Kyu Chang Wang

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.

Generation of dopaminergic neurons in vitro from human embryonic stem cells treated with neurotrophic factors.

The aim of this study was to produce dopaminergic neurons in vitro from human embryonic stem (hES) cells following treatment of various neurotrophic factors. MB03 hES cells were induced by retinoic acid (RA) or basic fibroblast growth factor (bFGF), which were further treated with brain derived neurotrophic factor (BDNF) or transforming growth factor (TGF)-alpha in each induction method during neuron differentiation days. At the final differentiation stage (21 days), all treatment groups revealed very similar levels (bFGF, 76-78%; RA, 70-74%) of mature neurons (anti-NF-200) in two induction methods irrespective of the addition of BDNF or TGF-alpha. In addition, immunostaining and HPLC analyses revealed higher levels of tyrosine hydroxylase (20+/-2.3%) and dopamine (265.5+/-62.8 pg/ml) in the bFGF- and TGF-alpha-treated hES cells than in RA- or BDNF-treated hES cells. These data are one of the first reports on the generation of dopaminergic neurons of hES cells in vitro. Also, our results indicate that TGF-alpha may be successfully used in the bFGF induction protocol and yield higher numbers of dopaminergic neurons from hES cells.

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.

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.

Genetically modified human embryonic stem cells relieve symptomatic motor behavior in a rat model of Parkinson's disease

Embryonic stem (ES) cells have great potential as a cell source for cell replacement therapy. To investigate the possibility of using ES cells as a carrier of therapeutic gene(s), human ES cells (MB03) were co-transfected with cDNAs coding for tyrosine hydroxylase (TH) and GTP cyclohydrolase I (GTPCH I), then bulk-selected in the presence of neomycin and hygromycin-B. Successful transfection was confirmed by Western immunoblotting and RT-PCR. The genetically modified ES cells (bk-THGC) were found to produce a significant amount of L-dopa spontaneously and relieved apomorphine-induced asymmetric motor behavior by approximately 54% when grafted into striatum of 6-OHDA-denervated rat brain. The number of rotations, however, increased up to 176+/-18% in 6 weeks when PBS was used instead (sham-graft). Immunohistochemical stainings revealed that the grafted human ES cells survived and expressed TH for at least 6 weeks while the experiment was continued.

Cerebellar alterations induced by chronic hypoxia: an immunohistochemical study using a chick embryonic model

A model of fetal aerogenic hypoxia was developed in which fertilized chicken eggs were half-painted with melted wax and incubated under normal conditions. The cerebellum of the hypoxic chick embryos at a later stage of development (E18-20) was analyzed immunochemically. Hypoxic insult resulted in considerable neurocytological deficits of the Purkinje cells and altered glial fibrillary acid protein (GFAP) immunoreactivity in the fetal cerebellum. Purkinje cells in the hypoxic embryos were marked by small cell size, poorly developed dendrites, low cell density, deletion and ectopia. On the other hand, enhanced GFAP immunoreactivity was found in astrocytes and Bergmann glia of the hypoxic embryos. Our results indicate that chronic hypoxia in the chick fetus can cause severe disorders of neuronal development as well as glial activation. We suggest that our hypoxic model of chick embryos could be an accessible animal model for further elucidating fetal hypoxia.

Incidence and Risk Factors of Ventriculoperitoneal Shunt Infections in Children: A Study of 333 Consecutive Shunts in 6 Years

The major aims of this study were to estimate the infection rate and recognize the risk factor for ventriculoperitoneal (VP) shunt infections in children. To analyze shunt infection rate and identify risk factors, a retrospective cohort analysis of 333 consecutive VP shunt series was performed at Seoul National University Childrens Hospital in Korea between January 2005 and February 2011. Overall, 35 shunts (10.5%) were infected, which represented an infection rate of 0.075 infection cases per shunt per year. VP shunt infection occurred at a median of 1 month (range, 6 days to 8 months) after insertion. An independent risk factor for shunt infection was undergoing an operation before the first year of life (relative risk 2.31; 95% confidence interval, 1.19-4.48). The most common causative microorganism was coagulase-negative staphylococci in 16 (45.7%) followed by Staphylococcus aureus in 8 (22.9%). Methicillin resistance rate was 83.3% among coagulase-negative staphylococci and S. aureus. In this study, cerebrospinal fluid shunt infection rate was 10.5%. Infection was frequently caused by methicillin-resistant coagulase-negative staphylococci and S. aureus within two months after shunt surgery. Vancomycin may be considered as the preoperative prophylaxis for shunt surgery in a situation where methicillin resistance rate is very high.

Intracranial mesenchymal chondrosarcoma: a case report and literature review.

Intracranial mesenchymal chondrosarcoma is a rare entity. The case of a 13-year-old girl with mesenchymal chondrosarcoma which seemed to arise from the dura mater is presented here together with a review of the literature. In the present case, the tumor involved the superior sagittal sinus. It recurred 21 months after gross total removal of the mass and coagulation of the involved wall of the superior sagittal sinus. Reoperation was performed followed by radiation therapy.

Nasal chondromesenchymal hamartoma of infancy clinically mimicking meningoencephalocele.

We report a typical case of nasal chondromesenchymal hamartoma (NCMH) of infancy, which extended to the orbit and intracranium through the skull base. The nasal mass was incidentally found in a 5-month-old otherwise healthy boy who had recently developed ptosis of the left eye. On neuroimaging, there were defects in the left ethmoid bone of the anterior cranial fossa and medial orbital wall. A round heterogeneous mass was found in the left nasal cavity. Solid portions were strongly enhanced. The preoperative diagnosis was nasal glioma or encephalocele. After frontal craniotomy, the mass was separated from the cranial basal dura. Through the transnasal approach, the mass was dissected from the left orbital content and removed. NCMH is a rare benign lesion and histopathological analogue of the mesenchymal hamartoma of the chest wall, having unique pathology: islands of hyaline cartilage, somewhat calcified or ossified hyalinized collagenous trabeculae and abundant myxoid stroma. Its occurrence in the nasal cavity was identified in 1998. The recognition of this entity is necessary to avoid misdiagnosis of the frozen section and for appropriate surgery.

Protective Role of COMP-Ang1 in Ischemic Rat Brain

In cerebral ischemia, the induction of angiogenesis may represent a natural defense mechanism that enables the hypoxic brain to avoid progression into infarction. Angiopoietin‐1 (Ang1) is known to produce non‐leaky and stable blood vessel formation mainly by the Tie2 receptor. Therefore, we envisioned that the application of cartilage oligomeric matrix protein‐Ang1 (COMP‐Ang1), a soluble, stable, and potent form of Ang1, would promote angiogenesis and provide a protective effect following unilateral middle cerebral artery occlusion (MCAO) in rats. To this end, we employed a 2‐hour‐MCAO model, and treated rats with adenovirus encoding COMP‐Ang1 (Ade‐COMP‐Ang1) or control virus encoding β‐gal (Ade‐β‐gal). Time course magnetic resonance images (MRIs) revealed significantly reduced infarct volume in the rats treated with Ade‐COMP‐Ang1 with an improvement of post‐ischemic neurological deficits compared with rats treated with Ade‐β‐gal. Moreover, compared to the rats treated with Ade‐β‐gal, the rats treated with Ade‐COMP‐Ang1 showed an increase in blood vessels, especially in the border zone adjacent to the infarction, increased number of endogenous neuronal progenitor cells in the ischemic brain, and decreased number of TUNEL‐positive cells. Taken together, COMP‐Ang1 reduced infarct volume and consequently attenuated post‐ischemic neurological deficits through enhanced angiogenesis and increased viable cell mass of neuronal cells.