Figure 4. PHGDH inhibition in a PHGDH-dependent cell line unexpectedly reduces the incorporation of exogenous serine into dTMP and AMP.

All data are the mean of three biological replicates. Error bars represent standard deviations. *, p<0.05, Student’s t-test. a, Incorporation of ¹³C from glucose, glucose-derived serine, and exogenous serine into nucleotides. b, 10 µM NCT-503 treatment for four hours reduces the synthesis of glucose-derived serine and decreases the incorporation of ¹³C from glucose via serine into AMP. c, 10 µM NCT-503 treatment for four hours in the presence of exogenous U-¹³C-serine does not increases the proportion of labeled serine but increases the fraction of labeled glycine, consistent with decreased synthesis of unlabeled serine. Unexpectedly, NCT-503 reduces the incorporation of one-carbon units from exogenous U-¹³C-serine into AMP and dTMP.