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From laboratory expertise to clinical practice: multidrug-resistance-based gene therapy becomes available for
1Department of Urology, Erasmus University, Rotterdam, The Netherlands.
Abstract:
Many human tumors such as bladder carcinoma that are initially responsive to chemotherapy eventually fail to respond to treatment. For most drugs, dose escalation that may be required for a cure cannot be achieved because sensitive tissues such as bone marrow limit cytotoxic therapy. Approaches to prevent or circumvent myelosuppression are therefore a high priority of research on dose intensification protocols. One such strategy is to protect bone marrow cells by virtue of expression of the multidrug-resistance (MDR1) gene encoding for P-glycoprotein. In our first set of experiments, we transplanted bone marrow cells derived from transgenic mice that constitutively express MDR1 to lethally irradiated recipients (n = 36). From 6 weeks to 10 months after the transplant, all animals contained MDR1 DNA in spleen and bone marrow specimens as indicated by Southern-blot analysis and expressed MDR1 RNA in bone marrow samples as detected by slot-blot analysis. In addition, these animals were resistant to the myelosuppressive effect of doxorubicin, daunomycin, taxol, vinblastine, vincristine, etoposide, and actinomycin D, whereas control animals that were reconstituted with normal bone marrow reacted with a significant decrease in their white blood counts. In a second set of experiments, we retrovirally transfected a construct consisting of a murine long-terminal repeat (LTR) promoter and the human MDR1 gene into CD34-positive bone marrow stem cells from rhesus monkeys using the same technique as in the ongoing clinical ADA gene-therapy protocol. Upon transplantation, high-level and long-lasting expression of the human MDR1 gene was observed in recipient monkeys.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Mice engineered to express the multidrug-resistance (MDR1) gene in bone marrow cells showed resistance to chemotherapy-induced myelosuppression. This strategy protects against bone marrow damage, enabling higher chemotherapy doses for cancer treatment.
Area of Science:
- Biomedical Science
- Molecular Biology
- Cancer Research
Background:
- Chemotherapy resistance in human tumors like bladder carcinoma necessitates dose escalation for effective treatment.
- Myelosuppression, or bone marrow damage, limits the achievable doses of cytotoxic chemotherapy.
- Protecting bone marrow cells via multidrug-resistance (MDR1) gene expression is a key strategy for dose intensification protocols.
Purpose of the Study:
- To investigate the potential of MDR1 gene expression in bone marrow cells to circumvent chemotherapy-induced myelosuppression.
- To evaluate the efficacy of MDR1 gene transfer in protecting bone marrow from cytotoxic drug effects.
Main Methods:
- Transplantation of bone marrow cells from MDR1 transgenic mice into irradiated recipients.
- Southern-blot and slot-blot analyses to confirm MDR1 DNA and RNA expression in transplanted cells.
- Retroviral transfection of the human MDR1 gene into CD34-positive bone marrow stem cells from rhesus monkeys.
Main Results:
- MDR1 gene expression was confirmed in spleen and bone marrow of recipient mice for up to 10 months post-transplant.
- MDR1-expressing bone marrow cells conferred resistance to multiple chemotherapy drugs, including doxorubicin and taxol, unlike control groups.
- High-level, long-lasting expression of the human MDR1 gene was observed in recipient monkeys after stem cell transplantation.
Conclusions:
- Constitutive MDR1 expression in bone marrow cells provides significant protection against chemotherapy-induced myelosuppression in mice.
- Retroviral transfer of the MDR1 gene into primate bone marrow stem cells leads to sustained gene expression.
- This approach holds promise for protecting bone marrow and enabling dose-intensified chemotherapy in cancer treatment.