CTCF and gastric cancer: Gastric cancer MSCs upregulate the levels of PD-L1 bound to the transcription factor CCCTC binding factor (CTCF), enhance the CSC-likeproperties of GC cells, and lead to tumorigenesis. In vivo, PD-L1-positive GC cells have greater stemness potential and tumorigenicity than PD-L1-negative GC cells. GC cells are heterogeneous, and PD-L1s in GC cells have different reactivities to GCMSCs.