cytochrome-c-t and Leukemia--Erythroblastic--Acute

Matrine is a major component of Sophora Flavescens and has been reported to stimulate differentiation of erythroleukemia cells. Here we show that matrine inhibits cell proliferation or induces apoptosis in a cell type-specific manner. The latter effect was investigated in more detail in the p53 deficient erythroleukemia cell line, K562. Matrine exposure induced apoptosis in a time- and dose-dependent manner in these cells. Interestingly, co-treatment with etoposide potentiated apoptosis. Further analysis of matrine-induced apoptotic changes revealed that E2F-1 and Apaf-1 were upregulated, whereas Rb was downregulated after 24 h of exposure. This was followed by Bax translocation, cytochrome c release, and caspase-9 and -3 activation. These results demonstrate that matrine triggers apoptosis of K562 cells primarily through the mitochondrial pathway and that matrine is a potential anti-tumor drug.

Topics: Alkaloids; Antineoplastic Agents, Phytogenic; Apoptosis; Apoptotic Protease-Activating Factor 1; bcl-2-Associated X Protein; Caspase 3; Caspase 9; Cytochromes c; Dose-Response Relationship, Drug; Down-Regulation; Drug Synergism; E2F1 Transcription Factor; Enzyme Activation; Etoposide; HeLa Cells; Humans; K562 Cells; Leukemia, Erythroblastic, Acute; Matrines; Mitochondria; Protein Transport; Quinolizines; Retinoblastoma Protein; Time Factors; Tumor Suppressor Protein p53; U937 Cells; Up-Regulation

Ligation of the cell surface molecule CD44 by anti-CD44 monoclonal antibodies (mAbs) has been shown to induce cell differentiation, cell growth inhibition and in some cases, apoptosis in myeloid leukemic cells. We report, herein, that exposure of human erythroleukemic HEL cells to the anti-CD44 mAb A3D8 resulted in cell growth inhibition followed by caspase-independent apoptosis-like cell death. This process was associated with the disruption of mitochondrial membrane potential (Delta Psi m), the mitochondrial release of apoptosis-inducing factor (AIF), but not of cytochrome c, and the nuclear translocation of AIF. All these effects including cell death, loss of mitochondrial Delta Psi m and AIF release were blocked by pretreatment with the poly (ADP-ribose) polymerase inhibitor isoquinoline. A significant protection against cell death was also observed by using small interfering RNA for AIF. Moreover, we show that calpain protease was activated before the appearance of apoptosis, and that calpain inhibitors or transfection of calpain-siRNA decrease A3D8-induced cell death, and block AIF release. These data suggest that CD44 ligation triggers a novel caspase-independent cell death pathway via calpain-dependent AIF release in erythroleukemic HEL cells.

Topics: Antigens, CD; Apoptosis; Apoptosis Inducing Factor; Calpain; Caspases; Cell Cycle; Cell Death; Cell Line, Tumor; Cell Survival; Cytochromes c; DNA, Neoplasm; Electrophoresis, Gel, Pulsed-Field; Humans; Hyaluronan Receptors; Isoquinolines; Leukemia, Erythroblastic, Acute; Membrane Potentials; Mitochondrial Membranes; Poly(ADP-ribose) Polymerase Inhibitors; Protein Transport; RNA, Small Interfering; Transfection

Mitochondria play a key role in the regulation of apoptosis induced by numerous antitumor chemotherapeutic and other toxic agents. Photodynamic therapy (PDT) exerts significant cellular killing efficacy through either an apoptotic or necrotic cell death pathway. This study investigated the mechanism underlying the killing effects of a novel amphipathic photosensitizer [di-sulfonated di-phthalimidomethyl phthalocyanine zinc (ZnPcS2P2)]-mediated photodynamic therapy (ZnPcS2P2-PDT) on K562 cells. Apoptosis was evident in the post-PDT cells through the TdT-mediated dUTP nick end labeling (TUNEL) method and DNA fragmentation assay. After ZnPcS2P2-PDT, K562 cells underwent mitochondria-dependent apoptosis as evidenced by the release of cytochrome c from mitochondria into cytosol, accompanied by mitochondrial membrane potential (deltapsim) reduction, indicating the opening of the mitochondrial permeability transition pore (PTP). The activities of protease from the caspase family and caspase-3 were also significantly elevated. Furthermore, ZnPcS2P2-PDT down-regulated the expression of chimaeric Bcr-Abl oncoprotein, which is the molecular hallmark of chronic myelogenous leukemia (CML).

Topics: Apoptosis; Caspase 3; Caspases; Cytochromes c; DNA Fragmentation; Down-Regulation; Flow Cytometry; Fusion Proteins, bcr-abl; Humans; In Situ Nick-End Labeling; Indoles; Intracellular Membranes; K562 Cells; Leukemia, Erythroblastic, Acute; Membrane Potentials; Mitochondria; Organometallic Compounds; Photochemotherapy