Molecular Therapy
Volume 17, Issue 11, November 2009, Pages 1929-1937
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Original Article
Genotoxic Potential of Lineage-specific Lentivirus Vectors Carrying the β-Globin Locus Control Region

https://doi.org/10.1038/mt.2009.183Get rights and content
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Insertional mutagenesis by long terminal repeat (LTR) enhancers in γ-retrovirus-based vectors (GVs) in clinical trials has prompted deeper investigations into vector genotoxicity. Experimentally, self-inactivating (SIN) lentivirus vectors (LVs) and GV containing internal promoters/enhancers show reduced genotoxicity, although strong ubiquitously-active enhancers dysregulate genes independent of vector type/design. Herein, we explored the genotoxicity of β-globin (BG) locus control region (LCR), a strong long-range lineage-specific-enhancer, with/without insulator (Ins) elements in LV using primary hematopoietic progenitors to generate in vitro immortalization (IVIM) assay mutants. LCR-containing LV had ~200-fold lower transforming potential, compared to the conventional GV. The LCR perturbed expression of few genes in a 300 kilobase (kb) proviral vicinity but no upregulation of genes associated with cancer, including an erythroid-specific transcription factor occurred. A further twofold reduction in transforming activity was observed with insulated LCR-containing LV. Our data indicate that toxicology studies of LCR-containing LV in mice will likely not yield any insertional oncogenesis with the numbers of animals that can be practically studied.

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published online 25 August 2009

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T.H. and F.U. contributed equally to this work; C.B. and P.M. are co-corresponding authors contributed equally to this work.