PCK2 and neoplasm: Amino acids with a relevant role in regulating the anabolic potential of the tumor, such as serine, glycine, proline, or threonine, showed increased molar fractions with increasing PEPCK-M expression with excess glucose in the media (Fig. 1g) and in a more physiological glucose exhaustion condition (Fig. 1h; 24 h after media refresh with 1 mM glucose which is depleted within the initial 12 h; see Supplementary Figure 2).