title: E2F activity is essential for survival of Myc-overexpressing human cancer cells.
abstract: Effective cell cycle completion requires both Myc and E2F activities. However, whether these two activities interact to regulate cell survival remains to be tested. Here we have analysed survival of inducible c-Myc-overexpressing cell lines derived from U2OS human osteosarcoma cells, which carry wild-type pRb and p53 and are deficient for p16 and ARF expression. Induced U2OS-Myc cells neither underwent apoptosis spontaneously nor upon reconstitution of the ARF-p53 axis and/or serum-starvation. However, they died massively when concomitantly exposed to inhibitors of E2F activity, including a constitutively active pRb (RbDeltacdk) mutant, p16, a stable p27 (p27T187A) mutant, a dominant-negative (dn) CDK2, or dnDP-1. Similar apoptotic effect was observed upon down-modulation of endogenous E2Fs through overexpression of E2F binding site oligonucleotides in U2OS-Myc cells, upon expression of RbDeltacdk or dnDP-1 in the Myc-amplified HL-60 (ARF-; p53-) human leukemia cells, and upon co-transfection of Myc and RbDeltacdk in SAOS-2 (ARF+; p53-) human osteosarcoma cells but not in human primary fibroblasts. Consistent with these results, a dnp53 mutant did not abrogate the Myc-induced apoptotic phenotype, which instead strictly depended on caspase-3-like proteases and on Myc transcriptional activity. Our data indicate that in contrast to normal cells, Myc-overexpressing human cancer cells need E2F activity for their survival, regardless of their ARF and p53 status, a notion that may have important implications for antineoplastic treatment strategies.
authors.affiliation: Department of Cell Cycle and Cancer, Institute of Cancer Biology, Danish Cancer Society, 2100 Copenhagen E., Denmark. bartek@biobase.dk
authors.forename: Eric
authors.initials: E
authors.lastname: Santoni-Rugiu
authors.forename: Dominique
authors.initials: D
authors.lastname: Duro
authors.forename: Thomas
authors.initials: T
authors.lastname: Farkas
authors.forename: Ida S
authors.initials: IS
authors.lastname: Mathiasen
authors.forename: Marja
authors.initials: M
authors.lastname: Jäättelä
authors.forename: Jiri
authors.initials: J
authors.lastname: Bartek
authors.forename: Jiri
authors.initials: J
authors.lastname: Lukas
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D001859:Bone Neoplasms / Q000378:metabolism* / Q000473:pathology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004268:DNA-Binding Proteins; D015536:Down-Regulation; D050684:E2F Transcription Factors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant / Q000502:physiology; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D009841:Oligonucleotides / Q000494:pharmacology*; D012516:Osteosarcoma / Q000378:metabolism* / Q000473:pathology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D025803:Tumor Suppressor Protein p14ARF / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D061945:Caspase Inhibitors; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D004791:Enzyme Inhibitors; D009841:Oligonucleotides; D016271:Proto-Oncogene Proteins c-myc; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases