AKT1 and Ewing sarcoma: The deletion of phosphatase and tensin homolog on chromosome 10 (PTEN) was identified in 25% of the ES patients, consistent with the PTEN deletion in ES cells, which eventually resulted in the reduced sensitivity to IGF-1R inhibitors, including NVP-AEW541 and OSI-906, and activation of the AKT pathway in the ES cells.