The 8-CPT-cAMP/ATRA combined treatment induces APL cells differentiation. (A) NBT reduction assays of three U937 cell strains posttreatment of 8-CPT-cAMP (100 μM) and/or ATRA (1 μM) for 3, 5, and 7 d, respectively. (B) Morphological analysis of U937-mt-PLZF/RARα cells after 8-CPT-cAMP (100 μM) and/or ATRA (1 μM) treatment for 7 d (magnification: 1,000×). (C) Activities of pRARE-tk-Luc reporter transfected in both U937-mt-P/R9 and U937-mt-PLZF/RARα cells were detected after 8-CPT-cAMP (100 μM) and/or ATRA (1 μM) treatment for 24 h. (D) Real-time RT-PCR quantified the mRNA expression of RARα2, RARβ2, CEBPɛ, and TGM2 in U937-mt-PLZF/RARα cells after 8-CPT-cAMP (100 μM) and/or ATRA (1 μM) treatment for 24 and 48 h, respectively. Results were presented as mean ± SD of three independent experiments. Briefly, *P < 0.05, **P < 0.01, and ***P < 0.001 in comparison.