Molecule in red meat, milk linked to cancer progression
November 14, 2008
by Keith Nunes
LA JOLLA, CALIF. — Consumption of red meat and milk products may contribute to the increased risk of cancerous tumors, according to research conducted at the University of California at San Diego’s School of Medicine. The researchers’ findings suggest inflammation resulting from a molecule introduced through consumption of the foods may promote tumor growth and were published online this week in advance of print publication in the Proceedings of the National Academy of Sciences.
Dr. Ajit Varki, M.D., a distinguished professor of medicine and cellular and molecular medicine, and co-director of the U.C.S.D. Glycobiology Research and Training Center, and colleagues studied a non-human cellular molecule called N-glycolylneuraminic acid (Neu5Gc). Neu5Gc is a type of glycan, or sugar molecule, that humans don’t naturally produce, but that may be incorporated into human tissues as a result of eating red meat. The body then develops anti-Neu5Gc antibodies – an immune response that may lead to chronic inflammation,
"We’ve shown that tumor tissues contain much more Neu5Gc than is usually found in normal human tissues," said Dr. Varki. "We therefore surmised that Neu5Gc must somehow benefit tumors."
The researchers’ study used specially bred mice that lacked the Neu5Gc molecule and mimicked humans before the molecule is absorbed into the body through ingesting red meat. The researchers induced tumors containing Neu5Gc, and then administered anti-Neu5Gc antibodies to half of the mice. In mice that were given antibodies inflammation was induced, and the tumors grew faster. In the control mice that were not treated with antibodies, the tumors were less aggressive.
Other researchers have shown that humans who take non-steroidal anti-inflammatory drugs have a reduced risk of cancer. Therefore, the mice with cancerous tumors facilitated by anti-Neu5Gc antibodies were treated with an NSAID. In these animals, the anti-inflammatory treatment blocked the effect of the Neu5Gc antibodies and the tumors were reduced in size.
"Taken together, our data indicate that chronic inflammation results from interaction of Neu5Gc accumulated in our bodies from eating red meat with the antibodies that circulate as an immune response to this non-human molecule – and this may contribute to cancer risk," said Dr. Varki.
The study was funded in part by a grant from the National Cancer Institute of the National Institutes of Health.