title: Cell cycle specific induction of apoptosis and necrosis by paclitaxel in the leukemic U937 cells.
abstract: Induction of cell apoptosis and necrosis by paclitaxel was investigated in human leukemic U937 cells. To explore whether paclitaxel induces both apoptosis and necrosis in different cell cycle stages, we synchronized the cells in G1, S and G2/M stages by counterflow centrifugal elutriation (CCE). The Annexin V and PI analysis revealed that, after paclitaxel treatment, the cells in G1 and S stages died predominantly through apoptosis, whereas G2/M-stage cells died through both apoptosis and necrosis. These phenomena were verified by a trypan blue exclusion assay and by detection of the release of lactose dehydrogenase (LDH). Paclitaxel treatment significantly decreased viability in G2/M cells and led these cells to release more LDH than other cells. These treated cells also released certain substances that inhibited cell growth. These results strongly suggest that the cell membrane of the treated G2/M-cells is disrupted, leading to the leakage of LDH and cell growth inhibitory substances out of cell. Furthermore, the typical events of apoptosis, such as the release of cytochrome c and the decrease of mitochondria membrane potential, occur primarily in S stage rather than in the G2/M stages. These results suggest that paclitaxel induces typical apoptosis in the G1- and S- cells, but it induces both apoptosis and necrosis in G2/M-phase cells.
authors.affiliation: Faculty of Biotechnology and Laboratory Science in Medicine/Institute of Biotechnology in Medicine, National Yang-Ming University, Taipei, Taiwan 112, Republic of China.
authors.forename: Pei-Chin
authors.initials: PC
authors.lastname: Liao
authors.forename: Chien-Hui
authors.initials: CH
authors.lastname: Lieu
mesh_terms: D017304:Annexin A5 / Q000737:chemistry; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects*; D003114:Colony-Forming Units Assay; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D019254:Genes, bcl-2 / Q000187:drug effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D007202:Indicators and Reagents; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D009336:Necrosis; D017239:Paclitaxel / Q000494:pharmacology*; D011419:Propidium; D017382:Reactive Oxygen Species / Q000378:metabolism; D020298:U937 Cells
chemical_list: D017304:Annexin A5; D000972:Antineoplastic Agents, Phytogenic; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D007202:Indicators and Reagents; D017382:Reactive Oxygen Species; D011419:Propidium; D045304:Cytochromes c; D007770:L-Lactate Dehydrogenase; D017239:Paclitaxel