Bacterial toxins produced by tiny marine organisms collected in Antarctica could become an effective treatment for melanoma, the deadliest form of skin cancer, according to researchers at the University of South Florida (USF).
Expedition Yields Promising Samples
A team from USF recently returned from a six-week expedition to one of the world's remotest regions, collecting samples of ascidians, invertebrates known as sea squirts that thrive in icy waters. Divers descended to depths of up to 130 feet for about half an hour at a time to gather the organisms.
Brian Baker, professor of chemistry at USF, explained that the toxins produced by ascidians as protection against predators can be repurposed. Research already undertaken has shown the toxins killed melanoma cells in mice.
"The good news is it didn't kill the mice," Baker said. "It did kill their cancer, so we know it has the physiological properties to act like a drug. We need grams of material to do a bigger study in mice, perhaps go into other animal models, and if we can prove the safety, we can actually start some human trials."
Challenges in the Antarctic
Ben Meister, a USF professor and diving safety officer for the expedition funded by the National Science Foundation, said sea temperatures were only one of the challenges. "In Antarctica, you're dealing with ice, leopard seals, changing seas and sometimes very limited visibility," he said. "Every dive must be carefully planned to balance getting the work done while keeping everyone safe."
Baker acknowledged the pathway to producing a safe and effective anti-melanoma drug is long, requiring a succession of strictly regulated trials. However, knowledge gained from the expedition could significantly advance the timeline.
Laboratory Work Ahead
Work on developing the toxins towards a potential melanoma-fighting drug will now take place in laboratories, with some already under way in partnerships with the Desert Research Institute and the Scripps Institution of Oceanography. The new knowledge from this year's expedition has advanced understanding of how the melanoma-killing bacterium lives inside the microorganism and the ecological relationship between them.
"Things we learn from these field studies are going to help us to advance this thing when we start doing those animal models, and human models, and taking it forward we will have a much better idea of the things we can do and things we shouldn't do in terms of using it as a drug," Baker said.
The researchers returned exhausted but excited about the laboratory stage, which will include trying to synthetically reproduce the toxin. "You need hundreds of milligrams to grams of this metabolite, and from a basketball size collection of ascidians we might get one-thousandth of that," Baker said. "Obviously we cannot collect 1,000 basketball quantities from the Antarctic, that would destroy the ecology, so one of the things we have to do is figure out how to make this stuff in the lab."
Broader Implications
Baker started his career in marine biology and chemistry in 1990 and has worked on many projects evaluating undersea organisms for possible use in healthcare. "More than half of Food and Drug Administration-approved drugs originate from natural sources," he said. "I can tell you about any number of other metabolites that we found in sponges, corals, tunicates and things, and not just from Antarctica."
He called the melanoma discovery "sort of a career pinnacle." "Killing cancer cells in a petri dish is one thing, but going beyond that is much harder, and the fact that we've cleared some of those higher hurdles is really exciting for me," he said. "Now we've got to make the next hurdle."
