CD44 and gastric cancer: The correlation analysis between TM4SF18 and checkpoint gene expression showed that TNFRSF9, CD44, CD86, TNFSF15, CD40, TNFRSF4, VSIR, TNFESF8, PDCD1LG2, TNFSF14, CD80, CD276, HAVCR2, CD28, and CD48 in GC were highly correlated in expression (Fig. 8B).