Differential expression of trophoblast-specific membrane antigens by normal and abnormal human placentae and by neoplasms of trophoblastic and non-trophoblastic origin.

Using a specific antiserum to human syncytial trophoblast plasma membrane (TrPM), we have investigated the expression of these antigens on a variety of trophoblastic and non-trophoblastic tissues by a standard peroxidase/anti-peroxidase staining method. Normal placenta (first-trimester as well as full-term), placenta from tubal pregnancy and placenta accreta were all found to express TrPM antigens. However, malignant change in trophoblast neoplasms appeared to by accompanied by a loss of these antigens, with 7 out of 10 specimens of hydatidiform mole staining positively while 3 specimens of invasive mole and 7 specimens of choriocarcinoma were all negative. In contrast, a number of malignant tumours of non-trophoblastic origin such as carcinomas of the colon, cervix, bladder and hepatomas were found to express TrPM antigens. The possible significance of the reversal to a trophoblast phenotype by malignant neoplasms of non-trophoblastic origin is discussed.