90 P - Association Of Lactosamine Type 2 Oligosaccharide Structures with MUC-1 Apomucin in the Human Breast Cancer Cell Line SKBR5

Tumor-associated mucins are high molecular weight plycopeptides Involved in the cytoedhesive properties of cancer cell. The proadhesive ection of mucins seems to rely on the high degree of glycolisation, In particular on the high content of lactosamine type 2 carbohydrate structures of the Lewis (Le) family. In order to charecterize the carbohydrate profile of tumor-associate mucins, we determined the expression of Le carbohydrate antigens on soluble tumor mucins secreted by the LeY + human breast cancer cell line SKBR5. Aller purification of mucins by gel permeation chromatography followed by Immunoprecipitation with the anti LeY mAb ABL 364, the obtained LeY-carrying mucin was tested for the reactivity with a panel of carbohydrate-specific mAb's. As determined in a crossed determination ELISA system, the LeY-carrying mucin showed a strong reactivity With mAb's directed against the lactosamine type 2 epitopes LeX and sialyl. LeX (sLeX) We also determined the reactivity of the LeY-carrying mucin with mAb SM-3 directed against the protein core of MUC-1, an apomucin synthesized by various breast cell lines in vitro. In crossed immunodetermination ELISA there was only a weak binding of mAb SM-3 to the LeY reactivity material. However, the binding reactivity increased significantly When the meterial was pretreated with neuraminase. In conclusion, our data demonstrate that In SKBR5 mucins (a) the LeY oligosaccharide structure is associated With the MUC-1 apomucin and (b) beside leY. In SKBR5 cells the MUC-l apomucin additionally bears the laetoeamine type 2 oligosaccharide structures LeX and sLeX. Since the detection of the MUC-1 core protein by mAb SM-3 requires the pretreatment of the soluble material with neuraminase, our findings also suggest lhat the content of sialic acid playa an Important role in determining the antigenellc profile of LeY-reactive mucins synthesized by SKBR5 breast cancer cells.