Dissecting cell type-specific metabolism in pancreatic ductal adenocarcinoma

Tumors are composed of many different cell types including cancer cells, fibroblasts, and immune cells. Dissecting functional metabolic differences between various cell types within a mixed population can be limited by the rapid turnover of metabolites relative to the time needed to isolate cells. To overcome this challenge, we traced isotope-labeled nutrients into macromolecules that turn over more slowly than metabolites. This approach was used to assess differences between cancer cell and fibroblast metabolism in pancreatic cancer organoid-fibroblast co-cultures and in pancreatic tumors. In these contexts, we find pancreatic cancer cells exhibit increased pyruvate carboxylation relative to fibroblasts, and that this flux depends on both pyruvate carboxylase and malic enzyme 1 activity. Consequently, expression of both enzymes in cancer cells is necessary for organoid and tumor growth, demonstrating that dissecting the metabolism of specific cell populations within heterogeneous systems can identify dependencies that may not be evident from studying isolated cells in culture or bulk tumor tissue.