Protein-Bound Polysaccharide K Partially Prevents Apoptosis of Circulating T Cells Induced by Anti-Cancer Drug S-1 in Patients with Gastric Cancer

Abstract

Background and Methods:It has been shown that T-cell dysfunction, including apoptosis of peripheral blood T cells, commonly occurs in patients receiving chemotherapy. In order to evaluate whether concomitant administration of the oral biological response modifier protein-bound polysaccharide K (PSK) could induce anti-apoptotic effects in patients treated with the anti-cancer drug, S-1, peripheral blood T cells were analyzed for induction of apoptosis, caspase-3 activities and expression of proapoptotic protein Bax and anti-apoptotic protein Bcl-2 in patients with curatively resected stage III gastric cancer, who were randomly assigned to postoperative adjuvant therapy with S-1 alone (n = 10) or S-1 combined with PSK (n = 10). Results: T-cell apoptosis 5 weeks after adjuvant therapy was significantly higher in the S-1 group (24.1 ± 5.0%) than in the S-1 + PSK group (19.1 ± 3.9%). S-1 induced T-cell apoptosis and concomitantly elevated caspase-3 activities and Bax expression in peripheral blood T cells. In addition, PSK partially prevented the T-cell apoptosis induced by S-1. Conclusion:PSK could partially prevent the T-cell apoptosis induced by S-1.