05:19 PM ET 01/31/97
New gene therapy could treat prostate cancer
Release at 6:30 P.M. EST
By Andrea Orr
LOS ANGELES (Reuter) - Researchers have discovered a highly precise and potent way to target prostate cancer that could lead to a new treatment that is safer and more effective than
chemotherapy, a new study reported Friday.
The treatment would work by injecting genes into the
prostate that kill the cancer cell while sparing the surrounding
healthy cells -- a method the author of the study likens to a
''smart bomb.''
The study of this genetically engineered attack on prostate cancer was conducted at the Jonsson Comprehensive Cancer Center at the University of California at Los Angeles. The findings are published in the Feb. 1 issue of the journal ``Cancer
Research''.
``Chemotherapy can not differentiate between the good and
the bad cells,'' Dr. Arie Belldegrum, principal investigator for
the study and chief of Urologic Oncology at the UCLA School of
Medicine told Reuters. ``We are attempting to create a smart
bomb.''
While the concept of gene therapy to treat cancer is not
new, Belldegrum's team has discovered a delivery system that
transports a genetically-altered, cancer-killing gene 1,000
times more effectively than previously known methods.
Prostate cancer is the most common form of cancer in men,
and kills about 40,000 men in the U.S. each year.
But unlike most other forms of cancer, prostate cancer is
also the ideal target for gene therapy because it is almost always associated with a substance in the blood stream, known as the protein specific antigen, or PSA.
All people have PSA genes but only the presence of prostate cancer activates them to produce the protein specific antigen. For this reason, doctors can usually detect prostate cancer with a simple blood test.
``With colon or breast cancer we don't have such specific
markers,'' said Dr. Belldegrum.
Recognizing the value of this specific marker, researchers
have often focused their gene therapy experiments on prostate
cancer, using the promoter, or driver region of the PSA gene to
direct a so-called suicide gene to the targeted cancer cells.
But while the concept worked in theory, the activity has in the past been too weak to work on patients. What the UCLA research team discovered to make it more practicable is the enhancer region on the PSA gene, which they say makes the treatment 1,000 times more effective by boosting the effectiveness of the delivery system.
In tests, the genetically engineered PSA genes have been
shown to attack human prostate cancer cells growing in mice. Dr.
Belldegrum said the researchers are now preparing to apply for
Food and Drug Administration approval to begin experimenting
with the therapy on people within a year or two.
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