Interestingly, 2-HG can be derived also from the promiscuous activity of some key metabolic enzymes, including malate dehydrogenase (MDH), lactate dehydrogenase (LDH) [25], and phosphoglycerate dehydrogenase (PHGDH) [26], and can accumulate in cancer cells in both its enantiomeric forms (i.e., D- and L-2HG). This evidence concerns the gene PHGDH and cancer.