title: Effective suicide gene therapy for leukemia in a model of insertional oncogenesis in mice.
abstract: The safety of gene therapy using hematopoietic stem cells may be increased by including a suicide gene in the therapeutic vector to eliminate adverse events like insertional oncogenesis while retaining the clinical benefits. We have developed a model of experimental insertional oncogenesis by transducing the murine factor-dependent leukemia cell line Ba/F3 with a bicistronic Moloney murine leukemia virus retroviral vector encoding a murine oncogene (cKit(D814V)) in addition to one of three suicide genes: Herpes simplex virus thymidine kinase (HSV-TK); SR39, an HSV-TK mutant with an increased affinity for the drug substrate Ganciclovir (GCV); or sc39, a splice-corrected version of SR39. Following intravenous challenge with transduced Ba/F3 clones and treatment with GCV, leukemia developed in mice given cells expressing HSV-TK, but not SR39 or sc39. In vitro GCV resistance was observed in heterogeneously transduced Ba/F3 pools at 2.5-14%, and single-nucleotide changes or partial loss of the suicide gene were identified as mechanisms of drug escape. However, GCV treatment resulted in 80-100% survival of mice challenged even with pools of partially resistant Ba/F3 cells expressing SR39 or sc39. Thus, in this model of vector-driven insertional oncogenesis, a suicide gene approach was effective for eliminating leukemia using modified HSV-TK variants with improved biological activity.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Southern California, Keck School of Medicine, University of Los Angeles, California, USA.
authors.forename: Martina
authors.initials: M
authors.lastname: Blumenthal
authors.forename: Dianne
authors.initials: D
authors.lastname: Skelton
authors.forename: Karen A
authors.initials: KA
authors.lastname: Pepper
authors.forename: Thomas
authors.initials: T
authors.lastname: Jahn
authors.forename: Emily
authors.initials: E
authors.lastname: Methangkool
authors.forename: Donald B
authors.initials: DB
authors.lastname: Kohn
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic; D004195:Disease Models, Animal; D015774:Ganciclovir / Q000494:pharmacology; D041722:Genes, Transgenic, Suicide / Q000235:genetics*; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D007938:Leukemia / Q000235:genetics* / Q000473:pathology / Q000628:therapy*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009857:Oncogenes / Q000235:genetics*; D012680:Sensitivity and Specificity; D015996:Survival Rate
chemical_list: D015774:Ganciclovir