INFLUENCE OF RETROVIRAL-MEDIATED GENE TRANSDUCTION OF BOTH THE RECOMBINANT-HUMAN-ERYTHROPOIETIN RECEPTOR AND INTERLEUKIN-9 RECEPTOR GENES INTO SINGLE CD34-OR LOW CORD-BLOOD CELLS ON CYTOKINE-STIMULATED ERYTHROID COLONY FORMATION(+CD33)

Introduction of genes for cytokine receptors into hematopoietic stem/p rogenitor cells (HSC/HPC) may be of clinical use in the future. We rec ently reported that retroviral-mediated transduction of either the hum an erythropoietin receptor (hEpoR) or interleukin-9 receptor (hIL-9R) genes into highly purified HSC/HPC from cord blood (CB) resulted in in creased numbers of detectable cytokine-responsive erythroid progenitor s (burst-forming units-erythroid [BFU-E]). In the present study, we ev aluated if this increase could be further enhanced by cotransducing bo th these genes into single isolated HSC/HPC. Single CD34(++)CD33(-or l ow)-expressing cells from CB were transduced with viral supernatant co ntaining the hEpoR or hIL-9R genes or cotransduced with both genes. In the presence of Steel factor (SLF), interleukin-3 (IL-3), granulocyte -macrophage colony-stimulating factor (GM-CSF), erythropoietin (Epo), and IL-9, the numbers of erythroid colonies formed were significantly increased after transduction of cells with either the hIL-9R or hEpoR gene compared to mock-transduced cells. This increase was significantl y enhanced in cells cotransduced with both genes compared with either gene alone. Integration and expression of both genes was confirmed by polymerase chain reaction (PCR) and reverse-transcriptase (RT)-PCR ana lysis, respectively. The data demonstrate that myeloid progenitors can be transduced at the single-cell level with both hEpoR and hIL-9R gen es with resultant enhanced proliferation of these progenitors in the e rythroid lineage by combinations of cytokines including Epo and IL-9.