Epithelial cells from normal human endometrium express a tumor-associated glycoprotein (TAG-72) epitope in vitro

Monoclonal antibody B72.3 identifies a tumor-associated glycoprotein (TAG-72) epitope derived from a human breast carcinoma metastasis. Recently, expression of this epitope was noted in normal endometrium during the secretory, but not proliferative, menstrual interval. In light of known hormonal control of normal endometrial growth and differentiation, we investigated in vitro expression of TAG-72 epitope in purified endometrial epithelium cultured under serum-free conditions on Matrigel biomatrix. Cells from secretory endometrium exhibited homogeneous tumor-associated glycoprotein 72 epitope expression. Unexpectedly, epithelium from the proliferative interval developed expression after 5 to 6 days of culture. Epithelial cells from both intervals maintained expression over 12 days of culture without exogenous estradiol and progesterone. Spontaneous, uniform expression of tumor-associated glycoprotein 72 epitope by normal endometrial epithelial cells in vitro is in marked contrast to the cyclic, heterogeneous expression observed in vivo. Such expression also differs from published in vitro observations of cancer cell lines that express this epitope.