GDF6 and Ewing sarcoma: shRNA-mediated silencing of GDF6 severely impaired anchorage-independent growth (Figure 2L), migration (Transwell assays in Figure 2M and wound closure assays in Figure 2N), invasion (Figure 2O), sphere formation (Figure 2P), and xenograft tumorigenicity (Figure 2Q) of Ewing sarcoma cells.