- Neuro Oncology
Assistant Professor, Neurology & Neurological Sciences
Assistant Professor (By courtesy), Neurosurgery
Assistant Professor (By courtesy), Pediatrics - Operations
Assistant Professor (By courtesy), Pathology
Member, Child Health Research Institute
Member, Stanford Cancer Institute
Member, Stanford Neurosciences Institute
Honors & Awards
Young Investigator Award, Hagerty Foundation for Glioma Research (2006)
K08 Mentored Clinical Scientist Career Development Award, National Institutes of Neurological Disorders and Stroke (2010 - 2015)
Peter A. Steck Memorial Award, Pediatric Brain Tumor Foundation (2011)
Basic Science IV Award, California Institute of Regenerative Medicine (CIRM) (2012 - 2015)
‘A’ Award, Alex’s Lemonade Stand Foundation (2012-2015)
New Faculty Physician Scientist Translational Research Award, California Institute of Regenerative Medicine (CIRM) (2013 - 2018)
Neuro-Oncology Investigator Award, American Academy of Neurology (2017)
Boards, Advisory Committees, Professional Organizations
Chair, Brainstem Glioma Working Group, Pediatric Brain Tumor Consortium (2013 - Present)
Member, Pediatric Brain Tumor Consortium Translational Biology Committee (2012 - Present)
Institutional Co-PI, Pediatric Brain Tumor Consortium (PBTC) (2012 - Present)
Member, Children’s Oncology Group (COG) (2011 - Present)
Board Certification: Neuro-Oncology, United Council for Neurologic Subspecialties (2013)
Fellowship:Stanford University School of Medicine (2010) CA
Residency:Massachusetts General Hospital (2008) MA
Residency:Brigham and Women's Hospital Harvard Medical School (2008) MA
Internship:Stanford University (2005) CA
Medical Education:Stanford University (2004) CA
Subspecialty Board Certification, United Council for Neurological Subspecialties, Neuro-Oncology (2013)
Board Certification: Neurology, American Board of Psychiatry and Neurology (2008)
PhD, Stanford University, Neuroscience (2004)
MD, Stanford University (2004)
Current Research and Scholarly Interests
Much of brain development occurs after birth. Maturation of complex neural circuitry necessary for high-level cognitive and motor functions occurs throughout childhood and young adulthood. Central to the process of developing or strengthening a functional neural circuit is the generation of new glial cells for neuronal support, synapse formation and myelination. In some brain regions, such as the hippocampus, new neuron production occurs throughout postnatal life and is believed to subserve normal memory function.
The Monje Lab studies the molecular and cellular mechanisms of postnatal neurodevelopment. This includes microenvironmental influences on neural precursor cell fate choice in normal neurodevelopment and in disease states. Areas of emphasis include neuronal instruction of gliogenesis, cellular contributions to the neurogenic and gliogenic signaling microenvironment, molecular determinants of neural precursor cell fate, and the role of neural precursor cells in oncogenesis and repair mechanisms. As a practicing neurologist and Neuro-oncologist, Dr Monje is particularly interested in the roles for neural precursor cell function and dysfunction in the origins of pediatric brain tumors and the consequences of cancer treatment. As a paradigm of pediatric gliogenesis, we have been focusing on brainstem tumors, whose spatial and temporal specificity bespeak an underlying developmental cause.
Independent Studies (19)
- Directed Investigation
BIOE 392 (Win, Spr)
- Directed Reading in Cancer Biology
CBIO 299 (Win, Spr)
- Directed Reading in Neurology and Neurological Science
NENS 299 (Aut, Win, Spr)
- Directed Reading in Neurosciences
NEPR 299 (Aut, Win, Spr)
- Directed Reading in Stem Cell Biology and Regenerative Medicine
STEMREM 299 (Win, Spr)
- Early Clinical Experience in Neurology and Neurological Sciences
NENS 280 (Aut, Win, Spr)
- Graduate Research
CBIO 399 (Aut, Win, Spr)
- Graduate Research
NENS 399 (Aut, Win, Spr)
- Graduate Research
NEPR 399 (Aut, Win, Spr, Sum)
- Graduate Research
STEMREM 399 (Aut, Win, Spr, Sum)
HUMBIO 194 (Aut, Win, Spr)
- Medical Scholars Research
NENS 370 (Aut, Win, Spr, Sum)
- Medical Scholars Research
STEMREM 370 (Win, Spr)
- Out-of-Department Advanced Research Laboratory in Bioengineering
BIOE 191X (Aut, Win, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Aut, Win, Spr)
- Research in Human Biology
HUMBIO 193 (Aut, Win, Spr)
- Teaching in Cancer Biology
CBIO 260 (Spr)
- Undergraduate Research
NENS 199 (Aut, Win, Spr)
- Undergraduate Research
STEMREM 199 (Aut, Win, Spr, Sum)
- Directed Investigation
Transcriptional Dependencies in Diffuse Intrinsic Pontine Glioma
2017; 31 (5): 635-?
Diffuse intrinsic pontine glioma (DIPG) is a fatal pediatric cancer with limited therapeutic options. The majority of cases of DIPG exhibit a mutation in histone-3 (H3K27M) that results in oncogenic transcriptional aberrancies. We show here that DIPG is vulnerable to transcriptional disruption using bromodomain inhibition or CDK7 blockade. Targeting oncogenic transcription through either of these methods synergizes with HDAC inhibition, and DIPG cells resistant to HDAC inhibitor therapy retain sensitivity to CDK7 blockade. Identification of super-enhancers in DIPG provides insights toward the cell of origin, highlighting oligodendroglial lineage genes, and reveals unexpected mechanisms mediating tumor viability and invasion, including potassium channel function and EPH receptor signaling. The findings presented demonstrate transcriptional vulnerabilities and elucidate previously unknown mechanisms of DIPG pathobiology.
View details for DOI 10.1016/j.ccell.2017.03.011
View details for Web of Science ID 000400738600008
View details for PubMedID 28434841
Neural Precursor-Derived Pleiotrophin Mediates Subventricular Zone Invasion by Glioma.
2017; 170 (5): 845–59.e19
The lateral ventricle subventricular zone (SVZ) is a frequent and consequential site of pediatric and adult glioma spread, but the cellular and molecular mechanisms mediating this are poorly understood. We demonstrate that neural precursor cell (NPC):glioma cell communication underpins this propensity of glioma to colonize the SVZ through secretion of chemoattractant signals toward which glioma cells home. Biochemical, proteomic, and functional analyses of SVZ NPC-secreted factors revealed the neurite outgrowth-promoting factor pleiotrophin, along with required binding partners SPARC/SPARCL1 and HSP90B, as key mediators of this chemoattractant effect. Pleiotrophin expression is strongly enriched in the SVZ, and pleiotrophin knock down starkly reduced glioma invasion of the SVZ in the murine brain. Pleiotrophin, in complex with the binding partners, activated glioma Rho/ROCK signaling, and ROCK inhibition decreased invasion toward SVZ NPC-secreted factors. These findings demonstrate a pathogenic role for NPC:glioma interactions and potential therapeutic targets to limit glioma invasion. PAPERCLIP.
View details for DOI 10.1016/j.cell.2017.07.016
View details for PubMedID 28823557
View details for PubMedCentralID PMC5587159
Functionally defined therapeutic targets in diffuse intrinsic pontine glioma
2015; 21 (6): 555-559
Diffuse intrinsic pontine glioma (DIPG) is a fatal childhood cancer. We performed a chemical screen in patient-derived DIPG cultures along with RNA-seq analyses and integrated computational modeling to identify potentially effective therapeutic strategies. The multi-histone deacetylase inhibitor panobinostat demonstrated therapeutic efficacy both in vitro and in DIPG orthotopic xenograft models. Combination testing of panobinostat and the histone demethylase inhibitor GSK-J4 revealed that the two had synergistic effects. Together, these data suggest a promising therapeutic strategy for DIPG.
View details for DOI 10.1038/nm.3855
View details for Web of Science ID 000355778300010
View details for PubMedID 25939062
Neuronal Activity Promotes Glioma Growth through Neuroligin-3 Secretion
2015; 161 (4): 803-816
Active neurons exert a mitogenic effect on normal neural precursor and oligodendroglial precursor cells, the putative cellular origins of high-grade glioma (HGG). By using optogenetic control of cortical neuronal activity in a patient-derived pediatric glioblastoma xenograft model, we demonstrate that active neurons similarly promote HGG proliferation and growth in vivo. Conditioned medium from optogenetically stimulated cortical slices promoted proliferation of pediatric and adult patient-derived HGG cultures, indicating secretion of activity-regulated mitogen(s). The synaptic protein neuroligin-3 (NLGN3) was identified as the leading candidate mitogen, and soluble NLGN3 was sufficient and necessary to promote robust HGG cell proliferation. NLGN3 induced PI3K-mTOR pathway activity and feedforward expression of NLGN3 in glioma cells. NLGN3 expression levels in human HGG negatively correlated with patient overall survival. These findings indicate the important role of active neurons in the brain tumor microenvironment and identify secreted NLGN3 as an unexpected mechanism promoting neuronal activity-regulated cancer growth.
View details for DOI 10.1016/j.cell.2015.04.012
View details for Web of Science ID 000354175200014
View details for PubMedID 25913192
View details for PubMedCentralID PMC4447122
- Neuronal Activity Promotes Oligodendrogenesis and Adaptive Myelination in the Mammalian Brain SCIENCE 2014; 344 (6183): 487-?
- Subventricular spread of diffuse intrinsic pontine glioma. Acta neuropathologica 2014
Hedgehog-responsive candidate cell of origin for diffuse intrinsic pontine glioma
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2011; 108 (11): 4453-4458
Diffuse intrinsic pontine gliomas (DIPGs) are highly aggressive tumors of childhood that are almost universally fatal. Our understanding of this devastating cancer is limited by a dearth of available tissue for study and by the lack of a faithful animal model. Intriguingly, DIPGs are restricted to the ventral pons and occur during a narrow window of middle childhood, suggesting dysregulation of a postnatal neurodevelopmental process. Here, we report the identification of a previously undescribed population of immunophenotypic neural precursor cells in the human and murine brainstem whose temporal and spatial distributions correlate closely with the incidence of DIPG and highlight a candidate cell of origin. Using early postmortem DIPG tumor tissue, we have established in vitro and xenograft models and find that the Hedgehog (Hh) signaling pathway implicated in many developmental and oncogenic processes is active in DIPG tumor cells. Modulation of Hh pathway activity has functional consequences for DIPG self-renewal capacity in neurosphere culture. The Hh pathway also appears to be active in normal ventral pontine precursor-like cells of the mouse, and unregulated pathway activity results in hypertrophy of the ventral pons. Together, these findings provide a foundation for understanding the cellular and molecular origins of DIPG, and suggest that the Hh pathway represents a potential therapeutic target in this devastating pediatric tumor.
View details for DOI 10.1073/pnas.1101657108
View details for Web of Science ID 000288450900040
View details for PubMedID 21368213
Impaired human hippocampal neurogenesis after treatment for central nervous system
ANNALS OF NEUROLOGY
2007; 62 (5): 515-520
The effects of cancer treatments such as cranial radiation and chemotherapy on human hippocampal neurogenesis remain unknown. In this study, we examine neuropathological markers of neurogenesis and inflammation in the human hippocampus after treatment for acute myelogenous leukemia or medulloblastoma. We demonstrate a persistent radiation-induced microglial inflammation that is accompanied by nearly complete inhibition of neurogenesis after cancer treatment. These findings are consistent with preclinical animal studies and suggest potential therapeutic strategies.
View details for DOI 10.1002/ana.21214
View details for Web of Science ID 000251383300012
View details for PubMedID 17786983
Inflammatory blockade restores adult hippocampal neurogenesis
2003; 302 (5651): 1760-1765
Cranial radiation therapy causes a progressive decline in cognitive function that is linked to impaired neurogenesis. Chronic inflammation accompanies radiation injury, suggesting that inflammatory processes may contribute to neural stem cell dysfunction. Here, we show that neuroinflammation alone inhibits neurogenesis and that inflammatory blockade with indomethacin, a common nonsteroidal anti-inflammatory drug, restores neurogenesis after endotoxin-induced inflammation and augments neurogenesis after cranial irradiation.
View details for Web of Science ID 000186970100047
View details for PubMedID 14615545
Irradiation induces neural precursor-cell dysfunction
2002; 8 (9): 955-962
In both pediatric and adult patients, cranial radiation therapy causes a debilitating cognitive decline that is poorly understood and currently untreatable. This decline is characterized by hippocampal dysfunction, and seems to involve a radiation-induced decrease in postnatal hippocampal neurogenesis. Here we show that the deficit in neurogenesis reflects alterations in the microenvironment that regulates progenitor-cell fate, as well as a defect in the proliferative capacity of the neural progenitor-cell population. Not only is hippocampal neurogenesis ablated, but the remaining neural precursors adopt glial fates and transplants of non-irradiated neural precursor cells fail to differentiate into neurons in the irradiated hippocampus. The inhibition of neurogenesis is accompanied by marked alterations in the neurogenic microenvironment, including disruption of the microvascular angiogenesis associated with adult neurogenesis and a marked increase in the number and activation status of microglia within the neurogenic zone. These findings provide clear targets for future therapeutic interventions.
View details for DOI 10.1038/nm749
View details for Web of Science ID 000177757900030
View details for PubMedID 12161748
Chemoradiation impairs normal developmental cortical thinning in medulloblastoma.
Journal of neuro-oncology
Medulloblastoma patients are treated with surgery, radiation and chemotherapy. Radiation dose to the temporal lobe may be associated with neurocognitive sequelae. Longitudinal changes of temporal lobe cortical thickness may result from neurodevelopmental processes such as synaptic pruning. This study applies longitudinal image analysis to compare developmental change in cortical thickness in medulloblastoma (MB) patients who were treated by combined modality therapy to that of cerebellar juvenile pilocytic astrocytoma (JPA) patients who were treated by surgery alone. We hypothesized that the rates of developmental change in cortical thickness would differ between these two groups. This retrospective cohort study assessed changes in cortical thickness over time between MB and JPA patients. High-resolution magnetic resonance (MR) images of 14 MB and 7 JPA subjects were processed to measure cortical thickness of bilateral temporal lobe substructures. A linear mixed effects model was used to identify differences in substructure longitudinal changes in cortical thickness. The left temporal lobe exhibited overall increased cortical thickness in MB patients relative to JPA patients who showed overall cortical thinning (mean annual cortical thickness change: MB 0.14 mm/year versus JPA -0.018 mm/year across all substructures), particularly in the inferior temporal lobe substructures (p < 0.0001). The cortical thickness change of the right temporal lobe substructures exhibited similar, though attenuated trends (p = 0.002). MB patients exhibit overall increased cortical thickness rather than cortical thinning as seen in JPA patients and as expected in normal cortical development. These observations are possibly due to chemoradiation induced-disruption of normal neuronal mechanisms. Longitudinal image analysis may identify early biomarkers for neurocognitive function with routine imaging.
View details for DOI 10.1007/s11060-017-2453-5
View details for PubMedID 28534154
Decoupling genetics, lineages, and microenvironment in IDH-mutant gliomas by single-cell RNA-seq
2017; 355 (6332): 1391-?
Tumor subclasses differ according to the genotypes and phenotypes of malignant cells as well as the composition of the tumor microenvironment (TME). We dissected these influences in isocitrate dehydrogenase (IDH)-mutant gliomas by combining 14,226 single-cell RNA sequencing (RNA-seq) profiles from 16 patient samples with bulk RNA-seq profiles from 165 patient samples. Differences in bulk profiles between IDH-mutant astrocytoma and oligodendroglioma can be primarily explained by distinct TME and signature genetic events, whereas both tumor types share similar developmental hierarchies and lineages of glial differentiation. As tumor grade increases, we find enhanced proliferation of malignant cells, larger pools of undifferentiated glioma cells, and an increase in macrophage over microglia expression programs in TME. Our work provides a unifying model for IDH-mutant gliomas and a general framework for dissecting the differences among human tumor subclasses.
View details for DOI 10.1126/science.aai8478
View details for Web of Science ID 000397809500034
View details for PubMedID 28360267
Disrupting the CD47-SIRP alpha anti-phagocytic axis by a humanized anti-CD47 antibody is an efficacious treatment for malignant pediatric brain tumors
SCIENCE TRANSLATIONAL MEDICINE
2017; 9 (381)
Morbidity and mortality associated with pediatric malignant primary brain tumors remain high in the absence of effective therapies. Macrophage-mediated phagocytosis of tumor cells via blockade of the anti-phagocytic CD47-SIRPα interaction using anti-CD47 antibodies has shown promise in preclinical xenografts of various human malignancies. We demonstrate the effect of a humanized anti-CD47 antibody, Hu5F9-G4, on five aggressive and etiologically distinct pediatric brain tumors: group 3 medulloblastoma (primary and metastatic), atypical teratoid rhabdoid tumor, primitive neuroectodermal tumor, pediatric glioblastoma, and diffuse intrinsic pontine glioma. Hu5F9-G4 demonstrated therapeutic efficacy in vitro and in vivo in patient-derived orthotopic xenograft models. Intraventricular administration of Hu5F9-G4 further enhanced its activity against disseminated medulloblastoma leptomeningeal disease. Notably, Hu5F9-G4 showed minimal activity against normal human neural cells in vitro and in vivo, a phenomenon reiterated in an immunocompetent allograft glioma model. Thus, Hu5F9-G4 is a potentially safe and effective therapeutic agent for managing multiple pediatric central nervous system malignancies.
View details for DOI 10.1126/scitranslmed.aaf2968
View details for Web of Science ID 000396307600001
View details for PubMedID 28298418
A Protocol for Rapid Post-mortem Cell Culture of Diffuse Intrinsic Pontine Glioma (DIPG)
JOVE-JOURNAL OF VISUALIZED EXPERIMENTS
Diffuse Intrinsic Pontine Glioma (DIPG) is a childhood brainstem tumor that carries a universally fatal prognosis. Because surgical resection is not a viable treatment strategy and biopsy is not routinely performed, the availability of patient samples for research is limited. Consequently, efforts to study this disease have been challenged by a paucity of faithful disease models. To address this need, we describe here a protocol for the rapid processing of post-mortem autopsy tissue samples in order to generate durable patient-derived cell culture models that can be used in in vitro assays or in vivo orthotopic xenograft experiments. These models can be used to screen for potential drug targets and to study fundamental pathobiological processes within DIPG. This protocol can further be extended to analyze and isolate tumor and microenvironmental cells using Fluorescence-activated Cell Sorting (FACS), which enables subsequent analysis of gene expression, protein expression, or epigenetic modifications of DNA at the bulk cell or single cell level. Finally, this protocol can also be adapted to generate patient-derived cultures for other central nervous system tumors.
View details for DOI 10.3791/55360
View details for Web of Science ID 000397848300065
View details for PubMedID 28362421
- Pediatric high-grade glioma: biologically and clinically in need of new thinking NEURO-ONCOLOGY 2017; 19 (2): 153-161
The international diffuse intrinsic pontine glioma registry: an infrastructure to accelerate collaborative research for an orphan disease.
Journal of neuro-oncology
Diffuse intrinsic pontine glioma (DIPG), a rare, often fatal childhood brain tumor, remains a major therapeutic challenge. In 2012, investigators, funded by the DIPG Collaborative (a philanthropic partnership among 29 private foundations), launched the International DIPG Registry (IDIPGR) to advance understanding of DIPG. Comprised of comprehensive deidentified but linked clinical, imaging, histopathological, and genomic repositories, the IDIPGR uses standardized case report forms for uniform data collection; serial imaging and histopathology are centrally reviewed by IDIPGR neuro-radiologists and neuro-pathologists, respectively. Tissue and genomic data, and cell cultures derived from autopsies coordinated by the IDIPGR are available to investigators for studies approved by the Scientific Advisory Committee. From April 2012 to December 2016, 670 patients diagnosed with DIPG have been enrolled from 55 participating institutions in the US, Canada, Australia and New Zealand. The radiology repository contains 3558 studies from 448 patients. The pathology repository contains tissue on 81 patients with another 98 samples available for submission. Fresh DIPG tissue from seven autopsies has been sent to investigators to develop primary cell cultures. The bioinformatics repository contains next-generation sequencing data on 66 tumors. Nine projects using data/tissue from the IDIPGR by 13 principle investigators from around the world are now underway. The IDIPGR, a successful alliance among philanthropic agencies and investigators, has developed and maintained a highly collaborative, hypothesis-driven research infrastructure for interdisciplinary and translational projects in DIPG to improve diagnosis, response assessment, treatment and outcome for patients.
View details for DOI 10.1007/s11060-017-2372-5
View details for PubMedID 28093680
Diffuse Intrinsic Pontine Glioma: New Pathophysiological Insights and Emerging Therapeutic Targets
2017; 15 (1): 88-97
Diffuse Intrinsic Pontine Glioma (DIPG) is the leading cause of brain tumor-related death in children, with median survival of less than one year. Despite decades of clinical trials, there has been no improvement in prognosis since the introduction of radiotherapy over thirty years ago.To review the clinical features and current treatment challenges of DIPG, and discuss emerging insights into the unique genomic and epigenomic mechanisms driving DIPG pathogenesis that present new opportunities for the identification of therapeutic targets.In recent years, an increased availability of biopsy and rapid autopsy tissue samples for preclinical investigation has combined with the advent of new genomic and epigenomic profiling tools to yield remarkable advancements in our understanding of DIPG disease mechanisms. As well, a deeper understanding of the developmental context of DIPG is shedding light on therapeutic targets in the microenvironment of the childhood brain.
View details for DOI 10.2174/1570159X14666160509123229
View details for Web of Science ID 000391855800010
View details for PubMedID 27157264
Single-cell RNA-seq supports a developmental hierarchy in human oligodendroglioma.
Although human tumours are shaped by the genetic evolution of cancer cells, evidence also suggests that they display hierarchies related to developmental pathways and epigenetic programs in which cancer stem cells (CSCs) can drive tumour growth and give rise to differentiated progeny. Yet, unbiased evidence for CSCs in solid human malignancies remains elusive. Here we profile 4,347 single cells from six IDH1 or IDH2 mutant human oligodendrogliomas by RNA sequencing (RNA-seq) and reconstruct their developmental programs from genome-wide expression signatures. We infer that most cancer cells are differentiated along two specialized glial programs, whereas a rare subpopulation of cells is undifferentiated and associated with a neural stem cell expression program. Cells with expression signatures for proliferation are highly enriched in this rare subpopulation, consistent with a model in which CSCs are primarily responsible for fuelling the growth of oligodendroglioma in humans. Analysis of copy number variation (CNV) shows that distinct CNV sub-clones within tumours display similar cellular hierarchies, suggesting that the architecture of oligodendroglioma is primarily dictated by developmental programs. Subclonal point mutation analysis supports a similar model, although a full phylogenetic tree would be required to definitively determine the effect of genetic evolution on the inferred hierarchies. Our single-cell analyses provide insight into the cellular architecture of oligodendrogliomas at single-cell resolution and support the cancer stem cell model, with substantial implications for disease management.
View details for DOI 10.1038/nature20123
View details for PubMedID 27806376
Myelin plasticity in the central nervous system.
2016; 110: 563-573
Myelin sheaths, specialized segments of oligodendrocyte (OL) plasma membranes in the central nervous system (CNS), facilitate fast, saltatory conduction of action potentials down axons. Changes to the fine structure of myelin in a neural circuit, including sheath thickness and internode length (length of myelin segments between nodes of Ranvier), are expected to affect conduction velocity of action potentials. Myelination of the mammalian CNS occurs in a stereotyped, progressive pattern and continues well into adulthood in humans. Recent evidence from zebrafish, rodents, non-human primates, and humans suggests that myelination may be sensitive to experiences during development and adulthood, and that varying levels of neuronal activity may underlie these experience-dependent changes in myelin and myelin-forming cells. Several cellular, molecular, and epigenetic mechanisms have been investigated as contributors to myelin plasticity. A deeper understanding of myelin plasticity and its underlying mechanisms may provide insights into diseases involving myelin damage or dysregulation. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.
View details for DOI 10.1016/j.neuropharm.2015.08.001
View details for PubMedID 26282119
Pediatric high-grade glioma: biologically and clinically in need of new thinking.
High-grade gliomas in children are different from those that arise in adults. Recent collaborative molecular analyses of these rare cancers have revealed previously unappreciated connections among chromatin regulation, developmental signaling, and tumorigenesis. As we begin to unravel the unique developmental origins and distinct biological drivers of this heterogeneous group of tumors, clinical trials need to keep pace. It is important to avoid therapeutic strategies developed purely using data obtained from studies on adult glioblastoma. This approach has resulted in repetitive trials and ineffective treatments being applied to these children, with limited improvement in clinical outcome. The authors of this perspective, comprising biology and clinical expertise in the disease, recently convened to discuss the most effective ways to translate the emerging molecular insights into patient benefit. This article reviews our current understanding of pediatric high-grade glioma and suggests approaches for innovative clinical management.
View details for PubMedID 27282398
Epigenetic targeting of Hedgehog pathway transcriptional output through BET bromodomain inhibition
2014; 20 (7): 732-740
Hedgehog signaling drives oncogenesis in several cancers, and strategies targeting this pathway have been developed, most notably through inhibition of Smoothened (SMO). However, resistance to Smoothened inhibitors occurs by genetic changes of Smoothened or other downstream Hedgehog components. Here we overcome these resistance mechanisms by modulating GLI transcription through inhibition of bromo and extra C-terminal (BET) bromodomain proteins. We show that BRD4 and other BET bromodomain proteins regulate GLI transcription downstream of SMO and suppressor of fused (SUFU), and chromatin immunoprecipitation studies reveal that BRD4 directly occupies GLI1 and GLI2 promoters, with a substantial decrease in engagement of these sites after treatment with JQ1, a small-molecule inhibitor targeting BRD4. Globally, genes associated with medulloblastoma-specific GLI1 binding sites are downregulated in response to JQ1 treatment, supporting direct regulation of GLI activity by BRD4. Notably, patient- and GEMM (genetically engineered mouse model)-derived Hedgehog-driven tumors (basal cell carcinoma, medulloblastoma and atypical teratoid rhabdoid tumor) respond to JQ1 even when harboring genetic lesions rendering them resistant to Smoothened antagonists. Altogether, our results reveal BET proteins as critical regulators of Hedgehog pathway transcriptional output and nominate BET bromodomain inhibitors as a strategy for treating Hedgehog-driven tumors with emerged or a priori resistance to Smoothened antagonists.
View details for Web of Science ID 000338689500015
Human pontine glioma cells can induce murine tumors.
2014; 127 (6): 897-909
Diffuse intrinsic pontine glioma (DIPG), with a median survival of only 9 months, is the leading cause of pediatric brain cancer mortality. Dearth of tumor tissue for research has limited progress in this disease until recently. New experimental models for DIPG research are now emerging. To develop preclinical models of DIPG, two different methods were adopted: cells obtained at autopsy (1) were directly xenografted orthotopically into the pons of immunodeficient mice without an intervening cell culture step or (2) were first cultured in vitro and, upon successful expansion, injected in vivo. Both strategies resulted in pontine tumors histopathologically similar to the original human DIPG tumors. However, following the direct transplantation method all tumors proved to be composed of murine and not of human cells. This is in contrast to the indirect method that included initial in vitro culture and resulted in xenografts comprising human cells. Of note, direct injection of cells obtained postmortem from the pons and frontal lobe of human brains not affected by cancer did not give rise to neoplasms. The murine pontine tumors exhibited an immunophenotype similar to human DIPG, but were also positive for microglia/macrophage markers, such as CD45, CD68 and CD11b. Serial orthotopic injection of these murine cells results in lethal tumors in recipient mice. Direct injection of human DIPG cells in vivo can give rise to malignant murine tumors. This represents an important caveat for xenotransplantation models of DIPG. In contrast, an initial in vitro culture step can allow establishment of human orthotopic xenografts. The mechanism underlying this phenomenon observed with direct xenotransplantation remains an open question.
View details for DOI 10.1007/s00401-014-1272-4
View details for PubMedID 24777482
Recurrent activating ACVR1 mutations in diffuse intrinsic pontine glioma
2014; 46 (5): 457-461
Diffuse intrinsic pontine gliomas (DIPGs) are highly infiltrative malignant glial neoplasms of the ventral pons that, due to their location within the brain, are unsuitable for surgical resection and consequently have a universally dismal clinical outcome. The median survival time is 9-12 months, with neither chemotherapeutic nor targeted agents showing substantial survival benefit in clinical trials in children with these tumors. We report the identification of recurrent activating mutations in the ACVR1 gene, which encodes a type I activin receptor serine/threonine kinase, in 21% of DIPG samples. Strikingly, these somatic mutations (encoding p.Arg206His, p.Arg258Gly, p.Gly328Glu, p.Gly328Val, p.Gly328Trp and p.Gly356Asp substitutions) have not been reported previously in cancer but are identical to mutations found in the germ line of individuals with the congenital childhood developmental disorder fibrodysplasia ossificans progressiva (FOP) and have been shown to constitutively activate the BMP-TGF-β signaling pathway. These mutations represent new targets for therapeutic intervention in this otherwise incurable disease.
View details for DOI 10.1038/ng.2925
View details for Web of Science ID 000335422900011
View details for PubMedID 24705252
Diffusion-weighted MRI derived apparent diffusion coefficient identifies prognostically distinct subgroups of pediatric diffuse intrinsic pontine glioma.
Journal of neuro-oncology
2014; 117 (1): 175-182
While pediatric diffuse intrinsic pontine gliomas (DIPG) remain fatal, recent data have shown subgroups with distinct molecular biology and clinical behavior. We hypothesized that diffusion-weighted MRI can be used as a prognostic marker to stratify DIPG subsets with distinct clinical behavior. Apparent diffusion coefficient (ADC) values derived from diffusion-weighted MRI were computed in 20 consecutive children with treatment-naïve DIPG tumors. The median ADC for the cohort was used to stratify the tumors into low and high ADC groups. Survival, gender, therapy, and potential steroid effects were compared between the ADC groups. Median age at diagnosis was 6.6 (range 2.3-13.2) years, with median follow-up seven (range 1-36) months. There were 14 boys and six girls. Seventeen patients received radiotherapy, five received chemotherapy, and six underwent cerebrospinal fluid diversion. The median ADC of 1,295 × 10(-6) mm(2)/s for the cohort partitioned tumors into low or high diffusion groups, which had distinct median survivals of 3 and 13 months, respectively (log-rank p < 0.001). Low ADC tumors were found only in boys, whereas high ADC tumors were found in both boys and girls. Available tissue specimens in three low ADC tumors demonstrated high-grade histology, whereas one high ADC tumor demonstrated low-grade histology with a histone H3.1 K27M mutation and high-grade metastatic lesion at autopsy. ADC derived from diffusion-weighted MRI may identify prognostically distinct subgroups of pediatric DIPG.
View details for DOI 10.1007/s11060-014-1375-8
View details for PubMedID 24522717
Reduced H3K27me3 and DNA Hypomethylation Are Major Drivers of Gene Expression in K27M Mutant Pediatric High-Grade Gliomas.
2013; 24 (5): 660-672
Two recurrent mutations, K27M and G34R/V, within histone variant H3.3 were recently identified in ∼50% of pHGGs. Both mutations define clinically and biologically distinct subgroups of pHGGs. Here, we provide further insight about the dominant-negative effect of K27M mutant H3.3, leading to a global reduction of the repressive histone mark H3K27me3. We demonstrate that this is caused by aberrant recruitment of the PRC2 complex to K27M mutant H3.3 and enzymatic inhibition of the H3K27me3-establishing methyltransferase EZH2. By performing chromatin immunoprecipitation followed by next-generation sequencing and whole-genome bisulfite sequencing in primary pHGGs, we show that reduced H3K27me3 levels and DNA hypomethylation act in concert to activate gene expression in K27M mutant pHGGs.
View details for DOI 10.1016/j.ccr.2013.10.006
View details for PubMedID 24183680
Functional and structural differences in the hippocampus associated with memory deficits in adult survivors of acute lymphoblastic leukemia
PEDIATRIC BLOOD & CANCER
2013; 60 (2): 293-300
Radiation and chemotherapy targeted to the central nervous system (CNS) can cause cognitive impairment, including impaired memory. These memory impairments may be referable to damage to hippocampal structures resulting from CNS treatment.In the present study, we explored episodic memory and its neuroimaging correlates in 10 adult survivors of childhood acute lymphoblastic leukemia (ALL) treated with cranial radiation therapy and both systemic and intrathecal chemotherapy and 10 controls matched for age and sex, using a subsequent memory paradigm after episodic encoding of visual scenes.We report behavioral, structural, and functional changes in the brains of the adult survivors. They demonstrated poorer recognition memory, hippocampal atrophy, and altered blood oxygenation level-dependent (BOLD) signal in the hippocampus. Whole brain statistical map analysis revealed increased BOLD signal/activation in several brain regions during unsuccessful encoding in ALL survivors, potentially reflecting ineffective neural recruitment. Individual differences in memory performance in ALL participants were related to magnitude of BOLD response in regions associated with successful encoding.Taken together, these findings describe long term neuroimaging correlates of cognitive dysfunction after childhood exposure to CNS-targeted cancer therapies, suggesting enduring damage to episodic memory systems.
View details for DOI 10.1002/pbc.24263
View details for Web of Science ID 000312557600021
View details for PubMedID 22887801
Effect of cancer therapy on neural stem cells: implications for cognitive function
CURRENT OPINION IN ONCOLOGY
2012; 24 (6): 672-678
Modern cancer therapies have allowed for a dramatic increase in the survival rates in both children and adults. However, a frequent and unfortunate side-effect of cancer therapy is a long-term decline in neurocognitive function. Specifically, cranial radiation therapy markedly alters memory processes, while chemotherapeutic agents are correlated with deficits in attention, concentration, and speed of information processing. Here, we describe the putative cellular etiologies of cancer treatment-induced cognitive decline, with an emphasis on the role of neural stem and precursor cell dysfunction.New studies highlight the lasting effects of chemotherapy on memory, executive function, attention, and speed of information processing up to 20 years following chemotherapy. Cognitive decrements are associated with decreased white-matter integrity as well as alterations in stem cell function in humans and rodent models of cancer therapy. Genetic polymorphisms may underlie differential sensitivity of certain individuals to the neurological consequences of chemotherapy. Increasing data support the concept that disruption of normal neural stem and precursor cell function is an important causative factor for the cognitive deficits that result from cancer therapy in both children and adults.Further studies are needed to elucidate the role of chemotherapy on cell-intrinsic processes and cellular microenvironments. Further, the effects of the new generation of targeted molecular therapies on neural stem and progenitor cell function remains largely untested. Understanding the mechanisms behind cancer therapy-induced damage to neural stem and precursor cell populations will elucidate neuroprotective and cell replacement strategies aimed at preserving cognition after cancer therapy.
View details for DOI 10.1097/CCO.0b013e3283571a8e
View details for Web of Science ID 000310361500011
View details for PubMedID 22913969
Cognitive side effects of cancer therapy demonstrate a functional role for adult neurogenesis
BEHAVIOURAL BRAIN RESEARCH
2012; 227 (2): 376-379
Cancer therapies frequently result in a spectrum of neurocognitive deficits that include impaired learning, memory, attention and speed of information processing. Damage to dynamic neural progenitor cell populations in the brain are emerging as important etiologic factors. Radiation and chemotherapy-induced damage to neural progenitor populations responsible for adult hippocampal neurogenesis and for maintenance of subcortical white matter integrity are now believed to play major roles in the neurocognitive impairment many cancer survivors experience.
View details for DOI 10.1016/j.bbr.2011.05.012
View details for Web of Science ID 000301404000010
View details for PubMedID 21621557
Complete Ocular Paresis in a Child with Posterior Fossa Syndrome
2012; 48 (1): 51-54
Posterior fossa syndrome (PFS), also known as cerebellar affective syndrome, is characterized by emotional lability and decreased speech production following injury or surgery to the cerebellum. Rarely, oculomotor dysfunction has been described in association with PFS. Here, we report a case of complete ocular paresis associated with PFS in an 11-year-old male following medulloblastoma resection.
View details for DOI 10.1159/000339382
View details for Web of Science ID 000309885700010
View details for PubMedID 22906880
- Hedgehogs, Flies, Wnts and MYCs: The Time Has Come for Many Things in Medulloblastoma JOURNAL OF CLINICAL ONCOLOGY 2011; 29 (11): 1395-1398
Neurological complications following treatment of children with brain tumors.
Journal of pediatric rehabilitation medicine
2011; 4 (1): 31-36
Brain tumors and their treatments in children result in a range of neurological complications that can affect daily function and rehabilitation potential, including neurocognitive sequelae, ototoxicity, seizure disorders, stroke, and peripheral neuropathy. Deficits in cognitive function, particularly learning and memory, attention and speed of information processing, can be debilitating. With new insights to the cellular and molecular etiology of these deficits, new therapies for cognitive decline after therapy are emerging. Management strategies for other neurological complications are also emerging.
View details for DOI 10.3233/PRM-2011-0150
View details for PubMedID 21757808
Clinical Patterns and Biological Correlates of Cognitive Dysfunction Associated with Cancer Therapy
2008; 13 (12): 1285-1295
Standard oncological therapies, such as chemotherapy and cranial radiotherapy, frequently result in a spectrum of neurocognitive deficits that includes impaired learning, memory, attention, and speed of information processing. In addition to classical mechanisms of neurotoxicity associated with chemo- and radiotherapy, such as radiation necrosis and leukoencephalopathy, damage to dynamic progenitor cell populations in the brain is emerging as an important etiologic factor. Radiation- and chemotherapy-induced damage to progenitor populations responsible for maintenance of white matter integrity and adult hippocampal neurogenesis is now believed to play a major role in the neurocognitive impairment many cancer survivors experience.
View details for DOI 10.1634/theoncologist.2008-0130
View details for Web of Science ID 000261996600008
View details for PubMedID 19019972
CRANIAL RADIATION THERAPY AND DAMAGE TO HIPPOCAMPAL NEUROGENESIS
DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS
2008; 14 (3): 238-242
Cranial radiation therapy is associated with a progressive decline in cognitive function, prominently memory function. Impairment of hippocampal neurogenesis is thought to be an important mechanism underlying this cognitive decline. Recent work has elucidated the mechanisms of radiation-induced failure of neurogenesis. Potential therapeutic interventions are emerging.
View details for DOI 10.1002/ddrr.26
View details for Web of Science ID 000262726500008
View details for PubMedID 18924155
Excitation-neurogenesis coupling in adult neural stem/progenitor cells
2004; 42 (4): 535-552
A wide variety of in vivo manipulations influence neurogenesis in the adult hippocampus. It is not known, however, if adult neural stem/progenitor cells (NPCs) can intrinsically sense excitatory neural activity and thereby implement a direct coupling between excitation and neurogenesis. Moreover, the theoretical significance of activity-dependent neurogenesis in hippocampal-type memory processing networks has not been explored. Here we demonstrate that excitatory stimuli act directly on adult hippocampal NPCs to favor neuron production. The excitation is sensed via Ca(v)1.2/1.3 (L-type) Ca(2+) channels and NMDA receptors on the proliferating precursors. Excitation through this pathway acts to inhibit expression of the glial fate genes Hes1 and Id2 and increase expression of NeuroD, a positive regulator of neuronal differentiation. These activity-sensing properties of the adult NPCs, when applied as an "excitation-neurogenesis coupling rule" within a Hebbian neural network, predict significant advantages for both the temporary storage and the clearance of memories.
View details for Web of Science ID 000221708300006
View details for PubMedID 15157417
Extreme sensitivity of adult neurogenesis to low doses of X-irradiation
2003; 63 (14): 4021-4027
Therapeutic irradiation of the brain is associated with a number of adverse effects, including cognitive impairment. Although the pathogenesis of radiation-induced cognitive injury is unknown, it may involve loss of neural precursor cells from the subgranular zone (SGZ) of the hippocampal dentate gyrus and alterations in new cell production (neurogenesis). Young adult male C57BL mice received whole brain irradiation, and 6-48 h later, hippocampal tissue was assessed using immunohistochemistry for detection of apoptosis and numbers of proliferating cells and immature neurons. Apoptosis peaked 12 h after irradiation, and its extent was dose dependent. Forty-eight h after irradiation, proliferating SGZ cells were reduced by 93-96%; immature neurons were decreased from 40 to 60% in a dose-dependent fashion. To determine whether acute cell sensitivity translated into long-term changes, we quantified neurogenesis 2 months after irradiation with 0, 2, 5, or 10 Gy. Multiple injections of BrdUrd were given to label proliferating cells, and 3 weeks later, confocal microscopy was used to determine the percentage of BrdUrd-labeled cells that showed mature cell phenotypes. The production of new neurons was significantly reduced by X-rays; that change was dose dependent. In contrast, there were no apparent effects on the production of new astrocytes or oligodendrocytes. Measures of activated microglia indicated that changes in neurogenesis were associated with a significant inflammatory response. Given the known effects of radiation on cognitive function and the relationship between hippocampal neurogenesis and associated memory formation, our data suggest that precursor cell radiation response and altered neurogenesis may play a contributory if not causative role in radiation-induced cognitive impairment.
View details for Web of Science ID 000184379800031
View details for PubMedID 12874001
Radiation injury and neurogenesis
CURRENT OPINION IN NEUROLOGY
2003; 16 (2): 129-134
For many cancers, survival depends on aggressive combined therapies, but treatment comes at a price. Children and adults who receive radiotherapy involving the brain frequently experience a progressive cognitive decline. The overt pathologies of radiation injury such as white matter necrosis or vasculopathy are the obvious "smoking guns" of dysfunction. However, many patients exhibit severe learning and memory deficits with no overt pathologic changes. This is especially true when the radiation field involves the temporal lobes. The cause of this debilitating dysfunction is currently unknown and untreatable.Within the temporal lobe, the hippocampal formation plays a central role in short-term learning and memory--the functions most notably affected by radiation. Recent work has also shown that hippocampus-dependent learning and memory are strongly influenced by the activity of neural stem cells and their proliferative progeny. The hippocampal granule cell layer undergoes continuous renewal and restructuring by the addition of new neurons. Radiation at much lower doses than that needed to injure the more resistant post-mitotic neurons and glia of the brain has been found to affect these highly proliferative progenitors severely. The stem/progenitor cell is so sensitive to radiation that a single low dose to the cranium of a mature rat is sufficient to ablate hippocampal neurogenesis.Progressive learning and memory deficits following irradiation may be caused by the accumulating hippocampal dysfunction that results from a long-term absence of normal stem/progenitor activity. Here, the authors describe the nature of this stem cell dysfunction and contemplate how restoration of stem/progenitor cell activity might be approached in experimental models and, eventually, the clinic.
View details for DOI 10.1097/01.wco.0000063772.8181.b7
View details for Web of Science ID 000182542200002
View details for PubMedID 12644738