By increasing production of a blood pressure-regulating enzyme in mice, researchers have found they can enhance the mouse immune system's ability to sense tumor growth.
When scientists at Emory University School of Medicine engineered mice that make more angiotensin-converting enzyme in white blood cells called macrophages, the mice could more effectively limit the growth of injected tumors.
The enzyme works by "trimming" small bits of protein that originate from the tumors, allowing the immune system to identify the tumors and mount a response more efficiently.
The results are published online in the Journal of Biological Chemistry (JBC).
Senior author Kenneth Bernstein, MD, Emory distinguished service professor of pathology and laboratory medicine, says his group's findings suggest a strategy for amplifying immune system function in humans.
"We think we've discovered a means of tweaking the immune response by modifying the process of antigen presentation," Dr. Bernstein says.
In the clinic, doctors might be able to enhance a cancer patient's ability to resist a tumor by removing his or her white blood cells, boosting their production of angiotensin-converting enzyme, and re-infusing them, he says.
Antigen presentation refers to how proteins from within the body are constantly recycled and chewed up into small bits called peptides, which appear on the surfaces of cells. While the immune system generally ignores peptides from proteins in the body, it can respond to the peptides from foreign invaders.
Angiotensin-converting enzyme, or ACE, plays a critical role in controlling blood pressure and is the target of common medications. The hormone angiotensin (a peptide) constricts blood vessels, increases the brain's perception of thirst and indirectly causes the kidneys to retain sodium, thus limiting its production can reduce blood pressure.
ACE acts chemically by removing amino aci
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