Retroviral mediated gene transfer in chronic myelogenous leukaemia

Gene therapy for chronic myelogenous leukaemia (CML) may provide a therapeutic option for patients who are ineligible for bone marrow transplantation. To determine the feasibility of such an approach we evaluated the transduction efficiency of CML progenitor colonies from seven patients in chronic phase. Vector transduction was optimized using the CML-derived K562 cell line and applied to CML mononuclear cells. After vector exposure, optimal gene transfer was noted when CML mononuclear cell cultures contained stem cell factor, IL-3, GM-CSF and erythropoietin. The addition of IL-6 to this combination decreased transduction efficiency. Using these conditions, 20.4% ± 2.4 (SE) of erythroid colonies (CFU-GEMM and BFU-E) and 20.2% ± 4.7 of CFU-GM colonies were G418 resistant. This compares with a transduction efficiency of 5.9% ± 1.1 and 6.4% ± 1.5, respectively, for erythroid and CFU-GM colonies using marrow obtained from normal donors. Only a modest increase in gene transfer was noted when CML cells were stimulated with cytokines for the 24 h preceding vector exposure. Vector DNA in colonies expressing the BCR/ABL transcript was documented by performing PCR analysis on individual colonies. The relatively high gene transfer rate in CML suggests that this disease might be very suitable for gene therapy.