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Figure 1. Key metabolic pathways sustaining the tumor microenvironment. Tumor cells receive different metabolites from the tumor microenvironment. Inflammatory cells release various metabolites to the microenvironment that are taken up by tumor cells or other stroma cells. Tumor associated-macrophages (TAMs) release prostaglandin E2 (PGE2) and high amounts of lactate; tumor associated-neutrophils (TAN) also release PGE2 to the microenvironment. Pre-adipocytes release glutamine, fatty acids (F.A), and arginine through the uptake of citrulline. Cancer-associated fibroblasts (CAFs) secrete glutamine, alanine, high amounts of lactate, exosomes containing amino acids, lipids, and intermediates of the tricarboxylic acid (TCA) cycle, which are taken up by tumor cells. Lactate present in the tumor microenvironment is taken up by macrophages and tumor cells. Glutamine can be taken up by macrophages, neutrophils, and tumor cells. Glucose, when available, is used by most of the cells present in the microenvironment. All these metabolite exchanges contribute to the protumor phenotype of the tumor microenvironment. This figure was created with BioRender (www.biorender.com)