As an integral aspect of the metabolic reprogramming that occurs in cancer, oncogenic KRAS mutations drive the stimulation of macropinocytosis, a type of endocytosis that mediates nonselective fluid-phase uptake. Using KRAS-driven models of pancreatic ductal adenocarcinoma (PDAC), we were the first to demonstrate that macropinocytosis functions in tumor cells as a nutrient acquisition pathway. Macropinocytosis triggers the internalization of extracellular proteins via discrete endocytic vesicles called macropinosomes. The incoming protein cargo is targeted for lysosome-dependent degradation, causing the intracellular release of amino acids. These protein-derived amino acids support metabolic fitness by contributing to the intracellular amino acid pools, as well as to the biosynthesis of central carbon metabolites. In this way, macropinocytosis represents a novel amino acid supply route that tumor cells use to survive the nutrient-poor conditions of the tumor microenvironment. While the tenets of the signal transduction events that drive macropinocytosis in cancer have emerged, a detailed picture of the macropinosome itself is not yet available. With the aid of nanotechnology, we have developed methodology to isolate a pure fraction of macropinosomes from PDAC cells. Having the capability to purify macropinosomes, we are now uniquely positioned to benefit from largescale proteomics that can provide a broad picture of this important organelle. By elucidating the molecular anatomy of KRAS-driven macropinosomes, we will gain further insight into the regulation and function of macropinocytosis in cancer. Moreover, having a clearer picture of the macropinosome will make us better positioned to exploit this pathway therapeutically and deliver breakthroughs to patients.
Pancreatic ductal adenocarcinoma (PDAC) is a recalcitrant cancer that is in urgent need of innovative therapeutic strategies that offer an improvement in clinical outcome. This project seeks to make strides in cancer treatment and precision medicine by identifying the molecular machinery associated with macropinocytosis, an endocytic uptake pathway that functions as an amino acid supply route in cancer cells. The goal of this proposal is to decipher macropinosome-resident proteins in PDAC that could serve as the basis for the development of novel targeting strategies and biomarker assays.
