Leukemias following retroviral transfer of multidrug resistance 1 (MDR1) are driven by combinatorial insertional mutagenesis.
Previous studies have demonstrated leukemic complications in mice after high-copy retroviral gene transfer of the multidrug resistance 1 (MDR1) cDNA, encoding a membrane-located efflux pump expressed in hematopoietic stem cells. In contrast, no such complications or MDR1-associated alterations of hematopoiesis were observed in numerous other studies exploring MDR1 gene transfer into cell lines, mice, dogs, nonhuman primates, and human subjects. Here, we show that leukemias associated with retroviral expression of MDR1 depend on high vector dose, and involve the selection of clones with combinatorial insertional mutagenesis of proto-oncogenes or other signaling genes. Compared with insertion patterns in normal long-term repopulating hematopoietic cells, such hits were overrepresented in leukemic clones, pointing to a causal role. A similar constellation of insertion sites was also observed in a leukemia arising after high-copy retroviral gene transfer of a fluorescent protein. Spectral karyotyping demonstrated additional chromosomal translocations in a subset of cases, indicative of secondary genetic instability. We also show that insertional mutants can be amplified in vitro prior to transplantation. On the basis of these findings, we suggest the use of preclinical dose-escalation studies to define a therapeutic index for retroviral transgene delivery.
Modlich
Ute
U
Department of Hematology, Hemostaseology and Oncology, Institute of Cellular and Molecular Pathology, Hannover Medical School, Germany.
Kustikova
Olga S
OS
Schmidt
Manfred
M
Rudolph
Cornelia
C
Meyer
Johann
J
Li
Zhixiong
Z
Kamino
Kenji
K
von Neuhoff
Nils
N
Schlegelberger
Brigitte
B
Kuehlcke
Klaus
K
Bunting
Kevin D
KD
Schmidt
Sonja
S
Deichmann
Annette
A
von Kalle
Christof
C
Fehse
Boris
B
Baum
Christopher
C
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000008:administration & dosage*; D000818:Animals; D018628:Gene Dosage; D018014:Gene Transfer Techniques / Q000009:adverse effects*; D019450:Genes, MDR / Q000235:genetics; D015316:Genetic Therapy / Q000009:adverse effects; D005822:Genetic Vectors / Q000009:adverse effects; D007938:Leukemia / Q000209:etiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D016254:Mutagenesis, Insertional; D012190:Retroviridae / Q000235:genetics*; D014178:Translocation, Genetic
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1