Differences in the pattern of endogenous lectins from spontaneous rat mammary tumors

Three spontaneously occurring rat mammary tumors, a fibroadenoma and two tubulopapillary adenocarcinomas, differing in their degree of histologic differentiation and malignancy, were investigated. They revealed significant differences in the pattern of carbohydrate-binding proteins with specificities for alpha- and beta-galactosyl, alpha-mannosyl, and alpha-fucosyl moieties, respectively. Analysis was performed by affinity chromatography on resins with immobilized sugars or glycoproteins and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The patterns were divided into categories according to the dependence of binding activity on the presence of Ca2+ and to dependence on extraction conditions. In comparison with both adenocarcinomas, the fibroadenoma contained alpha- and beta-galactoside-binding proteins at apparent molecular weights of 74,000 and 130,000. These proteins were not found in either adenocarcinoma. Comparison between the two adenocarcinomas revealed qualitative differences for all classes of carbohydrate-binding proteins under investigation. These differences between tumors of the same tumor class (mammary tumors) and tumor type (tubulopapillary adenocarcinoma) allow for the proposal that the pattern of endogenous carbohydrate-binding proteins may be potentially useful as a diagnostic marker.