Research methods may pave the way for future new drugs from the sea
Images and video interview available upon request
October 2001 — Researchers
at Scripps Institution of Oceanography at the University of California,
San Diego (UCSD), have produced evidence that bacteria living inside a
small marine animal may be the source of a new drug compound being
developed to fight cancer.
The marine invertebrate Bugula neritina, a brown bryozoan
animal with stringy tufts that look like algae, appears unremarkable
and similar to a variety of moss-like sea creatures. In fact, bryozoans
are widely known by boat operators, who consider them ordinary fouling
organisms and often scrape them off their vessels’ hulls.
But their potential may be far from ordinary. Scientists
previously discovered Bugula neritina to be the source of bryostatins,
a family of chemical compounds currently being studied for their
ability to treat a variety of cancers. The anti-cancer drug Bryostatin
1 can be extracted from colonies of Bugula neritina.
The new study provides evidence that bacteria that live
inside Bugula neritina, and are passed in larvae from one generation to
the next, are the likely source of the anti-cancer compound.
"This paper presents a whole series of experiments from a
variety of different directions that provide evidence that this
bacteria may indeed be the agent for producing the drug," said Margo
Haygood, the senior author of the paper appearing in this month’s issue
of Applied and Environmental Microbiology.
Through the experiments, Haygood and her co-authors
identified a gene of the type that produces the compound. They also
showed that the gene is expressed solely in the bacteria, called
"Candidatus Endobugula sertula."
The findings pave the way for new studies in Haygood’s
laboratory, research that addresses problems historically facing the
development of drugs from the sea.
"Currently there really isn’t a practical way to produce
enough bryostatin for
people to use. Even if there were enough of the animals out there,
collecting enough would be environmentally destructive. This is one of
the biggest problems in the development of drugs from marine
organisms," said Haygood, an associate professor in the Marine Biology
Research Division and the Center for Marine Biotechnology and
Biomedicine at Scripps.
"There are many cases of these very interesting and useful
compounds that are found in marine invertebrates that are suspected to
be made by bacterial symbionts (organisms living in symbiosis with
another). This work is important because if we can use this
experimental system to unlock the potential of these bryostatin drugs,
it can serve as a model for many, many others."
Haygood’s new research is addressing two areas: Attempting
to cultivate and grow the bacteria outside of its natural environment
within Bugula neritina; and attempting to clone the genes that make the
drug and deliver them into an organism that can be more practically
produced in large quantities.
Most anti-cancer drugs act by killing any rapidly growing
cells, inevitably interfering with the body’s normal processes.
Bryostatin 1 "flips a switch" that controls how cells behave in the
body. In the case of leukemia cells, for example, it seems to bring
them to their senses and make them behave like normal blood cells. The
drug is now in clinical trials for use in humans.
Source : University of California – San Diego