Eating Red Meat Can Stimulate Cancer Progression
Researchers have revealed that a new mechanism
for how human consumption of red meat
and milk products could contribute to the increased risk of cancerous tumors.
Their findings suggest that inflammation resulting from a molecule introduced through consumption of these foods could promote tumor growth.
The lead investigators of the study, Ajit Varki, M.D, a professor of medicine and cellular and molecular medicine from the University of California, San Diego School of Medicine (UCSD;La Jolla, CA, USA; http://medicine.ucsd.edu) and
codirector of the UCSD Glycobiology Research and Training Center, and colleagues studied a nonhuman
cellular molecule called N-glycolylneuraminic acid (Neu5Gc). Neu5Gc is a type of glycan, or sugar molecule, that humans do not naturally produce, but that can be incorporated into human tissues
as a result of eating red meat. The body then develops anti-Neu5Gc antibodies – an immune response that could potentially lead to chronic inflammation, as first suggested in a 2003 Proceedings of the [U.S.] National Academy of
Sciences (PNAS) article authored by Dr. Varki.
"We've shown that tumor tissues contain much
more Neu5Gc than is usually found in normal
human tissues," stated Dr. Varki. "We, therefore,
surmised that Neu5Gc must somehow benefit
It has been long recognized by scientists that
chronic inflammation can actually stimulate cancer,
Dr. Varki explained. Therefore, the
researchers wondered if this was why tumors containing
the non-human molecule grew even in the
presence of Neu5Gc antibodies. "The paradox of
Neu5Gc accumulating in human tumors in the
face of circulating antibodies suggested that a lowgrade,
chronic inflammation actually facilitated
the tumor growth, so we set out to study that
hypothesis," said coauthor Nissi M.Varki, M.D.,
UCSD professor of pathology. Using specially bred
mouse models that lacked the Neu5Gc molecule –
mimicking humans before the molecule is
absorbed into the body through ingesting red meat
– the investigators induced tumors containing
Neu5Gc, and then administered anti-Neu5Gc
antibodies to 50% of the mice. In mice that were given antibodies, inflammation was induced, and the tumors grew more rapidly. In the control mice
that were not treated with antibodies, the tumors were less aggressive
Other investigators have previously shown that humans who take nonsteroidal anti-inflammatory drugs (NSAIDs) 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.
Dr. Varki's findings were published online
November 11, 2008, in advance of print publication
in the journal Proceedings of the [U.S.]
National Academy of Sciences (PNAS).