KRAS and neoplasm: Although tumor-bearing and normal lung mice exhibited similar levels of m+3 isotopologues of lactate and pyruvate (Figure 7A,C), we observed increased m+2 and m+3 isotopologue labeling of several TCA cycle intermediates consistent with Kras-driven lung tumors exhibiting increased lactate utilization as a nutrient source for the TCA cycle (Figure 7A,D).