Scientists have shown for the first time that the immune system of a mouse can completely destroy cancer cells in the prostate. Experts say the discovery, published in today's issue of Proceedings of the National Academy of Sciences , could open the door to an immune-based therapy for prostate cancer, the second the most common cause of cancer death for. men
for the body's defense system to launch an attack against an invader, the immune system cells called T cells must detect two different signals. "It's like the two keys that must be turned simultaneously to launch a nuclear missile," says Eugene Kwon, a urologist at the National Heart, Lung, and Blood Institute When a cell becomes cancerous, one of these signals. - the antigen, an immune system protein considered foreign -. is expressed on the surface of cancer cells themselves the second signal, a protein called B7, is always present on the surface of said antigen-presenting cells which present the antigen to the immune system. This primer T cells to attack the cells bearing the antigen, including cancer cells. But for yet unclear reasons, certain cancers, including prostate, do not enable a strong immune response .
to show that T cells in mice are able to mount a sustained attack against cancer cells of the prostate, Kwon and his colleagues made the cancer cells themselves express B7. (Essentially, they bypassed intermediaries, antigen presenting cells). They extracted cancer cells from preliminarily reared mice to develop a prostate cancer spontaneously added and the B7 gene of mice so that the cells express the B7 protein. Within a week to inject these cancer cells under normal mouse skin, tumor cells were completely destroyed by T cells. After 0 days, the cancer cells had still not grown
After this success, Kwon and colleagues tried a different approach: They turn off cell Security T outlet. Normally, T cells deactivate after a protein called CTLA-4 protein absorbs B7 alarm signal. But if it happens before all the cancer cells are destroyed, the tumor is likely to recur. Researchers injected cancerous prostate cells in healthy mice; then 7, 10 or 13 days later, they were injected with a protein that binds to CTLA-4, such as B7 continue to activate T cells Cancerous prostate cells in 42% of mice (21 to 50) were completely eliminated by the immune system. Treatment significantly slowed tumor growth in the rest of mice. Because the effect of the rise in T cell plan is temporary, the mice did not suffer autoimmune or inflammatory disorders.
"There is a sensible approach seriously immunologists," said Tom Waldman, a clinician at the National Cancer Institute. "I think they should go ahead with human trials." Team member James Allison, an immunologist at the University of California, Berkeley, said he hoped that this strategy probably used in conjunction with other treatments such as chemotherapy low level, can be tested in the man within the next two years.
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