title: Heat-directed suicide gene therapy for breast cancer.
abstract: Adjuvant hyperthermia can improve treatment outcome for locally recurrent breast cancer (LRBC). Previously, we demonstrated that infection of human breast cancer cells with a recombinant adenovirus expressing beta-galactosidase from the human hsp70b gene promoter (Ad.70b.betagal) results in 50- to 800-fold increases in reporter gene expression following heat treatment (30 minutes at 43 degrees C). Here, we describe a heat-directed suicide gene therapy strategy based on an adenoviral vector (Ad.70b.CDTK) in which expression of the dual prodrug-activating E. coli cytosine deaminase/herpes simplex virus thymidine kinase (CDTK) fusion gene is under the control of the hsp70b promoter. Treatment of T47D and MCF-7 breast cancer cells with mild hyperthermia (43 degrees C/30 minutes) and prodrugs (100 microg/ml 5-fluorocytosine and 10 microg/ml ganciclovir) following infection with Ad.70b.CDTK (10-100 PFU/cell) resulted in 30- to 60-fold decreases in clonogenic survival relative to control cultures treated with heat or prodrugs alone. Clonogenic survival declined even further (up to 240-fold) following heat treatment at 41.5 degrees C for 120 minutes. A decreased clonogenic survival was accompanied by tumor cell apoptosis. These results demonstrate that this combined treatment strategy can be highly effective against heat- and radiation-resistant breast tumor cells and supports the continued development of heat-directed CDTK suicide gene therapy strategies for LRBC.
authors.affiliation: Department of Medical Biophysics, University of Toronto, 610 University Avenue, Toronto, Ontario, M5G 2M9 Canada.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Brade
authors.forename: Paul
authors.initials: P
authors.lastname: Szmitko
authors.forename: Duc
authors.initials: D
authors.lastname: Ngo
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Liu
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Klamut
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000628:therapy*; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D043525:Cytosine Deaminase / Q000235:genetics / Q000378:metabolism; D005260:Female; D015316:Genetic Therapy; D006801:Humans; D006979:Hyperthermia, Induced; D011355:Prodrugs / Q000627:therapeutic use; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism
chemical_list: D011355:Prodrugs; D011993:Recombinant Fusion Proteins; D013937:Thymidine Kinase; C092717:thymidine kinase 1; D043525:Cytosine Deaminase