MDM4 and Ewing sarcoma: Cell line sensitivity to XI-006 was not correlated with MDM4 mRNA or protein levels, and reduction of MDM4 mRNA and protein levels were only observed in the least sensitive Ewing sarcoma and osteosarcoma cell lines at high XI-006 concentrations (>1 μM) that also induced DNA damage (Figs 3 and 4).