MPO and neoplasm: Nevertheless, it is noteworthy that untreated PDAC tumor is likely to create an immunosuppressive TME enriched with endogenously produced AHR ligands, as human pancreatic adenocarcinoma expresses IL-4-induced-1, an enzyme that has the ability to convert tryptophan to indole-3-pyruvic acid (I3P) and its downstream products, including 3-IAA, indole-3-lactic acid, indole-3-aldehyde (I3A), and kynurenic acid.4 Thus, FOLFIRINOX may enable neutrophil MPO to oxidize either gut microbiota- or cancer cell-derived 3-IAA to toxic products.