Chemical inhibition of EP4 by the new EP4 antagonist, TP‐16, significantly decreased the proportion of M-MDSCs, though no significant difference was observed in the proportion of PMN‐MDSCs and decreased the expression of MDSC markers (for both M-MDSCs and PMN‐MDSCs), such as Arg‐1, Ptgs2, IL‐4ra, Ido1, and IL‐10, thus enhancing cytotoxic T‐cell activation and increasing responsiveness to anti-PD-1 therapy in a spontaneous colorectal cancer mouse model (96). The gene discussed is PTGER4; the disease is colorectal cancer.