Failure of human rhombic lip differentiation underlies medulloblastoma formation

Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hindbrain with strong links to early development of the hindbrain^1-4. Mutations that activate Sonic hedgehog signalling lead to Sonic hedgehog MB in the upper rhombic lip (RL) granule cell lineage^5-8. By contrast, mutations that activate WNT signalling lead to WNT MB in the lower RL^9,10. However, little is known about the more commonly occurring group 4 (G4) MB, which is thought to arise in the unipolar brush cell lineage^3,4. Here we demonstrate that somatic mutations that cause G4 MB converge on the core binding factor alpha (CBFA) complex and mutually exclusive alterations that affect CBFA2T2, CBFA2T3, PRDM6, UTX and OTX2. CBFA2T2 is expressed early in the progenitor cells of the cerebellar RL subventricular zone in Homo sapiens, and G4 MB transcriptionally resembles these progenitors but are stalled in developmental time. Knockdown of OTX2 in model systems relieves this differentiation blockade, which allows MB cells to spontaneously proceed along normal developmental differentiation trajectories. The specific nature of the split human RL, which is destined to generate most of the neurons in the human brain, and its high level of susceptible EOMES⁺KI67⁺ unipolar brush cell progenitor cells probably predisposes our species to the development of G4 MB.

Effective Immunotherapy of Glioblastoma in an Adolescent with Constitutional Mismatch Repair-Deficiency Syndrome

BACKGROUND

Individuals with constitutional mismatch repair-deficiency syndrome (CMMR-D) are characterised by early occurrence of colon cancer, haematological malignancies, and brain tumors (malignant gliomas, high-grade gliomas) in childhood, adolescence, and early adulthood. High mutational tumor burden is typical of glioblastoma in CMMR-D patients and could be a reason why this type of glioblastoma responds well to immunotherapies, including those that employ checkpoint inhibitors.

OBSERVATION

We describe a case of an adolescent with CMMR-D that had been genetically proven by whole exome sequencing (c.2T>A/p.M1K and c.2521delT/p.W841fs PMS2 gene mutation). The patient presented successively with colon cancer and glioblastoma with a high mutational burden. The individualized glioblastoma therapy was based on the biological tumor profile and included immunotherapy with a combination of vaccination with autologous dendritic cells producing IL-12 and nivolumab, in addition to radiotherapy with metronomic temozolomide. The patient is still alive 21 months after the initial glioblastoma diagnosis and shows a complete therapeutic response documented by repeated magnetic resonance examinations.

CONCLUSION

Individuals with CMMR-D should be regularly examined using established algorithms. Whole body magnetic resonance imaging can play a key role, because it enables the early diagnosis of malignancy during the asymptomatic period. Malignancies in CMMR-D patients usually exhibit a hypermutated genotype and respond to immunotherapy. Conventional glioblastoma therapy is only palliative. Patients can benefit from an individualized therapeutic plan based on the tumor biological profile. Extensive molecular analysis of the tumor tissue is necessary. Key words hereditary cancer predisposition syndromes - glioblastoma - whole exome sequencing - immunotherapy - vaccines - checkpoint inhibitors This study was supported by the research project of the Czech Ministry of Health AZV 16-33209A (Next generation sequencing and express profiling as diagnostic tools for personalized therapeutic plans in children with solid tumors). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Submitted: 26. 9. 2018 Accepted: 18. 11. 2018.

Molecular Classification of Medullobastomas by Whole Genome Expression Profiling

BACKGROUND

Medulloblastoma (MB) is the most common malignant tumour of the central nervous system in children. MB is considered to be high risk tumour propensity to metastasize. In the Czech Republic, approximately 10-12 children are affected annually by this tumour. Recent progress in molecular diagnostics helps to refine the diagnosis and estimate clinical prognosis of the disease. Currently, MBs are subclassified into WNT-activated, SHH-activated, group 3, and 4 based on molecular pathways that drive their tumorigenesis. Each subtype differs in its histopathology, clinical features, genomic changes and gene expressions. The aim of our study is to classify patients MBs into four basic molecular groups and compare our results with published data.

MATERIAL AND METHODS

In our study we analysed expression profiles using Affymetrix GeneChip Human Gene 1.0. ST Array (Thermo Fisher Scientific, MA, USA). As input material RNA extracted from the fresh frozen tissue was used. Molecular classification based on the method established by P. Northcott in 2011 was performed.

RESULTS

From April 2015 to February 2019, 21 patients with MBs were included in our study. Median age of the patients at the time of diagnosis was 6 years, 14 boys and 7 girls were enrolled. Gene expression profiling and molecular classification of MBs was performed. Based on this methodology, we found the most frequently represented subgroup of MB was group 4 (9 patients, 43%), followed by group 3 (5 patients, 24%), SHH-activated MB (4 patients, 19%) and the least represented subgroup was WNT-activated MB (3 patients, 14%). Results of molecular subgroup classification of MBs were successfully correlated with histopathological findings and other molecular-genetic examinations.

CONCLUSION

Molecular classification of MBs has been established in our institution allowing better understanding of this heterogeneous disease and helping clinicians in therapeutic planning in affected patients. This work was supported by the Czech Ministry of Health grant No. 16-33209A. All rights reserved.  he authors declare they have no potential confl icts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers. Submitted: 1. 3. 2019 Accepted: 4. 3. 2019.

NEUROFIBROMATOSIS TYPE 1 AND OPTIC PATHWAY GLIOMA

PURPOSE

Evaluate the effectiveness of treatment of patients with optic pathway glioma.

MATERIALS AND METHODS

Comparison of literature research on neurofibromatosis and optic pathway glioma with a cohort of pediatric patients treated at the Childrens Ophthalmology Clinic of the University Hospital in Brno from January 2013 until June 2018.

DISCUSSION

The main challenge of this and other retrospective studies is variable intervals between ophthalmologic examinations. In some pediatric patients it is also difficult to objectively assess visual functions. The main risk factors are age at the time of treatment and tumor localization. Tumor progression itself does not always correlate with worse visual acuity outcomes, and it remains to be evaluated whether some patients would be better off without treatment. As of now, there are no clinical biomarkers able to predict impending visual acuity loss.

CONCLUSION

The cohort outcome agrees with literature. Chemotherapy remains a treatment of choice and its most likely outcome is visual acuity stabilization. In order to properly evaluate the treatments effectiveness, better collaboration between medical specialists and regular standardized ophthalmology examinations are required.

Spectrum and prevalence of genetic predisposition in medulloblastoma: a retrospective genetic study and prospective validation in a clinical trial cohort

BACKGROUND

Medulloblastoma is associated with rare hereditary cancer predisposition syndromes; however, consensus medulloblastoma predisposition genes have not been defined and screening guidelines for genetic counselling and testing for paediatric patients are not available. We aimed to assess and define these genes to provide evidence for future screening guidelines.

METHODS

In this international, multicentre study, we analysed patients with medulloblastoma from retrospective cohorts (International Cancer Genome Consortium [ICGC] PedBrain, Medulloblastoma Advanced Genomics International Consortium [MAGIC], and the CEFALO series) and from prospective cohorts from four clinical studies (SJMB03, SJMB12, SJYC07, and I-HIT-MED). Whole-genome sequences and exome sequences from blood and tumour samples were analysed for rare damaging germline mutations in cancer predisposition genes. DNA methylation profiling was done to determine consensus molecular subgroups: WNT (MBWNT), SHH (MBSHH), group 3 (MBGroup3), and group 4 (MBGroup4). Medulloblastoma predisposition genes were predicted on the basis of rare variant burden tests against controls without a cancer diagnosis from the Exome Aggregation Consortium (ExAC). Previously defined somatic mutational signatures were used to further classify medulloblastoma genomes into two groups, a clock-like group (signatures 1 and 5) and a homologous recombination repair deficiency-like group (signatures 3 and 8), and chromothripsis was investigated using previously established criteria. Progression-free survival and overall survival were modelled for patients with a genetic predisposition to medulloblastoma.

FINDINGS

We included a total of 1022 patients with medulloblastoma from the retrospective cohorts (n=673) and the four prospective studies (n=349), from whom blood samples (n=1022) and tumour samples (n=800) were analysed for germline mutations in 110 cancer predisposition genes. In our rare variant burden analysis, we compared these against 53 105 sequenced controls from ExAC and identified APC, BRCA2, PALB2, PTCH1, SUFU, and TP53 as consensus medulloblastoma predisposition genes according to our rare variant burden analysis and estimated that germline mutations accounted for 6% of medulloblastoma diagnoses in the retrospective cohort. The prevalence of genetic predispositions differed between molecular subgroups in the retrospective cohort and was highest for patients in the MBSHH subgroup (20% in the retrospective cohort). These estimates were replicated in the prospective clinical cohort (germline mutations accounted for 5% of medulloblastoma diagnoses, with the highest prevalence [14%] in the MBSHH subgroup). Patients with germline APC mutations developed MBWNT and accounted for most (five [71%] of seven) cases of MBWNT that had no somatic CTNNB1 exon 3 mutations. Patients with germline mutations in SUFU and PTCH1 mostly developed infant MBSHH. Germline TP53 mutations presented only in childhood patients in the MBSHH subgroup and explained more than half (eight [57%] of 14) of all chromothripsis events in this subgroup. Germline mutations in PALB2 and BRCA2 were observed across the MBSHH, MBGroup3, and MBGroup4 molecular subgroups and were associated with mutational signatures typical of homologous recombination repair deficiency. In patients with a genetic predisposition to medulloblastoma, 5-year progression-free survival was 52% (95% CI 40-69) and 5-year overall survival was 65% (95% CI 52-81); these survival estimates differed significantly across patients with germline mutations in different medulloblastoma predisposition genes.

INTERPRETATION

Genetic counselling and testing should be used as a standard-of-care procedure in patients with MBWNT and MBSHH because these patients have the highest prevalence of damaging germline mutations in known cancer predisposition genes. We propose criteria for routine genetic screening for patients with medulloblastoma based on clinical and molecular tumour characteristics.

FUNDING

German Cancer Aid; German Federal Ministry of Education and Research; German Childhood Cancer Foundation (Deutsche Kinderkrebsstiftung); European Research Council; National Institutes of Health; Canadian Institutes for Health Research; German Cancer Research Center; St Jude Comprehensive Cancer Center; American Lebanese Syrian Associated Charities; Swiss National Science Foundation; European Molecular Biology Organization; Cancer Research UK; Hertie Foundation; Alexander and Margaret Stewart Trust; V Foundation for Cancer Research; Sontag Foundation; Musicians Against Childhood Cancer; BC Cancer Foundation; Swedish Council for Health, Working Life and Welfare; Swedish Research Council; Swedish Cancer Society; the Swedish Radiation Protection Authority; Danish Strategic Research Council; Swiss Federal Office of Public Health; Swiss Research Foundation on Mobile Communication; Masaryk University; Ministry of Health of the Czech Republic; Research Council of Norway; Genome Canada; Genome BC; Terry Fox Research Institute; Ontario Institute for Cancer Research; Pediatric Oncology Group of Ontario; The Family of Kathleen Lorette and the Clark H Smith Brain Tumour Centre; Montreal Children's Hospital Foundation; The Hospital for Sick Children: Sonia and Arthur Labatt Brain Tumour Research Centre, Chief of Research Fund, Cancer Genetics Program, Garron Family Cancer Centre, MDT's Garron Family Endowment; BC Childhood Cancer Parents Association; Cure Search Foundation; Pediatric Brain Tumor Foundation; Brainchild; and the Government of Ontario.

Intertumoral Heterogeneity within Medulloblastoma Subgroups

While molecular subgrouping has revolutionized medulloblastoma classification, the extent of heterogeneity within subgroups is unknown. Similarity network fusion (SNF) applied to genome-wide DNA methylation and gene expression data across 763 primary samples identifies very homogeneous clusters of patients, supporting the presence of medulloblastoma subtypes. After integration of somatic copy-number alterations, and clinical features specific to each cluster, we identify 12 different subtypes of medulloblastoma. Integrative analysis using SNF further delineates group 3 from group 4 medulloblastoma, which is not as readily apparent through analyses of individual data types. Two clear subtypes of infants with Sonic Hedgehog medulloblastoma with disparate outcomes and biology are identified. Medulloblastoma subtypes identified through integrative clustering have important implications for stratification of future clinical trials.

Uniformity under in vitro conditions: Changes in the phenotype of cancer cell lines derived from different medulloblastoma subgroups

Medulloblastoma comprises four main subgroups (WNT, SHH, Group 3 and Group 4) originally defined by transcriptional profiling. In primary medulloblastoma tissues, these groups are thought to be distinguishable using the immunohistochemical detection of β-catenin, filamin A, GAB1 and YAP1 protein markers. To investigate the utility of these markers for in vitro studies using medulloblastoma cell lines, immunoblotting and indirect immunofluorescence were employed for the detection of β-catenin, filamin A, GAB1 and YAP1 in both DAOY and D283 Med reference cell lines and the panel of six medulloblastoma cell lines derived in our laboratory from the primary tumor tissues of known molecular subgroups. Immunohistochemical detection of these markers was performed on formalin-fixed paraffin-embedded tissue of the matching primary tumors. The results revealed substantial divergences between the primary tumor tissues and matching cell lines in the immunoreactivity pattern of medulloblastoma-subgroup-specific protein markers. Regardless of the molecular subgroup of the primary tumor, all six patient-derived medulloblastoma cell lines exhibited a uniform phenotype: immunofluorescence showed the nuclear localization of YAP1, accompanied by strong cytoplasmic positivity for β-catenin and filamin A, as well as weak positivity for GAB1. The same immunoreactivity pattern was also found in both DAOY and D283 Med reference medulloblastoma cell lines. Therefore, we can conclude that various medulloblastoma cell lines tend to exhibit the same characteristics of protein marker expression under standard in vitro conditions. Such a finding emphasizes the importance of the analyses of primary tumors in clinically oriented medulloblastoma research and the urgent need to develop in vitro models of improved clinical relevance, such as 3D cultures and organotypic slice cultures.

Expression of nestin, CD133 and ABCG2 in relation to the clinical outcome in pediatric sarcomas

BACKGROUND

Nestin, CD133 and ABCG2 are recently discussed as putative markers, co-expression of which might determine a cancer stem cell (CSC) phenotype in sarcomas.

OBJECTIVE

Our study is focused on immunohistochemical analysis of nestin, CD133 and ABCG2 expression in rhabdomyosarcoma, Ewing sarcoma and osteosarcoma. Furthermore, we also analyzed the possible correlation of nestin, CD133 and ABCG2 expression levels with the patient outcome to identify potential prognostic values of these three putative CSC markers in the same cohorts.

METHODS

Using immunohistochemistry, expression of nestin, CD133 and ABCG2 was analyzed in 24 rhabdomyosarcoma, 22 Ewing sarcoma and 10 osteosarcoma tissue samples and expression levels of these markers were correlated with clinical outcome.

RESULTS

High nestin levels indicate poor prognosis in patients with Ewing sarcoma (P = 0.001), and high CD133 expression is associated with shorter survival in rhabdomyosarcoma patients (P = 0.002). In contrast, no significant relationship was found between ABCG2 expression and the clinical outcome.

CONCLUSIONS

Our analysis represents the first complex study of these three putative CSCs markers together in three different types of pediatric sarcomas and showed their possible prognostic values in these tumors.

New Brain Tumor Entities Emerge from Molecular Classification of CNS-PNETs

Primitive neuroectodermal tumors of the central nervous system (CNS-PNETs) are highly aggressive, poorly differentiated embryonal tumors occurring predominantly in young children but also affecting adolescents and adults. Herein, we demonstrate that a significant proportion of institutionally diagnosed CNS-PNETs display molecular profiles indistinguishable from those of various other well-defined CNS tumor entities, facilitating diagnosis and appropriate therapy for patients with these tumors. From the remaining fraction of CNS-PNETs, we identify four new CNS tumor entities, each associated with a recurrent genetic alteration and distinct histopathological and clinical features. These new molecular entities, designated "CNS neuroblastoma with FOXR2 activation (CNS NB-FOXR2)," "CNS Ewing sarcoma family tumor with CIC alteration (CNS EFT-CIC)," "CNS high-grade neuroepithelial tumor with MN1 alteration (CNS HGNET-MN1)," and "CNS high-grade neuroepithelial tumor with BCOR alteration (CNS HGNET-BCOR)," will enable meaningful clinical trials and the development of therapeutic strategies for patients affected by poorly differentiated CNS tumors.

Therapeutic Impact of Cytoreductive Surgery and Irradiation of Posterior Fossa Ependymoma in the Molecular Era: A Retrospective Multicohort Analysis

PURPOSE

Posterior fossa ependymoma comprises two distinct molecular variants termed EPN_PFA and EPN_PFB that have a distinct biology and natural history. The therapeutic value of cytoreductive surgery and radiation therapy for posterior fossa ependymoma after accounting for molecular subgroup is not known.

METHODS

Four independent nonoverlapping retrospective cohorts of posterior fossa ependymomas (n = 820) were profiled using genome-wide methylation arrays. Risk stratification models were designed based on known clinical and newly described molecular biomarkers identified by multivariable Cox proportional hazards analyses.

RESULTS

Molecular subgroup is a powerful independent predictor of outcome even when accounting for age or treatment regimen. Incompletely resected EPN_PFA ependymomas have a dismal prognosis, with a 5-year progression-free survival ranging from 26.1% to 56.8% across all four cohorts. Although first-line (adjuvant) radiation is clearly beneficial for completely resected EPN_PFA, a substantial proportion of patients with EPN_PFB can be cured with surgery alone, and patients with relapsed EPN_PFB can often be treated successfully with delayed external-beam irradiation.

CONCLUSION

The most impactful biomarker for posterior fossa ependymoma is molecular subgroup affiliation, independent of other demographic or treatment variables. However, both EPN_PFA and EPN_PFB still benefit from increased extent of resection, with the survival rates being particularly poor for subtotally resected EPN_PFA, even with adjuvant radiation therapy. Patients with EPN_PFB who undergo gross total resection are at lower risk for relapse and should be considered for inclusion in a randomized clinical trial of observation alone with radiation reserved for those who experience recurrence.

Prognostic value of medulloblastoma extent of resection after accounting for molecular subgroup: a retrospective integrated clinical and molecular analysis

Background

Incomplete surgical resection of medulloblastoma is controversially considered a marker of high-risk disease; driving aggressive surgical resections, “second-look” surgeries, and/or intensified chemoradiotherapy. All prior publications evaluating the clinical importance of extent of resection (EOR) failed to account for molecular subgroup. We analysed the prognostic value of EOR across 787 medulloblastoma samples in a subgroup-specific manner.

Methods

We retrospectively identified patients from Medulloblastoma Advanced Genomics International Consortium (MAGIC) centres with a histological diagnosis of medulloblastoma and complete extent of resection and survival data. Specimens were collected from 35 international institutions. Medulloblastoma subgroup affiliation was determined using nanoString gene expression profiling on frozen or formalin-fixed paraffin-embedded tissues. Extent of resection (EOR) based on post-operative imaging was classified as gross total (GTR), near total (NTR, <1·5cm²), or subtotal (STR, ≥ 1·5cm²). Overall survival (OS) and progression-free survival (PFS) multivariable analyses including subgroup, age, metastatic status, geographical location of therapy (North America/Australia vs world), and adjuvant therapy regimen were performed. The primary endpoint was the impact of surgical EOR by molecular subgroup and other clinical variables on OS and PFS.

Findings

787 medulloblastoma patients (86 WNT, 242 SHH, 163 Group 3, and 296 Group 4) were included in a multivariable Cox model of PFS and OS. The marked benefit of EOR in the overall cohort was greatly attenuated after including molecular subgroup in the multivariable analysis. There was an observed PFS benefit of GTR over STR (hazard ration [HR] 1·45, 95% CI; 1·07–1·96, p=0·02) but there was no observed PFS or OS benefit of GTR over NTR (HR 1·05, 0·71–1·53, p=0·82 and HR 1·14, 0·75–1·72, p=0.55). There was no statistically significant survival benefit to greater EOR for patients with WNT, SHH, or Group 3 patients (HR 1·03, 0·67–1·58, p=0·9 for STR vs. GTR). There was a PFS benefit for GTR over STR in patients with Group 4 medulloblastoma (HR1·97, 1·22–3·17, p=0·01), particularly those with metastatic disease (HR 2·22, 1–4·93, p=0·05). A nomogram based on this multivariable cox proportional hazards model shows the comparably smaller impact of EOR on relative risk for PFS and OS than subgroup affiliation, metastatic status, radiation dose, and adjuvant chemotherapy.

Interpretation

The prognostic benefit of EOR for patients with medulloblastoma is attenuated after accounting for molecular subgroup affiliation. Although maximal safe surgical resection should remain the standard of care, surgical removal of small residual portions of medulloblastoma is not recommended when the likelihood of neurological morbidity is high as there is no definitive benefit to GTR over NTR. Our results suggest a re-evaluation of the long-term implications of intensified craniospinal irradiation (36 Gy) in children with small residual portions of medulloblastoma.

Funding

Funding Canadian Cancer Society Research Institute, Terry Fox Research Institute, Canadian Institutes of Health Research, National Institutes of Health, Pediatric Brain Tumor Foundation, Garron Family Chair in Childhood Cancer Research.

[Identification of a Family with SUFU Germline Deletion Based on a Case of Desmoplastic Medulloblastoma in an Infant]

BACKGROUND

Medulloblastoma, an embryonal neuroectodermal tumor of the cerebellum, is the most common malignant brain tumor in children. There are approximately 15 cases diagnosed in the Czech Republic each year. The recent World Health Organization classification recognizes several histopathological subtypes of medulloblastoma: classical, desmoplastic/ nodular with its extensive-nodularity variant, and anaplastic/ large-cell variant. Further molecular analysis identified four basic subgroups of medulloblastoma: WNT, SHH, Group 3, and Group 4. The subgroup of SHH meduloblastoma is associated with somatic mutations of SHH, PTCH1, SUFU, SMO and TP53, while the most common mutations found in infants up to three years of age were PTCH1 and SUFU. The majority of medulloblastomas are sporadic diseases, whereas only about 5- 10% of all cases occur in connection with hereditary genetic syndromes.

CASE

We present a case of a 21-months old girl diagnosed with a localized posterior fossa tumor. The histopathological examination revealed a desmoplastic/ nodular medulloblastoma. The treatment comprised a radical exstirpation of the tumor followed by adjuvant chemotherapy. With the use of array-CGH, a partial biallelic deletion of the SUFU gene (locus 10q24.32) was detected in the tumor DNA, whereas a monoallelic deletion was found in the peripheral lymphocyte DNA of the patient. These findings were confirmed by an independent qPCR method. Monoallelic germline deletion of SUFU was also identified in the patients mother, who was a healthy carrier. Pedigree of the family suggested a transition of the germline deletion of SUFU, since another brain tumors (including one case diagnosed before the age of three years) were identified in previous generations.

CONCLUSION

Germline mutations in SUFU gene are believed to predispose to infant desmoplastic/ nodular medulloblastomas, basal cell carcinomas and meningiomas. The susceptibility gene shows autosomal dominant inheritance with an incomplete penetrance. There is no evidence-based surveillance strategy suggested for the carriers of germline SUFU mutations/ deletions so far. Our recommendation is based both on a family history of our patient and similar cases described in the literature. Since the germinal mutations in SUFU are responsible for up to 50% of all desmoplastic medulloblastomas in children under three years of age, genetic testing of SUFU should be encouraged in this population of patients.

Cancer stem cell markers in pediatric sarcomas: Sox2 is associated with tumorigenicity in immunodeficient mice

The three most frequent pediatric sarcomas, i.e., Ewing's sarcoma, osteosarcoma, and rhabdomyosarcoma, were examined in this study: three cell lines derived from three primary tumor samples were analyzed from each of these tumor types. Detailed comparative analysis of the expression of three putative cancer stem cell markers related to sarcomas-ABCG2, CD133, and nestin-was performed on both primary tumor tissues and corresponding cell lines. The obtained results showed that the frequency of ABCG2-positive and CD133-positive cells was predominantly increased in the respective cell lines but that the high levels of nestin expression were reduced in both osteosarcomas and rhabdomyosarcomas under in vitro conditions. These findings suggest the selection advantage of cells expressing ABCG2 or CD133, but the functional tests in NOD/SCID gamma mice did not confirm the tumorigenic potential of cells harboring this phenotype. Subsequent analysis of the expression of common stem cell markers revealed an evident relationship between the expression of the transcription factor Sox2 and the tumorigenicity of the cell lines in immunodeficient mice: the Sox2 levels were highest in the two cell lines that were demonstrated as tumorigenic. Furthermore, Sox2-positive cells were found in the respective primary tumors and all xenograft tumors showed apparent accumulation of these cells. All of these findings support our conclusion that regardless of the expression of ABCG2, CD133 and nestin, only cells displaying increased Sox2 expression are directly involved in tumor initiation and growth; therefore, these cells fit the definition of the cancer stem cell phenotype.

[Profile of Activation of Tyrosine Kinases and MAP Kinases in Therapy of Maffucci Syndrome]

BACKGROUND

Maffucci syndrome is a rare congenital nonhereditary disease characterized by multiple hemangiomas and enchondromas, which may progress into malignancy. The causal therapy does not exist, and therapy is aimed at complications. The determination of appropriate therapy is complicated, and a multidisciplinary approach is often essential.

CASE

Authors are presenting the case of a 20-year -old patient with Maffucci syndrome. During her life, multiple enchondromas and progressing hemangiomas have been revealed and they have caused many complications, such as limited movement, growth failure, pain, fluidothorax and ascites. A profile of phosphorylation of selected tyrosine kinases and MAP kinases from progressing hemangioma was performed and with consideration of the result, it led to change of treatment strategy with encouraging clinical response lasting for six months.

Molecular Classification of Ependymal Tumors across All CNS Compartments, Histopathological Grades, and Age Groups

Ependymal tumors across age groups are currently classified and graded solely by histopathology. It is, however, commonly accepted that this classification scheme has limited clinical utility based on its lack of reproducibility in predicting patients' outcome. We aimed at establishing a uniform molecular classification using DNA methylation profiling. Nine molecular subgroups were identified in a large cohort of 500 tumors, 3 in each anatomical compartment of the CNS, spine, posterior fossa, supratentorial. Two supratentorial subgroups are characterized by prototypic fusion genes involving RELA and YAP1, respectively. Regarding clinical associations, the molecular classification proposed herein outperforms the current histopathological classification and thus might serve as a basis for the next World Health Organization classification of CNS tumors.

Overexpression of the ∆Np73 isoform is associated with centrosome amplification in brain tumor cell lines

The p73 protein is a member of the p53 family, and this protein is known to be essential for the maintenance of genomic stability, DNA repair, and apoptosis regulation. Transcription from two promoters leads to two main N-terminal isoforms: the TAp73 isoform is reported to have tumor suppressor function, whereas the ΔNp73 isoform likely has oncogenic potential. The present study is focused on the investigation of a possible role of both these p73 N-terminal isoforms in the process of centrosome amplification. HGG-02 and GM7 glioblastoma cell lines and the Daoy medulloblastoma cell line were used in this study. The cells were analyzed using indirect immunofluorescence to determine TAp73 and ΔNp73 expression patterns and possible co-localization with the BubR1 protein, as well as the number of centrosomes. A transiently transfected GM7 cell line was used to verify the results concerning the N-terminal isoforms in relation to centrosome amplification. We found that increased immunoreactivity for the ΔNp73 isoform is associated with the occurrence of an abnormal number of centrosomes in particular cells. Using the transiently transfected GM7 cell line, we confirmed that centrosome amplification is present in cells with overexpression of the ΔNp73 isoform. In contrast, the immunoreactivity for the TAp73 isoform was weak or medium in most of the cells with an aberrant number of centrosomes. To determine the putative counterpart of the p73 N-terminal isoforms among spindle assembly checkpoint (SAC) proteins, we also evaluated possible interactions between the N-terminal isoforms and BubR1 protein, but no co-localization of these proteins was observed.

WNT activation by lithium abrogates TP53 mutation associated radiation resistance in medulloblastoma

TP53 mutations confer subgroup specific poor survival for children with medulloblastoma. We hypothesized that WNT activation which is associated with improved survival for such children abrogates TP53 related radioresistance and can be used to sensitize TP53 mutant tumors for radiation. We examined the subgroup-specific role of TP53 mutations in a cohort of 314 patients treated with radiation. TP53 wild-type or mutant human medulloblastoma cell-lines and normal neural stem cells were used to test radioresistance of TP53 mutations and the radiosensitizing effect of WNT activation on tumors and the developing brain. Children with WNT/TP53 mutant medulloblastoma had higher 5-year survival than those with SHH/TP53 mutant tumours (100% and 36.6% ± 8.7%, respectively (p < 0.001)). Introduction of TP53 mutation into medulloblastoma cells induced radioresistance (survival fractions at 2Gy (SF2) of 89% ± 2% vs. 57.4% ± 1.8% (p < 0.01)). In contrast, β-catenin mutation sensitized TP53 mutant cells to radiation (p < 0.05). Lithium, an activator of the WNT pathway, sensitized TP53 mutant medulloblastoma to radiation (SF2 of 43.5% ± 1.5% in lithium treated cells vs. 56.6 ± 3% (p < 0.01)) accompanied by increased number of γH2AX foci. Normal neural stem cells were protected from lithium induced radiation damage (SF2 of 33% ± 8% for lithium treated cells vs. 27% ± 3% for untreated controls (p = 0.05). Poor survival of patients with TP53 mutant medulloblastoma may be related to radiation resistance. Since constitutive activation of the WNT pathway by lithium sensitizes TP53 mutant medulloblastoma cells and protect normal neural stem cells from radiation, this oral drug may represent an attractive novel therapy for high-risk medulloblastomas.

[Subependymal giant cell astrocytoma associated with tuberous sclerosis complex - pharmacological treatment using mTOR inhibitors]

Tuberous sclerosis complex is a neurocutaneous syndrome that results from a germline mutation in TSC1 or TSC2 genes. The pathogenic activation of mTORC1 leads to the development of subependymal giant cell astrocytomas in patients with tuberous sclerosis complex. Blocking of the dysregulated pathway with mTOR inhibitors has the potential to reduce the volume of this low-grade brain tumor. This article reviews the current knowledge on the pharmacological treatment of subependymal giant cell astrocytomas. A longterm followup and early therapeutic intervention should lead to mortality and morbidity reduction and quality of life improvement in patients with tuberous sclerosis complex associated tumors.

Enhancer hijacking activates GFI1 family oncogenes in medulloblastoma

Medulloblastoma is a highly malignant paediatric brain tumour currently treated with a combination of surgery, radiation and chemotherapy, posing a considerable burden of toxicity to the developing child. Genomics has illuminated the extensive intertumoral heterogeneity of medulloblastoma, identifying four distinct molecular subgroups. Group 3 and group 4 subgroup medulloblastomas account for most paediatric cases; yet, oncogenic drivers for these subtypes remain largely unidentified. Here we describe a series of prevalent, highly disparate genomic structural variants, restricted to groups 3 and 4, resulting in specific and mutually exclusive activation of the growth factor independent 1 family proto-oncogenes, GFI1 and GFI1B. Somatic structural variants juxtapose GFI1 or GFI1B coding sequences proximal to active enhancer elements, including super-enhancers, instigating oncogenic activity. Our results, supported by evidence from mouse models, identify GFI1 and GFI1B as prominent medulloblastoma oncogenes and implicate 'enhancer hijacking' as an efficient mechanism driving oncogene activation in a childhood cancer.

The ATRA-induced differentiation of medulloblastoma cells is enhanced with LOX/COX inhibitors: an analysis of gene expression

Background

A detailed analysis of the expression of 440 cancer-related genes was performed after the combined treatment of medulloblastoma cells with all-trans retinoic acid (ATRA) and inhibitors of lipoxygenases (LOX) and cyclooxygenases (COX). The combinations of retinoids and celecoxib as a COX-2 inhibitor were reported to be effective in some regimens of metronomic therapy of relapsed solid tumors with poor prognosis. Our previous findings on neuroblastoma cells using expression profiling showed that LOX/COX inhibitors have the capability of enhancing the differentiating action of ATRA. Presented study focused on the continuation of our previous work to confirm the possibility of enhancing ATRA-induced cell differentiation in these cell lines via the application of LOX/COX inhibitors. This study provides more detailed information concerning the mechanisms of the enhancement of the ATRA-induced differentiation of medulloblastoma cells.

Methods

The Daoy and D283 Med medulloblastoma cell lines were chosen for this study. Caffeic acid (an inhibitor of 5-LOX) and celecoxib (an inhibitor on COX-2) were used in combined treatment with ATRA. The expression profiling was performed using Human Cancer Oligo GEArray membranes, and the most promising results were verified using RT-PCR.

Results

The expression profiling of the selected cancer-related genes clearly confirmed that the differentiating effects of ATRA should be enhanced via its combined administration with caffeic acid or celecoxib. This effect was detected in both cell lines. An increased expression of the genes that encoded the proteins participating in induced differentiation and cytoskeleton remodeling was detected in both cell lines in a concentration-dependent manner. This effect was also observed for the CDKN1A gene encoding the p21 protein, which is an important regulator of the cell cycle, and for the genes encoding proteins that are associated with proteasome activity. Furthermore, our results showed that D283 Med cells are significantly more sensitive to treatment with ATRA alone than Daoy cells.

Conclusions

The obtained results on medulloblastoma cell lines are in accordance with our previous findings on neuroblastoma cells and confirm our hypothesis concerning the common mechanism of the enhancement of ATRA-induced cell differentiation in various types of pediatric solid tumors.

Cytogenetic prognostication within medulloblastoma subgroups

PURPOSE

Medulloblastoma comprises four distinct molecular subgroups: WNT, SHH, Group 3, and Group 4. Current medulloblastoma protocols stratify patients based on clinical features: patient age, metastatic stage, extent of resection, and histologic variant. Stark prognostic and genetic differences among the four subgroups suggest that subgroup-specific molecular biomarkers could improve patient prognostication.

PATIENTS AND METHODS

Molecular biomarkers were identified from a discovery set of 673 medulloblastomas from 43 cities around the world. Combined risk stratification models were designed based on clinical and cytogenetic biomarkers identified by multivariable Cox proportional hazards analyses. Identified biomarkers were tested using fluorescent in situ hybridization (FISH) on a nonoverlapping medulloblastoma tissue microarray (n = 453), with subsequent validation of the risk stratification models.

RESULTS

Subgroup information improves the predictive accuracy of a multivariable survival model compared with clinical biomarkers alone. Most previously published cytogenetic biomarkers are only prognostic within a single medulloblastoma subgroup. Profiling six FISH biomarkers (GLI2, MYC, chromosome 11 [chr11], chr14, 17p, and 17q) on formalin-fixed paraffin-embedded tissues, we can reliably and reproducibly identify very low-risk and very high-risk patients within SHH, Group 3, and Group 4 medulloblastomas.

CONCLUSION

Combining subgroup and cytogenetic biomarkers with established clinical biomarkers substantially improves patient prognostication, even in the context of heterogeneous clinical therapies. The prognostic significance of most molecular biomarkers is restricted to a specific subgroup. We have identified a small panel of cytogenetic biomarkers that reliably identifies very high-risk and very low-risk groups of patients, making it an excellent tool for selecting patients for therapy intensification and therapy de-escalation in future clinical trials.

TERT promoter mutations are highly recurrent in SHH subgroup medulloblastoma

Telomerase reverse transcriptase (TERT) promoter mutations were recently shown to drive telomerase activity in various cancer types, including medulloblastoma. However, the clinical and biological implications of TERT mutations in medulloblastoma have not been described. Hence, we sought to describe these mutations and their impact in a subgroup-specific manner. We analyzed the TERT promoter by direct sequencing and genotyping in 466 medulloblastomas. The mutational distributions were determined according to subgroup affiliation, demographics, and clinical, prognostic, and molecular features. Integrated genomics approaches were used to identify specific somatic copy number alterations in TERT promoter-mutated and wild-type tumors. Overall, TERT promoter mutations were identified in 21 % of medulloblastomas. Strikingly, the highest frequencies of TERT mutations were observed in SHH (83 %; 55/66) and WNT (31 %; 4/13) medulloblastomas derived from adult patients. Group 3 and Group 4 harbored this alteration in <5 % of cases and showed no association with increased patient age. The prognostic implications of these mutations were highly subgroup-specific. TERT mutations identified a subset with good and poor prognosis in SHH and Group 4 tumors, respectively. Monosomy 6 was mostly restricted to WNT tumors without TERT mutations. Hallmark SHH focal copy number aberrations and chromosome 10q deletion were mutually exclusive with TERT mutations within SHH tumors. TERT promoter mutations are the most common recurrent somatic point mutation in medulloblastoma, and are very highly enriched in adult SHH and WNT tumors. TERT mutations define a subset of SHH medulloblastoma with distinct demographics, cytogenetics, and outcomes.

EGFR signaling in the HGG-02 glioblastoma cell line with an unusual loss of EGFR gene copy

Epidermal growth factor receptor (EGFR) gene amplification and the overexpression of EGFR are described as common features of glioblastoma multiforme (GBM). Nevertheless, we previously reported the loss of EGFR gene copy in a GBM specimen from a patient with an unusually favorable course of the disease, and the HGG-02 cell line with this aberration was successfully derived from this tumor. Here, we present a detailed analysis of changes in gene expression and cell signaling in the HGG-02 cell line; the GM7 reference cell line with a standard EGFR gene copy number derived from a very aggressive GBM was used as a control. We confirmed the downregulation of EGFR expression and signaling in HGG-02 cells using different methods (RTK analysis, gene profiling and RT-PCR). Other changes that may have contributed to the non-aggressive phenotype of the primary tumor were identified, including the downregulated phosphorylation of the Axl and Trk receptors, as well as increased activity of JNK and p38 kinases. Notably, differences in PDGF signaling were detected in both of these cell lines; HGG-02 cells preferentially expressed and signaled through PDGFRα, and PDGFRβ was strongly overexpressed and phosphorylated in the GM7 reference cell line. Using expression profiling of cancer-related genes, we revealed the specific profile of HGG-02 cells that included upregulated tumor-suppressors as well as downregulated genes associated with the extracellular matrix. This study represents the first comprehensive analysis of gene expression and cell signaling in glioblastoma cells with lower EGFR gene dosage. As indicated by our results, the TAM receptors, Trk receptors and PDGFRs need to be investigated further since their regulation appears to be important for glioblastoma biological features as well as the clinical course of the disease.

Subgroup-specific prognostic implications of TP53 mutation in medulloblastoma

PURPOSE

Reports detailing the prognostic impact of TP53 mutations in medulloblastoma offer conflicting conclusions. We resolve this issue through the inclusion of molecular subgroup profiles.

PATIENTS AND METHODS

We determined subgroup affiliation, TP53 mutation status, and clinical outcome in a discovery cohort of 397 medulloblastomas. We subsequently validated our results on an independent cohort of 156 medulloblastomas.

RESULTS

TP53 mutations are enriched in wingless (WNT; 16%) and sonic hedgehog (SHH; 21%) medulloblastomas and are virtually absent in subgroups 3 and 4 tumors (P < .001). Patients with SHH/TP53 mutant tumors are almost exclusively between ages 5 and 18 years, dramatically different from the general SHH distribution (P < .001). Children with SHH/TP53 mutant tumors harbor 56% germline TP53 mutations, which are not observed in children with WNT/TP53 mutant tumors. Five-year overall survival (OS; ± SE) was 41% ± 9% and 81% ± 5% for patients with SHH medulloblastomas with and without TP53 mutations, respectively (P < .001). Furthermore, TP53 mutations accounted for 72% of deaths in children older than 5 years with SHH medulloblastomas. In contrast, 5-year OS rates were 90% ± 9% and 97% ± 3% for patients with WNT tumors with and without TP53 mutations (P = .21). Multivariate analysis revealed that TP53 status was the most important risk factor for SHH medulloblastoma. Survival rates in the validation cohort mimicked the discovery results, revealing that poor survival of TP53 mutations is restricted to patients with SHH medulloblastomas (P = .012) and not WNT tumors.

CONCLUSION

Subgroup-specific analysis reconciles prior conflicting publications and confirms that TP53 mutations are enriched among SHH medulloblastomas, in which they portend poor outcome and account for a large proportion of treatment failures in these patients.

Intracellular distribution of the ΔNp73 protein isoform in medulloblastoma cells: a study with newly generated rabbit polyclonal antibodies

The p73 protein is a member of the p53 family of transcription factors that has two N-terminal isoforms: the TAp73 isoform is reported to have a tumor suppressor function, whereas the ΔNp73 isoform likely has oncogenic potential. The expression of these isoforms and the differences in their intracellular distribution have been described in many cancer types; however, little is known about the p73 isoforms in brain tumors. Our study is focused on the intracellular localization of ΔNp73 in medulloblastoma cell lines. Due to a lack of suitable anti-ΔNp73 antibodies, we developed two new rabbit polyclonal antibodies, ΔNp73-26 and ΔNp73-27, with sufficient specificity, as demonstrated by immunodetection methods using transiently transfected cell lines. Both of these new antibodies were subsequently used for analysis of the ΔNp73 distribution in medulloblastoma cells using immunofluorescence, immunoblotting and immunogold labeling for transmission electron microscopy. We found a nuclear localization of the ΔNp73 isoform in all of the medulloblastoma cell lines included in this study. Furthermore, a non-random accumulation of the ΔNp73 isoform near the cell nuclei was observable in all of these cell lines. By double-labeling with ΔNp73 and golgin-97, we showed the co-localization of the ΔNp73 isoform with the Golgi apparatus. Nevertheless, further detailed analyses of possible interactions of ΔNp73 with the proteins accumulated in the Golgi apparatus should be performed to explain the dynamics of ΔNp73 outside the cell nucleus.

Subgroup-specific structural variation across 1,000 medulloblastoma genomes

Medulloblastoma, the most common malignant paediatric brain tumour, is currently treated with nonspecific cytotoxic therapies including surgery, whole-brain radiation, and aggressive chemotherapy. As medulloblastoma exhibits marked intertumoural heterogeneity, with at least four distinct molecular variants, previous attempts to identify targets for therapy have been underpowered because of small samples sizes. Here we report somatic copy number aberrations (SCNAs) in 1,087 unique medulloblastomas. SCNAs are common in medulloblastoma, and are predominantly subgroup-enriched. The most common region of focal copy number gain is a tandem duplication of SNCAIP, a gene associated with Parkinson's disease, which is exquisitely restricted to Group 4α. Recurrent translocations of PVT1, including PVT1-MYC and PVT1-NDRG1, that arise through chromothripsis are restricted to Group 3. Numerous targetable SCNAs, including recurrent events targeting TGF-β signalling in Group 3, and NF-κB signalling in Group 4, suggest future avenues for rational, targeted therapy.

CD133 expression and identification of CD133/nestin positive cells in rhabdomyosarcomas and rhabdomyosarcoma cell lines

Background: Co-expression of CD133, cell surface glycoprotein, and nestin, an intermediate filament protein, was determined to be a marker of neural stem cells and of cancer stem cells in neurogenic tumors. Methods: We examined the expression of CD133 and nestin in ten tumor tissue samples taken from patients with rhabdomyosarcomas and in five rhabdomyosarcoma cell lines. Immunohistochemistry and immunofluorescence were used to examine FFPE tumor tissue samples. Cell lines were analyzed by immunofluorescence, immunoblotting, flow cytometry, and RT-PCR. Functional assays (clonogenic in vitro assay and tumorigenic in vivo assay) were also performed using these cell lines. Results: CD133 and nestin were detected in all 10 tumor tissue samples and in all 5 cell lines; however, the frequency of CD133+, Nes+, and CD133+/Nes+ cells, as well as the intensity of fluorescence varied in individual samples or cell lines. The expression of CD133 and nestin was subsequently confirmed in all cell lines by immunoblotting. Furthermore, we observed an increasing expression of CD133 in relation to the cultivation. All cell lines were positive for Oct3/4 and nucleostemin; NSTS-11 cells were also able to form xenograft tumors in mice. Conclusion: Our results represent the first evidence of CD133 expression in rhabdomyosarcoma tissue and in rhabdomyosarcoma cell lines. In addition, the co-expression of CD133 and nestin as well as results of the functional assays suggest a possible presence of cancer cells with a stem-like phenotype in these tumors.

Metronomic chemotherapy with the COMBAT regimen in advanced pediatric malignancies: a multicenter experience

BACKGROUND

The outcome of children with refractory/relapsed malignancies remains poor and novel therapies are urgently required. One of the promising approaches is metronomic chemotherapy. We present the clinical results of 74 children with advanced solid tumors treated according to treatment recommendation with data registry in three European pediatric centers.

METHODS

COMBAT (Combined Oral Metronomic Biodifferentiating Antiangiogenic Treatment) included low-dose daily temozolomide, etoposide, celecoxib, vitamin D, fenofibrate and retinoic acid. From 2004 to 2010, 74 children were enrolled.

RESULTS

The 2-year overall survival (OS) was 43.1% (median 15.4, range 1.3-69.9 months). Of the 74 patients, 50 patients (68%) died and 24 are alive: 6 (8%) with progressive disease, 7 (9%) with stable disease/partial response and 11 (15%) in complete response. Median time to response was 6 months. Of 62 patients with initially measurable disease, 25 (40%) had radiological response or stable disease. Fourteen of 25 showing clinical benefit responded within the first 6 months. The treatment was well tolerated on an outpatient basis. Regarding non-hematological toxicity of grade ≥2, hepatotoxicity of grade 3 occurred in 8 children and grade 3 cheilitis in 16 children.

CONCLUSION

COMBAT is a feasible and effective treatment option for patients with relapsing/refractory malignancies. The treatment is well tolerated with a low acute toxicity profile.

Nestin expression in high-grade osteosarcomas and its clinical significance

Nestin has been detected in various malignancies and its expression correlates with advanced grade in some neoplasms. The aim of this study was to examine nestin expression in high-grade osteosarcomas and to determine its prognostic value. Using immunohistochemistry and immunofluorescence, we evaluated nestin expression in tumor tissue samples from 45 patients with high-grade osteosarcomas. In both methods, the frequency of nestin-positive tumor cells was classified into three categories (1+, 2+ and 3+ for immunohistochemistry; 1F+, 2F+ and 3F+ for immunofluorescence) and clinicopathological correlations were statistically evaluated and analyzed. Nestin-positive tumor cells were detected in all of the examined osteosarcomas using both immunohistochemistry and immunofluorescence, although the proportion of undoubtedly positive neoplastic cells varied in individual samples from a few nestin-positive tumor cells to diffuse nestin positivity. High levels of nestin expression detected by immunofluorescence (2F+ and 3F+) were associated with worse clinical outcomes (OS, p=0.031; EFS, p<0.001). However, high levels of nestin expression as measured by immunohistochemistry trended towards shorter patient survival rates but did not reach statistical significance. Despite significantly shorter survival rates observed in patients with high levels of nestin expression assessed by immunofluorescence, nestin does not seem to represent a powerful prognostic marker that would be superior to conventional methods.

Analysis of nuclear nestin localization in cell lines derived from neurogenic tumors

Nestin is a class VI intermediate filament protein expressed in the cytoplasm of stem and progenitor cells in the mammalian CNS during development. In adults, nestin is present only in a small subset of cells and tissues, including the subventricular zone of the adult mammalian brain, where neurogenesis occurs. Nestin expression has also been detected under such pathological conditions as ischemia, inflammation, and brain injury, as well as in various types of human solid tumors and their corresponding cell lines. Furthermore, nestin was recently found in the nuclei of glioblastoma, neuroblastoma, and angiosarcoma cells and it was proved to interact directly with the nuclear DNA in neuroblastoma cells. Here, we perform the first study of the intracellular distribution of nestin in cell lines derived from neurogenic tumors. Using immunodetection methods, we examined nestin expression in tumor-derived cell lines obtained from 11 patients with neuroblastoma, medulloblastoma, or glioblastoma multiforme. Besides its standard cytoplasmic localization, nestin was present in the nuclei of two neuroblastoma cell lines and one medulloblastoma cell line. Nestin was only present in the nuclei of cells with diffuse cytoplasmic staining for this protein, and the proportion of cells positive for nestin in nuclei, as well as the intensity of staining, varied. The presence of nestin in the nuclei was confirmed by both transmission electron microscopy and Western blotting. Our results indicate that the presence of nestin in the nuclei of tumor cells is not very rare, especially under in vitro conditions.

Analysis of the intracellular localization of p73 N-terminal protein isoforms TAp73 and ∆Np73 in medulloblastoma cell lines

The protein homologous to the tumor suppressor p53, p73, has essential roles in development and tumorigenesis. This protein exists in a wide range of isoforms with different, even antagonistic, functions. However, there are virtually no detailed morphological studies analyzing the endogenous expression of p73 isoforms at the cellular level in cancer cells. In this study, we investigated the expression and subcellular distribution of two N-terminal isoforms, TAp73 and ΔNp73, in medulloblastoma cells using immunofluorescence microscopy. Both proteins were observed in all cell lines examined, but differences were noted in their intracellular localization between the reference Daoy cell line and four newly established medulloblastoma cell lines (MBL-03, MBL-06, MBL-07 and MBL-10). In the new cell lines, TAp73 and ΔNp73 were located predominantly in cell nuclei. However, there was heterogeneity in TAp73 distribution in the cells of all MBL cell lines, with the protein located in the nucleus and also in a limited non-random area in the cytoplasm. In a small percentage of cells, we detected cytoplasmic localization of TAp73 only, i.e., nuclear exclusion was observed. Our results provide a basis for future studies on the causes and function of distinct intracellular localization of p73 protein isoforms with respect to different protein-protein interactions in medulloblastoma cells.

Low-level copy number changes of MYC genes have a prognostic impact in medulloblastoma

High-level amplifications of MYC genes are associated with poor outcomes in childhood medulloblastoma (MB). However, the occurrence of MYCN and MYCC copy number increases below the intense amplification pattern is rarely reported, and its clinical impact has not yet been determined. Here, we describe this phenomenon and its prognostic significance in a cohort of 29 MB patients. Using interphase fluorescence in situ hybridization (I-FISH), low-level copy number alterations, i.e. gain of MYCN, were shown in 5/27 (19%) samples, whereas amplification was revealed in only 1/27 (4%) samples. MYCC gain was revealed in 6/29 (21%) MB, while amplification was disclosed in only 2/29 (7%). Hyperploidy and co-incidence of gains in both MYC loci were frequently observed in samples with copy number aberrations. Survival analysis has clearly shown that MYC copy number increases are associated with lowered event-free survival and overall survival in MB. In the case of MYCN, this negative correlation was statistically significant. We conclude that limited numerical alterations in loci 2p24 (MYCN) and 8q24 (MYCC), as assessed by I-FISH, are present in MB with a higher frequency than high-level amplifications. Poor prognoses were observed in patients with copy number increases in MYC genes. Our data illustrate the importance of further investigations in multicenter trials to better refine the emerging genomic-based prognostic stratification in MB.

An unusual loss of EGFR gene copy in glioblastoma multiforme in a child: a case report and analysis of a successfully derived HGG-02 cell line

PURPOSE

The aim of this study was to perform a detailed cytogenetic and molecular genetic analysis of a tumor taken from a 14.5-year-old boy with glioblastoma multiforme who showed an atypical clinical course.

METHODS

Formalin-fixed, paraffin embedded tumor tissue and the corresponding HGG-02 cell line derived from this tumor were analyzed using fluorescence in situ hybridization (FISH), G-banding, multiplex ligation-dependent probe amplification (MLPA), functional analysis of separated alleles in yeast (FASAY), immunohistochemistry (IHC), and immunocytochemistry (ICC).

RESULTS

Mutation of the p53 gene and hypermethylation of the MLH1 gene were detected by FASAY and MLPA, respectively. Cytogenetic analysis showed a polyploid karyotype with extensive heterogeneity in chromosome number. Using FISH, we identified a very unusual genetic change - a loss of EGFR gene copy in both the tumor tissue and the HGG-02 cell line. In accordance with the cytogenetic findings, IHC and ICC did not demonstrate overexpression of EGFR in the tumor tissue or HGG-02 cells.

CONCLUSIONS

Despite his very poor prognosis, the patient experienced 34 months of event-free survival after surgery and adjuvant radiotherapy and chemotherapy. The detected loss of the EGFR gene copy may contribute to the unusual biological features of this tumor, but the forthcoming detailed expression analysis of cancer regulatory pathways is necessary to better understand this tumor phenotype.

Enhancement of ATRA-induced differentiation of neuroblastoma cells with LOX/COX inhibitors: an expression profiling study

BACKGROUND

We performed expression profiling of two neuroblastoma cell lines, SK-N-BE(2) and SH-SY5Y, after combined treatment with all-trans retinoic acid (ATRA) and inhibitors of lipoxygenases (LOX) and cyclooxygenases (COX). This study is a continuation of our previous work confirming the possibility of enhancing ATRA-induced cell differentiation in these cell lines by the application of LOX/COX inhibitors and brings more detailed information concerning the mechanisms of the enhancement of ATRA-induced differentiation of neuroblastoma cells.

METHODS

Caffeic acid, as an inhibitor of 5-lipoxygenase, and celecoxib, as an inhibitor on cyclooxygenase-2, were used in this study. Expression profiling was performed using Human Cancer Oligo GEArray membranes that cover 440 cancer-related genes.

RESULTS

Cluster analyses of the changes in gene expression showed the concentration-dependent increase in genes known to be involved in the process of retinoid-induced neuronal differentiation, especially in cytoskeleton remodeling. These changes were detected in both cell lines, and they were independent of the type of specific inhibitors, suggesting a common mechanism of ATRA-induced differentiation enhancement. Furthermore, we also found overexpression of some genes in the same cell line (SK-N-BE(2) or SH-SY5Y) after combined treatment with both ATRA and CA, or ATRA and CX. Finally, we also detected that gene expression was changed after treatment with the same inhibitor (CA or CX) in combination with ATRA in both cell lines.

CONCLUSIONS

Obtained results confirmed our initial hypothesis of the common mechanism of enhancement in ATRA-induced cell differentiation via inhibition of arachidonic acid metabolic pathway.

Influence of LOX/COX inhibitors on cell differentiation induced by all-trans retinoic acid in neuroblastoma cell lines

We investigated the possible modulation by LOX/ COX inhibitors of all-trans retinoic acid (ATRA)-induced cell differentiation in two established neuroblastoma cell lines, SH-SY5Y and SK-N-BE(2). Caffeic acid, as an inhibitor of 5-lipoxygenase, and celecoxib, as an inhibitor of cyclooxygenase-2, were chosen for this study. The effects of the combined treatment with ATRA and LOX/COX inhibitors on neuroblastoma cells were studied using cell morphology assessment, detection of differentiation markers by immunoblotting, measurement of proliferation activity, and cell cycle analysis and apoptosis detection by flow cytometry. The results clearly demonstrated the potential of caffeic acid to enhance ATRA-induced cell differentiation, especially in the SK-N-BE(2) cell line, whereas application of celecoxib alone or with ATRA led predominantly to cytotoxic effects in both cell lines. Moreover, the higher sensitivity of the SK-N-BE(2) cell line to combined treatment with ATRA and LOX/COX inhibitors suggests that cancer stem cells are a main target for this therapeutic approach. Nevertheless, further detailed study of the phenomenon of enhanced cell differentiation by expression profiling is needed.

Central neurocytoma: the neuroradiological perspective

BACKGROUND

Central neurocytoma (CN) represents a rare, relatively recently described primary central nervous system tumor. It ranks among intraventricular tumors due to its predominant location within the lateral brain ventricles. CN occurs mostly in young adults around the 3rd decade of life; almost a fifth of the cases are children under 18 years of age.

OBJECTIVES

The authors present three cases of patients with histopathologically confirmed CN, emphasizing diagnostic imaging issues. A review of the literature concerning differential diagnosis and clinical and therapeutic aspects is also presented.

CONCLUSION

Literature reports of CN comprise most likely case reports, small cohorts of patients, and meta-analytic studies due to the generally low incidence of this tumor. In the current paper, the authors summarize up-to-date knowledge of this rare disease on the background of their own observations. CN should be included in the list for differential diagnostics of intraventricular brain tumors, especially those located in lateral ventricles.

Nestin expression in osteosarcomas and derivation of nestin/CD133 positive osteosarcoma cell lines

Background

Nestin was originally identified as a class VI intermediate filament protein that is expressed in stem cells and progenitor cells in the mammalian CNS during development. This protein is replaced in the adult organism by other intermediate filament proteins; however, nestin may be re-expressed under certain pathological conditions such as ischemia, inflammation, brain injury, and neoplastic transformation. Nestin has been detected in many kinds of tumors, especially in tumors derived from the CNS. Co-expression of nestin and the CD133 surface molecule is considered to be a marker for cancer stem cells in neurogenic tumors. Our work was aimed at a detailed study of nestin expression in osteosarcomas and osteosarcoma-derived cell lines.

Methods

Using immunodetection methods, we examined nestin in tumor tissue samples from 18 patients with osteosarcomas. We also successfully established permanent cell lines from the tumor tissue of 4 patients and immunodetection of nestin and CD133 was performed on these cell lines.

Results

Nestin-positive tumor cells were immunohistochemically detected in all of the examined osteosarcomas, but the proportion of these cells that were positively stained as well as the intensity of staining varied. Nestin-positive cells were rarely observed in 2 tumor samples, and the remaining 16 tumor samples showed various nestin expression patterns ranging from very sporadic occurrence to an overwhelming proportion of cells with strong positive staining. Three of the established osteosarcoma cell lines were demonstrated to be nestin-positive, and only one cell line showed no expression of nestin; this finding corresponds with the rare occurrence of nestin-positive cells in the respective tumor sample. Moreover, three of these osteosarcoma cell lines were undoubtedly proven to be Nes+/CD133+.

Conclusion

Our results represent the first evidence of nestin expression in osteosarcomas and suggest the possible occurrence of cells with a stem-like phenotype in these tumors.

[Radiotherapy induced glioblastoma in a child previously treated for cerebellar medulloblastoma (case report and review of the literature)]

Malignant gliomas represent the most frequent radiotherapy induced ("secondary") solid tumor. Their prognosis remains extremely poor despite of aggressive multimodal treatment. We present a case report of a 16 years old boy who developed cerebellar glioblastoma six years following the combined treatment for medulloblastoma. Clinical history, pathological and cytogenetic findings of the case are discussed along with treatment possibilities.

p73 expression in medulloblastoma: TAp73/DeltaNp73 transcript detection and possible association of p73alpha/DeltaNp73 immunoreactivity with survival

The human p73 protein is essential for normal morphogenesis and maintenance of neural tissue. Recently, several TP73 transcripts have been revealed in medulloblastoma (MB), the most common malignant brain tumor in children. Here, we performed immunohistochemical analysis on 29 MB specimens using anti-p73alpha and anti-DeltaNp73 antibodies. Real-time PCR quantification was performed to assess TAp73 and DeltaNp73 transcripts in a subset of 13 MB samples. Normal cerebellar tissues and RNA were used for comparison. Pilot clinical-pathological correlations were also provided. We report significant differences for TAp73 and DeltaNp73 mRNA expression between tumor tissues and reference (P = 0.013, P = 0.028). Immunohistochemically, 52 and 29% MB samples were positive for p73alpha and DeltaNp73, respectively. p73alpha expression was found to be in both the nucleus and cytoplasm, whereas DeltaNp73 was localized predominantly in the cytoplasm. In normal cerebellum, positive staining for p73alpha and DeltaNp73 was observed in the Purkinje cells of newborns, not adult samples, which supports the developmental role of TP73 during organogenesis of the human cerebellum. Survival analysis has shown negative relationship of DeltaNp73-immunoreactivity with overall survival (OS) and event free survival (EFS) (P = 0.026 and P = 0.127, respectively). For p73alpha-positive cases, the negative trend in OS (P = 0.149) and EFS (P = 0.216) was also apparent. Our results indicate the involvement of p73 protein in MB tumorigenesis and define TP73 as a potential prognostic and therapeutic target for medulloblastoma.

The optimization of sample treatment for spectral karyotyping with applications for human tumour cells

Spectral karyotyping (SKY) represents an important tool for the investigation of the complex chromosomal rearrangements (CCRs) in many human malignancies which may be difficult to characterize by conventional banding techniques. The main goal of our work was to optimize the most important steps in the preparation of molecular cytogenetic slides for a SKY protocol. This approach consisted of optimization of both the aging procedure and protease pretreatment of the slides, with special regard given to the preservation of chromosome structure and shape, as well as to the intensity of hybridization signals. The best results were obtained with a chemical aging procedure using SSC or ethanol in combination with trypsin pretreatment applied at a higher concentration for a shorter period of pretreatment. A resulting protocol for SKY also applicable to human solid tumour cells was subsequently proposed. The practical potential of the SKY technique was demonstrated on examples of two types of human embryonal tumours--neuroblastoma and Wilms' tumour, in which some kinds of chromosomal aberrations were not detectable by means of classic cytogenetic methods.