This PLOS ONE paper, co-authored by Alban Bessède, CSO of Explicyte, demonstrates that the expression of tryptophan-degrading enzyme IDO1 is not strictly associated with L-Kynurenine production in breast and colorectal cancer tissues. The study suggests that the in situ detection of L-Kynurenine could serve to stratify patients in the context of cancer immunotherapies targeting tryptophan catabolic enzymes: indoleamine 2,3-dioxygenase (IDO-1/-2) or tryptophan 2,3-dioxygenase 2 (TDO2).