Biomedical Engineering Reference
In-Depth Information
to block angiogenesis by delivering to a tumor a vector with a gene
that would prevent angiogenesis as the tumor increases in size, thus
starving the tumor. This method has been effective in animal tests
but has not yet been tested on humans.
The large number and types of gene therapy trials for cancers
reflect both the potential opportunities to develop treatments
and the fact that a single strategy will not likely work for all forms
of cancer.
The Use of Antisense
Another promising molecular approach to treating cancer, studied
for decades, uses specific RNA molecules to target oncogenes and
other genes that permit a cancer cell to thrive and grow. The goal is
to prevent the production of the protein that causes the uncontrolled
division of tumor cells. The idea behind this approach is that a short
piece of DNA or RNA would bind specifically to a messenger RNA,
founded on its sequence of bases, and prevent the message from
being used to make the protein. This would stop the cell division of
cancer cells and possibly cause cancer cells to die.
Synthetic RNA and DNA drugs have been named
antisense
because they were crafted to bind to the single strand of the RNA
message, the “sense” sequence that would normally be translated
into protein. As more and more oncogenes were implicated in the
ability of specific cancer cells to divide and increase in number
without normal controls, efforts were made to produce an RNA
antisense drug that stopped that growth. Although test-tube studies
in the lab have often been successful, antisense drugs face
formidable challenges. They must resist being broken down by
enzymes in the blood. They must also be able to get to and
into the cells. They also need to be able to clamp onto the targeted
message once they get inside the cell.
A number of different chemical modifications of the basic RNA
antisense have shown promise in the lab and in animal test systems,
(continued on page 104)
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