ATI induces terminal differentiation of NB4, NB4-R2, and primary leukemic cells harvested from APL patients. (A) Morphological examination of APL cells treated with ATI. (B) Detection of NBT reduction activity and CD11b/CD14 expression of cells treated with ATI. (C) Expression of CD11b in primary leukemic cells treated with ATI in vitro. Concentration of agents used: A, 0.375 μM; T, 0.75 μM; I, 0.75 μM. (D) Combination of A, T, and I exerts synergic effects on NB4 and NB4-R2 cells, as reflected by the median-effect method of Chou and Talalay (23).