1. ¹Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
2. ²Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
3. ³Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN, USA
4. ⁴Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
5. ⁵Department of Neurology, Indiana University School of Medicine, Indianapolis, IN, USA
6. ⁶Department of Pathology, Indiana University School of Medicine, Indianapolis, IN, USA
7. ⁷Department of Pediatric Oncology, Dana-Farber Cancer Institute and Children's Hospital, Boston, MA, USA
8. ⁸Department of Pediatrics, Duke University, Durham, NC, USA
9. ⁹Division of Experimental Hematology, Cincinnati Children's Research Foundation and Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA
10. ¹⁰Department of Pharmacology, Indiana University School of Medicine, Indianapolis, IN, USA

Correspondence: Dr K Cornetta, Department of Medical and Molecular Genetics, Indiana University School of Medicine, IB 130, 975 W Walnut Street, Indianapolis, IN 46202, USA. E-mail: kcornett@iupui.edu

¹¹These authors contributed equally to this work.

Received 18 November 2005; Revised 6 February 2006; Accepted 5 March 2006; Published online 28 April 2006.

Abstract

Administration of chemotherapy is often limited by myelosuppression. Expression of drug-resistance genes in hematopoietic cells has been proposed as a means to decrease the toxicity of cytotoxic agents. In this pilot study, we utilized a retroviral vector expressing methylguanine DNA methyltransferase (MGMT) to transduce hematopoietic progenitors, which were subsequently used in the setting of alkylator therapy (procarbazine, CCNU, vincristine (PCV)) for poor prognosis brain tumors. Granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood progenitor cells were collected by apheresis and enriched for CD34+ expression. Nine subjects were infused with CD34+-enriched cells treated in a transduction procedure involving a 4-day exposure to cytokines with vector exposure on days 3 and 4. No major adverse event was related to the gene therapy procedure. Importantly, the engraftment kinetics of the treated product was similar to unmanipulated peripheral blood stem cells, suggesting that the ex vivo manipulation did not significantly reduce engrafting progenitor cell function. Gene-transduced cells were detected in all subjects. Although the level and duration was limited, patients receiving cells transduced using fibronectin 'preloaded' with virus supernatant appeared to show improved in vivo marking frequency. These findings demonstrate the feasibility and safety of utilizing MGMT-transduced CD34+ peripheral blood progenitor cells in the setting of chemotherapy.