PHGDH and colorectal carcinoma: Furthermore, we investigated the relationship between 2HG (sum of D2HG and L2HG) and amino acid metabolism in human CRC tumors and adjacent non-neoplastic tissues using metabolomic data presented in one of our previous studies [18] and found that levels of Phe, Gly, Tyr, Val, Ile, Ser, and Leu, regulated by ATF4 target genes such as PHGDH, SLC7A5, and SLC7A11, were significantly correlated with 2HG levels (Fig. 8).