AHR and neoplasm: In pancreatic ductal adenocarcinoma (PDAC), the microbiome promotes immune tolerance by modulating tumor-associated macrophages (TAMs) via TLR signaling, fostering an immunosuppressive environment.[4] Recent studies show that PDAC-derived tryptophan metabolites activate the aryl hydrocarbon receptor (AhR) in macrophages, promoting tumor-supportive polarization, reducing inflammatory T-cell infiltration, and enhancing PDAC growth.[5]