title: Adenovirus-mediated human topoisomerase IIalpha gene transfer increases the sensitivity of etoposide-resistant human breast cancer cells.
abstract: Cellular resistance to chemotherapeutic agents is attributable to several mechanisms, including alteration of topoisomerase IIalpha (topo IIalpha) gene expression. Etoposide-resistant MDA-VP human breast cancer cells express lower amounts of enzymatically active and drug-sensitive topo IIalpha than do MDA parent cells, suggesting that the low level of topo IIalpha is the mechanism of resistance. To determine whether transfer of a normal topo IIalpha gene into MDA-VP cells can increase topo IIalpha gene expression, topo IIalpha protein production, and cell sensitivity to etoposide, a recombinant adenovirus, Ad-hTopoIIalpha, containing the human topo IIalpha gene, was constructed. The shuttle vector pAvCvSv-hTopIIalpha was constructed and co-transfected with the pBHG10 packaging vector into 293 cells. Infectious recombinant adenovirus plaques were isolated and purified. Presence of the topo IIalpha gene was confirmed by PCR and restriction enzyme digestion. After infection with Ad-hTopoIIalpha, topo IIalpha mRNA expression in MDA-VP cells increased 7.4-fold, topo IIalpha protein production increased 5.9-fold, and sensitivity to etoposide was enhanced 4.5-fold compared with control transfected cells. Infection of normal human embryonic lung cells and human fibroblast cells with Ad-hTopoIIalpha did not enhance the expression of topo IIalpha or sensitivity to etoposide. Viral uptake was comparable in the MDA-VP and normal cell lines. These data suggest that topo IIalpha gene transfer using an adenoviral vector can selectively increase etoposide sensitivity in drug-resistant tumor cells and may enhance the therapeutic index of etoposide.
authors.affiliation: Department of Cancer Biology, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Zhou
authors.forename: L A
authors.initials: LA
authors.lastname: Zwelling
authors.forename: Y
authors.initials: Y
authors.lastname: Kawakami
authors.forename: T
authors.initials: T
authors.lastname: An
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: C
authors.initials: C
authors.lastname: Herzog
authors.forename: E S
authors.initials: ES
authors.lastname: Kleinerman
mesh_terms: D000256:Adenoviridae; D000951:Antigens, Neoplasm; D001943:Breast Neoplasms; D002470:Cell Survival / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000633:toxicity*; D005260:Female; D005822:Genetic Vectors; D006801:Humans; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection / Q000379:methods
chemical_list: D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D005047:Etoposide; D004250:DNA Topoisomerases, Type II