ER− breast cancer metabolomes generally tend to demonstrate more drastic and characteristic features compared to ER+ breast cancer: elevated β-alanine (suggested as the strongest differentiating marker between ER− and ER+ breast cancer), an accumulation of 2-hydroxyglutarate (2HG), GSH, branched-chain amino acids, carnitines, and strongly elevated cholines (in particular phosphocholine and phospholipids) combined with elevated glycerol-3-phosphate acyltransferase (GPAM) activity has been detected [39–41, 43, 47]. The gene discussed is GPAM; the disease is breast cancer.