Seeking Cancer Cures On Ocean Floor

Scientists plunging to deep corners of the ocean are finding rare sponges that they hope, against astronomical odds, could lead them to a cure for cancer or other diseases.

Researchers at Harbor Branch Oceanographic Institution pull hundreds of new specimens from the sea every year, hoping at least one of them will be tougher than the cancer cells they carefully grow in a laboratory.

The team journeys to polluted and pristine waters throughout the year to collect sea life from a submarine with mechanical claws and arms, pulling in bunches of orange, yellow and brown sponges that have developed their own systems of self-protection. Most of the sponges have never been seen before.

"Nature can crank these things out, but to make them in a laboratory would be very difficult," said Amy Wright, division director at Harbor Branch.

The National Cancer Institute estimates that about 65 percent of all cancer drugs come from marine life and plants - their bark, roots, leaves and fruits. One of the more widely used anticancer drugs, Taxol, comes from the bark of Pacific yew trees.

But it usually takes thousands of tests to find one promising lead.

In 18 years of studies, only one sponge discovered by Harbor Branch has been promising enough to lure a pharmaceutical company's interest. A compound within the sponge, called Discodermalide, has stopped cancer cells from reproducing in early tests. In 1990, the institution secured a patent for the compound, hailed as its most important discovery.

Harbor Branch focuses on marine sponges because they are stationary and develop toxic chemicals to ward off predators, Wright said. The hope is that the chemicals within the sponges will kill cancer cells without hurting healthy human cells.

The research institution is one of about a half-dozen looking to marine life for cancer cures, and it specializes in deep-water discoveries. To accomplish dives of up to 3,000 feet, Harbor Branch built three submersibles that are launched from its research vessels.

One of the vessels, named after the institution's founder, Seward Johnson, is 204 feet long and can travel any of the world's oceans. The research vessels take crews of up to 40 people, including 15 scientists, into the Atlantic Ocean, Caribbean and Gulf of Mexico several times throughout the year.

Teams of researchers typically stay out to sea for two to three weeks, using a submersible each day to search for rare sponges.

The group looks for anything out of the ordinary. The scientist who discovered the sponge that yielded Discodermalide found it in surprisingly shallow waters about 500 feet deep during a scuba dive in the Caribbean.

The nonprofit institution operates under two five-year grants from the National Institutes of Health worth a total of $750,000 a year, along with five smaller grants from the National Science Foundation that pay about $160,000 annually.

During the scientists' research cruises, samples collected from the submersibles are put in a large freezer on the research vessel.

Once they return to Harbor Branch, researchers grind up small pieces of the specimens with ethyl alcohol. They then pour the mixture through a filter into test tubes, producing extracts as brightly colored as the sponges they collect.

The extracts are dropped into vials containing laboratory-grown cancer cells. If the extract kills 50 percent or more of the cancer cells, it undergoes more testing, but the vast majority don't continue to yield encouraging results.

"Those cancer cells can tolerate a lot. They're tough," said research specialist Pat Linley. Linley grows lung cancer, pancreatic cancer and breast cancer cells in the lab and would be the first to see whether a new discovery could hold as much promise as Discodermalide.

Swiss pharmaceutical giant Novartis Pharma is working to develop a drug from the compound. Tests show that in lower concentrations, the compound is at least as effective as the widely used anticancer drug Taxol, Wright said.

"It's like a funnel where you feed in lots of materials and you end up with very few winners," said Gordon Cragg, chief of the natural products branch at the National Cancer Institute. "But of course the ultimate reward is when you do end up with something good."

He said between 1960 and 1982, the National Cancer Institute collected 35,000 plant samples and made 114,000 extracts to test against cancer. Only two of those extracts produced "interesting" leads, Cragg said.

Developing anticancer drugs is particularly difficult because cancer cells are so similar to human cells, and it's hard to kill one and not the other, Cragg said. Current chemotherapy drugs kill cancer cells but also aren't selective enough, which is why they can cause nausea, vomiting and hair loss.

"But there are slight differences and what you have to try to take advantage of are those small differences," Cragg said. "The big hope is you can kill off the cancer cells without hurting the patient too much."

By Jill Barton