Lectins as probes for identification of tumor-associated antigens on urothelial and colonic carcinoma cell lines

Abstract

In the search for tumor-associated antigens, seven lectins were used to investigate the cellular distribution of membrane-associated glycoproteins on a panel of human cells derived from tumor or normal tissues. Surface labelled lysates of the different cells were precipitated with the lectins and the precipitates were separated on SDS-PAGE. Comparison of the autoradiographic patterns revealed that a La-reactive 115K glycopeptide (gp 115) was present on transitional-cell carcinoma cells of the urinary bladder, on two spontaneously transformed urothelial cell lines and on a melanoma cell line. Gp 115 was absent from a non-transformed urothelial cell line, a squamous bladder carcinoma line and five unrelated cell lines of miscellaneous tissue origin. When precipitation was performed with a rabbit antiserum raised against the La-reactive components of a TCC cell line the same distribution of gp 115 was observed. From Helix pomatia hemagglutinin (HP) precipitates a 150K glycopolypeptide co-migrating with a previously described HP-reactive differentiation antigen associated with human T cells was present on one of the urothelial cell lines and on a colon carcinoma cell line. When different extracts depleted of ConA binding glycopeptides were compared, a group of three antigens (32K, 35K and 40K) were identified in the extracts of the colon carcinoma cell line, HT29. These antigens were shared by two other colon carcinoma cell lines but were absent from the unrelated cells of our panel. Furthermore, an extensively absorbed rabbit anti-HT29 serum specifically precipitated one of these antigens (35K) from the three colon cell lines.