Solute carrier transporters as targets for drug delivery and pharmacological intervention for chemotherapy.

Many solute carrier transporters that interact with anticancer agents and contribute to their pharmacokinetics have been shown to be differentially upregulated in cancer cells as a result of adaptive response to altered nutritional requirements. This review focuses on pathophysiological function of membrane transporters responsible for the influx of physiological substances including oligopeptides, amino acids, and organic cations and anions, and summarizes the recent knowledge regarding mechanisms in their gene expressions. Broad substrate specificity of enhanced oligopeptide H(+) /peptide cotransporter 1 activity in cancer cells is useful for tumor tissue-specific delivery of chemotherapeutic agents and positron emission tomography diagnostic probes. Amino acid transporters such as LAT1 and ASCT2 are upregulated in human cancer cells and are thought to stimulate tumor growth by regulating mammalian target of rapamycin through nutrient pathway. Especially, LAT1 could be a molecular target to deprive cancer cells of amino acids in combination with aminopeptidase inhibitors. As organic anion transporting polypeptides carry estrone-3-sulfate that is intracellularly hydrolyzed to estrone, their overexpression may provide a pharmacological merit to treat hormone-responsive breast tumors. Therefore, it is important to understand the pathophysiological significance and gene expression in cancer to develop new rationales for drug delivery and pharmacological interventions for chemotherapy.