Fig. 1.

Kynurenine:tryptophan ratios are higher in patients with advanced prostate cancer. Sera or plasma samples were evaluated for kynurenine and tryptophan concentrations from normal male volunteer blood donors (n = 12), patients with newly diagnosed prostate cancer pre-treatment (n = 14), patients with non-castrate, PSA-recurrent non-metastatic (M0) prostate cancer (n = 15), castration-resistant, M0 prostate cancer (n = 15), and castration-resistant, metastatic prostate cancer (n = 16). Shown are the ratios of kynurenine-to-tryptophan for each group (a), and overall with respect to subject age (b) or serum PSA for individuals with prostate cancer (c). Open circles in panel b are normal male blood donors. For panel a, *p < 0.05 (Kruskal–Wallis test with Dunn’s correction for multiple comparisons). Tests of correlation with age and PSA (b and b) were made by Spearman test