title: MJ-29 inhibits tubulin polymerization, induces mitotic arrest, and triggers apoptosis via cyclin-dependent kinase 1-mediated Bcl-2 phosphorylation in human leukemia U937 cells.
abstract: We investigated the signaling pathways associated with microtubule interaction and apoptosis in U937 cells in vitro and in the U937 xenograft model in vivo by using 6-pyrrolidinyl-2-(2-hydroxyphenyl)-4-quinazolinone (MJ-29). MJ-29 induced growth inhibition and cell death of leukemia cell lines (U937, HL-60, K562, and KG-1) in a dose- and time-dependent manner but did not obviously impair the viability of normal cells (peripheral blood mononuclear cells and human umbilical vein endothelial cells). MJ-29 interacted with alpha- and beta-tubulin, inhibited tubulin polymerization both in vitro and in vivo, and disrupted microtubule organization. MJ-29 caused mitotic arrest by activating cyclin-dependent kinase 1 (CDK1)/cyclin B complex activity. MJ-29-induced growth inhibition and activation of CDK1 activity were significantly attenuated by roscovitine (CDK inhibitor) and CDK1 small interfering RNA (siRNA). Furthermore, MJ-29-induced Bcl-2 phosphorylation was also significantly attenuated by CDK1 siRNA. MJ-29 caused an increase in the protein levels of cytosolic cytochrome c, apoptotic protease-activating factor-1, procaspase-9, and apoptosis-inducing factor. MJ-29-promoted activation of caspase-9 and caspase-3 during apoptosis was significantly attenuated by caspase-9 and caspase-3 inhibitors. It is noteworthy that in BALB/c(nu/nu) mice bearing U937 xenograft tumors MJ-29 inhibited tumor growth in vivo. The terminal deoxynucleotidyl transferase-mediated d-UTP nick end-labeling-positive apoptotic cells of tumor sections significantly increased in MJ-29-treated mice compared with the control group. In conclusion, our results suggest that MJ-29 induces mitotic arrest and apoptosis in U937 cells via CDK1-mediated Bcl-2 phosphorylation and inhibits the in vivo tumor growth of U937 xenograft mice.
authors.affiliation: Department of Pharmacology, China Medical University, Taichung, Taiwan.
authors.forename: Jai-Sing
authors.initials: JS
authors.lastname: Yang
authors.forename: Mann-Jen
authors.initials: MJ
authors.lastname: Hour
authors.forename: Wen-Wen
authors.initials: WW
authors.lastname: Huang
authors.forename: Kuei-Li
authors.initials: KL
authors.lastname: Lin
authors.forename: Sheng-Chu
authors.initials: SC
authors.lastname: Kuo
authors.forename: Jing-Gung
authors.initials: JG
authors.lastname: Chung
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001704:Biopolymers; D016203:CDC2 Protein Kinase / Q000502:physiology*; D053148:Caspase 3 / Q000096:biosynthesis; D053453:Caspase 9 / Q000096:biosynthesis; D004790:Enzyme Induction; D006801:Humans; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008938:Mitosis / Q000187:drug effects*; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D010865:Pilot Projects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D015398:Signal Transduction; D014183:Transplantation, Heterologous; D014404:Tubulin / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D000970:Antineoplastic Agents; D001704:Biopolymers; D019253:Proto-Oncogene Proteins c-bcl-2; D014404:Tubulin; D050257:Tubulin Modulators; D016203:CDC2 Protein Kinase; D053148:Caspase 3; D053453:Caspase 9