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Tissue transport of anti-cancer drugs
1Department of Medical Oncology, VU medical center, and Tumor Cell Biology Group, VU, Amsterdam, the Netherlands. j.lankelma@vumc.nl
Abstract:
Blood-borne drug molecules are transported through as well as around cells in tissue. For small molecule drugs with a molar weight <1000, the wall of the capillary blood vessels in tumors usually is not a barrier. Just after a rise in the drug concentration in the blood, the cells closest to the microvessels are exposed to the highest drug concentrations. Short or long lasting concentration gradients away from the capillary vessels will develop. Since in a tumor the distance to the nearest blood vessel can be relatively large, inefficient transport of drugs to some cancer cells may limit drug efficacy. Studies on in vitro drug gradients have given insight into the factors determining this transport. Small intercellular distances, high cellular drug influx and low drug efflux rates, and high intracellular and extracellular drug binding favor the development of drug gradients. In the absence of drug metabolism, gradients "level out" over time and may reverse as the blood concentration drops. Understanding the drug transport process from the microvessels to every cancer cell will be important for optimizing cancer chemotherapy. Cancer cells that can "hide" for the drug may lead to regrowth of the tumor.
Insights
Drug transport to cancer cells is key for effective chemotherapy. Understanding how drugs move through tumors helps improve treatment and prevent cancer regrowth.
Area of Science:
- Pharmacology
- Oncology
- Biomedical Engineering
Background:
- Blood-borne drug molecules travel through and around tissue cells.
- Tumor capillary walls are generally not a barrier for small molecule drugs (<1000 Molar Weight).
- Drug concentration gradients form in tumors, with cells nearest blood vessels receiving the highest doses.
Purpose of the Study:
- To investigate the factors influencing drug transport and gradient formation within tumor tissues.
- To understand how inefficient drug delivery to cancer cells impacts chemotherapy efficacy.
- To identify mechanisms by which cancer cells may evade drug exposure, potentially leading to tumor regrowth.
Main Methods:
- Analysis of in vitro drug gradient studies.
- Evaluation of factors affecting drug transport, including intercellular distances, cellular influx/efflux rates, and drug binding.
- Modeling of drug concentration changes over time in relation to blood concentration.
Main Results:
- Small intercellular distances, high cellular drug influx, low efflux, and high intracellular/extracellular binding favor drug gradient development.
- In the absence of drug metabolism, gradients diminish over time and can reverse as blood concentration decreases.
- Inefficient drug transport to distant cancer cells can limit overall treatment effectiveness.
Conclusions:
- Optimizing chemotherapy requires a thorough understanding of drug transport dynamics from microvessels to all cancer cells.
- Identifying cancer cells that can avoid drug exposure is crucial for preventing tumor recurrence.
- Targeting drug delivery mechanisms can enhance chemotherapy outcomes and combat treatment resistance.