Figure 3. Reductive carboxylation in spheroids is primarily dependent on cytosolic IDH1.

Fractional abundance of citrate m+4 and m+5 in spheroids containing or lacking IDH1 (a) or IDH2 (b) cultured in [U-¹³C]glutamine (n=3 cultures from two experiments). c, Abundance of total citrate and of citrate m+4 and m+5 from [U-¹³C]glutamine in H460 spheroids containing or lacking IDH3 (n=2 cultures from a representative experiment). d, Fractional abundance of citrate m+4 and m+5 in H460 spheroids cultured with [U-¹³C]glutamine and treated with an IDH1 inhibitor (321) or a structurally similar control compound (990) (n=4 cultures from two experiments). e, Fumarate mass isotopologues in mitochondria isolated from cells containing or lacking the citrate transporter protein (CTP-WT and CTP-KO, respectively). Isolated mitochondria were cultured with [U-¹³C]citrate as the sole carbon source (left), or [U-¹³C]citrate with unlabeled pyruvate and glutamine (right) (n=4 cultures from two experiments). *p<0.05, ANOVA (a–b), or Welch's unequal variances t-test (c–e). All experiments were repeated 3 times or more.