In this context, it has been shown that removal of dietary tryptophan, which cause AhR inhibition, and administration of ampicillin, an antibiotic that eradicates indole-producing Lactobacilli, all restored cytotoxic IFNγ + TNF⍺ + CD8 + T-cell function, increased tumor-associated macrophages expression of PD-L1 and MHC class II molecules, and reduced the expression of Cyp1a1, Cyp1b1, and Cyp1a2 genes [142]. This evidence concerns the gene CYP1A1 and neoplasm.