Fig. 6.

Bi-plot of Loadings and Scores from principal component analysis of Table 2 data. Flux ratios R5-R7 (see Table 2) were determined from Model 2 by simulating ¹³C serine labeling from [1,2-¹³C] glucose, using [¹³C] 3-phosphoglycerate labeling simulated by Model 1 (Table 3). The Scores reflecting individual experiments clustered into two groups—the less malignant T47D line and the LM/BoM lines, indicating differences in relative folate cycle fluxes for more vs. less malignant cells. MDA-MB-231 cells were not analyzed since there was no significant ¹³C enrichment in serine. The Loadings are indicated by arrows and provide information on relative strength of correlations between the variables R5–R7 used to simulate ¹³C serine labeling