NR2E3 and Ewing sarcoma: In previous work, we identified that the iron-dependent RRM2 subunit of ribonucleotide reductase (RNR), which is the rate limiting and iron-dependent enzyme in the synthesis of deoxyribonucleotides and required for DNA replication, is one target of iron chelators in Ewing sarcoma cells [7, 17, 20].