Serum soluble interleukin-2 receptor and immunohistochemical staining of IL-2R/Tac antigen in gastric cancer

In the present study, we investigated the significance of serum soluble IL-2R as a tumor marker, and examined the existence and localization of positive cells for IL-2R/Tac antigen in gastric cancer tissues and its regional lymph nodes. Eighty-two patients with gastric cancer were included. Levels of serum soluble-IL-2R were measured by an enzyme-linked immunosorbent assay. In the tissues obtained from 19 cases, immunohistochemical staining was performed with the use of avidin-biotin-peroxidase complex technique, in which mouse anti-human interleukin-2 receptor antibody was used. The preoperative levels of serum soluble IL-2R in patients-with gastric cancer were significantly higher than those of normal controls (p<0.001). The levels of serum soluble IL-2R in cases with metastatic lymph nodes were also significantly higher than those without metastatic lymph nodes (p<0.05). Concerning the tumor markers, there were significant differences of serum soluble IL-2R levels between those who were positive and those negative for CA19-9, CEA, alpha-FTP, and IAP. In the immunohistochemical staining of IL-2R, 13 of 19 cases (68.4%) showed IL-2R positive cells in the gastric cancer tissues. In regard to the metastatic lymph nodes, 3 of 5 cases (60.0%) showed IL-2R positive cells. On the other hand, IL-2R positive cells were not recognized in normal gastric tissues and non-metastatic lymph nodes. These results may suggest that activated T-lymphocytes infiltrating into the cancer tissues play an antitumor role and release a large amount of alpha-chain of IL-2R, resulting in the high levels of serum soluble IL-2R in patients with gastric cancer.