The observation of a strong correlation between COX2 and IL-10, IDO1, CXCL8, and CCL22 exclusively after BCG exposure (but not at baseline in unstimulated bladder tumor explants), and the elimination of the induction of these factors by blockers of PGE2 production or signaling helps to explain the role of PGE2 as a factor promoting the progression of BlCa and its resistance to BCG and other treatments observed in mouse models [15,41,42,43]. The gene discussed is IDO1; the disease is bladder transitional cell carcinoma.