Lymphomagenesis in SCID-X1 mice following lentivirus-mediated phenotype correction independent of insertional mutagenesis and gammac overexpression.
The development of leukemia as a consequence of vector-mediated genotoxicity in gene therapy trials for X-linked severe combined immunodeficiency (SCID-X1) has prompted substantial research effort into the design and safety testing of integrating vectors. An important element of vector design is the selection and evaluation of promoter-enhancer elements with sufficient strength to drive reliable immune reconstitution, but minimal propensity for enhancer-mediated insertional mutagenesis. In this study, we set out to explore the effect of promoter-enhancer selection on the efficacy and safety of human immunodeficiency virus-1-derived lentiviral vectors in gammac-deficient mice. We observed incomplete or absent T- and B-cell development in mice transplanted with progenitors expressing gammac from the phosphoglycerate kinase (PGK) and Wiscott-Aldrich syndrome (WAS) promoters, respectively. In contrast, functional T- and B-cell compartments were restored in mice receiving an equivalent vector containing the elongation factor-1-alpha (EF1alpha) promoter; however, 4 of 14 mice reconstituted with this vector subsequently developed lymphoma. Extensive analyses failed to implicate insertional mutagenesis or gammac overexpression as the underlying mechanism. These findings highlight the need for detailed mechanistic analysis of tumor readouts in preclinical animal models assessing vector safety, and suggest the existence of other ill-defined risk factors for oncogenesis, including replicative stress, in gene therapy protocols targeting the hematopoietic compartment.
Ginn
Samantha L
SL
Gene Therapy Research Unit of the Children's Medical Research Institute and The Children's Hospital at Westmead, Westmead, New South Wales, Australia.
Liao
Sophia H Y
SH
Dane
Allison P
AP
Hu
Min
M
Hyman
Jessica
J
Finnie
John W
JW
Zheng
Maolin
M
Cavazzana-Calvo
Marina
M
Alexander
Stephen I
SI
Thrasher
Adrian J
AJ
Alexander
Ian E
IE
D000818:Animals; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015316:Genetic Therapy / Q000009:adverse effects; D005822:Genetic Vectors / Q000009:adverse effects / Q000235:genetics; D053631:Interleukin Receptor Common gamma Subunit / Q000235:genetics / Q000502:physiology*; D016086:Lentivirus / Q000235:genetics*; D008223:Lymphoma / Q000209:etiology* / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D016254:Mutagenesis, Insertional; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D053632:X-Linked Combined Immunodeficiency Diseases / Q000235:genetics / Q000628:therapy*
D053631:Interleukin Receptor Common gamma Subunit