Expression of Fas antigen (CD95) in peripheral blood lymphocytes and in liver‐infiltrating, cytotoxic lymphocytes in patients with hepatocellular carcinoma

BACKGROUND Fas‐expressing cytotoxic T lymphocytes (CTLs) are important antitumor immune effector cells in patients with hepatocellular carcinoma (HCC). The role of transforming growth factor β 1 (TGF‐β1) in modulating the expression of Fas by CTLs is not known in HCC. The objectives of this study were to characterize the expression of Fas by CTLs and natural killer (NK) cells among peripheral blood lymphocytes (PBLs) and tumor‐infiltrating lymphocytes (TILs) in patients with HCC and to correlate the association, if any, with serum TGF‐β1 levels. METHODS PBLs from 18 patients with HCC and TILs from 5 HCC liver specimens were isolated, and Fas expression was analyzed by three‐color flow cytometry. The results were compared with results from normal control volunteers (n = 19 individuals). Serum TGF‐β1 levels in patients with HCC were measured by enzyme‐linked immunosorbent assay. RESULTS The median percentage of Fas expression by CD3 positive T cells was significantly higher in patients with HCC compared with normal controls (54.37% vs. 32.03%, respectively; P = 0.0036), and this was attributable solely to Fas expression by CD4 positive PBLs (54.46% vs. 34.90%, respectively; P = 0.0234). In contrast, Fas expression was significantly higher in all the subtypes of TILs (CD3 positive, CD4 positive, CD8 positive, NK cells, and natural T cells) compared with controls (all P values were < 0.001). Tumor size was inversely proportional to the TGF‐β1 levels (correlation coefficient [ r ] = −0.725; P < 0.0001), which were correlated inversely with Fas expression by CD4 positive PBLs ( r = −0.516; P = 0.01). CONCLUSIONS In patients with HCC, TILs exhibit significantly increased expression of Fas compared with PBLs that may enhance their susceptibility to apoptotic mechanisms. Larger tumors were associated with lower serum TGFβ1 levels, and this was correlated with greater Fas expression by CD4 positive PBLs. Cancer 2001;92:2136–41. © 2001 American Cancer Society.