Co-expression of Fas (APO-1, CD95)/Fas ligand by BeWo and NJG choriocarcinoma cell lines.
OBJECTIVE
Fas (CD95) is a transmembrane protein of the tumor necrosis factor receptor superfamily that induces apoptosis in susceptible cells on crosslinking by its ligand (FasL). The Fas loss of function and concurrent expression of its ligand (FasL) have been associated with malignant phenotype. In this study, we sought to investigate the hitherto undescribed expression of Fas and FasL on the immortalized human choriocarcinoma cell lines BeWo and NJG.


METHODS
Receptor and ligand expression was demonstrated using specific antibodies and multiple techniques including immunocytochemistry, confocal immunofluorescence microscopy, flow cytometry, immunoblots, and reverse transcription polymerase chain reaction (RT-PCR).


RESULTS
Data from this study indicate that human choriocarcinoma cell subtypes co-express both Fas and FasL. A specific cytoplasmic and membranous pattern of immunoreactivity was noted that was further confirmed at mRNA transcripts by RT-PCR. In addition, we provide evidence using flow cytometry that the Fas receptors are downregulated. The mean fluorescence intensities for NJG and BeWo were 1.47 +/- 0.5 and 1.59 +/- 0.4, while that for Fas-positive Jurkat cells was 25.6 +/- 3.1.


CONCLUSIONS
To our knowledge, this is the first report on the identification and constitutive co-expression of Fas and FasL in BeWo and NJG choriocarcinoma cells. Choriocarcinoma cells evade immune attack by downregulating the Fas receptor and by killing lymphocytes through expression of FasL. Taken together, our investigations suggest that the Fas/FasL system may represent a mechanism by which malignant trophoblasts become resistant to apoptosis, escape immune surveillance, and metastasize.
Rajashekhar
G
G
Department of Obstetrics and Gynecology, National University Hospital, National University of Singapore, Lower Kent Ridge Road, 119074, Singapore. abgannam@nus.edu.sg
Loganath
A
A
Roy
A C
AC
Mongelli
J M
JM
D002822:Choriocarcinoma / Q000276:immunology* / Q000378:metabolism; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000378:metabolism; D053222:Fas Ligand Protein; D005260:Female; D005434:Flow Cytometry; D031901:Gestational Trophoblastic Disease / Q000276:immunology* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D008856:Microscopy, Fluorescence; D011247:Pregnancy; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000276:immunology* / Q000378:metabolism; D019014:fas Receptor / Q000096:biosynthesis*
D018997:Chorionic Gonadotropin, beta Subunit, Human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D019014:fas Receptor