Journal
BIOCHEMICAL PHARMACOLOGY
Volume 66, Issue 7, Pages 1207-1218Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0006-2952(03)00467-2
Keywords
multidrug resistance; acid-base; weak acid; weak base; chemotherapy
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Funding
- NCI NIH HHS [R01 CA77575] Funding Source: Medline
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Resistance to anti-cancer chemotherapies often leads to regional failure, and can be caused by biochemical and/or physiological mechanisms. Biochemical mechanisms include the overexpression of resistance-conferring proteins. In contrast, physiological resistance involves the tumor microenvironment, and can be caused by poor perfusion, hypoxia and/or acidity. This communication investigates the role of tumor acidity in resistance to a panel of chemotherapeutic agents commonly used against breast cancer, such as anthracyclines, taxanes, anti-metabolites and alkylating agents. The effects of pH on the cytotoxicity of these agents were determined, and ion trapping was confirmed by monitoring the effect of pH on the cellular uptake of radiolabeled anthracyclines. Furthermore, pH-dependent cytotoxicity and uptake were compared between parental drug sensitive MCF-7 cells and variants overexpressing p-glycoprotein (MDR-1) and Breast Cancer Resistance Protein. These data indicate that the magnitude of physiological resistance from pH-dependent ion trapping is comparable to biochemical resistance caused by overexpression of drug efflux pumps. Hence, microenvironment-based ion trapping is a significant barrier to anthracycline-based chemotherapy and can itself be a therapeutic target to enhance the efficacy of existing chemotherapies. (C) 2003 Elsevier Inc. All rights reserved.
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