Gene transfer efficiency and leukemia development
Group . | Mouse no. . | Transgene expression before BMT, % . | Frequency of transgene expression after BMT, frequency (% expression in positive mice) . | Mean transfer efficiency, by PCR, % . | Outcome . |
|---|---|---|---|---|---|
| Experiment I | |||||
| SF91m3 supernatants (LD) | 17-25, n = 9 | 16 | 0/9 mice | 5 | Healthy |
| HaMDR1 supernatants (LD) | 8-16, n = 8 | 15 | 2/8 mice (8) | 14 | Healthy |
| SF91PdsRED2 supernatants (HD) | 1-7, n = 7 | 75 | 7/7 mice (80-90) | 420 | 1 leukemia (L5) |
| HaMDR1 coculture (HD) | 26-31, n = 6 | 30 | 3/6 mice (6) | 147 | 2 leukemias (L29, L31); 1 recipient-type leukemia after secondary BMT (L28.2) |
| Experiment II | |||||
| SF91m3 supernatants (LD) | 54-61, n = 8 | 10 | 1/8 mice (8) | < 1 | Healthy |
| HaMDR1 supernatants (LD) | 64-69, n = 6 | 30 | 1/6 mice (9) | 10 | Healthy |
| SF11tCD34 supernatants (LD) | 48-53, n = 6 | 30 | 6/6 mice (8) | ND | Healthy |
| Experiment III | |||||
| HaMDR1 coculture + in vitro expansion (HD) | 40-47, n = 8 | 65 | 6/8 mice (10) | 1100 | 5 leukemias (L40, L43, L44, L45, L46) |
| Mock-transduced + in vitro expansion | 32-39, n = 8 | — | 0/8 mice | 0 | Healthy |
Group . | Mouse no. . | Transgene expression before BMT, % . | Frequency of transgene expression after BMT, frequency (% expression in positive mice) . | Mean transfer efficiency, by PCR, % . | Outcome . |
|---|---|---|---|---|---|
| Experiment I | |||||
| SF91m3 supernatants (LD) | 17-25, n = 9 | 16 | 0/9 mice | 5 | Healthy |
| HaMDR1 supernatants (LD) | 8-16, n = 8 | 15 | 2/8 mice (8) | 14 | Healthy |
| SF91PdsRED2 supernatants (HD) | 1-7, n = 7 | 75 | 7/7 mice (80-90) | 420 | 1 leukemia (L5) |
| HaMDR1 coculture (HD) | 26-31, n = 6 | 30 | 3/6 mice (6) | 147 | 2 leukemias (L29, L31); 1 recipient-type leukemia after secondary BMT (L28.2) |
| Experiment II | |||||
| SF91m3 supernatants (LD) | 54-61, n = 8 | 10 | 1/8 mice (8) | < 1 | Healthy |
| HaMDR1 supernatants (LD) | 64-69, n = 6 | 30 | 1/6 mice (9) | 10 | Healthy |
| SF11tCD34 supernatants (LD) | 48-53, n = 6 | 30 | 6/6 mice (8) | ND | Healthy |
| Experiment III | |||||
| HaMDR1 coculture + in vitro expansion (HD) | 40-47, n = 8 | 65 | 6/8 mice (10) | 1100 | 5 leukemias (L40, L43, L44, L45, L46) |
| Mock-transduced + in vitro expansion | 32-39, n = 8 | — | 0/8 mice | 0 | Healthy |
— indicates not applicable.
Overview of the experimental groups. Three independent experiments were performed (experiments I-III), containing 4, 3, and 2 groups of mice that underwent transplantation with bone marrow cells that were transduced by different retroviral vectors. Note that the efflux assays used to detect MDR1 transgene expression may not be as sensitive as detection of dsRED2 or tCD34 by flow cytometry. Data in the fourth column show the frequency of mice expressing the transgene and the average expression level in the positive animals. In an independent experiment involving 20 primary recipients observed for one year and serial BMT into secondary animals observed for another 7 months, no evidence was obtained for a leukemogenic capacity of SF91PdsRED2 under LD conditions (data not shown).
BMT indicates bone marrow transplantation; LD, low-dose gene transfer; HD, high-dose gene transfer according to in vivo marking rates (based on PCR) determined 9 weeks after BMT.