title: Bcl-2 overexpression attenuates SP600125-induced apoptosis in human leukemia U937 cells.
abstract: SP600125 is a specific inhibitor of c-Jun N-terminal kinase (JNK) that is known to strongly induce apoptosis and block cell cycle progression in G2/M phase. In this study, we demonstrated that treatment of U937 cells with SP600125 resulted in significant G2/M cell cycle arrest that was due to decreased cyclin B1 and cdc25c protein levels. Moreover, SP600125 promoted LDH release and DNA fragmentation that was associated with caspase-3 activation and degradation of its substrates. In contrast, overexpression of the antiapoptotic protein Bcl-2 rendered leukemia cells resistant to SP600125-induced apoptosis, but more sensitive to G2/M phase arrest and endoreduplication (>4N DNA). Overexpression of Bcl-2 significantly inhibited SP600125-induced caspase-3 activation and degradation of its substrates, and sustained expression levels of the IAP-2 proteins following SP600125 treatment. The inhibitory effect of Bcl-2 on apoptosis was attenuated by treatment with the small molecule Bcl-2 inhibitor, HA14-1. These data provide important mechanistic insights related to Bcl-2-mediated resistance to SP600125-induced apoptosis, and induction of G2/M phase arrest and endoreduplication.
authors.affiliation: Faculty of Applied Marine Science, Cheju National University, Jeju Special Self-Governing Province 690-756, South Korea.
authors.forename: Dong-Oh
authors.initials: DO
authors.lastname: Moon
authors.forename: Mun-Ock
authors.initials: MO
authors.lastname: Kim
authors.forename: Yung Hyun
authors.initials: YH
authors.lastname: Choi
authors.forename: Nam Deuk
authors.initials: ND
authors.lastname: Kim
authors.forename: Jeong-Hyun
authors.initials: JH
authors.lastname: Chang
authors.forename: Gi-Young
authors.initials: GY
authors.lastname: Kim
mesh_terms: D000873:Anthracenes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D007938:Leukemia / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D020298:U937 Cells; D015854:Up-Regulation
chemical_list: D000873:Anthracenes; D004791:Enzyme Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3