IDO1 and ovarian carcinoma: Afterward, univariate Cox regression analysis was performed to evaluate the prognostic value of each tryptophan metabolism-related gene in the TCGA ovarian cancer cohort, with IDO1, ALDH3A2, HADHA, OGDHL associated with risk values, and CAT, WARS1 involved in protective factors (Additional file 1: Fig. S5b).