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Intratumoral differences in methotrexate levels within human osteosarcoma xenografts studied by microdialysis
P O Ekstrøm1, K E Giercksky, A Andersen
1Department of Surgical Oncology, Norwegian Radium Hospital, Oslo, Norway. p.o.ekstrom@klinmed.uio.no
Abstract:
A central tenet in oncology is the assumed relationship between drug concentration and cytotoxicity. Determinations of drug levels in tumor tissues are, however, generally not undertaken. Microdialysis is a method where continuous drug monitoring may be achieved by sampling of low molecular weight substances from the extracellular space. By employing this technique it is possible to observe variable drug levels within tissues, including tumors, over time. Herein, we present results from a nude rat model where subcutaneous human osteosarcoma xenografts were established prior to the administration of the antifolate methotrexate as an intravenous infusion. Significant differences in drug exposure within single tumors were evident. Generally, peak drug concentrations were lower and drug efflux slower from the center of the tumors as compared to the periphery. The use of microdialysis could be an important tool for optimizing current strategies in anticancer chemotherapy.
Insights
Microdialysis reveals varied anticancer drug levels within tumors. This technique shows lower drug concentrations and slower drug removal from tumor centers, aiding chemotherapy optimization.
Area of Science:
- Oncology
- Pharmacokinetics
- Biomedical Engineering
Background:
- The relationship between drug concentration and cancer cell killing is crucial but often unmeasured in tumors.
- Current methods do not routinely assess drug levels within tumor tissues.
- Understanding intratumoral drug distribution is key for effective chemotherapy.
Purpose of the Study:
- To investigate the utility of microdialysis for monitoring anticancer drug concentrations within tumor tissues.
- To assess the variability of drug exposure over time and space within tumors.
- To evaluate the drug distribution of methotrexate in a human osteosarcoma xenograft model.
Main Methods:
- Utilized microdialysis for continuous monitoring of low molecular weight substances in the extracellular space.
- Established subcutaneous human osteosarcoma xenografts in a nude rat model.
- Administered methotrexate intravenously and measured drug levels via microdialysis probes placed in tumor centers and peripheries.
Main Results:
- Demonstrated significant variability in drug exposure within individual tumors.
- Observed lower peak drug concentrations in the center compared to the periphery of tumors.
- Found slower drug efflux from the tumor center than from the periphery.
Conclusions:
- Microdialysis enables real-time monitoring of intratumoral drug concentrations.
- Drug distribution within tumors is heterogeneous, with lower exposure in central regions.
- Microdialysis is a valuable tool for optimizing anticancer drug delivery and chemotherapy strategies.