C1498 cells were transfected with plasmid vectors harboring truncated mouse Flt3 gene that contained only the extracellular, transmembrane, and a small part of the intracellular domain of Flt3. FLT3 antigen expression on C1498-FLT3 cells was verified (Supplementary Figure 1) before the tumor cells were intravenously injected into B6.SJL mice. This evidence concerns the gene FLT3 and neoplasm.