Expression of Fas ligand is an early event in colorectal carcinogenesis

Background and Objectives: Fas ligand (FasL) is expressed in many cancers a nd plays an important role in establishing immunologically privileged envir onments that allow tumors to escape the host's immune surveillance. We inve stigate the expression of FasL in human colorectal cancer and colorectal ad enoma and elucidate the relationship between FasL expression and the clinic opathological characteristics of colorectal cancers. Methods: We examined 214 colorectal cancer specimens and 83 colorectal aden oma specimens. Expression of FasL was determined by immunohistochemical sta ining using a specific monoclonal antibody. We analyzed the relationship be tween the results of FasL expression and clinicopathological data statistic ally. Results: FasL expression was detected in 173 (80.8%) of 214 colorectal carc inomas and 34 (40.9%) of 83 colorectal adenomas. The status of FasL express ion in colorectal carcinoma was independent of clinicopathological features including tumor stage, histologic grade. lymphatic invasion, venous invasi on, lymph node metastasis, liver metastasis, and Dukes stage. In colorectal adenoma, FasL expression was more frequently observed in high-grade atypia than in low-grade atypia (P = 0.05). Conclusions: FasL expression is commonly observed not only in cancer but al so in highly dysplastic tissue. These observations suggest that FasL expres sion may be an important event in the transformation process leading to ade nocarcinoma. J, Surg. Oncol. 2001:76:63-68. (C) 2001 Wiley-Liss. Inc.