GLUD1 and cancer: Therefore, with millimolar ammonium concentrations within cancer cells (Ehrlich ascites mouse cells, 0.4–2.3 mM) (72) and in the surrounding microenvironment (0.8–3 mM) (5), the only possible GDH reaction, regardless of the GDH isoform and subcellular localization, is that of N assimilation.