Leukemias following retroviral transfer of multidrug resistance 1 (MDR1) are driven by combinatorial insertional mutagenesis

• Published in: Blood 2005-06, Vol.105 (11), p.4235-4246
• Main Authors: Modlich, Ute, Kustikova, Olga S., Schmidt, Manfred, Rudolph, Cornelia, Meyer, Johann, Li, Zhixiong, Kamino, Kenji, von Neuhoff, Nils, Schlegelberger, Brigitte, Kuehlcke, Klaus, Bunting, Kevin D., Schmidt, Sonja, Deichmann, Annette, von Kalle, Christof, Fehse, Boris, Baum, Christopher
• Format: Article
• Language: English
• Subjects: Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Animals; Applied cell therapy and gene therapy; ATP Binding Cassette Transporter, Subfamily B, Member 1 - administration & dosage; Biological and medical sciences; Gene Dosage; Gene Transfer Techniques - adverse effects; Genes, MDR - genetics; Genetic Therapy - adverse effects; Genetic Vectors - adverse effects; Hematologic and hematopoietic diseases; Leukemia - etiology; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Medical sciences; Mice; Mice, Inbred C57BL; Mutagenesis, Insertional; Retroviridae - genetics; Transfusions. Complications. Transfusion reactions. Cell and gene therapy; Translocation, Genetic
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2004-11-4535

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.