title: p53-independent increase in E2F-1 expression enhances the cytotoxic effects of etoposide and of adriamycin.
abstract: The transcription factor E2F-1 drives cell cycle progression at the G1- to S-phase boundary; however, overexpression of E2F-1 can induce apoptosis. We show here that E2F-1 protein levels increase in human medulloblastoma, glioma, lung, colon, and bladder cancer cell lines (n=7) following treatment with the DNA damaging agents adriamycin or etoposide. This induction of E2F-1 occurs independently of Rb or p53 status and involves new protein synthesis. Although E2F-1 protein levels increase following DNA damage, several genes transcriptionally targeted by E2F-1 are not similarly induced. Rather, induction of E2F-1 in the tumor cells correlates with their sensitivity to adriamycin or to etoposide. Correspondingly, fibroblasts from E2F-1 knockout mice are more resistant to DNA damage than cells from normal mice. Overexpression of E2F-1 protein in tumor cell lines infected with an adenovirus encoding wild-type E2F-1 leads to enhanced cytotoxicity following exposure to DNA damaging agents, which results from enhanced apoptosis. The results of this study implicate a role for E2F-1 in p53-independent cytotoxicity of chemotherapy and provide a pharmacological tool for increasing levels of the apoptosis-inducing E2F-1 protein.
authors.affiliation: Laboratory of Molecular Oncology and Cell Cycle Regulation, Howard Hughes Medical Institute, Departments of Medicine, Genetics, Cancer Center, and Institute for Human Gene Therapy, University of Pennsylvania School of Medicine, Philadelphia,
authors.forename: R D
authors.initials: RD
authors.lastname: Meng
authors.forename: P
authors.initials: P
authors.lastname: Phillips
authors.forename: W S
authors.initials: WS
authors.lastname: El-Deiry
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000187:drug effects*; D004249:DNA Damage; D004268:DNA-Binding Proteins; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005047:Etoposide / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D016160:Retinoblastoma Protein / Q000502:physiology; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: C533431:Arid4a 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; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D005047:Etoposide; D004317:Doxorubicin; D004247:DNA; D003513:Cycloheximide