title: Phenoxazine derivatives 2-amino-4,4alpha-dihydro-4alpha-phenoxazine-3-one and 2-aminophenoxazine-3-one-induced apoptosis through a caspase-independent mechanism in human neuroblastoma cell line NB-1 cells.
abstract: The aim of the present study was to determine whether phenoxazines such as 2-amino-4,4-alpha-dihydro-4alpha-phenoxazine-3-one (Phx-1) and 2-aminophenoxazine-3-one (Phx-3) may suppress the proliferation of human neuroblastoma cell line, NB-1 that is refractory to chemotherapeutic agents, inducing apoptosis through the activation of caspase pathway or not. Phx-1 and Phx-3 suppressed the proliferation of NB-1 cells extensively dependent on dose and time. The IC50 of Phx-1 and Phx-3 was about 20 microM and 0.5 microM, respectively, when the cells were treated with Phx-1 or Phx-3 for 72 h. Phx-1 and Phx-3 caused the mixed types of cell death-apoptosis and necrosis-in NB-1 cells, which was detected by flow cytometry. The induction of apoptosis/necrosis caused by these phenoxazines seemed to be correlated dominantly with the caspase independent pathway, because the increased activity of effector caspase 3/7 in NB-1 cells caused by 50 microM Phx-1 or 20 microM Phx-3 was completely cancelled by the addition of z-VAD-fmk, a pan-caspase inhibitor, but such phenoxazines-suppressed viability of NB-1 cells was not recovered to normal levels by this inhibitor. The results of this study demonstrate that Phx-1 and Phx-3 have antitumor activity against the neuroblastoma cell line, NB-1, though the IC50 was extremely low for Phx-3, inducing the mixed types of cell death, apoptosis and necrosis, caspase-independently.
authors.affiliation: Laboratory of Physiological Sciences, Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Shirato
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Imaizumi
authors.forename: Akihisa
authors.initials: A
authors.lastname: Abe
authors.forename: Akio
authors.initials: A
authors.lastname: Tomoda
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D009336:Necrosis / Q000139:chemically induced; D009447:Neuroblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010078:Oxazines / Q000494:pharmacology*
chemical_list: C104202:2-amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one; D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D010078:Oxazines; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C005512:3-aminophenoxazone; D020169:Caspases