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Mol Ther. 2016 Jun;24(6):1090-1099. doi: 10.1038/mt.2016.55. Epub 2016 Mar 9.

Evaluating the Safety of Retroviral Vectors Based on Insertional Oncogene Activation and Blocked Differentiation in Cultured Thymocytes.

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Division of Experimental Hematology, Department of Hematology, Memphis, Tennessee, USA.
Department of Computational Biology, Memphis, Tennessee, USA.
Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.
Division of Experimental Hematology, Department of Hematology, Memphis, Tennessee, USA. Electronic address:


Insertional oncogenesis due to retroviral (RV) vector integration has caused recurrent leukemia in multiple gene therapy trials, predominantly due to vector integration effects at the LMO2 locus. While currently available preclinical safety models have been used for evaluating vector safety, none have predicted or reproduced the recurrent LMO2 integrations seen in previous X-linked severe combined immunodeficiency (X-SCID) and Wiskott-Aldrich clinical gene therapy trials. We now describe a new assay for assessing vector safety that recapitulates naturally occurring insertions into Lmo2 and other T-cell proto-oncogenes leading to a preleukemic developmental arrest in primary murine thymocytes cultured in vitro. This assay was used to compare the relative oncogenic potential of a variety of gamma-RV and lentiviral vectors and to assess the risk conferred by various transcriptional elements contained in these genomes. Gamma-RV vectors that contained full viral long-terminal repeats were most prone to causing double negative 2 (DN2) arrest and led to repeated cases of Lmo2 pathway activation, while lentiviral vectors containing these same elements were significantly less prone to activate proto-oncogenes or cause DN2 arrest. This work provides a new preclinical assay that is especially relevant for assessing safety in SCID disorders and provides a new tool for designing safer RV vectors.

[Indexed for MEDLINE]
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