Elevated caspase-3 activity in peripheral blood T cells coexists with increased degree of T-cell apoptosis and down-regulation of TCR zeta molecules in patients with gastric cancer.

To evaluate the mechanisms of T-cell dysfunction in patients with gastric cancer, we investigated the caspase activity of T cells, the induction of spontaneous T-cell apoptosis, the expression of T-cell receptor (TCR) zeta molecules, and the ability of T cells to produce cytokines in peripheral blood lymphocytes from patients (n = 22) and healthy controls (n = 14). The caspase-3 activity of T cells was studied as the protease activity of caspase-3 using the cell-permeable substrate of PhiPhiLux G1D2. Flow cytometric analysis was performed with triple staining by annexin V-FITC, propidium iodide, and CD3-R-phycoerythrin-Cy5 for the detection of T-cell apoptosis and with intracellular staining using permeabilized cells for the expression of TCR-zeta molecules. IFN-gamma and tumor necrosis factor alpha production from T cells was evaluated in response to anti-CD3 stimulation. Caspase-3 activity of peripheral blood T cells from patients with advanced disease was significantly increased compared with that from controls [15.5 +/- 3.6 mean fluorescence intensity (MFI) versus 11.5 +/- 3.3 MFI; P = 0.0068]. Parallel to this, the apoptosis of peripheral blood T cells from patients with advanced disease was significantly higher than for those from controls (16.5 +/- 15.5% versus 4.8 +/- 2.7%; P = 0.010). Furthermore, the expression of TCR-zeta molecules in patients with advanced disease was significantly decreased in comparison with that of the controls (41.0 +/- 13.9 MFI versus 56.7 +/- 16.3 MFI; P = 0.014), and this decreased expression coexisted with impaired IFN-gamma (42.4 +/- 43.2 pg/ml versus 1,757.4 +/- 2449.0 pg/ml; P = 0.031) and tumor necrosis factor alpha (682.6 +/- 519.3 pg/ml versus 1,686.0 +/- 1,533.7 pg/ml; P = 0.041) production of T cells. Thus, peripheral blood T cells from gastric cancer patients simultaneously exhibit an elevated caspase-3 activity, an increased degree of T-cell apoptosis, a down-regulation of TCR-zeta molecules, and impaired cytokine production. These observations suggest that induction of T-cell apoptosis coexisting with a down-regulation of TCR-zeta molecules may be responsible for T-cell dysfunction in patients with gastric cancer.