Metals and metastasis: Exploiting the role of metals in cancer metastasis to develop novel anti-metastatic agents

Metastasis is currently the leading cause of cancer related death and is the most feared and difficult to treat outcome for cancer patients. This complex process is regulated by a plethora of signaling pathways and molecules that control cell proliferation, invasion, motility and adhesion. Many of these vital processes that enable metastasis to occur are influenced by metals, which play crucial roles in the function of numerous proteins and enzymes. Importantly, an excess of essential metals such as iron and copper is often associated with carcinogenesis and metastatic disease. As such, metals have emerged as promising and viable therapeutic targets for a new generation of anti-cancer and anti-metastatic agents. Further, the unique properties of metals, including their abilities to redox cycle or to mimic other metals, can also be utilized to more effectively target aggressive and metastatic cancer cells. This review will provide an overview of the role that metals play in the metastatic progression of cancer and the development of novel therapies that either target or utilize metal ions as part of their mechanism of action to inhibit metastasis.