Mechanisms of P-Glycoprotein Alteration During Anticancer Treatment: Role in the Pharmacokinetic and Pharmacological Effects of Various Substrate Drugs

Abstract

Abstract. In clinical pharmacotherapy, therapeutic benefits and adverse effects of medicines differ substantially between individuals and are often determined by their blood levels. Critical regulators influencing the pharmacokinetics and pharmacodynamics of drugs include drug transporters and drug-metabolizing enzymes. Among these, we have focused on P-glycoprotein (P-gp), a drug efflux transporter. A growing body of evidence indicates that the expression and functional activity of P-gp are altered under several pathological conditions, by exposure to substrate drugs of P-gp, and by ingestion of certain foods. In this critical review, we discuss the mechanisms by which anticancer drugs, most of which are P-gp substrates, alter the expression and functional activity of P-gp in tumors and normal tissues after chronic treatment. Accumulating evidence shows that various transcription factors, in addition to epigenetic and post-translational factors, modulate P-gp expression, which alters the pharmacokinetics and pharmacological effects of drugs. Therefore, it is important to consider individual patients with regard to drug-taking history, as well as levels of P-gp expression and function, when providing clinical pharmacotherapy.Keywords: P-glycoprotein, anticancer drug, drug-drug interaction, opioid, cancer *Corresponding author. stoku@pharm.Kobegakuin.ac.jp Published online in J-STAGE on July 2, 2014 doi: 10.1254/jphs.14R01CRInvited article 243 Changes in P-gp by Anticancer Treatment targeted anticancer drugs acting on specific genes or their products has grown rapidly. In fact, combination treatment with molecularly targeted drugs and cytotoxic chemotherapy against cancers such as acute leukemia or lymphatic malignancy improved therapeutic outcome in comparison to conventional anticancer chemotherapy (8, 9). However, solid tumors often have greater inherent resistance and are less sensitive to anticancer drugs (10). Furthermore, chronic exposure to anticancer drugs frequently leads to multi-drug resistance where the therapeutic effects of these drugs on tumors is largely reduced (11). The development of resistance to anticancer chemotherapy remains one of the major obstacles in effective pharmacological therapy for cancer using current treatment strategies (12).Research revealing the role of drug transporters in cancer began with the discovery of P-glycoprotein (P-gp). In 1976, during research to elucidate the mechanism by which cancer cell lines acquire multi-drug resistance, Juliano et al. discovered that P-gp is over-expressed on the surface membranes of multi-drug resistant cancer cells (13). Subsequent studies have demonstrated that P-gp is present in cancer tissue (11,14), as well as in normal tissues such as small intestine, where it regulates drug absorption, and liver and kidney, where it modulates drug clearance (15). These results suggest that P-gp determines blood levels of its substrate drugs. Furthermore, P-gp is now considered to be an extremely important factor in the pharmacokinetics of drugs bec...

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