Adenovirus-mediated E2F-1 gene transfer inhibits MDM2 expression and efficiently induces apoptosis in MDM2-overexpressing tumor cells

Clin Cancer Res. 1999 Aug;5(8):2242-50.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / genetics*
  • Animals
  • Apoptosis*
  • Blotting, Western
  • Carrier Proteins*
  • Caspase 3
  • Caspases / metabolism
  • Cell Cycle / genetics
  • Cell Cycle Proteins*
  • Cell Division / genetics
  • Cell Line
  • Cell Survival / genetics
  • DNA-Binding Proteins*
  • E2F Transcription Factors
  • E2F1 Transcription Factor
  • Gene Expression
  • Gene Transfer Techniques
  • Humans
  • Mice
  • Neoplasms, Experimental / genetics
  • Neoplasms, Experimental / metabolism*
  • Neoplasms, Experimental / pathology
  • Nuclear Proteins*
  • Proto-Oncogene Proteins / biosynthesis*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Proto-Oncogene Proteins c-mdm2
  • Retinoblastoma-Binding Protein 1
  • Transcription Factor DP1
  • Transcription Factors / biosynthesis
  • Transcription Factors / genetics*
  • Tumor Suppressor Protein p53 / biosynthesis
  • bcl-2-Associated X Protein

Substances

  • Arid4a protein, mouse
  • BAX protein, human
  • Bax protein, mouse
  • Carrier Proteins
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • E2F Transcription Factors
  • E2F1 Transcription Factor
  • E2F1 protein, human
  • E2f1 protein, mouse
  • Nuclear Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Retinoblastoma-Binding Protein 1
  • Transcription Factor DP1
  • Transcription Factors
  • Tumor Suppressor Protein p53
  • bcl-2-Associated X Protein
  • MDM2 protein, human
  • Mdm2 protein, mouse
  • Proto-Oncogene Proteins c-mdm2
  • CASP3 protein, human
  • Casp3 protein, mouse
  • Caspase 3
  • Caspases