AHR and pancreatic ductal adenocarcinoma: Pancreatic ductal adenocarcinoma (PDAC) similarly shows dense TAM infiltration; within this TME, microbial-derived tryptophan metabolites foster Aryl hydrocarbon receptor (AhR)-dependent immunoregulatory macrophage polarization, consistent with the broader role of tryptophan catabolism in driving M2-like TAM phenotypes [34,35].