Tumor cell metabolism in action

Project Summary/Abstract Tumors have distinctive metabolism. These distinguishing metabolic features enable both cancer diagnosis and therapy. Due to fast glucose metabolism, tumors light up by fluorodeoxyglucose PET imaging. Due to enhanced nucleotide synthesis, they are susceptible to antifolates, which are first-line therapies for leukemia (methotrexate) and lung cancer (pemetrexed). New facets of tumor metabolism continue to be discovered. Previously, co-PIs White and Rabinowitz contributed to the identification of autophagy and macropinocytosis as non-canonical means of cancer cell nutrient acquisition. Recently, they identified thrifty energy metabolism in tumors: by shedding normal tissue functions, tumors can grow and divide despite making less energy than most normal tissues. While valuable, up to now studies measuring tumor metabolic activity (e.g. with isotope tracing and mass spectrometry) have mainly studied the tumor as a whole. In the current era of immunotherapy, the insufficiency of this approach is painfully clear. Whole tumor measurements confound the metabolism of cancer cells and cancer-fighting immune cells. To resolve metabolism in tumors with cell type specificity, new methods are needed. Here we will develop and deploy such methods. The resulting knowledge will provide the basis for manipulating metabolism more effectively to help fight cancer. Aim 1 will determine, in state-of-the-art mouse modes, in vivo central metabolic fluxes (glycolysis, TCA) across different tumor cell types and during active response to immunotherapy. Aim 2 will measure how different tumor cell types obtain nucleotides. Nucleic acid synthesis is a clinically proven cancer vulnerability but at the same time, nucleotide synthesis inhibitors can also impair immune cells. We will assess nucleotide synthesis and scavenging, and how it changes in response to anti-folates. Defining the dynamics of nucleotide metabolism in vivo with cellular resolution will inform the metabolic relationship between tumor and immune cells in the tumor microenvironment. Aim 3 will explore the interplay between autophagy, metabolism, and antitumor immunity. Autophagy supports tumor cell metabolism, and host autophagy supplies nutrients to tumors and dampens antitumor immunity. We will use mouse genetics, nutrient supplementation, single cell transcriptomics, and in vivo isotope-tracing of host and tumor metabolism to define underlying mechanisms. The net impact of these efforts will be (i) broadly useful methods for tracking metabolism in action across cell types, (ii) fundamental knowledge of the metabolic feedstocks and pathways used by different tumor cells, and (iii) next-generation metabolic strategies for treating cancer.