Medicinal Uses

The Story:
    In 1945, Werner Bergmann, an organic chemist studying the shallow water sponges off the shore of Elliot Key, Florida, stumbled across a peculiar unidentified sponge.  It was not until a few years later that Bergmann and his taxonomist colleague, Dr. M. W. de Laubenfels, found more of this strange new species.  However, this time they named it, Cryptotethia crypta, and took it back to the lab.  At this point Bergmann had been trying to isolate and study sterols, derivatives of steroids, from marine organisms in his area.  When he finally got Cryptotethia crypta back to his lab and boiled the body mass in liquid ether he noticed that a large amount of some unidentifiable crystalline substance was separated.  Upon examination he noticed that the substance was not characteristic of the sterols that he was looking for.  Instead, it exhibited optic activity, as well as an ultraviolet absorption spectrum that was very similar to the nucleotide, thymidine.
    Thymidine is a combination of a pyrimidine nucleic base, thymine, bonded to a dioxyribose, or a sugar group.  In short, this is a sequence found in DNA, and the compound that Bergmann isolated was extremely similar to this molecule; because of this, the “new” compound was named spongothymidine.  Over the next few years Bergmann continued studying this particular Cryptotethia crypta extract and was able to isolate another similar compound that exhibited characteristics of the uridine, found in RNA.  Similarly, it was named spongouridine.  Today we know the two compounds as 3-beta-D-arabofuranosylthymine and 3-beta-D-arabofuranosyluracil respectively.

    As said before, these two compounds had striking similarities to thymidine and uridine.  The only difference was that thymidine had a deoxyribose sugar base (characteristic of DNA) and uridine has a ribose sugar base (characteristic of RNA), while the isolated compounds both had an arabinose group (sugar bases containing two anti-parallel alcohol groups on the second and third carbons).

    

This is where it gets juicy...
    These two compounds were found to be even more interesting because of their location in the Cryptotethia crypta organism.  Unlike their look-alike compounds found in DNA and RNA, these isolated compounds were in a free-state in the sponge.  In other words they were not incorporated with any DNA or RNA sequences and in fact seemed to inhibit DNA/RNA replication.  This led scientists to hypothesize that instead of being the building blocks that construct all living things on earth, they were used as a defense mechanism for Cryptotethia crypta.
    With this discovery, Seymour Cohen, another scientist interested in sponges, drew the first parallels between the simple sponge’s defense mechanism and the implement of the same kind of treatment to human cancer patients.  With his research in the 1950’s, along with lab work with other researchers of the time, a synthetic derivative of the spongothymidine found in Cryptotethia crypta, arabinosyl cytosine (ara-C), was found to successfully cure rats infected with cancer cells without killing them.  More work done by John Evans supporting these results with the same ara-C compound showing successful inhibition of leukemia cells.
    Today, the same ara-C compound is popularly used in cancer treatments.  It is now constructed as a liposomal (surrounded by a lipid, hydrophopic layer) drug know as Liposomal ara-C.  The drug is classified as a anti-metabolite, or a cell replication inhibitor, and used in most all chemotherapy treatments.