CPS1 and breast carcinoma: When researchers altered ammonia concentrations in breast cancer cells from 0 to 1 mM, the uptake of GLN or glucose and the expression of GS, GDH, and carbamoyl phosphate synthetase I (CPS1) ammonia-assimilating enzymes did not change [71], indicating that supraphysiological concentrations of ammonia may not interfere with the growth of breast cancer cells; however, they may stimulate breast cancer proliferation and growth and conversion to biomass [7].