IDO1 and cystic fibrosis: The inositol phosphate metabolism pathway was also found to be altered in CF AECs, namely the downregulation of genes encoding phosphohydrolases NUDT11, phospholipase PLCH2 and PLCD4, kinase ITPKB, and phosphatase INPP4B. We also observed a group of upregulated genes, including KYNU, KMO, IDO1, AADAT, and CCBL1, which are associated with the key biosynthetic process of tryptophan catabolism.