CXXC4 and gastric cancer: To further confirm that EV-delivered miR-675-3p affected the expression of PD-L1 through CXXC4/MAPK, CXXC4 was overexpressed simultaneously in GC cells treated with EVs, causing increased CXXC4 expression and reduced phosphorylated ERK content and PD-L1 expression (Figures 4E and 4F, p < 0.05).