PTGES and neoplasm: Previous studies indicated that tumor cells were able to positively regulate PD-L1 expression in TAMs through several signaling pathways, such as the cyclooxygenase 2/microsomal prostaglandin E synthase 1/prostaglandin E synthase 2 (COX2/mPGES1/PGE2) (169), NF-κB (170), and STAT3 (171).