When a genome editing system became available to induce a DSB of human genome at any locus of interest, EWSR::FLI1 and NPM1::ALK, which are oncogenic fusions in Ewing sarcoma and anaplastic large cell lymphoma, respectively, were artificially generated in human mesenchymal precursors using zinc finger and transcription activator-like effector nucleases [45]. Here, FLI1 is linked to Ewing sarcoma.