Bioinformatic analysis revealed that TDO2 mRNA levels were negatively correlated with AR and genes associated with AR, including SAM pointed domain containing ETS transcription factor (SPDEF), FOXA1, cAMP responsive element binding protein 3 like 4 (CREB3L4), RAB6C (a member of the RAS oncogene family), NK3 homeobox 1 (NKX3-1) and coiled-coil domain containing 125 (CCDC125), in an RNA sequencing database comprised of 208 prostate cancer samples38 (Supplementary Fig. S16a, b). Here, AR is linked to prostate cancer.