We then extracted protein and RNA from LNCaP-EnzR tumours and found that although the TDO2 inhibitor 680C91 and the AhR inhibitor CH223191 had no significant effect on AhR protein or mRNA levels (Supplementary Fig. S14e, f), they significantly reduced the mRNA levels of the AhR target gene CYP1A1 (Fig. 3n). Here, TDO2 is linked to neoplasm.