An Exome Capture-Based RNA-Sequencing Assay for Genome-Wide Identification and Prioritization of Clinically Important Fusions in Pediatric Tumors

This study reports the development of an exome capture-based RNA-sequencing assay to detect recurring and novel fusions in hematologic, solid, and central nervous system tumors. The assay used Twist Comprehensive Exome capture with either fresh or formalin-fixed samples and a bioinformatic platform that provides fusion detection, prioritization, and downstream curation. A minimum of 50 million uniquely mapped reads, a consensus read alignment/fusion calling approach using four callers (Arriba, FusionCatcher, STAR-Fusion, and Dragen), and custom software were used to integrate, annotate, and rank the candidate fusion calls. In an evaluation of 50 samples, the number of calls varied substantially by caller, from a mean of 24.8 with STAR-Fusion to 259.6 with FusionCatcher; only 1.1% of calls were made by all four callers. Therefore a filtering and ranking algorithm was developed based on multiple criteria, including number of supporting reads, calling consensus, genes involved, and cross-reference against databases of known cancer-associated or likely false-positive fusions. This approach was highly effective in pinpointing known clinically relevant fusions, ranking them first in 47 of 50 samples (94%). Detection of pathogenic gene fusions in three diagnostically challenging cases highlights the importance of a genome-wide and nontargeted method for fusion detection in pediatric cancer.

MEK inhibitors for neurofibromatosis type 1 manifestations: Clinical evidence and consensus

The wide variety of clinical manifestations of the genetic syndrome neurofibromatosis type 1 (NF1) are driven by overactivation of the RAS pathway. Mitogen-activated protein kinase kinase inhibitors (MEKi) block downstream targets of RAS. The recent regulatory approvals of the MEKi selumetinib for inoperable symptomatic plexiform neurofibromas in children with NF1 have made it the first medical therapy approved for this indication in the United States, the European Union, and elsewhere. Several recently published and ongoing clinical trials have demonstrated that MEKi may have potential benefits for a variety of other NF1 manifestations, and there is broad interest in the field regarding the appropriate clinical use of these agents. In this review, we present the current evidence regarding the use of existing MEKi for a variety of NF1-related manifestations, including tumor (neurofibromas, malignant peripheral nerve sheath tumors, low-grade glioma, and juvenile myelomonocytic leukemia) and non-tumor (bone, pain, and neurocognitive) manifestations. We discuss the potential utility of MEKi in related genetic conditions characterized by overactivation of the RAS pathway (RASopathies). In addition, we review practical treatment considerations for the use of MEKi as well as provide consensus recommendations regarding their clinical use from a panel of experts.

LTBK-04. LATE BREAKING ABSTRACT: MEK162 (binimetinib) in children with progressive or recurrent low-grade glioma: a multi-institutional phase II and target validation study

BACKGROUND

RAS/RAF/MEK/ERK pathway activation is the primary driver for most pediatric low-grade gliomas (pLGG). MEK162 (binimetinib) is an orally bioavailable MEK1/2 inhibitor with superior brain penetration in a preclinical model. The primary objective of this multi-institutional phase II and target validation study was to assess stratum-specific efficacy of binimetinib in progressive pLGG.

METHODS

Eligible children aged 1-18 years with previously treated radiographically progressive pLGG were enrolled and treated with binimetinib, starting dose 32mg/m2/dose twice daily. Stratum 1 included patients with pLGG with documented BRAF fusion; stratum 2, neurofibromatosis 1 (NF1)-associated pLGG; stratum 3, sporadic pLGG without documented BRAF fusion; and stratum 4, patients undergoing planned tumor biopsy who began binimetinib preoperatively. Partial and minor responses (PR and MR) were defined as ≥50% and ≥25% decrease in maximal two-dimensional measurements.

RESULTS

Of 86 patients enrolled, 85 were evaluable for response. Of these, 48 (56%) showed a radiographic response (30 PR and 18 MR) in the first year of treatment. Response rate for stratum 1 (n=28) was 50% (12 PR and 2 MR); 12 (43%) had stable disease (SD) and 2 (7%) progressive disease (PD). Stratum 2 (n=21) response rate was 43% (5 PR, 4 MR), with 12 (57%) SD and no PD. Stratum 3 (n=29) response rate was 69% (10 PR, 10 MR), 4 (14%) SD and 5 (17%) PD. Stratum 4 (n=7) include 3 PR, 2 MR, 2 SD. Nineteen (22%) discontinued treatment for toxicity (most commonly dermatologic), and an additional 42 (49%) required dose reduction. Median dose at the time of PR/MR was 28mg/m2; responses were seen at doses as low 16mg/m2.

CONCLUSION

Binimetinib is highly effective in the treatment of both NF1-associated and sporadic pLGG, with or without documented BRAF fusion. Modified dosing strategies to improve tolerability may be considered in future trials.

HGG-11. Clinical characteristics and clinical evolution of a large cohort of pediatric patients with primary central nervous system (CNS) tumors and tropomyosin receptor kinase (TRK) fusion

BACKGROUND: TRK fusions are detected in less than 3% of CNS tumors. Given their rarity, there are limited data on the clinical course of these patients. METHODS: We contacted 166 oncology centers worldwide to retrieve data on patients with TRK fusion-driven CNS tumors. Data extracted included demographics, histopathology, NTRK gene fusion, treatment modalities and outcomes. Patients less than 18 years of age at diagnosis were included in this analysis. RESULTS: Seventy-three pediatric patients with TRK fusion-driven primary CNS tumors were identified. Median age at diagnosis was 2.4 years (range 0.0–17.8) and 60.2 % were male. NTRK2 gene fusions were found in 37 patients (50.7%), NTRK1 and NTRK3 aberrations were detected in 19 (26.0%) and 17 (23.3%), respectively. Tumor types included 38 high-grade gliomas (HGG; 52.1%), 20 low-grade gliomas (LGG; 27.4%), 4 embryonal tumors (5.5%) and 11 others (15.1%). Median follow-up was 46.5 months (range 3-226). During the course of their disease, a total of 62 (84.9%) patients underwent surgery with a treatment intent, 50 (68.5%) patients received chemotherapy, 35 (47.9%) patients received radiation therapy, while 34 (46.6%) patients received NTRK inhibitors (3 as first line treatment). Twenty-four (32.9%) had no progression including 9 LGG (45%) and 9 HGG (23.6%). At last follow-up, only one (5.6%-18 evaluable) patient with LGG died compared to 11 with HGG (35.5%-31 evaluable). For LGG the median progression-free survival (PFS) after the first line of treatment was 17 months (95% CI: 0.0-35.5) and median overall survival (OS) was not reached. For patients with HGG the median PFS was 30 months (95% CI: 11.9-48.1) and median OS was 182 months (95% CI 20.2-343.8). CONCLUSIONS: We report the largest cohort of pediatric patients with TRK fusion-driven primary CNS tumors. These results will help us to better understand clinical evolution and compare outcomes with ongoing clinical trials.

LGG-23. Cardiac function in children and young adults treated with MEK inhibitors: a single institution retrospecive cohort study

INTRODUCTION: MEK inhibitors (MEKi) have shown efficacy in pediatric low-grade glioma, among other tumors, but have been associated with acute cardiac dysfunction in adults. Cardiac consequences in children are unknown. MATERIAL AND METHODS: We performed a single center retrospective cohort study evaluating cardiac function by echocardiography (echo) in children and young adults <21 years old receiving MEKi at Children’s Hospital Los Angeles between October 2013 and May 2018. Blinded assessment of left ventricular function by fractional shortening (FS) and ejection fraction (EF) was performed on all available echocardiograms obtained before, during, and following therapy, as well as after re-initiation of therapy. RESULTS: Twenty-six patients underwent MEKi therapy with echo follow-up during the study period. Twenty-four of these had complete echo data. Median follow-up was 12 months. Borderline EF (EF 53-57.9%) occurred in 12 (50%) patients; and 3 (12.5%) progressed to abnormal EF (EF <53%). Cardiac dysfunction, when it occurred, was mild (lowest documented EF was 45%, and lowest FS was 24.4%). EF abnormalities typically fluctuated during therapy, resolved off therapy, and recurred with MEKi re-initiation. No clinical or demographic differences were detected between those who maintained normal cardiac function and those who developed borderline or overt cardiac dysfunction. Symptomatic heart failure did not occur. CONCLUSION: In this cohort of children and young adults, MEKi use was associated with a relatively high incidence of borderline decrease in left ventricular function, often of uncertain clinical significance. There was no evidence of permanent cardiac dysfunction. Further evaluation in larger prospective trials is needed.

LGG-62. Weight change in pediatric patients treated with MEK inhibitors: a retrospective cohort study

BACKGROUND: MEK inhibition is an emerging treatment strategy in pediatric tumors characterized by activation of the Ras-Raf-MEK-ERK pathway, including low-grade glioma (LGG) and neurofibromatosis 1 (NF1)-associated tumors. Preliminary clinical experience suggests that MEK inhibitors (MEKi) may be associated with weight gain in children, which has not been a reported toxicity in adults. METHODS: 35 patients > 1 and < 21 years old treated at CHLA with MEKi between October 2013 and May 2019 were identified. Data was collected at t = 0 (baseline), t = 3 months, t = 6 months, t = 12 months, and t = 24 months, as well as pre- and post-treatment time points. Weight change was categorized as no change (change in Z-score [-0.25, +0.25]), weight gain (change in Z-score > 0.25), and weight loss (change in Z-score > -0.25). RESULTS: Weight gain and weight loss were seen in 11 (34.4%) and 8 (25%) patients, respectively, after 6 months on therapy. Weight gain reversed in 4 out of 5 patients with post-treatment data. There was no clear association between weight outcome and hypothesized covariates (including hypothalamic location and NF1 status). Notably, significant weight gain was seen across baseline weight spectrum, including patients who had underweight and severely overweight BMI percentiles at baseline. CONCLUSION: Our findings preliminarily suggest that MEK inhibition may be associated with clinically significant weight change, especially weight gain, in a subset of children and young adults. Reversal upon drug cessation suggests a causal relationship. Further prospective and mechanistic investigation is needed.

MEDB-86. A re-induction regimen for children with recurrent medulloblastoma

Medulloblastoma is the most common malignant brain tumor of childhood. Despite multi-modal therapies, ~30% of patients experience disease recurrence, which portends a poor prognosis. At initial recurrence, intensive chemotherapy may be effective prior to various consolidation therapies including high dose chemotherapy with autologous stem cell rescue or irradiation. We report outcomes for nine children treated at two institutions with the following regimen: cyclophosphamide 1500mg/m2/dose days 1,2; irinotecan 125mg/m2/dose days 1,8; temozolomide 150mg/m2/dose days 1-5, and oral etoposide 50mg/m2/dose days 1-7. Patients received 2-4 cycles based upon disease response and physician preference. The mean time from initial diagnosis to first recurrence was 19 months. After receiving two cycles of therapy, two patients had complete response (CR) and proceeded to consolidation. Of the remaining seven patients, five had partial response (PR) and two had stable disease (SD). Overall response rate was 78% after 2 cycles. Two patients with PR proceeded directly to consolidation with irradiation. Five patients (3 PR, 2 SD) received 2 additional cycles. After four cycles there was one CR, two with minimal residual disease, one SD and one progressive disease (PD). Four patients (44%) are alive with no evidence of disease (NED). One patient died of consolidation-related toxicity but had NED at time of death 28 months from initial recurrence. Five patients developed PD. Two patients died of disease, two are alive with disease, and one is alive with NED after PD and additional therapy. There were no treatment-related deaths. Infection was the most common complication. Five patients had febrile neutropenia and two developed sepsis. One patient required dose reduction for prolonged thrombocytopenia. Peripheral blood stem cell collection was achieved in all patients for whom it was attempted. This re-induction regimen is generally well-tolerated and effective in inducing responses for children with recurrent medulloblastoma.

IMG-03. RESPONSE ASSESSMENT IN PEDIATRIC LOW-GRADE GLIOMA: RECOMMENDATIONS FROM THE RESPONSE ASSESSMENT IN PEDIATRIC NEURO-ONCOLOGY (RAPNO) WORKING GROUP

INTRODUCTION

Pediatric low-grade gliomas (pLGG) show clinical and biological features that are distinct from their adult counterparts. Consequently, additional considerations are needed for response assessment in children compared to the established adult Response Assessment in Neuro-Oncology (RANO) criteria. Standardized response criteria in pediatric clinical trials are lacking, complicating comparisons of responses across studies. We therefore established an international committee of the Radiologic Assessment in Pediatric Neuro-Oncology (RAPNO) working group to develop consensus recommendations for response assessment in pLGG.

METHODS

The committee consisted of 25 international experts in the areas of Pediatric Neuro-Oncology, Neuroradiology and Neurosurgery. The committee first developed a set of agreed upon topics they deemed necessary to understand the controversies of imaging utilization and assessment in pLGG. These topics were divided up among the committee members who presented all available literature to the entire RAPNO committee via web teleconference. Once presented, the group discussed these data and developed consensus statements and recommendations based on available literature, committee expertise and clinical experience. Each topic was discussed until a consensus was reached.

RESULTS

Final consensus included recommendations about the following topics: specific imaging sequences, advanced imaging techniques, NF1-associated pLGG, molecular and histologic classification, assessment of cysts, vision and other functional outcomes as well as overall radiologic response assessment.

CONCLUSIONS

The RAPNO pLGG consensus establishes systemic recommendations that represent an initial effort to uniformly collect and assess response in pLGG. These recommendations should now be evaluated internationally and prospectively in an effort to assess clinical utility, validate and modify as appropriate.

LGG-52. BINIMETINIB IN CHILDREN WITH PROGRESSIVE OR RECURRENT LOW-GRADE GLIOMA NOT ASSOCIATED WITH NEUROFIBROMATOSIS TYPE 1: INITIAL RESULTS FROM A MULTI-INSTITUTIONAL PHASE II STUDY

BACKGROUND

RAS/RAF/MEK/ERK pathway activation is the primary driver for most pediatric low-grade gliomas (LGG). Binimetinib is an orally bioavailable MEK1/2 inhibitor found to have significant central nervous system penetration in a preclinical model.

OBJECTIVE

The primary objective of this multi-institutional open-label phase II study was to assess preliminary efficacy of binimetinib in progressive pediatric LGG. The study included strata for both neurofibromatosis type I (NF1) and non-NF1 associated tumors, as well as a target validation (surgical) stratum. NF1 and surgical strata remain open to enrollment and will be reported separately.

METHODS

Children aged 1–18 years with previously treated recurrent or progressive LGG were eligible. The dose of binimetinib was 32 mg/m²/dose twice daily. Partial and minor responses were defined, respectively, as 50% and 25% decrease in maximal two-dimensional measurements.

RESULTS

Fifty-seven eligible patients without NF1, median age 8 years, were enrolled and began treatment; 26 were female; 28 had documented KIAA1549-BRAF fusion. Eleven patients discontinued drug in the first year due to toxicity, and an additional 27 required dose reduction. The most common drug-attributable grade 3 toxicities included creatine kinase elevation (n=9 patients), rash (n=8), and truncal weakness (n=8). Truncal weakness improved or resolved with dose reduction or cessation. Grade 4 toxicities included creatine kinase elevation (n=2) and transient colitis (n=1). Of 44 patients with preliminary response data available, 22 (50%) showed a minor (n=7) or partial (n=15) response.

CONCLUSION

Binimetinib is active, with manageable toxicities, in children without NF1 with progressive LGG.

NURS-09. INTRODUCTION OF A WELLNESS PROGRAM FOR PEDIATRIC NEURO-ONCOLOGY PROVIDERS

INTRODUCTION

Pediatric oncology providers have unique and rewarding careers. The medical and psychosocial complexity of caring for pediatric oncology patients and their family units is simultaneously inspiring and challenging. In addition, the complex demands of the healthcare system can lead to chronic stress, burnout, and disruption to the healthcare professional’s individual well-being. Time constraints, lack of resources, and limited access to wellness interventions serve as barriers for providers to address adaptive coping within themselves. Identifying gaps to achieving wellness and implementing interventions may lead to improved equanimity for pediatric oncology providers in their personal lives as well as their medical practice.

METHODS

An interdisciplinary team of nurse practitioners and physicians in a large pediatric neuro-oncology program at an academic institution completed anonymized wellness self-assessments regarding the areas of emotional, environmental, intellectual, occupational, physical, social, spiritual, coping, and professional role wellness. The results were analyzed and barriers to provider health and well-being were identified. Tailored and regularly scheduled wellness interventions were implemented for the study participants addressing the identified wellness barriers. Participants will each complete post-intervention wellness self-assessments to evaluate the effectiveness of the program.

CONCLUSION

The introduction of a provider wellness program exemplifies a feasible approach to identify barriers and evaluate efficacy of wellness interventions in achieving multi-factorial provider wellness. Secondary aims include dissemination of findings, with the intention of cultivating improvement in provider quality of life throughout the healthcare profession, and the ultimate goal of improving care to patients and families.

Clinical and neuropsychological outcome of pediatric non-midline central nervous system germinoma treated with chemotherapy and reduced dose/volume irradiation: The Children's Hospital Los Angeles experience

BACKGROUND

Germ cell tumors (GCT) arising from non-midline structures (basal ganglia, thalamus, and posterior fossa) are rare. Although patients with midline (pineal and suprasellar) germinoma have excellent survival with chemotherapy and whole ventricular irradiation (WVI), germinoma in non-midline locations have traditionally been treated with craniospinal irradiation (CSI) or whole brain irradiation (WBI) to achieve similar outcomes. However, CSI and WBI are associated with significant long-term neuropsychological sequelae.

METHODS

We describe the clinical and neuropsychological outcomes of patients with non-midline germinoma treated at the Children's Hospital Los Angeles between 1990 and 2015.

RESULTS

Nine patients had basal ganglia/thalamic germinoma and one patient had a cerebellar primary. Eight patients received chemotherapy followed by reduced dose/volume irradiation, whereas two patients received chemotherapy alone as upfront therapy. One patient in the chemotherapy alone group relapsed after 4.3 years and was salvaged with CSI plus boost. The overall survival for the entire cohort was 100% at a median follow-up of 8.5 years. Neuropsychological data were available for six patients at a median of five months (baseline) and 4.2 years (follow-up) post-diagnosis. At four-year follow-up, data available revealed intact overall cognitive ability, verbal memory, and executive functioning, but persistent deficits in fine motor function. Comparison of baseline to follow-up suggests a downward trend in working memory, planning/problem-solving, verbal memory, and visuospatial integration.

CONCLUSION

Chemotherapy followed by reduced dose/volume of irradiation is an effective strategy resulting in long-term survival in patients with non-midline germinoma. Neuropsychological data suggest relatively minimal morbidity over time.

Unusual radiological and histological presentation of a diffuse leptomeningeal glioneuronal tumor (DLGNT) in a 13-year-old girl

Diffuse leptomeningeal glioneuronal tumors (DLGNTs) are newly recognized as an entity in the 2016 revision of the WHO Classification of tumors of the central nervous system. They typically present as diffuse leptomeningeal infiltrates along the neuraxis with focal and superficial involvement of the parenchyma. Here, we report a DLGNT with unusual radiological and histological features. A 13-year-old girl presented with scoliosis and back pain. Magnetic resonance imaging demonstrated a syrinx from C2 to T11 and an intramedullary mass from T6 to T9-10. No leptomeningeal involvement was recognized. Histological examination of the gross total resection specimen revealed a low-grade neuroepithelial neoplasm predominantly infiltrating the spinal cord and only focally involving the leptomeninges. Chromosome microarray identified co-deletion of the short arm of chromosome 1 and the long arm of chromosome 19 as well as fusion of the KIAA1549 and BRAF genes. Next-generation sequencing demonstrated wild-type alleles at the mutational hotspots of IDH1 (R132) and IDH2 (R140 and R172). In contrast to most reported DLGNTs, the tumor described in this manuscript was characterized by a predominant parenchymal component and only minor leptomeningeal involvement both radiographically and histologically. Our case, therefore, expands the spectrum of radiological and histopathological features of this new entity. It also highlights the critical role of molecular genetic testing in establishing the diagnosis of DLGNT in unusual cases.

Changing Trends in Brain Imaging Technique for Pediatric Patients with Ventriculoperitoneal Shunts

BACKGROUND

Children with ventriculoperitoneal shunts (VPS) undergoing brain computed tomography (CT) for shunt malfunction evaluation are at risk for later malignancy due to radiation exposure. We aimed to determine if and how hospitals have adopted radiation-avoiding magnetic resonance imaging (MRI) techniques.

METHODS

We performed a secondary analysis of the Pediatric Health Information System (PHIS) database. Children with VPS presenting to acute wards at 31 PHIS hospitals between January 1, 2007 and January 2, 2015 and receiving noncontrast neuroimaging on day of service 0/1 were included. Outcome measures were (1) incidence of MRI over time and (2) comparison of demographic characteristics between hospitals with MRI representing higher versus lower proportions (>15% or <15%) of total brain imaging.

RESULTS

MRIs increased by 18.1% from 2007 to 2015. Hospitals were assigned to high-use (n = 12) or minimal-use (n = 19) MRI groups based on year 2014/2015 MRI percentages. The only identified difference was an older mean age in the high-use group (8.1 vs. 7.5 years; p = 0.03).

CONCLUSIONS

MRI is increasingly used to evaluate patients with VPS. Hospitals with more MRI use had older patients and no increase in cost or length of stay. Initiating local quality improvement projects may help identify barriers to MRI uptake and increase use.

Allergic reactions and antiasparaginase antibodies in children with high-risk acute lymphoblastic leukemia: A children's oncology group report

BACKGROUND

The objectives of this study were to assess the incidence of clinical allergy and end-induction antiasparaginase (anti-ASNase) antibodies in children with high-risk acute lymphoblastic leukemia treated with pegylated (PEG) Escherichia coli ASNase and to determine whether they carry any prognostic significance.

METHODS

Of 2057 eligible patients, 1155 were allocated to augmented arms in which PEG ASNase replaced native ASNase postinduction. Erwinia chrysanthemi (Erwinia) ASNase could be used to replace native ASNase after allergy, if available. Allergy and survival data were complete for 990 patients. End-induction antibody titers were available for 600 patients.

RESULTS

During the consolidation phase, 289 of 990 patients (29.2%) had an allergic reaction. There were fewer allergic reactions to Erwinia ASNase than to native ASNase (odds ratio, 4.33; P < .0001) or PEG ASNase (odds ratio, 3.08; P < .0001) only during phase 1 of interim maintenance. There was no significant difference in 5-year event-free survival (EFS) between patients who received PEG ASNase throughout the entire study postinduction versus those who developed an allergic reaction to PEG ASNase during consolidation phase and subsequently received Erwinia ASNase (80.8% ± 2.8% and 81.6% ± 3.8%, respectively; P = .66). Patients who had positive antibody titers postinduction were more likely to have an allergic reaction to PEG ASNase (odds ratio, 2.4; P < .001). The 5-year EFS rate between patients who had negative versus positive antibody titers (80% ± 2.6% and 77.7% ± 4.3%, respectively; P = .68) and between patients who did not receive any ASNase postconsolidation and those who received PEG ASNase throughout the study (P = .22) were significantly different.

CONCLUSIONS

The current results demonstrate differences in the incidence rates of toxicity between ASNase preparations but not in EFS. The presence of anti-ASNase antibodies did not affect EFS.

Abstract B18: Presence of tumor-associated macrophages in SHH medulloblastoma

The concept of tumor-promoting inflammation is a recognized enabling characteristic of cancer. Tumor associated macrophages (TAMs), one of the main contributors to the tumor microenvironment, have been identified in many adult malignancies and in the MYCN non-amplified high risk neuroblastomas. TAMs have been shown to promote cancer via multiple mechanisms including tumor cell growth and survival, invasion, metastasis, angiogenesis, inflammation, and immune regulation. Recent studies in adult gliomas have demonstrated increased expression of macrophage/microglia associated genes in subtypes of gliomas, however little is known about the role of inflammation in medulloblastomas, the most common malignant childhood brain tumor.

In this study we examined the expression of inflammation-related genes and presence of TAMs in molecular subgroups of pediatric medulloblastoma. The molecular subgroups of medulloblastomas were initially identified using Human Exon Array (HuEx) microarray data from 168 samples (65 patients profiled at Children's Hospital Los Angeles and 103 from previously published cohort) using a modified algorithm based on non-negative matrix factorization. We then examined the inflammation and immunology related genes that were differentially expressed among the molecular subgroups and discovered greater expression of inflammation-related genes in tumors of the SHH molecular subgroup compared with those of the Group 3 and Group 4 subgroups. Gene expression analysis was then performed on 83 medulloblastoma samples using a custom-built TaqMan Low Density Array (TLDA) card containing 41 tumor-related and 4 inflammation-related genes that were significantly deregulated among medulloblastoma subgroups in the HuEx microarray analyses. Thirty-one of these genes were used to develop a signature predictive of molecular subgroup. The internal cross-validted error rate of the TLDA 31-gene signature was 8%, with predominant misclassifications occurring between Groups 3 and 4. The expression levels of CD163 and CSF1R, two markers associated with TAMs, were higher in tumors of the SHH subgroup compared to those in the WNT, Group 3, and Group 4 subgroups (CD163, t-test p=.02 for WNT and p&lt;0.001 for Groups 3 and 4; CSF1R, t-test p&lt;0.01 for all groups). To validate these findings, we performed immunohistochemical analysis of 51 primary and 3 recurrent medulloblastoma tumors using antibodies directed against CD163, which were then blindly graded by two neuropathologists. There were significantly greater numbers of macrophages observed in tumors of the SHH subgroup compared to those in Group 3 and Group 4 (t test p&lt;0.001 for both groups). Interestingly, macrophages in the desmoplastic or SHH tumors were concentrated in the poorly differentiated and highly proliferative internodular areas suggesting a tumor-proliferating role for these TAMs.

Our study reports the first evidence of the presence of TAMs in medulloblastomas and provides a novel 31-gene TLDA signature that accurately determines molecular subgroups of medulloblastomas. The increase in expression of macrophage related genes and intratumoral macrophages was strongly associated with the SHH subgroup of patients. The identification of TAMs in medulloblastomas provides opportunity for testing new therapies directed against TAMs such as CSF1R inhibitors, and the recognition of the importance of tumor microenvironment in childhood brain tumors.

Citation Format: Ashley Margol, Janahan Gnanachandran, Nathan Robison, Long Hung, Rebekah Kennedy, Marzieh Vali, Girish Dhall, Jonathan Finlay, Anat Epstein, Mark Krieger, Kathleen Dorris, Maryam Fouladi, Floyd Gilles, Alexander Judkins, Richard Sposto, Shahab Asgharzadeh. Presence of tumor-associated macrophages in SHH medulloblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B18.

PID1 (NYGGF4), a new growth-inhibitory gene in embryonal brain tumors and gliomas

PURPOSE

We present here the first report of PID1 (Phosphotyrosine Interaction Domain containing 1; NYGGF4) in cancer. PID1 was identified in 2006 as a gene that modulates insulin signaling and mitochondrial function in adipocytes and muscle cells.

EXPERIMENTAL DESIGN AND RESULTS

Using four independent medulloblastoma datasets, we show that mean PID1 mRNA levels were lower in unfavorable medulloblastomas (groups 3 and 4, and anaplastic histology) compared with favorable medulloblastomas (SHH and WNT groups, and desmoplastic/nodular histology) and with fetal cerebellum. In two large independent glioma datasets, PID1 mRNA was lower in glioblastomas (GBM), the most malignant gliomas, compared with other astrocytomas, oligodendrogliomas and nontumor brains. Neural and proneural GBM subtypes had higher PID1 mRNA compared with classical and mesenchymal GBM. Importantly, overall survival and radiation-free progression-free survival were longer in medulloblastoma patients whose tumors had higher PID1 mRNA (univariate and multivariate analyses). Higher PID1 mRNA also correlated with longer overall survival in patients with glioma and GBM. In cell culture, overexpression of PID1 inhibited colony formation in medulloblastoma, atypical teratoid rhabdoid tumor (ATRT), and GBM cell lines. Increasing PID1 also increased cell death and apoptosis, inhibited proliferation, induced mitochondrial depolaization, and decreased serum-mediated phosphorylation of AKT and ERK in medulloblastoma, ATRT, and/or GBM cell lines, whereas siRNA to PID1 diminished mitochondrial depolarization.

CONCLUSIONS

These data are the first to link PID1 to cancer and suggest that PID1 may have a tumor inhibitory function in these pediatric and adult brain tumors.

Medullublastoma expresses CD1d and can be targeted for immunotherapy with NKT cells (P4453)

Medulloblastoma (MB) is the most common brain tumor of childhood. Current therapies are toxic and often not curative that necessitates development of targeted immunotherapy. However, little is known about immunobiology of this tumor. In this study, we show that MB cells in 9 of 20 primary tumors express CD1d, an antigen-presenting molecule for Natural Killer T cells (NKTs). Quantitative RT-PCR analysis of 61 primary tumors revealed a high level of CD1d mRNA expression in a molecular subgroup characterized by overactivation of Sonic Hedgehog (SHH) oncogene. CD1d-positive MB cells cross-presented glycolipid antigens to activate NKT-cell cytotoxicity. Intracranial injection of human NKTs resulted in regression of orthotopic MB xenografts in NOD/SCID mice. Importantly, the numbers and functional properties of peripheral blood type-I NKTs were preserved in MB patients. Therefore, CD1d is expressed on tumor cells in a subset of MB patients and represents a novel target for immunotherapy of this brain tumor.