That humans depend upon the ocean for our existence is common knowledge. The ocean controls the planet’s climate, provides us with food, and generates oxygen. What isn’t as well known is the potential of the ocean as a medical resource. Many of the medicines that we use today are derived from natural terrestrial sources, including penicillin, perhaps the most important drug ever discovered. However, the biodiversity found on land pales in comparison with that found in the ocean — perhaps predictably, since the ocean accounts for 71 percent of the Earth’s surface. It is therefore likely that the ocean, much of which remains undiscovered today, harbors an incredible number of potentially life-saving compounds.
The healing properties of the sea have been recognized by many cultures, including the ancient Greeks, who examined the effects of seawater on human health. However, it is only recently that we have developed the technology to harness the healing power of the ocean in a more tangible sense. Although marine-medical prospecting remains a difficult and expensive endeavor, more research than ever before is now being conducted on the seafloor, as both scientists and corporations search for disease cures.
Thanks to the relative newness of marine-medical research, many of the potential cures derived from the ocean are still in the testing and development stages. In 2003, a research group led by William Fenical, the director of the Center for Marine Biotechnology and Biomedicine at Scripps Institution of Oceanography reported the discovery of a previously unknown strain of bacteria found in deep-ocean sediments. These bacteria are not only useful as powerful natural antibiotics, but may also prohibit the growth of cancer cells. The research group created a natural product known as Salinosporamide A from the ocean-sediment bacteria, which may someday be used as a cure for colon cancer, certain types of lung cancer, and most effectively of all, breast cancer. Early trials of the drug as it relates to a number of different cancers are ongoing.
Another marine substance thought to aid in the treatment of cancer is bryostatin, first isolated in the 1960s from a species of bryozoan, or sea moss, known as Bugula neritina. In in-vitro trials, bryostatin has proven effective when used in conjunction with other anti-cancer drugs against a large variety of tumor cells, including lung cancer, prostate cancer and non-Hodgkin’s lymphoma. In a recent issue of Current Alzheimer’s Research medical journal, a team of researchers from Louisiana State University’s Health Sciences Center published findings that suggest that bryostatin could also be useful as a memory-enhancing agent. The drug is thought to prevent the accumulation of toxic amyloid in the brain, therefore allowing a greater return of normal memory. Several other marine substances are currently undergoing clinical trials, including a Caribbean sponge species that may generate the compounds needed to create the anti-retroviral drug used to fight AIDS.
On the market
Despite the enormous potential for medical discovery, relatively few marine substances have so far been approved for clinical use. The process of gaining approval is time-consuming, expensive and legally complicated, and as such, medical trials can take many years. For commercial approval, a substance must be deemed both effective and safe, and from a logistical perspective, it must also be possible to manufacture the substance on a large scale.
The first marine-derived drug approved for use by the Food and Drug Administration (FDA) was Ara-C, or Cytarabine. Cytarabine owes its discovery to the Caribbean sponge Cryptothetya crypta, whose unusual nucleosides (a component of their DNA) inhibit the replication of genetic material. Researchers realized that this characteristic could be used to prevent tumor cells from dividing and replicating, and therefore used the sponge nucleosides to create a cytostatic drug that was the basis for the synthesis of Cytarabine. Today, Cytarabine features on the World Health Organizations’ List of Essential Medicines, and is used in chemotherapy treatment. It kills cancer cells by interfering with DNA synthesis, and is primarily used to treat acute myeloid leukemia, acute lymphocytic leukemia and non-Hodgkin’s lymphoma.
Another approved substance is the peptide Ziconotide, or Prialt. Derived from the venom of various cone snail species, Ziconotide modifies the toxins in this venom to treat chronic pain. Whereas cone snail venom naturally induces paralysis in its victims, Ziconotide blocks the nerves in the spinal cord that send pain signals to the brain. As a painkiller, it’s 1,000 times more powerful than morphine, and is used for patients whose pain is so severe that morphine is unable to provide relief. Alternatively, Ziconotide is also given to those patients that are allergic to morphine.
Other marine-derived substances are already used within the medical profession, including a drug derived from the tunicate species Ecteinascidia turbinate, which helps prevent patients from building up a resistance to chemotherapy drugs. Another commonly used substance is coagulan, a chemical derived from the unique blood of the horseshoe crab. These alien-looking invertebrates use amebocytes instead of white blood cells to fight infection, and theirs are so accurate that they coagulate rapidly around as little as one part in a trillion of bacterial contamination. Coagulan is therefore used to test medical equipment and vaccines for bacterial infection before they are used on humans, preventing the spread of disease in hospitals and other medical environments.
Pros and cons
The way in which coagulan is gathered is a good example of the drawbacks of using the ocean as a medical resource. Scientists are not yet effectively able to synthesize coagulan, and as a result, horseshoe crabs are taken from their environment on a massive scale in order to harvest their blood. In an attempt to prevent the decimation of this species, the crabs are drained of a percentage of their blood before being released alive back into the ocean. However, it is thought that even so, many crabs do not survive, leading to the potential future collapse of their population. We can only speculate on the deleterious consequences other marine species may face if they’re found to be of medical use.
With that being said, it is likely that cures, once found, will eventually be synthesized in order to facilitate mass production and to minimize the impact on the marine environment. Our increasing awareness of the ocean as a powerhouse for curing human health issues could also prove to be a great incentive for marine conservation. Perhaps if we start to see the ocean as the source of potential cures for cancer, Alzheimer’s, AIDS, or any other diseases that affect the human race, we will be encouraged to fight harder than ever before for its protection.