KLF4 and acute promyelocytic leukemia: Similarly, we observed that the expression of several genes that marked monocytic maturation, such as Irf8, Klf4, Irf7 and Tlr7, and the expression of a few granulocytic genes were upregulated with the spontaneous maturation of the c-Kit+CD11b++ APL cells from c-Kit+ CD11b+ or cKit+CD11b−AA4.1++ APL progenitors (Figure 4d).