Serine starvation promotes Nutlin-3-induced cell death through repression of PHGDH.
A, representative phase-contrast images of A375 cells treated with Nutlin-3 (10 μm) in the presence (Control) or absence (Ser Starv.) of serine in culture medium. B, the percentages of cell death for all treatments shown in A were quantified by trypan blue exclusion assay. Ctrl, control; Nut-3, Nutlin-3. C, Western blot analysis of expression levels of PHGDH, p53, Puma, Tigar, and Actin in A375 cells treated with Nutlin-3 (10 μm) in the presence or absence of serine. D, the percentages of cell death in A375-shGFP and A375-shp53 stable knockdown cells treated with Nutlin-3 (10 μm) in the presence or absence of serine. E, the percentages of cell death in p53 mutant cell lines (Colo-800 and Sk-mel28) treated with Nutlin-3 (10 μm) in the presence or absence of serine. F, the A375 and A375-PHGDH cell lines were treated with the indicated concentrations of Nutlin-3 for 48 h, and the expression levels of PHGDH, p53, Tigar, p21, and Actin were measured by Western blotting. G, the percentages of cell death in A375 and A375-PHGDH cell lines treated with Nutlin-3 (10 μm) under normal or serine starvation condition. Error bars represent mean ± S.D. from three different experiments.