(P16-022-23) Energy Metabolism in Breast Cancer Cells That Preferentially Metastasize to Lung and Liver

Objectives: To determine if the preferential metastasis of breast cancer to distant sites with different metabolic environments, such as lung and liver, depend on their ability to utilize energy substrates such as glucose, glutamine and fatty acids.

Methods: A Wnt-driven metastasis model of triple-negative breast cancer that either does not metastasize (M-Wnt) or preferentially metastasizes to the lung (metM-Wnt^Lung) or liver (metM-Wnt^Liver) were utilized. Protein expression of metabolic enzymes, ¹³C-metabolic flux analysis using uniformly labeled isotopes for glucose, glutamine and acetate, and ¹⁴C-palmitate uptake were analyzed to compare energy metabolism.

Results: Protein expression of pyruvate carboxylase (PC), the enzyme that converts pyruvate to oxaloacetate in the tricarboxylic acid (TCA) cycle, is 40% higher in metM-Wnt^Liver and 50% lower in metM-Wnt^Lung compared to non-metastatic M-Wnt. This is consistent with the increase in ¹³C₆-glucose flux to [M+3]-fumarate and -malate, suggesting increased PC activity in metM-Wnt^Liver as compared to metM-Wnt^Lung. On the other hand, the ratio of phospho-pyruvate dehydrogenase (PDH)/PDH, phosphorylation prevents conversion of pyruvate to acetyl CoA into TCA cycle, showed a 3-fold decrease in metM-Wnt^Lung compared to M-Wnt and metM-Wnt^Liver, suggesting differences in glucose metabolism. Moreover, ¹³C₅-glutamine flux into [M+4]-fumarate and -malate were increased in metM-Wnt^Lung, but treatment of high glutamine increased cell growth of metM-Wnt^Liver by 20% compared to metM-Wnt^Lung, suggesting increased adaptability to utilize glutamine in liver metastasis.  Also, the fatty acid synthesis rate was highest in metM-Wnt^Lung, as shown by significantly greater incorporation of de novo fatty acid substrates into palmitic and stearic fatty acids. Although lipid stores and ¹⁴C-palmitate uptake were similar, CPT1α expression, a rate-limiting enzyme for fatty acid oxidation (FAO), was higher in metM-Wnt^Lung (2.6-fold) compared to M-Wnt, suggesting increased FAO capacity.

Conclusions: Overall, breast cancer cells with preferential metastasis to lung and liver exhibit differential glucose, glutamine and fatty acids utilization which may drive their colonization to these target sites.

Funding Sources: National Institutes of Health, Women’s Global Health Institute and Purdue Institute for Cancer Research