A,ATF4 gene expression in patient tumors from three independently published Ewing sarcoma datasets [32–34]. B,
ATF4 mRNA and protein levels in Ewing sarcoma cell lines and non-Ewing mesenchymal cell lines (N=3). C, Trypan blue exclusion proliferation assay after shRNA knockdown of ATF4 (N=2). D, qRT-PCR and E, representative western blot of SSP (PHGDH, PSAT1, and PSPH) mRNA and protein (A673 & A4573– 30 µg, TC32– 50 µg) in Ewing sarcoma cell lines after 96 hours of shATF4 knockdown (N=3). F, Chromatin immunoprecipitation qRT-PCR (ChIP-qPCR) for ATF4 at PHGDH and PSAT1 gene promoters. Negative control is a promoter region in chr2 without ATF4 binding (N=3). G, Representative western blots and qRT-PCR for SSP expression in ATF4 overexpressing (OE) Ewing sarcoma cells (A4573– 30 µg, TC32– 50 µg) (N=2, N=3). Error bars represent SEM from independent biological replicates. * p<0.05; ** p<0.01; *** p<0.001; **** p<0.0001; Two-tailed t-test.