Treatment of human promyelocytic leukemia HL-60 cells with apigeninidin could induce cytotoxicity (IC50 = similar to 80 mu M) along with apoptotic sub-G(1) cells, TUNEL-positive apoptotic DNA fragmentation, activation of the multidomain pro-apoptotic BcI-2 proteins (Bak and Bax), mitochondrial membrane potential (Delta psi(m)) loss, release of mitochondrial cytochrome c and AIF into the cytoplasm, activation of caspase-9, -3, -8, and -7, and cleavage of PARP and lamin B. These induced apoptotic events were accompanied by decrease of Bcl-2 level and increase of Bak and Bax levels. Apigeninidin-induced sub-G(1) cells and activation of Bak and Bax were also detected in human acute leukemia Jurkat T cells, but not in Jurkat T cells overexpressing Bcl-2. Pretreatment of HL-60 cells with the pan-caspase inhibitor z-VAD-fmk reduced significantly apigeninidin-induced sub-G(1) cells and caspase cascade activation, whereas it failed to suppress Bak and Bax activations, Delta psi(m) loss, and release of mitochondrial cytochrome c and AIF. None of FADD and caspase-8 deficiencies affected the sensitivity of Jurkat T cells to apigeninidin-induced cytotoxicity. These results demonstrated that apigeninidin-induced apoptosis was mediated by activation of Bak and Bax, mitochondrial damage and resultant release of not only cytochrome c, causing caspase cascade activation, but also caspase-independent death effector AIF in HL-60 cells. (C) 2012 Elsevier Ltd. All rights reserved.