Differential expression of endogenous sugar-binding proteins (lectins) in murine tumor model systems with metastatic capacity

Abstract

In order to investigate possible differences in sugar binding activities of strongly versus weakly metastatic tumors, sugarbinding molecules (endogenous lectins) of murine tumor cells differing in metastatic capacity were analyzed by affinity chromatography on supports with immobilized sugars or glycoproteins and compared. After elution with specific sugar in the absence of Ca²⁺‐ions, the proteins were separated by sodium dodecyl sulfate‐polyacrylamide slab gel electrophoresis. In comparison to a weakly metastatic subline (Eb) spontaneous strongly metastatic variants (ESb) of a murine lymphoma contained additional sugar receptors for N‐acetylglucosamine (M_r 30 kDa) and maltose (M_r 64 kDa, 62 kDa, 54 kDa and 32 kDa), and lacked one sugar receptor for myoinositol (M_r 85 kDa), N‐acetylglucosamine (M_r 23 kDa) and maltose (M_r 22 kDa), respectively. The strongly metastatic variant ESb expressed the common β‐galactoside‐specific lectin to a higher extent and receptors for myo‐inositol, melibiose and mannan to a lower extent. In another model system derived from the murine mastocytoma cell line P 815 × 2A, biochemical analysis of the liver‐metastasizing variant P 815 × 2B revealed additional characteristic N‐acetylgalactos‐amine‐ and maltose‐specific binding proteins. This variant had reduced amounts of receptors for β‐galactosides and fucose in comparison to the parental clone. In a third tumor system a similar qualitative difference was disclosed: a metastatic variant derived from spleen metastases displayed a sugar receptor profile with 5 additional β‐galactoside‐binding proteins when compared to its parental clone 6‐6#3 + F, which is a virally transformed fibroblast line. The results show that metastatic variants of 3 murine tumor models consisting of lymphomas, mastocytomas and sarcomas are characterized by qualitative and quantitative alterations in the profiles of sugar‐binding proteins.