Breast cancer cells that preferentially metastasize to lung or bone are more glycolytic, synthesize serine at greater rates, and consume less ATP and NADPH than parent MDA-MB-231 cells

Table 4 ¹³C lactate labeling and model-optimized flux ratios with [5-¹³C] glutamine

	Lactate ¹³C isotopologue content (%)				Modeled flux ratios (%)
	M	M1	M2	M3	\(\frac{J_{11a+b}}{J_{11a+b}+{J}_{12f}}\) (R8)	\(\frac{J_{11a+b}}{J_{10}}\) (R9)	\(\frac{J_7}{J_{2c}+{J}_7}\) (R10)	\(\frac{J_{6a}}{J_{6a}+{J}_{6b}}\) (R11)	Model error (%)
T47D	99.13±0.09 ^a (99.15±0.08)	0.83±0.06 ^a (0.85±0.08)	0.03±0.01 ^a (0±0)	0.02±0.02 ^a (0±0)	46.6±1.3 ^a	63.2±3.4 ^a	3.5±0.2 ^a	100±0 ^a	0.11±0.04
MDA231	99.66±0.06 ^b (99.67±0.06)	0.33±0.06 ^b (0.33±0.06)	<0.01±0.01 ^a (0±0)	<0.01±0.00 ^a (0±0)	49.7±0.5 ^a	43.5±1.6 ^b	1.3±0.2 ^b	100±0 ^a	0.06±0.01
BoM	99.54±0.02 ^b (99.45±0.04)	0.46±0.02 ^b (0.55±0.04)	<0.01±0.00 ^a (0±0)	<0.01±0.00 ^a (0±0)	84.3±6.6 ^b	52.8±3.0 ^a,b	1.3±0.1 ^b	95±5 ^a	0.19±0.09
LM	98.05±0.06 ^c (98.11±0.07)	1.92±0.05 ^c (1.89±0.07)	0.02±0.00 ^a (0±0)	<0.01±0.00 ^a (0±0)	95.9±2.1 ^b	47.4±4.1 ^b	3.9±0.2 ^a	0±0 ^b	0.14±0.04

Cells were equilibrated with 1.5 mM [5-¹³C] glutamine and unlabeled glucose in 2-well Lab-Tek chambers for approximately 24–26 h. Basal respiration rate was assessed for approximately 1.5 h, followed by 2 × 1 h incubations to determine the rates of glucose and glutamine uptake, lactate production, and ¹³C enrichment in lactate. ¹³C lactate labeling (mean ± SEM, n=4) is expressed as percent contribution of each isotopologue to total extracellular lactate (M, M1, M2, and M3 denote lactate with none, one, two, two, or three ¹³C atoms, respectively). Data in parentheses are simulated lactate labeling (mean ± SEM, n=4) from Model 3-optimized flux ratios R8, R9, R10, and R11. Model error was calculated as the sum of the absolute values of the difference between the measured and calculated M-M3 lactate. Within a column, means sharing common superscripts do not significantly differ. Background isotopologue abundance for cells metabolizing unlabeled glucose averaged 96.52±0.05, 3.08±0.05, 0.40±0.01, and <0.01±0.01% for M, M1, M2, and M3, respectively. For these experiments, lactate labeling with [5-¹³C] glutamine was corrected for background labeling

ISSN: 2049-3002