CASP3 and Ewing sarcoma: Consistent with the growth phenotype observations, EF-targeted cells had higher levels (5–8-fold) of apoptosis, measured both by propidium iodide staining (subG1 cells, Fig. 2g) and caspase-3 analysis (Fig. 2h), than control transduced cells, suggesting that CRISPR-mediated abrogation of EF is sufficient to inhibit the survival, proliferation, and clonogenicity of EF-expressing Ewing sarcoma cells in vitro.