Pediatric Astrocytomas Research Articles

Pathology, Molecular Genetics, and Epigenetics of Diffuse Intrinsic Pontine Glioma.

Diffuse intrinsic pontine glioma (DIPG) is a devastating pediatric brain cancer with no effective therapy. Histological similarity of DIPG to supratentorial high-grade astrocytomas of adults has led to assumptions that these entities possess similar underlying molecular properties and therefore similar therapeutic responses to standard therapies. The failure of all clinical trials in the last 30 years to improve DIPG patient outcome has suggested otherwise. Recent studies employing next-generation sequencing and microarray technologies have provided a breadth of evidence highlighting the unique molecular genetics and epigenetics of this cancer, distinguishing it from both adult and pediatric cerebral high-grade astrocytomas. This review describes the most common molecular genetic and epigenetic signatures of DIPG in the context of molecular subgroups and histopathological diagnosis, including this tumor entity’s unique mutational landscape, copy number alterations, and structural variants, as well as epigenetic changes on the global DNA and histone levels. The increased knowledge of DIPG biology and histopathology has opened doors to new diagnostic and therapeutic avenues.

Longitudinal evaluation of health status and chronic conditions in aging pediatric astrocytoma survivors: A Childhood Cancer Survivor Study (CCSS) report.

10067 Background: Astrocytoma is a common pediatric central nervous system tumor. However, little is known about the health status and chronic conditions and their association with social outcomes in aging survivors. Methods: We evaluated 1,073 5-year astrocytoma survivors (median age: 28 years, range 9-56; median time from diagnosis: 21 years, range 7-38) and 4,023 siblings enrolled in the CCSS at up to 3 time points. We estimated the prevalence of poor health status in 6 domains (general health, functional impairment, activity limitation, mental health, cancer-related pain, cancer-related anxiety); severe, disabling, or life-threatening chronic conditions; and social outcomes (marriage, education, employment, income) in those ≥ 25 years of age. We compared outcomes between survivors and siblings as a function of attained age using generalized linear models with robust variances adjusted for race, sex, and body mass index. Results: Compared with siblings, astrocytoma survivors were more likely to report ...

LG-04 * NOTCH SIGNALING ACTIVATION IN PEDIATRIC LOW-GRADE ASTROCYTOMA

Pilocytic astrocytoma (PA) is the most common primary brain tumor in children, and various signaling pathways have been implicated in its biology. The Notch signaling pathway has been found to play a role in development, stem cell biology and the pathogenesis of several cancers but its role in PA has not been investigated. We studied alterations in Notch signaling components in clinical PA tumor tissue, to identify much needed therapeutic targets. In this study, we found Notch pathway members to be overexpressed at the mRNA (NOTCH1, NOTCH2, HEY1, HEY2) and protein (HES1) level in PA at various anatomical sites compared to non-neoplastic brain. The changes were not associated with specific BRAF alterations. Inhibiting the Notch pathway in pediatric low grade astrocytoma-derived cell lines (Res 186 and Res 259) using either RNA interference or a gamma secretase inhibitor resulted in a significant, but variable reduction in cell growth and migration. This study suggests a role for Notch signaling in the context of pediatric low grade astrocytoma tumorigenesis, and that Notch signaling is a viable pathway to target therapeutically.

HG-07 * DETECTION OF K27M MUTANT PEDIATRIC GLIOBLASTOMAS BY IMMUNOHISTOCHEMISTRY

Pediatric glioblastomas (GBM) are lethal and fatal tumors and ∼30% of GBM and ∼80% of diffuse intrinsic pontine gliomas show K27M mutations in the H3F3A gene, a variant encoding histone H3.3. These mutations lead to global reduction in H3K27me3. Our goal was to develop biomarkers for the histopathologic detection of these tumors. Therefore, we evaluated the utility of measuring H3K27me3 global reduction as a biomarker and tested an antibody directed specifically against the K27M mutation in 290 samples of 203 pediatric (including 38 pediatric high-grade astrocytomas), 38 adult brain tumors of various subtypes and grades and 49 non-neoplastic reactive brain tissues. Detection of K27M by immunohistochemistry showed 100% sensitivity and specificity and was superior to reduction in H3K27me3 as a biomarker. Moreover, cases that stained positive for K27M showed a significantly poor prognosis compared to corresponding negative tumors. These results suggest that immunohistochemical detection of K27M is a sensitive and specific surrogate for K27M mutations and a prognostic marker.

BT-07 * MEASURING TUMOR METABOLISM IN DIFFUSE INTRINSIC PONTINE GIOMAS (DIPG) USING HYPERPOLARIZED CARBON-13 MR SPECTROSCOPIC IMAGING

Diffuse intrinsic pontine gliomas (DIPGs) continue to have a very poor prognosis with a median survival rate of 9 months. The methods for assessing treatment response and tumor progression are based on radiographic response but conventional MRI is not sufficient for predicting clinical outcome. A recent first-in-human study using hyperpolarized 13C MR metabolic imaging showed the safety and feasibility of this technology for evaluating hyperpolarized pyruvate metabolism in humans. The purpose of this study was to demonstrate the feasibility of using hyperpolarized 13C metabolic imaging with [1-13C]pyruvate as a non-invasive imaging tool to evaluate in vivo metabolism in orthotopic brainstem xenografts injected with human DIPG cells. Primary human derived DIPG cells were implanted into the brainstem of athymic rats (n = 4). 3D magnetic resonance spectroscopic imaging (MRSI) data were acquired using a clinical 3T scanner with a custom-designed 1H/13C coil after the injection of hyperpolarized [1-13C]pyruvate solution. The hyperpolarized 13C MRSI data exhibited an abnormal 13C metabolism in the T2 lesions. The mean normalized lactate, normalized pyruvate and the ratio of lactate to pyruvate in the T2 hyperintense voxels were 3.1 ± 1.7, 1.5 ± 0.4 and 0.47 ± 0.2 (mean ± standard deviation), respectively, and significantly higher than the corresponding values from the contra-lateral hemisphere. The lactate signal in theses areas were highly elevated compared to the lactate signal in the normal appearing brain tissue from the supratentorial region. The metabolite quantification revealed the differentiation of lactate signal between tumor core, tissue in the periphery of tumor and tissue in the contra-lateral hemisphere. The corresponding H&E stained slides showed viable tumor that recapitulated the histopathology of a subset of high-grade pediatric astrocytomas. The results suggest that this technique may provide a unique non-invasive imaging tool that will be beneficial in the management of patients with DIPG.

Growth-factor-driven rescue to receptor tyrosine kinase (RTK) inhibitors through Akt and Erk phosphorylation in pediatric low grade astrocytoma and ependymoma.

Up to now, several clinical studies have been started investigating the relevance of receptor tyrosine kinase (RTK) inhibitors upon progression free survival in various pediatric brain tumors. However, single targeted kinase inhibition failed, possibly due to tumor resistance mechanisms. The present study will extend our previous observations that vascular endothelial growth factor receptor (VEGFR)-2, platelet derived growth factor receptor (PDGFR)β, Src, the epidermal growth factor receptor (ErbB) family, and hepatocyte growth factor receptor (HGFR/cMet) are potentially drugable targets in pediatric low grade astrocytoma and ependymoma with investigations concerning growth-factor-driven rescue. This was investigated in pediatric low grade astrocytoma and ependymoma cell lines treated with receptor tyrosine kinase (RTK) inhibitors e.g. sorafenib, dasatinib, canertinib and crizotinib. Flow cytometry analyses showed high percentage of cells expressing VEGFR-1, fibroblast growth factor receptor (FGFR)-1, ErbB1/EGFR, HGFR and recepteur d’origine nantais (RON) (respectively 52-77%, 34-51%, 63-90%, 83-98%, 65-95%). Their respective inhibitors induced decrease of cell viability, measured with WST-1 cell viability assays. At least this was partially due to increased apoptotic levels measured by Annexin V/Propidium Iodide apoptosis assays. EGF, HGF and FGF, which are normally expressed in brain (tumor) tissue, showed to be effective rescue inducing growth factors resulting in increased cell survival especially during treatment with dasatinib (complete rescue) or sorafenib (partial rescue). Growth-factor-driven rescue was less prominent when canertinib or crizotinib were used. Rescue was underscored by significantly activating downstream Akt and/or Erk phosphorylation and increased tumor cell migration. Combination treatment showed to be able to overcome the growth-factor-driven rescue. In conclusion, our study highlights the extensive importance of environmentally present growth factors in developing tumor escape towards RTK inhibitors in pediatric low grade astrocytoma and ependymoma. It is of great interest to anticipate upon these results for the design of new therapeutic trials with RTK inhibitors in these pediatric brain tumors.

Notch signaling activation in pediatric low-grade astrocytoma.

Pilocytic astrocytoma (PA) is the most common primary brain tumor in children; various signaling pathways have been implicated in its biology. The Notch signaling pathway has been found to play a role in the development, stem cell biology, and pathogenesis of several cancers, but its role in PA has not been investigated. We studied alterations in Notch signaling components in tumor tissue from 18 patients with PA and 4 with other low-grade astrocytomas to identify much needed therapeutic targets. We found that Notch pathway members were overexpressed at the mRNA (NOTCH1, NOTCH2, HEY1, HEY2) and protein (HES1) levels in PAs at various anatomic sites compared with non-neoplastic brain samples. These changes were not associated with specific BRAF alterations. Inhibiting the Notch pathway in the pediatric low-grade astrocytoma cell lines Res186 and Res259 using either RNA interference or a γ-secretase inhibitor resulted in variable, but significant, reduction in cell growth and migration. This study suggests a potential role for Notch signaling in pediatric low-grade astrocytoma tumorigenesis and that Notch signaling may be a viable pathway therapeutic target.

Histone H3.3 and cancer: A potential reader connection

The building block of chromatin is nucleosome, which consists of 146 base pairs of DNA wrapped around a histone octamer composed of two copies of histone H2A, H2B, H3, and H4. Significantly, the somatic missense mutations of the histone H3 variant, H3.3, are associated with childhood and young-adult tumors, such as pediatric high-grade astrocytomas, as well as chondroblastoma and giant-cell tumors of the bone. The mechanisms by which these histone mutations cause cancer are by and large unclear. Interestingly, two recent studies identified BS69/ZMYND11, which was proposed to be a candidate tumor suppressor, as a specific reader for a modified form of H3.3 (H3.3K36me3). Importantly, some H3.3 cancer mutations are predicted to abrogate the H3.3K36me3/BS69 interaction, suggesting that this interaction may play an important role in tumor suppression. These new findings also raise the question of whether H3.3 cancer mutations may lead to the disruption and/or gain of interactions of additional cellular factors that contribute to tumorigenesis.

EG-01 * EPIGENETIC INACTIVATION OF ARGININE BIOSYNTHESIS PATHWAY IN PAEDIATRIC HIGH GRADE GLIOMA

Aberrant cellular metabolism contributes significantly to the growth and proliferation of several tumour types. Identification of genes that control critical metabolic pathways is a major factor in the development of novel therapies that target metabolic defects in tumour cells. Our aim is to identify such genes in paediatric high grade glioma that are altered due to promoter hyper-methylation of cytosine residues in CpG dinucleotides. Genome wide DNA methylation profiling using Illumina infinium methylation 450K bead chip array was performed on 18 well-characterised short term cultures derived from paediatric high grade astrocytoma including 3 from diffuse intrinsic pontine glioma. Data analyses were based on beta scores of probes for each gene as measures of intensities of methylation. Genes were selected with beta scores of tumour > =0.70 and that of normal human astrocytes < =0.30. We identified that two vital genes involved in the regulation of arginine biosynthetic pathway, argininosuccinate synthetase 1(ASS1) and argininosuccinate lyase (ASL) were methylated in 9/18 (50%) cases. Hyper methylation was confirmed by methylation-specific PCR and up-regulation of gene expression following treatment with 2 µM 5-aza-2'-deoxyctidine. Down-regulation of ASS1 in hyper methylated samples was confirmed by Western blot analysis. Our findings report epigenetic deregulation of ASS1 and ASL in a subset of paediatric high grade glioma. The enzymes encoded by these genes are essential elements of urea cycle that function together in the de novo synthesis of arginine from citrulline. Tumour cells with deficient ASS1/ASL depend on external sources of arginine for survival and have been reported to be sensitive to autophagic cell death induced by arginine starvation. Therefore, further investigation may render the possibility of arginine-deprivation therapy in such sub type of paediatric high grade glioma. This therapeutic approach is of interest as tumour cells with abnormal expression of ASS1/ASL can be specifically targeted, while the normal cells can be spared.

Abstract B4: Growth-factor-driven rescue to receptor tyrosine kinase inhibitors in pediatric low-grade astrocytoma and ependymoma

Abstract Introduction: Brain tumors are still the leading cause of cancer morbidity and mortality among children, despite different therapeutic options including neurosurgery, chemotherapy and radiation. Up to now, several clinical studies have been started investigating the importance of receptor tyrosine kinase (RTK) inhibitors upon progression free survival in various pediatric brain tumors. However, it has been shown that single targeted kinase inhibition failed due to tumor resistance mechanisms. The present study will extend our previous observations that vascular endothelial growth receptor (VEGFR) 2, platelet derived growth factor receptor (PDGFR) β, Src, the epidermal growth factor receptor (ErbB) family, and hepatocyte growth factor receptor (HGFR/cMet) are potential drugable targets in pediatric low grade astrocytoma and ependymoma with investigations concerning growth-factor-driven rescue. Material and methods: Expression of various RTKs in pediatric low grade astrocytoma (Res-186, Res-259, UW-467) and ependymoma (Res-196) cell lines were determined using flow cytometry analyses. Growth-factor-driven rescue during RTK inhibition with agents including sorafenib, dasatinib, canertinib and crizotinib were analyzed on cell viability level measured with WST-1 cell viability assays and on phosphorylation level of the crucial downstream PI3K/Akt and MAPK/Erk survival signaling pathways using western blot analyses. Results: VEGFR-1, fibroblast growth factor receptor (FGFR) 1, ErbB-1, HGFR and recepteur d'origine nantais (RON) were highly expressed (respectively 52-77%, 34-51%, 63-90%, 83-98%, 65-95%) and their respective inhibitors showed induced decrease of tumor cell viability. EGF, HGF and FGF, which are normally environmentally expressed in brain (tumor) tissue, showed to be effective rescue inducing growth factors resulting in increased cell survival especially during treatment with dasatinib (complete rescue) or sorafenib (partial rescue) in both low grade astrocytoma and ependymoma. Growth-factor-driven rescue was less prominent when canertinib or crizotinib were used. Rescue was underscored by activating downstream Akt and/or Erk phosphorylation. Combination treatment showed to be able to overcome the growth-factor-driven resistance. Conclusions: In conclusion, our study highlights the extensive importance of environmentally present growth factors in developing resistance towards RTK inhibitors. It is of great interest to anticipate upon these results for the design of new therapeutic trials with RTK inhibitors in pediatric low grade astrocytoma and ependymoma. Citation Format: Mariska Sie, Wilfred F.A. den Dunnen, Harm Jan Lourens, Tiny G.J. Meeuwsen-de Boer, Frank J.G. Scherpen, Kim R. Kampen, Eelco W. Hoving, Eveline S.J.M. de Bont. Growth-factor-driven rescue to receptor tyrosine kinase inhibitors in pediatric low-grade astrocytoma and ependymoma. [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 B4.

Screening genes crucial for pediatric pilocytic astrocytoma using weighted gene coexpression network analysis combined with methylation data analysis.

To identify novel genes associated with pediatric pilocytic astrocytoma (PA) for better understanding the molecular mechanism underlying the pediatric PA pathogenesis. Gene expression profile data of GSE50161 and GSE44971 and the methylation data of GSE44684 were downloaded from Gene Expression Omnibus. The differentially expressed genes (DEGs) between PA and normal control samples were screened using the limma package in R, and then used to construct weighted gene coexpression network (WGCN) using the WGCN analysis (WGCNA) package in R. Significant modules of DEGs were selected using the clustering analysis. Function enrichment analysis of the DEGs in significant modules were performed using the WGCNA package and clusterprofiler package in R. Correlation between methylation sites of DEGs and PA was analyzed using the CpGassoc package in R. Totally, 3479 DEGs were screened in PA samples. Thereinto, 3424 DEGs were used to construct the WGCN. Several significant modules of DEGs were selected based on the WGCN, in which the turquoise module was positively related to PA, whereas blue module was negatively related to PA. DEGs (for example, DOCK2 (dedicator of cytokinesis 2), DOCK8 and FCGR2A (Fc fragment of IgG, low affinity IIa)) in blue module were mainly involved in Fc gamma R-mediated phagocytosis pathway and natural killer cell-mediated cytotoxicity pathway. Methylations of 14 DEGs among the top 30 genes in blue module were related to PA. Our data suggest that DOCK2, DOCK8 and FCGR2A may represent potential therapeutic targets in PA that merits further investigation.

Proteomic study of pilocytic astrocytoma pediatric brain tumor intracystic fluid.

Liquid chromatography in coupling with high-resolution ESI-LTQ-Orbitrap mass spectrometry was applied for a proteomic study of pediatric pilocytic astrocytoma brain tumor intracystic fluid by an integrated top-down/bottom-up platform. Both of the proteomic strategies resulted complementary and support each other in contributing to a wide characterization of the protein and peptide content of the tumor fluid. Top-down approach allowed to identify several proteins and peptides involved in different biological activities together with the characterization of interesting proteoforms such as fibrinopeptide A and its truncated form, fibrinopeptide B, complement C3f fragments, β-thymosin peptides, ubiquitin, several apolipoproteins belonging to A and C families, apolipoprotein J and D, and cystatin C. Of particular interest resulted the identification of a N-terminal truncated cystatin C proteoform, likely involved in immune response mechanism modulations and the identification of oxidized and glycosylated apolipoproteins including disulfide bridge dimeric forms. The bottom-up approach confirmed some of the experimental data findings together with adding the characterization of high-molecular-mass proteins in the samples. These data could contribute to elucidate the molecular mechanisms involved in onset and progression of the disease and cyst development.

A sensitive and specific histopathologic prognostic marker for H3F3A K27M mutant pediatric glioblastomas.

Pediatric glioblastomas (GBM) are highly aggressive and lethal tumors. Recent sequencing studies have shown that ~30 % of pediatric GBM and ~80 % of diffuse intrinsic pontine gliomas show K27M mutations in the H3F3A gene, a variant encoding histone H3.3. H3F3A K27M mutations lead to global reduction in H3K27me3. Our goal was to develop biomarkers for the histopathologic detection of these tumors. Therefore, we evaluated the utility of measuring H3K27me3 global reduction as a histopathologic and prognostic biomarker and tested an antibody directed specifically against the H3.3 K27M mutation in 290 samples. The study cohort included 203 pediatric (including 38 pediatric high-grade astrocytomas) and 38 adult brain tumors of various subtypes and grades and 49 non-neoplastic reactive brain tissues. Detection of H3.3 K27M by immunohistochemistry showed 100 % sensitivity and specificity and was superior to global reduction in H3K27me3 as a biomarker in diagnosing H3F3A K27M mutations. Moreover, cases that stained positive for H3.3 K27M showed a significantly poor prognosis compared to corresponding negative tumors. These results suggest that immunohistochemical detection of H3.3 K27M is a sensitive and specific surrogate for the H3F3A K27M mutation and defines a prognostically poor subset of pediatric GBM.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-014-1338-3) contains supplementary material, which is available to authorized users.

Specific detection of methionine 27 mutation in histone 3 variants (H3K27M) in fixed tissue from high-grade astrocytomas.

Studies in pediatric high-grade astrocytomas (HGA) by our group and others have uncovered recurrent somatic mutations affecting highly conserved residues in histone 3 (H3) variants. One of these mutations leads to analogous p.Lys27Met (K27M) mutations in both H3.3 and H3.1 variants, is associated with rapid fatal outcome, and occurs specifically in HGA of the midline in children and young adults. This includes diffuse intrinsic pontine gliomas (80 %) and thalamic or spinal HGA (>90 %), which are surgically challenging locations with often limited tumor material available and critical need for specific histopathological markers. Here, we analyzed formalin-fixed paraffin-embedded tissues from 143 pediatric HGA and 297 other primary brain tumors or normal brain. Immunohistochemical staining for H3K27M was compared to tumor genotype, and also compared to H3 tri-methylated lysine 27 (H3K27me3) staining, previously shown to be drastically decreased in samples carrying this mutation. There was a 100 % concordance between genotype and immunohistochemical analysis of H3K27M in tumor samples. Mutant H3K27M was expressed in the majority of tumor cells, indicating limited intra-tumor heterogeneity for this specific mutation within the limits of our dataset. Both H3.1 and H3.3K27M mutants were recognized by this antibody while non-neoplastic elements, such as endothelial and vascular smooth muscle cells or lymphocytes, did not stain. H3K27me3 immunoreactivity was largely mutually exclusive with H3K27M positivity. These results demonstrate that mutant H3K27M can be specifically identified with high specificity and sensitivity using an H3K27M antibody and immunohistochemistry. Use of this antibody in the clinical setting will prove very useful for diagnosis, especially in the context of small biopsies in challenging midline tumors and will help orient care in the context of the extremely poor prognosis associated with this mutation.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-014-1337-4) contains supplementary material, which is available to authorized users.

P05.02 * KIAA1549:BRAF FUSION GENE IN PEDIATRIC BRAIN TUMORS OF VARIOUS HISTOGENESIS

INTRODUCTION: Pediatric GBMs (pGBM) are histologically indistinguishable from adult GBM (aGBM) however they are molecularly distinct. Few molecular data exists on the mechanism underlying development and progression of pGBM, whereas a number of gene expression profiling analyses performed in aGBM helped to identify molecular events leading to oncogenesis and provided more accurate means for classification of subtypes, outcomes and even response to treatments. The KIAA1549:BRAF fusion (K-B) gene has been considered a driver of genetic events and a useful diagnostic marker in adult pilocytic astrocytoma (PA). The K-B fusion, on the other hand, is an unusual finding in pediatric diffuse astrocytomas and oligoastocytoma and not reported in pHGG On the other hand, it has been reported a low frequency of B_F fusion gene in adult diffuse gliomas in association with IDH1 mutations. METHODS: To further elucidate the possible occurrence of the K-B fusion gene in non-PA tumors, we investigated its presence in a series of 69 pediatric brain neoplasms of different histogenesis and grade (34 non PA and 35 PA). Fusion has been investigated through the analysis of messenger RNA by reverse-transcription polymerase chain reaction (RT-PCR) followed by sequencing. Selected cases were screened for mutational analysis for IDH1, BRAFv600 and H3F3A. Positive cases have undergone to confirmation by the interphase Fluorescence in situ Hybridization (FISH) analysis and quantitative PCR (Taqman). RESULTS: We detected the KIAA1549:BRAF fusion (K-B) gene in 5 out of 34 (14.7%) non-PA primary tumors, i.e. 1 glioblastoma, 1 anaplastic astrocytoma, 1 anaplastic PXA, 1 ependymoma and 1 AT/RT. The fusion gene was also found in 21 out of 35 PAs (63.6%) and in 1/3 (33%) WHO grade I gangliogliomas. Quantitative PCR and FISH analysis confirmed the presence of the K-B fusion gene. The frequency of fusion harboring nuclei in non-PA neoplasms was lower than in PAs. Screening for IDH1, BRAFv600, and H3F3A mutations disclosed one case with the IDH1 and one with the K27M-H3.3 mutation, both unassociated with the K-B gene. CONCLUSION: Our study indicates that: 1) the K-B fusion gene can occasionally be detected in non-PA tumors of various histogenesis; 2) its occurrence in these neoplasms is probably due rather to a random alteration related to genomic instability than to a driving molecular event, as in PAs; and 3) the K-B fusion gene's role as a diagnostic marker outside the histological spectrum of pediatric low-grade gliomas should be carefully considered.

Anorexia: an early sign of fourth ventricle astrocytoma in children.

Paediatric low-grade astrocytomas of the fourth ventricle are rare tumours, generally revealed by hydrocephalus. However, some patients present with a history of severe anorexia. It might be a harbinger, which if recognized, could lead to earlier diagnosis. We decided to examine our database in order to evaluate the incidence and signification of anorexia in this context. Retrospective monocentric study of cases of low-grade astrocytomas of the fourth ventricle operated between 1991 and 2012 in our paediatric neurosurgery department. We particularly observed the clinical presentation and long-term clinical, oncological and radiological evolution. Non-parametrical tests were used (Mann-Whitney, Fisher). We reviewed 34 cases, 31 pilocytic astrocytomas and 3 diffuse astrocytomas, 16 boys and 18 girls, (M/F ratio 0.89). Mean age at diagnosis was 8 years old. Seven presented with notable anorexia, the average BMI in this group was ≤2 standard deviation (SD); with clinical signs evolving for 11.5 months. Twenty-seven children had no anorexia; average BMI in this group was +1 SD, with clinical evolution for 6 months on an average of p < 0.05. We found no significant difference regarding hydrocephalus or tumour location. In all children with anorexia, body mass index improved markedly in the postoperative follow-up, which lasted, on average, for 6 years. Anorexia with stunted body weight curve is a non-exceptional presentation in children with low-grade astrocytomas of the fourth ventricle. Unexplained or atypical anorexia with negative etiologic assessment should prompt cerebral imaging. Clinical improvement after surgical resection, could suggest a possible interaction between tumour tissue and appetite-suppressing peptide secretion.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Reductions in the expression of miR-124-3p, miR-128-1, and miR-221-3p in pediatric astrocytomas are related to high-grade supratentorial, and recurrent tumors in Mexican children

Astrocytomas are the most frequent type of tumor of the central nervous system in children. Hence, it is important to describe markers that may improve our understanding of their behavior. Mature microRNAs (miRNAs) may be such biological markers. They are small molecules of RNA that regulate gene expression post-transcriptionally. Due to their importance in cancer, the objective of the present study was to determine the profile of expression of precursor and mature forms of miR-124-3p, miR-128-1, and miR-221-3p using RT-qPCR in pediatric samples. A total of 57 astrocytomas embedded in paraffin were selected. As controls, the study included 13 samples of normal brain tissue. Three of eight miRNAs were selected after a preliminary screening. All the miRNAs showed higher levels of expression in normal brain tissue. The expression of miR-124-3p and miR-128-1 decreased in astrocytomas than in normal brain tissue in all grades (p < 0.05 in both cases), and this reduction was most evident in GIV (407- and 1,469-fold, respectively); however, the expression of the precursor forms pre-miR-128-1 and pre-miR-221 was higher in GIV (3.5-fold) than in GI. The levels of miR-128-1 were higher in infratentorial tumors than in supratentorial cases (p = 0.006). Finally, the expression of miR-221-3p was higher in non-recurrent tumors and live patients (p = 0.0185 and p = 0.0004, respectively). The low expression of these miRNAs may constitute a potential marker of astrocytomas that correlates with localization, possibly due to alterations in the maturation processes of these miRNAs that produced low mature forms in patients with recurrent pediatric astrocytomas.

Recurrent somatic mutations in ACVR1 in pediatric midline high-grade astrocytoma

Pediatric midline high-grade astrocytomas (mHGAs) are incurable with few treatment targets identified. Most tumors harbor mutations encoding p.Lys27Met in histone H3 variants. In 40 treatment-naive mHGAs, 39 analyzed by whole-exome sequencing, we find additional somatic mutations specific to tumor location. Gain-of-function mutations in ACVR1 occur in tumors of the pons in conjunction with histone H3.1 p.Lys27Met substitution, whereas FGFR1 mutations or fusions occur in thalamic tumors associated with histone H3.3 p.Lys27Met substitution. Hyperactivation of the bone morphogenetic protein (BMP)-ACVR1 developmental pathway in mHGAs harboring ACVR1 mutations led to increased levels of phosphorylated SMAD1, SMAD5 and SMAD8 and upregulation of BMP downstream early-response genes in tumor cells. Global DNA methylation profiles were significantly associated with the p.Lys27Met alteration, regardless of the mutant histone H3 variant and irrespective of tumor location, supporting the role of this substitution in driving the epigenetic phenotype. This work considerably expands the number of potential treatment targets and further justifies pretreatment biopsy in pediatric mHGA as a means to orient therapeutic efforts in this disease.

Analysis of KIAA1549–BRAF fusion gene expression and IDH1/IDH2 mutations in low grade pediatric astrocytomas

Low-grade astrocytomas comprise about 30% of the central nervous system tumors in children. Several investigations have searched a correlation between the BRAF gene fusions alterations and mutations at IDH1 and IDH2 genes in low grade pediatric astrocytomas. This study identified the expression of KIAA1549-BRAF fusion gene and BRAF V600E mutation, mutations at exon 4 of the IDH1 and IDH2 genes in samples of pilocytic astrocytomas (PA) and grade-II astrocytomas (A-II) pediatric patients. The correlation between these alterations and the clinical profile of the patients was also evaluated. Eighty-two samples of low-grade astrocytomas (65 PA and 17 A-II) were analyzed by PCR and sequencing for each of the targets identified. We identified the KIAA1549-BRAF fusion transcript in 45% of the samples. BRAF V600E and BRAFins598T mutations were detected in 7 and 1% of the samples, respectively. Mutations in the R132/R172 residues of the IDH1/IDH2 genes were detected in only two samples, and the G105G polymorphism (rs11554137:C>T) was identified in ten patients. Additionally, we observed two mutations out of the usual hotspots at IDH1 and IDH2 genes. We observed a smaller frequency of mutations in IDHs genes than previously described, but since the prior studies were composed of adult or mixed (adults and children) samples, we believe that our results represent a relevant contribution to the growing knowledge in low grade childhood astrocytomas.