Figure 2.

Tryptophan metabolism pathway alterations in breast tumor tissues compared to normal breast tissues. Log-scale differences in the major Trp metabolites in normal and breast tumor tissues are shown in the scatter plot graphs. The Trp metabolism pathway begins with the rate-limiting inflammatory cytokines, IDO and TDO, which involves cleaving Trp by indoleamine 2,3-dioxygenase (IDO1/IDO2) or tryptophan 2,3-dioxygenase 2 (TDO2) to form N-formylkynurenine. N-formylkynurenine is further metabolized by enzymes to kynurenine. The byproducts of Trp with microbiome metabolic origin or contribution, indoleproprionate (IPA) and indoxyl sulfate, are indicated by the dotted line. * p < 0.05, *** p < 0.0005, **** p < 0.0001 is considered statistically significant.