Characterisation of the differential expression of marker antigens by normal and malignant endometrial epithelium.

In order to examine the production of marker proteins, a reproducible method has been established for culturing purified epithelial cells from normal and malignant endometrium. We have examined the differential expression of secretory proteins using immunohistochemistry in frozen tissue sections, immunocytochemistry in cell cultures derived from the same specimens and protein assays on the culture supernatants. Placental protein 14 (PP14) was produced by normal premenopausal epithelium but not by the post-menopausal or malignant endometrial epithelium. In contrast, placental alkaline phosphatase (PLAP) was produced by endometrial cancers and the endometrial adenocarcinoma-derived cell line Ishikawa, but not by the normal endometrial epithelium. Other markers such as CA-125, which was produced by both normal and malignant endometrium but not by the cell line, and human chorionic gonadotrophin (beta-hCG), which was produced by Ishikawa cells but not by any of the fresh tissues, were less cancer specific. Placental alkaline phosphatase is a direct product of endometrial cancers that can be readily assayed in serum using this two-site assay to test its clinical usefulness in monitoring patients at risk for endometrial cancer.