Coral reefs, forests, and thermal vents: the worldwide exploration of nature for novel antitumor agents.

Nature has been a source of medicinal treatments for thousands of years, and plant-based systems continue to play an essential role in the primary health care of 80% of the world's population. Nature has provided many of the effective anticancer agents in current use, such as the microbially derived drugs, dactinomycin, bleomycin, and doxorubicin, and the plant-derived drugs vinblastine, irinotecan, topotecan, etoposide, and paclitaxel. The search for novel antitumor agents from natural sources continues with botanists, marine biologists, and microbiologists teaming up with chemists, pharmacologists, toxicologists, and clinicians in the investigation of coral reefs, rainforests, and deep subsurface thermal vents for novel bioactive compounds. The wealth of anticancer drugs of natural origin and critical aspects of the ongoing discovery and development process are discussed.