Mouse bone marrow cells, mostly macrophages and myeloid-derived suppressor cells, cocultured with bladder tumor cells strongly expressed PD-L1, as well as microsomal PGE2 synthase 1 (mPGES1), cyclooxygenase 2 (COX2), and prostaglandin E2 (PGE2), while inhibition of mPGES1 or COX2 led to decreased production of PGE2 and expression of PD-L1. The gene discussed is PTGS2; the disease is urinary bladder neoplasm.