a, Proliferation rates of HeLa cells cultured in media +lipids or −lipids, without or with phenformin (100μM), and/or aspartic acid (10mM or 20mM) as indicated (n=3 per condition from a representative experiment). b, Proliferation rates of HeLa cells cultured in media +lipids or −lipids, without or with phenformin (100μM), and/or sodium aspartate (10mM) as indicated (n=3 per condition from a representative experiment). c, Proliferation rates of H1299 cells cultured in media +lipids or −lipids, without or with phenformin (10μM), and/or sodium aspartate (10mM) as indicated (n=3 per condition from a representative experiment). All data represent mean ± s.d. *P < 0.05, **P < 0.01, ***P < 0.001, ns P > 0.05, unpaired Student’s t-test. All experiments were repeated 3 times or more.