Gene Therapy for Cancer Treatment - Biotechnology and Your Health: Pharmaceutical Applications - page 98

IMMUNE-BASED CANCER GENE THERAPY STRATEGIES
Many cancer cells are sufficiently different from related normal cells
that our immune system can recognize the differences and should
be able to attack the tumor as the unwanted interloper that it is. But
sometimes the differences may not be great enough, or the tumor
cells—wily creatures that they are—may have developed the ability
to ward off an immune system attack. Cancer is not one disease, but
many, and in most cases, specific changes in the genetic makeup of
cancer cells are responsible for the uncontrolled growth of that form
of cancer. Strategies to unleash an immune response to a particular
kind of cancer must take into account the type of cancer and its
genetic changes.
One strategy for immune-based gene therapy for cancer is
delivery to tumor cells of a gene for an immune system signal
protein that will kill the tumor cells or call up an immune attack.
Because immune system signal proteins such as interleukin-2 have
so many different kinds of effects, they are generally too toxic to be
administered to the whole body. Delivering the gene construct to
tumor cells so that they produce the protein themselves makes
more sense. Several immune system signal protein genes, including
interleukin-2, are being tested in this way, either alone or in
combination with conventional chemotherapy drugs or radiation.
Stop and Consider
Why do you think there are so many gene therapy trials for cancer?
A specific immune response requires the delivery of a small bit
of the target protein, the antigen , to immune system cells. Another
immune-based gene therapy approach being studied for cancer is to
engineer a patient's antigen-presenting cells outside of the body
with the tumor antigen gene, and then return the altered cells to the
patient to efficiently deliver the “call to arms” to the immune system