Compunds are being mass produced and genetically engineered in laboratories.

Digging deep: Sea squirts, which live on the ocean floor, harbor chemicals toxic to cancer cells.

An expedition to the Republic of Palau in Micronesia has led to the discovery that microbes inside a bright green creature that lives in tropical oceans produce peptides that can kill cancer cells.

Oceans are thought to be home to a treasure trove of chemicals that could be developed into drugs to treat debilitating illnesses such as cancer, chronic pain and arthritis.

The sea squirt Lissoclinum patella is a tunicate—meaning that it has a thick secreted covering like a tunic—that clings to rocks, piers and boats, and lives on the bottom of the sea. Scientists had previously found that ground-up extracts of these sea squirts have antitumor activity. University of Utah researchers have now discovered that the squirts are home to Prochloron didemni, a symbiotic bacteria that produce patellamides, small cyclic peptides consisting of eight amino acids that are toxic to human cancer cell lines.

In collaboration with researchers from The Institute for Genomic Research in Maryland, the scientists cloned the genes for patellamides and expressed them in Escherichia coli (Proc. Natl. Acad.Sci. USA 102, 7051–7052; 2005).The method allows for a renewable supply of the compound, and for engineering more effective genetic variants.

You could potentially have all the compounds you need generated in culture in your lab. , Eric Schmidt, University of Utah

“You don't have to take animals off relatively fragile coral reefs because you could potentially have all the compounds you need generated in culture in your lab,” says lead investigator Eric Schmidt. He says he will continue his quest worldwide, including the Red Sea in Egypt and Papua New Guinea.

The finding is proof that marine organisms can be harnessed for drug discovery, says Tadeusz Molinski, professor of chemistry at the University of California, Davis. “It may also be the turning point in commercializing the potential of marine natural products.”

Marine organisms may make some of these chemicals to protect themselves from predators and ward off other organisms. “In other cases, it may be a total coincidence that, say, a peptide that is used by a marine snail for hunting prey also can be used to kill pain in human patients,” Molinski says.

According to a Natural Resources Defense Council report in March, more than 28 marine products are being tested in clinical trials, and many more are in preclinical development.

Most research has focused on creatures that dwell in shallow and tropical ocean water, but attention is increasingly being focused on the deep sea, where organisms have adapted over thousands of years to survive in cold, dark and highly pressurized places. “Three-quarters of the world is covered by oceans,” Molinksi says. “We've only dipped below the surface.”