title: KRIBB3, a novel microtubule inhibitor, induces mitotic arrest and apoptosis in human cancer cells.
abstract: KRIBB3 (5-(5-ethyl-2-hydroxy-4-methoxyphenyl)-4-(4-methoxyphenyl) isoxazole) inhibited cancer cell growth in vitro and in vivo. Flow cytometry studies showed that KRIBB3 caused cell cycle arrest at the G(2)/M phase and subsequent apoptosis. This was confirmed as accumulation of Cyclin B1 and cleavage of poly(ADP-ribose) polymerase (PARP) were detected. While transient inhibition by KRIBB3 led to reversible mitotic arrest, prolonged exposure to KRIBB3-induced apoptosis. Co-immunoprecipitation experiments showed that KRIBB3 initially induced association of inhibitory Mad2 with p55CDC (mammalian homologue of CDC20), an activator of APC/C (anaphase-promoting complex/cyclosome), suggesting that the mitotic spindle checkpoint was activated by KRIBB3. However, the level of this inhibitory complex of Mad2 with p55CDC was gradually decreased 24 h after KRIBB3 treatment, and was hardly detectable after 48 h, indicating some slipping of the mitotic checkpoint. Consistent with these observations, KRIBB3 activated the mitotic spindle checkpoint by disrupting the microtubule cytoskeleton. KRIBB3 was proven to be a tubulin inhibitor using in vitro polymerization assays and in vivo indirect immunofluorescence staining. The temporal pattern of Bax activation by KRIBB3 was similar to PARP cleavage, suggesting that Bax is a mediator of KRIBB3-dependent apoptosis. Furthermore, when KRIBB3 was administered intraperitoneally into nude mice at 50 mg/kg or 100 mg/kg, it inhibited 49.5 or 70.3% of tumor growth, respectively. These results suggest that KRIBB3 is a good drug candidate for cancer therapy.
authors.affiliation: Molecular Cancer Research Center, Korea Research Institute of Bioscience and Biotechnology, 52 Eoeun-dong Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: Ki Deok
authors.initials: KD
authors.lastname: Shin
authors.forename: Young Ju
authors.initials: YJ
authors.lastname: Yoon
authors.forename: Yeong-Rim
authors.initials: YR
authors.lastname: Kang
authors.forename: Kwang-Hee
authors.initials: KH
authors.lastname: Son
authors.forename: Hwan Mook
authors.initials: HM
authors.lastname: Kim
authors.forename: Byoung-Mog
authors.initials: BM
authors.lastname: Kwon
authors.forename: Dong Cho
authors.initials: DC
authors.lastname: Han
mesh_terms: D000818:Animals; D000840:Anisoles / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors; D006801:Humans; D007555:Isoxazoles / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008870:Microtubules / Q000187:drug effects*; D008938:Mitosis / Q000187:drug effects*; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C507623:5-(5-ethyl-2-hydroxy-4-methoxyphenyl)-4-(4-methoxyphenyl)isoxazole; D000840:Anisoles; D000970:Antineoplastic Agents; C494826:BAX protein, human; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D007555:Isoxazoles; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D051028:bcl-2-Associated X Protein