Figure 4.

Isotopologue profiling with regard to ¹³C in alanine, aspartate, glutamate, glycine, proline, and serine following incubation of LN18 cells with ²¹³Bi-anti-EGFR-MAb compared to untreated controls. As expected from the results shown in Fig. 2, isotopologue profiling did not reveal significant differences between ²¹³Bi-anti-EGFR-MAb treated and untreated LN18 cells, except for the serine isotopologue containing three ¹³C-atoms (M + 3). However, the frequency of the different ¹³C isotopologues was identical for all amino acids in both cell lines analyzed (EJ28Luc and LN18). For example, in proline consisting of five C-atoms, the most frequent isotopologues contained two ¹³C-atoms and isotopologues with four or five ¹³C atoms could not be detected in both cell lines. SHMT serine hydroxymethyl transferase, ALT alanine aminotransferase, PC pyruvate carboxylase, PDH pyruvate dehydrogenase.