Twenty fresh surgical specimens of human bladder tumors were tested for their ability to adhere to recombinant P and E-selectin. The adhesion was correlated to immunological detection of carbohydrate structures.Materials and Methods
A static titertray assay with immobilized selectins and appropriate controls was used for bladder tumor cell adhesion. On the same tumors expression of carbohydrate structures was examined by immunohistochemistry and Western blotting.Results
No tumor bound to P-selectin. Nine tumors showed a high number of cells binding to E-selectin, 5 showed intermediate binding, and 6 showed only rare binding. The specificity of the binding was verified by inhibition with EDTA, by blocking antibodies to E-selectin, and by an acrylamide based sLex (Gal beta 1-4 [Fuc alpha 1-3]GlcNAc-) polymer. The binding was significantly more frequent (p <0.045) in superficial tumors than in invasive tumors. The binding property was correlated to the detection of carbohydrate structures in Western blots and tissue sections of the same tumors, using six different monoclonal antibodies: anti-sLea, anti-sLex, anti-Lea, anti-Lex (two different clones) and anti-Leb. Most blot-stainings were smeared indicating a mucin-type carrier molecule, but 115, 55 and 40 kDa bands carrying Lea and/or Leb epitopes were present in all tumors that bound. The Lea structure, as detected by blotting, was the only structure necessary for binding in the center of the wells (p <0.001), and was correlated to number of bound cells (p <0.006). A weaker correlation was found between Leb and number of bound cells (p <0.032), whereas it was remarkable that no correlation was found with Lex or sLex. Immunohistological staining of Lea on cell membranes correlated with frequent binding (p <0.003), whereas no correlation was found to secretor and Lewis genotypes.Conclusions
These data on clinical specimens indicate that Lewis antigen mediated E-selectin adhesion may play a role in the human bladder cancer disease.