PTGS2 and cancer: Given that COX-2 overexpression is a common feature of various cancer types, that COX-2 inhibitors are already widely used in clinical practice with well-known and manageable side effects profiles, and that COX-2 activity is involved in malignant phenotype independent of immune suppression, we suggest that COX-2 inhibitors are broadly applicable, safe, and effective drugs for ICI combination therapy.