GAL-GALNAC - A BIOMARKER OF COLON CARCINOGENESIS

The disaccharide tumor marker Gal-GalNAc visualized by galactose oxida se-Schiff sequence is commonly present in cancer cells and in rectal m ucus of patients with colon cancer. The expression of this marker on t issue sections taken during experimental colon carcinogenesis shows ex cellent correlation with human precancerous lesions and cancers. A hig h proportions of 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 mark er is seen throughout the entire colon of patients with precancer and cancer; these include dysplasia, dilated and distorted crypts, regener ative dysplasia and hyperplastic crypts, as well as the morphologicall y normal crypts remote from cancer, Nearly identical pattern of Gal-Ga lNAc expression throughout the entire colon also appear during rat col on carcinogenesis induced by azoxzymethane including non-expression by the normal and regenerative epithelia during wound healing following mechanical injury. Thus, Gal-GalNAc detected by the simple technique o f galactose oxidase-Schiff sequence, is a biomarker that appears durin g the very early stages of progression of carcinogenesis. The expressi on pattern supports the field effect theory of carcinogenesis and also explains the basis for mass screening for cancer and precancerous con ditions. Chemoprevention strategy using Gal-GalNAc as an intermediate marker detected by accurate and cost-effective rectal mucus test may h ave great potential.