title: Differential cytotoxic pathways of topoisomerase I and II anticancer agents after overexpression of the E2F-1/DP-1 transcription factor complex.
abstract: The transcription factor complex E2F-1/DP-1 regulates the G1-to-S-phase transition and has been associated with sensitivity to the S-phase-specific anticancer agents camptothecin and etoposide, which poison DNA topoisomerase I and II, respectively. To investigate the relationship between E2F-1 and drug sensitivity in detail, we established human osteosarcoma U-20S-TA cells expressing full-length E2F-1/ DP-1 under the control of a tetracycline-responsive promoter, designated UE1DP-1 cells. Topoisomerase I levels and activity as well as the number of camptothecin-induced DNA single- and double-strand breaks were unchanged in UEIDP-1/tc- cells with >10-fold E2F-1/DP-1 overexpression. However, UE1DP-1/tc- cells were hypersensitive to camptothecin in both a clonogenic assay and four different apoptotic assays. This indicates that camptothecin-induced toxicity in this model is due to the activation of an E2F-1/ DP-1-induced post-DNA damage pathway rather than an increase in the number of replication forks caused by the S-phase initiation. In contrast, topoisomerase IIalpha levels (but not topoisomerase IIbeta levels), together with topoisomerase IIalpha promoter activity, increased 2--3-fold in UE1DP-1/tc-cells. Furthermore, the number of etoposide-induced DNA single- and double-strand breaks increased in UE1DP-1/tc-cells together with a rise in clonogenic sensitivity to etoposide, but an equal apoptotic sensitivity to etoposide. The increase in topoisomerase IIalpha promoter activity in UE1DP-1/tc--cells was shown to be due to S-phase initiation per se because it was blocked by ectopic expression of dominant negative cyclin-dependent kinase 2. In conclusion, overexpression of E2F-1/DP-1 in U-20S-TA cells is sufficient to increase clonogenic sensitivity to both topoisomerase I- and II-targeted anticancer drugs. However, the mechanism by which this occurs appears to be qualitatively different. The UE1DP-1 cell model may be used to elucidate post-DNA damage mechanisms of cell death induced by topoisomerase I-directed anticancer agents.
authors.affiliation: Laboratory and Finsen Centres, Rigshospitalet, Copenhagen, Denmark.
authors.forename: K
authors.initials: K
authors.lastname: Hofland
authors.forename: B O
authors.initials: BO
authors.lastname: Petersen
authors.forename: J
authors.initials: J
authors.lastname: Falck
authors.forename: K
authors.initials: K
authors.lastname: Helin
authors.forename: P B
authors.initials: PB
authors.lastname: Jensen
authors.forename: M
authors.initials: M
authors.lastname: Sehested
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000494:pharmacology; D002352:Carrier Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D004247:DNA / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism; D004274:DNA, Recombinant / Q000235:genetics; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase; D013936:Thymidine / Q000378:metabolism; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004274:DNA, Recombinant; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D004791:Enzyme Inhibitors; D011993:Recombinant Fusion Proteins; D056465:Retinoblastoma-Binding Protein 1; C493735:TFDP1 protein, human; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D050680:Transcription Factor DP1; D014157:Transcription Factors; D005047:Etoposide; D004247:DNA; D008156:Luciferases; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D002945:Cisplatin; D013936:Thymidine; D002166:Camptothecin