INTRODUÇÃO: A combinação de radioterapia e altas doses de cisplatina no tratamento do meduloblastoma tem se mostrado causa de importante ototoxicidade. Com a introdução da técnica de intensidade modulada do feixe (IMRT), tornou-se possível diminuir a dose média de radiação no aparelho auditivo. OBJETIVOS: O objetivo é determinar se com a radioterapia com reforço de dose com IMRT, é possível atingir índices menores de perda auditiva e se há um limite de dose no ouvido para a mesma. Analisar também se o volume de ouvido contornado durante o planejamento inverso influencia o resultado. MÉTODO: Quarenta e um pacientes com meduloblastoma (idade mediana, 10 anos) com audição normal ao início da radioterapia com IMRT foram avaliados retrospectivamente. O último seguimento e a última audiometria realizada após o término da radioterapia foram considerados. A função auditiva foi graduada em uma escala de 0 a 4 de acordo com os critérios de toxicidade do Pediatric Oncology Group (POG). As doses mínima, máxima, média e mediana recebidas pelo aparelho auditivo, bem como o volume contornado no planejamento do IMRT foram correlacionados com o grau de função auditiva. Foi realizada análise univariada e multivariada dos dados. RESULTADOS: O seguimento mediano foi de 41 meses (12,8 a 71) para avaliação audiométrica e 44 meses (14-72) para a sobrevida global. As doses medianas mínima, máxima, média e mediana recebidas pelo aparelho auditivo foram respectivamente de: 3785 (589,4 a 4758,2), 4832,5 (3724 a 5447,9), 4366,5 (2808,5 a 5097,3) e 4360,5 (2878 a 5031,1). Sete pacientes (17%) apresentaram perda auditiva graus 3 e 4. A análise univariada entre as variáveis não mostrou diferença com significância estatística, exceto para a dose de cisplatina (P < 0,03). Na análise multivariada com regressão logística, a dose mediana no aparelho auditivo foi um fator significativo para a perda auditiva graus 3 e 4 (P < 0,01), ao passo que a dose cumulativa de cisplatina apresentou tendência à perda graus 3 e 4 (P = 0,075). Não houve correlação entre o volume contornado no planejamento a perda auditiva. Perda auditiva graus 3 e 4 foi incomum com dose mediana no aparelho auditivo menor que 42 Gy (P = 0,063) e dose cumulativa de cisplatina abaixo de 375 mg/m² (P < 0,01). Nenhum paciente que recebeu carboplatina em substituição à cisplatina apresentou perda auditiva grave. Não houve associação, com significância estatística, entre as variáveis analisadas e a ototoxicidade, quando estes pacientes foram excluídos da análise. Quatro pacientes morreram e dois apresentaram recidiva no momento do estudo, levando a uma sobrevida global de 90% e uma sobrevida livre de doença de 85% em 44 meses. CONCLUSÕES: Os resultados mostram que o tratamento com IMRT leva a uma baixa taxa de perda auditiva grave, mesmo com um seguimento maior, o que é consistente com outros estudos. Acreditamos ser seguro contornar somente a cóclea e que uma dose mediana para a mesma deve ser mantida abaixo de 42 Gy. A quimioterapia com cisplatina continua a ter um papel importante no tratamento, no entanto a dose cumulativa não deve exceder 375 mg/m². A sobrevida foi impressionante neste estudo, uma vez que 21 (51,2%) foram classificados como alto risco / INTRODUCTION: The combination of radiation therapy and cisplatin chemotherapy for the treatment of medulloblastoma is a known cause of important ototoxicity. With the introduction of intensity-modulated radiation therapy (IMRT), it became possible to deliver less radiation to the auditory apparatus. PURPOSE: To determine if boost radiotherapy with IMRT can achieve a lower rate of hearing loss and if theres a cutoff dose for it. Also, to analyze whether the auditory apparatus volume contoured in inverse planning influences the outcome. METHODS: Forty-one pediatric medulloblastoma patients (median age, 10 years) with normal hearing at the time of radiation with IMRT were retrospectively evaluated. The last audiogram and follow-up from the completion of radiation were considered. Hearing function was graded on a scale 0 to 4 according to Pediatric Oncology groups toxicity criteria. Minimum, maximum, mean and median doses to the inner ear and its volume contoured in IMRT planning, as well the cisplatin dose were recorded and correlated with hearing function. Univariate and multivariate data analysis were performed. RESULTS: The median follow-up was 41 months (range 12.8-71.0 months) for audiometric evaluation and 44 months (range 14-72 months) for survival. Median doses for minimum, maximum, mean and median in the inner ear were respectively: 3785 (range, 589.4 to 4758.2), 4832.5 (range 3724 to 5447.9), 4366.5 (range 2808.5 to 5097,3) and 4360,5 (range 2878 to 5031,1). Seven patients (17%) have experienced Grade 3 or 4 hearing loss. Univariate analysis showed no difference among the variables with statistical significance, except for cisplatin dose (P < 0.03). In multivariate analysis with logistic regression, median dose in inner ear was a significant factor for hearing loss grade 3 or 4 (P < 0,01), meanwhile cisplatin dose had a trend to hearing loss grade 3 or 4 (P = 0.075). There was no relationship between the auditory apparatus volume contoured in planning and hearing loss. Grade 3 or 4 hearing loss were uncommon with median dose to the inner ear bellow 42 Gy (P = 0.063) and cisplatin dose less than 375 mg/m² (P < 0.01). None of the patients who received carboplatin in lieu of cisplatin had severe hearing loss. There was no statistically significant association between ototoxicity and the variables, when these patients were excluded from the analysis. Four patients died and two have recurred at the time of the study with a 90% overall survival rate and 85% disease free survival in 44 months. CONCLUSIONS: Our findings shows that IMRT treatment leads to a low rate of serious hearing loss even with a longer follow-up, which is consistent with others trials. We believe that is safe to contour only the cochlea and that a median dose to it should be kept below 42Gy. Cisplatin chemotherapy continues to have an important role in treatment, however doses should not exceed 375 mg/m². Survival rates were impressing in this trial given the fact that 21 (51.2%) patients were classified as high risk

O meduloblastoma (MB) é o tumor cerebral maligno mais comum na infância. A formação/progressão desta neoplasia foi associada a alterações moleculares, que inclui a desregulação da via de sinalização Wingless (Wnt), responsável pelo desenvolvimento embrionário. Além disso, as proteínas da família Aurora-quinases (A, B e C) têm sido amplamente estudadas, uma vez que a Aurora A e B foram encontrados hiperexpressas em diversas neoplasias, como o MB. Estudos recentes mostraram que existe uma associação entre a Via Wnt e as Aurora-quinases. No entanto, poucos trabalhos foram realizados para confirmar essa associação. Ademais, não existem trabalhos que relatem os efeitos do AMG900, um pan-inibidor de aurora-quinases, em MB, dando enfoque na regulação da via Wnt. Assim, o objetivo deste trabalho foi avaliar a modulação da via Wnt pelo inibidor AMG900 nas linhagens celulares de meduloblastoma pediátrico. Foram realizados os ensaios de PCR convencional, sequenciamento, qRT-PCR, transfecção transiente, ensaio clonogênico, Western Blot e ciclo celular. As linhagens celulares UW402, UW473 e ONS-76 não apresentaram mutações no éxon 3 do gene CTNNB1 (?-catenina) e no éxon 15 do gene APC. Não foi observada uma expressão significativa de CTNNB1, confirmando que as linhagens não possuíam a via Wnt ativa. Com isso foi necessário a transfecção transiente com a ?- catenina. Após este ensaio, houve um aumento da expressão de CTNNB1, Ciclina D1 e CMyc nas três linhagens, o que não ocorreu com as Auroras A e B. No ensaio clonogênico foi observado uma redução do número de colônias nas linhagens UW473 e ONS-76. Observou-se um aumento da expressão proteica da ?-catenina, da Aurora A e B na UW473, o que ocorreu somente com a ?-catenina na linhagem ONS-76. Após o tratamento com o AMG900 ocorreu uma diminuição da expressão proteica de ?-catenina, da Aurora A e B em ambas as linhagens. A transfecção não alterou o percentil celular em G2/M na UW402 e UW473. Já na ONS-76 houve um aumento significativo em G2/M, e o AMG900 potencializou esse bloqueio apenas nessa linhagem. Os resultados sugerem que pode haver alguma relação entre a inibição das proteínas Aurora-quinases e a expressão de proteínas da via Wnt. / Medulloblastoma (MB) is the most common malignant brain tumor in childhood. Tumor formation/progression has been associated to molecular alterations that include dysregulation of signaling pathway Wingless (Wnt), responsible for embryonic development. In addition, cell cycle proteins Aurora-kinase (A, B and C) have been widely studied since Aurora A and B were found overexpressed in many cancers such as MB. Recent studies show that there is an association between Wnt pathway and Aurora kinase proteins. However, few studies have been conducted to confirm this association. Moreover, there are no studies reporting the effects of AMG900 in MB, by focusing on the regulation of the Wnt pathway. The aim of this study is to evaluate Wnt pathway modulation by Aurora kinases inhibitor AMG900 in pediatric medulloblastoma cell lines. Conventional PCR, sequencing, qRT-PCR, transient transfection, clonogenic assay, Western Blot and cell cycle assays were performed. UW402, UW473 and ONS-76 cell lines did not present mutations in exon 3 of CTNNB1 gene and exon 15 of APC gene. There was no significant expression of CTNNB1 and their target genes in these cell lines, confirming that they did not have Wnt pathway activated. Considering this, transient transfection was necessary. After this trial, there was an increase in expression of CTNNB1 gene and its target genes Cyclin D1 and C-Myc in the three cell lines, which was not observed in Aurora kinases. Furthermore, in the clonogenic assay, a reduction in the number of colonies in UW473 and ONS-76 cell lines was observed. It was also observed an increase in ?-catenin protein, Aurora A and B in UW473 cell line, but not in ONS-76 cell line. However, after treatment there was a decrease in protein expression of ?-catenin, Aurora A and B in both cells. Transfection did not change the cellular percentile in G2 / M in UW402 and UW473. In ONS-76 there was a significant increase in G2 / M, and the treatment with AMG900 potentiated this block only in this cell line. Results suggest that there may be some relation between the inhibition of Aurora kinase protein and protein expression in Wnt pathway.

O meduloblastoma é o tumor cerebral maligno mais comum em crianças de zero a quatro anos e uma das principais causas de morbidade e mortalidade infantil. Diversos estudos têm suportado a hipótese de que a ativação de genes tipicamente expressos em células-tronco confere características mais primitivas e agressivas a células tumorais, frequentemente associadas a prognóstico clínico desfavorável. Nesse contexto, tanto fatores proteicos quanto miRNAs poderiam estimular uma reprogramação em células cancerosas, induzindo um fenótipo semelhantes ao de células-tronco. Estudos recentes apontam o envolvimento do miR-367 na reprogramação de fibroblastos ao estado pluripotente e sua expressão aberrante foi correlacionada com prognóstico desfavorável em alguns tipos de câncer. Neste trabalho, verificou-se um possível papel funcional do miR-367 na agressividade de meduloblastoma. Células de meduloblastoma de quatro diferentes linhagens, Daoy, D283-Med, CHLA-01-Med e USP-13-Med apresentaram níveis baixos de expressão de pri-miR-367 e miR-367 maduro, em relação aos níveis encontrados em células-tronco embrionárias humanas. Uma superexpressão transiente do miR-367 em células das linhagens CHLA-01-Med e USP-13-Med resultaram em uma redução significativa dos níveis proteicos de RYR3, bem como dos transcritos preditos de ITGAV e RAB23, respectivos alvos do miR-367, envolvidos em câncer. Além disso, a superexpressão de miR-367 aumentou significativamente a proliferação celular, indicada pela cinética de crescimento in vitro e pela maior porcentagem de células presentes nas fases S+G2/M do ciclo celular. Embora a sensibilidade ao tratamento com cisplatina não tenha sido alterada após superexpressão de miR-367, a capacidade de geração de neuroesferas in vitro foi significativamente aumentada. Este último resultado é interessante do ponto de vista clínico, uma vez que a capacidade de geração de neuroesferas está significativamente correlacionada com menor sobrevida de pacientes com meduloblastoma. Portanto, esses achados sugerem uma função pró-oncogênica ao miR-367, a qual pode afetar a agressividade de meduloblastoma por meio de efeitos positivos sobre a proliferação celular e propriedades de células-tronco neurais / Medulloblastoma is the most common malignant brain tumor in children aged four and younger, and is the leading cause of infant morbidity and mortality. Several studies have reported the activation of stem cell genes leading to more primitive and aggressive characteristics in tumor cell often associated with unfavorable clinical prognosis. Cell reprogramming, stimulated by tumor microenvironment factors, might induce tumor stem cells phenotype. Recent researches suggest an involvement of miR-367 in fibroblasts reprogramming into pluripotent state, as well as a correlation with poor prognosis in some cancers. In this study, we observed a possible functional role of miR-367 in medulloblastoma aggressiveness. Four different medulloblastoma cell lines, Daoy, D283-Med, CHLA-01-Med and USP-13-Med showed low rates of pri-miR-367 and mature miR-367 expression. Overexpression of miR-367 down-regulated the protein levels of its target RYR3 and of two bioinformatically predicted transcript targets encoding ITGAV and RAB23, which are involved in cancer in CHLA-01-Med and USP-13 Med cell lines. Furthermore, transfection with the miRNA mimic significantly increased cell proliferation and the percentage of cells observed in S + G2 / M phase of the cell cycle. Although the sensitivity to cisplatin treatment was not changed after overexpression of miR-367, the ability to generate neurospheres in vitro was significantly increased. This last result can be related to clinical ones because cells from medulloblastoma patients with low survival show great ability to generate neurospheres. In sum, these findings suggest a pro-oncogenic role to miR-367, which can affect medulloblastoma aggressiveness by cell proliferation and neural stem cells positive modifications

Medulloblastoma is the most common malignant brain tumor in children. Genetic profiling has identified four principle tumor subgroups; each subgroup is characterized by different initiating mutations, genetic and clinical profiles, and prognoses. The two most well-defined subgroups are caused by overactive signaling in the WNT and SHH mitogenic pathways; less is known about Groups 3 and 4 medulloblastomas. Identification of tumor subgroup using molecular classification is poised to become an important component of the medulloblastoma diagnosis and staging and will likely guide therapeutic options. G-protein coupled receptors (GPCR) possess characteristics that make them ideal targets for molecular imaging and therapeutics. While expression patterns of many proteins in human medulloblastoma subgroups have been discerned, the expression pattern of GPCRs in medulloblastoma has not been investigated. We have found that clusters of medulloblastoma tumors arise based solely on differential GPCR expression patterns. Further, two of these clusters correspond with high fidelity to the WNT and SHH subgroups. Distinct over-expressed GPCRs emerge; for example, LGR5 and GPR64 are significantly and uniquely over-expressed in the WNT subgroup of tumors, while PTGER4 is over-expressed in the SHH subgroup. Uniquely under-expressed GPCRs were also observed. Our results identify GPCRs with potential to act as imaging and therapeutic targets; elucidating tumorigenic mechanisms is a secondary benefit to identifying differential GPCR expression patterns in medulloblastoma tumors. Current imaging for diagnosis, staging, and measuring response to therapy for medulloblastoma patients relies heavily on MRI; single photon emission tomography (SPECT) using 111In-DTPA-Octreotide targeting the somatostatin type 2 receptor (SSTR2) is also available. Positron emission tomography (PET) affords a more sensitive and specific imaging modality than SPECT; however, the most common tracer 18FDG, is of limited usefulness for the delineation of brain tumors. Smoothened (SMO) is a GPCR that is overexpressed in a subset of medulloblastoma; we hypothesized that SMO overexpression could be exploited as a specific PET target in these tumors. Genentech generously provided the synthetically-derived small-molecule SMO ligand, GDC-0449, for use as the lead compound for development of a PET tracer. GDC-0449 has already been demonstrated to localize in brain tumors and has Cl- atoms incorporated in positions that are predicted to readily exchange with fluorine-18 to generate a fluorinated analog of the compound. We have successfully fluorinated GDC-0449, with very high radiochemical purity. Binding assays reveal affinities of the fluorinated analog of GDC-0449 for SMO to be comparable to precursor GDC-0449, and biodistribution experiments demonstrate accumulation of the fluorinated compound in tumors. The fluorinated analog of GDC-0449 holds promise as a novel PET imaging agent in medulloblastoma, providing highly specific and sensitive imaging for use in diagnosis, staging and measurement of response-to-treatment.

<p>Medulloblastoma is a highly malignant cerebellar childhood tumor. As in many other brain tumors, expression of platelet-derived growth factor (PDGF) and its receptors has been shown in medulloblastoma. To reveal the importance of this growth factor in cerebellar development and tumorigenesis, analyses were performed on human medulloblastoma cell lines and on tissue from normal mouse brain at different stages of development. The <i>in vivo</i> effect of a forced expression of PDGF-B in the cerebellar primordium was examined in transgenic mice. </p><p>In the normal mouse embryo, we found PDGF receptor-α-positive cells in the early neuroepithelium and on neuronal precursors. In the postnatal cerebellum, cells in the external germinal layer and Purkinje cells expressed the receptor. In the medulloblastoma cells, expression of all the three PDGF isoforms and PDGF receptors was seen and correlated to neuronal differentiation. Endogenously activated, <i>i.e.</i> tyrosine phosphorylated, PDGF receptors were identified. To reveal the role of PDGF in normal cerebellar development, we established transgenic mice where a PDGF-B cDNA was introduced via homologous recombination into the engrailed-1 gene. Engrailed-1 is specifically expressed at the mid-/hindbrain boundary of the early neural tube, <i>i.e.</i> in an area from which the cerebellar primordium develops. The ectopic expression of PDGF-B caused a disturbance of cerebellar development. Midline fusion of the cerebellar primordium did not occur properly, which resulted in cerebellar dysplasia in the adult mouse.</p><p>In a parallel study, the expression pattern of a glial fibrillary acidic protein (GFAP)-<i>lacZ</i> transgene was followed in the embryonic mouse central nervous system. It was shown that the human GFAP promoter was already active by embryonic day 9.5 and as development proceeded, expression occured in different, independent cell populations. Among these cell populations were the radial glial cells in the neocortex.</p>

Medulloblastoma is a highly malignant cerebellar childhood tumor. As in many other brain tumors, expression of platelet-derived growth factor (PDGF) and its receptors has been shown in medulloblastoma. To reveal the importance of this growth factor in cerebellar development and tumorigenesis, analyses were performed on human medulloblastoma cell lines and on tissue from normal mouse brain at different stages of development. The in vivo effect of a forced expression of PDGF-B in the cerebellar primordium was examined in transgenic mice. In the normal mouse embryo, we found PDGF receptor-α-positive cells in the early neuroepithelium and on neuronal precursors. In the postnatal cerebellum, cells in the external germinal layer and Purkinje cells expressed the receptor. In the medulloblastoma cells, expression of all the three PDGF isoforms and PDGF receptors was seen and correlated to neuronal differentiation. Endogenously activated, i.e. tyrosine phosphorylated, PDGF receptors were identified. To reveal the role of PDGF in normal cerebellar development, we established transgenic mice where a PDGF-B cDNA was introduced via homologous recombination into the engrailed-1 gene. Engrailed-1 is specifically expressed at the mid-/hindbrain boundary of the early neural tube, i.e. in an area from which the cerebellar primordium develops. The ectopic expression of PDGF-B caused a disturbance of cerebellar development. Midline fusion of the cerebellar primordium did not occur properly, which resulted in cerebellar dysplasia in the adult mouse. In a parallel study, the expression pattern of a glial fibrillary acidic protein (GFAP)-lacZ transgene was followed in the embryonic mouse central nervous system. It was shown that the human GFAP promoter was already active by embryonic day 9.5 and as development proceeded, expression occured in different, independent cell populations. Among these cell populations were the radial glial cells in the neocortex.

<p>Development requires a delicate balance of proliferation and differentiation. Too little proliferation can result in dysfunctional tissues, while prolonged or heightened proliferation can result in tumor formation. This is clearly seen with the granule neuron precursors (GNPs) of the cerebellum. Too little proliferation of these cells during development results in ataxia, whereas too much proliferation results in the cerebellar tumor medulloblastoma. While these cells are known to proliferate in response to Shh, it is not clear what controls the differentiation of these cells in vivo.</p><p> Previous work from our lab has identified basic fibroblast growth factor (bFGF) as a candidate differentiation factor for these cells. In this thesis, I characterize some of the cellular and molecular mechanisms involved in FGF-mediated inhibition (FMI) of Shh-induced GNP proliferation. In addition, I employ FGFR knockouts and a bFGF gain-of-function mouse to determine whether FGF signaling is necessary and/or sufficient for differentiation of GNPs during cerebellar development. Finally, the question of whether bFGF can be effective as a therapeutic agent for in vivo tumor treatment is tested in a transplant model.</p><p> These experiments indicate that FGF signaling is neither necessary nor sufficient for GNP differentiation during cerebellar development. However, transplanted tumors are potently inhibited by bFGF treatment. Furthermore, FMI is shown to occur around the level of Gli2 processing in the Shh pathway, implying that such a treatment has promise to be widely effective in treatment of Shh-dependent medulloblastomas.</p> / Dissertation

Medulloblastomas represent a heterogeneous group of cerebellar tumors that constitute the most frequent primary pediatric solid malignancy. Molecular characterization of these tumors have led to the understanding that distinctsubtypes possess characteristic properties such as gene expression profile, histological classification, and degree of dissemination that are predictive of disease progression and prognosis. Fractionation of primary medulloblastomas has led to the appreciation of brain tumor stem cells (BTSC) that may be driving the more aggressive and malignant disease. However, the developmental origins of these cells as well as the influences of early mutations in tumor suppressors on development and tumorigenesisremain unclear. My work is geared towards understanding the impact of mutations in the key tumor suppressor genes Ptc1 and p53 on medulloblastoma formation. I first identified key differences in neural stem cell marker expression that distinguish between Ptc1 and Ptc1;p53 medulloblastomas, demonstrating that the Ptc1;p53 genotype may pre-dispose to a more malignant, stem-like tumor. Through the use of a somatic mosaic model, we describe a synergistic interaction between Ptc1 haploinsufficiency and p53 deficiency leading to developmental seeding of the cerebellar field by pre-malignant cells and term this phenomenon “developmental field cancerization.” Interestingly, we observed this premalignant colonization in the cerebellarstem cell compartment as well, resulting in an aberrant population of self-renewing cells. Upon loss-of-heterozygosity at the Ptc1 locus, the Ptc;p53 animals alone develop robust cerebellar tumorsthat possess a definable stem-like population of cells that can re-initiate metastatic secondary tumors. These findings demonstrate how early mutationsin the tumor suppressor genes, such as Ptc1 and p53, may lead to stem cell field cancerization and play an important role in determining future tumor character and prognosis.

Medulloblastoma, the most common pediatric malignant brain tumor, is comprised of a heterogeneous group of tumors with distinct molecular subtypes and clinical outcomes. In particular, tumors with a cancer stem cell (CSC) population have been observed to be more resistant to conventional therapies, necessitating the elucidation of pathways important in this population. Work in our lab has shown that neurosphere culture-enriched cells from Ptch1LacZ/+;Trp53-/- mouse medulloblastomas exhibit properties of self-renewal, expression of neural stem cell (NSC) markers and potent tumor-initiation. The pathway dependencies and mechanisms of self-renewal in these medulloblastoma neurospheres (MBNS) have not yet been characterized.

Neural stem cell self-renewal and differentiation are tightly regulated events during CNS development, leading to cell division into new neural stem cells or the formation of neurons and glial cells. This thesis focuses on the cellular responses induced by known and novel factors in neural stem and progenitor cells (NSPCs). Platelet-derived growth factor (PDGF) signaling has previously been implicated in NSPC regulation as well as in tumor formation. In order to evaluate the differentiation process and find new regulators of NSPCs a micro-array screen was performed, evaluating transcription during normal differentiation and the effect of PDGF-AA in this process. The transcriptional profile of PDGF-AA treated NSPCs was shown to be an intermediate between the profiles of neural stem cells and their progeny. The NSPC transcriptome was also found to have similarities with that of experimental glioma. A previously non-characterized transcript, the nuclear receptor binding protein 2 (NRBP2), was identified and found to be expressed in the developing and adult mouse brain and in medulloblastoma. NRBP2 down-regulation rendered neural progenitors sensitive to induced cell death. Different PDGF ligands interact with different combinations of PDGF receptors. Therefore NSPCs were stimulated with either PDGF-AA or -BB to further evaluate cellular responses with regard to the two specific isoforms. A divergent effect between the two isoforms in long-term proliferation and cell survival was found, with PDGF-BB being the most efficient stimulator. Stem cell factor (SCF) has previously been identified as a regulator in the hematopoietic system and we showed that SCF induces a migratory response in NSPCs. In addition, SCF positively affected cell survival but had no effect on NSPC differentiation. Insights into the regulatory mechanisms involved in neural stem cell signaling are needed to develop diagnostic tools and novel treatments.