Imipridones affect tumor bioenergetics and promote cell lineage differentiation in diffuse midline gliomas

BACKGROUND

Pediatric diffuse midline gliomas (DMGs) are incurable childhood cancers. The imipridone ONC201 has shown early clinical efficacy in a subset of DMGs. However, the anticancer mechanisms of ONC201 and its derivative ONC206 have not been fully described in DMGs.

METHODS

DMG models including primary human in vitro (n = 18) and in vivo (murine and zebrafish) models, and patient (n = 20) frozen and FFPE specimens were used. Drug-target engagement was evaluated using in silico ChemPLP and in vitro thermal shift assay. Drug toxicity and neurotoxicity were assessed in zebrafish models. Seahorse XF Cell Mito Stress Test, MitoSOX and TMRM assays, and electron microscopy imaging were used to assess metabolic signatures. Cell lineage differentiation and drug-altered pathways were defined using bulk and single-cell RNA-seq.

RESULTS

ONC201 and ONC206 reduce viability of DMG cells in nM concentrations and extend survival of DMG PDX models (ONC201: 117 days, P = .01; ONC206: 113 days, P = .001). ONC206 is 10X more potent than ONC201 in vitro and combination treatment was the most efficacious at prolonging survival in vivo (125 days, P = .02). Thermal shift assay confirmed that both drugs bind to ClpP, with ONC206 exhibiting a higher binding affinity as assessed by in silico ChemPLP. ClpP activation by both drugs results in impaired tumor cell metabolism, mitochondrial damage, ROS production, activation of integrative stress response (ISR), and apoptosis in vitro and in vivo. Strikingly, imipridone treatment triggered a lineage shift from a proliferative, oligodendrocyte precursor-like state to a mature, astrocyte-like state.

CONCLUSION

Targeting mitochondrial metabolism and ISR activation effectively impairs DMG tumorigenicity. These results supported the initiation of two pediatric clinical trials (NCT05009992, NCT04732065).

Cooperation of Striatin 3 and MAP4K4 promotes growth and tissue invasion

MAP4K4 is associated with increased motility and reduced proliferation in tumor cells, but the regulation of this dichotomous functionality remained elusive. We find that MAP4K4 interacts with striatin 3 and 4 (STRN3/4) and that STRN3 and MAP4K4 exert opposing functions in Hippo signaling and clonal growth. However, depletion of either STRN3 or MAP4K4 in medulloblastoma cells reduces invasion, and loss of both proteins abrogates tumor cell growth in the cerebellar tissue. Mechanistically, STRN3 couples MAP4K4 to the protein phosphatase 2A, which inactivates growth repressing activities of MAP4K4. In parallel, STRN3 enables growth factor-induced PKCθ activation and direct phosphorylation of VASP_S157 by MAP4K4, which both are necessary for efficient cell invasion. VASP_S157 directed activity of MAP4K4 and STRN3 requires the CNH domain of MAP4K4, which mediates its interaction with striatins. Thus, STRN3 is a master regulator of MAP4K4 function, and disruption of its cooperation with MAP4K4 reactivates Hippo signaling and represses tissue invasion in medulloblastoma.

Analysis of the MAP4K4-STRN3 cooperation in medulloblastoma reveals its opposing regulation of Hippo activation and tissue invasion in cancer.

MODL-12.Ex vivo model identifies druggable vulnerabilities in medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumour in children and long-term sequelae in survivors caused by the harsh, non-targeted treatments is common. Current screening protocols for the detection of novel druggable vulnerabilities rely on 2D and 3D cell culture systems using established or primary tumour cells. However, these assays do neither provide the cellular, chemical and biophysical context of the tissue, nor reveal drug effects on the invasive behavior of the tumour cells. To overcome these limitations, we have established ex vivo Organotypic Cerebellum Slice Co-culture (OCSC) models for SHH and group 3 MB tumours, which provide spatio-temporal insights in the growth and dissemination behaviour of the tumour cells. OCSCs represent an excellent translational model for patient sample profiling, drug testing, and microenvironmental or explorative target identification studies in a physiologically relevant tissue context. We found that the AURKB inhibitor Barasertib (AZD-1152), which was ineffective to reduce ONS-76 cell invasion in vitro, effectively reduced tumour volume and proliferation of these SHH tumour cells in the tissue context. The AURKB inhibitor thus displays higher efficacy ex vivo, indicating an impact of the microenvironment on its functional activity. We further validated tumour suppressive activity of AURKB inhibition with Barasertib at low nanomolar concentration or with siRNA-mediated depletion of AURKB in Grp3 MB tumour cells and in primary tumour cells ex vivo, thereby confirming the therapeutic potential of AURKB inhibition against MB progression. We furthermore found that the combination of AURKB inhibition with irradiation or with the SRC inhibitor Dasatinib, lead to a near complete eradication of the tumour cells. Thus, OCSCs are a clinically relevant model where tumour material can be efficiently tested for drug sensitivities, which allowed us to identify AURKB inhibition as an effective treatment against tissue invasive MB.

Republication: Targeting PI3KC2β Impairs Proliferation and Survival in Acute Leukemia, Brain Tumours and Neuroendocrine Tumours

BACKGROUND

Eight human catalytic phosphoinositide 3-kinase (PI3K) isoforms exist which are subdivided into three classes. While class I isoforms have been well-studied in cancer, little is known about the functions of class II PI3Ks.

MATERIALS AND METHODS

The expression pattern and functions of the class II PI3KC2β isoform were investigated in a panel of tumour samples and cell lines.

RESULTS

Overexpression of PI3KC2β was found in subsets of tumours and cell lines from acute myeloid leukemia (AML), glioblastoma multiforme (GBM), medulloblastoma (MB), neuroblastoma (NB), and small cell lung cancer (SCLC). Specific pharmacological inhibitors of PI3KC2β or RNA interference impaired proliferation of a panel of human cancer cell lines and primary cultures. Inhibition of PI3KC2β also induced apoptosis and sensitised the cancer cells to chemotherapeutic agents.

CONCLUSION

Together, these data show that PI3KC2β contributes to proliferation and survival in AML, brain tumours and neuroendocrine tumours, and may represent a novel target in these malignancies.

Spatial proteomics finds CD155 and Endophilin-A1 as mediators of growth and invasion in medulloblastoma

The composition of the plasma membrane (PM)-associated proteome of tumor cells determines cell-cell and cell-matrix interactions and the response to environmental cues. Whether the PM-associated proteome impacts the phenotype of Medulloblastoma (MB) tumor cells and how it adapts in response to growth factor cues is poorly understood. Using a spatial proteomics approach, we observed that hepatocyte growth factor (HGF)-induced activation of the receptor tyrosine kinase c-MET in MB cells changes the abundance of transmembrane and membrane-associated proteins. The depletion of MAP4K4, a pro-migratory effector kinase downstream of c-MET, leads to a specific decrease of the adhesion and immunomodulatory receptor CD155 and of components of the fast-endophilin-mediated endocytosis (FEME) machinery in the PM-associated proteome of HGF-activated MB cells. The decreased surface expression of CD155 or of the fast-endophilin-mediated endocytosis effector endophilin-A1 reduces growth and invasiveness of MB tumor cells in the tissue context. These data thus describe a novel function of MAP4K4 in the control of the PM-associated proteome of tumor cells and identified two downstream effector mechanisms controlling proliferation and invasiveness of MB cells.

Central nervous system tumors in children under 5 years of age: a report on treatment burden, survival and long-term outcomes

Purpose

The challenges of treating central nervous system (CNS) tumors in young children are many. These include age-specific tumor characteristics, limited treatment options, and susceptibility of the developing CNS to cytotoxic therapy. The aim of this study was to analyze the long-term survival, health-related, and educational/occupational outcomes of this vulnerable patient population.

Methods

Retrospective study of 128 children diagnosed with a CNS tumor under 5 years of age at a single center in Switzerland between 1990 and 2019.

Results

Median age at diagnosis was 1.81 years [IQR, 0.98–3.17]. Median follow-up time of surviving patients was 8.39 years [range, 0.74–23.65]. The main tumor subtypes were pediatric low-grade glioma (36%), pediatric high-grade glioma (11%), ependymoma (16%), medulloblastoma (11%), other embryonal tumors (7%), germ cell tumors (3%), choroid plexus tumors (6%), and others (9%). The 5-year overall survival (OS) was 78.8% (95% CI, 71.8–86.4%) for the whole cohort. Eighty-seven percent of survivors > 5 years had any tumor- or treatment-related sequelae with 61% neurological complications, 30% endocrine sequelae, 17% hearing impairment, and 56% visual impairment at last follow-up. Most patients (72%) attended regular school or worked in a skilled job at last follow-up.

Conclusion

Young children diagnosed with a CNS tumor experience a range of complications after treatment, many of which are long-lasting and potentially debilitating. Our findings highlight the vulnerabilities of this population, the need for long-term support and strategies for rehabilitation, specifically tailored for young children.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11060-022-03963-3.

Mechanisms of imipridones in targeting mitochondrial metabolism in cancer cells

ONC201 is the first member of the imipridone family of anticancer drugs to enter the clinic for the treatment of diverse solid and hematologic cancers. A subset of pediatric and adult patients with highly aggressive brain tumors has shown remarkable clinical responses to ONC201, and recently, the more potent derivative ONC206 entered clinical trials as a single agent for the treatment of central nervous system (CNS) cancers. Despite the emerging clinical interest in the utility of imipridones, their exact molecular mechanisms are not fully described. In fact, the existing literature points to multiple pathways (e.g. tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) signaling, dopamine receptor antagonism, and mitochondrial metabolism) as putative drug targets. We have performed a comprehensive literature review and highlighted mitochondrial metabolism as the major target of imipridones. In support of this, we performed a meta-analysis of an ONC201 screen across 539 human cancer cell lines and showed that the mitochondrial caseinolytic protease proteolytic subunit (ClpP) is the most significant predictive biomarker of response to treatment. Herein, we summarize the main findings on the anticancer mechanisms of this potent class of drugs, provide clarity on their role, and identify clinically relevant predictive biomarkers of response.

Evaluation of Prognostic Factors and Role of Participation in a Randomized Trial or a Prospective Registry in Pediatric and Adolescent Nonmetastatic Medulloblastoma - A Report From the HIT 2000 Trial

Purpose

We aimed to compare treatment results in and outside of a randomized trial and to confirm factors influencing outcome in a large retrospective cohort of nonmetastatic medulloblastoma treated in Austria, Switzerland and Germany.

Methods and Materials

Patients with nonmetastatic medulloblastoma (n = 382) aged 4 to 21 years and primary neurosurgical resection between 2001 and 2011 were assessed. Between 2001 and 2006, 176 of these patients (46.1%) were included in the randomized HIT SIOP PNET 4 trial. From 2001 to 2011 an additional 206 patients were registered to the HIT 2000 study center and underwent the identical central review program. Three different radiation therapy protocols were applied. Genetically defined tumor entity (former molecular subgroup) was available for 157 patients.

Results

Median follow-up time was 7.3 (range, 0.09-13.86) years. There was no difference between HIT SIOP PNET 4 trial patients and observational patients outside the randomized trial, with 7 years progression-free survival rates (PFS) of 79.5% ± 3.1% versus 78.7% ± 3.1% (P = .62). On univariate analysis, the time interval between surgery and irradiation (≤ 48 days vs ≥ 49 days) showed a strong trend to affect PFS (80.4% ± 2.2% vs 64.6% ± 9.1%; P = .052). Furthermore, histologically and genetically defined tumor entities and the extent of postoperative residual tumor influenced PFS. On multivariate analyses, a genetically defined tumor entity wingless-related integration site-activated vs non-wingless-related integration site/non-SHH, group 3 hazard ratio, 5.49; P = .014) and time interval between surgery and irradiation (hazard ratio, 2.2; P = .018) were confirmed as independent risk factors.

Conclusions

Using a centralized review program and risk-stratified therapy for all patients registered to the study center, outcome was identical for patients with nonmetastatic medulloblastoma treated on and off the randomized HIT SIOP PNET 4 trial. The prognostic values of prolonged time to RT and genetically defined tumor entity were confirmed.

Real-time sensing of MAPK signaling in medulloblastoma cells reveals cellular evasion mechanism counteracting dasatinib blockade of ERK activation during invasion

Aberrantly activated kinase signaling pathways drive invasion and dissemination in medulloblastoma (MB). A majority of tumor-promoting kinase signaling pathways feed into the mitogen-activated protein kinase (MAPK) extracellular regulated kinase (ERK1/2) pathway. The activation status of ERK1/2 during invasion of MB cells is not known and its implication in invasion control unclear. We established a synthetic kinase activation relocation sensor (SKARS) for the MAPK ERK1/2 pathway in MB cells for real-time measuring of drug response. We used 3D invasion assays and organotypic cerebellum slice culture to test drug effects in a physiologically relevant tissue environment. We found that hepatocyte growth factor (HGF), epidermal growth factor (EGF), or basic fibroblast growth factor (bFGF) caused rapid nuclear ERK1/2 activation in MB cells, which persisted for several hours. Concomitant treatment with the BCR/ABL kinase inhibitor dasatinib completely repressed nuclear ERK1/2 activity induced by HGF and EGF but not by bFGF. Increased nuclear ERK1/2 activity correlated positively with speed of invasion. Dasatinib blocked ERK-associated invasion in the majority of cells, but we also observed fast-invading cells with low ERK1/2 activity. These ERK1/2-low, fast-moving cells displayed a rounded morphology, while ERK-high fast-moving cells displayed a mesenchymal morphology. Dasatinib effectively blocked EGF-induced proliferation while it only moderately repressed tissue invasion, indicating that a subset of cells may evade invasion repression by dasatinib through non-mesenchymal motility. Thus, growth factor-induced nuclear activation of ERK1/2 is associated with mesenchymal motility and proliferation in MB cells and can be blocked with the BCR/ABL kinase inhibitor dasatinib.

A single supratentorial high-grade neuroepithelial tumor with two distinct BCOR mutations, exceptionally long complete remission and survival

Here, we present a patient with high-grade neuroepithelial tumors with mutations in the BCL6 corepressor BCOR (HGNET-BCOR), a rare, highly malignant brain tumor with poor prognosis. The patient underwent gross total tumor resection (GTR), high-dose chemotherapy, and, after local relapse, GTR, proton radiation, and chemotherapy. After a 7.5 year-long complete remission, the tumor recurred locally, was treated by GTR, and responded to temozolomide treatment. In addition to an internal tandem duplication in BCOR common to the majority of HGNET-BCOR cases, molecular analysis revealed a second BCOR mutation in this tumor: a frame shift mutation. The combination of these mutations was associated with relatively low BCOR expression compared to other HGNET-BCOR cases.

A Weighted Genetic Risk Score of Adult Glioma Susceptibility Loci Associated with Pediatric Brain Tumor Risk

Genetic risk score (GRS) is used to demonstrate the genetic variants contributing to the polygenic architecture of complex diseases. By using a GRS, we have investigated the additive impact of the known adult glioma susceptibility loci on the pediatric brain tumor (PBT) risk and assessed the proportion of PBT heritability attributable to these susceptibility loci. A GRS was generated for PBTs based on the alleles and associated effect sizes derived from a previously published genome-wide association study on adult glioma. The GRS was calculated in CEFALO, a population-based case-control study of brain tumors in children and adolescents including saliva DNA of 245 cases and 489 controls. The unconditional logistic regression model was used to investigate the association between standardized GRS and risk of PBTs. To measure the variance explained by the effect of GRS, Nagelkerke pseudo-R2 was calculated. The GRS for adult brain tumors was associated with an increased risk of PBTs (OR 1.25 [95% CI 1.06-1.49], p = 0.009) and 0.3% of the variance in PBTs could be explained by the effect of GRS on the liability scale. This study provides evidence that heritable risks of PBTs are in-part attributable to some common genetic variants associated with adult glioma.

Alterations in ALK/ROS1/NTRK/MET drive a group of infantile hemispheric gliomas

Infant gliomas have paradoxical clinical behavior compared to those in children and adults: low-grade tumors have a higher mortality rate, while high-grade tumors have a better outcome. However, we have little understanding of their biology and therefore cannot explain this behavior nor what constitutes optimal clinical management. Here we report a comprehensive genetic analysis of an international cohort of clinically annotated infant gliomas, revealing 3 clinical subgroups. Group 1 tumors arise in the cerebral hemispheres and harbor alterations in the receptor tyrosine kinases ALK, ROS1, NTRK and MET. These are typically single-events and confer an intermediate outcome. Groups 2 and 3 gliomas harbor RAS/MAPK pathway mutations and arise in the hemispheres and midline, respectively. Group 2 tumors have excellent long-term survival, while group 3 tumors progress rapidly and do not respond well to chemoradiation. We conclude that infant gliomas comprise 3 subgroups, justifying the need for specialized therapeutic strategies.

Infant gliomas behave differently to their childhood or adult counterparts. Here, the authors perform a large-scale genetic analysis of these tumours, revealing genetic alterations which may offer therapeutic opportunities.

Management of Primary Tectal Plate Low-Grade Glioma in Pediatric Patients: Results of the Multicenter Treatment Study SIOP-LGG 2004

BACKGROUND

Tectal plate low-grade gliomas (LGGs) most often present with increased intracranial pressure and sometimes as incidental findings from brain imaging. Prognostic factors predicting outcome are largely unknown.

METHODS

From 2004 until 2012, 71 patients with tectal plate LGG from Germany and Switzerland were followed within the SIOP-LGG 2004 study. Median age at diagnosis was 9.7 (range: 0.1-17.5) years, and median follow-up time of surviving patients was 6.3 (interquartile range: 4.9-8.3) years.

RESULTS

A total of 41 out of 71 patients received no tumor treatment (12 with and 29 without biopsy). The 10-year event-free survival (EFS) rate (± standard error ) for patients with an initial tumor volume of ≤3 cm³ was 56% (±7%), as opposed to 12% (±8%) for those with tumors >3 cm³ (p < 0.001). The 10-year EFS for patients without contrast enhancement on initial magnetic resonance imaging (MRI) was 52% (±9%), and for those with enhancement, it was 23% (±9%) (p = 0.003). The 10-year overall survival rate was 96% (±3%) (death due to disease, 1; ventriculoperitoneal shunt infection, 1). Sixty-three (89%) patients had at least one cerebrospinal fluid diversion procedure.

CONCLUSIONS

More than half of patients were managed without tumor treatment. Favorable prognostic factors for EFS were small initial tumor volume (≤3cm³) and the absence of initial contrast enhancement on MRI. Overall survival was excellent.

Clinical, Radiologic, Pathologic, and Molecular Characteristics of Long-Term Survivors of Diffuse Intrinsic Pontine Glioma (DIPG): A Collaborative Report From the International and European Society for Pediatric Oncology DIPG Registries

Purpose Diffuse intrinsic pontine glioma (DIPG) is a brainstem malignancy with a median survival of < 1 year. The International and European Society for Pediatric Oncology DIPG Registries collaborated to compare clinical, radiologic, and histomolecular characteristics between short-term survivors (STSs) and long-term survivors (LTSs). Materials and Methods Data abstracted from registry databases included patients from North America, Australia, Germany, Austria, Switzerland, the Netherlands, Italy, France, the United Kingdom, and Croatia. Results Among 1,130 pediatric and young adults with radiographically confirmed DIPG, 122 (11%) were excluded. Of the 1,008 remaining patients, 101 (10%) were LTSs (survival ≥ 2 years). Median survival time was 11 months (interquartile range, 7.5 to 16 months), and 1-, 2-, 3-, 4-, and 5-year survival rates were 42.3% (95% CI, 38.1% to 44.1%), 9.6% (95% CI, 7.8% to 11.3%), 4.3% (95% CI, 3.2% to 5.8%), 3.2% (95% CI, 2.4% to 4.6%), and 2.2% (95% CI, 1.4% to 3.4%), respectively. LTSs, compared with STSs, more commonly presented at age < 3 or > 10 years (11% v 3% and 33% v 23%, respectively; P < .001) and with longer symptom duration ( P < .001). STSs, compared with LTSs, more commonly presented with cranial nerve palsy (83% v 73%, respectively; P = .008), ring enhancement (38% v 23%, respectively; P = .007), necrosis (42% v 26%, respectively; P = .009), and extrapontine extension (92% v 86%, respectively; P = .04). LTSs more commonly received systemic therapy at diagnosis (88% v 75% for STSs; P = .005). Biopsies and autopsies were performed in 299 patients (30%) and 77 patients (10%), respectively; 181 tumors (48%) were molecularly characterized. LTSs were more likely to harbor a HIST1H3B mutation (odds ratio, 1.28; 95% CI, 1.1 to 1.5; P = .002). Conclusion We report clinical, radiologic, and molecular factors that correlate with survival in children and young adults with DIPG, which are important for risk stratification in future clinical trials.

MAP4K4 controlled integrin β1 activation and c-Met endocytosis are associated with invasive behavior of medulloblastoma cells

Local tissue infiltration of Medulloblastoma (MB) tumor cells precedes metastatic disease but little is still known about intrinsic regulation of migration and invasion in these cells. We found that MAP4K4, a pro-migratory Ser/Thr kinase, is overexpressed in 30% of primary MB tumors and that increased expression is particularly associated with the frequently metastatic SHH β subtype. MAP4K4 is a driver of migration and invasion downstream of c-Met, which is transcriptionally up-regulated in SHH MB. Consistently, depletion of MAP4K4 in MB tumor cells restricts HGF-driven matrix invasion in vitro and brain tissue infiltration ex vivo. We show that these pro-migratory functions of MAP4K4 involve the activation of the integrin β-1 adhesion receptor and are associated with increased endocytic uptake. The consequent enhanced recycling of c-Met caused by MAP4K4 results in the accumulation of activated c-Met in cytosolic vesicles, which is required for sustained signaling and downstream pathway activation. The parallel increase of c-Met and MAP4K4 expression in SHH MB could predict an increased potential of these tumors to infiltrate brain tissue and cause metastatic disease. Molecular targeting of the underlying accelerated endocytosis and receptor recycling could represent a novel approach to block pro-migratory effector functions of MAP4K4 in metastatic cancers.

Management of primary thalamic low-grade glioma in pediatric patients: results of the multicenter treatment studies HIT-LGG 1996 and SIOP-LGG 2004

Background

Thalamic low-grade glioma (LGG) poses a special therapeutic challenge, as complete resection is often not possible. To determine the survival outcomes of mono- and bithalamic LGG, we analyzed a large cohort of pediatric patients.

Methods

From 1996 until 2012, 2618 patients were registered in the HIT-LGG 1996 and the SIOP-LGG 2004 studies. A total of 102 of these 2618 patients (3.9%) were diagnosed with a thalamic LGG with a median age at diagnosis of 8.0 years (range, 0.4-17.5 years); 87 patients (85%) had monothalamic and 15 patients (15%) had bithalamic LGG.

Results

Ninety patients received at least one surgical procedure. Thirty-one patients received radiotherapy and 24 patients received chemotherapy as a first-line, nonsurgical treatment indicated by radiological tumor progression or severe/progressive clinical symptoms. Patients with monothalamic tumors showed a 10-year overall survival (OS) rate of 91%, whereas patients with bithalamic tumors only reached 65% (P = .001). Bithalamic tumors more frequently showed diffuse histology than monothalamic tumors. Patients with diffuse astrocytoma had a lower 10-year OS (68%) than those with pilocytic astrocytoma (93%). The 10-year progression-free survival rate after the start of first nonsurgical treatment was 53% in the radiotherapy group and 34% in the chemotherapy group.

Conclusions

Thalamic glioma was manageable using a strategy that included surgery, observation, chemotherapy, and/or radiotherapy. Radiotherapy could be successfully deferred or obviated in a number of patients. Survival was high in among patients with monothalamic tumors. The worse prognosis associated with bithalamic tumors correlates with the higher rate of diffuse histology in this subgroup, precluding total or near-total resection.

Childhood cancer survival in Switzerland (1976-2013): Time-trends and predictors

Population-based studies on childhood cancer survival are key to monitor progress against cancer and to detect potential differences between regions and other subgroups in the population. We investigated time trends and factors associated with childhood cancer survival on a national level in Switzerland, from 1976 to 2013. We extracted data from the population-based Swiss Childhood Cancer Registry of 5,776 children (age 0-14 years) diagnosed with cancer from 1985 to 2014 in Switzerland. We calculated age-adjusted 5-year survival, defined the annual reduction in risk of death (ARR), and explored associations of survival with clinical and demographic factors. Overall, 5-year survival improved significantly, from 64% in 1976-1983 to 88% in 2004-2013. ARR over the whole period was 4% for all diagnostic groups, greatest for Hodgkin lymphomas (8%), ependymomas (6%), Burkitt's lymphomas (6%) and germ cell tumours (6%). Children treated in hospitals without specialised paediatric cancer centre for leukaemia (HR 12.9), lymphoma (HR 5.0) and neuroblastoma (HR 3.7) were at higher risk of death. In French-speaking Switzerland, risk of death was lower for lymphoma (HR 0.6), CNS tumours (HR 0.7) and neuroblastoma (HR 0.5). Children with migration background had a higher risk of death from all tumours except bone tumours. Childhood cancer survival significantly improved from 1976 to 2013, but there is room for further improvement. Survival rates varied by type of clinical treatment, language region and nationality. All paediatric cancer patients should be referred to a specialised paediatric cancer centre. Further research is needed to intervene and completely eliminate inequalities in survival.

MYC as Therapeutic Target for Embryonal Tumors: Potential and Challenges

The MYC family plays essential roles during brain development and their oncogenic deregulation is implicated in the formation of embryonal neural tumors such as medulloblastomas (MB) and neuroblastoma (NB). Amplification of the MYCN is the predominant marker for aggressive NB and correlates with poor prognosis, while c-MYC overexpression is a defining feature of MB subgroups inflected with aggressive biological behavior and increased likelihood of metastasis. Not surprisingly MYC has emerged as an attractive target for pediatric neural cancer therapy. However despite three decades of intensive research in MYC biology and an impressive number of 30,000 publications, inhibition of MYC as therapeutic strategy remains an elusive goal in cancer medicine. This review discusses the potential and challenges of targeting the oncogenic effects of MYC as therapeutic strategy for MYC over-expressing embryonal neural tumors where current therapies are inadequate.

Common genetic variations in cell cycle and DNA repair pathways associated with pediatric brain tumor susceptibility

Knowledge on the role of genetic polymorphisms in the etiology of pediatric brain tumors (PBTs) is limited. Therefore, we investigated the association between single nucleotide polymorphisms (SNPs), identified by candidate gene-association studies on adult brain tumors, and PBT risk.The study is based on the largest series of PBT cases to date. Saliva DNA from 245 cases and 489 controls, aged 7-19 years at diagnosis/reference date, was genotyped for 68 SNPs. Data were analyzed using unconditional logistic regression.The results showed EGFRrs730437 and EGFRrs11506105 may decrease susceptibility to PBTs, whereas ERCC1rs3212986 may increase risk of these tumors. Moreover, stratified analyses indicated CHAF1Ars243341, CHAF1Ars2992, and XRCC1rs25487 were associated with a decreased risk of astrocytoma subtype. Furthermore, an increased risk of non-astrocytoma subtype associated with EGFRrs9642393, EME1rs12450550, ATMrs170548, and GLTSCRrs1035938 as well as a decreased risk of this subtype associated with XRCC4rs7721416 and XRCC4rs2662242 were detected.This study indicates SNPs in EGFR, ERCC1, CHAF1A, XRCC1, EME1, ATM, GLTSCR1, and XRCC4 may be associated with the risk of PBTs. Therefore, cell cycle and DNA repair pathways variations associated with susceptibility to adult brain tumors also seem to be associated with PBT risk, suggesting pediatric and adult brain tumors might share similar etiological pathways.

The Changing Landscape of Pediatric Low-Grade Gliomas: Clinical Challenges and Emerging Therapies

Pediatric low-grade gliomas (PLGGs) are the most common brain tumors in children. Though histologically benign and associated with excellent outcome, patients with unresectable lesions--mostly young children with midline tumors--experience multiple progressions and are at increased risk for long-term neurological sequelae. PLGGs in children with underlying genetic predisposition syndromes--especially neurofibromatosis type 1 and tuberous sclerosis--have a distinct natural history and biology with important treatment implications. Given the complexity of medical issues, optimal management requires a large network of health care providers; treatment decisions must address both tumor control and potential side effects of the therapy. Current treatment strategies often fail to induce sustained tumor regression and many children require several lines of therapy, highlighting the need for novel therapies. Here, we review the current management of PLGG and discuss how new molecular targets--in particular alterations of the Ras/MAPK pathway--are rapidly changing our approach to PLGG.

Ventricular Catheter Systems with Subcutaneous Reservoirs (Ommaya Reservoirs) in Pediatric Patients with Brain Tumors: Infections and Other Complications

OBJECTIVE

This study aims to describe complications related to ventricular catheter systems with subcutaneous reservoirs (VCSR) (such as Ommaya reservoirs) in pediatric patients with brain tumors.

METHODS

Retrospective analysis of consecutive patients with a total of 31 VCSR treated at the Children's University Hospital of Zurich, Switzerland.

RESULTS

A total of 20 patients with a median age of 3.3 years at VCSR implantation received 31 VCSR. Overall, 19 complications in 11 patients were recorded: 7 patients had a VCSR-related infection with coagulase-negative staphylococci, 4 of these probably as a surgical complication and 3 probably related to VCSR use. Systemic perioperative prophylaxis was administered in 22 cases, and intraventricular vancomycin and gentamicin were given in 8 cases (none of which subsequently developed an infection). Other complications included wound dehiscence, catheter malplacement, and leakage of cerebrospinal fluid. Overall, 17 VCSR were explanted due to complications.

CONCLUSION

Infections were the most frequent VCSR-related complication. In our own institution, the high rate of complications led to the definition of a bundle of measures as a standard operating procedure for VCSR placement and use. Prospective studies in larger patient collectives are warranted to better identify risk factors and evaluate preventive measures such as the administration of perioperative antibiotics and the use of antimicrobial coating of catheters.

Computer-assisted quantification of motile and invasive capabilities of cancer cells

High-throughput analysis of cancer cell dissemination and its control by extrinsic and intrinsic cellular factors is hampered by the lack of adequate and efficient analytical tools for quantifying cell motility. Oncology research would greatly benefit from such a methodology that allows to rapidly determine the motile behaviour of cancer cells under different environmental conditions, including inside three-dimensional matrices. We combined automated microscopy imaging of two- and three-dimensional cell cultures with computational image analysis into a single assay platform for studying cell dissemination in high-throughput. We have validated this new approach for medulloblastoma, a metastatic paediatric brain tumour, in combination with the activation of growth factor signalling pathways with established pro-migratory functions. The platform enabled the detection of primary tumour and patient-derived xenograft cell sensitivity to growth factor-dependent motility and dissemination and identified tumour subgroup-specific responses to selected growth factors of excellent diagnostic value.

Image-based RNA interference screening reveals an individual dependence of acute lymphoblastic leukemia on stromal cysteine support

Interactions with the bone marrow microenvironment are essential for leukemia survival and disease progression. We developed an imaging-based RNAi platform to identify protective cues from bone marrow derived mesenchymal stromal cells (MSC) that promote survival of primary acute lymphoblastic leukemia (ALL) cells. Using a candidate gene approach, we detected distinct responses of individual ALL cases to RNA interference with stromal targets. The strongest effects were observed when interfering with solute carrier family 3 member 2 (SLC3A2) expression, which forms the cystine transporter x_c⁻ when associated with SLC7A11. Import of cystine and metabolism to cysteine by stromal cells provides the limiting substrate to generate and maintain glutathione in ALL. This metabolic interaction reduces oxidative stress in ALL cells that depend on stromal x_c⁻. Indeed, cysteine depletion using cysteine dioxygenase resulted in leukemia cell death. Thus, functional evaluation of intercellular interactions between leukemia cells and their microenvironment identifies a selective dependency of ALL cells on stromal metabolism for a relevant subgroup of cases, providing new opportunities to develop more personalized approaches to leukemia treatment.

Contrast-enhanced MRI of the temporomandibular joint: findings in children without juvenile idiopathic arthritis

BACKGROUND

Contrast-enhanced magnetic resonance imaging (MRI) is highly sensitive for assessing temporomandibular joint (TMJ) involvement in juvenile idiopathic arthritis (JIA), but only sparse data exist on normal TMJ appearance in children.

PURPOSE

To determine normal MRI appearance and enhancement pattern of pediatric TMJ as basis for diagnosing early arthritis.

MATERIAL AND METHODS

In 27 children (age range, 1.2-16.8 years) without TMJ pathology undergoing head MRI, fat-saturated T2-weighted (T2W) and postcontrast fat-saturated T1-weighted (T1W) images sagittally aligned to the 54 TMJs, besides standard T1W and T2W images, were assessed for bony and soft tissue signal intensity (SI), the amount of perceptible joint fluid, and contrast enhancement (CE).

RESULTS

Bone marrow SI and CE of the mandible were consistent with varying degrees of residual red marrow in 96% of joints. The mandibular condyles were mostly isointense to the ramus, but in 9% showed mild edema-like bone marrow SI and CE. Small amounts of intraarticular fluid were detected in 31% on T2W images without fat saturation and in 83% on T2W images with fat saturation as fine lines in the upper or lower joint compartment or as small dots in an articular recess. Seventy-nine percent of all TMJs showed intense joint enhancement on early images restricted to areas of intraarticular fluid.

CONCLUSION

Small amounts of joint fluid with intense CE are a common MRI finding in TMJs of children without JIA and therefore should not be considered diagnostic for early arthritis.

CCDC26, CDKN2BAS, RTEL1 and TERT Polymorphisms in pediatric brain tumor susceptibility

The role of genetic polymorphisms in pediatric brain tumor (PBT) etiology is poorly understood. We hypothesized that single nucleotide polymorphisms (SNPs) identified in genome-wide association studies (GWAS) on adult glioma would also be associated with PBT risk. The study is based on the Cefalo study, a population-based multicenter case-control study. Saliva DNA from 245 cases and 489 controls, aged 7-19 years at diagnosis/reference date, was extracted and genotyped for 29 SNPs reported by GWAS to be significantly associated with risk of adult glioma. Data were analyzed using unconditional logistic regression. Stratified analyses were performed for two histological subtypes: astrocytoma alone and the other tumor types combined. The results indicated that four SNPs, CDKN2BAS rs4977756 (p = 0.036), rs1412829 (p = 0.037), rs2157719 (p = 0.018) and rs1063192 (p = 0.021), were associated with an increased susceptibility to PBTs, whereas the TERT rs2736100 was associated with a decreased risk (p = 0.018). Moreover, the stratified analyses showed a decreased risk of astrocytoma associated with RTEL1 rs6089953, rs6010620 and rs2297440 (p trend = 0.022, p trend = 0.042, p trend = 0.029, respectively) as well as an increased risk of this subtype associated with RTEL1 rs4809324 (p trend = 0.033). In addition, SNPs rs10464870 and rs891835 in CCDC26 were associated with an increased risk of non-astrocytoma tumor subtypes (p trend = 0.009, p trend = 0.007, respectively). Our findings indicate that SNPs in CDKN2BAS, TERT, RTEL1 and CCDC26 may be associated with the risk of PBTs. Therefore, we suggest that pediatric and adult brain tumors might share common genetic risk factors and similar etiological pathways.

Background ionizing radiation and the risk of childhood cancer: a census-based nationwide cohort study

BACKGROUND

Exposure to medium or high doses of ionizing radiation is a known risk factor for cancer in children. The extent to which low-dose radiation from natural sources contributes to the risk of childhood cancer remains unclear.

OBJECTIVES

In a nationwide census-based cohort study, we investigated whether the incidence of childhood cancer was associated with background radiation from terrestrial gamma and cosmic rays.

METHODS

Children < 16 years of age in the Swiss National Censuses in 1990 and 2000 were included. The follow-up period lasted until 2008, and incident cancer cases were identified from the Swiss Childhood Cancer Registry. A radiation model was used to predict dose rates from terrestrial and cosmic radiation at locations of residence. Cox regression models were used to assess associations between cancer risk and dose rates and cumulative dose since birth.

RESULTS

Among 2,093,660 children included at census, 1,782 incident cases of cancer were identified including 530 with leukemia, 328 with lymphoma, and 423 with a tumor of the central nervous system (CNS). Hazard ratios for each millisievert increase in cumulative dose of external radiation were 1.03 (95% CI: 1.01, 1.05) for any cancer, 1.04 (95% CI: 1.00, 1.08) for leukemia, 1.01 (95% CI: 0.96, 1.05) for lymphoma, and 1.04 (95% CI: 1.00, 1.08) for CNS tumors. Adjustment for a range of potential confounders had little effect on the results.

CONCLUSIONS

Our study suggests that background radiation may contribute to the risk of cancer in children, including leukemia and CNS tumors.

Intraoperative Monitoring of Facial Nerve Motor-Evoked Potentials in Children

OBJECTIVE

To determine whether transcranial motor-evoked potential monitoring of the facial nerve (FNMEP) during eloquent tumor resection is feasible in children and can predict both immediate and postoperative facial nerve (FN) function.

METHODS

We included 24 consecutive procedures involving 21 patients (median age 5.5 years, range 5 months to 15 years, 8 female) who were operated on with FNMEP monitoring by the first author in 2013 and 2014. During surgery, we maintained a constant response amplitude by increasing the stimulation intensity and aimed to establish a warning criterion based on the "threshold-level" method. A threshold increase of greater than 20 mA for eliciting the FNMEP in the most reliable facial nerve target muscle was considered to be a prediction of reduced postoperative facial nerve function and consequently, a warning was given to the surgeon. The preoperative and early postoperative function was documented with the House-Brackmann grading system.

RESULTS

Monitoring of the FNMEP was feasible in all the surgeries in at least one facial nerve target muscle. The orbicularis oris muscle yielded the best result (95% of the trials), followed by the mentalis (87%) and orbicularis oculi muscles (86%). The median stimulation threshold was initially 65 mA (range 40-110 mA) for the FNMEP and 60 mA (15-220 mA) for the motor-evoked potential of the thenar muscles. The FNMEP deterioration showed a sensitivity of 100% for House-Brackmann deterioration and specificity of 74%.

CONCLUSIONS

Intraoperative FNMEP monitoring is feasible and safe in infants and children. We found no evidence that the procedures and thresholds should differ from FNMEP monitoring in adults. FNMEP monitoring provides valid evidence for FN function in pediatric eloquent area surgery; its use is complementary to direct electrical FN stimulation and continuous EMG monitoring of FN target muscles.

Microbeam radiation therapy: Clinical perspectives

Microbeam radiation therapy (MRT), a novel form of spatially fractionated radiotherapy (RT), uses arrays of synchrotron-generated X-ray microbeams (MB). MRT has been identified as a promising treatment concept that might be applied to patients with malignant central nervous system (CNS) tumours for whom, at the current stage of development, no satisfactory therapy is available yet. Preclinical experimental studies have shown that the CNS of healthy rodents and piglets can tolerate much higher radiation doses delivered by spatially separated MBs than those delivered by a single, uninterrupted, macroscopically wide beam. High-dose, high-precision radiotherapies such as MRT with reduced probabilities of normal tissue complications offer prospects of improved therapeutic ratios, as extensively demonstrated by results of experiments published by many international groups in the last two decades. The significance of developing MRT as a new RT approach cannot be understated. Up to 50% of cancer patients receive conventional RT, and any new treatment that provides better tumour control whilst preserving healthy tissue is likely to significantly improve patient outcomes.

The Ser/Thr kinase MAP4K4 drives c-Met-induced motility and invasiveness in a cell-based model of SHH medulloblastoma

Medulloblastoma (MB) comprises four molecularly and genetically distinct subgroups of embryonal brain tumors that develop in the cerebellum. MB mostly affects infants and children and is difficult to treat because of frequent dissemination of tumor cells within the leptomeningeal space. A potential promoter of cell dissemination is the c-Met proto-oncogene receptor tyrosine kinase, which is aberrantly expressed in many human tumors including MB. Database analysis showed that c-Met is highly expressed in the sonic hedgehog (SHH) subgroup and in a small subset of Group 3 and Group 4 MB tumors. Using a cell-based three-dimensional cell motility assay combined with live-cell imaging, we investigated whether the c-Met ligand HGF could drive dissemination of MB cells expressing high levels of c-Met, and determined downstream effector mechanisms of this process. We detected variable c-Met expression in different established human MB cell lines, and we found that in lines expressing high c-Met levels, HGF promoted cell dissemination and invasiveness. Specifically, HGF-induced c-Met activation enhanced the capability of the individual cells to migrate in a JNK-dependent manner. Additionally, we identified the Ser/Thr kinase MAP4K4 as a novel driver of c-Met-induced invasive cell dissemination. This increased invasive motility was due to MAP4K4 control of F-actin dynamics in structures required for migration and invasion. Thus, MAP4K4 couples growth factor signaling to actin cytoskeleton regulation in tumor cells, suggesting that MAP4K4 could present a promising novel target to be evaluated for treating growth factor-induced dissemination of MB tumors of different subgroups and of other human cancers.

MicroRNA signatures as biomarkers and therapeutic target for CNS embryonal tumors: the pros and the cons

Embryonal tumors of the central nervous system represent a heterogeneous group of childhood cancers with an unknown pathogenesis; diagnosis, on the basis of histological appearance alone, is controversial and patients’ response to therapy is difficult to predict. They encompass medulloblastoma, atypical teratoid/rhabdoid tumors and a group of primitive neuroectodermal tumors. All are aggressive tumors with the tendency to disseminate throughout the central nervous system. The large amount of genomic and molecular data generated over the last 5–10 years encourages optimism that new molecular targets will soon improve outcomes. Recent neurobiological studies have uncovered the key role of microRNAs (miRNAs) in embryonal tumors biology and their potential use as biomarkers is increasingly being recognized and investigated. However the successful use of microRNAs as reliable biomarkers for the detection and management of pediatric brain tumors represents a substantial challenge. This review debates the importance of miRNAs in the biology of central nervous systemembryonal tumors focusing on medulloblastoma and atypical teratoid/rhabdoid tumors and highlights the advantages as well as the limitations of their prospective application as biomarkers and candidates for molecular therapeutic targets.

NOTCH ligands JAG1 and JAG2 as critical pro-survival factors in childhood medulloblastoma

Medulloblastoma (MB), the most common pediatric malignant brain cancer, typically arises as pathological result of deregulated developmental pathways, including the NOTCH signaling cascade. Unlike the evidence supporting a role for NOTCH receptors in MB development, the pathological functions of NOTCH ligands remain largely unexplored. By examining the expression in large cohorts of MB primary tumors, and in established in vitro MB models, this research study demonstrates that MB cells bear abnormal levels of distinct NOTCH ligands. We explored the potential association between NOTCH ligands and the clinical outcome of MB patients, and investigated the rational of inhibiting NOTCH signaling by targeting specific ligands to ultimately provide therapeutic benefits in MB. The research revealed a significant over-expression of ligand JAG1 in the vast majority of MBs, and proved that JAG1 mediates pro-proliferative signals via activation of NOTCH2 receptor and induction of HES1 expression, thus representing an attractive therapeutic target. Furthermore, we could identify a clinically relevant association between ligand JAG2 and the oncogene MYC, specific for MYC-driven Group 3 MB cases. We describe for the first time a mechanistic link between the oncogene MYC and NOTCH pathway in MB, by identifying JAG2 as MYC target, and by showing that MB cells acquire induced expression of JAG2 through MYC-induced transcriptional activation. Finally, the positive correlation of MYC and JAG2 also with aggressive anaplastic tumors and highly metastatic MB stages suggested that high JAG2 expression may be useful as additional marker to identify aggressive MBs.

Epigenetic silencing of miRNA-9 is associated with HES1 oncogenic activity and poor prognosis of medulloblastoma

BACKGROUND

microRNA-9 is a key regulator of neuronal development aberrantly expressed in brain malignancies, including medulloblastoma. The mechanisms by which microRNA-9 contributes to medulloblastoma pathogenesis remain unclear, and factors that regulate this process have not been delineated.

METHODS

Expression and methylation status of microRNA-9 in medulloblastoma cell lines and primary samples were analysed. The association of microRNA-9 expression with medulloblastoma patients' clinical outcome was assessed, and the impact of microRNA-9 restoration was functionally validated in medulloblastoma cells.

RESULTS

microRNA-9 expression is repressed in a large subset of MB samples compared with normal fetal cerebellum. Low microRNA-9 expression correlates significantly with the diagnosis of unfavourable histopathological variants and with poor clinical outcome. microRNA-9 silencing occurs via cancer-specific CpG island hypermethylation. HES1 was identified as a direct target of microRNA-9 in medulloblastoma, and restoration of microRNA-9 was shown to trigger cell cycle arrest, to inhibit clonal growth and to promote medulloblastoma cell differentiation.

CONCLUSIONS

microRNA-9 is a methylation-silenced tumour suppressor that could be a potential candidate predictive marker for poor prognosis of medulloblastoma. Loss of microRNA-9 may confer a proliferative advantage to tumour cells, and it could possibly contribute to disease pathogenesis. Thus, re-expression of microRNA-9 may constitute a novel epigenetic regulation strategy against medulloblastoma.

Apparent diffusion coefficient of pediatric cerebellar tumors: a biomarker of tumor grade?

BACKGROUND

The role of diffusion weighted imaging (DWI) to reliably differentiate tumor types and grades in pediatric cerebellar tumors is controversial. We aimed to clarify the discrepancy reported in previous articles.

PROCEDURES

We retrospectively evaluated the apparent diffusion coefficient (ADC) values of the enhancing, solid parts of cerebellar tumors and correlated the absolute tumor ADC values and cerebellar and thalamic ratios with histology in a cohort of children with cerebellar tumors.

RESULTS

Twenty-four children (12 females) were included in the study. The median age at pre-surgical MRI was 10 years (range 29 days-18.5 years). Absolute ADC values (mean 1.49, SD 0.25 vs. 0.63 ± 0.18), cerebellar (2.04 ± 0.33 vs. 0.83 ± 0.25), and thalamic ratio (1.98 ± 0.35 vs. 0.79 ± 0.23) were significantly higher in low- than in high-grade tumors (P < 0.0001). Absolute ADC values and cerebellar and thalamic ratios were significantly higher in low-grade astrocytomas than in MBs. Overlap was seen for WHO grade II and III ependymomas. One hundred percent specific cutoff ADC values of >1.2 × 10(3) and <0.8 × 10(-3) mm(2) /s were established for low- and high-grade tumors.

CONCLUSION

ADC analysis of the solid, contrast enhancing components of pediatric cerebellar tumors may facilitate differentiation between various tumor histologies.

Natural history of a medulloblastoma: 30 months of wait and see in a child with a cerebellar incidentaloma

INTRODUCTION

With the increasing use of neuroimaging studies, the discovery of incidental neoplastic lesions is becoming more frequent. However, standard procedures are lacking, and little is known about their optimal management.

CASE REPORT

We here present the case of a boy with a cerebellar mass incidentally discovered on a CT scan performed after head trauma. In another scan performed after another incident of head trauma 14 months earlier, the lesion could be seen after retrospective examination. In view of the asymptomatic clinical and stable radiological status and the presumed diagnosis of a low-grade glioma, a watch-and-wait strategy was elected. After clinical and radiological progression was observed, the tumour was resected, 2½ years after the initial imaging study. Histological evaluation revealed a WNT pathway-activated classical medulloblastoma.

DISCUSSION

To our knowledge, this is the first description of such a long natural history and pre-symptomatic period of a medulloblastoma. The long period of stability followed by a period of accelerated tumour growth is compatible with increasing biological aggressiveness, possibly related to the stepwise accumulation of genetic changes.

Isolated intraspinal juvenile xanthogranuloma in an infant presenting as acute paraplegia

Juvenile xanthogranuloma is a histiocytic proliferative disease that predominantly affects the skin. Extracutaneous involvement is rare. We present the case of a 6-month-old infant with acute paraplegia. Magnetic resonance imaging showed an intraspinal extradural mass at midthoracic level with marked compression of the spinal cord. Complete tumor removal was achieved by emergency surgery and was followed by complete neurologic recovery. Histologic examination led to the diagnosis of a juvenile xanthogranuloma. To the best of our knowledge, an isolated intraspinal juvenile xanthogranuloma in the first 12 months of life has not been described before.

Novel agents targeting the IGF-1R/PI3K pathway impair cell proliferation and survival in subsets of medulloblastoma and neuroblastoma

The receptor tyrosine kinase (RTK)/phosphoinositide 3-kinase (PI3K) pathway is fundamental for cancer cell proliferation and is known to be frequently altered and activated in neoplasia, including embryonal tumors. Based on the high frequency of alterations, targeting components of the PI3K signaling pathway is considered to be a promising therapeutic approach for cancer treatment. Here, we have investigated the potential of targeting the axis of the insulin-like growth factor-1 receptor (IGF-1R) and PI3K signaling in two common cancers of childhood: neuroblastoma, the most common extracranial tumor in children and medulloblastoma, the most frequent malignant childhood brain tumor. By treating neuroblastoma and medulloblastoma cells with R1507, a specific humanized monoclonal antibody against the IGF-1R, we could observe cell line-specific responses and in some cases a strong decrease in cell proliferation. In contrast, targeting the PI3K p110α with the specific inhibitor PIK75 resulted in broad anti-proliferative effects in a panel of neuro- and medulloblastoma cell lines. Additionally, sensitization to commonly used chemotherapeutic agents occurred in neuroblastoma cells upon treatment with R1507 or PIK75. Furthermore, by studying the expression and phosphorylation state of IGF-1R/PI3K downstream signaling targets we found down-regulated signaling pathway activation. In addition, apoptosis occurred in embryonal tumor cells after treatment with PIK75 or R1507. Together, our studies demonstrate the potential of targeting the IGF-1R/PI3K signaling axis in embryonal tumors. Hopefully, this knowledge will contribute to the development of urgently required new targeted therapies for embryonal tumors.

Incidental findings of mass lesions on neuroimages in children

Increasing use of neuroimaging in children has led to more incidental findings of CNS mass lesions, the management of which is uncertain. The authors' aims in this study are to describe these mass lesions and their evolution, as well as to discuss the management options and determine the prevalence of incidental CNS mass lesions at their pediatric clinic. A retrospective study was undertaken in children with primary CNS tumors who were younger than 18 years old and were admitted to the University Children's Hospital of Zurich, Switzerland, between January 1995 and December 2010. In 19 (5.7%) of 335 patients with newly diagnosed CNS tumors, the diagnosis of a CNS mass lesion was an incidental finding. Reasons for obtaining neuroimages in these 19 patients were head trauma (in 6 patients); research protocols (in 3); nasal/orbital malformations (in 2); endocrinological and psychiatric evaluations (in 2); and vertebral bone anomaly without neurological signs, absence seizures, congenital ataxia, recurrent vomiting, developmental delay, and "check-up" at the explicit request of the parents (in 1 patient each). Seven patients underwent immediate surgery for low-grade glioma (4 patients) and craniopharyngioma, ependymoma, and choroid plexus papilloma (1 patient each); and 12 were treated conservatively or were observed. Ten of 12 conservatively treated patients remained stable (median follow-up time 1.8 years) and the other 2 underwent delayed surgery because of tumor progression (medulloblastoma in one patient and fibrillary astrocytoma in the other). Clinicians are increasingly challenged by the discovery of incidental CNS mass lesions. A subgroup of such lesions (with typical imaging patterns such as tectal glioma and dysembryoplastic neuroepithelial tumor) can be monitored conservatively, clinically, and radiographically. Future prospective studies are needed to define optimal management strategies based on larger collections of natural histories, as well as to assess the true prevalence of incidental CNS mass lesions.

Incidental findings of mass lesions on neuroimages in children

Increasing use of neuroimaging in children has led to more incidental findings of CNS mass lesions, the management of which is uncertain. The authors' aims in this study are to describe these mass lesions and their evolution, as well as to discuss the management options and determine the prevalence of incidental CNS mass lesions at their pediatric clinic. A retrospective study was undertaken in children with primary CNS tumors who were younger than 18 years old and were admitted to the University Children's Hospital of Zurich, Switzerland, between January 1995 and December 2010. In 19 (5.7%) of 335 patients with newly diagnosed CNS tumors, the diagnosis of a CNS mass lesion was an incidental finding. Reasons for obtaining neuroimages in these 19 patients were head trauma (in 6 patients); research protocols (in 3); nasal/orbital malformations (in 2); endocrinological and psychiatric evaluations (in 2); and vertebral bone anomaly without neurological signs, absence seizures, congenital ataxia, recurrent vomiting, developmental delay, and "check-up" at the explicit request of the parents (in 1 patient each). Seven patients underwent immediate surgery for low-grade glioma (4 patients) and craniopharyngioma, ependymoma, and choroid plexus papilloma (1 patient each); and 12 were treated conservatively or were observed. Ten of 12 conservatively treated patients remained stable (median follow-up time 1.8 years) and the other 2 underwent delayed surgery because of tumor progression (medulloblastoma in one patient and fibrillary astrocytoma in the other). Clinicians are increasingly challenged by the discovery of incidental CNS mass lesions. A subgroup of such lesions (with typical imaging patterns such as tectal glioma and dysembryoplastic neuroepithelial tumor) can be monitored conservatively, clinically, and radiographically. Future prospective studies are needed to define optimal management strategies based on larger collections of natural histories, as well as to assess the true prevalence of incidental CNS mass lesions.

Targeting PI3KC2β impairs proliferation and survival in acute leukemia, brain tumours and neuroendocrine tumours

BACKGROUND

Eight human catalytic phosphoinositide 3-kinase (PI3K) isoforms exist which are subdivided into three classes. While class I isoforms have been well-studied in cancer, little is known about the functions of class II PI3Ks.

MATERIALS AND METHODS

The expression pattern and functions of the class II PI3KC2β isoform were investigated in a panel of tumour samples and cell lines.

RESULTS

Overexpression of PI3KC2β was found in subsets of tumours and cell lines from acute myeloid leukemia (AML), glioblastoma multiforme (GBM), medulloblastoma (MB), neuroblastoma (NB), and small cell lung cancer (SCLC). Specific pharmacological inhibitors of PI3KC2β or RNA interference impaired proliferation of a panel of human cancer cell lines and primary cultures. Inhibition of PI3KC2β also induced apoptosis and sensitised the cancer cells to chemotherapeutic agents.

CONCLUSION

Together, these data show that PI3KC2β contributes to proliferation and survival in AML, brain tumours and neuroendocrine tumours, and may represent a novel target in these malignancies.

Pharmacological activation of the p53 pathway by nutlin-3 exerts anti-tumoral effects in medulloblastomas

Medulloblastomas account for 20% of pediatric brain tumors. With an overall survival of 40%-70%, their treatment is still a challenge. The majority of medulloblastomas lack p53 mutations, but even in cancers retaining wild-type p53, the tumor surveillance function of p53 is inhibited by the oncoprotein MDM2. Deregulation of the MDM2/p53 balance leads to malignant transformation. Here, we analyzed MDM2 mRNA and protein expression in primary medulloblastomas and normal cerebellum and assessed the mutational status of p53 and MDM2 expression in 6 medulloblastoma cell lines. MDM2 expression was elevated in medulloblastomas, compared with cerebellum. Four of 6 medulloblastoma cell lines expressed wild-type p53 and high levels of MDM2. The tumor-promoting p53-MDM2 interaction can be inhibited by the small molecule, nutlin-3, restoring p53 function. Targeting the p53-MDM2 axis using nutlin-3 significantly reduced cell viability and induced either cell cycle arrest or apoptosis and expression of the p53 target gene p21 in these 4 cell lines. In contrast, DAOY and UW-228 cells harboring TP53 mutations were almost unaffected by nutlin-3 treatment. MDM2 knockdown in medulloblastoma cells by siRNA mimicked nutlin-3 treatment, whereas expression of dominant negative p53 abrogated nutlin-3 effects. Oral nutlin-3 treatment of mice with established medulloblastoma xenografts inhibited tumor growth and significantly increased survival. Thus, nutlin-3 reduced medulloblastoma cell viability in vitro and in vivo by re-activating p53 function. We suggest that inhibition of the MDM2-p53 interaction with nutlin-3 is a promising therapeutic option for medulloblastomas with functional p53 that should be further evaluated in clinical trials.

Anaplastic ganglioglioma: a very rare intramedullary spinal cord tumor

Gangliogliomas (GGs) are a small subset of intramedullary spinal cord tumors in children. The anaplastic variant (WHO grade III) appears to be an extreme rarity. A literature research revealed only 15 case reports of intramedullary anaplastic GGs (aGGs) and only 4 pediatric patients. The course of an 18-month-old boy with sudden onset of paraparesis is presented. Spinal MRI revealed a contrast-enhancing intramedullary tumor ranging from T6 to T12. The patient underwent a standard laminectomy/laminoplasty and gross total resection of the lesion. His neurological status remained unchanged postoperatively and he recovered very well during outpatient neurorehabilitation. Neuropathologic examination revealed an aGG of WHO grade III. Because of the high-grade histology, adjuvant radiotherapy and chemotherapy with temozolomide were administered. The patient subsequently recovered to a normal functional status. Clinical and radiographic progression-free survival is now 4 years. Based on an extensive literature review, this is only the fifth pediatric patient with a primary intramedullary aGG and the second with documented progression-free survival of over 4 years. Another 4 primary intramedullary aGGs in adults and 7 patients with spinal dissemination from a cerebral aGG or malignant transformation of a low-grade GG have been reported. In comparison to the published case reports, which often indicate significant neurological dysfunction and rather short survival, the neurological recovery in this patient was favorable, and the oncologic outcome even more so. This is an argument for the use of the aggressive treatment regimen of complete resection followed by radio- and chemotherapy applied here.