To determine the in vivo efficacy of PIP/56-1 treatment, we used a subcutaneous xenograft model in which UCSD/AML1 cells were transplanted into Balb/c-RJ (Balbc: Jak3/Rag2 dKO) immunodeficient mice, a commonly used model for assessing antitumor effects of drug treatment, although subcutaneous xenograft models do not reflect the pathological features of AML. Here, JAK3 is linked to acute myeloid leukemia.