We also performed isotope tracing with 13C-labeled Arg in Reh and BaF3 cells and observed enhanced proline anabolism from Arg in KRAS-G12D cells (Figures 4G–4I), consistent with the aberrantly accumulated proline we earlier observed in RASmt B-ALL cells (Figure 3A). The gene discussed is KRAS; the disease is acute lymphoblastic leukemia.