENT EPENDYMOMA
Authors: Hu Qingjun , Lai Mingyao , Li Juan , Cai Linbo
Published: November 2021

OBJECTIVE

There is no standard treatment for recurrent ependymoma. This study aimed to investigated the role of radiotherapy in recurrent ependymoma.

METHODS

Retrospective analysis was performed on 49 cases of recurrent ependymoma diagnosed in Guangdong Sanjiu Brain Hospital from January 2008 to July 2020. Overall survival (OS) was calculated by Kaplan-Meier method and tested by Log-rank test. P < 0.05 was considered statistically significant.

RESULTS

The median age was 7 years (range:1-57 yrs). Nineteen patients were with ependymoma WHO grade II while 30 were with grade III, respectively. Recurrence treatment: 14 cases received re-surgery, 23 cases received radiotherapy, among them 16 cases received re-radiotherapy. To May, 2021, the median follow-up time was 35 months (range 3-153). Median PFS time was 17 months after initial diagnosis, median PFS time was 8 months after treatment to recurrence disease, Median OS time is 39 months, and median OS time is 20 months after recurrence. The median survival time for recurrence was 48 months vs. 11 months (P =0.001) in the radiotherapy group vs. non-radiotherapy group,res; Re-radiotherapy combined with chemotherapy vs reradiotherapy alone (0.194); RRT combined with anti-angiogenesis therapy vs. RRT alone (0.688).

CONCLUSION

Radiotherapy can prolong the survival time of recurrent ependymoma, and concurrent therapy as chemotherapy or anti-angiogenesis therapy with RT does not seem to improve the prognosis. Therefore, radiotherapy can be used as the main treatment for recurrent ependymoma.
RADT-35. CHANGE IN HIPPOCAMPAL VOLUME AS A FUNCTION OF RADIATION DOSE: RESULTS FROM A PROSPECTIVE TRIAL WITH STANDARDIZED IMAGING AND MORPHOMETRIC EVALUATION
Authors: Hall Matthew , Odia Yazmin , Niazi Toba , Naidoo Reshma , Alamdari Golnar , Kotecha Rupesh , Tom Martin , Mohler Alexander , Wroe Andrew , Yu Jen , Von Werne Katherine , Gallardo Laura , Walters Rameen , Abrams Kevin , Altman Nolan , Medina Santiago , Chuong Michael , Mehta Minesh
Published: November 2021

PURPOSE/OBJECTIVES

MRIs in pediatric and adult brain tumor patients (Age< 35) were prospectively collected at baseline and during follow-up to measure volumetric changes in multiple brain substructures with neurocognitive, laboratory, and quality-of-life assessments. In this planned interim analysis, we model early outcomes for change in hippocampal volume at 6 months following radiotherapy.

MATERIALS AND METHODS

As of 5/15/2021, 50 patients enrolled on this prospective study and 41 completed 6-month post-treatment assessments after fractionated intensity-modulated proton therapy. Left and right hippocampus volumes were independently measured on T1 sagittal precontrast MRI at baseline and 6-months after radiotherapy using both automated software and physician-delineated contours. The relationship between mean hippocampus dose and change in volume was assessed by Pearson’s correlation coefficient. A linear mixed-effects model was applied to evaluate other predictors associated with change in hippocampal volume, assuming random effects of subjects.

RESULTS

Mean hippocampus dose was strongly correlated with change in hippocampal volume at 6 months following radiotherapy (r=−0.727, 95% CI [-0.820,-0.596], p< 0.001). Changes in hippocampal volumes over time were similar between software and physician contours. Hippocampal volume was significantly reduced for mean doses ≥10 Gy (mean Δ -10.8% ± 5.5%, p< 0.001), while no significant volume change was observed with mean doses < 10 Gy (mean Δ +0.7% ± 3.9%). In the mixed-effects model, only mean hippocampus dose was significantly associated with hippocampal volume change (p< 0.001). The final model predicted a -3.4% change in hippocampal volume for every 10 Gy increase in mean dose.

CONCLUSIONS

Change in hippocampal volume was correlated with hippocampus mean dose at 6 months following radiotherapy. Future analyses will assess volume change in the hippocampus and other brain substructures over time as a function of radiation dose and correlate with measured neurocognitive and other effects.
CTIM-01. PHASE II TRIAL OF PEMBROLIZUMAB AND LENVATINIB FOR LEPTOMENINGEAL METASTASES
Authors: Wang Nancy , Gerstner Elizabeth , Cahill Daniel , Oh Kevin , Cahill Jennifer , Brastianos Priscilla
Published: November 2021

Leptomeningeal metastasis (LMD) is a late complication of cancer with poor prognosis and median survival of approximately 4-6 weeks without treatment. Whole brain radiation remains the mainstay of treatment, however it can cause significant neurocognitive sequelae and has not been shown to prolong overall survival. Thus, new treatment strategies are urgently needed to improve outcomes in patients with LMD. Results from recent Phase 2 studies of immune checkpoint inhibitors in LMD shows promising improvement in overall survival. Combining anti-VEGF therapy and immunotherapy may control symptoms due to inflammation and tumor-induced irritation, minimize steroid use, and promote improved efficacy of immunotherapy through modulation of the tumor immune microenvironment. We designed a multi-institutional, single-arm Phase 2 study of pembrolizumab in combination with lenvatinib in patients with LMD from any solid tumor. The primary objective is to estimate the overall survival rate at 6 months (OS6). A Simon two-stage design with a total sample size of 19 evaluable patients will be used to compare a null hypothesis of OS6 of 25% against an alternative hypothesis of 55%. Secondary objectives include assessing safety of pembrolizumab and lenvatinib in this patient population, systemic response rate, intracranial/intraspinal response rate, and progression-free survival. We will also explore clinician-reported neurologic outcomes and patient-reported quality of life and symptom burden. Blood, cerebrospinal fluid, and tissue biomarkers will be analyzed to determine predictors of response. Patients must be on minimal doses of steroids prior to study enrollment and cannot have received prior immune checkpoint inhibitor or anti-VEGF therapy. Response to treatment will be determined using RANO-BM for intracranial disease and RECIST 1.1 for systemic disease. Study accrual is anticipated over 12-24 months with anticipated total study duration of 30 months.
CTIM-06. CLINICAL EFFICACY AND BIOMARKER ASSESSMENT OF VT1021, A CD36/CD47 DUAL-TARGETING AGENT, IN RECURRENT GLIOBLASTOMA
Authors: Ahluwalia Manmeet , Battiste James , Bockorny Bruno , Bullock Andrea , Patel Manish , Wen Patrick , Shepard Dale , Vaickus Lou , Vincent Melanie , Chen Jian jenny , Wang Suming , Watnick Randolph , Crochiere Marsha , Cieslewicz Michael , Watnick Jing
Published: November 2021

Glioblastoma (GBM) is the most common and aggressive primary brain malignancy in adults and recurs after treatment in >90% of all patients. Prognosis of patients with recurrent GBM (rGBM) is poor with a median progression free survival of ~1.8 months and median overall survival of 8-10 months. VT1021, a cyclic peptide derived from prosaposin, induces the expression of thrombospondin-1 (TSP-1) in myeloid derived suppressor cells (MDSCs), which are heavily recruited to the tumor microenvironment. Following completion of the Phase 1 Dose Escalation study and determination of the RP2D, an expansion study was conducted in a heavily pretreated rGBM population. The results of the expansion study reveal that VT1021 is safe and well tolerated in rGBM. Pharmacodynamic response to VT1021 was observed by induction of TSP-1 in circulating MDSCs and in the tumor microenvironment. VT1021 demonstrated significant single agent activity. Among 22 evaluable GBM subjects, 3 had complete response (CR), 1 had partial response (PR), and 7 had stable disease (SD) with an average study duration of over 120 days. The overall disease control rate (DCR) was 50%. Among the 3 CR, 2 showed complete radiological regression of the target lesion, the third was found to have no evidence of disease upon pathological examination following surgery. Nine of the 19 (47%) evaluable subjects with available biopsy samples showed high expression levels of both CD36 AND CD47. Among these 9 subjects, 3 achieved CR, representing an overall response rate of 33.3%, with another 3 patients achieving SD for a DCR of 67%. In conclusion, VT1021 demonstrates promising single-agent clinical activity in rGBM, particularly in subjects with high expression levels of CD36 and CD47. Additional clinical studies have been planned to further investigate the efficacy of VT1021 in rGBM and other solid tumor indications.
CTIM-12. A PHASE 1 TRIAL OF IMMUNORADIOTHERAPY WITH THE IDO ENZYME INHIBITOR (BMS-986205) AND NIVOLUMAB IN PATIENTS WITH NEWLY DIAGNOSED MGMT PROMOTER UNMETHYLATED IDHwt GLIOBLASTOMA
Authors: Lukas Rimas , Sachdev Sean , Kumthekar Priya , Dixit Karan , Grimm Sean , Gondi Vinai , Sharp Laura , Lezon Ray , James David , Lesniak Maciej , Stupp Roger , Wainwright Derek
Published: November 2021

BACKGROUND

IDHwt glioblastoma with unmethylated MGMT gene promoter carries a poor prognosis. Preclinical studies have shown that combination of radiotherapy and dual immunotherapy with nivolumab and IDO inhibition significantly prolongs survival of mice with an orthotopic glioblastoma [Ladomersky, et al. CCR 2018;24(11):2559-2573]. In a clinical trial in patients with newly diagnosed glioblastoma with unmethylated MGMT we substituted temozolomide for dual immunotherapy combination.

METHODS

Phase 1 trial [NCT04047706] using a 3 + 3 dose-escalation design. All received standard radiotherapy (30 x 2 Gy) with addition of once daily oral BMS-986205 and intravenous nivolumab (240mg every 2 weeks) begining on day 1 of radiotherapy and continuing until disease progression or intolerance. BMS-986205 dosing was increased from 50 mg to 100 mg. DLT period encompasses 6 weeks of radiotherapy and the 4 subsequent weeks. Immunocorrelatives being conducted before and after treatment include mass spectrometry for tryptophan and kynurenine levels, immunohistochemistry of resected tumor, and RNA-sequencing and flow cytometric analysis of PBMCs.

RESULTS

Twelve patients were treated on 2 dose levels of BMS-986205 (50, 100 mg). Treatment-emergent toxicity was as expected for this population. Three (25%) treatment-related SAEs were reported. Dose limiting toxicity of grade 3 transaminase elevation was observed in 2 patients at the 100 mg dose level, while at lower doses of BMS-986205 no substantial alterations of liver enzymes was observed. No other relevant treatment related toxicity occured. Ongoing immunocorrelative profiling and preliminary outcome data (all patients minimal follow-up >12 months) will be available at the time of the meeting.

CONCLUSIONS

Dose limiting toxicity of BMS-986205 in combination with nivolumab and radiotherapy is hepatic (reversible) transaminitis. The recommended dose for further investigation is 50 mg. Accrual is ongoing for the MGMT promoter methylated cohort using the same regimen without withholding temozolomide. A randomized phase 2/3 trial is approved within the NRG network.
CTIM-16. PHASE 2 STUDY OF PEMBROLIZUMAB PLUS TTFields PLUS TEMOZOLOMIDE IN PATIENTS WITH NEWLY DIAGNOSED glioblastoma (2-THE-TOP)
Authors: Tran David , Ghinaseddin Ashley , Chen Dongjiang , Rahman Maryam
Published: November 2021

INTRODUCTION

Emerging data indicate that TTFields, the new anti-mitotic treatment for GBM, stimulate immunity via the type-1 interferon (T1IFN) pathway of STING and AIM2 inflammasomes. Thus, we hypothesize that TTFields synergize with immune checkpoint inhibitors to induce anti-tumor immunity in GBM.

METHODS

We conduct a phase 2 study combining pembrolizumab, TTFields and maintenance TMZ in 25 patients with newly diagnosed GBM (ndGBM). To distinguish immune effects of TTFields from pembrolizumab, TTFields is started at cycle 1 of TMZ and pembrolizumab (200mg Q3Wks) at cycle 2. The primary endpoint is PFS vs. the historical control of TTFields plus TMZ (JAMA/318:2306-2316). Secondary endpoints include toxicity, immune signature of TTFields vs. pembrolizumab by single-cell RNAseq of PBMCs, and OS.

RESULTS

As of 05/24/2021, 25 patients with a median age of 61 years were enrolled. Eight (32%) and 4 (16%) had biopsy only and partial resection, respectively. Eighteen (72%) had unmethylated MGMT and 3 (12%) had an IDH mutation. The median follow-up was 14.7 months. Twelve (48%) were progression-free, and 15 (60%) were alive. Of 19 patients with follow-up >=9 months, the median PFS was >=11.2 months vs. 6.7 months in the control. Six (24%) patients with measureable tumors achieved partial to complete response. The most common serious adverse events were thrombosis, seizure, and metabolic disturbances in 4 (16%), 3 (12%), and 2 (8%) patients, respectively. We sequenced 193,760 PBMCs in 12 patients before pembrolizumab and detected robust post-TTFields T cell activation in 11 of 12 patients via the T1IFN trajectory with a strong correlation with the TCRab clonal expansion Simpson index (Spearman coefficient r=-0.8, P=0.014). Importantly, we defined a T cell-based gene signature of TTFields effects on TCRab clonal expansion.

CONCLUSION

The triple combination is well tolerated and shows early evidence of efficacy in ndGBM patients. Survival and molecular data will be updated.