(A) Capture of extracellular proteins by macropinocytosis to recover amino acids. (B) Uptake of insoluble nutrients, such as iron and cholesterol, through receptor-mediated endocytosis. (C) Utilization of dying cells and/or necrotic cell debris for nutrient acquisition. Solid arrows depict movement of metabolites. Dashed arrows depict regulatory effects of signal transduction components. Tfn, transferrin; LDL, low-density lipoprotein; mTORC1, mechanistic target of rapamycin, complex 1; PTEN, phosphatase and tensin homolog; AMPK, AMP-activated protein kinase.