Fas and Fas ligand: strong co-expression in human hepatocytes surrounding hepatocellular carcinoma; can cancer induce suicide in peritumoural cells?

Fas (Apo-1, CD95), a member of the nerve growth factor/tumour necrosis fact or receptor superfamily, mediates apoptosis in response to agonistic antibo dies or pas ligand (Fas-L) binding. Fas has been shown to be present on hep atocyte membranes in normal liver and in chronic hepatitis C. At the presen t time, very limited data are available on the expression of Fas-L. This pa per describes a study of 20 cases of active chronic hepatitis of different aetiologies, 20 hepatocellular carcinomas (HCCs) and the adjacent non-tumou ral liver parenchyma, and five normal livers. The immunohistochemical expre ssion of Fas and Fas-L was determined using specific monoclonal antibodies. In normal liver, Fas was faintly expressed on membranes of hepatocytes and bile duct cells, while Fas-L was negative. In active chronic hepatitis, pa s expression in hepatocytes was enhanced, resulting in a diffuse honeycomb pattern. Fas-L, showed cytoplasmic positivity in hepatocytes in areas of in terface hepatitis. Strong expression of Fas as well as Fas-L in the hepatoc ytes immediately adjacent to HCC was a constant finding. Within the HCCs, F as-L expression was variable, but present only in a minority of cells. Fas varied from a diffuse honeycomb pattern to focal positivity in occasional c ells. There was no correlation between Fas and Fas-L expression in the tumo urs. In conclusion, hepatocytes can co-express Fas and Fast in areas of int erface hepatitis and adjacent to HCC, suggesting that they have the ability to induce apoptosis in an autocrine or paracrine way. Within the tumour, t he Fas-Fas-L apoptosis pathway seems to be little involved. Copyright (C) 2 000 John Wiley & Sons, Ltd.