bluuebunny/crossref_metadata_2025 huggingface dataset:
CTIM-27. LOCOREGIONAL B7-H3-SPECIFIC CAR T CELLS FOR CHILDREN AND YOUNG ADULTS WITH DIPG: INTERIM REPORT OF BRAINCHILD-03 ARM C
Authors: Vitanza Nicholas , Wilson Ashley , Yokoyama Jason , Johnson Adam , Gust Jule , Huang Wenjun , Albert Catherine , Pinto Navin , Foster Jessica , Orentas Rimas , Paulovich Amanda , Berens Michael , Gardner Rebecca , Jensen Michael , Park Julie
Published: November 2021

Following preclinical optimization of B7-H3-specific CAR T cells against pediatric brain tumor models, we opened BrainChild-03 (NCT04185038), a phase 1 clinical trial of repeatedly dosed, outpatient, locoregional B7-H3-specific CAR T cells for children with recurrent/refractory central nervous system (CNS) tumors or diffuse intrinsic pontine glioma (DIPG). Here, we report the interim findings from patients enrolled on Arm C, dedicated to DIPG. The primary endpoints are feasibility and safety, with secondary endpoints of disease response. We utilize second-generation CAR T cells with a 4-1BB costimulatory domain and a methotrexate-resistant human DHFR mutein (huDHFRFS; L22F,F31S), allowing for methotrexate selection. We do not deliver conditioning chemotherapy. The first three evaluable patients with DIPG all met feasibility for generating a balanced CD4:CD8 CAR T cell product, with 3.85x109 CAR T cells generated for S005, 4.29x109 for S008, and 2.45x109 for S012, allowing for greater than 6 months of biweekly dosing for each patient. All subjects were treated at Dose Level 1 (1x107 CAR T cells). S005 received 10 doses before clinical progression greater than 2 years from diagnosis, S008 has received 10 doses and continues on therapy with decreased tumor volume, and S012 has received 5 doses and continues on study with stable disease. There have been no dose limiting toxicities (DLT). 3/3 patients exhibited post infusion fever, headache, and elevated serum CRP but no evidence of cytokine release syndrome (CRS) or systemic CAR T cells. 0/3 patients required PICU admissions. In the cerebrospinal fluid (CSF), 2/3 patients have had elevations of cytokines such as CXCL10 and CCL2, as well as circulating CSF CAR T cells. Advanced serial patient CSF proteomic and transcriptomic profiling are underway. Ultimately, this report provides preliminary evidence that outpatient locoregional B7-H3 CAR T cells for children with DIPG may be feasible and tolerable.
CTIM-28. MDNA55, AN INTERLEUKIN-4 RECEPTOR TARGETED IMMUNOTHERAPY, FOR RECURRENT GBM DELIVERED BY CONVECTION ENHANCED DELIVERY (CED)
Authors: Sampson John , Achrol Achal Singh , Aghi Manish K , Bankiewiecz Krystof , Bexon Martin , Brem Steven , Brenner Andrew , Chandhasin Chandtip , Chowdhary Sajeel , Coello Melissa , Ellingson Benjamin , Floyd John , Han Seunggu , Kesari Santosh , Merchant Fahar , Merchant Nina , Randazzo Dina , Vogelbaum Michael , Vrionis Frank , Zabek Miroslaw , Butowski Nicholas
Published: November 2021

BACKGROUND

MDNA55 is an IL4R-targeted toxin in development for treatment of recurrent glioblastoma (rGBM). MDNA55 binds to IL4R expressed by tumor cells and non-malignant cells of the tumor microenvironment.

METHOD

MDNA55-05 was an open-label, single-arm study of MDNA55 delivered by CED as a single treatment in patients with 1st or 2nd recurrence following de novo GBM, IDH wild type status and not indicated for resection at relapse. Dose volumes (up to 60mL) and concentration of MDNA55 (1.5 to 9.0 μg/mL) were studied.

RESULTS

MDNA55 showed an acceptable safety profile at all doses tested. Median OS (mOS) amongst all subjects was 11.9 months, OS-24 was 20%, and PFS-12 was 27%. Among subjects expressing high levels of IL4R (irrespective of MDNA55 dose) and low levels of IL4R expression administered high dose (≥ 180μg) of MDNA55 (IL4Rhi + IL4Rlo/hd), mOS further improved to 14.0 months with OS-24 of 20%. Unmethylated MGMT promoter status did not affect MDNA55 treatment outcomes. In the IL4Rhi + IL4Rlo/hd population (N=17), mOS was 14.9 months with OS-24 of 22%. Following treatment with high concentrations of MDNA55 (6.0 or 9.0 μg/mL), transient (median of 3 cycles) low dose Avastin (5mg/kg q2w or 7.5mg/kg q3w) was used for symptom control and steroid sparring. Among these subjects, mOS amongst all comers (N=9) and the IL4Rhi + IL4Rlo/hd group (N=8) increased to 21.8 and 18.6 months with OS-24 of 44% and 38%, respectively.

CONCLUSIONS

MDNA55 shows potential to benefit all rGBM patients treated at high dose irrespective of IL4R expression. In the 1:1 randomized Phase 3 trial, the study will enrol two-thirds of subjects in the SOC arm from a matched external control arm. Unlike conventional RCTs, the hybrid design sets a new precedent for GBM trials, allowing robust OS analysis while significantly reducing the number of subjects randomized to SOC arm.
CTNI-17. A PHASE 1 WITH DOSE EXPANSION/PHASE 2 STUDY OF SELINEXOR IN COMBINATION WITH STANDARD OF CARE THERAPY FOR NEWLY DIAGNOSED OR RECURRENT GLIOBLASTOMA
Authors: Odia Yazmin , Wen Patrick , Mehta Minesh , Colman Howard , Dunbar Erin , Butowski Nicholas , Harrison Rebecca , Schulder Michael , Boockvar John , Chow Frances , Kumthekar Priya , Mason Warren , Venur Vyshak , Plotkin Scott , Lassman Andrew , Duic Paul , Tamir Sharon , Li Kai , Liu Yang , Mundy Gregory , Damestani Yasaman , Sbar Eric , Shah Jatin , Shacham Sharon , Goldlust Samuel
Published: November 2021

BACKGROUND

Glioblastoma (GBM) is the most common and aggressive primary brain tumor with median overall survival of 15 months and 5-7 months for patients with newly diagnosed or recurrent disease (nGBM or rGBM), respectively. Selinexor is a first-in-class, oral, selective inhibitor of nuclear export which blocks exportin 1 (XPO1), forcing the nuclear retention and reactivation of tumor suppressor proteins, ultimately causing cancer cell death. Increased XPO1 expression in gliomas is associated with higher pathological grade and poorer prognosis. Consistent with these data, selinexor inhibited tumor growth and prolonged survival in an animal model of GBM. Importantly, selinexor showed encouraging intra-tumoral penetration and single-agent efficacy in rGBM (KING study). The current trial tests the hypothesis that adding selinexor to standard therapy will improve clinical outcomes for patients with nGBM or rGBM.

METHODS

To facilitate the successful development of new therapies, consensus recommendations are to use biomarker enrichment and flexible design that allows expansion of promising cohorts. Accordingly, this phase 1a dose finding study is followed by a phase 1b dose expansion (and ultimately by a 1:1 randomized phase 2 efficacy exploration trial) to independently evaluate: radiation + selinexor in nGBM with unmethylated MGMT promoter (Arm A), radiation + temozolomide + selinexor for nGBM with methylated MGMT promoter (Arm B), and lomustine + selinexor in rGBM (Arm C). Bevacizumab or TTField + selinexor in rGBM (Arms D & E, respectively) are being considered. The Phase 1a primary endpoint is maximum tolerated dose/recommended phase 2 dose. The phase 1b primary endpoint is PFS at 3 months against historic controls. The phase 1b dose expansion is included to evaluate preliminary efficacy before launching into a randomized phase 2 trial. Patient quality of life during the trial will be objectively measured using digital devices (e.g. smartwatch/customized smartphone app). We are currently enrolling patients nationwide. Clinical Trial Registration number: NCT04421378.
CTNI-36. SAFETY OF ONC201 ADMINISTERED TWO CONSECUTIVE DAYS PER WEEK IN PEDIATRIC H3 K27M-MUTANT GLIOMA PATIENTS
Authors: Gardner Sharon , Koschmann Carl , Tarapore Rohinton , Allen Jeffrey , Zaky Wafik , Odia Yazmin , Hall Matthew , Daghistani Doured , Khatib Ziad , Aguilera Dolly , MacDonald Tobey , de Blank Peter , McGovern Susan , Mueller Sabine , Kline Cassie , Vitanza Nicholas , Allen Joshua , Khatua Soumen
Published: November 2021

ONC201, an anti-cancer DRD2 antagonist and ClpP agonist, is in Phase II trials for adult H3 K27M-mutant diffuse midline gliomas. The recommended phase 2 dose (RP2D) of 625mg ONC201 once a week has been established as a biologically active dose that is well tolerated in adult and pediatric populations. Radiographic regressions with single agent ONC201 have been reported in recurrent H3 K27M-mutant glioma patients. In another study, twice/week dosing was explored in adult patients and deemed to be safe (no DLTs observed). This warranted exploration of twice/week dosing in pediatric patients and will be discussed in this presentation. This multi-arm, dose-escalation and dose-expansion trial (ONC014; NCT03416530) determined the pediatric RP2D of ONC201 administered once per week and twice per week on two consecutive days. ONC201 was orally administered and scaled by body weight. Dose escalation was performed by a 3 + 3 design beginning with two 125mg capsules less than the adult RP2D equivalent. Twelve children (8 females; 4 males) with H3 K27M-mutant gliomas (pons: 8; thalamus: 2; spinal cord: 2) aged 4-19 years have been treated post-radiation: 3 at dose level -1; 3 at dose level 1; 6 as part of the dose expansion cohort on dose level 2. Median KPS was 90 (range 70-100). One treatment cycle was 21 days (6 doses), which also defined the DLT window. Patients were on-treatment for a median length of 4 cycles (range: 2-11). Twice weekly dosing of ONC201 was tolerated well, as observed with weekly dosing, with no instance of DLT. A total of 4 SAEs were reported, none of which were related to the study drug. The most common AEs (regardless of relatedness) included headache, facial nerve disorder, abducens nerve disorder, nausea, fatigue and ataxia. Additional safety data, PK, and clinical outcomes from this arm will be reported.
CTNI-40. EVALUATING FEASIBILITY AND EFFICIENCY OF PHASE II ADAPTIVE PLATFORM TRIAL DESIGNS BASED ON THE INDIVIDUALIZED SCREENING TRIAL OF INNOVATIVE GLIOBLASTOMA THERAPY (INSIGhT) EXPERIENCE
Authors: Rahman Rifaquat , Trippa Lorenzo , Lee Eudocia Quant , Arrillaga-Romany Isabel , Touat Mehdi , Fell Geffrey , McCluskey Christine , Bruno Jennifer , Gaffey Sarah , Drappatz Jan , Lassman Andrew , Galanis Evanthia , Ahluwalia Manmeet , Colman Howard , Nabors L Burt , Hepel Jaroslaw , Elinzano Heinrich , Schiff David , Chukwueke Ugonma , Beroukhim Rameen , Batchelor Tracy , Nayak Lakshmi , McFaline-Figueroa J Ricardo , Rinne Mikael , Kaley Thomas , Lu-Emerson Christine , Bi Wenya Linda , Arnaout Omar , Haas-Kogan Daphne , Tanguturi Shyam , Cagney Daniel , Aizer Ayal , Welch Mary , Doherty Lisa , Lavallee Maria , Fisher-Longden Brittany , Dowling Shanna , Pisano William , Lapinskas Emily , Meredith David , Chiocca E Antonio , Reardon David , Ligon Keith , Alexander Brian , Wen Patrick
Published: November 2021

BACKGROUND

The Individualized Screening Trial of Innovative Glioblastoma Therapy (INSIGhT) is a phase II platform trial with Bayesian adaptive randomization and deep genomic profiling to more efficiently test experimental agents in newly diagnosed glioblastoma and to prioritize therapies for late-stage testing.

METHODS

In the ongoing INSIGhT trial, patients with newly diagnosed MGMT-unmethylated glioblastoma are randomized to the control arm or one of three experimental therapy arms (CC-115, abemaciclib, and neratinib). The control arm therapy is radiotherapy with concomitant and adjuvant temozolomide, and primary endpoint is overall survival. Randomization has been adapted based on Bayesian estimation of biomarker-specific probability of treatment impact on progression-free survival (PFS). All tumors undergo detailed molecular sequencing, and this is facilitated with the companion ALLELE protocol. To evaluate feasibility of this approach, we assessed the status of this ongoing trial.

RESULTS

Since INSIGhT was activated 4.3 years ago, it has expanded to include 12 sites across the United States. A total of 247 patients have been enrolled. Randomization probabilities have been repeatedly adjusted over time based upon early PFS results to alter the randomization ratio from standard 1:1:1:1 randomization. All three arms have completed accrual and efficacy estimates are available based upon comparison to the common control arm in context of relevant biomarkers. There are 87 patients alive and in follow-up, and there are ongoing plans to add additional arms to evaluate further treatments in the future.

CONCLUSION

The INSIGhT trial demonstrates that a multi-center Bayesian adaptive platform trial is a feasible and effective approach to help prioritize therapies and biomarkers for newly diagnosed GBM. The trial has maintained robust accrual, and the simultaneous testing of multiple agents, sharing a common control arm and adaptive randomization serve as features to increase trial efficiency relative to traditional clinical trial designs.
CTNI-43. CXCL12 INHIBITION IN MGMT UNMETHYLATED GLIOBLASTOMA – RESULTS OF AN EARLY PROOF-OF-CONCEPT ASSESSMENT IN THE MULTICENTRIC PHASE I/II GLORIA TRIAL (NCT04121455)
Authors: Giordano Frank , Layer Julian , Leonardelli Sonia , Friker Lea , Seidel Clemens , Zeyen Thomas , Schaub Christina , Sperk Elena , Sahm Katharina , Kebir Sied , Hambsch Peter , Pietsch Torsten , Glas Martin , Bisdas Sotirios , Hölzel Michael , Herrlinger Ulrich
Published: November 2021

BACKGROUND

Preclinical studies showed that CXCL12-mediated influx of highly angiogenic monocytes/macrophages is a key driver of tumor re-vascularization and re-growth after radiotherapy (RT) of glioblastoma (GBM). We report findings from a phase I/II proof-of concept (PoC) study on CXCL12 inhibition during and after RT of GBM.

METHODS

Patients ≥18years with incompletely or unresected GBM without MGMT promoter hypermethylation and ECOG≤2 were eligible to participate. Patients received continuous (24/7) i.v. infusions of 200mg/week (n=3), 400mg/week (n=3) or 600mg/week (n=3) of the CXCL12 inhibitor olaptesed pegol (OLA) for 26 weeks during and after normo- or hypofractionated RT (60Gy/40.05Gy). The primary endpoint was safety as per the incidence of treatment-related adverse events. The study was accompanied by PoC-research including multiparametric MRI biomarkers (relative cerebral blood volume, rCBV; fractional tumor burden with high perfusion, FTBhigh; apparent diffusion coefficient, ADC) and of multiplexed immunofluorescence imaging (CODEX®) of reference and patient samples. Initial results of these analyses are reported for the first six patients enrolled.

RESULTS

Five of six (83%) patients assessed with advanced MRI showed response under OLA in rCBV/FTBhigh and ADC. Maximum reduction in perfusion (rCBV) from baseline was 55%, maximum reduction of FTBhigh was 55% and maximum increase in ADC was 77%. Furthermore, five of six (83%) patients analyzed showed reduction of enhancing tissue volumes in at least one scan under OLA therapy. In both one patient and two reference samples CXCL12 co-localized with endothelial cells of the microvascular proliferation zone. In a paired sample (before/during OLA) of one patient, endothelial cells stained positive for CXCL12 before but not during treatment and almost all GBM cells were negative in Ki67 staining in the sample obtained under OLA therapy.

CONCLUSIONS

Advanced MRI and multiplexed immunofluorescence suggest efficacy of combined radiotherapy and CXCL12 inhibition in unmethylated GBM.

Funded by NOXXON Pharma AG; ClinicalTrials.gov number, NCT04121455.
CTNI-47. INTERIM RESULTS OF NCT03011671: A MULTI-INSTITUTIONAL PHASE I STUDY OF ACETAZOLAMIDE WITH TEMOZOLOMIDE IN ADULTS WITH NEWLY DIAGNOSED MGMT-METHYLATED MALIGNANT GLIOMA
Authors: Yamini Bakhtiar , Lyne Seán , Driscoll Riley , Bernal Giovanna , Wu Longtao , NIcholas Martin , Chmura Steve , Collins John , Park Deric , Pytel Peter , Karrison Theodore , Stupp Roger , Grimm Sean , Gondi Vinai , Merrell Ryan , Lukas Rimas
Published: November 2021

Preclinical studies indicate that up-regulation of carbonic anhydrase (CA) by temozolomide (TMZ), via a mechanism requiring the proto-oncogene BCL-3, promotes resistance to therapy in glioblastoma (GBM) cells. Moreover, the CA inhibitor, acetazolamide (ACZ), sensitizes patient-derived GBM cells and xenografts to TMZ. These findings led to the current Phase I study investigating the safety and efficacy of adding ACZ to adjuvant TMZ in patients with newly diagnosed, MGMT-methylated malignant glioma. 24 patients were enrolled (23 GBM and one Grade III IDH-mutant astrocytoma), median age was 53.5 and mean KPS 91. ACZ was given on days 1-21 of each adjuvant TMZ cycle (250 mg BID days 1-7, increased to 500 mg BID days 8-21). No patient experienced the primary outcome of regimen limiting toxicity (RLT) and there were only three grade III adverse events deemed likely unrelated to ACZ. For the secondary endpoints of overall and progression free survival (OS and PFS, respectively), only the 23 GBM patients were included (22 IDH-wildtype and 1 IDH-mutant). From diagnosis, median PFS was 18.8 months (95% CI: 10.4-23.0) and median OS was 25.0 months (95% CI: 19.9-28.4). Median time from diagnosis to consent was 2.9 months. As of April 2021, only 7 of 23 deaths had occurred. 2-year OS% was 68.2%. Further analysis of secondary endpoints including 6-month objective response rate (ORR) and biomarker analysis of BCL-3 by IHC will be available in the coming months. In sum, the data indicate that addition of ACZ to TMZ is safe and does not lead to reduced TMZ dosing. Also, compared to historical data, interim outcomes suggest that addition of ACZ may substantially improve PFS and 2-year overall survival. These findings support the hypothesis that ACZ acts as a chemosensitizer of alkylating chemotherapy in GBM and support examination of this regimen in a randomized, placebo-controlled study.
CTNI-48. A PHASE 0 ‘TRIGGER’ TRIAL OF CDK4/6 PLUS ERK1/2 INHIBITORS IN RECURRENT GLIOBLASTOMA
Authors: Sanai Nader , Chang Yu-Wei , Margaryan Tigran , DeSantis Anita , Elliott Mackenna , Pennington-Krygier Chelsea , Hook Garry , Yoo Wonsuk , Tien An-Chi , Tovmasyan Artak , Mehta Shwetal
Published: November 2021

BACKGROUND

This dual-drug Phase 0 study (NCT04391595) evaluates the tumor pharmacokinetics (PK) and tumor pharmacodynamics (PD) of abemaciclib, a selective CDK4/6-inhibitor, plus LY3214996, a selective ERK1/2 inhibitor, in recurrent GBM patients.

METHODS

Adult recurrent GBM patients (n=10) with intact RB expression, > 30% pERK expression, and CDKN2A/B deletion or CDK4/6 amplification received six days of abemaciclib (150mg BID) plus LY3214996 (200mg QD) prior to a planned resection at 3-5 or 7-9 hour time interval after the final drug dose in a Time-Escalation Arm. Tumor tissue (gadolinium [Gd]-enhancing and nonenhancing regions), cerebrospinal fluid (CSF), and plasma were collected. Total and unbound drug concentrations were measured using validated LC-MS/MS methods. Tumor PD effects, including RB and RSK phosphorylation, were compared to matched archival or pre-treatment biopsied tissue. A PK ‘trigger’ (i.e., unbound concentration > 5x biochemical IC50) was set for each drug. Gd-nonenhancing tumor tissue exhibiting abemaciclib and LY3214996 concentrations in excess of their trigger threshold qualified patients for postoperative dual-drug therapy.

RESULTS

No dose-limiting toxicities were observed. In Gd-nonenhancing tumor regions, median unbound concentrations of abemaciclib were 31.2 nM (3-5 hour cohort) and 25.1 nM (7-9 hour cohort) while median unbound concentrations of LY3214996 were 52.0 nM (3-5 hour cohort) and 10.2 nM (7-9 hour cohort). Tumor RB and RSK phosphorylation decreased in 6/10 and 2/10 patients, respectively. Tumor proliferation (MIB-1) was decreased in 8/10 patients. 5/10 patients exceeded PK thresholds for both abemaciclib (12 nM) and LY3214996 (25 nM), thereby entering the study’s therapeutic expansion phase.

CONCLUSION

Abemaciclib and LY3214996 achieve pharmacologically-relevant concentrations in Gd-non-enhancing GBM tissue and are associated with suppression of RB pathway and tumor proliferation. The Optimal Time Interval (OTI) for tissue sampling was 3-5 hours after the final drug dose. Based on this interim analysis, the trial will accrue an additional 25 patients at this OTI.
CTNI-53. RADIATION TREATMENT VOLUMES BEFORE AND AFTER BRAF/MEK THERAPY IN NEWLY DIAGNOSED PAPILLARY CRANIOPHARYNGIOMAS: A CORRELATIVE ANALYSIS OF THE ALLIANCE A071601 PHASE II TRIAL
Authors: Shih Helen , Tabrizi Shervin , Kabat Brian , Twohy Erin , Geyer Susan , Vora Shivangi , Gerstner Elizabeth , Kaufmann Timothy , Ruff Michael , Reardon David , Cohen Adam , Bota Daniela , Agarwalla Pankaj , De la Fuente Macarena , Lesser Glen , Campian Jian , Kumthekar Priya , Knopp Michael , Cahill Daniel , Santagata Sandro , Barker Fred , Galanis Evanthia , Brastianos Priscilla , Brown Paul
Published: November 2021

PURPOSE

Standard of care for craniopharyngiomas is surgery with or without radiotherapy (RT). Cohort A of Alliance A071601 evaluated the efficacy of BRAF/MEK inhibition with vemurafenib/cobimetinib in patients with previously untreated papillary craniopharyngiomas (PCP), which carry the BRAF V600E mutation. Cohort B is currently enrolling patients with recurrence after RT. In a correlative analysis, we examined changes in RT volumes after BRAF/MEK therapy in Cohort A.

METHODS

Previously unirradiated patients with BRAF-mutated PCP were treated with vemurafenib/cobimetinib. Sixteen patients had scans available before starting vemurafenib/cobimetinib (“pre-therapy”) and after completing therapy (“post-therapy”). Two patients went off study treatment after 8 and 9 days due to side-effects and were excluded for this analysis. Gross target volumes (GTV) were contoured on pre-therapy and post-therapy scans. On post-therapy scans, an additional target comprising gross disease and at-risk regions for microscopic residual disease (GTV-micro) was defined and considered the treatment volume. Clinical target volume (CTV) was a 5-mm uniform expansion on pre-therapy GTV and post-therapy GTV-micro. Volumes were independently reviewed by two radiation oncologists. Changes in volumes from pre- versus post-therapy were compared using the Wilcoxon signed rank test.

RESULTS

In 14 patients evaluated, 57% were female and median age at enrollment was 49.5 years (range 33-83). Median time on treatment was 8.9 months (range 4.0-18.0). Median GTV pre-therapy was 3.8 mL (range 0.2-23.4) versus 0.3 mL (range 0.0-3.2) post-therapy (p=0.0001) and 1.7 mL (range 0.1-8.0) post-therapy GTV-micro (p=0.0001). Median CTV pre-therapy was 13.7 mL (range 2.8-51.8) versus 9.1 mL (range 2.2-27.5) post-therapy (p=0.0001). All tumors abutted the optic chiasm pre-therapy, only 6 did post-therapy.

CONCLUSIONS

Vemurafenib/cobimetinib resulted in smaller RT volumes. BRAF/MEK inhibitors could reduce RT volumes and spare dose to surrounding normal structures. Enrollment to Cohort B of Alliance A071601 should be considered for patients with recurrent tumors after RT.

SUPPORT

https://acknowledgments.alliancefound.org
DDRE-18. THERAPEUTIC EFFECTS OF TASQUINIMOD ON GLIOBLASTOMA
Authors: Liu Junfeng , Piranlioglu Raziye , Shono Naoyuki , Ling Alexander Lee , Soni Himanshu , Nakashima Hiroshi , Chiocca E Antonio
Published: November 2021

Glioblastoma is the most aggressive and most common primary malignant brain tumor in adults. This disease is still incurable despite multimodal therapies. We evaluated Tasquinimod, an oral HDAC4 inhibitor, in use with oncolytic HSV therapy. Tasquinimod is known to bind to HDAC4 and S100A9 to modulate myeloid population and angiogenesis in the tumors. This drug is being clinically evaluated in prostate and other solid tumors and multiple myeloma. However, the therapeutic effect of Tasquinimod in glioblastoma is not known. We found that Tasquinimod could change the immune-suppressive phenotype of MDSCs and polarize M2 macrophages towards M1 phenotype in ex vivo assay using mouse bone marrow cells treated with glioma conditioned media. We also tested Tasquinimod and oncolytic HSV in murine CT2A in C57/B6 mice and primary human GBM xenograft model in athymic mice. While the therapeutic effect of Tasquinimod or oHSV alone was not significant or marginal, the combo group show significantly longer survival. The study of underlying mechanisms is still ongoing. In conclusion, Tasquinimod combined with oncolytic HSV could have a better therapeutic effect on glioblastoma.
DDRE-19. SPHINGOSINE KINASE 1 AS A THERAPEUTIC TARGET FOR IDH1-R132H mut GLIOMA
Authors: Dowdy Tyrone , Yamasaki Tomohiro , Zhang Lumin , Celiku Orieta , Lita Adrian , Rodado Victor Ruiz , Gilbert Mark , Larion Mioara
Published: November 2021

BACKGROUND

Our study aimed to identify vulnerabilities within sphingolipid metabolism with potential to translate to therapeutics. While the vital role of sphingolipids in maintaining rheostat balance and as secondary messengers for signaling pathways (involving proliferation, invasion, migration, and angiogenesis) has been well-documented, their role has not been widely investigated in gliomas. Therefore, metabolic analysis of sphingolipid pathway for IDH1-R132H (IDH1 mut ) glioma cell lines was conducted in order to elucidate susceptible targets.

METHODS

Global sphingolipid quantification utilized high-throughput LCMS analysis. Pathway protein expression was measured via Western blots in vitro and derived from patients using The Cancer Genome Atlas analysis.

RESULTS

We probed the impact of decreasing D-2HG on the sphingolipid metabolism after treating a panel of IDH1 mut glioma cells with IDH1-R132H mut inhibitor, AGI5198. This revealed significant downregulation of N,N-dimethylsphingosine (NDMS), C17-sphingosine, and C18-sphinganine. Coincidentally, sphingosine-1-phosphate (S1P) was significantly upregulated in these gliomas. We conducted rational drug screen which revealed that inhibition of SPHK1 with N,N-dimethylsphingosine in combination with C17-sphingosine triggered biostatic dose-response across IDH1 mut gliomas and low impact on IDH WT glioblastoma (GBM) cells. Western analysis revealed that the IDH1 mut gliomas and IDH WT GBM expressed sphingosine kinase-1 (SPHK1). Data also unveiled a discovery that SPHK2 was highly expressed in the GBM cells while remarkably absent in the glioma cells.

CONCLUSION

Herein, we provide evidence that certain IDH1 mut gliomas present epigenetic silencing of SPHK2 which creates dependency on SPHK1 for S1P; thus, increasing sensitivity to targeting sphingolipid metabolism, and creating susceptibility to proliferation arrest and subsequent cellular death. S1P production has been reported to be elevated particularly for malignant glioblastomas in prior studies; whereas our research revealed that it is relatively low in IDH mut by comparison with IDH WT tumor cells. These findings suggest targeting the sphingolipid metabolism may present a promising strategy to improve survival for patients diagnosed with IDH1 mut gliomas.
DDRE-24. ARF4-MEDIATED RETROGRADE TRAFFICKING PROMOTES CHEMORESISTANCE IN GBM
Authors: Budhiraja Shreya , Baisiwala Shivani , Nandoliya Khizar , Dara Gabriel , Perrault Ella , Zolp Andrew , Chen Li , Dmello Crismita , Park Cheol , Sonabend Adam , Ahmed Atique
Published: November 2021

Glioblastoma (GBM) is the most common type of adult malignant brain tumor, with a median survival of only 21 months. This is partly due to the high rate of resistance to conventional therapy, including temozolomide (TMZ), leading to recurrence rates close to 100%. To identify the unknown genes driving the development of this resistance, we performed a genome-wide CRISPR knockout screen comparing a DMSO-treated population with a TMZ-treated population over 14 days. Results showed significant enrichment of ~200 novel genes and pathways. From this list, we identified 4 previously unstudied genes showing significant elevations in RNA expression (p< 0.05) when comparing recurrent and primary tumors in patient datasets, along with significant survival benefits corresponding to low gene expression (p< 0.05). Validation experiments in vitro showed significant elevations in RNA and protein expression in multiple patient-derived xenografts (PDX) lines during TMZ-treated conditions, while knocking out these genes also resulted in significantly heightened sensitivity to TMZ (p< 0.01). We investigated one particularly enriched gene, ARF4, known to be involved in retrograde trafficking. With previous studies showing that ARF4 is upregulated under ER stress, we first confirmed the increased expression of ER stress markers during TMZ treatment to explain the increased expression of ARF4 during treatment. Further investigation via live-cell imaging also showed a consequent increase in retrograde trafficking in TMZ-treated cells, as evidenced by significantly increased trafficking of transferrin receptors, a retrograde transport marker, as well as EGFR, known to play a role in promoting chemoresistance through strengthened DNA repair response. ARF4-overexpressed GBM cells similarly showed increased trafficking of transferrin receptors and EGFR to the nucleus, while ARF4-knockdowns showed decreased trafficking and nuclear EGFR expression. Ultimately, our CRISPR-Cas9 screen has identified a promising therapeutic target, ARF4, which may drive GBM’s robust resistance to chemotherapy through increased retrograde trafficking of chemoresistance-promoting nuclear EGFR.
DDRE-25. WSD0628: A BRAIN PENETRABLE ATM INHIBITOR AS A RADIOSENSITIZER FOR THE TREATMENT OF GBM AND METASTATIC CNS TUMOR
Authors: zhong wei , Liu Lily , Sun Claire , Mu Zhihua
Published: November 2021

ATM (ataxia telangiectasia mutated) kinase, activated by DNA double-strand breaks, promotes DNA repair as well as activates DNA damage checkpoint and plays a key role for resistance to radiotherapy and chemotherapy. ATM function loss confers hypersensitivity to ionizing radiation evidenced by ataxia-telangiectasia (A-T) cells. Thus, pharmacological inhibition of ATM kinase is expected to suppress DSB DNA repair, block checkpoint controls and enhance the therapeutic effect of radiotherapy and other DNA double-strand breaks-inducing chemotherapy. Herein, we report a discovery of a potent, selective, orally bioavailable, and brain penetrable ATM inhibitor WSD0628, as a radiosensitizer for GBM and metastatic CNS tumors with IC50 against ATM < 1nM with high selectivity ( >400 folds) for ATR and DNA-PK. WSD0628 is highly selective over other kinases. In-vitro MDCKII transfected cells and Caco-2 assays have shown that WSD0628 is highly permeable and not a substrate of P-gp or BCRP, two main efflux transporters expressed on human BBB. Preclinical CNS PK studies in rat and mouse confirmed good brain penetration of WSD0628 with Kp,uu,brain and Kp,uu,csf > 0.3. Significant prolongation of overall survival for mice bearing GBM PDX intracranial model was achieved by treatment with WSD0628 (5mpk, QD) combo with radiation. Moreover, WSD0628 shows low PK variation liability without aldehyde oxidase (AO) metabolism, low hERG liability ( >30 uM), and good safety window based on DRF studies. Taken together, our data provide a good rationale for WSD0628 to be developed toward clinic combo with radiation for the treatment of patients with GBM and cancers with CNS metastasis.
DDRE-29. EGFR INHIBITION DOWNREGULATES MGMT AND SENSITIZES GBM CELLS TO TMZ
Authors: Habib Amyn , Sarkaria Jann , Gong Ke , Guo Gao
Published: November 2021

Glioblastoma (GBM) is a highly malignant type of adult brain tumor with a poor prognosis. Temozolomide (TMZ), a DNA alkylating agent, has been widely used as an effective first-line chemotherapeutic agent for the treatment of GBM patients. The efficacy of TMZ in GBM depends on the absence of the DNA repair protein MGMT which reverses the DNA damage induced by TMZ. The MGMT promoter is hypermethylated in about 45% of GBMs, resulting in lack of MGMT expression and increased responsiveness to TMZ. TMZ is less effective in MGMT unmethylated GBMs. We propose that EGFR inhibition downregulates MGMT and sensitizes glioma cells to TMZ and a combination of pretreatment with erlotinib followed by TMZ could be a useful therapeutic approach in MGMT expressing GBMs. As our experimental model, we used multiple MGMT unmethylated lines from the Mayo Clinic patient derived xenografts (PDXs) panel. Our data demonstrate that exposure of cells to erlotinib for 48h results in downregulation of MGMT at the mRNA and protein level. Additionally, EGFR inhibition activates the AP-1 transcription factor, and overexpression of AP-1 components Fos and Jun results in decreased MGMT expression in TMZ resistant PDXs, suggesting that AP-1 acts as a transcriptional repressor of MGMT. We further identified that the mice implanted with TMZ resistant PDXs pretreated with afatinib followed by TMZ treatment survived longer compared to those treated with TMZ alone. Thus, the use of EGFR inhibition may enhance the sensitivity of MGMT unmethylated GBMs to TMZ.
DDRE-35. PRE-CLINICAL ASSESSMENT OF PPRX-1701, A NANOPARTICLE FORMULATION OF 6-BROMO-ACETOXIME, FOR THE TREATMENT OF GLIOBLASTOMA
Authors: Zdioruk Mykola , Finkelberg Tomer , Nowicki Michal , Wu Bin , Takeda Yuji , Chiocca Antonio , Lawler Sean
Published: November 2021

We previously showed that derivatives of the Chinese traditional medicine indirubin promote survival in murine glioblastoma models (Williams et al. Cancer Research 2011). However, poor drug solubility hampered further development of this approach. Here we introduce PPRX-1701, a 6’-bromoindirubin acetoxime (BiA) containing drug/polymer nanoparticle formulation which can be injected intravenously at relatively high concentrations. Mechanistically, BiA is thought to act as a broadly selective serine-threonine protein kinase inhibitor, with activity against Src family kinases, GSK-3 and JAK2. Our preliminary data show that intravenous administration of PPRX-1701 is well-tolerated and can reach intracranial murine glioblastoma as assessed by luminescent reporter assays. PPRX-1701 administration leads to improved survival in the GL261 glioblastoma mouse model (median survival 30 days (control), 47 days (treated), p < 0.0001). Treatment with PPRX-1701 was associated with alterations in the tumor immune microenvironment, with reduced Tregs and pro-tumor macrophages, and increased CD8+ T cells. Further preliminary mechanistic studies have shown that PPRX-1701/BiA blocks the expression multiple immunosuppressive molecules in GBM downstream of interferon-g (IFNg) including PD-L1 and indoleamine 2,3-dioxygenase 1 (IDO1) - a key enzyme in the tryptophan–kynurenine–aryl hydrocarbon receptor (Trp–Kyn–AhR) immunosuppressive pathway. BiA promoted more effective T-cell mediated tumor cell killing using patient derived glioblastoma ex vivo co-culture models. This data supports further development of PPRX-1701 is a candidate immunotherapeutic agent for glioblastoma treatment. Ongoing pre-clinical studies are investigating combination with other relevant therapies.
DDRE-36. INVESTIGATING MEDULLOBLASTOMA HETEROGENEITY AND PREDICTING COMPOUND RESPONSE
Authors: Ruiz Luz , Ayad Nagi
Published: November 2021

Medulloblastoma is the most common malignant brain tumor found in children. It is a cerebellar tumor that affects motor and cognitive processes such as coordination and movement. The standard of care is surgical removal, radiation, and chemotherapy. These treatments can be very damaging to the developing child, in that they can impair vision and walking, among other body functions. Due to this, new treatments are necessary. Treatment plans for children with medulloblastoma need to be tailored to the specific subtype that they have. Genetic studies have revealed that there are four subtypes of pediatric medulloblastoma: Group 3, Group 4, SHH, and WNT. Beyond these bulk-resolution subtypes, we hypothesize intratumor heterogeneity as a barrier to new effective treatments. I have mined single-cell RNA sequencing data to investigate cellular heterogeneity and predict compound response. I analyzed Medulloblastoma patient tumor data along with data obtained from a 10X Genomics Chromium single-cell RNA sequencing experiment performed in the laboratory from a Tg (Neurod-Smoothened*A1) mouse. We hypothesize that distinct cell populations within medulloblastoma should show different predicted compounds that would target them. We have ranked compound predictions to investigate whether compounds may selectively target any of these populations using transcriptional response signatures derived from the LINCS L1000 perturbagen-response dataset. We also hypothesize that Medulloblastoma tumors have distinct subtypes of cells that are preferentially sensitive to BET bromodomain, casein kinase, and ATM/ATR inhibitors. Our analysis identified ten transcriptionally distinct cell types across these medulloblastoma tumors as well as compounds predicted to target them in each transcriptional subtype. Furthermore, we identified bromodomain and casein kinase inhibitors as a potential combination therapy due to their predicted synergy at targeting all cell populations within medulloblastoma. Our studies show the importance of considering cellular heterogeneity when identifying new treatments for medulloblastoma and other brain cancers.
DDRE-45. HIGH-THROUGHPUT SCREENING OF EPIGENETIC COMPOUNDS FOR THE TREATMENT OF CHORDOMA IDENTIFIES POTENTIAL NOVEL THERAPEUTICS
Authors: Wroblewski Tadeusz , Tatman Philip , Fringuello Anthony , Scherer Sam , Foreman William , Damek Denise , Youssef Samy , Lillehei Kevin , Ormond David , Graner Michael
Published: November 2021

BACKGROUND

Chordoma is a rare malignant tumor with few treatment options. While surgical resection is deemed the most effective treatment, the 5-year overall survival rate is 61% and 5-year recurrence free survival rate is approximately 50%. To date, no FDA approved pharmacotherapies exist for the treatment of chordoma, and adjuvant therapy remains highly debated. This necessitates the need for further research to provide clinicians with more options to treat this patient population.

METHODS

In this study, we conducted a high-throughput 139-compound epigenetic inhibitor screen against 12 chordoma patient-derived cell lines; 4 were resected at our institution and 8 were graciously donated by the Chordoma Foundation.

RESULTS

8 tumors were located in the sacrum, 3 were located in the mobile spine, and 1 tumor was located in the clivus. 5 tumors were primary, 5 were recurrent, and 2 were metastatic. 6 tumors came from female patients and 6 tumors came from male patients. The top three most effect compounds across the cohort were the G9a inhibitor UNC0631 (cell viability = 64.5% +/-25.1SD; p=1.53x10-9), the KDM inhibitor JIB-04 (cell viability = 68.4% +/-27.2SD; p=9.81x10-8), and the G9a inhibitor BIX01294 (cell viability = 68.6% +/-27.9SD; p=1.27x10-7). No single compound significantly reduced viability in every tumor in the cohort, although the HDAC inhibitor HC Toxin significantly reduced viability in 9 tumors (cell viability = 69.7% +/-16.6SD; p=2.6x10-12). The most effective compound for sacral tumors was UNC0631 (viability = 68.6% +/-22.1SD; p=4x10-7), UNC0631 was also the most effective for spinal tumors (viability = 54.4% +/-32.1SD; p=2.72x10-3), and notably, no significant compounds were identified for the single clival tumor.

CONCLUSIONS

Based on our drug screen results, epigenetic inhibition, particularly methyltransferase inhibition, may be a promising therapeutic avenue for the treatment of chordomas.
EPID-15. AGE AND DOSIMETRIC IMPACTS ON RADIOTHERAPY ASSOCIATED GROWTH IMPAIRMENT FOR PATIENTS WITH INTRACRANIAL GERM CELL TUMORS (GCTs)
Authors: Deng Guanhua , Zhou Zhaoming , Li Juan , Lai Mingyao , Hu Qingjun , Zhou Cheng , Cai Linbo
Published: November 2021

PURPOSE

Intracranial germ cell tumors (GCTs) are rare pediatric central nervous system (CNS) tumors. Growth impairment induced by radiation treatments was rarely evaluated. We aimed to study the impacts of radiotherapy on height development and identify the dosimetric constraints.

MATERIALS AND METHODS

A total of 148 pediatric patients diagnosed with GCTs were retrospectively analyzed. Sex, age at irradiation, physical doses and biologically effective dose (BED), height, and endocrine status were obtained from patient records. The cumulative change in height was assessed using age-matched normalized height (ANH). Variables were assessed for correlations and statistical significance.

RESULTS

Cumulative physical doses and BEDs for the whole brain and pituitary were derived via DVHs and BEDVHs. In contrast to patients >11.5 yr, linear correlations between ANH and cumulative physical doses as well as BEDs to the whole brain and pituitary were identified in patients≤11.5 yr. Dosimetric constrains to the pituitary was 36 Gy for physical dose (AUC=0.70 [95% CI, 0.54-0.86], P< 0.05) and 63 Gy2 BED (AUC=0.69 [95% CI, 0.53-0.86], P< 0.05). Intriguingly, no significant differences in ANH were found among different CSI dose groups in patients ≤11.5 yr. (all P>0.05). Impaired hormone secretions in terms of GH and TSH were identified following cranial irradiation (both P< 0.001), particularly for those with tumors at the suprasellar region (GH: P< 0.01, TSH: P< 0.001).

CONCLUSION

Our study revealed the impacts of age, dosimetrics and tumor locations for growth impairment. This study will contribute to the optimization of radiation treatment planning and facilitate more individualized therapeutic strategies in pediatric patient with GCTs.
EPID-16. DIFFUSE LEPTOMENINGEAL GLIONEURONAL TUMOR IN PEDIATRIC PATIENTS: A QUANTITATIVE EXPLORATION
Authors: Lu Victor , Di Long , Daniels David , Maher Ossama , Niazi Toba
Published: November 2021

BACKGROUND

Diffuse leptomeningeal glioneuronal tumor (DLGNT), also known as oligodendrogliomatosis, is a rare neuro-oncologic condition along the neuraxis that remains poorly understood in children. We sought to describe our institutional experience and quantitively summarize the clinical survival and prognostic features of DLGNT in the pediatric population across the contemporary literature.

METHODS

We report four institutional cases of pediatric DLGNT diagnosed between 2000-2020 based on retrospective review of our records, and performed a comprehensive literature search for published cases from 2000 onwards to create an integrated cohort for analysis. Kaplan-Meier estimations, Fisher’s exact test, and logistic regression were utilized to interrogate the data.

RESULTS

Our overall integrated cohort consisted of 54 pediatric DLGNT patients, with 19 (35%) female and 35 (65%) male patients diagnosed at an average age of 6.4 years (range, 1.3-17 years) by means of surgical biopsy. Chemotherapy was used in 45 cases (83%), and mean follow-up time of 54 months (range, 3-204). Across the entire cohort, overall survival 1 month after diagnosis was 96% (95% CI 86-99%), and by 10 years was 69% (95% CI 49-82%). On multivariate analysis of complete data, chemotherapy treatment (HR=0.23, P=0.04) was statistically predictive of longer overall survival. When including limited data, longer duration of symptoms by presentation (HR=1.03, P=0.03) was statistically predictive of shorter overall survival.

CONCLUSIONS

This is the first quantitative study of pediatric DLGNT clinical course. More than 2-out-of-3 pediatric DLGNT patients survive beyond one decade. Chemotherapy is statistically associated with longer survival in DLGNT pediatric patients and should form the core of any treatment regimen in this setting. Early detection by means of judicious imaging and surgical biopsy for tissue diagnosis can lead to earlier treatment and likely superior outcomes.
EPID-18. USING GERMLINE VARIANTS FOR DIFFERENTIAL DIAGNOSIS OF INDETERMINATE BRAIN LESIONS: EVALUATING THE EFFECT OF TUMOR TYPE AND RACE ON SENSITIVITY AND SPECIFICITY OF GLIOMA polygenic risk models
Authors: Eckel-passow Jeanette , Paul Decker , Kosel Matthew , Kollmeyer Thomas , Drucker Kristen , Conte Gian Marco , Erickson Bradley , Slager Susan , Lachance Daniel , Jenkins Robert , Tobin Oliver
Published: November 2021

Abnormalities on brain MRI may be identified in ~15% of individuals aged 50-66. It can be difficult to discriminate glioma, CNS lymphoma, Inflammatory Demyelinating Disease (CNSIDD) and solitary metastasis, and misdiagnosis may expose patients to unnecessary anxiety, surgery, or radiotherapy. CNS lymphoma requires only biopsy, solitary metastasis may be resected and radiated or radiated empirically, and high-grade glioma requires maximal safe resection followed by chemoradiation. CNSIDD should only be biopsied when diagnostic uncertainty requires it, and resection and radiotherapy are unnecessary, introducing unwarranted morbidity. Polygenic risk models can identify patients at the highest risk of developing glioma; we hypothesized that these polygenic models could help with differential diagnosis of indeterminate brain lesions. We also hypothesized that race would be an important contributing factor in the models. In the initial discovery and validation European (EUR) cohorts the mean probability of glioma for IDHmut non-codeleted glioma was 0.55 and 0.52, respectively, and in healthy controls was 0.19 and 0.21, respectively. To further evaluate sensitivity, we analyzed additional genotype data from 867 gliomas (764 EUR, 54 AFR, 24 AMR, 15 EAS, 10 SAS) from The Cancer Genome Atlas (TCGA). Across 764 EUR IDHmut non-codeleted glioma, the mean probability 0.53, whereas across 54 AFR and 24 AMR the mean was 0.22 and 0.32, respectively. To evaluate specificity, we analyzed 3200 TCGA patients with primary tumor types that commonly metastasize to the brain (2676 EUR, 365 AFR, 46 AMR, 95 EAS, 18 SAS), and 236 AFR healthy controls. For patients with non-CNS primary tumors, the mean probability ranged from 0.09-0.18 for EUR and 0.04-0.07 for AFR. For AFR healthy controls, the mean was 0.05. Overall, race is a significant factor for polygenic risk models. Further work entails evaluating polygenic risk models in IDHwt glioma, CNS lymphoma and CNSIDD cohorts as well as in additional races.
IMMU-05. CCR2+ MYELOID-DERIVED SUPPRESSOR CELLS FROM MURINE GLIOMAS ARE SOURCED FROM THE BONE MARROW, SUPPRESS T CELL ACTIVATION, AND MIGRATE TO CCL2
Authors: Takacs Gregory , Kreiger Christian , Luo Defang , Flores-Toro Joseph , Deleyrolle Loic , Rahman Maryam , Mitchell Duane , Harrison Jeffrey
Published: November 2021

INTRODUCTION

Mounting evidence suggests infiltrating immune-suppressive cells contribute to immune checkpoint inhibitor resistance and poor survival in Glioblastoma (GBM) patients. We have previously shown glioma-associated monocytic-myeloid derived suppressor cells (M-MDSCs) express chemokine receptors CCR2 and CX3CR1. Genetic and pharmacologic targeting of CCR2 promoted sequestration of M-MDSCs in the bone marrow and, in combination with PD-1 blockade, slowed progression of KR158 and 005GSC murine gliomas. This combination treatment also enhanced infiltration of IFNg-producing T cells that were less exhausted. Although CCR2+/CX3CR1+ cells display surface markers indicative of bone marrow-derived M-MDSCs, additional studies are needed to formally establish the source of these cells and to determine if they exhibit an immune-suppressive phenotype as well as migrate to the CCR2 ligands, CCL2 and/or CCL7.

OBJECTIVE

Evaluate the source, migration, and immune suppressive function of CCR2+/CX3CR1+ myeloid cells from glioma bearing mice.

METHODS

To identify the source of CCR2+/CX3CR1+ myeloid cells, chimeric wild type mice harboring bone marrow cells from transgenic CCR2WT/RFP/CX3CR1WT/GFP mice were generated. CCR2+/CX3CR1+ cells were enriched from bone marrow obtained from either wild-type or CCR2WT/RFP/CX3CR1WT/GFP naïve and glioma-bearing mice in order to evaluate their immune suppressive phenotype and ability to migrate to CCL2 and CCL7.

RESULTS

CCR2+/CX3CR1+ cells are present in glioma isolates from chimeric mice, indicative of a bone marrow-derived cell population, and are detectable within the tumor microenvironment as early as 3 days post orthotopic implantation of KR158 cells; these cells accumulate as tumors increase in size (r=0.7605, p=0.007). CCR2+/CX3CR1+ M-MDSCs isolated from the bone marrow of tumor bearing mice suppress CD8+ T cell production of IFNg and migrate to CCL2 more efficiently than CCL7.

CONCLUSION

CCR2+/CX3CR1+ cells from glioma bearing mice are derived from the bone marrow and represent an immune suppressive population that migrates to CCL2.