Figure 3.

IDO1 expression in basal-like BC cell lines and patient samples. A. IDO1 mRNA expression was upregulated in basal-like breast tumors. Student t test was used to compare basal-like and luminal subgroups of BC based on a large microarray data set. B, Kynureinine was elevated in basal-type tumors based on metabolic profiling data. C, Kynurenine concentrations in BC tissues were associated with survival based on Kaplan-Meier analysis. D, Semi-quantitative RT-PCR analysis of basal IDO1 mRNA expression in 10 BC cell lines. E, Overnight treatment of IFNγ (100 ng/mL) induced IDO1 protein expression in ER⁻/TNBC cell lines, but not in ER⁺ cell lines. F and G, IDO1 enzymatic assays in MDA-MB-231 and MCF7, respectively. IFNγ (100 ng/mL) induced enzymatically active IDO1 protein expression causing tryptophan catabolism and kynurenine accumulation over time in MDA-MB-231, but not, MCF7 cells. H, Positive correlation between IDO1 mRNA expression and kynurenine relative abundance within tumor was observed in basal-like and all BC patient samples, but not in luminal A samples, based on the results of metabolite and mRNA analysis. Results in D and E are representative gel images from 2–3 independent experiments. Data in F and G are shown by mean ± SEM from three independent measurements.