Frequent loss of Fas expression and function in human lung tumours with overexpression of FasL in small cell lung carcinoma.

Fas (CD95) and its ligand FasL signal apoptosis and are involved in tissue homeostasis and the elimination of target cells by cytotoxic T cells. Corruption of this signalling pathway in tumour cells, for example by reduced Fas expression or increased FasL expression, can participate in tumour development and immune escape. The present study has analysed Fas/FasL expression and Fas death signalling function in vivo in lung tumour tissues [57 non-small cell lung carcinomas and 64 neuroendocrine lung tumours including small cell lung carcinoma (SCLC)] in comparison with normal lung tissue, and in vitro in neuroendocrine tumour cell lines in comparison with normal human bronchial epithelial cells. The Fas expression score was markedly decreased compared with normal lung tissue in 90% of the 121 lung tumours and was completely lost in 24%. The Fas staining pattern suggested cytoplasmic Fas expression in tumours, whereas membrane expression was observed in normal lung tissue. Loss of Fas at the cell surface was also shown in vitro by FACS analysis of neuroendocrine tumour cell lines and was concomitant with the resistance of tumour cells to FasL-mediated apoptosis according to in vitro cell viability. The lack of cell surface Fas expression in tumour cell lines resulted from the lack of intracellular Fas protein due to impaired Fas gene transcription. The FasL expression score was also decreased in most non-small cell lung carcinomas compared with normal bronchial cells, whereas 91% of SCLCs had higher expression than normal cells. FasL overexpression was related to advanced tumour stage as well as to a Fas/FasL ratio less than 1. It is concluded that a marked decrease in Fas expression may be part of lung tumourigenesis allowing tumour cells to escape from apoptosis. FasL overexpression in the context of Fas down-regulation in SCLC predicts the ability of SCLC cells to induce paracrine killing of Fas-expressing cytotoxic T cells. In lung tumours, Fas restoration may represent a key, although not unique, step in therapeutic strategies to reconstitute the ability of tumour cells to undergo apoptosis.

Viard-Leveugle I ，Veyrenc S ，French LE ，Brambilla C ，Brambilla E ... -  《JOURNAL OF PATHOLOGY》

Fas ligand is expressed in normal breast epithelial cells and is frequently up-regulated in breast cancer.

Fas (CD95/Apo-1) is a cell membrane receptor that upon binding by its ligand (FasL), triggers a signal resulting in apoptotic cell death. Fas is produced by breast epithelial cells, but its contribution to breast tissue homeostasis is unknown. This study investigated whether FasL is synthesized in the breast. By reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunohistochemistry, FasL expression was analysed in normal and malignant human breast epithelial cell lines, normal breast tissue, benign breast disease (fibrocystic changes, fibroadenoma), and breast cancer (ductal carcinoma in situ; invasive ductal, lobular, mucinous and medullary carcinomas). The results demonstrate expression of FasL by normal breast epithelial cells and show a marked increase of FasL protein in the majority of breast carcinomas, compared with normal breast tissue and benign breast disease. By western blot analysis, soluble FasL was detected in culture supernatants of one of three normal breast epithelial cell lines and in all four breast cancer cell lines tested. The expression of Fas protein was more heterogeneous in benign and malignant breast tissue, with expression levels ranging from weak to strong, but breast cancer cells frequently exhibited a weaker Fas expression than surrounding residual normal breast epithelial cells. In vitro, two out of three normal breast epithelial cell lines were sensitive to cell death induction by an agonistic anti-Fas antibody. Co-treatment with cycloheximide, an inhibitor of protein translation, rendered the resistant cell line sensitive. In contrast, two out of four breast cancer cell lines were resistant to the anti-Fas antibody and this resistance could not be reversed by cycloheximide. These results suggest that increased expression of FasL may confer an advantage on breast cancer cells, possibly by eliminating tumour-infiltrating immune cells, and/or by facilitating tissue destruction during invasion.

Müllauer L ，Mosberger I ，Grusch M ，Rudas M ，Chott A ... -  《JOURNAL OF PATHOLOGY》

Increased Fas ligand expression by T cells and tumour cells in the progression of actinic keratosis to squamous cell carcinoma.

Satchell AC ，Barnetson RS ，Halliday GM 《BRITISH JOURNAL OF DERMATOLOGY》

In vivo expression of soluble Fas and FAP-1: possible mechanisms of Fas resistance in human hepatoblastomas.

Many tumour cells express both Fas and its ligand (FasL) on their surface and it has remained a mystery why such cells do not simply kill themselves. It remains to be determined whether Fas and FasL are expressed in human hepatoblastomas and if so, what is responsible for the possible Fas resistance of these tumours. In this study, the expression of Fas and FasL was examined in 23 cases of human hepatoblastoma by immunohistochemical staining. To elucidate possible Fas resistance in hepatoblastomas, Fas-resistance pathways including the expression of bcl-2 and Fas-associated phosphatase-1 (FAP-1), and the expression of soluble Fas (sFas) mRNA, were analysed by immunohistochemistry and in situ reverse transcription-polymerase chain reaction (in situ RT-PCR). Fas gene mutation in the death domain was also examined. Fas and FasL were expressed in all hepatoblastomas analysed. Twenty (87 per cent) and 18 (78 per cent) cases of hepatoblastoma were positive for sFas mRNA and FAP-1, respectively, but none of the hepatoblastomas expressed bcl-2. Mutation in the death domain of the Fas gene was not found in hepatoblastomas. Taken together, these findings demonstrated that Fas, a death receptor, and its ligand are co-expressed in hepatoblastomas in vivo, but some inhibitors of Fas-mediated apoptosis are also expressed in these tumours. These results suggest that it is probably due to the action of inhibitory molecules of the Fas pathway that the tumour cells of hepatoblastomas do not kill themselves in an autocrine-driven cycle and that in this manner hepatoblastomas avoid apoptosis.

Lee SH ，Shin MS ，Lee JY ，Park WS ，Kim SY ，Jang JJ ，Dong SM ，Na EY ，Kim CS ，Kim SH ，Yoo NJ ... -  《JOURNAL OF PATHOLOGY》

Up-regulation of Fas (APO-1/CD95) ligand and down-regulation of Fas expression in human esophageal cancer.

Gratas C ，Tohma Y ，Barnas C ，Taniere P ，Hainaut P ，Ohgaki H ... -  《-》