IDO1 and neoplasm: Interestingly, BCG treatment was also associated with elevation of additional COX2/PGE2-dependent suppressive factors, such as indoleamine-2,3-dioxygenase 1 (IDO1) and IL10 [51,111,112], which is consistent with our earlier observations that COX2 is critical for the induction, persistence, and suppressive activity of tumor-associated MDSCs [102,104].