title: The genotoxic potential of retroviral vectors is strongly modulated by vector design and integration site selection in a mouse model of HSC gene therapy.
abstract: gamma-Retroviral vectors (gammaRVs), which are commonly used in gene therapy, can trigger oncogenesis by insertional mutagenesis. Here, we have dissected the contribution of vector design and viral integration site selection (ISS) to oncogenesis using an in vivo genotoxicity assay based on transplantation of vector-transduced tumor-prone mouse hematopoietic stem/progenitor cells. By swapping genetic elements between gammaRV and lentiviral vectors (LVs), we have demonstrated that transcriptionally active long terminal repeats (LTRs) are major determinants of genotoxicity even when reconstituted in LVs and that self-inactivating (SIN) LTRs enhance the safety of gammaRVs. By comparing the genotoxicity of vectors with matched active LTRs, we were able to determine that substantially greater LV integration loads are required to approach the same oncogenic risk as gammaRVs. This difference in facilitating oncogenesis is likely to be explained by the observed preferential targeting of cancer genes by gammaRVs. This integration-site bias was intrinsic to gammaRVs, as it was also observed for SIN gammaRVs that lacked genotoxicity in our model. Our findings strongly support the use of SIN viral vector platforms and show that ISS can substantially modulate genotoxicity.
authors.affiliation: San Raffaele-Telethon Institute for Gene Therapy, via Olgettina 58, 20132 Milan, Italy. montini.eugenio@hsr.it
authors.forename: Eugenio
authors.initials: E
authors.lastname: Montini
authors.forename: Daniela
authors.initials: D
authors.lastname: Cesana
authors.forename: Manfred
authors.initials: M
authors.lastname: Schmidt
authors.forename: Francesca
authors.initials: F
authors.lastname: Sanvito
authors.forename: Cynthia C
authors.initials: CC
authors.lastname: Bartholomae
authors.forename: Marco
authors.initials: M
authors.lastname: Ranzani
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Benedicenti
authors.forename: Lucia Sergi
authors.initials: LS
authors.lastname: Sergi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Ambrosi
authors.forename: Maurilio
authors.initials: M
authors.lastname: Ponzoni
authors.forename: Claudio
authors.initials: C
authors.lastname: Doglioni
authors.forename: Clelia
authors.initials: C
authors.lastname: Di Serio
authors.forename: Christof
authors.initials: C
authors.lastname: von Kalle
authors.forename: Luigi
authors.initials: L
authors.lastname: Naldini
mesh_terms: D000818:Animals; D001483:Base Sequence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000172:deficiency / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D017988:Gammaretrovirus / Q000235:genetics* / Q000472:pathogenicity*; D019942:Genes, p16; D015316:Genetic Therapy / Q000009:adverse effects* / Q000379:methods; D005822:Genetic Vectors / Q000009:adverse effects*; D018380:Hematopoietic Stem Cell Transplantation / Q000009:adverse effects; D016086:Lentivirus / Q000235:genetics / Q000472:pathogenicity; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009154:Mutation; D009374:Neoplasms, Experimental / Q000209:etiology / Q000235:genetics; D020079:Terminal Repeat Sequences
chemical_list: C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; D017931:DNA Primers