EXPRESSION OF A-BLOOD-GROUP AND H-BLOOD-GROUP AND OF CD44 ANTIGENS DURING CHEMICAL RAT COLONIC CARCINOGENESIS

Using an experimental model of rat colon adenocarcinoma, we have recen tly shown that the presence of H blood-group antigen on variants of th e CD44 adhesion molecule carrying amino acids encoded by exon v6 (CD44 v6), increased the cells' tumorigenicity. In the present study, colon adenocarcinomas were induced by 1,2-dimethylhydrazine treatment in rat s. Using immunohistochemistry, biopsies of normal, precancerous and ca rcinomatous colon mucosa were evaluated for expression A and H blood g roup antigens and CD44s and CD44v6 antigens. Normal rat colon showed s trong and homogeneous expression of blood-group antigen A, but weak ex pression of H antigen. Several weeks before the appearance of tumours, dysplastic glands were strongly stained with anti-H reagents, while t heir A antigen was lost. Expression of CD44v6 was weak and restricted to some cells at the bottom of normal crypts. No obvious change was ob served before appearance of severe dysplasia. In carcinomas, a strong but irregular expression of A, H and CD44v6 antigens was observed. In moderately differentiated carcinomas, A and H antigens were present at the apical surface of cells, whereas CD44v6 was found at the basolate ral side. Only carcinomatous cells with loss of polarity, found in poo rly differentiated cancers or infiltrated in the muscularis mucosae, w ere found to coexpress blood-group H or A and CD44v6 antigens at their surface.