Inhibition of enhancer of zest homologue 2 is a potential therapeutic target for high-MYC medulloblastoma.

MYC amplification is common in Group 3 medulloblastoma and is associated with poor survival. Group 3 and Group 4 medulloblastomas are also known to have elevated levels of histone H3-lysine 27-tri-methylation (H3K27me3), at least in part due to high expression of the H3K27 methyltransferase enhancer of zest homologue 2 (EZH2), which can be regulated by MYC. We therefore examined whether MYC expression is associated with elevated EZH2 and H3K27me3 in medulloblastoma, and if high-MYC medulloblastomas are particularly sensitive to pharmacological EZH2 blockade. Western blot analysis of low (DAOY, UW228, CB SV40) and high (DAOY-MYC, UW228-MYC, CB-MYC, D425) MYC cell lines showed that higher levels of EZH2 and H3K27me3 were associated with elevated MYC. In fixed medulloblastoma samples examined using immunohistochemistry, most MYC positive tumors also had high H3K27me3, but many MYC negative ones did as well, and the correlation was not statistically significant. All high MYC lines tested were sensitive to the EZH2 inhibitor EPZ6438. Many low MYC lines also grew more slowly in the presence of EPZ6438, although DAOY-MYC cells responded more strongly than parent DAOY cultures with lower MYC levels. We find that higher MYC levels are associated with increased EZH2, and pharmacological blockade of EZH2 is a potential therapeutic strategy for aggressive medulloblastoma with elevated MYC.

PERK Activation Promotes Medulloblastoma Tumorigenesis by Attenuating Premalignant Granule Cell Precursor Apoptosis.

Evidence suggests that activation of pancreatic endoplasmic reticulum kinase (PERK) signaling in response to endoplasmic reticulum stress negatively or positively influences cell transformation by regulating apoptosis. Patched1 heterozygous deficient (Ptch1(+/-)) mice reproduce human Gorlin's syndrome and are regarded as the best animal model to study tumorigenesis of the sonic hedgehog subgroup of medulloblastomas. It is believed that medulloblastomas in Ptch1(+/-) mice results from the transformation of granule cell precursors (GCPs) in the developing cerebellum. Here, we determined the role of PERK signaling on medulloblastoma tumorigenesis by assessing its effects on premalignant GCPs and tumor cells. We found that PERK signaling was activated in both premalignant GCPs in young Ptch1(+/-) mice and medulloblastoma cells in adult mice. We demonstrated that PERK haploinsufficiency reduced the incidence of medulloblastomas in Ptch1(+/-) mice. Interestingly, PERK haploinsufficiency enhanced apoptosis of premalignant GCPs in young Ptch1(+/-) mice but had no significant effect on medulloblastoma cells in adult mice. Moreover, we showed that the PERK pathway was activated in medulloblastomas in humans. These results suggest that PERK signaling promotes medulloblastoma tumorigenesis by attenuating apoptosis of premalignant GCPs during the course of malignant transformation.

PLK1-associated microRNAs are correlated with pediatric medulloblastoma prognosis.

PURPOSE: Medulloblastoma (MB) is the most common malignant tumor of the central nervous system (CNS) in children. Despite its relative good survival rates, treatment can cause long time sequels and may impair patients' lifespan and quality, making the search for new treatment options still necessary. Polo like kinases (PLKs) constitute a five-member serine/threonine kinases family (PLK 1-5) that regulates different stages during cell cycle. Abnormal PLKs expression has been observed in several cancer types, including MB. As gene regulators, miRNAs have also been described with variable expression in cancer. METHODS: We evaluated gene expression profiles of all PLK family members and related miRNAs (miR-100, miR-126, miR-219, and miR-593*) in MB cell lines and tumor samples. RESULTS: RT-qPCR analysis revealed increased levels of PLK1-4 in all cell lines and in most MB samples, while PLK5 was found underexpressed. In parallel, miR-100 was also found upregulated while miR-129, miR-216, and miR-593* were decreased in MB cell lines. Variable miRNAs expression patterns were observed in MB samples. However, a correlation between miR-100 and PLK4 expression was observed, and associations between miR-100, miR-126, and miR-219 expression and overall and event free survival were also evinced in our cohort. Moreover, despite the lack of association with clinico-pathological features, when comparing primary tumors to those relapsed, we found a consistent decrease on PLK2, miR-219, and miR-598* and an increase on miR-100 and miR-126. CONCLUSION: Specific dysregulation on PLKs and associated miRNAs may be important in MB and can be used to predict prognosis. Although miRNAs sequences are fundamental to predict its target, the cell type may also be consider once that mRNA repertoire can define different roles for specific miRNA in a given cell.

Telomere dysfunction and chromothripsis.

Chromothripsis is a recently discovered form of genomic instability, characterized by tens to hundreds of clustered DNA rearrangements resulting from a single dramatic event. Telomere dysfunction has been suggested to play a role in the initiation of this phenomenon, which occurs in a large number of tumor entities. Here, we show that telomere attrition can indeed lead to catastrophic genomic events, and that telomere patterns differ between cells analyzed before and after such genomic catastrophes. Telomere length and telomere stabilization mechanisms diverge between samples with and without chromothripsis in a given tumor subtype. Longitudinal analyses of the evolution of chromothriptic patterns identify either stable patterns between matched primary and relapsed tumors, or loss of the chromothriptic clone in the relapsed specimen. The absence of additional chromothriptic events occurring between the initial tumor and the relapsed tumor sample points to telomere stabilization after the initial chromothriptic event which prevents further shattering of the genome.

Overcoming resistance to Sonic Hedgehog inhibition by targeting p90 ribosomal S6 kinase in pediatric medulloblastoma.

BACKGROUND: Molecular subtyping has allowed for the beginning of personalized treatment in children suffering from medulloblastoma (MB). However, resistance inevitably emerges against these therapies, particularly in the Sonic Hedgehog (SHH) subtype. We found that children with SHH subtype have the worst outcome underscoring the need to identify new therapeutic targets. PROCEDURE: High content screening of a 129 compound library identified agents that inhibited SHH MB growth. Lead molecular target levels, p90 ribosomal S6 kinase (RSK) were characterized by immunoblotting and qRT-PCR. Comparisons were made to human neural stem cells (hNSC). Impact of inhibiting RSK with the small molecule BI-D1870 or siRNA was assessed in growth assays (monolayer, neurosphere, and soft agar). NanoString was used to detect RSK in a cohort of 66 patients with MB. To determine BI-D1870 pharmacokinetics/pharmacodynamics, 100 mg/kg was I.P. injected into mice and tissues were collected at various time points. RESULTS: Daoy, ONS76, UW228, and UW426 MB cells were exquisitely sensitive to BI-D1870 but unresponsive to SHH inhibitors. Anti-tumor growth corresponded with inactivation of RSK in MB cells. BI-D1870 had no effect on hNSCs. Inhibiting RSK with siRNA or BI-D1870 suppressed growth, induced apoptosis, and sensitized cells to SHH agents. Notably, RSK expression is correlated with SHH patients. In mice, BI-D1870 was well-tolerated and crossed the blood-brain barrier (BBB). CONCLUSIONS: RSK inhibitors are promising because they target RSK which is correlated with SHH patients as well as cause high levels of apoptosis to only MB cells. Importantly, BI-D1870 crosses the BBB, acting as a scaffold for development of more long-lived RSK inhibitors.

Neural stem cell-mediated CE/CPT-11 enzyme/prodrug therapy in transgenic mouse model of intracerebellar medulloblastoma.

Medulloblastoma is a heterogeneous diffuse neoplasm that can be highly disseminated, and is the most common malignant childhood brain tumor. Although multimodal treatments have improved survival rates for patients with medulloblastoma, these tumors are associated with high morbidity and mortality. New treatment strategies are urgently needed to improve cure rates and, importantly, to spare normal brain tissue from neurotoxicity and patients from life-long cognitive and functional deficits associated with current therapies. In numerous preclinical brain tumor models, neural stem cells (NSCs) have shown great promise as delivery vehicles for therapeutic genes. Here, we have used an established, genetically modified human NSC line (HB1.F3.CD) to deliver carboxylesterase (CE) to cerebellar tumor foci and locally activate the prodrug camptothecin-11 (CPT-11) (Irinotecan) to the potent topoisomerase I inhibitor SN-38. HB1.F3.CD NSC tumor tropism, intratumoral distribution and therapeutic efficacy were investigated in clinically relevant experimental models. Magnetic resonance imaging was used for in vivo tracking of iron nanoparticle-labeled NSCs, and to assess the therapeutic efficacy of CE-expressing HB1.F3.CD cells. As compared with controls, a significant decrease in tumor growth rate was seen in mice that received both NSCs and CPT-11 as their treatment regimen. Thus, this study provides proof-of-concept for NSC-mediated CE/CPT-11 treatment of medulloblastoma, and serves as a foundation for further studies toward potential clinical application.

Polo-like kinase 1 (PLK1) inhibition suppresses cell growth and enhances radiation sensitivity in medulloblastoma cells.

BACKGROUND: Medulloblastoma is the most common malignant brain tumor in children and remains a therapeutic challenge due to its significant therapy-related morbidity. Polo-like kinase 1 (PLK1) is highly expressed in many cancers and regulates critical steps in mitotic progression. Recent studies suggest that targeting PLK1 with small molecule inhibitors is a promising approach to tumor therapy. METHODS: We examined the expression of PLK1 mRNA in medulloblastoma tumor samples using microarray analysis. The impact of PLK1 on cell proliferation was evaluated by depleting expression with RNA interference (RNAi) or by inhibiting function with the small molecule inhibitor BI 2536. Colony formation studies were performed to examine the impact of BI 2536 on medulloblastoma cell radiosensitivity. In addition, the impact of depleting PLK1 mRNA on tumor-initiating cells was evaluated using tumor sphere assays. RESULTS: Analysis of gene expression in two independent cohorts revealed that PLK1 mRNA is overexpressed in some, but not all, medulloblastoma patient samples when compared to normal cerebellum. Inhibition of PLK1 by RNAi significantly decreased medulloblastoma cell proliferation and clonogenic potential and increased cell apoptosis. Similarly, a low nanomolar concentration of BI 2536, a small molecule inhibitor of PLK1, potently inhibited cell growth, strongly suppressed the colony-forming ability, and increased cellular apoptosis of medulloblastoma cells. Furthermore, BI 2536 pretreatment sensitized medulloblastoma cells to ionizing radiation. Inhibition of PLK1 impaired tumor sphere formation of medulloblastoma cells and decreased the expression of SRY (sex determining region Y)-box 2 (SOX2) mRNA in tumor spheres indicating a possible role in targeting tumor initiating cells. CONCLUSIONS: Our data suggest that targeting PLK1 with small molecule inhibitors, in combination with radiation therapy, is a novel strategy in the treatment of medulloblastoma that warrants further investigation.

Inhibition of tumor cell migration and invasion through knockdown of Rac1 expression in medulloblastoma cells.

Medulloblastoma is one of the common malignant brain tumors in children or young adults and its overall disease-free 5-year survival rate is approximately 50% due to tumor progression, invasion, and metastasis. This study aimed to determine whether one of Rho GTPases, Rac1 can affect the morphology, motility, and invasion of medulloblastoma cells through knockdown of Rac1 expression. Medulloblastoma Daoy cells were used to manipulate Rac1 expression using Rac1 shRNA, Rac1N17, and Rac1L61 constructs. Reverse transcriptase-PCR and western blot were used to detect expression of Rac1 mRNA and protein, respectively. Invasion and migration assays were performed to assess invasion and migration capacity of Daoy cells, respectively. The data showed that Rac1 mRNA and protein were overexpressed in Daoy cells. Deletion of Rac1 decreased the cross-linked actin network and pseudopodia and also inhibited the number of migration cells migrated or invaded to the other side of the filter compared to control cells. These data indicated that the invasion and migration in Daoy cells were inhibited by deletion of Rac1, and suggest that targeting Rac1 by Rac1 shRNA may further be evaluated and used as a potential anticancer strategy to treat medulloblastoma.

Medulloblastoma uses GABA transaminase to survive in the cerebrospinal fluid microenvironment and promote leptomeningeal dissemination.

Medulloblastoma (MB) is a malignant pediatric brain tumor arising in the cerebellum. Although abnormal GABAergic receptor activation has been described in MB, studies have not yet elucidated the contribution of receptor-independent GABA metabolism to MB pathogenesis. We find primary MB tumors globally display decreased expression of GABA transaminase (ABAT), the protein responsible for GABA metabolism, compared with normal cerebellum. However, less aggressive WNT and SHH subtypes express higher ABAT levels compared with metastatic G3 and G4 tumors. We show that elevated ABAT expression results in increased GABA catabolism, decreased tumor cell proliferation, and induction of metabolic and histone characteristics mirroring GABAergic neurons. Our studies suggest ABAT expression fluctuates depending on metabolite changes in the tumor microenvironment, with nutrient-poor conditions upregulating ABAT expression. We find metastatic MB cells require ABAT to maintain viability in the metabolite-scarce cerebrospinal fluid by using GABA as an energy source substitute, thereby facilitating leptomeningeal metastasis formation.

TORC1/2 kinase inhibition depletes glutathione and synergizes with carboplatin to suppress the growth of MYC-driven medulloblastoma.

Medulloblastoma is the most common malignant pediatric brain tumor. Tumors having high levels of c-MYC have the worst clinical prognosis, with only a minority of patients surviving. To address this unmet clinical need, we generated a human neural stem cell model of medulloblastoma that recapitulated the most aggressive subtype phenotypically and by mRNA expression profiling. An in silico analysis of these cells identified mTOR inhibitors as potential therapeutic agents. We hypothesized that the orally bioavailable TORC1/2 kinase inhibitor TAK228 would have activity against MYC-driven medulloblastoma. TAK228 inhibited mTORC1/2, decreased cell growth and caused apoptosis in high-MYC medulloblastoma cell lines. Comprehensive metabolic profiling of medulloblastoma orthotopic xenografts showed upregulation of glutathione compared to matched normal brain. TAK228 suppressed glutathione production. Because glutathione is required to detoxify platinum-containing chemotherapy, we hypothesized that TAK228 would cooperate with carboplatin in medulloblastoma. TAK228 synergized with carboplatin to inhibit cell growth and induce apoptosis and extended survival in orthotopic xenografts of high-MYC medulloblastoma. Brain-penetrant TORC1/2 inhibitors and carboplatin may be an effective combination therapy for high-risk medulloblastoma.

Protein kinase A regulatory subunit distribution in medulloblastoma.

BACKGROUND: Previous studies showed a differential distribution of the four regulatory subunits of cAMP-dependent protein kinases inside the brain, that changed in rodent gliomas: therefore, the distribution of these proteins inside the brain can give information on the functional state of the cells. Our goal was to examine human brain tumors to provide evidence for a differential distribution of protein kinase A in different tumors. METHODS: The distribution of detergent insoluble regulatory (R1 and R2) and catalytic subunits of cAMP dependent kinases was examined in pediatric brain tumors by immunohistochemistry and fluorescent cAMP analogues binding. RESULTS: R2 is organized in large single dots in medulloblastomas, while it has a different appearance in other tumors. Fluorescent cAMP labelling was observed only in medulloblastoma. CONCLUSIONS: A different distribution of cAMP dependent protein kinases has been observed in medulloblastoma.

The tumour-associated carbonic anhydrases CA II, CA IX and CA XII in a group of medulloblastomas and supratentorial primitive neuroectodermal tumours: an association of CA IX with poor prognosis.

BACKGROUND: Medulloblastomas (MBs) and supratentorial primitive neuroectodermal tumours (PNETs) are the most common highly aggressive paediatric brain tumours. In spite of extensive research on these tumours, there are only few known biomarkers or therapeutic target proteins, and the prognosis of patients with these tumours remains poor. Our aim was to investigate whether carbonic anhydrases (CAs), enzymes commonly overexpressed in various tumours including glioblastomas and oligodendrogliomas, are present in MBs and PNETs, and whether their expression can be correlated with patient prognosis. METHODS: We determined the expression of the tumour-associated carbonic anhydrases CA II, CA IX and CA XII in a series of MB/PNET specimens (n = 39) using immunohistochemistry. RESULTS: Endothelial CA II, cytoplasmic CA II, CA IX and CA XII were expressed in 49%, 73%, 23% and 11% of the tumours, respectively. CA II was detected in the neovessel endothelium and the tumour cell cytoplasm. CA IX was mainly expressed in the tumour cells located in perinecrotic areas. CA XII showed the most homogenous distribution within the tumours. Importantly, CA IX expression predicted poor prognosis in both univariate (p = 0.041) and multivariate analyses (p = 0.016). CONCLUSIONS: We suggest that CA IX should be considered a potential prognostic and therapeutic target in MBs and PNETs.

Tumor environment dictates medulloblastoma cancer stem cell expression and invasive phenotype.

The neural precursor surface marker CD133 is thought to be enriched in brain cancer stem cells and in radioresistant DAOY medulloblastoma-derived tumor cells. Given that membrane type-1 matrix metalloproteinase (MT1-MMP) expression is a hallmark of highly invasive, radioresistant, and hypoxic brain tumor cells, we sought to determine whether MT1-MMP and other MMPs could regulate the invasive phenotype of CD133(+) DAOY cells. We found that when DAOY medulloblastoma or U87 glioblastoma cells were implanted in nude mice, only those cells specifically implanted in the brain environment generated CD133(+) brain tumors. Vascular endothelial growth factor and basic fibroblast growth factor gene expression increases in correlation with CD133 expression in those tumors. When DAOY cultures were induced to generate in vitro neurosphere-like cells, gene expression of CD133, MT1-MMP, MMP-9, and MDR-1 was induced and correlated with an increase in neurosphere invasiveness. Specific small interfering RNA gene silencing of either MT1-MMP or MMP-9 reduced the capacity of the DAOY monolayers to generate neurospheres and concomitantly abrogated their invasive capacity. On the other hand, overexpression of MT1-MMP in DAOY triggered neurosphere-like formation which was further amplified when cells were cultured in neurosphere medium. Collectively, we show that both MT1-MMP and MMP-9 contribute to the invasive phenotype during CD133(+) neurosphere-like formation in medulloblastoma cells. Increases in MMP-9 may contribute to the opening of the blood-brain barrier, whereas increased MT1-MMP would promote brain tumor infiltration. Our study suggests that MMP-9 or MT1-MMP targeting may reduce the formation of brain tumor stem cells.

Targeting Upstream Kinases of STAT3 in Human Medulloblastoma Cells.

BACKGROUND: Medulloblastoma is the most common malignant brain tumor in children. Despite improvement in overall survival rate, it still lacks an effective targeted treatment strategy. The Janus family of cytoplasmic tyrosine kinases (JAKs) and Src kinases, upstream protein kinases of signal transducer and activator of transcription 3 (STAT3), play important roles in medulloblastoma pathogenesis and therefore represent potential therapeutic targets. METHODS: In this report, we examined the inhibitory efficacy of the JAK1/2 inhibitor, ruxolitinib, the JAK3 inhibitor, tofacitinib and two Src inhibitors, KX2-391 and dasatinib. RESULTS: These small molecule drugs significantly reduce cell viability and inhibit cell migration and colony formation in human medulloblastoma cells in vitro. Src inhibitors have more potent efficacy than JAK inhibitors in inhibiting medulloblastoma cell migration ability. The Src inhibitors can inhibit both phosphorylation of STAT3 and Src while JAK inhibitors reduce JAK/STAT3 phosphorylation. We also investigated the combined effect of the Src inhibitor, dasatinib with cisplatin. The results show that dasatinib exerts synergistic effects with cisplatin in human medulloblastoma cells through the inhibition of STAT3 and Src. CONCLUSION: Our results suggest that the small molecule inhibitors of STAT3 upstream kinases, ruxolitinib, tofacitinib, KX2-391, and dasatinib could be novel and attractive candidate drugs for the treatment of human medulloblastoma.

RITA downregulates Hedgehog-GLI in medulloblastoma and rhabdomyosarcoma via JNK-dependent but p53-independent mechanism.

Overactivation of the Hedgehog (HH) signaling pathway is implicated in many cancers. In this study, we demonstrate that the small molecule RITA, a p53 activator, effectively downregulates HH signaling in human medulloblastoma and rhabdomyosarcoma cells irrespective of p53. This is mediated by a ROS-independent activation of the MAP kinase JNK. We also show that in vitro RITA sensitized cells to the GLI antagonist GANT61, as co-administration of the two drugs had more pronounced effects on cell proliferation and apoptosis. In vivo administration of RITA or GANT61 suppressed rhabdomyosarcoma xenograft growth in nude mice; however, co-administration did not further enhance tumor suppression, even though cell proliferation was decreased. RITA was more potent than GANT61 in downregulating HH target gene expression; surprisingly, this suppressive effect was almost completely eliminated when the two drugs were administered together. Notably, RNA-seq demonstrated a broader response of pathways involved in cancer cell growth in the combination treatment, providing a plausible interpretation for tumor reduction in the absence of HH signaling downregulation.

Hemangioblastomas share protein expression with embryonal hemangioblast progenitor cell.

Hemangioblastomas are central nervous system (CNS) tumors of unknown histogenesis, which can occur sporadically or in von Hippel-Lindau disease. Hemangioblastomas are composed of neoplastic "stromal" cells of unknown origin, accompanied by intensive reactive angiogenesis. Failure to specify the cytologic origin of the stromal cell has precluded the development of nonsurgical therapies and limits understanding of its basic biology. We report that the stromal cells express proteins (Scl, brachyury, Csf-1R, Gata-1, Flk-1, and Tie-2) that characterize embryonic progenitor cells with hemangioblastic differentiation potential and conclude that embryonic progenitors with hemangioblast potential represent a possible cytologic equivalent of the stromal cell. We also identified a new autocrine/paracrine stimulatory loop between the receptor Tie-2 and the hypoxia-inducible factor target Ang-1, which, combined with previous observations, suggests that a variety of autocrine loops may be initiated in hemangioblastomas, depending on the differentiation status of the tumor cells and the extent of HIF downstream activation. Finally, the consistent identification of Scl in the stromal cells may help explain the unique and characteristic topographical distribution of hemangioblastomas within the CNS.

Cytogenetic and molecular biological characterization of an adult medulloblastoma.

Medulloblastoma is a malignant invasive embryonal tumor, occurring in children mainly. It is rare in adults (<1% of adult brain tumors), and so comprehensive cytogenetic and molecular biological data on adult medulloblastomas are very limited. Conventional therapies provide disappointing long-term disease control, and new therapeutic options are being tested. We performed comprehensive cytogenetic analyses of an adult medulloblastoma, WHO grade IV, using trypsin-Giemsa staining (GTG-banding), multicolor fluorescence in situ hybridization (M-FISH), and locus-specific FISH, complemented by molecular karyotyping using high-density single nucleotide polymorphism (SNP) arrays. GTG-banding of 25 metaphases revealed 31 structural chromosomal aberrations, predominantly located on chromosomes 4q, 9q, 10q, 11p, and 20q, which were confirmed by M-FISH. Two novel, so far not described translocations were found: t(4;11)(q25;p15) and t(9;20)(p23;p12). GTG-banding, locus-specific FISH, and M-FISH detected numerical changes of chromosomes 8, 14, 18, 19, 20, 21, and 22. Molecular karyotyping by SNP array confirmed chromosomal changes -2p, -10q, -16q, and -Xq and revealed de novo partial uniparental disomy 1q and 9q. Applying an upcoming therapeutic approach, we found that primary medulloblastoma cells were resistant to TRAIL, a novel anticancer cytokine, but could be efficiently sensitized by cotreatment with the proteasome inhibitor bortezomib. Bortezomib-TRAIL cotreatment may serve as a powerful therapeutic option for medulloblastoma patients.

Neurotrophin receptors and heparanase: a functional axis in human medulloblastoma invasion.

Medulloblastoma (MB) is the most common malignant brain tumor of childhood. Although modern therapy has produced five-year survival rates as high as 70% for some MB patients, this resulted in significant long-term treatment-related morbidity. The cellular mechanisms involved in metastatic spread of medulloblastoma are largely unknown. Neurotrophins (NT) comprise a family of structurally and functionally related neurotrophic factors that are critical for central nervous system (CNS) development with nerve growth factor (NGF) being the prototypic NT. NT acts through two groups of structurally unrelated neurotrophin receptors (NTR): a family of receptor tyrosine kinases (Trks, mainly TrkA, TrkB, and TrkC) and a tumor necrosis factor receptor (TNFR)-like molecule called p75NTR TrkC expression is a good prognostic indicator for MB. TrkC binds only to neurotrophin-3 (NT-3) whereas p75 binds to all NT family members. Importantly, little is known about the biological functions of p75 in primitive neuroectodermal tumors such as MB. In contrast, NT-regulated heparanase (HPSE) is a unique extracellular matrix-degrading enzyme known to be associated with tumor progression in a wide variety of cancers. However, HPSE roles in MB invasive pathways have not been investigated. We provide evidence of a differential expression of HPSE in newly-developed medulloblastoma cell lines. Secondly, we show a correlation between HPSE expression and the invasive properties of these medulloblastoma lines. Thirdly, by performing investigations to elucidate prognostic implications of HPSE and TrkC/p75NTR expression in MB, we demonstrate a correlation between p75NTR and HPSE expression. Finally, by using antibodies specific to TrkC and immunohistochemistry (IHC) we prove that IHC scores reveal a significant expression of HPSE in 76% of MB tissues from children aged 3 years and older. Taken together, our data provide evidence that HPSE functionality, in a context linked to TrkC and p75NTR activation, may play critical roles in medulloblastoma tumor invasion and progression.

Association of cavernous malformation within vestibular schwannoma: immunohistochemical analysis of matrix metalloproteinase-2 and -9.

A 65-year-old man presented with a rare case of cavernous malformation with hemorrhage located within vestibular schwannoma. He had suffered hearing impairment for 20 years, and was admitted to our hospital with vertigo and ataxic gait. Neurological examination revealed hearing loss, facial nerve paresis, and left cerebellar ataxia. Magnetic resonance imaging demonstrated a left vestibular schwannoma 35 mm in diameter, as well as a heterogeneous area associated with hypointense rim within the tumor, indicating intratumoral hemorrhage. Subtotal removal of the tumor together with the fibrously encapsulated hematoma was performed through a left retrosigmoid craniotomy. Histological examination of the surgical specimen revealed cavernous malformation within vestibular schwannoma. Immunohistochemistry for matrix metalloproteinase (MMP)-2 and -9, and tissue inhibitors of metalloproteinase-2 showed strong expression in the endothelial cells of the cavernous malformation, but not in the interstitial structures. His symptoms significantly improved after surgery and he underwent gamma-knife therapy for the residual tumor. Cavernous malformations may show dynamic characteristics such as repeated hemorrhage and de novo formation. MMP-2 and -9, which are implicated in angiogenesis and hemorrhage, may be upregulated in such tumors.