title: Flavopiridol-induced apoptosis is mediated through up-regulation of E2F1 and repression of Mcl-1.
abstract: Flavopiridol treatment can lead to apoptosis via a mechanism that has been associated with down-regulation of Mcl-1. Likewise, recent studies from our laboratory demonstrated that E2F1 leads to transcriptional repression of Mcl-1 and subsequently apoptosis. Given the ability of cyclin/cyclin-dependent kinase 2 antagonists to kill transformed cells, we surmised that flavopiridol may stabilize E2F1 and enhance apoptosis via repression of Mcl-1. Here we demonstrate that flavopiridol is associated with a dose-dependent increase in E2F1 protein levels, a corresponding reduction in Mcl-1, and apoptosis in H1299 lung carcinoma cells. Treatment of H1299 cells with 200 nM flavopiridol resulted in the rapid elevation of E2F1 and reduction in Mcl-1 levels within 12 h of treatment. The elevation of E2F1 and reduction in Mcl-1 clearly preceded the induction of apoptosis. Both H1299 and NIH3T3 fibroblast cell lines that constitutively express Mcl-1 under the control of the cytomegalovirus promoter have no reductions in Mcl-1 levels with flavopiridol treatment and are resistant to apoptosis induced by flavopiridol. H1299 cells that have E2F1 deleted through RNAi vector targeting are less sensitive to flavopiridol-induced cell death, and likewise, mouse embryo fibroblast cell lines deficient in E2F1 are less susceptible to apoptosis induced by flavopiridol compared with wild-type control fibroblasts. These data suggest that apoptosis induced by flavopiridol is dependent on the enhancement of E2F1 levels and the repression of Mcl-1.
authors.affiliation: Experimental Therapeutics Programs, H. Lee Moffitt Cancer Center and Research Institute, and Department of Interdisciplinary Oncology, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
authors.forename: Yihong
authors.initials: Y
authors.lastname: Ma
authors.forename: W Douglas
authors.initials: WD
authors.lastname: Cress
authors.forename: Eric B
authors.initials: EB
authors.lastname: Haura
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D002289:Carcinoma, Non-Small-Cell Lung; D018797:Cell Cycle Proteins / Q000235:genetics; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005419:Flavonoids / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D008175:Lung Neoplasms; D051379:Mice; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D010880:Piperidines / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; D005419:Flavonoids; C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D010880:Piperidines; D019253:Proto-Oncogene Proteins c-bcl-2; D014157:Transcription Factors; C077990:alvocidib