IDO1 and posterior cortical atrophy: The significant correlation between levels of expression of IDO and its activity (kynurenine/tryptophan ratio) in PCa specimens, the trend seen in relation to PCa patients' clinical features [Gleason score (GS)], and the finding that TGF-β expression was significantly correlated to IDO gene expression in PCa contributed to the identification of a peculiar subset of tumors (9).