title: Leukemias following retroviral transfer of multidrug resistance 1 (MDR1) are driven by combinatorial insertional mutagenesis.
abstract: 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.
authors.affiliation: Department of Hematology, Hemostaseology and Oncology, Institute of Cellular and Molecular Pathology, Hannover Medical School, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Modlich
authors.forename: Olga S
authors.initials: OS
authors.lastname: Kustikova
authors.forename: Manfred
authors.initials: M
authors.lastname: Schmidt
authors.forename: Cornelia
authors.initials: C
authors.lastname: Rudolph
authors.forename: Johann
authors.initials: J
authors.lastname: Meyer
authors.forename: Zhixiong
authors.initials: Z
authors.lastname: Li
authors.forename: Kenji
authors.initials: K
authors.lastname: Kamino
authors.forename: Nils
authors.initials: N
authors.lastname: von Neuhoff
authors.forename: Brigitte
authors.initials: B
authors.lastname: Schlegelberger
authors.forename: Klaus
authors.initials: K
authors.lastname: Kuehlcke
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Bunting
authors.forename: Sonja
authors.initials: S
authors.lastname: Schmidt
authors.forename: Annette
authors.initials: A
authors.lastname: Deichmann
authors.forename: Christof
authors.initials: C
authors.lastname: von Kalle
authors.forename: Boris
authors.initials: B
authors.lastname: Fehse
authors.forename: Christopher
authors.initials: C
authors.lastname: Baum
mesh_terms: 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
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1