CHOLINERGIC MARKERS IN TRANSFORMED TROPHOBLAST CELLS - BEWO AND JAR CELLS

During the first trimester of pregnancy, the human placental trophobla st contains very low levels of choline acetyltransferase (ChA), a spec ific enzyme for synthesis of acetylcholine (ACh) and a reliable cholin ergic marker. There is a relationship between ChA levels and developme nt and maturation of syncytiotrophoblast during the first six months o f pregnancy, when ChA levels reach maximum. These observations suggest that ChA and its product, ACh, have significant roles during differen tiation of cytotrophoblast into syncytium. Therefore, we have measured ChA levels in malignant trophoblast cultures before and after differe ntiation. Two pure trophoblast cell lines (BeWo and JAr) are used in t hese studies. ChA in these cells was determined by a standard radiomet ric method in which C-14-acetyl groups were transferred from C-14-acet ylcoenzyme A to choline. Methotrexate (1 mu M) was used to differentia te the cells. The following results were obtained: a) Undifferentiated BeWo cells contained a ChA level of 311.0+/-8.3 pmoles ACh formed (M/-S.E., N=6)/mg protein/10 min. Differentiation decreased ChA level to 213.0+/-9.3 pmoles ACh/mg protein/10 min.; b) Undifferentiated JAr ce lls contained ChA levels of 279.0+/-15.0 ACh pmoles formed/mg protein/ 10 min. This decreased to 166.8+/-10.0 upon differentiation; c) Upon d ifferentiation, ChA levels decreased by 31.5-40.2% in BeWo and JAr cel l lines. In term human placenta, the ChA level falls by about 46.0-73% after syncytiotrophoblast is fully developed; d) Chorionic gonadotrop in (hCG), which is produced in cytotrophoblast, is a standard tumor ma rker for chorionic cancer. As the syncytiotrophoblast is formed, produ ction of hCG decreases. Similarly, production of hCG by BeWo and JAr c ells decreases upon their differentiation, and e) In hydatidiform mole , which can undergo malignant transformation into choriocarcinoma, the re were no significant levels of ChA. These observations suggest that ChA and ACh are necessary for development and maturation of syncytiotr ophoblast.