Importance of murine study design for testing toxicity of retroviral vectors in support of phase I trials.
Although retroviral vectors are one of the most widely used vehicles for gene transfer, there is no uniformly accepted pre-clinical model defined to assess their safety, in particular their risk related to insertional mutagenesis. In the murine pre-clinical study presented here, 40 test and 10 control mice were transplanted with ex vivo manipulated bone marrow cells to assess the long-term effects of the transduction of hematopoietic cells with the retroviral vector MSCV-MGMT(P140K)wc. Test mice had significant gene marking 8-12 months post-transplantation with an average of 0.93 vector copies per cell and 41.5% of peripheral blood cells expressing the transgene MGMT(P140K), thus confirming persistent vector expression. Unexpectedly, six test mice developed malignant lymphoma. No vector was detected in the tumor cells of five animals with malignancies, indicating that the malignancies were not caused by insertional mutagenesis or MGMT(P140K) expression. Mice from a concurrent study with a different transgene also revealed additional cases of vector-negative lymphomas of host origin. We conclude that the background tumor formation in this mouse model complicates safety determination of retroviral vectors and propose an improved study design that we predict will increase the relevance and accuracy of interpretation of pre-clinical mouse studies.
Will
Elke
E
Division of Experimental Hematology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
Bailey
Jeff
J
Schuesler
Todd
T
Modlich
Ute
U
Balcik
Brenden
B
Burzynski
Ben
B
Witte
David
D
Layh-Schmitt
Gerlinde
G
Rudolph
Cornelia
C
Schlegelberger
Brigitte
B
von Kalle
Christof
C
Baum
Christopher
C
Sorrentino
Brian P
BP
Wagner
Lars M
LM
Kelly
Patrick
P
Reeves
Lilith
L
Williams
David A
DA
D000818:Animals; D001483:Base Sequence; D016026:Bone Marrow Transplantation / Q000009:adverse effects; D017321:Clinical Trials, Phase I as Topic / Q000379:methods; D015342:DNA Probes / Q000235:genetics; D015316:Genetic Therapy / Q000009:adverse effects*; D005822:Genetic Vectors / Q000633:toxicity*; D006410:Hematopoiesis; D006801:Humans; D008223:Lymphoma / Q000209:etiology / Q000235:genetics / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016254:Mutagenesis, Insertional; D012107:Research Design; D012190:Retroviridae / Q000235:genetics*; D012449:Safety; D014161:Transduction, Genetic
D015342:DNA Probes