Radical-induced DNA damage by cytotoxic square-planar copper(II) complexes incorporating o-phthalate and 1,10-phenanthroline or 2,2'-dipyridyl.
DNA-targeting copper(II) reagents have emerged as suitable drug candidates owing to the clinical success of the copper-activated, natural chemotherapeutic drug bleomycin. This agent and the synthetic chemical nuclease copper(II) bis-1,10-phenanthroline represent important templates for inorganic drug design owing to their ability to initiate free radical DNA scission. Herein, we report the synthesis and biological properties of 1:1:1 square-planar copper(II) complexes incorporating the dicarboxylate o-phthalate and 1,10-phenanthroline (1) or 2,2'-dipyridyl (2) ligands. Their broad-spectrum chemotherapeutic potential has been assessed at 24- and 96-h intervals, along with that of the clinical agent cisplatin, using breast (MCF-7), prostate (DU145), colon (HT29), and intrinsically cisplatin-resistant ovarian (SK-OV-3) human cancer cells. 1 represents a potent cytotoxic agent with IC(50) values ranging from 5.6 to 3.4μM across all cell lines, including SK-OV-3. The production of endogenous reactive oxygen species within SK-OV-3 cancer cells was monitored using the fluorophore 2',7'-dichlorodihydrofluorescin diacetate, and results indicate a concentration-dependent propensity toward ROS generation by 1 and 2 that mirrors their antitumoral behavior. DNA interaction studies, using fluorescence and viscosity measurements, were conducted in tandem with the DNA-targeting drugs actinomycin D and pentamidine, using calf thymus DNA, poly[d(A-T)(2)], and poly[d(G-C)(2)], with intercalation of 1 and 2 at the minor groove appearing to be the likely interaction mode. DNA cleavage reactions using superhelical plasmid DNA, in the presence of exogenous reductant, l-ascorbic acid, revealed excellent agreement between double-stranded DNA scission capability and antitumoral IC(50) concentration. The presence of double-strand DNA breaks (DSBs) was confirmed within SK-OV-3 cancer cells using immunodetection of γ-H2AX foci by confocal microscopy and flow cytometry, with complex 1 quantitatively producing superior numbers of DSBs compared with complex 2. Superoxide dismutase and catalase mimetic activity assays were conducted, and these activities are related to the ability of both complexes to cleave DNA through free radical generation.
School of Chemical Sciences and National Institute for Cellular Biotechnology, Dublin City University, Glasnevin, Dublin 9, Ireland. andrew.kellett@dcu.ie
Andrew
A
Kellett
Orla
O
Howe
Mark
M
O'Connor
Malachy
M
McCann
Bernadette S
BS
Creaven
Siobhán
S
McClean
Agnieszka
A
Foltyn-Arfa Kia
Alan
A
Casey
Michael
M
Devereux
D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001667:Binding, Competitive; D002374:Catalase / Q000737:chemistry; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D004247:DNA / Q000737:chemistry; D053903:DNA Breaks, Double-Stranded; D003609:Dactinomycin / Q000737:chemistry; D004354:Drug Screening Assays, Antitumor; D004996:Ethidium / Q000737:chemistry; D005434:Flow Cytometry; D005609:Free Radicals / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D020128:Inhibitory Concentration 50; D007364:Intercalating Agents / Q000737:chemistry; D018613:Microscopy, Confocal; D018716:Molecular Mimicry; D010419:Pentamidine / Q000737:chemistry; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000737:chemistry; D014783:Viscosity
D000970:Antineoplastic Agents; D056831:Coordination Complexes; D005609:Free Radicals; C468783:H2AX protein, human; D006657:Histones; D007364:Intercalating Agents; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D003609:Dactinomycin; D010419:Pentamidine; D004247:DNA; C427203:calf thymus DNA; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D004996:Ethidium; D002945:Cisplatin