FIGURE 1.

Elevated TDO2‐kynurenine pathway activity in patient‐derived colon cancer spheroids is associated with liver metastasis. A, Experimental scheme. B, Volcano plot of the quantified concentration for cationic metabolites through the comparison of nonmetastatic spheroids vs. metastatic spheroids. L‐kynurenine is indicated by the arrow. C, Levels of kynurenine per cell measured by chromatography tandem mass spectrometry (GC‐MS/MS). D, E, qPCR analyses of (D) TDO2 and (E) IDO1 in the indicated spheroids. F, Representative immunostaining for TDO2 in spheroids with a low (CRC‐20) or high (CRC‐24 M) level of TDO2. Nuclei were counterstained by Hoechst 33 342. Scale bar: 50 µm. Values represent the mean ± SD