Upregulation of T-cell Immunoglobulin and Mucin-Domain Containing-3 (Tim-3) in Monocytes/Macrophages Associates with Gastric Cancer Progression

T-cell immunoglobulin and mucin-domain containing-3 (Tim-3) is an important immune regulatory molecule in cancer immune system. However, expression and function of Tim-3 in monocytes/macrophages in cancer progression mainly remain unclear. In this study, we analyzed Tim-3 levels in peripheral blood mononuclear cells (PBMCs) from 62 gastric cancer patients and 45 healthy controls using flow cytometry and then associated Tim-3 levels with clinical pathological data from patients. We found Tim-3 level was significantly upregulated in monocytes from gastric cancer patients compared with those from healthy controls, and that upregulated Tim-3 levels associated with depth of tumor invasion and tumor lymph node metastasis and advanced clinical stages of gastric cancer patients. Furthermore, tumor-bearing mouse experiments revealed that Tim-3 level on monocytes/macrophages associated with xenograft formation and growth. In addition, culture of monocytes from healthy controls with gastric cancer cell-conditioned medium upregulated Tim-3 expression, but IL-10, TNF-α, IFN-γ, or GM-CSF treatment or T-bet, Eomes, and T-bet/Eomes double gene knockout did not affect Tim-3 levels in blood monocytes/macrophages from human or mouse, respectively. Gal-9/Tim-3 signal was able to significantly stimulate monocyte to secrete IL-6, IL-8, and IL-10, but not IL-1β, IL-12p70, or TNF-α in presence of LPS. In conclusion, our study demonstrated that Tim-3 expressed by monocyte/macrophages might be an important mechanism in gastric cancer progression.