The marine ecosystem is an enormously rich source of natural products with potential therapeutic usefulness in oncology. Over the past few years, >2000 new compounds from various marine sources have been described and characterized. The significant expansion of this field is due to improvements in the technologies involved in sample collection, the closer collaboration among scientists from a variety of disciplines worldwide and the support of governmental institutions as well as pharmaceutical companies. Some of these compounds have been tested in clinical trials and are in advanced stages of development, while others are still in preclinical stages. These agents are characterized as having unique mechanisms of action and pharmacological properties. They represent potential candidates for the treatment of malignant disease, either to be used as single agents, or as part of a combination regimen. More recently, the focus of attention has shifted towards microscopic organisms. Microorganisms are abundant in the marine ecosystem and biologically rich. In fact, it is believed that a number of metabolites obtained from some macroorganisms may be produced by their associated microorganisms. In addition, microorganisms can be adapted to artificial culture conditions thus avoiding problems of collection and supply.
In summary, the marine world has become an important source of anticancer agents with novel mechanisms of action. The continuation of preclinical and clinical studies is required in order to assess the exact role of this new class of compound in the treatment of patients with cancer. It is anticipated that marine-derived anticancer drugs will represent valuable tools in the oncological armamentarium.