In vivo manipulation of interleukin-2 expression by a retroviral tetracycline (tet)-regulated system.
We have used the tetracycline (tet)-regulated system as described previously to evaluate the applicability of controlled gene expression in cancer gene therapy. As a model gene, we used the human interleukin-2 (IL-2) gene, which has been placed under the transcriptional control of the tetO/promoter. Human melanoma cells were transduced by two modified retroviral tet vectors containing the transactivator regulatory unit and the IL-2 gene driven by the tetO/promoter, respectively. In the absence of tet, IL-2 expression in the target cells was stable over several months. IL-2 production was in the range of 40 U/10(6) cells/24 hours. A fine tuning of IL-2 expression could be achieved by culturing the transduced cells with increasing doses of tet, whereby a concentration of 500 ng/mL tet in the culture medium abrogated IL-2 expression. Most importantly for clinical application, IL-2 expression by the transduced melanoma cells could also be regulated in vivo. When nu/nu mice were inoculated with the transduced tumor cells, they failed to develop tumors. Instead, the inhibition of IL-2 expression in the transduced tumor cells by oral administration of tet led to subcutaneous tumor growth; this growth rate was comparable with the growth rate of subcutaneously inoculated untransduced parental cells. The finding demonstrates the applicability of the tet-regulated system in cancer gene therapy.
Pitzer
C
C
Department of Tumor Progression and Immune Defense, German Cancer Research Center, Heidelberg.
Schindowski
K
K
Pomer
S
S
Wirth
T
T
Zöller
M
M
D016475:3T3 Cells; D000818:Animals; D004305:Dose-Response Relationship, Drug; D015316:Genetic Therapy / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D008545:Melanoma / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D008957:Models, Genetic; D009369:Neoplasms / Q000628:therapy*; D012190:Retroviridae / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013752:Tetracycline / Q000008:administration & dosage*; D013997:Time Factors; D014161:Transduction, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D007376:Interleukin-2; D008156:Luciferases; D013752:Tetracycline