Objective: To study the expression of Fas ligand on peritumoral lymphocytes and its relation to the apoptosis of colorectal carcinoma.
Methods: The expression of Fas protein and FasL in 86 cases of colorectal carcinomas and normal colorectal tissues at the margins of resection was studied immunohistochemically. Apoptosis of cancer cells was evaluated with TUNEL method, which was then correlated with FasL expression on peritumoral lymphocytes.
Results: 53 (61.6%) of 86 cases of colorectal carcinoma were stained positively with Fas monoclonal antibodies, but such stain was net found in the normal colorectal tissues at the margin of resection. Peritumoral lymphocytes of 69 cases (80.2%) were stained positively with FasL antibodies. The intensity of FasL staining on peritumoral lymphocytes was positively correlated with the apoptotic index of cancer cells in the Fas positive colorectal carcinomas (P < 0.01), but not in the Fas negative group.
Conclusion: FasL expressed on the surfaces of peritumoral lymphocytes mediates apoptosis of colorectal cancer cells by acting on its receptor, Fas protein on cancer cells. The elevation of Fas expression on cancer cells and application of specific Fas antibodies may serve as new approaches to treat colorectal carcinoma.