Cancer has long been recognized as a disease of altered cellular metabolism as cancer cells have an abnormally high demand for nutrients to support their growth and proliferation. However, targeting cancer cell metabolism has not been seriously explored as a potential therapeutic strategy until recently. The Haigis lab at Harvard Medical School has shown that ammonia accumulates in the tumor microenvironment and then is primarily assimilated through Glutamate Dehydrogenase (GDH) activity to generate amino acids. Furthermore, many cancer patients experience hyperammonemia as a side effect of treatment due to cancer cell lysis. These results demonstrate that ammonia is not simply a secreted waste product but a crucial metabolite that plays an important role in cancer cells’ ability to meet nutritional needs. Thus, targeting ammonia metabolism provides a promising avenue for novel cancer therapeutics.