WASHINGTONThe human body has strong immune defenses against cells of
foreign species. For example, cells that produce a sugar known as
galactose-alpha(1,3)galactose, found in many mammalian species but not in
humans, trigger a hyperacute response in humans that destroys the great
majority of the interloper cells. Cancer cells, however, which also contain
many molecules not found in normal cells, nonetheless often elude the immune
A single enzymealpha(1,3)galacto-syltransferase or alpha-GTcreates the
foreign sugar. Now, researchers at the Stoddard Cancer Research Institute,
Methodist & Lutheran Health System, Des Moines, are trying to exploit the
natural immunity of the human to the nonhuman enzyme and turn the immune
system that attacks foreign species cells against human breast cancer cells.
Charles J. Link, Jr., MD, director of the Institute, reported the work at
the Susan G. Komen Breast Cancer Foundation 5th Annual Conference on
Innovations in Quality Care.
Getting that foreign enzyme into human breast cancer tissues would produce
the sugar, causing the immune system to perceive the breast cancer cells as
foreign and destroy them, Dr. Link explained.
In effect, breast cancer cells infected with the foreign enzyme and
introduced into a patient would act as a vaccine against the individual’s own
breast cancer cells.
Tests on a mouse model have thus far proved the theoretical principle, Dr.
Link said, and data are being gathered with an eye toward undertaking human
trials. To that end, the alpha-GT gene has been cloned into an artificial
herpesvirus that has a high propensity for infecting breast cells.
In the animal studies, breast cancer was induced both in knockout mice
lacking alpha-GT and in normal mice. The gene was then inserted into the
knockout mice.The virus-borne alpha-GT infection afforded the knockout mice
"complete protection" from breast cancer cells, Dr. Link said, whereas every
one of the normal controls had died of the cancer within 17 days.