Human lung carcinoma monoclonal antibody specific for the Thomsen-Friedenreich antigen.

A monoclonal antibody, RS1-114, was raised against the human adenocarcinoma of the lung cell line A549. By studying the reactivity of RS1-114 with A549 cells following chemical and enzymatic treatments, it was shown that the epitope is a galactose-containing carbohydrate, which is devoid of sialic acid. Hemagglutination of desialylated RBCs, enzyme-linked immunosorbent assay studies with glycoprotein antigens before and after desialylation, and competition studies using peanut agglutinin indicate that monoclonal antibody RS1-114 recognizes the Thomsen-Friedenreich antigen, a cryptic determinant on human erythrocytes which can be exposed by neuraminidase treatment. It is expressed in an unhidden form on a large percentage of carcinomas and is therefore an important human tumor marker. RS1-114 is reactive with cryptic determinants of the Thomsen-Friedenreich antigen on white blood cells as well as red blood cells, and it reacts with unhidden determinants on human tumor cell lines. The number of binding sites on carcinoma cells is further increased by neuraminidase treatment. By immunohistochemical staining, it was shown that 75% of the human tumors tested are reactive with RS1-114. These include tumors of the breast, colon, lung, kidney, ovary, and rectum.