MGMT gene promoter methylation in pediatric glioblastomas

Childhood Cancer: Occurrence, Treatment and Risk of Second Primary Malignancies

Cancer represents the leading cause of disease-related death and treatment-associated morbidity in children with an increasing trend in recent decades worldwide. Nevertheless, the 5-year survival of childhood cancer patients has been raised impressively to more than 80% during the past decades, primarily attributed to improved diagnostic technologies and multiagent cytotoxic regimens. This strong benefit of more efficient tumor control and prolonged survival is compromised by an increased risk of adverse and fatal late sequelae. Long-term survivors of pediatric tumors are at the utmost risk for non-carcinogenic late effects such as cardiomyopathies, neurotoxicity, or pneumopathies, as well as the development of secondary primary malignancies as the most detrimental consequence of genotoxic chemo- and radiotherapy. Promising approaches to reducing the risk of adverse late effects in childhood cancer survivors include high precision irradiation techniques like proton radiotherapy or non-genotoxic targeted therapies and immune-based treatments. However, to date, these therapies are rarely used to treat pediatric cancer patients and survival rates, as well as incidences of late effects, have changed little over the past two decades in this population. Here we provide an overview of the epidemiology and etiology of childhood cancers, current developments for their treatment, and therapy-related adverse late health consequences with a special focus on second primary malignancies.

The molecular oncology of bilateral high-grade thalamic astrocytomas in children

BACKGROUND

Bilateral thalamic astrocytomas in children are exceedingly rare. These highly malignant tumors seldom respond to conventional treatment strategies and carry a grim prognosis for patients. However, recent advances in molecular oncology have had a positive impact on prognostication and treatment strategies of these tumors.

CASE-BASED REVIEW

We present a new case of WHO grade III bilateral thalamic astrocytoma in a child and review the pathophysiology, molecular oncogenesis, and relevant treatment strategies for this rare disease.

CONCLUSIONS

High-grade thalamic astrocytomas affecting both thalami pose a challenge to pediatric neurosurgeons, neuro-oncologists, and neuropathologists given the lack of effective treatment strategies. Understanding recent revelations in the field of molecular oncology can assist clinicians in adequately formulating a treatment plan in this patient population.

GSK3β‑mediated Ser156 phosphorylation modulates a BH3‑like domain in BCL2L12 during TMZ‑induced apoptosis and autophagy in glioma cells

BH3 domains, classified initially as BCL2 homology domains, participate in both apoptosis and autophagy. Beclin-1 contains a BH3 domain, which is required for binding to antiapoptotic BCL2 homologs and BCL2-mediated inhibition of autophagy. BCL2-like 12 (BCL2L12) also harbors a BH3-like domain, which is 12 residues long and contains a LXXXAE/D motif. In a yeast two-hybrid system performed in the present study, BCL2L12 shared similar binding partnerships to antiapoptotic BCL2 homologs, such as Beclin-1. In addition, this BH3-like domain was involved in antiapoptosis and drug-induced autophagy in glioma cell lines. Mutations in S156 and hydrophobic L213 to alanine counteracted the antiapoptotic properties of BCL2L12 and downregulated the activation of microtubule associated protein 1 light chain 3B (LC3B), autophagy-related (ATG)12-ATG5 conjugates and Beclin-1, compared with a BCL2L12 wild-type group. Molecular dynamics simulations revealed that phosphorylation at Ser156 of BCL2L12 (within α-6 and α-7 helices) influenced the BH3-like domain conformation (α-9 helix), indicating that glycogen synthase kinase (GSK) 3β-mediated Ser156 phosphorylation modulated a BH3-like domain in BCL2L12. Altogether, the present findings indicated that BCL2L12 may participate in anti-apoptosis and autophagy via a BH3-like domain and GSK3β-mediated phosphorylation at Ser156. Furthermore, blockade of temozolomide (TMZ)-induced autophagy by 3-methyladenine (3-MA) resulted in enhanced activation of apoptotic markers, as well as tumor suppresor protein p53 (p53) expression in U87MG cells. The present results suggested that p53 and O6-methylguanine DNA methyltransferase activation, and BCL2, BCL-extra large, Beclin-1 and BCL2L12 expression may be used as a detection panel to determine which patients can benefit from TMZ and ABT-737 combination treatment.

Extent of surgical resection and adjuvant temozolomide improves survival in pediatric GBM: a single center experience

BACKGROUND

Pediatric glioblastoma (pGBM) is an uncommon entity. The importance of concurrent and adjuvant temozolomide is not known in this subset of patients.

METHODS

We retrospectively analyzed our database between 2000 and 2015. All patients were treated with maximally safe surgical resection. This was followed by a uniform treatment schedule of post-operative radiation with concurrent daily temozolomide at 75 mg/m². Radiation dose was 60 Gy in 30 fractions planned by 3-dimensional conformal radiotherapy. Concurrent and adjuvant temozolomide was used in all patients treated after 2007. Four weeks later, adjuvant temozolomide was started at 150 mg/m², day 1 to 5 every 28 days and escalated to 200 mg/m² from the second cycle onwards if well tolerated. Log-rank test was used to compare survival distribution. The data was analyzed using SPSS (version 16).

RESULTS

Fifty-one patients were analyzed. Median age was 14 years (range: 5 to 21 years). Thirty-five males and 16 females were noted. Median symptom duration was 4 months. Twenty-eight patients underwent a gross total resection (GTR) while 17 underwent a subtotal resection; six patients underwent decompression. Thirty-three patients received concurrent chemotherapy while 27 received adjuvant chemotherapy. Median progression-free survival (PFS) was 15.1 months. One- and 3-year PFS was 54.4% and 3-year PFS was 24.6.7%. The median overall survival was 17.4 months. In univariate analysis survival was better for gross total resection (17.4 months vs. 11.5 months; p = 0.037), and significance maintained after multivariate analysis p = 0.026, HR 3.069, 95% CI 1.14-8.23. In univariate analysis, survival was better for patients receiving temozolomide but did not achieve significance. However, in multivariate analysis, use of temozolomide was associated with significantly improved survival p = 0.036, HR 3.315, 95% CI 1.07-10.19.

CONCLUSIONS

GTR improves survival significantly in pGBM. Adjuvant temozolomide may improve survival in pGBM.

Molecular mechanisms and therapeutic targets in pediatric brain tumors

Brain tumors are among the leading causes of cancer-related deaths in children. Although surgery, aggressive radiation, and chemotherapy have improved outcomes, many patients still die of their disease. Moreover, those who survive often suffer devastating long-term side effects from the therapies. A greater understanding of the molecular underpinnings of these diseases will drive the development of new therapeutic approaches. Advances in genomics and epigenomics have provided unprecedented insight into the molecular diversity of these diseases and, in several cases, have revealed key genes and signaling pathways that drive tumor growth. These not only serve as potential therapeutic targets but also have facilitated the creation of animal models that faithfully recapitulate the human disease for preclinical studies. In this Review, we discuss recent progress in understanding the molecular basis of the three most common malignant pediatric brain tumors-medulloblastoma, ependymoma, and high-grade glioma-and the implications for development of safer and more effective therapies.

Pediatric glioblastoma: a single institution experience

PURPOSE

The aim of this study was to evaluate characteristics of childhood glioblastoma multiforme, effectiveness of treatment modalities, and detect factors related to outcome.

METHODS

A detailed analysis was performed on a series of 15 patients treated between 2000 and 2013, based on their clinical, radiologic, pathologic, treatment, and follow-up data.

RESULTS

Median survival time of children with glioblastoma was 13.5 months. One- and 2-year overall survival probabilities were 66.7 and 20 %, respectively. There were no significant differences in survival based on patients' gender, age, disease presentation with or without epileptic seizures, signs/symptoms of increased intracranial pressure, or tumor location. The presence of neurological deficit initially, as well as prior to radiotherapy, which was quantified by neurologic function score (NFS), had an impact on overall survival. Children with NFS 0 lived longer compared to others (p = 0.001). Survival of children that underwent gross total resection was longer than that of children that underwent subtotal resection (p = 0.030). Mean survival time of children with gross total resection was 73.5 months, compared to 13 months in children with subtotal resection. There was no significant correlation between outcome and type of radiotherapy. In four patients with gigantocellular glioblastoma, we found no evidence of a better prognosis. Two long-term survivors were recorded. Both of them underwent gross total resection and were assigned a NFS 0.

CONCLUSIONS

Gross total resection is essential for longer overall survival among pediatric patients with glioblastoma and offers a possibility for long-term survival. Severity of neurologic symptoms quantified by NFS can be considered as a potential predictor of outcome.

Pediatric gliosarcoma treated with adjuvant radiotherapy and temozolomide

PURPOSE

Primary pediatric gliosarcoma (pPGS) is an extremely rare entity with only 25 cases reported in the English literature. The value of concurrent and adjuvant temozolomide is not known in this group of patient.

METHODS

Five patients of pPGS treated from 2006 to 2011 were included in this retrospective analysis. All patients underwent maximal safe surgical resection. Adjuvant therapy included conformal radiation 60 Gy in 30 fractions (2 Gy daily for 5 days in a week) with concurrent temozolomide 75 mg/m(2) daily followed by six cycles of maintenance temozolomide 150-200 mg/m(2) (day 1 to day 5) every 4 weeks. We combined the survival data of 25 patients (already published) and five of our patients and analyzed them in terms of progression free survival (PFS) and overall survival (OS) using Kaplan-Meier method.

RESULTS

Male to female ratio was 1:4 and median age was 12 years (range, 7-19 years). All but one patient underwent gross total resection and four patients completed adjuvant radiotherapy as well as concurrent and adjuvant temozolomide. At a median follow up of 22.6 months (range, 0 to 45.3 months), two patients were dead and two were alive without disease while one was lost to follow up. For the pooled data, estimated median PFS and OS of all 30 patients reported in literature were 12 and 43 months, respectively. Two years PFS and OS rate for all patients was 44.2 and 62.9%, respectively.

CONCLUSION

Adjuvant radiotherapy and temozolomide is well tolerated and show an encouraging survival in pPGS.

Therapeutic approach beyond conventional temozolomide for newly diagnosed glioblastoma: Review of the present evidence and future direction

Glioblastoma multiforme (GBM) is the most aggressive form of primary brain tumor. Maximal safe surgical resection followed by adjuvant partial brain radiation with concurrent and adjuvant temozolomide (TMZ) (oral alkylating agent) is the standard of care. Five years survival in TMZ treated patient reaches 9.8%. We aimed to summarize the changes in the management of GBM beyond conventional temozolomide based adjuvant treatment. We searched the PUBMED with the following key words: Glioblastoma, phase III trial, Phase II trial, adjuvant treatment in GBM. Clinical research has found a wide range of molecular aberrations in GBM and attempts are being made to further improve survival with the addition of different classes of drugs. Angiogenesis inhibitors, oncolytic vaccines, dose dense TMZ, and anti-epidermal growth factor receptor monoclonal antibody in phase III trials have failed to improve survival. Recent studies have also shown that the management strategies might be different and needs to be customized as per the age of patients such as pediatric and elderly patients. In addition, treatments should be personalized depending on the molecular aberrations. We reviewed all published phase III trials for newly diagnosed GBM as well as also looked into possible future directions in this review. Limited progress has happed beyond conventional TMZ in the adjuvant treatment of GBM. Newer insights are emerging about treatment intensification and introduction of newer molecular targeted drugs with more information about molecular aberrations.

Molecular Biology in Pediatric High-Grade Glioma: Impact on Prognosis and Treatment

High-grade gliomas are the main cause of death in children with brain tumours. Despite recent advances in cancer therapy, their prognosis remains poor and the treatment is still challenging. To date, surgery followed by radiotherapy and temozolomide is the standard therapy. However, increasing knowledge of glioma biology is starting to impact drug development towards targeted therapies. The identification of agents directed against molecular targets aims at going beyond the traditional therapeutic approach in order to develop a personalized therapy and improve the outcome of pediatric high-grade gliomas. In this paper, we critically review the literature regarding the genetic abnormalities implicated in the pathogenesis of pediatric malignant gliomas and the current development of molecularly targeted therapies. In particular, we analyse the impact of molecular biology on the prognosis and treatment of pediatric high-grade glioma, comparing it to that of adult gliomas.

Clinical outcome and molecular characterization of pediatric glioblastoma treated with postoperative radiotherapy with concurrent and adjuvant temozolomide: a single institutional study of 66 children

Background

Glioblastoma (GBM) in children is rare. Pediatric GBM have a distinct molecular profile as compared to adult GBM. There are relatively few studies of pediatric GBMs and no standard of care on adjuvant therapy. We aimed to evaluate the clinical outcome and molecular profile of pediatric GBM.

Methods and Materials

Between 2004 and 2013, 66 consecutive children with histologically proven GBM were identified from our database. The majority of the children underwent maximal safe resection followed by focal radiotherapy with concurrent and adjuvant temozolomide. Immunohistochemical staining was performed for p53, MIB-1 labeling index, MGMT overexpression, and EGFR amplification and isocitrate dehydrogenase (IDH1) R132H point mutation. Survival and impact of possible prognostic factors on outcomes were analyzed.

Result

Median survival was 15 months. The overall survival rate at 1 year was 62%, at 2 years was 30%, and at 3 years was 27%. Patients with thalamic tumors (P < .001), incompletely resected tumors (P < .00001), and tumors with MIB-1 labeling index >25% (P < .002) had poor overall survival rates. p53 was overexpressed in 74% of patients, MGMT promoter methylation was seen in 37% of patients, IDH1 mutation was seen in 4% of patients, and no patients had EGFR amplification. MGMT methylation and p53 overexpression did not impact survival.

Conclusions

Clinical outcome of pediatric GBM is similar to that reported for adult GBM. The frequency of p53 overexpression is higher than in adult GBM, while MGMT methylation, IDH1 mutations and EGFR amplification is lower than in adult GBM. MGMT methylation and p53 expression status do not have any prognostic significance.

Outcomes of pediatric glioblastoma treated with adjuvant chemoradiation with temozolomide and correlation with prognostic factors

Background:

Pediatric glioblastoma (pGBM) patients are underrepresented in major trials for this disease. We aimed to explore the outcome of pGBM patients treated with concurrent and adjuvant temozolomide (TMZ).

Materials and Methods:

23 patients of pGBM treated from 2004 to 2010 were included in this retrospective analysis. Adjuvant therapy included conformal radiation 60 gray at 2 gray/fraction daily over 6 weeks with concurrent TMZ 75 mg/m² followed by six cycles of adjuvant TMZ 150-200 mg/m² (day 1-5) every 4 weeks. Kaplan-Meier estimates of overall survival (OS) were determined. Univariate analysis with log-rank test was used to determine the impact of prognostic variables on survival.

Results:

Median age at presentation was 11.5 years (range: 7-19 years) and M:F ratio was 15:8. All patients underwent maximal safe surgical resection; 13 gross total resection and 10 sub-total resection. At a median follow-up of 18 months (range: 2.1-126 months), the estimated median OS was 41.9 months. The estimated median OS for patients receiving only concurrent TMZ was 8 months while that for patients receiving concurrent and adjuvant TMZ was 41.9 months (P = 0.081). Estimated median OS for patients who did not complete six cycles of adjuvant TMZ was 9.5 months versus not reached for those who completed at least six cycles (P = 0.0005). Other prognostic factors did not correlate with survival.

Conclusions:

Our study shows the benefit of TMZ for pGBM patients. Both concurrent and adjuvant TMZ seem to be important for superior OS in this group of patients.

Integrated analysis of pediatric glioblastoma reveals a subset of biologically favorable tumors with associated molecular prognostic markers

Pediatric glioblastoma (pedGBM) is amongst the most common malignant brain tumors of childhood and carries a dismal prognosis. In contrast to adult GBM, few molecular prognostic markers for the pediatric counterpart have been established. We, therefore, investigated the prognostic significance of genomic and epigenetic alterations through molecular analysis of 202 pedGBM (1-18 years) with comprehensive clinical annotation. Routinely prepared formalin-fixed paraffin-embedded tumor samples were assessed for genome-wide DNA methylation profiles, with known candidate genes screened for alterations via direct sequencing or FISH. Unexpectedly, a subset of histologically diagnosed GBM (n = 40, 20 %) displayed methylation profiles similar to those of either low-grade gliomas or pleomorphic xanthoastrocytomas (PXA). These tumors showed a markedly better prognosis, with molecularly PXA-like tumors frequently harboring BRAF V600E mutations and 9p21 (CDKN2A) homozygous deletion. The remaining 162 tumors with pedGBM molecular signatures comprised four subgroups: H3.3 G34-mutant (15 %), H3.3/H3.1 K27-mutant (43 %), IDH1-mutant (6 %), and H3/IDH wild-type (wt) GBM (36 %). These subgroups were associated with specific cytogenetic aberrations, MGMT methylation patterns and clinical outcomes. Analysis of follow-up data identified a set of biomarkers feasible for use in risk stratification: pedGBM with any oncogene amplification and/or K27M mutation (n = 124) represents a particularly unfavorable group, with 3-year overall survival (OS) of 5 %, whereas tumors without these markers (n = 38) define a more favorable group (3-year OS ~70 %).Combined with the lower grade-like lesions, almost 40 % of pedGBM cases had distinct molecular features associated with a more favorable outcome. This refined prognostication method for pedGBM using a molecular risk algorithm may allow for improved therapeutic choices and better planning of clinical trial stratification for this otherwise devastating disease.

Impact of tumor location and pathological discordance on survival of children with midline high-grade gliomas treated on Children's Cancer Group high-grade glioma study CCG-945

Children with high-grade glioma (HGG) have a poor prognosis compared to those with low-grade glioma (LGG). Adjuvant chemotherapy may be beneficial, but its optimal use remains undetermined. Histology and extent of resection are important prognostic factors. We tested the hypothesis that patients with midline HGG treated on Children's Cancer Group Study (CCG) CCG-945 have a worse prognosis compared to the entire group. Of 172 children eligible for analysis, 60 had midline tumors primarily localized to the thalamus, hypothalamus and basal ganglia. Time-to-progression and death were determined from the date of initial diagnosis, and survival curves were calculated. Univariate analyses were undertaken for extent of resection, chemotherapy regimen, anatomic location, histology, proliferation index, MGMT status and p53 over-expression. For the entire midline tumor group, 5-year PFS and OS were 18.3 ± 4.8 and 25 ± 5.4 %, respectively. Many patients only had a biopsy (43.3 %). The sub-groups with near/total resection and hypothalamic location appeared to have better PFS and OS. However, the effect of tumor histology on OS was significant for children with discordant diagnoses on central pathology review of LGG compared to HGG. Proliferative index (MIB-1 > 36 %), MGMT and p53 over-expression correlated with poor outcomes. Children treated on CCG-945 with midline HGG have a worse prognosis when compared to the entire group. The midline location may directly influence the extent of resection. Central pathology review and entry of patients on clinical trials continue to be priorities to improve outcomes for children with HGG.

Management of high-grade gliomas in the pediatric patient: Past, present, and future

High-grade gliomas (HGGs) constitute ∼15% of all primary brain tumors in children and adolescents. Routine histopathological diagnosis is based on tissue obtained from biopsy or, preferably, from the resected tumor itself. The majority of pediatric HGGs are clinically and biologically distinct from histologically similar adult malignant gliomas; these differences may explain the disparate responses to therapy and clinical outcomes when comparing children and adults with HGG. The recently proposed integrated genomic classification identifies 6 distinct biological subgroups of glioblastoma (GBM) throughout the age spectrum. Driver mutations in genes affecting histone H3.3 (K27M and G34R/V) coupled with mutations involving specific proteins (TP53, ATRX, DAXX, SETD2, ACVR1, FGFR1, NTRK) induce defects in chromatin remodeling and may play a central role in the genesis of many pediatric HGGs. Current clinical practice in pediatric HGGs includes surgical resection followed by radiation therapy (in children aged > 3 years) with concurrent and adjuvant chemotherapy with temozolomide. However, these multimodality treatment strategies have had a minimal impact on improving survival. Ongoing clinical trials are investigating new molecular targets, chemoradiation sensitization strategies, and immunotherapy. Future clinical trials of pediatric HGG will incorporate the distinction between GBM molecular subgroups and stratify patients using group-specific biomarkers.

Genome-wide methylation profiling identifies an essential role of reactive oxygen species in pediatric glioblastoma multiforme and validates a methylome specific for H3 histone family 3A with absence of G-CIMP/isocitrate dehydrogenase 1 mutation

BACKGROUND

Pediatric glioblastoma multiforme (GBM) is rare, and there is a single study, a seminal discovery showing association of histone H3.3 and isocitrate dehydrogenase (IDH)1 mutation with a DNA methylation signature. The present study aims to validate these findings in an independent cohort of pediatric GBM, compare it with adult GBM, and evaluate the involvement of important functionally altered pathways.

METHODS

Genome-wide methylation profiling of 21 pediatric GBM cases was done and compared with adult GBM data (GSE22867). We performed gene mutation analysis of IDH1 and H3 histone family 3A (H3F3A), status evaluation of glioma cytosine-phosphate-guanine island methylator phenotype (G-CIMP), and Gene Ontology analysis. Experimental evaluation of reactive oxygen species (ROS) association was also done.

RESULTS

Distinct differences were noted between methylomes of pediatric and adult GBM. Pediatric GBM was characterized by 94 hypermethylated and 1206 hypomethylated cytosine-phosphate-guanine (CpG) islands, with 3 distinct clusters, having a trend to prognostic correlation. Interestingly, none of the pediatric GBM cases showed G-CIMP/IDH1 mutation. Gene Ontology analysis identified ROS association in pediatric GBM, which was experimentally validated. H3F3A mutants (36.4%; all K27M) harbored distinct methylomes and showed enrichment of processes related to neuronal development, differentiation, and cell-fate commitment.

CONCLUSIONS

Our study confirms that pediatric GBM has a distinct methylome compared with that of adults. Presence of distinct clusters and an H3F3A mutation-specific methylome indicate existence of epigenetic subgroups within pediatric GBM. Absence of IDH1/G-CIMP status further indicates that findings in adult GBM cannot be simply extrapolated to pediatric GBM and that there is a strong need for identification of separate prognostic markers. A possible role of ROS in pediatric GBM pathogenesis is demonstrated for the first time and needs further evaluation.

Paediatric and adult glioblastoma: multiform (epi)genomic culprits emerge

We have extended our understanding of the molecular biology that underlies adult glioblastoma over many years. By contrast, high-grade gliomas in children and adolescents have remained a relatively under-investigated disease. The latest large-scale genomic and epigenomic profiling studies have yielded an unprecedented abundance of novel data and provided deeper insights into gliomagenesis across all age groups, which has highlighted key distinctions but also some commonalities. As we are on the verge of dissecting glioblastomas into meaningful biological subgroups, this Review summarizes the hallmark genetic alterations that are associated with distinct epigenetic features and patient characteristics in both paediatric and adult disease, and examines the complex interplay between the glioblastoma genome and epigenome.

Using the molecular classification of glioblastoma to inform personalized treatment

Glioblastoma is the most common and most aggressive diffuse glioma, associated with short survival and uniformly fatal outcome, irrespective of treatment. It is characterized by morphological, genetic and gene-expression heterogeneity. The current standard of treatment is maximal surgical resection, followed by radiation, with concurrent and adjuvant chemotherapy. Due to the heterogeneity, most tumours develop resistance to treatment and shortly recur. Following recurrence, glioblastoma is quickly fatal in the majority of cases. Recent genetic molecular advances have contributed to a better understanding of glioblastoma pathophysiology and disease stratification. In this paper we review basic glioblastoma pathophysiology, with emphasis on clinically relevant genetic molecular alterations and potential targets for further drug development.

Molecular diagnostics in paediatric glial tumours

Glial tumours in children have distinct patterns of epigenetic alteration, chromosomal structure, and gene and protein expression that differentiate them from their histological counterparts in adults. Understanding paediatric gliomas at the molecular level provides important prognostic and therapeutic insights, such as which genetic alterations confer a favourable response to adjuvant therapy, or which signalling pathways might be amenable to specific molecularly targeted agents. For clinicians, the ultimate goal is to individualise therapeutic regimens on the basis of the molecular fingerprint of a particular tumour and the prognosis conferred by this profile. In this Review, we examine a series of studies of molecular and genomic analysis of glial tumours in children, and discuss the many clinical insights that these molecular features provide.

Pediatric glioblastoma with oligodendroglioma component: aggressive clinical phenotype with distinct molecular characteristics

The 2007 World Health Organization classification defined a new variant of glioblastoma (GBM) containing oligodendroglioma foci as GBM with an oligodendroglioma component (GBMO), which shows a favorable clinical outcome compared with "classic" GBM. However, all of the reported cases of GBMO have been adult cases, with no previous reports of pediatric cases. In this report, we demonstrated molecular characteristics of a pediatric GBMO case, showing aggressive clinical behavior with 8-month overall survival. The case showed neither isocitrate dehydrogenase 1/2 genes (IDH1/2) mutation nor 1p/19q co-deletion, a hallmark of oligodendroglioal tumors. In addition, microsatellite instability, leading to the putative mechanism of temozolomide (TMZ) resistance, was frequently detected. Molecular genetic analysis may provide critical prognostic and therapeutic insights, especially for the pediatric glioma containing oligodendroglioma components.

Pediatric neuro-oncology: current status and future directions

Tumors of the central nervous system (CNS) are the most common solid malignancies in childhood and are the leading cause of cancer-related death in this age group. While an ongoing improvement in overall prognosis has been achieved in the last few decades, current therapeutic approaches still confer significant morbidities, especially for the very young. The traditional strategies of surgery, radiotherapy and conventional cytotoxic chemotherapy need to be further refined while newer approaches, including molecularly targeted agents, hold the promise of better responses, improved outcomes and reduced toxicities. This article discusses treatment standards, the focus of current clinical investigations and the future promise of novel, biologically based approaches for the most common pediatric CNS tumors: primitive neuroectodermal tumors including medulloblastomas, ependymomas and astrocytomas (both low-grade and high-grade glioma).

MGMT promoter gene methylation in pediatric glioblastoma: analysis using MS-MLPA

PURPOSE

Promoter methylation of the O⁶-methylguanine-DNA-methyltransferase (MGMT) gene is widely recognized as an important predictive factor in the treatment of glioblastoma (GBM) patients with temozolomide. However, data regarding the methylation status of the MGMT promoter in pediatric GBM are yet to be elucidated.

METHODS

Nineteen tissue samples of pediatric GBM were evaluated for the MGMT promoter methylation status using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA). Methylation status was also evaluated using methylation-specific polymerase chain reaction (MSP) for 17 of the 19 patients. The correlation between MGMT promoter methylation and clinical outcome was assessed.

RESULTS

Three of the 19 patients (16%) showed methylation of the MGMT promoter, according to MS-MLPA, as did 1 of the 17 (6%), according to MSP. The methylation status did not seem to have a definite effect on clinical outcome.

CONCLUSIONS

Pediatric GBMs rarely have methylated MGMT promoters. With a better clinical outcome and lower methylation rate than their adult counterparts, it may be suggested that, for pediatric GBM, MGMT promoter methylation does not play a significant role as a prognostic factor.