The
disaccharide tumor marker Gal-GalNAc visualized by
galactose oxidase-Schiff sequence is commonly present in
cancer cells and in rectal mucous of patients with
colon cancer. The expression of this marker on tissue sections taken during experimental colon
carcinogenesis shows excellent correlation with human precancerous lesions and even higher percentage of
colon cancers express this marker, whereas, no expression is seen in the normal human large intestine. Multifocal expression of the marker is seen throughout the entire colon of patients with precancer and
cancer; these include dysplasia, dilated and distorted crypts, regenerative dysplasia and hyperplastic crypts, as well as the morphologically normal crypts remote from
cancer. Nearly identical pattern of
Gal-GalNAc expression throughout the entire colon also appear during rat colon
carcinogenesis induced by
azoxymethane including non-expression by the normal and regenerative epithelia during wound healing following mechanical injury. Thus,
Gal-GalNAc detected by the simple technique of
galactose oxidase-Schiff sequence, is a
biomarker that appears during the very early stages of progression of
carcinogenesis. The expression pattern supports the field effect theory of
carcinogenesis and also explains the basis for mass screening for
cancer and
precancerous conditions.
Chemoprevention strategy using
Gal-GalNAc as an intermediate marker detected by accurate and cost-effective rectal mucus test may have great potential.