Cognitive consequences of the treatment of medulloblastoma among children

Neuroimaging Biomarkers and Neurocognitive Outcomes in Pediatric Medulloblastoma Patients: a Systematic Review

Medulloblastoma is a malign posterior fossa brain tumor, mostly occurring in childhood. The CNS-directed chemoradiotherapy treatment can be very harmful to the developing brain and functional outcomes of these patients. However, what the underlying neurotoxic mechanisms are remain inconclusive. Hence, this review summarizes the existing literature on the association between advanced neuroimaging and neurocognitive changes in patients that were treated for pediatric medulloblastoma. The PubMed/Medline database was extensively screened for studies investigating the link between cognitive outcomes and multimodal magnetic resonance (MR) imaging in childhood medulloblastoma survivors. A behavioral meta-analysis was performed on the available IQ scores. A total of 649 studies were screened, of which 22 studies were included. Based on this literature review, we conclude medulloblastoma patients to be at risk for white matter volume loss, more frequent white matter lesions, and changes in white matter microstructure. Such microstructural alterations were associated with lower IQ, which reached the clinical cut-off in survivors across studies. Using functional MR scans, changes in activity were observed in cerebellar areas, associated with working memory and processing speed. Finally, cerebral microbleeds were encountered more often, but these were not associated with cognitive outcomes. Regarding intervention studies, computerized cognitive training was associated with changes in prefrontal and cerebellar activation and physical training might result in microstructural and cortical alterations. Hence, to better define the neural targets for interventions in pediatric medulloblastoma patients, this review suggests working towards neuroimaging-based predictions of cognitive outcomes. To reach this goal, large multimodal prospective imaging studies are highly recommended.

Parents' perception of their children's process of reintegration after childhood cancer treatment

Our objective was to further the understanding of the process of reintegration of childhood cancer patients after treatment and to identify factors influencing that process. Using a qualitative approach, we conducted 49 interviews with parents (n = 29 mothers, n = 20 fathers) from 31 families with a child (<18 years) with leukemia or CNS tumor. Interviews were conducted about 16 to 24 months after the end of the treatment. We used a semi-structured interview guideline and analyzed the data using content analysis. Average age of pediatric cancer patients was 5.5 years at the time of diagnosis; mean time since diagnosis was 3.5 years. Parents reported immediate impact of the disease on their children. Reintegration had gone along with delayed nursery/school enrollment or social challenges. In most cases reintegration was organized with a gradual increase of attendance. Due to exhaustion by obligatory activities, reintegration in leisure time activities was demanding and parents reported a gradual increase of activity level for their children. Parents described several barriers and facilitators influencing the reintegration process into nursery/school and leisure time activities (structural support, social support, health status, intrapersonal aspects). Although many children reintegrate well, the process takes lots of effort from parents and children. Childhood cancer survivors and their families should be supported after the end of intensive treatment to facilitate reintegration.

Neuropsychological functioning in survivors of childhood medulloblastoma/CNS-PNET: The role of secondary medical complications

OBJECTIVE

To investigate the long-term cognitive consequences of malignant pediatric brain tumor and its treatment, and factors explaining variability in cognitive functioning among survivors. Method: A geographical cohort of survivors of pediatric medulloblastoma (MB) and supratentorial primitive neuroectodermal tumor (CNS-PNET), treated between 1974 and 2013, was invited to participate. Of the 63 surviving patients, 50 (79%) consented to participation. The participants were tested with a battery of neuropsychological tests covering a wide age range. Verbal cognition, nonverbal cognition, processing speed, attention, memory, executive functioning, and manual dexterity were assessed. The participants were between 5:5 and 51:11 years of age at time of assessment. Assessments took place on average 19 years after primary tumor resective surgery. Results: One participant had a severe intellectual disability. For the rest, IQ varied from 52 to 125, with a mean score of 88.0 (SD 19.7). Twenty-eight (56%) of the participants had full-scale IQ scores in the age-average range or above. Gender, age at operation, time since operation, the presence of secondary medical complications, and treatment variables explained 46% of the variability in IQ scores, F(4,44) =  9.5, p<.001. The presence of endocrine insufficiency in combination with either epilepsy and/or hydrocephalus was associated with lowered IQ, lowered processing speed, and memory impairments. Conclusion: Patients treated for childhood MB and CNS-PNET have a lifelong risk of medical sequelae, including impaired cognitive functioning. This study adds to the literature by demonstrating the importance of following neuropsychological functioning closely, especially processing speed, learning, and memory, in survivors who have multiple secondary medical complications.

Neuroprotection of Radiosensitive Juvenile Mice by Ultra-High Dose Rate FLASH Irradiation

Major advances in high precision treatment delivery and imaging have greatly improved the tolerance of radiotherapy (RT); however, the selective sparing of normal tissue and the reduction of neurocognitive side effects from radiation-induced toxicities remain significant problems for pediatric patients with brain tumors. While the overall survival of pediatric patients afflicted with medulloblastoma (MB), the most common type primary brain cancer in children, remains high (≥80%), lifelong neurotoxic side-effects are commonplace and adversely impact patients’ quality of life. To circumvent these clinical complications, we have investigated the capability of ultra-high dose rate FLASH-radiotherapy (FLASH-RT) to protect the radiosensitive juvenile mouse brain from normal tissue toxicities. Compared to conventional dose rate (CONV) irradiation, FLASH-RT was found to ameliorate radiation-induced cognitive dysfunction in multiple independent behavioral paradigms, preserve developing and mature neurons, minimize microgliosis and limit the reduction of the plasmatic level of growth hormone. The protective “FLASH effect” was pronounced, especially since a similar whole brain dose of 8 Gy delivered with CONV-RT caused marked reductions in multiple indices of behavioral performance (objects in updated location, novel object recognition, fear extinction, light-dark box, social interaction), reductions in the number of immature (doublecortin⁺) and mature (NeuN⁺) neurons and increased neuroinflammation, adverse effects that were not found with FLASH-RT. Our data point to a potentially innovative treatment modality that is able to spare, if not prevent, many of the side effects associated with long-term treatment that disrupt the long-term cognitive and emotional well-being of medulloblastoma survivors.

Erbb4 Is Required for Cerebellar Developmentand Malignant Phenotype of Medulloblastoma

Medulloblastoma is the most common and malignant pediatric brain tumor in childhood. It originates from dysregulation of cerebellar development, due to an excessive proliferation of cerebellar granule neuron precursor cells (CGNPs). The underlying molecular mechanisms, except for the role of SHH and WNT pathways, remain largely unknown. ERBB4 is a tyrosine kinase receptor whose activity in cancer is tissue dependent. In this study, we characterized the role of ERBB4 during cerebellum development and medulloblastoma progression paying particular interests to its role in CGNPs and medulloblastoma stem cells (MBSCs). Our results show that ERBB4 is expressed in the CGNPs during cerebellum development where it plays a critical role in migration, apoptosis and differentiation. Similarly, it is enriched in the population of MBSCs, where also controls those critical processes, as well as self-renewal and tumor initiation for medulloblastoma progression. These results are translated to clinical samples where high levels of ERBB4 correlate with poor outcome in Group 4 and all medulloblastomas groups. Transcriptomic analysis identified critical processes and pathways altered in cells with knock-down of ERBB4. These results highlight the impact and underlying mechanisms of ERBB4 in critical processes during cerebellum development and medulloblastoma.

Treatment of children under 4 years of age with medulloblastoma and ependymoma in the HIT2000/HIT-REZ 2005 trials: Neuropsychological outcome 5 years after treatment

Young children with brain tumours are at high risk of developing treatment-related sequelae. We aimed to assess neuropsychological outcomes 5 years after treatment. This cross-sectional study included children under 4 years of age with medulloblastoma (MB) or ependymoma (EP) enrolled in the German brain tumour trials HIT2000 and HIT-REZ2005. Testing was performed using the validated Wuerzburg Intelligence Diagnostics (WUEP-D), which includes Kaufman-Assessment-Battery, Coloured Progressive Matrices, Visual-Motor Integration, finger tapping “Speed”, and the Continuous Performance Test. Of 104 patients in 47 centres, 72 were eligible for analyses. We assessed whether IQ was impacted by disease extent, disease location, patient age, gender, age at surgery, and treatment (chemotherapy with our without craniospinal irradiation [CSI] or local radiotherapy [LRT]). Median age at surgery was 2.3 years. Testing was performed at a median of 4.9 years after surgery. Patients with infratentorial EPs (treated with LRT) scored highest in fluid intelligence (CPM 100.9±16.9, mean±SD); second best scores were achieved by patients with MB without metastasis treated with chemotherapy alone (CPM 93.9±13.2), followed by patients with supratentorial EPs treated with LRT. In contrast, lowest scores were achieved by patients that received chemotherapy and CSI, which included children with metastasised MB and those with relapsed MB M0 (CPM 71.7±8.0 and 73.2±21.8, respectively). Fine motor skills were reduced in all groups. Multivariable analysis revealed that type of treatment had an impact on IQ, but essentially not age at surgery, time since surgery or gender. Our results confirm previous reports on the detrimental effects of CSI in a larger cohort of children. Comparable IQ scores in children with MB treated only with chemotherapy and in children with EP suggest that this treatment strategy represents an attractive option for children who have a high chance to avoid application of CSI. Longitudinal follow-up examinations are warranted to assess long-term neuropsychological outcomes.

Humanized Stem Cell Models of Pediatric Medulloblastoma Reveal an Oct4/mTOR Axis that Promotes Malignancy

Medulloblastoma (MB), the most frequent malignant childhood brain tumor, can arise from cellular malfunctions during hindbrain development. Here we generate humanized models for Sonic Hedgehog (SHH)-subgroup MB via MYCN overexpression in primary human hindbrain-derived neuroepithelial stem (hbNES) cells or iPSC-derived NES cells, which display a range of aggressive phenotypes upon xenografting. iPSC-derived NES tumors develop quickly with leptomeningeal dissemination, whereas hbNES-derived cells exhibit delayed tumor formation with less dissemination. Methylation and expression profiling show that tumors from both origins recapitulate hallmarks of infant SHH MB and reveal that mTOR activation, as a result of increased Oct4, promotes aggressiveness of human SHH tumors. Targeting mTOR decreases cell viability and prolongs survival, showing the utility of these varied models for dissecting mechanisms mediating tumor aggression and demonstrating the value of humanized models for a better understanding of pediatric cancers.

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Human iPSC-derived or primary neuroepithelial stem cells can be transformed by MYCN

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MYCN drives infant SHH medulloblastoma with clinically relevant features

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Epigenetically regulated Oct4 promotes mTOR hyperactivation in infant SHH tumors

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mTOR inhibition efficiently targets metastatic SHH medulloblastoma models and PDXs

Intelligence and posterior fossa tumors in Brazilian youth

Central nervous system tumors are the most frequent solid neoplasms in childhood and are frequently located in posterior fossa (PF). In Brazil, this diagnosis is associated to high mortality rates and this context is increasingly worrisome outside of large urban centers in which delayed diagnosis and defaulting from treatment compromise survivorship. Moreover, the lesion and therapeutic toxicity compromise cognitive domains. This study investigated the impact of PF tumors and their treatments on the intellectual capacity of 37 children and adolescents aged 6 to 16, divided into two groups: patients with low grade tumors, submitted only to neurosurgery (G1) and with tumors of higher malignancy submitted to neurosurgery, chemotherapy, and/or radiotherapy (G2). Using the Wechsler Intelligence Scales for Children, data reveal that G1 presented preserved mean performance, while G2 presented low average performance. Cluster-type analysis divided the participants into two groups regarding intelligence, clinical and sociodemographic variables. Inferential statistical analysis highlighted the influence of antineoplastic treatment on nonverbal domains. Mother's schooling demonstrated influence on verbal domains, revealing an important dissociation pattern. The results suggest the relevance of sociocultural factors on the expression of the damage, as well as the administration of radiotherapy at critical neurodevelopmental stages.

Geometrical structures for radiation biology research as implemented in the TOPAS-nBio toolkit

Computational simulations, such as Monte Carlo track structure simulations, offer a powerful tool for quantitatively investigating radiation interactions within cells. The modelling of the spatial distribution of energy deposition events as well as diffusion of chemical free radical species, within realistic biological geometries, can help provide a comprehensive understanding of the effects of radiation on cells. Track structure simulations, however, generally require advanced computing skills to implement. The TOPAS-nBio toolkit, an extension to TOPAS (TOol for PArticle Simulation), aims to provide users with a comprehensive framework for radiobiology simulations, without the need for advanced computing skills. This includes providing users with an extensive library of advanced, realistic, biological geometries ranging from the micrometer scale (e.g. cells and organelles) down to the nanometer scale (e.g. DNA molecules and proteins). Here we present the geometries available in TOPAS-nBio.

Targeting mTOR as a Therapeutic Approach in Medulloblastoma

Mechanistic target of rapamycin (mTOR) is a master signaling pathway that regulates organismal growth and homeostasis, because of its implication in protein and lipid synthesis, and in the control of the cell cycle and the cellular metabolism. Moreover, it is necessary in cerebellar development and stem cell pluripotency maintenance. Its deregulation has been implicated in the medulloblastoma and in medulloblastoma stem cells (MBSCs). Medulloblastoma is the most common malignant solid tumor in childhood. The current therapies have improved the overall survival but they carry serious side effects, such as permanent neurological sequelae and disability. Recent studies have given rise to a new molecular classification of the subgroups of medulloblastoma, specifying 12 different subtypes containing novel potential therapeutic targets. In this review we propose the targeting of mTOR, in combination with current therapies, as a promising novel therapeutic approach.

Neuropsychological consequences of childhood medulloblastoma and possible interventions: A review

BACKGROUND

Children who have been treated for a medulloblastoma often suffer long-term cognitive impairments that often negatively affect their academic performance and quality of life. In this article, we will review the neuropsychological consequences of childhood medulloblastoma and discuss the risk factors known to influence the presence and severity of these cognitive impairments and possible interventions to improve their quality of life.

METHODS

This narrative review was based on electronic searches of PubMed to identify all relevant studies.

RESULTS

Although many types of cognitive impairments often emerge during a child's subsequent development, the core cognitive domains that are most often affected in children treated for a medulloblastoma are processing speed, attention and working memory. The emergence and magnitude of these deficits varies greatly among patients. They are influenced by demographic (age at diagnosis, parental education), medical and treatment-related factors (perioperative complications, including posterior fossa syndrome, radiation therapy dose, etc.), and the quality of interventions such as school adaptations provided to the child or rehabilitation programs that focus on cognitive skills, behavior and psychosocial functioning.

CONCLUSION

These patients require specialized and coordinated multidisciplinary rehabilitation follow-up that provides timely and adapted assessments and culminates in personalized intervention goals being set with the patient and the family. Follow-up should be continued until referral to adult services.

Longitudinal changes in gray matter regions after cranial radiation and comparative analysis with whole body radiation: a DTI study

PURPOSE

Radiation-induced white matter changes are well known and vastly studied. However, radiation-induced gray matter alterations are still a research question. In the present study, these changes were assessed in a longitudinal manner using Diffusion Tensor Imaging (DTI) and further compared for cranial and whole body radiation exposure.

MATERIALS AND METHODS

Male mice (C57BL/6) were irradiated with cranial or whole body radiation followed by DTI study at 7T animal MRI system during predose, subacute and early delayed phases of radiation sickness. Fractional anisotropy (FA) and mean diffusivity (MD) values were obtained from brain's gray matter regions.

RESULTS

Decreased FA with increased MD was observed prominently in animals exposed to cranial radiation showing most changes at 8 months post irradiation. However, whole body radiation induced FA changes were mostly observed at 1 month post irradiation as compared to controls.

CONCLUSIONS

The differential response after whole body and cranial irradiation observed in the study depicts that radiation exposure of 5 Gy could induce permanent alterations in gray matter regions prominently as observed in Caudoputamen region at all the time points. Thus, our study has bolstered the role of DTI to probe microstructural changes in gray matter regions of brain after radiation exposure.

Stochastic Modeling of Radiation-induced Dendritic Damage on in silico Mouse Hippocampal Neurons

Cognitive dysfunction associated with radiotherapy for cancer treatment has been correlated to several factors, one of which is changes to the dendritic morphology of neuronal cells. Alterations in dendritic geometry and branching patterns are often accompanied by deficits that impact learning and memory. The purpose of this study is to develop a novel predictive model of neuronal dendritic damages caused by exposure to low linear energy transfer (LET) radiation, such as X-rays, γ-rays and high-energy protons. We established in silico representations of mouse hippocampal dentate granule cell layer (GCL) and CA1 pyramidal neurons, which are frequently examined in radiation-induced cognitive decrements. The in silico representations are used in a stochastic model that describes time dependent dendritic damage induced by exposure to low LET radiation. Changes in morphometric parameters, such as total dendritic length, number of branch points and branch number, including the Sholl analysis for single neurons are described by the model. Our model based predictions for different patterns of morphological changes based on energy deposition in dendritic segments (EDDS) will serve as a useful basis to compare specific patterns of morphological alterations caused by EDDS mechanisms.

Impact of attention on social functioning in pediatric medulloblastoma survivors

BACKGROUND

Parent-reported attention problems have been associated with social functioning in a broad sample of pediatric cancer survivors.

OBJECTIVE

The present study focused on a more homogeneous sample (pediatric medulloblastoma survivors), with the novel inclusion of self-reported attention ratings.

PARTICIPANTS/METHODS

Thirty-three pediatric medulloblastoma survivors, ages 7-18 years, completed a brief IQ measure and self-report of attentional and social functioning. Parents rated patients' attentional and social functioning.

RESULTS

Mean attention ratings were average based on both parent- and self-report, though parent ratings were significantly discrepant from normative means. No significant demographic or treatment-related predictors of self-reported attention problems were identified, whereas female gender was associated with greater parent-reported attention problems. Canonical correlation analysis revealed a significant association between parent-reported attention difficulties and social functioning in pediatric medulloblastoma survivors, but there was no association between self-reported attention problems and measures of social functioning.

CONCLUSIONS

Consistent with existing literature in broader samples of pediatric cancer survivors, the present study further affirms attention deficits as an underlying contributor to social deficits in pediatric medulloblastoma survivors while also finding little relationship between self-reports of attention and social performance. Notably, present findings provide additional support suggesting that attention functioning is a more significant contributor to social outcomes for pediatric medulloblastoma survivors than the level of cognitive ability.

Mechanisms of radiotherapy-associated cognitive disability in patients with brain tumours

Standard treatment of primary and metastatic brain tumours includes high-dose megavoltage-range radiation to the cranial vault. About half of patients survive >6 months, and many attain long-term control or cure. However, 50-90% of survivors exhibit disabling cognitive dysfunction. The radiation-associated cognitive syndrome is poorly understood and has no effective prevention or long-term treatment. Attention has primarily focused on mechanisms of disability that appear at 6 months to 1 year after radiotherapy. However, recent studies show that CNS alterations and dysfunction develop much earlier following radiation exposure. This finding has prompted the hypothesis that subtle early forms of radiation-induced CNS damage could drive chronic pathophysiological processes that lead to permanent cognitive decline. This Review presents evidence of acute radiation-triggered CNS inflammation, injury to neuronal lineages, accessory cells and their progenitors, and loss of supporting structure integrity. Moreover, injury-related processes initiated soon after irradiation could synergistically alter the signalling microenvironment in progenitor cell niches in the brain and the hippocampus, which is a structure critical to memory and cognition. Progenitor cell niche degradation could cause progressive neuronal loss and cognitive disability. The concluding discussion addresses future directions and potential early treatments that might reverse degenerative processes before they can cause permanent cognitive disability.

Measurement of neurodevelopmental changes in children treated with radiation for brain tumors: what is a true 'baseline?'

OBJECTIVE

To review the various ways in which baseline neuropsychological functioning is measured in the extant literature on pediatric brain tumors, describe the pros and cons of each approach, and increase the awareness of researchers as to the implications of each.

METHOD

We reviewed the literature from 1993 to 2013, and classified studies by baseline approach and explicitness of selection of approach.

RESULTS

There are multiple approaches to operationalizing baseline levels of ability and to assess change from baseline. Each approach has strengths and weaknesses, and selection may depend on the question under investigation. Approaches to baseline estimation varied widely with a trend over time toward reliance on statistical modeling. Researchers were often insufficiently explicit about the reasons for adopting a particular approach. The common use of standardized scores requires caution as they obscure critical inferential limitations about change and magnitude of change. Some viable approaches were infrequently used, such as actuarial prediction formulas. Multiple simultaneous methods akin to theory testing and formal methods of construct validation could enhance scientific yield since all approaches are fallible.

CONCLUSIONS

Estimating baseline neuropsychological functioning is very challenging, particularly when it concerns children in the preschool years. Nevertheless, it is a crucial methodological decision with important implications for the interpretation of research findings that needs to be dealt with explicitly.

HDAC and PI3K Antagonists Cooperate to Inhibit Growth of MYC-Driven Medulloblastoma

Medulloblastoma (MB) is a highly malignant pediatric brain tumor. Despite aggressive therapy, many patients succumb to the disease, and survivors experience severe side effects from treatment. MYC-driven MB has a particularly poor prognosis and would greatly benefit from more effective therapies. We used an animal model of MYC-driven MB to screen for drugs that decrease viability of tumor cells. Among the most effective compounds were histone deacetylase inhibitors (HDACIs). HDACIs potently inhibit survival of MYC-driven MB cells in vitro, in part by inducing expression of the FOXO1 tumor suppressor gene. HDACIs also synergize with phosphatidylinositol 3-kinase inhibitors to inhibit tumor growth in vivo. These studies identify an effective combination therapy for the most aggressive form of MB.

Psychosocial profile of pediatric brain tumor survivors with neurocognitive complaints

PURPOSE

With more children surviving a brain tumor, neurocognitive consequences of the tumor and its treatment become apparent, which could affect psychosocial functioning. The present study therefore aimed to assess psychosocial functioning of pediatric brain tumor survivors (PBTS) in detail.

METHODS

Psychosocial functioning of PBTS (8-18 years) with parent-reported neurocognitive complaints was compared to normative data on health-related quality of life (HRQOL), self-esteem, psychosocial adjustment, and executive functioning (one-sample t tests) and to a sibling control group on fatigue (independent-samples t test). Self-, parent-, and teacher-report questionnaires were included, where appropriate, providing complementary information.

RESULTS

Eighty-two PBTS (mean age 13.4 years, SD 3.2, 49 % males) and 43 healthy siblings (mean age 14.3, SD 2.4, 40 % males) were included. As compared to the normative population, PBTS themselves reported decreased physical, psychological, and generic HRQOL (d = 0.39-0.62, p < 0.008). Compared to siblings, increased fatigue-related concentration problems (d = 0.57, p < 0.01) were reported, although self-reported self-esteem and psychosocial adjustment seemed not to be affected. Parents of PBTS reported more psychosocial (d = 0.81, p < 0.000) and executive problems (d = 0.35-0.43, p < 0.016) in their child than parents of children in the normative population. Teachers indicated more psychosocial adjustment problems for female PBTS aged 8-11 years than for the female normative population (d = 0.69, p < 0.025), but they reported no more executive problems.

CONCLUSIONS

PBTS with parent-reported neurocognitive complaints showed increased psychosocial problems, as reported by PBTS, parents, and teachers.

IMPLICATIONS FOR CANCER SURVIVORS

Systematic screening of psychosocial functioning is necessary so that tailored support from professionals can be offered to PBTS with neurocognitive complaints.

Stem cell transplantation reverses chemotherapy-induced cognitive dysfunction

The frequent use of chemotherapy to combat a range of malignancies can elicit severe cognitive dysfunction often referred to as "chemobrain," a condition that can persist long after the cessation of treatment in as many as 75% of survivors. Although cognitive health is a critical determinant of therapeutic outcome, chemobrain remains an unmet medical need that adversely affects quality of life in pediatric and adult cancer survivors. Using a rodent model of chemobrain, we showed that chronic cyclophosphamide treatment induced significant performance-based decrements on behavioral tasks designed to interrogate hippocampal and cortical function. Intrahippocampal transplantation of human neural stem cells resolved all cognitive impairments when animals were tested 1 month after the cessation of chemotherapy. In transplanted animals, grafted cells survived (8%) and differentiated along neuronal and astroglial lineages, where improved cognition was associated with reduced neuroinflammation and enhanced host dendritic arborization. Stem cell transplantation significantly reduced the number of activated microglia after cyclophosphamide treatment in the brain. Granule and pyramidal cell neurons within the dentate gyrus and CA1 subfields of the hippocampus exhibited significant reductions in dendritic complexity, spine density, and immature and mature spine types following chemotherapy, adverse effects that were eradicated by stem cell transplantation. Our findings provide the first evidence that cranial transplantation of stem cells can reverse the deleterious effects of chemobrain, through a trophic support mechanism involving the attenuation of neuroinflammation and the preservation host neuronal architecture.

Executive function late effects in survivors of pediatric brain tumors and acute lymphoblastic leukemia

BACKGROUND

Survivors of pediatric brain tumors (BT) and acute lymphoblastic leukemia (ALL) are at risk for neurocognitive late effects related to executive function.

PROCEDURE

Survivors of BT (48) and ALL (50) completed neurocognitive assessment. Executive function was compared to estimated IQ and population norms by diagnostic group.

RESULTS

Both BT and ALL demonstrated relative executive function weaknesses. As a group, BT survivors demonstrated weaker executive functioning than expected for age. Those BT survivors with deficits exhibited a profile suggestive of global executive dysfunction, while affected ALL survivors tended to demonstrate specific rapid naming deficits.

CONCLUSION

Findings suggest that pediatric BT and ALL survivors may exhibit different profiles of executive function late effects, which may necessitate distinct intervention plans.

Stem cell therapies for the treatment of radiation-induced normal tissue side effects

SIGNIFICANCE

Targeted irradiation is an effective cancer therapy but damage inflicted to normal tissues surrounding the tumor may cause severe complications. While certain pharmacologic strategies can temper the adverse effects of irradiation, stem cell therapies provide unique opportunities for restoring functionality to the irradiated tissue bed.

RECENT ADVANCES

Preclinical studies presented in this review provide encouraging proof of concept regarding the therapeutic potential of stem cells for treating the adverse side effects associated with radiotherapy in different organs. Early-stage clinical data for radiation-induced lung, bone, and skin complications are promising and highlight the importance of selecting the appropriate stem cell type to stimulate tissue regeneration.

CRITICAL ISSUES

While therapeutic efficacy has been demonstrated in a variety of animal models and human trials, a range of additional concerns regarding stem cell transplantation for ameliorating radiation-induced normal tissue sequelae remain. Safety issues regarding teratoma formation, disease progression, and genomic stability along with technical issues impacting disease targeting, immunorejection, and clinical scale-up are factors bearing on the eventual translation of stem cell therapies into routine clinical practice.

FUTURE DIRECTIONS

Follow-up studies will need to identify the best possible stem cell types for the treatment of early and late radiation-induced normal tissue injury. Additional work should seek to optimize cellular dosing regimes, identify the best routes of administration, elucidate optimal transplantation windows for introducing cells into more receptive host tissues, and improve immune tolerance for longer-term engrafted cell survival into the irradiated microenvironment.

Persistent changes in neuronal structure and synaptic plasticity caused by proton irradiation

Cranial radiotherapy is used routinely to control the growth of primary and secondary brain tumors, but often results in serious and debilitating cognitive dysfunction. In part due to the beneficial dose depth distributions that may spare normal tissue damage, the use of protons to treat CNS and other tumor types is rapidly gaining popularity. Astronauts exposed to lower doses of protons in the space radiation environment are also at risk for developing adverse CNS complications. To explore the consequences of whole body proton irradiation, mice were subjected to 0.1 and 1 Gy and analyzed for morphometric changes in hippocampal neurons 10 and 30 days following exposure. Significant dose-dependent reductions (~33 %) in dendritic complexity were found, when dendritic length, branching and area were analyzed 30 days after exposure. At equivalent doses and times, significant reductions in the number (~30 %) and density (50-75 %) of dendritic spines along hippocampal neurons of the dentate gyrus were also observed. Immature spines (filopodia, long) exhibited the greatest sensitivity (1.5- to 3-fold) to irradiation, while more mature spines (mushroom) were more resistant to changes over a 1-month post-irradiation timeframe. Irradiated granule cell neurons spanning the subfields of the dentate gyrus showed significant and dose-responsive reductions in synaptophysin expression, while the expression of postsynaptic density protein (PSD-95) was increased significantly. These findings corroborate our past work using photon irradiation, and demonstrate for the first time, dose-responsive changes in dendritic complexity, spine density and morphology and synaptic protein levels following exposure to low-dose whole body proton irradiation.

Engineered knottin peptide enables noninvasive optical imaging of intracranial medulloblastoma

Central nervous system tumors carry grave clinical prognoses due to limited effectiveness of surgical resection, radiation, and chemotherapy. Thus, improved strategies for brain tumor visualization and targeted treatment are critically needed. We demonstrate that mouse cerebellar medulloblastoma (MB) can be targeted and illuminated with a fluorescent, engineered cystine knot (knottin) peptide that binds with high affinity to αvβ3, αvβ5, and α5β1 integrin receptors. This integrin-binding knottin peptide, denoted EETI 2.5F, was evaluated as a molecular imaging probe in both orthotopic and genetic models of MB. Following tail vein injection, fluorescence arising from dye-conjugated EETI 2.5F was localized to the tumor compared with the normal surrounding brain tissue, as measured by optical imaging. The imaging signal intensity correlated with tumor volume. Due to its unique ability to bind to α5β1 integrin, EETI 2.5F showed superior in vivo and ex vivo brain tumor imaging contrast compared with other engineered integrin-binding knottin peptides and with c(RGDfK), a well-studied integrin-binding peptidomimetic. Next, EETI 2.5F was fused to an antibody fragment crystallizable (Fc) domain (EETI 2.5F-Fc) to determine if a larger integrin-binding protein could also target intracranial brain tumors. EETI 2.5F-Fc, conjugated to a fluorescent dye, illuminated MB following i.v. injection and was able to distribute throughout the tumor parenchyma. In contrast, brain tumor imaging signals were not detected in mice injected with EETI 2.5F proteins containing a scrambled integrin-binding sequence, demonstrating the importance of target specificity. These results highlight the potential of using EETI 2.5F and EETI 2.5-Fc as targeted molecular probes for brain tumor imaging.

Transplantation of human fetal-derived neural stem cells improves cognitive function following cranial irradiation

Treatment of central nervous system (CNS) malignancies typically involves radiotherapy to forestall tumor growth and recurrence following surgical resection. Despite the many benefits of cranial radiotherapy, survivors often suffer from a wide range of debilitating and progressive cognitive deficits. Thus, while patients afflicted with primary and secondary malignancies of the CNS now experience longer local regional control and progression-free survival, there remains no clinical recourse for the unintended neurocognitive sequelae associated with their cancer treatments. Multiple mechanisms contribute to disrupted cognition following irradiation, including the depletion of radiosensitive populations of stem and progenitor cells in the hippocampus. We have explored the potential of using intrahippocampal transplantation of human stem cells to ameliorate radiation-induced cognitive dysfunction. Past studies demonstrated the capability of cranially transplanted human embryonic (hESCs) and neural (hNSCs) stem cells to functionally restore cognition in rats 1 and 4 months after cranial irradiation. The present study employed an FDA-approved fetal-derived hNSC line capable of large scale-up under good manufacturing practice (GMP). Animals receiving cranial transplantation of these cells 1 month following irradiation showed improved hippocampal spatial memory and contextual fear conditioning performance compared to irradiated, sham surgery controls. Significant newly born (doublecortin positive) neurons and a smaller fraction of glial subtypes were observed within and nearby the transplantation core. Engrafted cells migrated and differentiated into neuronal and glial subtypes throughout the CA1 and CA3 subfields of the host hippocampus. These studies expand our prior findings to demonstrate that transplantation of fetal-derived hNSCs improves cognitive deficits in irradiated animals, as assessed by two separate cognitive tasks.

Cranial irradiation compromises neuronal architecture in the hippocampus

Cranial irradiation is used routinely for the treatment of nearly all brain tumors, but may lead to progressive and debilitating impairments of cognitive function. Changes in synaptic plasticity underlie many neurodegenerative conditions that correlate to specific structural alterations in neurons that are believed to be morphologic determinants of learning and memory. To determine whether changes in dendritic architecture might underlie the neurocognitive sequelae found after irradiation, we investigated the impact of cranial irradiation (1 and 10 Gy) on a range of micromorphometric parameters in mice 10 and 30 d following exposure. Our data revealed significant reductions in dendritic complexity, where dendritic branching, length, and area were routinely reduced (>50%) in a dose-dependent manner. At these same doses and times we found significant reductions in the number (20-35%) and density (40-70%) of dendritic spines on hippocampal neurons of the dentate gyrus. Interestingly, immature filopodia showed the greatest sensitivity to irradiation compared with more mature spine morphologies, with reductions of 43% and 73% found 30 d after 1 and 10 Gy, respectively. Analysis of granule-cell neurons spanning the subfields of the dentate gyrus revealed significant reductions in synaptophysin expression at presynaptic sites in the dentate hilus, and significant increases in postsynaptic density protein (PSD-95) were found along dendrites in the granule cell and molecular layers. These findings are unique in demonstrating dose-responsive changes in dendritic complexity, synaptic protein levels, spine density and morphology, alterations induced in hippocampal neurons by irradiation that persist for at least 1 mo, and that resemble similar types of changes found in many neurodegenerative conditions.

Neurocognitive consequences of a paediatric brain tumour and its treatment: a meta-analysis

AIM

This meta-analysis provides a systematic review of studies into intellectual and attentional functioning of paediatric brain tumour survivors (PBTS) as assessed by two widely used measures: the Wechsler Intelligence Scale for Children (3rd edition; WISC-III) and the Conners' Continuous Performance Test (CPT).

METHOD

Studies were located that reported on performance of PBTS (age range 6-16y). Meta-analytic effect sizes were calculated for Full-scale IQ, Performance IQ, and Verbal IQ as measured by the WISC-III, and mean hit reaction time, errors of omission, and errors of commission as measured by the CPT. Exploratory analyses investigated the possible impacts of treatment mode, tumour location, age at diagnosis, and time since diagnosis on intelligence.

RESULTS

Twenty-nine studies were included: 22 reported on the WISC-III in 710 PBTS and seven on CPT results in 372 PBTS. PBTS performed below average (p(s) <0.001) on Full-scale IQ (Cohen's d=-0.79), Performance IQ (d=-0.90), and Verbal IQ (d=-0.54). PBTS committed more errors of omission than the norm (d=0.82, p<0.001); no differences were found for mean hit reaction time and errors of commission. Cranial radiotherapy, chemotherapy, and longer time since diagnosis were associated with lower WISC-III scores (p(s) <0.05).

INTERPRETATION

PBTS have seriously impaired intellectual functioning and attentiveness. Being treated with cranial radiotherapy and/or chemotherapy as well as longer time since diagnosis leads to worse intellectual functioning.

Health-related quality of life and cognitive functioning at on- and off-treatment periods in children aged between 6-13 years old with brain tumors: a prospective longitudinal study

PURPOSE

Our study aimed to examine the relationship between intelligence and health-related quality of life (HRQOL) in children (6-13 years old) diagnosed as having a brain tumor.

MATERIALS AND METHODS

We administered a Korean version of the Wechsler Intelligence Scale for Children-III, the Pediatric Quality of Life Inventory, version 4.0 (PedsQL), the Korean version of the Parenting Stress Index-Short Form, and the Korean Version of the Parenting Sense of Competence (K-PSOC) scale before or after initial radiotherapy (T1) and after treatment termination (T2). In total, 13 patients completed both the T1 and T2 interviews.

RESULTS

Scores significantly declined between T1 and T2 on the full-scale intelligence quotients (FIQ), verbal intelligence quotients (VIQ), performance intelligence quotients (PIQ), similarity and coding tests, as well as the K-PSOC, which measures parental anxiety. FIQ scores at T1 were correlated with the self-reported PedsQL total scores (r=0.739) and the parent proxy-report PedsQL scores for school functioning (r=0.706) at T2. Also, the FIQ scores at T2 were correlated with the self-reported PedsQL total scores (r=0.748) and scores for physical health (r=0.728) at T2.

CONCLUSION

The cognitive ability and intelligence level of the patients significantly declined between on and off treatment periods, and higher intelligence functioning at both on and off treatment was correlated with long-term higher HRQOL. Further investigations that monitor intelligence, HRQOL and parenting stress over a longer period, using a greater number of participants, are needed.

Treatment of medulloblastoma using an oncolytic measles virus encoding the thyroidal sodium iodide symporter shows enhanced efficacy with radioiodine

Background

Medulloblastoma is the most common malignant brain tumor of childhood. Although the clinical outcome for medulloblastoma patients has improved significantly, children afflicted with the disease frequently suffer from debilitating side effects related to the aggressive nature of currently available therapy. Alternative means for treating medulloblastoma are desperately needed. We have previously shown that oncolytic measles virus (MV) can selectively target and destroy medulloblastoma tumor cells in localized and disseminated models of the disease. MV-NIS, an oncolytic measles virus that encodes the human thyroidal sodium iodide symporter (NIS), has the potential to deliver targeted radiotherapy to the tumor site and promote a localized bystander effect above and beyond that achieved by MV alone.

Methods

We evaluated the efficacy of MV-NIS against medulloblastoma cells in vitro and examined their ability to incorporate radioiodine at various timepoints, finding peak uptake at 48 hours post infection. The effects of MV-NIS were also evaluated in mouse xenograft models of localized and disseminated medulloblastoma. Athymic nude mice were injected with D283med-Luc medulloblastoma cells in the caudate putamen (localized disease) or right lateral ventricle (disseminated disease) and subsequently treated with MV-NIS. Subsets of these mice were given a dose of ¹³¹I at 24, 48 or 72 hours later.

Results

MV-NIS treatment, both by itself and in combination with ¹³¹I, elicited tumor stabilization and regression in the treated mice and significantly extended their survival times. Mice given ¹³¹I were found to concentrate radioiodine at the site of their tumor implantations. In addition, mice with localized tumors that were given ¹³¹I either 24 or 48 hours after MV-NIS treatment exhibited a significant survival advantage over mice given MV-NIS alone.

Conclusions

These data suggest MV-NIS plus radioiodine may be a potentially useful therapy for the treatment of medulloblastoma.

A distinct Smoothened mutation causes severe cerebellar developmental defects and medulloblastoma in a novel transgenic mouse model

Deregulated developmental processes in the cerebellum cause medulloblastoma, the most common pediatric brain malignancy. About 25 to 30% of cases are caused by mutations increasing the activity of the Sonic hedgehog (Shh) pathway, a critical mitogen in cerebellar development. The proto-oncogene Smoothened (Smo) is a key transducer of the Shh pathway. Activating mutations in Smo that lead to constitutive activity of the Shh pathway have been identified in human medulloblastoma. To understand the developmental and oncogenic effects of two closely positioned point mutations in Smo, we characterized NeuroD2-SmoA2 mice and compared them to NeuroD2-SmoA1 mice. While both SmoA1 and SmoA2 transgenes cause medulloblastoma with similar frequencies and timing, SmoA2 mice have severe aberrations in cerebellar development, whereas SmoA1 mice are largely normal during development. Intriguingly, neurologic function, as measured by specific tests, is normal in the SmoA2 mice despite extensive cerebellar dysplasia. We demonstrate how two nearly contiguous point mutations in the same domain of the encoded Smo protein can produce striking phenotypic differences in cerebellar development and organization in mice.

VMY-1-103 is a novel CDK inhibitor that disrupts chromosome organization and delays metaphase progression in medulloblastoma cells

Medulloblastoma is the most prevalent of childhood brain malignancies, constituting 25% of childhood brain tumors. Craniospinal radiotherapy is a standard of care, followed by a 12mo regimen of multi-agent chemotherapy. For children less than 3 y of age, irradiation is avoided due to its destructive effects on the developing nervous system. Long-term prognosis is worst for these youngest children and more effective treatment strategies with a better therapeutic index are needed. VMY-1-103, a novel dansylated analog of purvalanol B, was previously shown to inhibit cell cycle progression and proliferation in prostate and breast cancer cells more effectively than purvalanol B. In the current study, we have identified new mechanisms of action by which VMY-1-103 affected cellular proliferation in medulloblastoma cells. VMY-1-103, but not purvalanol B, significantly decreased the proportion of cells in S phase and increased the proportion of cells in G(2)/M. VMY-1-103 increased the sub G(1) fraction of apoptotic cells, induced PARP and caspase-3 cleavage and increased the levels of the Death Receptors DR4 and DR5, Bax and Bad while decreasing the number of viable cells, all supporting apoptosis as a mechanism of cell death. p21(CIP1/WAF1) levels were greatly suppressed. Importantly, we found that while both VMY and flavopiridol inhibited intracellular CDK1 catalytic activity, VMY-1-103 was unique in its ability to severely disrupt the mitotic spindle apparatus significantly delaying metaphase and disrupting mitosis. Our data suggest that VMY-1-103 possesses unique antiproliferative capabilities and that this compound may form the basis of a new candidate drug to treat medulloblastoma.