HDAC9 and Ewing sarcoma: Finally, we treated additional sarcoma cell lines, including HT1080 (fibrosarcoma), RD (rhabdomyosarcoma), and U2OS (osteosarcoma), with romidepsin and observed a similar decrease in the levels of multiple replication proteins, demonstrating that the effect of HDAC inhibitors on DNA replication proteins is not limited to Ewing sarcoma tumors (Fig. 1F).