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Penetration of anticancer drugs through solid tissue: a factor that limits the effectiveness of chemotherapy for
J K Tunggal1, D S Cowan, H Shaikh
1Division of Experimental Therapeutics, Ontario Cancer Institute, University of Toronto, Canada.
Abstract:
Penetration of anticancer agents to cells distant from the vascular system is required for efficacy of cancer chemotherapy against solid tumors. Many solid tumors have a poorly formed blood vascular system with variable rates of blood flow and much larger intercapillary distances than those found in normal tissues. The requirement for drugs to penetrate several layers of tissue might pose a barrier to the effective treatment of solid tumors. Multicellular layers (approximately 200 microm thick) were grown in vitro on Teflon membranes from EMT6 murine and MCF7 human tumors and have been used to quantitate the penetration of four widely used anticancer drugs through solid tissue. The penetration of doxorubicin and mitoxantrone was limited and very slow (<10% of the rate of penetration through the Teflon membrane alone). The penetration of methotrexate and 5-FU was more rapid (approximately 30-50% of the rate of penetration through the Teflon membrane alone), but remains a substantial barrier to the effectiveness of these drugs. Strategies to improve the penetration of anticancer drugs through poorly vascularized tumor tissue have considerable potential to improve the outcome of chemotherapy for solid tumors.
Insights
Chemotherapy drugs struggle to reach solid tumors due to poor blood vessel networks. Improving drug penetration is key to enhancing cancer treatment effectiveness.
Area of Science:
- Oncology
- Pharmacology
- Biomedical Engineering
Background:
- Effective cancer chemotherapy for solid tumors requires anticancer agents to penetrate tissue distant from the vascular system.
- Solid tumors often exhibit poorly developed vasculature, characterized by variable blood flow and increased intercapillary distances compared to normal tissues.
- Drug penetration through multiple tissue layers presents a significant challenge to successful solid tumor treatment.
Purpose of the Study:
- To quantify the penetration of four common anticancer drugs through in vitro multicellular tumor models.
- To assess the impact of tumor tissue structure on drug diffusion and efficacy.
Main Methods:
- Multicellular layers (approx. 200 micrometers thick) were cultured in vitro from EMT6 murine and MCF7 human tumor cell lines on Teflon membranes.
- The penetration rates of doxorubicin, mitoxantrone, methotrexate, and 5-fluorouracil (5-FU) were measured through these tumor tissue models and compared to penetration through the Teflon membrane alone.
Main Results:
- Doxorubicin and mitoxantrone exhibited limited and very slow penetration (<10% of control).
- Methotrexate and 5-FU showed more rapid penetration (30-50% of control), but still represented a substantial barrier.
- Drug penetration was significantly hindered by the simulated solid tumor tissue structure.
Conclusions:
- The diffusion of several key anticancer drugs is substantially impaired by the physical barriers within solid tumor tissues.
- Strategies aimed at enhancing drug penetration through poorly vascularized tumor environments hold significant promise for improving chemotherapy outcomes.
- Further research into drug delivery systems and therapeutic approaches that overcome tumor penetration limitations is warranted.