Alpha-fetoprotein triggers hepatoma cells escaping from immune surveillance through altering the expression of Fas/FasL and tumor necrosis factor related apoptosis-inducing ligand and its receptor of lymphocytes and liver cancer cells

Abstract

Aim: To investigate the mechanism of alpha-fetoprotein (AFP) in escaping from the host immune surveillance of hepatocellular carcinoma.

Methods: AFP purified from human umbilical blood was administrated into the cultured human lymphoma Jurkat T cell line or hepatoma cell line, Bel7402 in vitro. The expression of tumor necrosis factor related apoptosis-inducing ligand (TRAIL) and its receptor (TRAILR) mRNA were analyzed by Northern blot and Western blot was used to detect the expression of Fas and Fas ligand (FasL) protein.

Results: AFP (20 mg/L) could promote the expression of FasL and TRAIL, and inhibit the expression of Fas and TRAILR of Bel7402 cells. For Jurkat cell line, AFP could suppress the expression of FasL and TRAIL, and stimulate the expression of Fas and TRAILR. AFP also could synergize with Bel7402 cells to inhibit the expression of FasL protein and TRAIL mRNA in Jurkat cells. The monoclonal antibody against AFP (anti-AFP) could abolish these functions of AFP.

Conclusion: AFP is able to promote the expression of FasL and TRAIL in hepatoma cells and enhance the expression of Fas and TRAILR in lymphocytes. These could elicit the escape of hepatocellular carcinoma cells from the host's lymphocytes immune surveillance.

Figure 1

Influence of AFP (20 mg/L), anti-AFP (40 mg/L), AFP (20 mg/L) plus anti-AFP (40 mg/L) and HSA (20 mg/L) on the expression of Fas and FasL protein in Bel7402 cells and Jurkat cells. A, C: Western blot of Fas and FasL protein of Bel7402 cells or of Jurkat cells; B, D: Quantitative analysis of IOD of Fas/IOD of actin, the columns represent mean±SD.

Figure 2

Effect of AFP (20 mg/L), anti-AFP (40 mg/L) and AFP (20 mg/L) plus anti-AFP (40 mg/L) on the expression of Fas and FasL protein in Bel7402 cells or in Jurkat when the cells were cultured individually or co-cultured. A and C: Western blot analysis of Fas and FasL protein of Bel7402 cells or of Jurkat cells; B and D: Quantitative analysis IOD of Fas/IOD of actin, the columns represent mean±SD.

Figure 3

Effect of AFP (20 mg/L), anti-AFP (40 mg/L) and AFP (20 mg/L) plus anti-AFP (40 mg/L) on the TRAIL mRNA expression of Bel7402 cells and Jurkat cells were cultured individually or cultured together. A: Northern blot of TRAIL mRNA of Bel7402 cells and Jurkat cells; B: Quantitative analysis IOD of TRAIL/IOD of β-actin, the columns represent mean±SD.

Figure 4

Influence of AFP (20 mg/L), anti-AFP (40 mg/L) and AFP (20 mg/L) plus anti-AFP (40 mg/L) on the expression of TRAILR mRNA in Bel7402 cells and Jurkat cells were cultured individually or cultured together. A: Northern blot analysis of TRAILR mRNA of Bel7402 cells and Jurkat cells; B: Quantitative analysis IOD of TRAILR/IOD of β-actin, the columns represent mean±SD.