For example, mouse Ews/Fli-1-transformed cells coexpressing mutant KRAB/FLI-1 formed tumours in nine out of 10 mice inoculated with a mean size of 96±26 mm3 by day 30; however, at the same stage no tumours were observed in cells coexpressing KRAB/FLI-1. This evidence concerns the gene EWSR1 and neoplasm.