News Story The Coast News, July 1, 2004
Encinitas Doctor Makes a Breakthrough
By Joann Cachapero
Staff Writer
ENCINITAS-- Encinitas resident Dr. Jan Schnitzer announced
last week a breakthrough in cancer treatment research, resulting from
studies conducted by Schnitzer and his research team at the Sidney
Kimmel Cancer Center, in San Diego.
Study findings were published in the June 10 issue of the British science
journal, Nature.
"Dr. Schnitzer's work is offering the possibility of a whole new way
of targeting new blood vessels that we believe are of importance to
tumor growth, said Edward A Sausville, M.D., associate director for
clinical research at the University of Maryland Cancer Center. "As
such, I think it represents a very important opportunity, both diagnostically,
and potentially, in therapy."
As scientific director at the Kimmel Center, Schnitzer and his colleagues
utilized technologies developed there to pinpoint a protein unique
to the vascular system surrounding a solid tumor, but not present in
normal tissue.
"My team identified one single protein out of a million or so proteins
in the body that can be used to target a drug to travel freely into
a solid cancerous tumor," explained Schnitzer.
The protein, named AnnexinA1, became the specific target for laboratory-created
monoclonal antibodies loaded with a dose of therapeutic radioactive
drugs.
By using this method of direct delivery to the tumor, Schnitzer and his
team found they were able to use less medication, while effectively
administering a more potent dose to the tumor in a short amount of
time, usually within one to two hours.
"The antibody is the carrier system; a guided missile," explained Schnitzer,
"whereas the drug is the effector--the explosive in the warhead of
the guided missile."
The specificity of the antibody-to-protein connection also prevents normal
tissue from being affected by radioactive or chemotherapeutic medication
attached to the antibody. As such, there is potential to avoid the
debilitating side effects associated with traditional cancer treatments.
"Current cancer treatment drugs, which can destroy cancer tissue, but
with life-threatening side effects, could be transformed into drugs
which are totally safe and much more effective." said Albert B. Deisseroth,
M.D., Ph.D., Kimmel Center president and chief executive.
Also, because AnnexinA1 is present in the walls of blood vessels supporting
tumor growth, injected monoclonal antibodies use the circulating blood
as a vehicle so that medication administered by this method is absorbed
directly into the tumor; a step in advancing the treatment of cancerous
tumors that has evaded researchers since the discovery of monoclonal
antibodies in the 1980s.
Study experiments were conducted on 30 laboratory rats with aggressive
breast cancer tumors that has metastasized to the lungs.
A few days away from death, 10 of the rats received no treatment and
died. Another third of the study rats were injected with non-specific
radioactive antibodies, but also died within the same time period as
the rats that had not been treated. The final group of 10 was treated
with the AnnexinA1-specific antibody, tagged with a therapeutic radioactive
isotope.
Of those 10 rats, seven survived with their tumors efficiently destroyed.
Results of recent pathology studies, unpublished in the Nature article,
show the therapy requires five to seven days to destroy the solid tumors
completely.
While researchers are excited about the potential for advancement of
cancer therapies as a result of their findings, Schnitzer also points
out that there are uses for the new technology in the field of diagnostics,
as well as genetic therapies.
Using a technology called molecular imaging, researchers would be able
to track radioactive antibodies to their specific targets; in the case
of cancerous growths, tracker antibodies would seek out and find tumors
within hours of injection, leading to faster, noninvasive forms of
diagnosis.
As researchers single out more specific proteins, a greater possibility
exists to treat a wide range of diseases and conditions.
"Our novel target discovery and validation strategy can be applied to
most diseases by finding the key new targets that will improve drug
and gene delivery to single tissues of the body, not just tumors,"
said Schnitzer.
About a year away from the next step, Schnitzer's research will involve
human subjects.
"We need to go into the clinic to perform molecular imaging studies to
see if the antibody targets selectively solid tumors in humans as it
did in the rats, and then test its ability to destroy human tumors
in clinical trials," he explained. Researchers noted, in the study,
that blood vessel protein from biopsied tissue in human breast cancer
was almost identical to the AnnexinA1 protein found in the rats. Also,
biopsied tissues from lung, colon and prostate tumors were targeted
with the AnnexinA1 antibody with identical results.
Schnitzer, a graduate of Princeton and Yale, came to San Diego first
as an assistant professor at UCSD and then to conduct his work with
the Sidney Kimmel Cancer Center.
He has resided for the last six years in Encinitas with his wife, Melinda,
and their three children, Janina, Tad and Anna.
In the future, he hopes that his efforts in cancer research will bring
about "better, more human treatments for cancer patients that are more
effective in eradicating cancer."
