Adenovirus-mediated E2F-1 gene transfer inhibits MDM2 expression and efficiently induces apoptosis in MDM2-overexpressing tumor cells.
The oncoprotein MDM2 binds and inactivates p53. MDM2 also binds to the tumor suppressor pRB, as well as E2F-1. E2F-1 is a transcription factor that regulates S phase entry and has been shown to cause apoptosis in some cell types when overexpressed. To investigate the effect of adenovirus-mediated E2F-1 overexpression, MDM2-overexpressing tumor cell lines were treated by mock infection, infection with an adenoviral vector expressing beta galactosidase, or E2F-1 (Ad5CMV-E2F-1). Western blot analysis confirmed significant overexpression of E2F-1 in Ad5CMV-E2F-1-infected cells. E2F-1 overexpression resulted in marked growth inhibition and rapid loss of cell viability. Ad5CMV-E2F-1 infection resulted in early S phase entry, followed by apoptotic cell death. E2F-1 overexpression was associated with a marked decrease in MDM2 levels and no evidence of increased Bax levels, whereas p53 and Bcl-2 levels remained undetectable. Cleavage of poly-ADP-ribose polymerase and caspase 3/CPP32 implicated activation of the caspase cascade in E2F-1-mediated apoptosis. These results indicate that adenovirus-mediated E2F-1 overexpression in MDM2-overexpressing tumor cells results in decreased MDM2 expression and widespread apoptosis. Because MDM2-overexpressing tumors are often resistant to p53 gene therapy, adenovirus-mediated E2F-1 gene therapy may be a promising alternative strategy.
Yang
H L
HL
Department of Surgery, James Graham Brown Cancer Center, University of Louisville, Kentucky 40202, USA.
Dong
Y B
YB
Elliott
M J
MJ
Liu
T J
TJ
Atienza
C
C
Stilwell
A
A
McMasters
K M
KM
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002352:Carrier Proteins; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D002470:Cell Survival / Q000235:genetics; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D015870:Gene Expression; D018014:Gene Transfer Techniques; D006801:Humans; D051379:Mice; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D051028:bcl-2-Associated X Protein
C533431:Arid4a protein, mouse; C494826:BAX protein, human; C494827:Bax protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases