Differences in substrate specificity among glutathione conjugates (GS-X) pump family members: comparison between multidrug resistance-associated protein and a novel transporter expressed on a cisplatin-resistant cell line (KCP-4)

Metal- and metalloid-based compounds to target and reverse cancer multidrug resistance

Drug resistance remains the major cause of cancer treatment failure especially at the late stage of the disease. However, based on their versatile chemistry, metal and metalloid compounds offer the possibility to design fine-tuned drugs to circumvent and even specifically target drug-resistant cancer cells. Based on the paramount importance of platinum drugs in the clinics, two main areas of drug resistance reversal strategies exist: overcoming resistance to platinum drugs as well as multidrug resistance based on ABC efflux pumps. The current review provides an overview of both aspects of drug design and discusses the open questions in the field. The areas of drug resistance covered in this article involve: 1) Altered expression of proteins involved in metal uptake, efflux or intracellular distribution, 2) Enhanced drug efflux via ABC transporters, 3) Altered metabolism in drug-resistant cancer cells, 4) Altered thiol or redox homeostasis, 5) Altered DNA damage recognition and enhanced DNA damage repair, 6) Impaired induction of apoptosis and 7) Altered interaction with the immune system. This review represents the first collection of metal (including platinum, ruthenium, iridium, gold, and copper) and metalloid drugs (e.g. arsenic and selenium) which demonstrated drug resistance reversal activity. A special focus is on compounds characterized by collateral sensitivity of ABC transporter-overexpressing cancer cells. Through this approach, we wish to draw the attention to open research questions in the field. Future investigations are warranted to obtain more insights into the mechanisms of action of the most potent compounds which target specific modalities of drug resistance.

Cisplatin nephrotoxicity: molecular mechanisms

Cisplatin is one of the most widely used chemotherapeutic agents for the treatment of several human malignancies. The efficacy of cisplatin is dose dependent, but the significant risk of nephrotoxicity frequently hinders the use of higher doses to maximize its antineoplastic effects. Several advances in our understanding of the biochemical and molecular mechanisms underlying cisplatin nephrotoxicity have recently emerged, and are reviewed in this article. Evidence is presented for distinct mechanisms of cisplatin toxicity in actively dividing tumor cells versus the normally quiescent renal proximal tubular epithelial cells. The unexpected role of gamma-glutamyl transpeptidase in cisplatin nephrotoxicity is elucidated. Recent studies demonstrating the ability of proximal tubular cells to metabolize cisplatin to a nephrotoxin are reviewed. The evidence for apoptosis as a major mechanism underlying cisplatin-induced renal cell injury is presented, along with the data exploring the role of specific intracellular pathways that may mediate the programmed cell death. The information gleaned from this review may provide critical clues to novel therapeutic interventions aimed at minimizing cisplatin-induced nephrotoxicity while enhancing its antineoplastic efficacy.