How eating red meat, milk can promote increased cancer spread risk

Washington, Nov 14 : A research team led by an Indian-origin scientist at the University of California, San Diego School of Medicine have shown how eating red meat and milk products could increase the risk of cancerous tumours.

Ajit Varki, M.D., and colleagues have found that inflammation resulting from a molecule introduced through consumption of these foods could promote tumour growth, For the study, the researchers examined a non-human cellular molecule called N-glycolylneuraminic acid (Neu5Gc), which is a type of glycan, or sugar molecule, that humans don't naturally produce, but that can be incorporated into human tissues as a result of eating red meat.

As already known, the body then develops anti-Neu5Gc antibodies - an immune response that could potentially lead to chronic inflammation.

"We've shown that tumour tissues contain much more Neu5Gc than is usually found in normal human tissues. We therefore surmised that Neu5Gc must somehow benefit tumours," said Varki.

He said that scientists have known that chronic inflammation can actually stimulate cancer, thus they speculated this to be the reason why tumours containing the non-human molecule grew even in the presence of Neu5Gc antibodies.

"The paradox of Neu5Gc accumulating in human tumours in the face of circulating antibodies suggested that a low-grade, chronic inflammation actually facilitated the tumor growth, so we set out to study that hypothesis," said co-author Nissi M.Varki, M.D., UCSD professor of pathology.

They used specially bred mouse models that lacked the Neu5Gc molecule - mimicking humans before the molecule is absorbed into the body through ingesting red meat - and induced tumors containing Neu5Gc, and then administered anti-Neu5Gc antibodies to half of the mice.

It was found that in mice that were given antibodies inflammation was induced, and the tumours grew faster. In the control mice that were not treated with antibodies, the tumours were less aggressive

Earlier it was shown that humans who take non-steroidal anti-inflammatory drugs (commonly known as NSAIDs) have a reduced risk of cancer.

Thus, the mice with cancerous tumours facilitated by anti-Neu5Gc antibodies were treated with an NSAID, which blocked the effect of the Neu5Gc antibodies in these animals and also reduced the size of the tumours.

"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 Varki.

The study is published online in advance of print publication in the Proceedings of the National Academy of Sciences (PNAS).

ANI