title: Zinc(II)-Thiosemicarbazone Complexes Are Localized to the Lysosomal Compartment Where They Transmetallate with Copper Ions to Induce Cytotoxicity.
abstract: As the di-2-pyridylketone thiosemicarbazone (DpT) and 2-acetylpyridine thiosemicarbazone (ApT) series show potent antitumor activity in vitro and in vivo, we synthesized their fluorescent zinc(II) complexes to assess their intracellular distribution. The Zn(II) complexes generally showed significantly greater cytotoxicity than the thiosemicarbazones alone in several tumor cell-types. Notably, specific structure-activity relationships demonstrated the importance of the di-2-pyridyl pharmacophore in their activity. Confocal fluorescence imaging and live cell microscopy showed that the Zn(II) complex of our lead compound, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which is scheduled to enter clinical trials, was localized to lysosomes. Under lysosomal conditions, the Zn(II) complexes were shown to transmetallate with copper ions, leading to redox-active copper complexes that induced lysosomal membrane permeabilization (LMP) and cytotoxicity. This is the first study to demonstrate direct lysosomal targeting of our novel Zn(II)-thiosemicarbazone complexes that mediate their activity via transmetalation with copper ions and LMP.
authors.affiliation: Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, The University of Sydney , Blackburn Building (D06), Level 5, Sydney, New South Wales 2006, Australia.
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Stacy
authors.affiliation: Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, The University of Sydney , Blackburn Building (D06), Level 5, Sydney, New South Wales 2006, Australia.
authors.forename: Duraippandi
authors.initials: D
authors.lastname: Palanimuthu
authors.affiliation: School of Chemistry and Molecular Biosciences, University of Queensland , Brisbane, Queensland 4072, Australia.
authors.forename: Paul V
authors.initials: PV
authors.lastname: Bernhardt
authors.affiliation: Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, The University of Sydney , Blackburn Building (D06), Level 5, Sydney, New South Wales 2006, Australia.
authors.forename: Danuta S
authors.initials: DS
authors.lastname: Kalinowski
authors.affiliation: Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, The University of Sydney , Blackburn Building (D06), Level 5, Sydney, New South Wales 2006, Australia.
authors.forename: Patric J
authors.initials: PJ
authors.lastname: Jansson
authors.affiliation: Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, The University of Sydney , Blackburn Building (D06), Level 5, Sydney, New South Wales 2006, Australia.
authors.forename: Des R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D002463:Cell Membrane Permeability / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008247:Lysosomes / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013882:Thiosemicarbazones / Q000737:chemistry / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D009942:Organometallic Compounds; D013882:Thiosemicarbazones; D015032:Zinc