The Southern Sea's Medical Wonder: Viva Palmerolide!

Photos from UAB in Antarctica group on Flickr, related to this post
By Jim McClintock
Posted on 04/01/07
While our research program here in Antarctica focuses primarily on aspects of the ecology of the marine bottom-dwelling seaweeds and invertebrates, we are pleased that there are broader impacts of our work that have societal implications. Not least of these is the possibility that some of the compounds we discover in the course of our chemical ecological studies also have the potential to ultimately fight cancer, AIDS, cystic fibrosis, microbial infections, and other often devastating human diseases.

The world’s oceans represent a cornucopia of potential human drugs for a number of reasons. First off, about 2/3 of the drugs we take for granted today (e.g., penicillin, aspirin, taxol, etc.) come from natural products (compounds made by organisms for ecological rather than metabolic purposes) discovered in terrestrial microbes and plants. This historical focus on land-based organisms is primarily because of the ease of their harvest and near proximity. However, the recent advent of modern oceanographic and diving technology has greatly enhanced our ability to search for natural products from marine organisms.

Another reason the ocean’s are particularly promising sources for new drugs is that life on our planet evolved in and from the sea. As such, marine organisms have had many additional millennia to evolve unique defensive metabolites. Moreover, documented levels of species diversity in the world’s oceans are fantastically high, with many more species certainly awaiting discovery. For all these reasons, it is not particularly surprising that there are currently a number of drugs from marine organisms from tropical and temperate environments currently under clinical study.

But what about the marine organisms that occupy the world’s polar seas such as here where we are working in Antarctica?  Are these “inhospitable” cold regions of the globe also worthy of the “search for a cure”?

Early marine natural products chemists, and some even today, believe that the search for marine natural products is best suited to warmer seas. This is likely related to a preconceived notion that polar seas are lacking in species diversity, and that predators that would select for chemical defenses, or nearby neighbors that would compete chemically for space, are few and far between. These premises have turned out to be false, at least here in Antarctica.

Recent studies of the taxonomic diversity of the marine invertebrates living in the seas surrounding Antarctica have revealed remarkably high numbers of species. Moreover, here on the Antarctic Peninsula the numbers of marine seaweeds number over 100 species, and even more importantly, many dominate ecologically.

While fish predators that graze on seaweeds, sponges, soft corals and other plant-life are indeed rare, there are many species of sea stars that predate immobile invertebrates, and as you have learned from earlier blogs written by Maggie and Chuck, a myriad of amphipods (little shrimp-like organisms) that are potential consumers of seaweeds, and perhaps also sponges and sea squirts (tunicates).

So has our ecological research in Antarctica yielded any promising compounds for drug development?  Happily, we can report that several years ago we discovered a suite of novel chemicals in an Antarctic sea squirt that are very potent against several forms of melanoma. We have named these compounds “palmerolides” in recognition of their being discovered here in the waters surrounding Palmer Station.

The National Cancer Institute, which first noted the potent anti-cancer activity of our palmerolides, has now conducted promising cancer research using mouse models. Moreover, several drug companies have displayed strong interest in the possibility of taking the palmerolides to the drug testing stage, and one company is currently undertaking such studies. As with almost all natural products discovered in organisms, should palmerolide become a cancer drug, it can be synthesized in the laboratory and thus sea squirts that harbor these compounds would not need to be harvested from the ocean.

Wouldn’t it be exciting if the basic marine ecological research supported by the National Science Foundation’s Office of Polar Programs and our home institutions, UAB and USF, bore this fruit of a considerably “broader impact” on human society?! 

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