In osteosarcoma, depriving cells of serine and glycine did not change the efficacy of PHGDH inhibition (Figures 2E and 2F), demonstrating that osteosarcoma may be solely reliant on de novo serine biosynthesis for cell survival and suggesting that extracellular serine- and glycine-indifference may be unique to bone tumors. The gene discussed is PHGDH; the disease is bone neoplasm.