Figure 1.

Roles of natural killer cells in the esophageal cancer tumor microenvironment. (A) Natural killer (NK) cells exert essential anti-tumor functions through degranulation, cytokine release, and activated receptor expression, directly killing esophageal tumor cells in the absence of antigen recognition in the tumor microenvironment (TME). (B) Cancer cells can escape from NK cell immune surveillance in the TME through the PD-1/PD-L1 pathway and the competitive combination of activated NKp30 receptor, expressed on NK cells, by releasing soluble B7-H6 (indicated as sB7-H6). Otherwise, large amounts of H₂O₂ produced by tumor infiltrated macrophages in the TME are prone to induce CD56^dim NK cell apoptosis, while CD56^dim NK cells can also transform to a CD56^bright phenotype during tumor development, as well as decreasing in number and becoming dysfunctional.