Use of sialylated or sulfated derivatives and acrylamide copolymers of Galβ1,3GalNAcα- and GalNAcα- to determine the specificities of blood group T- and Tn-specific lectins and the copolymers to measure anti-T and anti-Tn antibody levels in cancer patients

Abstract

Sialylated or sulfated derivatives and acrylamide copolymers of blood group T-(Galβ1,3GalNAcα-) and Tn-(GalNAcα) haptens were studied for their interaction with the lectins of peanut (PNA),Agaricus bisporus-(ABA),Helix pomatia-(HPA) andVicia villosa B₄-(VVA), using asialo Cowper's gland mucin (ACGM), which contains both T and Tn epitopes, as the coating substrate in enzyme linked lectin assay. Both T and Tn copolymers (∼40 haptens) showed high affinity and strict specificity; although the T-copolymer at 0.05–0.07 µm concentration caused 50% inhibition of interaction of either PNA or ABA with ACGM, there was little inhibition of the HPA and VVA interactions at over 100 times that concentration. The Tn-copolymer at 0.02–0.05 µm inhibited HPA or VVA interaction with ACGM by 50% but gave virtually no inhibition of PNA and ABA binding. Sialyl, sulfate or methyl group substitution on C-6 of GalNAc of the T-haptene did not prevent interaction with PNA but almost abolished interaction with ABA. In contrast, sialyl or sulfate group on C-6 and sulfate on C-3 of Gal in Galβ1,3GalNAcα- inhibited almost completely the interaction of PNA with ACGM but had only a slight effect on the interaction of ABA; C-6 substitution with either sialic acid or sulfate on GalNAcα- almost abolished the interaction of both HPA and VVA with ACGM. Preliminary studies revealed a significant depression in the serum level of anti-T (two to three-fold decrease) and anti-Tn (∼ two-fold decrease) antibodies in breast cancer compared with normal control subjects when the acrylamide T- and Tn-copolymers were used as coating substrates in enzyme linked immunoassays.