CAD and malignant colon neoplasm: Besides, we detected the expression of two other enzymes involved in ammonia assimilation, glutamate dehydrogenase 1 (GDH1), and glutamine synthetase (GS), which were expressed in most cancer cells, except for colon cancer cell line HCT8, but the level of phosphorylated CAD was higher in HCT8 than other cells.