Although the precise mechanism by which thiostrepton promotes EWS/FLI1 downregulation remains to be elucidated, results from the current study strongly suggest that thiostrepton alone may show greater efficacy in the treatment of EWS than against other tumor types, as it exerts its inhibitory action on EWS cells and tumors at concentrations lower than those reported to be required for effective antitumor activity on other cancer types (44,45,48,49). This evidence concerns the gene FLI1 and cancer.