Differential expression of tumor-associated antigens in human colon carcinomas xenografted into nude mice

The tumor-associated antigen profile of a number of different human colon carcinomas xenografted into inbred Swiss nude mice was examined to determine whether the tumors could serve as useful models for antigen purification, radioimmunodetection, and immunotherapy. Extreme heterogeneity was observed both by radioimmunoassay and immunohistochemical procedures for the expression of carcinoembryonic antigen (CEA), colon-specific antigens (CSAp), and colonic mucin antigen (CMA) within the tumors. Four of 10 tumors (DLD-2, DLD-3, DLD-5, and HCT-10) were high producers of CEA (greater than 75 micrograms/g wet tissue wt). Two of these (DLD-2 and HCT-10) correlated with a high production of CSAp and CMA, whereas the other 2 produced low quantities of these antigens. Another tumor, HCT-14-OM1, produced large amounts of CMA yet produced moderate amounts of CEA and low quantities of CSAp. Immunohistochemical analyses of CEA gave a mostly diffuse cellular and cell surface staining for all of the tumors. Staining for CSAp was very focal, as in DLD-5 where only a few of the tumor cells were stained. Staining of CMA was limited; however, DLD-2, HCT-10, and HCT-14-OM1 showed intense cystoplasmic and intraluminal staining. A determination of the tumor antigen profile may be useful in characterization and classification of the tumor as well as enabling the selection of the proper antibody or antibodies for immunodetection and immunotherapy.