Consistently, the frequency of B7-H4-null Mac-1+Gr-1− leukemia cells (Gr-1 expression level indicates the extent of myeloid cell differentiation) in the peripheral blood increased markedly to twofold greater than that in WT controls upon primary transplantation (38.7±1.2% vs 17.2±3.4%, Figure 1b). Here, VTCN1 is linked to leukemia.