CD226 and gastric cancer: In the present study, we characterized the surface receptor phenotypes of circulating NK cells in human GC and found that the proportion of peripheral blood NK cells which expressed the activating receptors NKp30, NKp46, NKG2D, and DNAM-1 was significantly decreased in GC patients compared to healthy donors, and that this effect could be mediated in vitro by TGF-β1.