In conclusion, downregulation of miR-124 and miR-383 is a frequent event in MB. Restoration of miR-124 and miR-383 inhibited cell growth and cell cycle progression in MB, suggesting these miRNAs harbor growth suppressor function. In addition, this study demonstrates SLC16A1 and PRDX3 are the direct targets of miR-124 and miR-383, respectively. Together, these data shed new light on miR-124 and miR-383 in MB pathogenesis, and suggest that miR-124/SLC16Al and miR-383/PRDX3 pathways are potential therapeutic targets for treatment of MB. / Medulloblastoma (MB) is an invasive embryonal tumor of the cerebellum, accounting for ∼20% of all primary pediatric brain tumors. The overall survival rate is 60--70% in standard-risk MB patients, but merely ∼30% in high-risk group. Patients who survive often suffer from long-term neurologic and cognitive deficits. New therapy is needed to reduce the mortality rate and to improve the quality of life of survivors. Understanding the molecular pathogenesis of MB is critical to the development of efficacious therapeutic treatment. / MicroRNAs (miRNAs) are short non-protein-coding RNAs that function in diverse biological processes through negative regulation on gene expression at the post-transcriptional level. Accumulative evidence indicates that miRNAs play an important role in the development of human cancers, with their deregulation resulting in altered activity of downstream tumor suppressors, oncogenes and other signaling molecules. / The aim of my project is to identify and characterize deregulated miRNAs located on chromosome 8p in MB. Our group has previously identified a minimally deleted region on 8p22-23.1 and partial or interstitial deletions at 8p22-23.2 in MBs. Despite extensive investigation, no promising candidate genes were identified in these. I questioned if miRNAs (miR-124, miR-383 and miR-320) were the targets on chromosome 8p. Quantitative expression analysis of 29 MBs revealed that miR-124 and miR-383 were downregulated in 72% and 79% of tumors, respectively, compared to normal cerebella. In contrast miR-320 expression was variable. Ectopic expression of miR-124 and miR-383 in MB cell lines (DAOY and ONS-76) showed significant growth inhibition. Cell cycle profiling revealed miR-124 and miR-383 inhibited cell cycle progression and induced apoptosis. These results suggest that miR-124 and miR-383 are potential growth suppressors. / To identify gene targets of miR-124, computational analysis was carried out. Twelve candidate genes predicted as miR124 target were selected for analysis. One candidate gene, SLC16A1, showed downregulation at transcript and protein levels after miR-124 transfection. Luciferase reporter assay demonstrated that miR-124 interacted at the 3' untranslated region of SLC16A1. These results suggest that miR-124 negatively regulates SLC16A1. Expression analysis further revealed that overexpression of SLC16A1 was common in MBs. / To identify miR-383 targets, global gene expression analysis and computational approach were applied. Two genes (PRDX3 and RBMS1 ) showed downregulation upon miR-383 transfection. Reporter assay confirmed that miR-383 interacted at 3' untranslated regions of these genes, suggesting that PRDX3 and RBMS1 are targets ofmiR-383. / Li, Ka Wai Kay. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 236-293). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Ng, Hin Yi Winnie. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 137-140). / Abstracts in English and Chinese. / Acknowledgements --- p.ii / List of Tables --- p.iii / List of Figures --- p.iv / Abstract in English --- p.vi / Abstract in Chinese --- p.ix / Table of Contents --- p.xi / Chapter CHAPTER 1: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Medulloblastoma (MB) --- p.1 / Chapter 1.1.1 --- Definition of Medulloblastoma --- p.1 / Chapter 1.1.2 --- Pathological Classification --- p.2 / Chapter 1.1.3 --- Current Treatment --- p.3 / Chapter 1.1.4 --- Molecular Pathology --- p.4 / Chapter 1.1.5 --- Molecular Classification of MB --- p.7 / Chapter 1.2 --- MicroRNAs (miRNAs) --- p.9 / Chapter 1.2.1 --- Biogenesis --- p.9 / Chapter 1.2.2 --- Functions --- p.10 / Chapter 1.2.3 --- MicroRNAs & Cancers --- p.10 / Chapter 1.2.4 --- Aberrant Expressions of MicroRNAs in Medulloblastoma --- p.12 / Chapter 1.2.5 --- MiR-106b-25 Cluster in MB --- p.13 / Chapter 1.2.6 --- miR-106b-25 Cluster in Regulating Target Genes --- p.15 / Chapter 1.2.7 --- Application of Regulatory miRNAs --- p.16 / Chapter 1.3 --- Target Gene Identification --- p.18 / Chapter 1.3.1 --- Recent Molecular Advances in Target Gene Identification --- p.18 / Chapter 1.3.2 --- Importance of Target Gene Identification --- p.19 / Chapter CHAPTER 2: --- AIMS OF STUDY --- p.21 / Chapter CHAPTER 3: --- COMPUTATIONAL TARGET PREDICTION --- p.23 / Chapter 3.1 --- Introduction- Computational Approach --- p.23 / Chapter 3.2 --- Methods --- p.27 / Chapter 3.2.1 --- Prediction Algorithms --- p.27 / Chapter 3.2.1.1 --- EIMMo2 --- p.27 / Chapter 3.2.1.2 --- miRDB --- p.27 / Chapter 3.2.1.3 --- miR-Tar-miRanda --- p.28 / Chapter 3.2.1.4 --- miR-Tar-RNAhybrid --- p.28 / Chapter 3.2.1.5 --- Diana-microT --- p.29 / Chapter 3.2.1.6 --- Pic-Tar --- p.29 / Chapter 3.2.1.7 --- TargetScan 4.2 --- p.29 / Chapter 3.2.2 --- Cell Culture --- p.30 / Chapter 3.2.2.1 --- Cell Lines --- p.30 / Chapter 3.2.2.2 --- Cell Counts --- p.31 / Chapter 3.2.3 --- Transfections --- p.31 / Chapter 3.2.3.1 --- Transfection of MicroRNA Inhibitors --- p.31 / Chapter 3.2.3.1.1 --- Transfection Efficiency of Lipofectamine2000 --- p.32 / Chapter 3.2.3.1.2 --- Transfection of MicroRNA Inhibitors for Real-time PCR --- p.32 / Chapter 3.2.3.1.3 --- Transfection of MicroRNA Inhibitors for Western Blotting --- p.33 / Chapter 3.2.3.2 --- Co-transfection of Plasmid and MicroRNA Inhibitors --- p.33 / Chapter 3.2.3.2.1 --- Blocking Efficiency of MicroRNA Inhibitors --- p.33 / Chapter 3.2.3.2.2 --- Co-transfection of Target Gene Expression Vector and MicroRNA Inhibitors --- p.34 / Chapter 3.2.4 --- Real-time PCR Amplification --- p.35 / Chapter 3.2.4.1 --- Total RNA Extraction from Cell Lines --- p.35 / Chapter 3.2.4.2 --- Stemloop miRNA Taqman qRT-PCR Analysis --- p.36 / Chapter 3.2.4.3 --- Reverse Transcription --- p.37 / Chapter 3.2.4.4 --- Real-time PCR Target Gene Expression --- p.38 / Chapter 3.2.5 --- Cloning of Potential Target Genes into pMIR Luciferase Expression Vector --- p.39 / Chapter 3.2.5.1 --- High-Fidelity PCR Amplification of yUTRs --- p.41 / Chapter 3.2.5.2 --- PCR Purification of Amplified PCR Product --- p.42 / Chapter 3.2.5.3 --- Restriction Enzyme Digestions --- p.42 / Chapter 3.2.5.4 --- Ligation of 3'UTR to Expression Vector --- p.43 / Chapter 3.2.5.5 --- Transformation --- p.43 / Chapter 3.2.5.6 --- Preparation of the Cloned Plasmid --- p.43 / Chapter 3.2.5.7 --- Sequencing of the Cloned Plasmid --- p.44 / Chapter 3.2.6 --- Site-directed Mutagenesis --- p.45 / Chapter 3.2.7 --- Dual-Luciferase Assay --- p.47 / Chapter 3.2.8 --- Western Blot Analysis --- p.47 / Chapter 3.3 --- Results --- p.49 / Chapter 3.3.1 --- Expression Levels of miR-106b-25 Cluster in MB Cell Lines --- p.49 / Chapter 3.3.2 --- Evaluation of Transfection Efficiency Using Lipofetamine2000 --- p.51 / Chapter 3.3.3 --- Blocking Efficiency of MicroRNA Inhibitors --- p.52 / Chapter 3.3.4 --- Target Prediction List --- p.53 / Chapter 3.3.5 --- Recognition Sites of Potential Targets --- p.55 / Chapter 3.3.6 --- Expression Levels of ZNFX1 in MB Cell Lines --- p.56 / Chapter 3.3.7 --- Transcriptional Regulation of ZNFXl and DNAJB12 --- p.57 / Chapter 3.3.8 --- Verification of Potential Target Genes --- p.59 / Chapter 3.3.9 --- Identification of Critical Target Sites --- p.61 / Chapter 3.3.10 --- Effects of Anti-microRNA Inhibitors on ZNFX1 Protein Levels --- p.66 / Chapter 3.4 --- Discussion --- p.67 / Chapter CHAPTER 4: --- EXPERIMENTAL APPROACH IN INDENTIFYING POTENTIAL TARGETS --- p.77 / Chapter 4.1 --- Introduction- Experimental Approach --- p.74 / Chapter 4.2 --- Methods --- p.79 / Chapter 4.2.1 --- Isolation of cDNA Clone Library --- p.79 / Chapter 4.2.1.1 --- Preparation of Cytoplasmic Extracts --- p.79 / Chapter 4.2.1.2 --- Reverse Transcription Using Endogenous miRNA as Primers --- p.81 / Chapter 4.2.1.3 --- Collection of Polynucleotides --- p.82 / Chapter 4.2.1.4 --- Synthesis of Second-strand cDNAs --- p.82 / Chapter 4.2.1.5 --- PCR Purification of Double-stranded cDNAs --- p.83 / Chapter 4.2.1.6 --- Restriction Endonuclease Digestion --- p.84 / Chapter 4.2.1.7 --- Ligation to Adaptor --- p.85 / Chapter 4.2.1.8 --- PCR Amplification with Biotin-labelled miRNA PCR Primers --- p.86 / Chapter 4.2.1.9 --- Capture of Biotin-labelled PCR Fragments --- p.88 / Chapter 4.2.1.10 --- Introducing NotI Recognition Sequences --- p.88 / Chapter 4.2.1.11 --- Cloning into the pCR2.1 Vector --- p.89 / Chapter 4.2.1.12 --- Ligation of the cDNA Fragments and the pCR2.1 Vector --- p.90 / Chapter 4.2.1.13 --- Transformation --- p.90 / Chapter 4.2.1.14 --- Preparation of Purified Plasmids --- p.91 / Chapter 4.2.1.15 --- Sequencing Analysis of the cDNA Clone Library --- p.91 / Chapter 4.2.2 --- Real-time PCR Target Gene Expression in Cell Lines --- p.92 / Chapter 4.2.3 --- Real-time PCR Target Gene Expression Upon Inhibition of miR-106b --- p.92 / Chapter 4.2.4 --- Cloning of Potential Target Genes into pMIR Luciferase Expression Vector --- p.93 / Chapter 4.2.5 --- Site-directed Mutagenesis --- p.94 / Chapter 4.2.6 --- Luciferase Reporter Assay --- p.94 / Chapter 4.3 --- Results --- p.95 / Chapter 4.3.1 --- Sequencing Analysis of the cDNA Clone Library --- p.95 / Chapter 4.3.2 --- Expression Levels of Candidate Genes in MB Cell Lines --- p.100 / Chapter 4.3.3 --- Effects of Anti-miR-106b Inhibitors on 3'UTR of Target Genes --- p.101 / Chapter 4.3.4 --- Verification of Candidate Genes --- p.103 / Chapter 4.3.5 --- Verification of Target Sites with Site-directed Mutagenesis --- p.104 / Chapter 4.4 --- Discussion --- p.107 / Chapter CHAPTER 5: --- FUNCTIONAL ASSAYS --- p.111 / Chapter 5.1 --- Introduction- Functional Investigation of miR-106b-25 Cluster --- p.111 / Chapter 5.2 --- Methods --- p.113 / Chapter 5.2.1 --- Cell Culture --- p.113 / Chapter 5.2.2 --- Over-expression of miR-106b Mimic --- p.113 / Chapter 5.2.3 --- MTT Assay --- p.114 / Chapter 5.2.4 --- IC50 of Cisplatin --- p.115 / Chapter 5.2.5 --- MTT Assay with Cisplatin Treatment --- p.115 / Chapter 5.2.6 --- Cell Cycle --- p.116 / Chapter 5.2.7 --- BrdU Cell Proliferation Assay --- p.117 / Chapter 5.2.8 --- Wound Healing Assay --- p.117 / Chapter 5.3 --- Results --- p.119 / Chapter 5.3.1 --- Effects of Inhibition of miR-106b-25 Cluster on Cell Growth. --- p.119 / Chapter 5.3.2 --- Cell Cycle Distribution Analysis --- p.121 / Chapter 5.3.3 --- Sensitivity to Cisplatin --- p.123 / Chapter 5.3.4 --- Cell Proliferation Assay --- p.124 / Chapter 5.3.5 --- Cell Motility --- p.126 / Chapter 5.3.6 --- Efficiency of Over-expression Using miR-106b Mimic --- p.129 / Chapter 5.3.7 --- Effects of miR-106b on Cell Growth --- p.130 / Chapter 5.4 --- Discussion --- p.131 / Chapter CHAPTER 6: --- CONCLUSION --- p.135 / REFERENCE --- p.137

In human infection, herpes simplex virus (HSV) navigates two distinct life cycles; lytic and latent. The latent cycle takes place in sensory neurons, and is characterized as a dormant period punctuated by stress-induced episodes of viral reactivation. Understanding the mechanisms by which HSV latency and reactivation occur has been hindered by the lack of a model that faithfully recapitulates the environment of a human sensory neuron. Systems ranging from rat neurons to human fibroblasts have been developed to host HSV latency, however few available models have been able to investigate the role of human neuron-specific factors. To address this need, human medulloblastoma tumour cell lines, which derive from neuronal precursor cells, were differentiated and examined for their ability to host the HSV latency-reactivation cycle—in a manner similar to the differentiated PC-12 cell model. ONS-76 and UW228 medulloblastoma cell lines were screened for differentiation capacity. The differentiated cells were demonstrated to possess neuronal character as several neuron-specific proteins were found to be expressed. Differentiated ONS-76 cells were not compatible with hosting HSV latency, however, infection with a viral mutant impaired for lytic cycle initiation exhibited a deviant pattern of gene expression that resembles what has been observed in reactivation. Differentiated UW228 cells were found to host a low frequency, stable infection with the HSV mutant, characterized by the absence of infectious virus and viral lytic gene expression in the presence of persisting viral DNA. This DNA could further be induced to re-enter the lytic cycle through heat shock treatment and removal of differentiating agents from cell cultures. These results depict differentiated medulloblastoma cells as a novel tool in the study of HSV latency and reactivation, as these cells derive from the central nervous system and provide a new cellular perspective through which HSV biology can be viewed.

Cancer is a fearful, deadly disease. Currently there is almost no cure. The reason is that the disease mechanisms are hardly understood to humans. This in turn is because of the complex molecular activities that underlie cancer processes. Some variables of these processes, such as gene expressions, copy number profiles and point mutations, recently became measurable in high-throughput. However, these data are massive and non-readable even to experts. A lot of efforts are being made to develop engineering tools for the analysis and interpretation of these data, for various purposes. In this thesis, we focus on addressing the problem of individuality in cancer. More specifically, we are interested in knowing the subgroups of processes in a cancer, called subtypes. This problem has both theoretical and practical implications. Theoretically, classification of cancer patients represents an understanding of the disease, and may help speed up drug development. Practically, subgroups of patients can be treated with different protocols for optimal outcomes. Towards this end, we propose an approach with two specific aims: performing subtypes for a given set of high-throughput data, and identifying candidate genes (called drivers) that drive the subtype-specific processes. First, we assume that a subtype has a distinctive process, compared not just with normal controls, but also with other cases of the same cancer. The process is characterized with a set of differentially expressed genes uniquely found in the corresponding subtype. Based on this assumption, we develop a signature based subtyping algorithm, which on the one hand divides a set of cases into as many subtypes as possible, while on the other hand merges subtypes that have too small a signature set. We applied this algorithm to datasets of the pediatric brain tumor of medulloblastoma, and found no more than three subtypes can meet the above criteria. Second, we explore subtype patterns of the copy number profiles. By regarding all events on a chromosome arm as a single event, we quantize the copy number profiles into event profiles. An unsupervised decision tree training algorithm is specifically designed for detecting subtypes on these profiles. The trained decision tree is intuitive, predictive, easy to implement and deterministic. Its application to datasets of medulloblastoma reveals interesting subtype patterns characterized with co-occurrence of CNA events. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Medulloblastoma is the most common malignant central nervous system (CNS) tumor in childhood. The cranio-spinal radiation (CSR) required to treat this disease results in long-term cognitive and neurologic impairments. Medulloblastoma was recently categorized into four genetic subgroups (WNT, SHH, Group 3, and Group 4). This study examined neuropsychological and intellectual functioning in 91 medulloblastoma patients (41 Group 4; 20 Group 3; 18 SHH; 12 WNT) following treatment, and examined the impact of several medical, treatment and demographic factors on functioning over time. Longitudinal growth curve analyses revealed hydrocephalus most clearly predisposes to poor neuropsychological functioning. Results also indicate medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. All subgroups experience intellectual declines following treatment; however, comparing between subgroups revealed Group 4 performs most poorly, and Group 3 has the best overall intellectual outcome. Lastly, qualitative analyses suggest treatment with a larger CSR dose may contribute to poor intellectual functioning.

Medulloblastoma is the most common malignant central nervous system (CNS) tumor in childhood. The cranio-spinal radiation (CSR) required to treat this disease results in long-term cognitive and neurologic impairments. Medulloblastoma was recently categorized into four genetic subgroups (WNT, SHH, Group 3, and Group 4). This study examined neuropsychological and intellectual functioning in 91 medulloblastoma patients (41 Group 4; 20 Group 3; 18 SHH; 12 WNT) following treatment, and examined the impact of several medical, treatment and demographic factors on functioning over time. Longitudinal growth curve analyses revealed hydrocephalus most clearly predisposes to poor neuropsychological functioning. Results also indicate medulloblastoma subgroups have heterogeneous intellectual outcomes following treatment. All subgroups experience intellectual declines following treatment; however, comparing between subgroups revealed Group 4 performs most poorly, and Group 3 has the best overall intellectual outcome. Lastly, qualitative analyses suggest treatment with a larger CSR dose may contribute to poor intellectual functioning.

BACKGROUND: Medulloblastoma (MB) is the most common malignant brain tumor in children, accounting for 15-20% of all pediatric brain tumors. In patients with MB, prognosis depends heavily on the molecular makeup of the tumor. New genomic approaches over the last decade have enabled researchers to sub-classify MB based on differences in the transcriptome: WNT, Sonic hedgehog (SHH), Group 3 (MYC-amplified), and Group 4 (heterogeneous). SHH tumors represent a third of all MB cases, and small-molecule inhibitors have already been developed that target SHH signaling. Most notably, vismodegib has shown great promise in the treatment of MB and other SHH-driven cancers by targeting Smoothened (SMO), an upstream regulator of GLI activity. However, most patients who had initially responded to the drug quickly acquired point mutations in SMO that led to treatment resistance. In addition, patients who harbored mutations downstream of SMO had no response to treatment and were found to be intrinsically resistant. Although most patients with SHH-MB can be cured, current treatments often require broad base therapies, such as radiation and chemotherapy, which can have harmful and long-lasting side effects. These observations underscore the need for less toxic, more targeted therapies that act at the level of the GLI family of transcription factors themselves. However, as transcription factors are generally considered undruggable, Dr. Robbins’ group at the University of Miami Miller School of Medicine sought to address this need by using focused screens of siRNAs or small molecules that target epigenetic GLI regulators. They identified several candidates that act as readers, writers, and/or erasers of protein acetylation and methylation and showed that a subset of these candidates act downstream of SMO to attenuate GLI signaling (data not yet published). Bromodomain- and Plant Homeodomain-linked Zinc Finger-containing Protein 1 (BRPF1) was one of these candidates and further analysis revealed that its knockdown reduced Gli1 expression by more than 50%. Recent studies link BRPF1 to cerebellar development and tumor formation in SHH-MB and may be suggestive of its role as a negative regulator. OBJECTIVES: We sought to compare basal levels of Brpf1 expression in normal versus MB in mice; to characterize Brpf1 knockdown versus overexpression in SHH cell lines; and to determine if BRPF1 merits further investigation as a candidate for future drug targeting therapies in MB and other SHH-driven cancers. METHODS: We used RT-qPCR and immunoblotting analysis to look at Brpf1 expression in Ptch+/- and adult wild-type mice. cDNA and protein samples were donated by colleagues in the lab. We also grew and maintained SHH Light2 cells in culture and then used these cells to carry out siRNA and plasmid DNA transfections. RNA extraction, RT-PCR, and RT-qPCR were used to examine transfection efficiency and its effect on Gli1 expression. RESULTS: Brpf1 levels were higher in SHH-MB compared to normal cerebellum. However, BRPF1 proteins were not detected in either normal or tumor samples. Brpf1 knockdown in Light2 cells correlated with an overall decrease in Gli1 expression while overexpression had no obvious affect on Gli1 expression. CONCLUSIONS: Our findings suggest that BRPF1 may function as a positive regulator of GLI activity. Recent studies verify this claim at least partially stating that BRPF1 acts as both a positive and negative regulator of gene expression depending on the context. Thus, before we can draw any final conclusions, more research is needed to look at BRPF1 in the specific context of the SHH pathway and developing cerebellum.

<p>Medulloblastoma (MB) remains incurable in one third of patients despite aggressive multi-modality standard therapies. The heterogeneity of MB molecular subtypes as well as the failure of standard therapies to treat metastatic or recurrent disease necessitates more potent targeted approaches that minimize collateral toxicity. Immunotherapy presents a promising strategy by specifically targeting cancer cells and to date, there have been few successful immunologic applications targeting MB. Emerging evidence from integrated genomic studies has suggested MB variants arise from deregulation of pathways affecting the proliferation and differentiation of progenitor cell populations within the developing cerebellum. To test the developing cerebellum as a source of tumor rejection antigens, we adapted two animal models of MB recapitulating human Sonic Hedgehog (SHH) and Group 3 tumors for immunotherapeutic evaluation. Immunologic characterization of these murine models revealed subtype-specific differences in the tumor microenvironment and a differential response to immune checkpoint blockade. We used total embryonic RNA from the developing mouse cerebellum (P5) to generate antigen-specific T cells and confirmed the immunogenicity of targeting developmentally regulated antigens in vitro. Developmental antigen-specific T cells produced high levels of Th1-type cytokines in response to two immunologically distinct subtypes of MB. Interestingly, developmental antigen specific T cells did not show any cross reactivity with the normal brain or subsequent stages of the developing brain after P5. Targeting developmental antigens conferred a significant survival benefit and long term cures in intracranial treatment models of SHH and Group 3 tumor bearing animals. We additionally tested whether the enrichment of select developmental antigens through the exclusion of normal brain transcripts would potentiate antitumor responses in both animal models. Finally, we evaluated the relevance of targeting fetal antigens across human MB subtypes. Our studies demonstrate that developmental antigens can safely target multiple MB subtypes and can be further refined to preferentially target individual subgroups. Further studies targeting immunogenic developmental antigens and leveraging this strategy with specific immune modulatory interventions represent a novel approach at utilizing patient molecular classification information to mediate safe and effective immunotherapy.</p> / Dissertation

Meduloblastoma é o câncer do Sistema Nervoso Central mais comum em crianças entre 0 e 4 anos. Ele é originado de células precursoras neuronais, que falharam em se diferenciar e continuaram a se proliferar. A proteína SAM68 está desregulada em várias linhagens de células de cânceres humanos e é uma proteína que pode estar envolvida em uma ampla gama de vias de sinalização importantes, incluindo metabolismo de RNA, regulação do ciclo celular, apoptose, regulação de splicing e transdução de sinal. Em células-tronco neurais (NSC), níveis elevados de SAM68 levam a uma redução importante na proliferação celular. Contudo, na maioria dos cânceres estudados até o momento, a SAM68 está envolvida com progressão tumoral. Com este trabalho, buscou-se entender o envolvimento de SAM68 na proliferação e morte de células de meduloblastoma. Por meio da análise de expressão transcricional e proteica, do silenciamento de SAM68, análise de apoptose por citometria de fluxo e análise de proliferação por índice mitótico e incorporação de EdU, observou-se que, em linhagens de meduloblastoma, a SAM68 está envolvida com proliferação, mas não com apoptose. Seu funcionamento em meduloblastoma é similar aos resultados obtidos com NCS do que com outros tipos de câncer, visto que o silenciamento dessa proteína favorece a proliferação das células de meduloblastoma. Em vista dos resultados aparentemente conflitantes, tendo um papel mais semelhante a um supressor tumoral, porém sendo altamente expressa em meduloblasoma, sugeriram-se algumas hipóteses, que foram apenas inicialmente testadas neste trabalho, mas precisam ser aprofundadas em trabalhos futuros / SAM68 is considered a prototype of STAR proteins (Signal Transducers and Activators of RNA protein), that are involved in the signal translation and RNA activation. In cancer, the intracellular levels of Sam68 are crucial to the progression of the disease. Recent observations indicate Sam68 with both pro-oncogenic and tumor suppressor activities, depending on the type of cell. Here, we analyzed SAM68 expression by real time PCR and western blot, proliferation of cell with and without SAM68 by mitotic index and incorporation of EdU and cell death by flux cytometry to define the relevance of the presence of SAM68 to cell proliferation and death. We found that proliferation of medulloblastoma cell lines are affected for absent SAM68, but not apoptosis. Because the contrast of an action similar to a tumor suppressor and a high expression level, we hypothesized that the increase of SAM68 levels is important during the neuronal development, regulating splicing variants. Our results allied to some literature data corroborate this hypothesis

Recent discoveries enabled us to divide medulloblastoma into molecular sub-groups and uncover novel mutations in these tumors. However, except for superior survival of the WNT sub-group, the prognostic and therapeutic implications of these observations remain unclear. TP53 mutations which confer radioresistance revealed conflicting clinical relevance in different studies. We hypothesized that the effect of TP53 mutations on survival is modulated through molecular sub-grouping. This is especially important since therapeutic targeting of WNT can be achieved with administration of lithium. Here we first confirmed that TP53 mutant tumors confers unfavorable outcome only in SHH subgroup, but not in WNT. We demonstrated that while TP53 mutations cause radioresistance, activation of WNT/β-catenin signaling radiosensitizes medulloblastoma cells. We demonstrated that lithium activates the WNT pathway and effectively sensitize medulloblastoma cells to radiation. Furthermore, lithium did not sensitize normal neural stem cells to radiation, suggesting its potential as an effective radiosensitizer for medulloblastoma.