Expression of FasL in squamous cell carcinomas of the cervix and cervical intraepithelial neoplasia and its role in tumor escape mechanism.
BACKGROUND
To date, several mechanisms have been described by which malignant cells escape from the immune system. One of these is through the expression of FasL. The authors hypothesized that the Fas/FasL interaction enables cervical carcinoma cells to induce apoptosis of the cells of the immune system and thereby escape from them.


METHODS
The authors tested the expression of FASL on the surface of cervical carcinoma tissues. Next, they stained the same cervical tissues with anti-human leukocyte common antigen and TUNEL to identify apoptotic cells. An in vitro functional assay was then done to test if the FASL expressed on the surface of cervical carcinoma cell lines was or was not responsible for inducing apoptosis in T-cells. Finally, they compared the expression of FASL on normal and dysplastic cervical tissues.


RESULTS
Ninety-four percent of the cervical carcinoma tissues the authors tested expressed FasL and the majority of the apoptotic cells in the specimens were leukocytes with very few tumor cells. In the in vitro functional assay, only the Fasl expressing cell line and not the Fasl negative cell line was able to induce apoptosis of the Fas-expressing Jurkat cells. On examining the normal cervical tissues, the authors found that the expression of Fasl was confined to the basal cell layer with loss of expression observed in the suprabasal layers, which made it an immune privileged site. Conversely, there was persistent expression of FasL in the dysplastic layers in cervical dysplasia and squamous cell carcinoma specimens.


CONCLUSIONS
The findings of the current study support the authors' hypothesis that persistent expression of FasL plays a role in the ability of cervical carcinoma cells to escape from the immune system.
Ibrahim
Ramy
R
Cancer Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20889, USA.
Frederickson
Helen
H
Parr
Allyson
A
Ward
Yvona
Y
Moncur
Joel
J
Khleif
Samir N
SN
D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000276:immunology* / Q000503:physiopathology*; D002584:Cervix Uteri / Q000502:physiology; D053222:Fas Ligand Protein; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D007962:Leukocytes; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured; D019139:Tumor Escape; D048069:Tumor Necrosis Factors / Q000096:biosynthesis*; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000276:immunology* / Q000503:physiopathology*; D002578:Uterine Cervical Dysplasia / Q000235:genetics / Q000276:immunology* / Q000503:physiopathology*
C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D048069:Tumor Necrosis Factors