c- and N-myc Regulate Neural Precursor Cell Fate, Cell Cycle, and Metabolism to Direct Cerebellar Development

Separate murine knockout (KO) of either c- or N-myc genes in neural stem and precursor cells (NSC) driven by nestin-cre causes microcephaly. The cerebellum is particularly affected in the N-myc KO, leading to a strong reduction in cerebellar granule neural progenitors (CGNP) and mature granule neurons. In humans, mutation of N-myc also causes microcephaly in Feingold Syndrome. We created a double KO (DKO) of c- and N-myc using nestin-cre, which strongly impairs brain growth, particularly that of the cerebellum. Granule neurons were almost absent from the Myc DKO cerebellum, and other cell types were relatively overrepresented, including astroglia, oligodendrocytes, and Purkinje neurons. These findings are indicative of a profound disruption of cell fate of cerebellar stem and precursors. DKO Purkinje neurons were strikingly lacking in normal arborization. Inhibitory neurons were ectopic and exhibited very abnormal GAD67 staining patterns. Also consistent with altered cell fate, the adult DKO cerebellum still retained a residual external germinal layer (EGL). CGNP in the DKO EGL were almost uniformly NeuN and p27KIP1 positive as well as negative for Math1 and BrdU at the peak of normal cerebellar proliferation at P6. The presence of some mitotic CGNP in the absence of S phase cells suggests a possible arrest in M phase. CGNP and NSC metabolism also was affected by loss of Myc as DKO cells exhibited weak nucleolin staining. Together these findings indicate that c- and N-Myc direct cerebellar development by maintaining CGNP and NSC populations through inhibiting differentiation as well as directing rapid cell cycling and active cellular metabolism

Anti-proliferative activity of the quassinoid NBT-272 in childhood medulloblastoma cells

BACKGROUND: With current treatment strategies, nearly half of all medulloblastoma (MB) patients die from progressive tumors. Accordingly, the identification of novel therapeutic strategies remains a major goal. Deregulation of c-MYC is evident in numerous human cancers. In MB, over-expression of c-MYC has been shown to correlate with anaplasia and unfavorable prognosis. In neuroblastoma – an embryonal tumor with biological similarities to MB – the quassinoid NBT-272 has been demonstrated to inhibit cellular proliferation and to down-regulate c-MYC protein expression. METHODS: To study MB cell responses to NBT-272 and their dependence on the level of c-MYC expression, DAOY (wild-type, empty vector transfected or c-MYC transfected), D341 (c-MYC amplification) and D425 (c-MYC amplification) human MB cells were used. The cells were treated with different concentrations of NBT-272 and the impact on cell proliferation, apoptosis and c-MYC expression was analyzed. RESULTS: NBT-272 treatment resulted in a dose-dependent inhibition of cellular proliferation (IC50 in the range of 1.7 – 9.6 ng/ml) and in a dose-dependent increase in apoptotic cell death in all human MB cell lines tested. Treatment with NBT-272 resulted in up to 90% down-regulation of c-MYC protein, as demonstrated by Western blot analysis, and in a significant inhibition of c-MYC binding activity. Anti-proliferative effects were slightly more prominent in D341 and D425 human MB cells with c-MYC amplification and slightly more pronounced in c-MYC over-expressing DAOY cells compared to DAOY wild-type cells. Moreover, treatment of synchronized cells by NBT-272 induced a marked cell arrest at the G1/S boundary. CONCLUSION: In human MB cells, NBT-272 treatment inhibits cellular proliferation at nanomolar concentrations, blocks cell cycle progression, induces apoptosis, and down-regulates the expression of the oncogene c-MYC. Thus, NBT-272 may represent a novel drug candidate to inhibit proliferation of human MB cells in vivo

Gliomas do nervo óptico: estudo de 11 casos Optic nerve gliomas: a study of 11 cases

Os gliomas do nervo óptico podem apresentar-se esporadicamente ou como componentes da neurofibromatose. São neoplasias raras, correspondendo a 2 a 5% dos tumores intracranianos e cerca de 6% dos tumores intra-orbitários. No presente estudo, analisamos 11 casos de glioma de nervo óptico diagnosticados em Curitiba num período de 25 anos, sendo 10 pacientes do sexo feminino e 1 do sexo masculino. As idades variaram de 3 a 25 anos; 6 pacientes apresentavam idades inferiores a 15 anos. Dos casos desta série, 27,3% (n=3) apresentavam associação com neurofibromatose. Quanto à localização dos tumores, em 5 pacientes a lesão estava restrita ao nervo óptico e no restante havia extensão para o quiasma óptico, região supra-selar, lobo frontal ou temporal. Todos os pacientes tinham astrocitoma pilocítico.<br>Optic nerve gliomas may occur alone or as components of neurofibromatosis. They are rare tumors accounting for 2 to 5% of all intracranial tumors and 6% of the intra-orbitary neoplasms. The authors present 11 cases of optic nerve glioma diagnosed in Curitiba in the last 25 years. Out of these 11 patients there were 10 women and only 1 man. The ages ranged from 3 to 25 years old, and 6 patients were under 15 years. In this series, 27,3% (n=3) of the cases were associated with neurofibromatosis. Five patients had their tumors restricted to the optic nerve while the others had either extension to the optic chiasm, supra-selar region, frontal or temporal lobe. All the patients had pilocytic astrocytomas