DIFFERENTIAL EXPRESSION OF ALPHA-2,6-SIALYLTRANSFERASE IN COLON TUMORS RECOGNIZED BY A MONOCLONAL-ANTIBODY

It has been reported that alpha 2,6-sialyltransferase (alpha 2,6-ST; E .C. 2.4.99.1) activity is associated with cellular differentiation. To define its role in colon carcinoma differentiation, we have generated murine monoclonal antibodies (MAb) against alpha 2,6-sialyltransferas e. The MAb, designated 6B9 of IgM isotype, showed strong reactivity wi th the purified and crude alpha 2,6-ST by ELISA and dot blot assays. W estern blotting with MAb 6B9 identified purified alpha 2,6-ST of MW 47 kDa and the same MW protein from rat and human liver extracts. The MA b also reacted with two other liver proteins of approximate MW 65 and 100 kDa, Immunoperoxidase studies with formalin-fixed paraffin-embedde d tissues showed that MAb 6B9 reacts with liver tissues, the staining of hepatocytes was granular and cytoplasmic, There was a distinct patt ern of zonal distribution of this enzyme in hepatocytes located partic ularly in the portal areas of the liver corresponding to zone 1, Norma l colon (100%) and hyperplastic polyps (100%) showed very weak to no r eactivity, Adenomas (100%) demonstrated moderate reactivity, while the poor (33%), moderate (100%) and well-differentiated (80%) colon adeno carcinomas showed strong reactivity, Results suggest that alpha 2,6-ST is associated with the differentiation state of colon tumors.