Retroviral gene transfer to primitive normal and leukemic hematopoietic cells using clinically applicable procedures.
Clinical uses of gene transfer to bone marrow transplants require the establishment of a reproducible method for infecting large numbers of very primitive hematopoietic cells at high efficiency using cell-free retrovirus-containing media. In this study we report the results of experiments with preparations of a high-titer (2-5 x 10(7)/ml) helper-free recombinant neo(r) retrovirus that indicate this goal can now be achieved based on measurements of gene transfer efficiencies to cells referred to as long-term culture initiating cells (LTC-IC) because they give rise to clonogenic cells after greater than or equal to 5 wk in long-term culture (LTC). Intermittent, repeated exposure of normal human marrow mononuclear cells to virus-containing supernatant over a 3-d period of cell maintenance on an IL-3/granulocyte colony-stimulating factor (G-CSF) producing stromal layer resulted in gene transfer efficiencies to LTC-IC of 41%; a level previously obtainable only using co-cultivation infection techniques. Marrow cells enriched greater than or equal to 500-fold for LTC-IC (1-2% pure) by flow cytometry showed gene transfer efficiencies of 27% when infected in a similar fashion over a shorter period (24 h), but in the presence of added soluble IL-3 and G-CSF without stromal feeders, and this increased to 61% when Steel factor was also present during the infection period. By using a less highly enriched population of LTC-IC obtained by a bulk immunoselection technique applicable to large-scale clinical marrow harvests, gene transfer efficiencies to LTC-IC of 40% were achieved and this was increased to 60% by short-term preselection in G418. Southern analysis of DNA from the nonadherent cells produced by these LTC over a 6-wk period provided evidence of clonal evolution of LTC-IC in vitro. Leukemic chronic myelogenous leukemia LTC-IC were also infected at high efficiency using the same supernatant infection strategy with growth factor supplementation. These data demonstrate the feasibility of using cell-free virus preparations for infecting clinical marrow samples suitable for transplantation, as well as for further analysis of human marrow stem cell dynamics in vitro.
Hughes
P F
PF
Terry Fox Laboratory, B. C. Cancer Agency, Vancouver, Canada.
Thacker
J D
JD
Hogge
D
D
Sutherland
H J
HJ
Thomas
T E
TE
Lansdorp
P M
PM
Eaves
C J
CJ
Humphries
R K
RK
D001483:Base Sequence; D015139:Blotting, Southern; D004247:DNA; D006412:Hematopoietic Stem Cells / Q000382:microbiology; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics*; D008969:Molecular Sequence Data; D009355:Neomycin / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012190:Retroviridae / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured
D004247:DNA; D009355:Neomycin