title: Selective sensitization of adriamycin-resistant P388 murine leukemia cells to antineoplastic agents following transfection with human DNA topoisomerase II alpha.
abstract: Previous studies have demonstrated decreased levels of DNA topoisomerase II alpha protein and messenger RNA in the Adriamycin-resistant P388 murine leukemia cell line P388/ADR/7 compared to the sensitive P388/4 cell line. An allelic fusion event involving the topoisomerase II alpha and the retinoic acid receptor a genes has been identified in these cells that probably contributes to the decreased topoisomerase II activity in P388/ADR/7 cells. However, this allelic mutation may be a minor contributor or even incidental to the resistance phenotype, since these cells display other candidate mechanisms of resistance, including increased P-glycoprotein, increased glutathione-S-transferase activity and an increased onset of DNA repair. To establish a role for topoisomerase II alpha in mediating the Adriamycin resistance phenotype, complementation of the mutant allele was attempted by transfecting the murine P388/ADR/7 cells with a human topoisomerase II alpha expression construct under the control of the human metallothionein IIA promoter. The majority of transfected cell lines that were obtained by selection in hygromycin B contained copies of the integrated expression construct that were rearranged. Only two of thirty-two transfected cell lines were found to contain a single, unrearranged copy of the human topoisomerase II alpha cDNA. P388/ADR/7 cell lines carrying an integrated, intact human topoisomerase II alpha expression vector were more sensitive to Adriamycin, daunorubicin, mitoxantrone, and etoposide, but not to actinomycin D and vincristine compared to control cells transfected with vector alone or cell lines with rearranged topoisomerase II alpha expression constructs. These findings suggest that topoisomerase II alpha is a selective and significant contributor to multifactorial resistance.
authors.affiliation: Department of Pharmacology, University of Toronto, Ontario, Canada.
authors.forename: J P
authors.initials: JP
authors.lastname: McPherson
authors.forename: A M
authors.initials: AM
authors.lastname: Deffie
authors.forename: N R
authors.initials: NR
authors.lastname: Jones
authors.forename: G A
authors.initials: GA
authors.lastname: Brown
authors.forename: K L
authors.initials: KL
authors.lastname: Deuchars
authors.forename: G J
authors.initials: GJ
authors.lastname: Goldenberg
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000096:biosynthesis* / Q000235:genetics; D004317:Doxorubicin / Q000633:toxicity*; D019008:Drug Resistance, Neoplasm; D005822:Genetic Vectors; D006801:Humans; D007941:Leukemia P388; D051379:Mice; D018168:Receptors, Retinoic Acid / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D000072482:Retinoic Acid Receptor alpha; D014162:Transfection; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
chemical_list: D000970:Antineoplastic Agents; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins; D000072482:Retinoic Acid Receptor alpha; D004317:Doxorubicin; D004250:DNA Topoisomerases, Type II