RNA-seq data from the Cancer Cell Line Encyclopedia (CCLE; Broad Institute) indicated relatively low-baseline mRNA expression of the serine transporter ASCT2/SLC1A5, which could explain why PHGDH inhibition cannot be compensated for with extracellular serine and glycine in osteosarcoma cells (Barretina et al., 2012). The gene discussed is PHGDH; the disease is osteosarcoma.