Identification and purification of an organ specific, tumor membrane associated antigen from a spontaneously metastasizing rat mammary carcinoma

An organ specific (common histotypic) antigen has been identified and partially purified from a spontaneously metastasizing rat mammary carcinoma, TMT-081. The antigen is present in the tumor at a level about 50–200 times greater than in non-malignant, hyperplastic mammary tissue.

The antigen is a membrane associated glycoprotein and was solubilized by limited papain digestion of tumor cell membranes or by extraction with non-ionic detergent. Partial purification of papain solubilized antigen by gel filtration and lectin affinity chromatography yielded material that was 50% precipitable by a specific rabbit antibody reagent obtained from antiserum raised against the tumor. The apparent molecular weight of the partially purified antigen was about 28.000 as determined by SDS-PAGE. Quantitation of the antigen was accomplished by a sensitive binding inhibition radioimmune assay. The antigen was present in hyperplastic mammary tissue and was not detected in other normal adult or fetal rat tissues and in a polyoma virus induced syngeneic rat fibrosarcoma. The antigen could be detected in the serum of tumor bearing animals at concentrations reflecting the tumor mass present.