Immunohistochemical analysis of Fas ligand expression in sarcomas.: Sarcomas express high level of FasL in vivo

Fas ligand (FasL) and its receptor, Fas, play a key role in the regulation of apoptosis within the immune system. Several prior experimental studies of Fas ligand expression in tumors have suggested a mechanism that enables tumors to evade immune destruction by inducing apoptosis in activated lymphocytes near the tumor cells. Many types of carcinomas have been shown to express Fast, but at present nothing is known about the range of sarcomas capable of expressing Fast in vivo. The aim of this study was to determine the in vivo patterns of Fast expression in human sarcomas. Archival paraffin-embedded tissues of 57 sarcomas and 30 carcinomas were analyzed by immunohistochemistry for the expression of Fast. Fast immunoreactivity was seen in 39 of 57 (68%) sarcomas, including 10 of 10 rhabdomyosarcomas, 5 of 5 malignant schwannomas, 2 of 2 Ewing's sarcomas, 8 of 11 malignant fibrous histiocytomas, 4 of 5 angiosarcomas, 2 of 5 synovial sarcomas, 2 of 5 liposarcomas, 3 of 5 leiomyosarcomas, 2 of 6 osteosarcomas, and 1 of 3 chondrosarcomas. All carcinomas tested (10 gastric adenocarcinomas, 10 hepatocellular carcinomas, and 10 renal cell carcinomas) were positive for Fast. These results demonstrate that Fast expression in sarcomas, although less frequent than in carcinomas, is widespread among the sarcoma types, and suggest that Fast might contribute to the immune escape of sarcomas through killing Pas-bearing lymphocytes.