Ultrastructural immunolocalization of tumor-associated glycoprotein (TAG-72) in human gastric and mammary carcinomas

Ultrastructural immunolocalization of tumor-associated glycoprotein (TAG-72) was studied using murine monoclonal antibody (MoAb) B72.3 in carcinoma of the stomach and breast, non-neoplastic gastric mucosa, and fibroadenoma of the breast. MoAb B72.3 was reactive with the cell membrane, rough endoplasmic reticulum (rER), Golgi complex, or secretory granules in tumor cells of gastric adenocarcinoma. In non-neoplastic gastric mucosa, mucous droplets of goblet cells were frequently reactive and rER in foveolar epithelia was occasionally reactive, but reactivity along cell membranes or in secretory granules was not observed. MoAb B72.3 was also reactive along the cell membranes of breast carcinomas, while fibroadenomas showed no reactivity. Our study has indicated that (a) TAG-72 may be synthesized in rER and Golgi complex and secreted in two ways--i.e., via secretory granules and mucous droplets, and (b) its location along the cell membrane and in secretory granules may be specific for carcinoma cells.