Infusion-rate independent cellular adriamycin concentrations and cytotoxicity to human bone marrow clonogenic cells (CFU-GM)
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R Raijmakers1, P Speth, T de Witte
1Department of Internal Medicine, University Hospital, Nijmegen, The Netherlands.
Abstract:
The effect of adriamycin (ADM) infusion-rate on cellular ADM concentrations and on clonogenicity of human haematopoietic cells was studied in vivo and in vitro. In patients an ADM dose of 30 mg m-2 was administered as a bolus injection, or as a 4 h or a 24 h infusion. In vitro the effect of ADM on clonogenic cell growth was determined after exposure during 5 min, 2 h and 24 h of human bone marrow cells to increasing ADM concentrations. ADM showed rapid intracellular accumulation, to levels 100-fold the plasma concentration in vivo or the incubation medium concentration in the in vitro experiments. After a bolus injection or 5 min exposure only approximately 10% of the cellular peak ADM was retained after elimination of the drug from the plasma or the incubation medium. Ninety percent of the ADM was apparently 'loosely' bound. After 4 h and 24 h constant-rate infusions and also after 2 h and 24 h incubations in vitro, the cells accumulated ADM gradually, and the subsequent washing-out of the cellular ADM was substantially less, most of the ADM being 'tightly' bound. Despite these different patterns of uptake and retention after in vivo short- and long-lasting infusion of the same total dose, the 'tightly-bound' cellular ADM concentrations were the same. Moreover, comparable cellular ADM concentrations, retained after efflux of the 'loosely-bound' cellular ADM fraction were equally cytotoxic to normal human clonogenic cells. Short-lasting cellular peak ADM concentrations which occur after a bolus injection or after short exposure to high ADM concentrations are not essential for the cytotoxic effect, in contrast to the retained, 'tightly-bound' cellular ADM levels.
Insights
Adriamycin (ADM) infusion rate impacts cellular drug levels and human hematopoietic cell clonogenicity. Tightly-bound ADM, not peak concentrations, is crucial for cytotoxic effects on normal cells.
Area of Science:
- Pharmacology
- Cell Biology
- Oncology
Background:
- Adriamycin (ADM) is a key chemotherapy agent.
- Understanding ADM's cellular uptake and retention is vital for optimizing treatment.
- Infusion rates can significantly alter drug pharmacokinetics and pharmacodynamics.
Purpose of the Study:
- To investigate the effect of ADM infusion rate on cellular ADM concentrations.
- To determine the impact of ADM infusion rate on the clonogenicity of human hematopoietic cells.
- To elucidate the relationship between ADM cellular binding (loosely vs. tightly bound) and cytotoxicity.
Main Methods:
- Administered ADM (30 mg m-2) via bolus, 4-hour, or 24-hour infusion in patients.
- Exposed human bone marrow cells to varying ADM concentrations for 5 minutes, 2 hours, and 24 hours in vitro.
- Measured intracellular ADM concentrations and assessed clonogenic cell growth.
Main Results:
- ADM rapidly accumulated intracellularly, reaching levels 100-fold higher than plasma or medium concentrations.
- Short exposure (bolus/5 min) resulted in ~10% 'loosely' bound ADM retained; long exposure (infusions/2-24h) led to gradual accumulation and substantial 'tightly' bound ADM.
- Despite different uptake/retention patterns, 'tightly-bound' cellular ADM concentrations were similar across infusion durations.
- Retained 'tightly-bound' ADM fractions demonstrated comparable cytotoxicity to normal human clonogenic cells.
Conclusions:
- The rate of ADM infusion influences cellular drug accumulation and binding.
- Cytotoxicity is primarily mediated by retained, 'tightly-bound' intracellular ADM, not transient peak concentrations.
- Optimizing ADM infusion strategies may enhance therapeutic efficacy by maximizing tightly-bound drug levels.