FLT3 and neoplasm: A20 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 was confirmed by flow cytometry (Supplementary Figure 1) before tumor cells were subcutaneously inoculated on the back of BALB/c mice.