YW152F inhibits the growth of Ewing sarcoma in vivo and does not effect tumor cell proliferation or viability in vitro. (A) TC71 or A4573 cells were subcutaneously injected in nude mice that had previously received GFP⁺ BM transplants. Mice were treated twice weekly with YW152F, IgG, or PBS and tumor growth was quantified. Black lines show mean volumes for each group. (B) TC71 or A4573 cells were seeded in triplicate in 6-well dishes. Cells were treated daily with either 5 μg/mL of YW152F or human IgG control. Cell viability and total cell number were assessed at 48 and 72 hours using the trypan blue assay and automated Vi-Cell cell counter. Black bars represent IgG-treated cells, and striped bars represent YW152F-treated cells. (P > .05 for all data.)