Mitotic arrest induced by XK469, a novel antitumor agent, is correlated with the inhibition of cyclin B1 ubiquitination.
XK469 (NSC 697887) is a novel antitumor agent with broad activity against a variety of tumors. Previous studies suggest that XK469 is a topoisomerase II beta poison with functional activity similar to that of 4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA). The goal of our study was to investigate its mechanism of action further using a human HCT-116 (H116) colon tumor cell model. Concentration-survival curves with continuous exposure indicated that XK469 had low cytotoxic activity against H116 cells. Cell cycle analysis revealed that XK469 is a phase-specific cell cycle blocker that is associated with increased levels of cyclin B1, cyclin A and p53 but not CDK1 (cdc2) or cyclin E. In contrast, treatment of H116 cells with m-AMSA caused a total degradation of both cyclin A and B1 but enhanced expression of cyclin E and p53. Accumulation of cyclin B1 in XK469-treated cells was correlated with the inhibition of cyclin B1 ubiquitination, a metabolic process mandatory for proteasome-mediated protein turnover. However, no inhibition of cyclin B1 ubiquitination was detected in cells treated with m-AMSA or colchicine, a known mitotic inhibitor. Furthermore, unlike m-AMSA, XK469 did not induce caspase activation or apoptotic cell death in H116 cells. Our results suggest that XK469 is a phase-specific cell cycle inhibitor with a unique mechanism of action that is correlated with the inhibition of cyclin B1 ubiquitination and its accumulation at early M phase.
Lin
Hong
H
Division of Hematology-Oncology, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Liu
Xiang Y
XY
Subramanian
Balanehru
B
Nakeff
Alexander
A
Valeriote
Fred
F
Chen
Ben D
BD
D000677:Amsacrine / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology; D019926:Cyclin B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D056744:Cyclin B1; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D008938:Mitosis / Q000187:drug effects; D010447:Peptide Hydrolases / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology*; D008941:Spindle Apparatus / Q000187:drug effects*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D025801:Ubiquitin / Q000037:antagonists & inhibitors* / Q000378:metabolism
D000970:Antineoplastic Agents; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D011810:Quinoxalines; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; C118180:XK 469; D000677:Amsacrine; D010447:Peptide Hydrolases; D020169:Caspases