[Frontiers in Bioscience S4, 375-391, January 1, 2012]

New applications of old metal-binding drugs in the treatment of human cancer

Sara M. Schmitt1, Michael Frezza1, Qing Ping Dou1

1The Developmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute, and Departments of Oncology, Pharmacology and Pathology, School of Medicine, Wayne State University, Detroit, Michigan 48201, USA

TABLE OF CONTENTS

1. Abstract
2. Introduction
2.1. The use of metal complexes for cancer treatment
2.2. Ruthenium-based complexes as potential anticancer agents
3. Importance of metals in the growth and progression of cancer
3.1. Copper
3.2. Zinc
4. Ubiquitin-proteasome pathway
5. Dithiocarbamates
5.1. Gold Dithiocarbamates
5.2. Copper and zinc-containing dithiocarbamates
5.2.1. Disulfiram, EtDTC, and PyDTC
5.2.2. Synthetic EtDTC copper and zinc complexes
5.2.3. Synthetic PyDTC copper and zinc complexes
6. Hydroxyquinolines
6.1. Clioquinol
6.2. 8-Hydroxyquinoline analogs
7. Conclusions
8. Acknowledgements
9. References

1. ABSTRACT

Significant advances in the use of metal complexes, precipitated by platinum, have fostered a renewed interest in harnessing their rich potential in the treatment of cancer. In addition to platinum-based complexes, the anticancer properties of other metals such as ruthenium have been realized, and ruthenium-based compounds are currently being investigated in clinical trials. Since the process of drug development can be expensive and cumbersome, finding new applications of existing drugs may provide effective means to expedite the regulatory process in bringing new drugs to the clinical setting. Encouraging findings from laboratory studies reveal significant anticancer activity from different classes of metal-chelating compounds, such as disulfiram, clioquinol, and dithiocarbamate derivatives that are currently approved for the treatment of various pathological disorders. Their use as coordination complexes with metals such as copper, zinc, and gold that target the ubiquitin-proteasome pathway have shown significant promise as potential anticancer agents. This review discusses the unique role of several selected metals in relation to their anti-cancer properties as well as the new therapeutic potential of several previously approved metal-chelating drugs. In vitro and in vivo experimental evidence along with mechanisms of action (e.g., via targeting the tumor proteasome) will also be discussed with anticipation of strengthening this exciting new concept.