title: Phorbol ester effects on topoisomerase II activity and gene expression in HL-60 human leukemia cells with different proclivities toward monocytoid differentiation.
abstract: We examined the effects of phorbol ester treatment on topoisomerase II-mediated events in two human leukemia cell lines with different proclivities toward phorbol ester-induced monocytoid differentiation. HL-60 is the parent line that will terminally differentiate; 1E3 is a derived line that will not terminally differentiate. Within 24 h of phorbol ester treatment, etoposide-induced, topoisomerase II-mediated DNA cleavage declined 10-fold, whereas 4'-(9-acridinylamino)-methanesulfon-m-anisidide- induced DNA cleavage declined 3-fold in HL-60. In phorbol-treated 1E3, etoposide-induced DNA cleavage declined only 2-fold, whereas 4'-(9-acridinylamino)methanesulfon-m-anisidide-induced cleavage was barely affected. There was a 2- to 3-fold decline in topoisomerase II activity within the nuclear extracts from phorbol-treated HL-60 cells but not from phorbol-treated 1E3 cells. Immunoblotting experiments with anti-topoisomerase II antibodies indicated that phorbol treatment produced a structural change in the immunoreactive topiosomerase II in HL-60 nuclear extracts but produced no change in 1E3 topoisomerase II. Phorbol ester treatment also produced a decline in the level of topoisomerase II gene expression in HL-60 but not in 1E3 cells. By contrast, the cytotoxicity of etoposide in both lines was decreased following phorbol treatment. Thus, phorbols may uncouple the mechanisms linking drug-induced, topoisomerase II-DNA cleavable complex stabilization with drug-induced cytotoxicity, particularly in 1E3.
authors.affiliation: Department of Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
authors.forename: L A
authors.initials: LA
authors.lastname: Zwelling
authors.forename: M
authors.initials: M
authors.lastname: Hinds
authors.forename: D
authors.initials: D
authors.lastname: Chan
authors.forename: E
authors.initials: E
authors.lastname: Altschuler
authors.forename: J
authors.initials: J
authors.lastname: Mayes
authors.forename: T F
authors.initials: TF
authors.lastname: Zipf
mesh_terms: D000677:Amsacrine / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D005047:Etoposide / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007951:Leukemia, Myeloid; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D009687:Nuclear Proteins; D010703:Phorbol Esters; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D000677:Amsacrine; D005047:Etoposide; D004250:DNA Topoisomerases, Type II