Figure 5. Inhibition of IDO by 1-methyl DL-tryptophan prevents tryptophan catabolism.

Uveal melanoma cells were cultured in the presence or absence of IFN-γ and also in the presence or absence of 1-methyl DL tryptophan for 72 hours. Supernatants were collected and treated with TCA to precipitate proteins, and mixed with p-dimethylaminobenzaldehyde to stabilize kynurenine in the samples. Kynurenine was detected by colorimetric analysis using a spectrophotometer at a wavelength of A₄₉₀. Kynurenine concentration in uveal melanoma culture supernatants was determined by standard regression analysis derived from colorimetric analysis of kynurenine concentration standards. The results are representative of 3 separate experiments.