ENDOGLIN, A COMPONENT OF THE TGF-BETA RECEPTOR SYSTEM, IS A DIFFERENTIATION MARKER OF HUMAN CHORIOCARCINOMA CELLS

Endoglin is an integral membrane glycoprotein that binds transforming growth factor-beta 1 (TGF-beta 1) with high affinity and it is strongl y expressed on syncytiotrophoblasts throughout pregnancy. Here, we des cribe the expression of endoglin by the choriocarcinoma cell line JAR as evidenced by flow cytometry, immunoprecipitation, Western blot and reverse transcriptase polymerase chain reaction analyses. Crosslinking experiments of [I-125]-labeled TGF-beta 1 to JAR cells indicated that endoglin expressed at the surface of these cells binds TGF-beta. Furt hermore, staining of human choriocarcinoma tissue sections with a poly clonal antibody to endoglin demonstrated a high expression of endoglin in syncytiotrophoblast-like areas, as opposed to a negative staining of cytotrophoblast-like cells. This pattern of endoglin expression was confirmed by experiments with methotrexate, an inducer of giant, mult inucleated, non-proliferative cells, morphologically indistinguishable from the naturally occurring syncytiotrophoblasts. Thus, treatment of the JAR and JEG-3 choriocarcinoma cell lines with methotrexate led to an increase in endoglin expression, as demonstrated by Western and No rthern blot analyses. Taken together, our results suggest that endogli n, in addition to being involved in placental development, may also be a cellular differentiation marker. (C) 1998 Wiley-Liss, Inc.