Abstract
BackgroundWith 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.MethodsTo 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.ResultsNBT-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.ConclusionIn 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.
Highlights
With current treatment strategies, nearly half of all medulloblastoma (MB) patients die from progressive tumors
We examined the effects of NBT272 in human MB cell lines expressing different levels of c-MYC
Results c-MYC expression in human MB cell lines To test the effects of NBT-272 on human MB cells, we selected three human MB cell lines with different levels of c-MYC expression [12,13]
Summary
Nearly half of all medulloblastoma (MB) patients die from progressive tumors. Nearly half of all patients die from progressive tumors. In childhood MB, c-MYC gene amplification has been demonstrated in ~8% of primary tumors [6,7,8,9,10,11]. High c-MYC mRNA expression and c-MYC gene amplification have been suggested to be indicators of poor prognosis in MB [6,9,11,12,13,14,15,16,17,18]. High cMYC mRNA expression was demonstrated to be significantly associated with tumor anaplasia [19,20]
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