title: Improvement of antitumor activity by gene amplification with a replicating but nondisseminating adenovirus.
abstract: Gene therapy is a promising approach for cancer treatment; however, efficacy of current vectors remains insufficient. To improve the success of suicide gene therapy, we constructed a replication-competent adenoviral vector that has its protease gene deleted and expresses bacterial cytosine deaminase fused with bacterial uracil phosphoribosyltransferase (CU). The prodrug, 5-fluorocytosine, is transformed into the highly toxic and tissue-diffusible 5-fluorouracil by CU in infected cells. This vector is incapable of producing infectious particles but is able to undergo a single round of replication, thereby increasing transgene copy number and expression. In the presence of 5-FC, compared with the first-generation vector (AdCU), the replication-competent vector, Ad(dPS)CU-IRES-E1A, was significantly more efficacious for in vitro tumor cell killing and in bystander assays, whereas 25-fold fewer viral particles were required in a three-dimensional spheroid model. For in vivo experiments, in which virus was injected into preestablished intracranial glioma xenografts, followed by 5-FC treatment, mice receiving Ad(dPS)CU-IRES-E1A had significantly smaller tumors at 35 days postinjection as well as significantly longer median survival than mice treated with the replication-deficient, protease-deleted vector [Ad(dPS)CU]. In an immunocompetent syngeneic model, Ad(dPS)CU + 5-FC-treated mice had a median survival of only 23 days, whereas Ad(dPS)CU-IRES-E1A + 5-FC-treated animals had a survival of 57.1% at 365 days. In conclusion, Ad(dPS)CU-IRES-E1A in the presence of 5-FC produces more potent tumoricidal effects than its replication-deficient counterparts.
authors.affiliation: Groupe de Vecteurs de Génomique et Thérapie Génique, Biotechnology Research Institute, National Research Council, Montreal, QC, Canada.
authors.forename: Denis
authors.initials: D
authors.lastname: Bourbeau
authors.forename: Cara Jean
authors.initials: CJ
authors.lastname: Lau
authors.forename: Jairo
authors.initials: J
authors.lastname: Jaime
authors.forename: Zafiro
authors.initials: Z
authors.lastname: Koty
authors.forename: Simone P
authors.initials: SP
authors.lastname: Zehntner
authors.forename: Geneviève
authors.initials: G
authors.lastname: Lavoie
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Mes-Masson
authors.forename: Josephine
authors.initials: J
authors.lastname: Nalbantoglu
authors.forename: Bernard
authors.initials: B
authors.lastname: Massie
mesh_terms: D000256:Adenoviridae / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D000818:Animals; D045744:Cell Line, Tumor; D043525:Cytosine Deaminase / Q000235:genetics / Q000378:metabolism; D005437:Flucytosine / Q000493:pharmacokinetics; D005472:Fluorouracil / Q000493:pharmacokinetics / Q000494:pharmacology; D005784:Gene Amplification; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D016679:Genome, Viral; D005909:Glioblastoma / Q000235:genetics / Q000628:therapy*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D010430:Pentosyltransferases / Q000235:genetics / Q000378:metabolism; D010447:Peptide Hydrolases / Q000172:deficiency* / Q000235:genetics; D018874:Spheroids, Cellular; D019076:Transgenes; D014779:Virus Replication
chemical_list: D005437:Flucytosine; D010430:Pentosyltransferases; C023269:uracil phosphoribosyltransferase; D010447:Peptide Hydrolases; D043525:Cytosine Deaminase; D005472:Fluorouracil