title: Prevalent loss of mitotic spindle checkpoint in adult T-cell leukemia confers resistance to microtubule inhibitors.
abstract: Human T-cell leukemia virus type I (HTLV-I) is the causative agent for adult T-cell leukemia (ATL). Molecularly, ATL cells have extensive aneugenic abnormalities that occur, at least in part, from cell cycle dysregulation by the HTLV-I-encoded Tax oncoprotein. Here, we compared six HTLV-I-transformed cells to Jurkat and primary peripheral blood mononuclear cells (PBMC) in their responses to treatment with microtubule inhibitors. We found that both Jurkat and PBMCs arrested efficiently in mitosis when treated with nocodazole. By contrast, all six HTLV-I cells failed to arrest comparably in mitosis, suggesting that ATL cells have a defect in the mitotic spindle assembly checkpoint. Mechanistically, we observed that in HTLV-I Tax-expressing cells human spindle assembly checkpoint factors hsMAD1 and hsMAD2 were mislocated from the nucleus to the cytoplasm. This altered localization of hsMAD1 and hsMAD2 correlated with loss of mitotic checkpoint function and chemoresistance to microtubule inhibitors.
authors.affiliation: Molecular Virology Section, Laboratory of Molecular Microbiology, NIAID, National Institutes of Health, Bethesda, Maryland 20892-0460, USA.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kasai
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Iwanaga
authors.forename: Hidekatsu
authors.initials: H
authors.lastname: Iha
authors.forename: Kuan-Teh
authors.initials: KT
authors.lastname: Jeang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D002460:Cell Line; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006367:HeLa Cells; D015368:Human T-lymphotropic virus 1 / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D015458:Leukemia, T-Cell / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D015739:Nocodazole / Q000494:pharmacology; D010641:Phenotype; D010880:Piperidines / Q000494:pharmacology; D011485:Protein Binding; D008941:Spindle Apparatus; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010880:Piperidines; C077990:alvocidib; D015739:Nocodazole