DNA Interactions of Monofunctional Organometallic Ruthenium(II) Antitumor Complexes in Cell-free Media

Modifications of natural DNA in a cell-free medium by antitumor monodentate Ru(II) arene compounds of the general formula [(eta 6-arene)Ru(en)Cl]+ (arene ) biphenyl, dihydroanthracene, tetrahydroanthracene, p-cymene, or benzene; en ) ethylenediamine) were studied by atomic absorption, melting behavior, transcription mapping, circular and linear dichroism, plasmid unwinding, competitive ethidium displacement, and differential pulse polarography. The results indicate that these complexes bind preferentially to guanine residues in double-helical DNA. The data are consistent with DNA binding of the complexes containing biphenyl, dihydroanthracene, or tetrahydroanthracene ligands that involves combined coordination to G N7 and noncovalent, hydrophobic interactions between the arene ligand and DNA, which may include arene intercalation and minor groove binding. In contrast, the single hydrocarbon rings in the p-cymene and benzene ruthenium complexes cannot interact with double-helical DNA by intercalation. Interestingly, the adducts of the complex containing p-cymene ligand, which has methyl and isopropyl substituents, distort the conformation and thermally destabilize double-helical DNA distinctly more than the adducts of the three multiring ruthenium arene compounds. It has been suggested that the different character of conformational alterations induced in DNA, and the resulting thermal destabilization, may affect differently further “downstream” effects of damaged DNA and consequently may result in different biological effects of this new class of metal-based antitumor compounds. The results point to a unique profile of DNA binding for Ru(II) arene compounds, suggesting that a search for new anticancer compounds based on this class of complexes may also lead to an altered profile of biological activity in comparison with that of metal-based antitumor drugs already used in the clinic or currently on clinical trials

NMR Study of the Interaction of Platinum Salts with a Tetrapeptide Containing Cysteinyl Residues

1H-, 13C- and 195Pt-NMR spectroscopies are used to identify the complexes formed between the platinum salts cis-(NH3)2PtCl2 (cis-DDP), trans-(NH3)2PtCl2 (trans-DDP), cis-(en)Pt(ONO2)2, and [(dien)PtBr]Br and the tetrapeptide Boc-Cys1(SMe)-Ser2-Ala3-Cys4(SMe)-CONH2 (CSAC) containing the sequence Cys-X-Y-Cys (X, Y = amino acids) and being a model of metallothionein (MT) and/or a model for platinum binding to methionine type sulfur, known to occur in biological systems. MT, rich in cysteine is known to bind both in vivo and in vitro with the antitumor drug cis-DDP. The 1H- and 13C-NMR assignments were made by two-dimensional homoand heteronuclear experiments for the ligand CSAC. The S-CH3 groups coordinate through sulfur to Pt(II) in all cases. The results show that cis-DDP forms a mixture of different diastereoisomers around the sulfur chiral centers and/or polymeric species with NH3 liberation, due to the strong trans-effect of sulfur. cis-Pt(en)(ONO2)2 forms a monomeric (1:1) chelate structure with CSAC, without en liberation, coordinated through both sulfur atoms. However, slow en liberation could take also place upon increasing temperature. Three signals are observed in the 1H- and 195Pt-NMR spectra of this complex in accordance with the proposed monomeric structure. trans-DDP, on the other hand, forms a 2:1 complex with CSAC identical to the one formed by [Pt(dien)Br]Br, both coordinated to the -S-CH3 groups. No amine release was observed in the case of these two complexes. © 1994, American Chemical Society. All rights reserved

Dichlorobis(cycloalkylamine)platinum(II) complexes. Structure activity relationship on the human MDA-MB-231 breast cancer cell line

The syntheses of dichlorobis(cycloalkylamine)platinum(II) complexes with cis and trans cycloalkylamine ligands [cis-PtCl2(C3H5NH2)2 to cis-PtCl2(C8H15NH2)2 and trans-PtCl2(C7H13NH2)2 and trans-PtCl2(C8H15NH2)2 are described. The distinction between cis and trans isomers was achieved by 1H-NMR spectroscopy. The antitumor activity was detd. on the cell proliferation of the human MDA-MB-231 breast cancer cell line during long-term drug exposure. The complexes with small cycloalkylamine ligands were inferior, those with large cycloalkylamine ligands were comparable or superior to cisplatin. All cycloalkylamine ligands were inactive. IR spectroscopic studies showed that the size of the cycloalkylamine ring does not lead to significant differences in the Pt-Cl binding strength. Therefore it is assumed that the markedly stronger antitumor activity of the higher homologs is not the result of a faster reaction with bionucleophiles such as DNA. A possible explanation of the high activity of some of the isomers is the strong lipophilicity of the complexes. This assumption was confirmed by toxicity tests against confluent cultures

Organometallic half-sandwich iridium anticancer complexes

The low-spin 5d6 IrIII organometallic half-sandwich complexes [(η5-Cpx)Ir(XY)Cl]0/+, Cpx = Cp*, tetramethyl(phenyl)cyclopentadienyl (Cpxph), or tetramethyl(biphenyl)cyclopentadienyl (Cpxbiph), XY = 1,10-phenanthroline (4−6), 2,2′-bipyridine (7−9), ethylenediamine (10 and 11), or picolinate (12−14), hydrolyze rapidly. Complexes with N,N-chelating ligands readily form adducts with 9-ethylguanine but not 9-ethyladenine; picolinate complexes bind to both purines. Cytotoxic potency toward A2780 human ovarian cancer cells increases with phenyl substitution on Cp*: Cpxbiph > Cpxph > Cp*; Cpxbiph complexes 6 and 9 have submicromolar activity. Guanine residues are preferential binding sites for 4−6 on plasmid DNA. Hydrophobicity (log P), cell and nucleus accumulation of Ir correlate with cytotoxicity, 6 > 5 > 4; they distribute similarly within cells. The ability to displace DNA intercalator ethidium bromide from DNA correlates with cytotoxicity and viscosity of Ir−DNA adducts. The hydrophobicity and intercalative ability of Cpxph and Cpxbiph make a major contribution to the anticancer potency of their IrIII complexes

Isolation and structure of the endogenous agonist of opioid receptor-like ORL1 receptor.

The ORL1 receptor, an orphan receptor whose human and murine complementary DNAs have recently been characterized, structurally resembles opioid receptors and is negatively coupled with adenylate cyclase. ORL1 transcripts are particularly abundant in the central nervous system. Here we report the isolation, on the basis of its ability to inhibit the cyclase in a stable recombinant CHO(ORL1+) cell line, of a neuropeptide that resembles dynorphin A9 and whose amino acid sequence is Phe-Gly-Gly-Phe-Thr-Gly-Ala-Arg-Lys-Ser-Ala-Arg-Lys-Leu-Ala-Asn-Gln. The rat-brain cDNA encodes the peptide flanked by Lys-Arg proteolytic cleavage motifs. The synthetic heptadecapeptide potently inhibits adenylate cyclase in CHO(ORL1+) cells in culture and induces hyperalgesia when administered intracerebroventricularly to mice. Taken together, these data indicate that the newly discovered heptadecapeptide is an endogenous agonist of the ORL1 receptor and that it may be endowed with pro-nociceptive properties.Journal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.SCOPUS: ar.jinfo:eu-repo/semantics/publishe