title: Ligand modulation of a dinuclear platinum compound leads to mechanistic differences in cell cycle progression and arrest.
abstract: Despite similar structures and DNA binding profiles, two recently synthesized dinuclear platinum compounds are shown to elicit highly divergent effects on cell cycle progression. In colorectal HCT116 cells, BBR3610 shows a classical G2/M arrest with initial accumulation in S phase, but the derivative compound BBR3610-DACH, formed by introduction of the 1,2-diaminocyclohexane (DACH) as carrier ligand, results in severe G1/S as well as G2/M phase arrest, with nearly complete S phase depletion. The origin of this unique effect was studied. Cellular interstrand crosslinking as assayed by comet analysis was similar for both compounds, confirming previous in vitro results obtained on plasmid DNA. Immunoblotting revealed a stabilization of p53 and concomitant transient increases in p21 and p27 proteins after treatment with BBR3610-DACH. Cell viability assays and cytometric analysis of p53 and p21 null cells indicated that BBR3610-DACH-induced cell cycle arrest was p21-dependent and partially p53-dependent. However, an increase in the levels of cyclin E was observed with steady state levels of CDK2 and Cdc25A, suggesting that the G1 block occurs downstream of CDK/cyclin complex formation. The G2/M block was corroborated with decreased levels of cyclin A and cyclin B1. Surprisingly, BBR3610-DACH-induced G1 block was independent of ATM and ATR. Finally, both compounds induced apoptosis, with BBR3610-DACH showing a robust PARP-1 cleavage that was not associated with caspase-3/7 cleavage. In summary, BBR3610-DACH is a DNA binding platinum agent with unique inhibitory effects on cell cycle progression that could be further developed as a chemotherapeutic agent complementary to cisplatin and oxaliplatin.
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, Richmond, VA 23298-0613, United States; Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298-0613, United States.
authors.forename: Vijay R
authors.initials: VR
authors.lastname: Menon
authors.forename: Erica J
authors.initials: EJ
authors.lastname: Peterson
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Valerie
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Farrell
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Povirk
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D020552:Comet Assay; D045325:HCT116 Cells; D006801:Humans; D008024:Ligands; D017671:Platinum Compounds / Q000494:pharmacology*
chemical_list: D008024:Ligands; D017671:Platinum Compounds; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins
keywords: (3,4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; 1,2-diaminocyclohexane; ATM; ATR; Apoptosis; Ataxia Telangiectasia Mutated; Ataxia Telangiectasia Mutated and Rad3 related; BrdU; BrdU (PubChem CID: 6035); CDK; Cell cycle; Chk1; Cisplatin (PubChem CID: 441203); DACH; DNA damage response; Dinuclear platinum compounds; Gray; Gy; Interstrand crosslinks; MTT; MTT (PubChem CID: 64965); PAGE; PARP; PBS; PCNA; PPC; PVDF; Propidium Iodide (PubChem CID: 104981); SDS; SYBR Green (PubChem CID: 56841760); bromodeoxyuridine; checkpoint kinase 1; cyclin dependent kinase; p53; phosphate buffered saline; poly (ADP-ribose) polymerase; polyacrylamide gel electrophoresis; polynuclear platinum complex; polyvinylidene difluoride; proliferating cell nuclear antigen; sodium dodecyl sulfate