ASS1 and neoplasm: ASS1 is a key enzyme in aspartate metabolism (Figure 7A) and serves a regulatory function in the intracellular aspartate levels.[26, 27] Previous study has shown that aspartate promotes tumor growth through activating the S6K/CAD pathway.[12] Besides, our published data have linked CAD with stemness properties and HCC progression.[28] As expected, GSEA demonstrated that circRAPGEF1 overexpression in HepG2 cells upregulated amino acid metabolism pathway (Figure 7B).