Yonago Acta medica 2011;54:001010
Increased B7-H1 and B7-H4 Expressions on Circulating Monocytes and Tumor-Associated Macrophages are Involved in Immune Evasion in Patients with Gastric Cancer
Tomoyuki Matsunaga, Hiroaki Saito and Masahide Ikeguchi
Division of Surgical Oncology, Department of Surgery, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan
Expression of the costimulatory molecule B7-H4, a member of the inhibitory B7 family, has been reported to be upregulated on tumor-associated macrophages, and this overexpression may be involved in immune evasion in cancer patients. The present study was designed to investigate B7-H4 expression on monocytes/macrophages and its relationship with immune evasion in gastric cancer patients. B7-H4 expression on circulating monocytes and tumor-associated macrophages was evaluated by multicolor flow cytometry. Carboxyfluorescein succinimidyl ester proliferation assays and quantitative interferon-gamma enzyme-linked immunosorbent assays were carried out to determine the inhibitory effect of B7-H4+ monocytes on CD4+ T cells. B7-H4 expression on circulating monocytes was upregulated and these B7-H4+ monocytes showed immunosuppressive properties. B7-H4 expression was closely related to the depth of invasion, as well as the presence of lymphatic and venous invasion. There were significant correlations between B7-H4 expression and B7-H1 or HLA-DR expression on monocytes/macrophages in gastric cancer patients. B7-H4 expression was remarkably upregulated in gastric cancer tissues compared with peripheral blood samples. Complete surgical removal of the tumor decreased B7-H4 expression on circulating monocytes from gastric cancer patients. Cocultures of gastric cancer cell lines and monocytes led to upregulation of B7-H4 expression on monocytes. Increased B7-H4 expression on circulating monocytes and tumor-associated macrophages may be one of the key mechanisms responsible for immune evasion by tumors in gastric cancer.
Key words: B7-H1; B7-H4; gastric cancer; macrophage; monocyte