Researchers at the University of California, San Diego School of Medicine say antibodies to a non-human sugar molecule commonly found in people may be useful as a future biomarker

It is published in the April 19 online issue of the journal Cancer Research and in the May 1 print edition.
Every animal cell is cloaked in complex molecules called sialic acids that serve as vital contact points for interaction with other cells and the surrounding environment. Humans produce a particular kind of sialic acid called N-acetylneuraminic acid (Neu5Ac), but can also carry another non-human type called N-glycolylneuraminic acid or Neu5Gc, which is obtained through the diet, notably by the consumption of red meat. The molecular structures of these sialic acids differ by just a single oxygen atom, but this difference is enough to prompt the human immune system to produce a complex anti-Neu5Gc response.
In previous research, Varki and colleagues described how low-dose anti-Neu5Gc antibodies can lead to chronic inflammation, an immunological response associated with cancer development and growth. In the new work, using a novel sialoglycan-microarray, the team discovered that patients with carcinomas have elevated levels of antibodies to one specific Neu5Gc-containing sugar chain. This unusual antigen arises from dietary Neu5Gc incorporation into the cancer marker Sialyl-Tn. It is the first example of a biomarker in the form of human "xeno-autoantibodies" to a dietary molecule.
Following up on this discovery, the scientists also found that purified human anti-Neu5Gc antibodies have immunotherapeutic potential: they specifically kill Neu5Gc-expressing mouse or human tumors when applied at higher concentrations. These findings point to a dual response of anti-Neu5Gc antibodies that can either stimulate tumor growth at a low dose (serving as a biomarker of disease) or suppress tumor growth at a high dose.
"Precisely how therapeutic antibodies work in patients remains unclear, even in therapies already approved by the Food and Drug Administration," said Schwab. "It is likely a combination of signaling immune cells to kill cancer cells and antibodies directly killing cells by recruiting other proteins in the body. Understanding how lower levels of antibodies stimulate cancer growth while strong responses can kill cancer cells will be critical to moving this approach safely into cancer treatment."
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Nonetheless, Schwab expressed optimism about the significance and future of the work.
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Source-Newswise