Figure 2
From: 13C and 15N natural isotope abundance reflects breast cancer cell metabolism
Cancerous cell lines are naturally 13C-enriched and 15N-depleted.
When compared to source C and N used for growth, the natural isotopic enrichment (ε13C and ε15N) differentiates the control immortalized line (MCF10A) and the breast tumor ascites-derived line (ZR75-1) from other adenocarcinoma lines (a). The isotope enrichment in lipids parallels that in total organic matter and cancerous lines contain more (13C-enriched) C4-acids (b). Despite some variations, transcript quantitation of key enzymes shows a generally lower expression in cancer cells compared to MCF10A cells of enzymes of the urea cycle, lipid synthesis or the anaplerotic pathway (gene abbreviations in Supplementary Table S5), suggesting that metabolite excretion in addition to biosynthesis is involved in the isotopic differences (c).
