Metabolic Analyses of Crosstalk between Pancreatic Stromal and Cancer Cells

Metabolic crosstalk between cell types is critical to our mechanistic understanding of pancreatic cancer. The lack of methods to investigate metabolic crosstalk has impeded the comprehensive OMIC characterization of these complex cellular systems. To address this need, an NMR metabolomics method employing a selective isotope-labeling strategy is presented to study metabolic crosstalk in routine cell cultures. 2D 1H-13C HSQC NMR experiments were used to simultaneously monitor pancreatic cancer cells and stromal cells, which revealed a cancer-cell-induced metabolic remodeling of stromal cells. Cancer-cell-conditioned medium was used to stimulate stromal cells, which identified a unique and divergent metabolism in stromal cells in contrast to the classical Warburg metabolism in cancer cells. The two phenotypically different stromal cells exhibited distinct stimulated metabolic profiles; however, the exo-metabolome from both stimulated stromal cells revealed that 13C6-glucose-derived carbon is excreted as alanine and pyruvate. Furthermore, intracellular 13C6-glucose was converted to a variety of tricarboxylic acid cycle-linked and redox metabolites. Stromal cells, unlike cancer cells, mainly convert 13C3-pyruvate to alanine and lactate at an early growth time point, followed by the incorporation of 13C3-pyruvate-derived carbon into multiple amino acids. Interestingly, unstimulated stromal cells depend on pyruvate for survival, whereas cancer cells do not. Simply put, efficient metabolic crosstalk between cancer and stromal cells enables the cells to utilize different metabolic pathways and nutrient sources. Although presented to study cancer-stromal crosstalk, the method can be easily adapted to a variety of cellular crosstalk systems, such as neuron-astrocyte, host-pathogen, or host-microbiota systems.