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.


CONCLUSIONS
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.
von Bueren
André O
AO
Neuro-Oncology Program, University Children's Hospital, Zurich, Switzerland. Andre.vonBueren@kispi.unizh.ch <Andre.vonBueren@kispi.unizh.ch>
Shalaby
Tarek
T
Rajtarova
Julia
J
Stearns
Duncan
D
Eberhart
Charles G
CG
Helson
Lawrence
L
Arcaro
Alexandre
A
Grotzer
Michael A
MA
D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002528:Cerebellar Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D002648:Child; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D006131:Growth Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D008527:Medulloblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D036702:Quassins / Q000494:pharmacology* / Q000627:therapeutic use; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000096:biosynthesis
D004268:DNA-Binding Proteins; D006131:Growth Inhibitors; C116115:MYCBP protein, human; D036702:Quassins; D014157:Transcription Factors