CCR8 and neoplasm: The second largest CD4+ T cell cluster corresponded to TREGS (cluster 4), with high expression of TREG marker genes (FOXP3, IL2RA/CD25, CTLA4, TIGIT), but also the expression of activation genes (TNFRSF4/OX40, TNFRSF18/GITR) and CCR8, which has been proposed as a marker of clonally expanded TREGS that recognize tumor antigens (56–58).