Lack of evidence for expression of Fas ligand in Fas-bearing tumors.

Interaction of Fas and its ligand plays an important role in the cell death by means of apoptosis in a variety of cell types. We recently demonstrated the frequent expression of Fas in female reproductive tract tumors, which prompted us to examine the local production of Fas ligand by the Fas-bearing tumors. Human endometrial and ovarian carcinomas, surgically removed, were studied. No expression of Fas ligand messenger ribonucleic acid (mRNA) as assessed by reverse transcription-polymerase chain reaction using oligonucleotide primers according to published sequences were observed; Fas ligand mRNA was detected in lymphocytes. Immunoblotting of membrane proteins with the specific antibody failed to demonstrate any substantial level of immunoreactive Fas ligand in these tumors. The results for both mRNA expression and immunoreactivity suggest that human ovarian and endometrial carcinomas lack the Fas ligand. The demonstration of absence of Fas ligand expression raises the possibility that the stimulated proliferation of the Fas ligand-absent tumors may occurs by release of Fas-Fas ligand system-associated apoptosis.