ALDH9A1 and prostate adenocarcinoma: In the TCGA-PRAD cohort, a signature of eight ALDH genes (including ALDH1A1, ALDH1A2, ALDH1B1, ALDH2, ALDH3A2, ALDH7A1, ALDH8A1, and ALDH9A1) involved in tryptophan metabolism was predominantly downregulated compared to normal patients, with the fold change of ALDH1A2 being the most severe among the panel [75].