Clonal Heterogeneity Supports Mitochondrial Metabolism in Pancreatic Cancer

Abstract

Pancreatic ductal adenocarcinoma (PDA) is characterized by a heterogenous and densely fibrotic microenvironment. This limits functional vasculature and diffusion of nutrients through the tumor1,2. Accordingly, pancreatic cancer cells develop numerous metabolic adaptations to survive and proliferate in nutrient austere conditions3-7. Subtypes of PDA have been characterized by transcriptional and functional differences8-12, which have been reported to exist within the same tumor13-15. However, it remains unclear if this diversity extends to metabolic programming. Here, using a combination of metabolomic profiling and functional interrogation of metabolic dependencies, we identify two distinct metabolic subclasses within neoplastic populations isolated from a single pancreatic tumor. Furthermore, these populations are poised for metabolic crosstalk, and in examining this, we find an unexpected role for asparagine in maintaining cell proliferation following mitochondrial inhibition. Functionally, when challenged by mitochondrial inhibition, asparagine supplementation increases intracellular levels of asparagine and aspartate, a rate limiting biosynthetic precursor16-18. Conversely, depletion of extracellular asparagine with PEG-asparaginase sensitizes pancreatic tumors to mitochondrial targeting with phenformin. Together, these data extend the concept of metabolic diversity to neoplastic populations within individual tumors, while illustrating a new method of intratumoral communication that supports tumor fitness19,20. Finally, the combination of asparaginase with mitochondrial inhibition could provide a powerful new strategy for this difficult to treat disease.