title: Kaempferol Activates G₂-Checkpoint of the Cell Cycle Resulting in G₂-Arrest and Mitochondria-Dependent Apoptosis in Human Acute Leukemia Jurkat T Cells.
abstract: The effect of kaempferol (3,5,7,4-tetrahydroxyflavone), a flavonoid compound that was identified in barnyard millet (Echinochloa crus-galli var. frumentacea) grains, on G2-checkpoint and apoptotic pathways was investigated in human acute leukemia Jurkat T cell clones stably transfected with an empty vector (J/Neo) or a Bcl-xL expression vector (J/Bcl-xL). Exposure of J/Neo cells to kaempeferol caused cytotoxicity and activation of the ATM/ATR-Chk1/Chk2 pathway, activating the phosphorylation of p53 (Ser-15), inhibitory phosphorylation of Cdc25C (Ser-216), and inactivation of cyclin-dependent kinase 1 (Cdk1), with resultant G2- arrest of the cell cycle. Under these conditions, apoptotic events, including upregulation of Bak and PUMA levels, Bak activation, mitochondrial membrane potential (Δψm) loss, activation of caspase-9, -8, and -3, anti-poly (ADP-ribose) polymerase (PARP) cleavage, and accumulation of apoptotic sub-G1 cells, were induced without accompanying necrosis. However, these apoptotic events, except for upregulation of Bak and PUMA levels, were completely abrogated in J/Bcl-xL cells overexpressing Bcl-xL, suggesting that the G2-arrest and the Bcl-xL-sensitive mitochondrial apoptotic events were induced, in parallel, as downstream events of the DNA-damage-mediated G2-checkpoint activation. Together these results demonstrate that kaempferol-mediated antitumor activity toward Jurkat T cells was attributable to G2-checkpoint activation, which caused not only G2-arrest of the cell cycle but also activating phosphorylation of p53 (Ser-15) and subsequent induction of mitochondriadependent apoptotic events, including Bak and PUMA upregulation, Bak activation, Δpsim loss, and caspase cascade activation.
authors.affiliation: Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
authors.forename: Ki Yun
authors.initials: KY
authors.lastname: Kim
authors.affiliation: Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
authors.forename: Won Young
authors.initials: WY
authors.lastname: Jang
authors.affiliation: Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Institute of Life Science and Biotechnology, Kyungpook National University, Daegu 41566, Republic of Korea.
authors.forename: Do Youn
authors.initials: do Y
authors.lastname: Jun
authors.affiliation: Nation Institute of Crop Science, Rural Development Administration, Miryang 50424, Republic of Korea.
authors.forename: Jee Youn
authors.initials: JY
authors.lastname: Ko
authors.affiliation: Nation Institute of Crop Science, Rural Development Administration, Miryang 50424, Republic of Korea.
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Yun
authors.affiliation: Laboratory of Immunobiology, School of Life Science and Biotechnology, College of Natural Sciences, Kyungpook National University, Daegu 41566, Republic of Korea.
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation; D031747:Echinochloa / Q000737:chemistry; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D006801:Humans; D019169:Jurkat Cells; D044949:Kaempferols / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009336:Necrosis; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051020:bcl-X Protein / Q000235:genetics; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; C494811:BCL2L1 protein, human; D044949:Kaempferols; D011518:Proto-Oncogene Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; C006552:kaempferol; D045304:Cytochromes c; D020687:cdc25 Phosphatases; D020169:Caspases
keywords: Antitumor activity; Bak activation; G2-checkpoint activation; caspase cascade; kaempferol; mitochondrial apoptosis