In addition to transport, cancer cells can acquire glutamine through the breakdown of macromolecules under nutrient-deprived conditions. Macropinocytosis, which can have a role in normal biology and is active in most non-cancerous cells19, can be stimulated by oncogenic RAS20, enabling cancer cells to scavenge extracellular proteins, which are then degraded to amino acids, including glutamine, supplying metabolites for survival21, 22.