Key role for p27Kip1, retinoblastoma protein Rb, and MYCN in polyamine inhibitor-induced G1 cell cycle arrest in MYCN-amplified human neuroblastoma cells.
Alpha-difluoromethylornithine (DFMO) inhibits the proto-oncogene ornithine decarboxylase (ODC) and is known to induce cell cycle arrest. However, the effect of DFMO on human neuroblastoma (NB) cells and the exact mechanism of DFMO-induced cell death are largely unknown. Treatment with DFMO in combination with SAM486A, an S-adenosylmethionine decarboxylase (AdoMetDC) inhibitor, has been shown to enhance polyamine pool depletion. Therefore, we analysed the mechanism of action of DFMO and/or SAM486A in two established MYCN-amplified human NB cell lines. DFMO and SAM486A caused rapid cell growth inhibition, polyamine depletion, and G1 cell cycle arrest without apoptosis in cell lines LAN-1 and NMB-7. These effects were enhanced with combined inhibitors and largely prevented by cotreatment with exogenous polyamines. The G1 cell cycle arrest was concomitant with an increase in cyclin-dependent kinase inhibitor p27Kip1. In a similar fashion, DFMO and DFMO/SAM486A inhibited the phosphorylation of the G1/S transition-regulating retinoblastoma protein Rb at residues Ser795 and Ser807/811. Moreover, we observed a dramatic decrease in MYCN protein levels. Overexpression of MYCN induces an aggressive NB phenotype with malignant behavior. We show for the first time that DFMO and SAM486A induce G1 cell cycle arrest in NB cells through p27Kip1 and Rb hypophosphorylation.
Wallick
Christopher J
CJ
Cancer Research Center of Hawaii, University of Hawaii at Manoa, 1236 Lauhala Street, Honolulu, HI 96813, USA.
Gamper
Ivonne
I
Thorne
Mike
M
Feith
David J
DJ
Takasaki
Kelsie Y
KY
Wilson
Shannon M
SM
Seki
Jennifer A
JA
Pegg
Anthony E
AE
Byus
Craig V
CV
Bachmann
André S
AS
D012437:Adenosylmethionine Decarboxylase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000578:Amidines / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007189:Indans / Q000494:pharmacology; D000071447:N-Myc Proto-Oncogene Protein; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D015513:Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*; D009955:Ornithine Decarboxylase / Q000378:metabolism; D011073:Polyamines / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D016160:Retinoblastoma Protein / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D000578:Amidines; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D007189:Indans; C000715470:MAS1 protein, human; C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011073:Polyamines; D000090063:Proto-Oncogene Mas; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C082408:4-amidinoindan-1-one 2'-amidinohydrazone; D009955:Ornithine Decarboxylase; D012437:Adenosylmethionine Decarboxylase