One concept of improving anticancer effects of conventional platinum-based antitumor drugs consists of conjugating these compounds with other biologically (antitumor) active agents, acting by a different mechanism. Here, we present synthesis, physicochemical characterization, biological effects, and mechanisms of action of four new analogs of conventional cisplatin, namely, cis-Pt(II) complexes containing either methyl or ethyl pyrazole N-donor ligands and chlorido or iodido ligands. It is noteworthy that while chlorido complexes display activity in a variety of cancer cell lines comparable to cisplatin, iodido complexes are considerably more potent due to their enhanced hydrophobicity and consequently enhanced cellular accumulation. Moreover, all of the studied Pt(II) alkylpyrazole complexes display a higher selectivity for tumor cells and effectively overcome the acquired resistance to cisplatin. Further results focused on the mechanism of action of the studied complexes and showed that in contrast to cisplatin and several platinum-based antitumor drugs, DNA damage by the investigated Pt(II)-alkylpyrazole complexes does not play a major role in their mechanism of action. Our findings demonstrate that inhibition of the tubulin kinesin Eg5, which is essential for forming a functional mitotic spindle, plays an important role in their mechanism of antiproliferative action.

• Publication type
• Journal Article MeSH

The global modification of mammalian and plasmid DNAs by the novel platinum compounds cis-[PtCl(2)(isopropylamine)(1-methylimidazole)] and trans-[PtCl(2)(isopropylamine)(1-methylimidazole)] and the reactivity of these compounds with reduced glutathione (GSH) were investigated in cell-free media using various biochemical and biophysical methods. Earlier cytotoxicity studies had revealed that the replacement of the NH(3) groups in cisplatin by the azole and isopropylamine ligands lowers the activity of cisplatin in both sensitive and resistant cell lines. The results of the present work show that this replacement does not considerably affect the DNA modifications by this drug, recognition of these modifications by HMGB1 protein, their repair, and reactivity of the platinum complex with GSH. These results were interpreted to mean that the reduced activity of this analog of cisplatin in tumor cell lines is due to factors that do not operate at the level of the target DNA. In contrast, earlier studies had shown that the replacement of the NH(3) groups in the clinically ineffective trans isomer (transplatin) by the azole and isopropylamine ligands results in a radical enhancement of its activity in tumor cell lines. Importantly, this replacement also markedly alters the DNA binding mode of transplatin, which is distinctly different from that of cisplatin, but does not affect reactivity with GSH. Hence, the results of the present work are consistent with the view and support the hypothesis systematically tested by us and others that platinum drugs that bind to DNA in a fundamentally different manner from that of conventional cisplatin may have altered pharmacological properties.

• MeSH
• Cell-Free System MeSH
• Circular Dichroism MeSH
• DNA chemistry   drug effects   MeSH
• Glutathione chemistry   drug effects   MeSH
• Culture Media chemistry   MeSH
• Humans MeSH
• Organoplatinum Compounds chemistry   pharmacology   MeSH
• Antineoplastic Agents chemistry   pharmacology   MeSH
• Spectrophotometry, Ultraviolet MeSH
• Stereoisomerism MeSH
• Binding Sites MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• dichloro(isopropylamine)(1-methylimidazole)diplatinum(II) MeSH Browser
• DNA MeSH
• Glutathione MeSH
• Culture Media MeSH
• Organoplatinum Compounds MeSH
• Antineoplastic Agents MeSH

Platinum(II) diam(m)ine complexes such as cisplatin are effective anticancer drugs but have accompanying side effects. We are exploring the design of platinum complexes with low toxicity that could be photoactivated selectively at the target site. We show here that the Pt(IV) azide complex cis, trans-[Pt(en)(N(3))(2)(OH)(2)] is unreactive towards DNA until irradiated with visible light. Transcription mapping studies of a 212-bp fragment of pSP73KB plasmid DNA treated with cis, trans-[Pt(en)(N(3))(2)(OH)(2)] and irradiated with visible light showed that the platination sites were similar to those observed for cisplatin, and were mainly in GG sequences. HPLC analysis of enzymatic digests of an irradiated sample of a 40-bp DNA duplex treated with the same complex also revealed preferential formation of GG cross-links. Since such DNA lesions are thought to be responsible for the induction of apoptosis in cancer cells by platinum drugs, the use of unreactive photoactivatable platinum pro-drugs may become an effective strategy for the design of a new generation of platinum anticancer complexes.

• MeSH
• DNA Adducts chemical synthesis   isolation & purification   MeSH
• Azides chemistry   MeSH
• Cisplatin chemistry   MeSH
• DNA chemistry   MeSH
• Photochemistry MeSH
• Photochemotherapy MeSH
• Transcription, Genetic MeSH
• Guanine chemistry   MeSH
• Antineoplastic Agents chemistry   MeSH
• Base Sequence MeSH
• Platinum Compounds chemistry   MeSH
• Chromatography, High Pressure Liquid MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA Adducts MeSH
• Azides MeSH
• Cisplatin MeSH
• DNA MeSH
• Guanine MeSH
• Antineoplastic Agents MeSH
• Platinum Compounds MeSH

Bifunctional polynuclear platinum compounds represent a novel class of metal-based antitumor drugs which are currently undergoing preclinical development. A typical agent is [(trans-PtCl(NH(3))(2))(2)H(2)N(CH(2))(4)NH(2)]Cl(2) (1,1/t,t), which coordinates to bases in DNA and forms various types of covalent crosslinks. It also forms a 1,2-d(GpG) intrastrand adduct, the equivalent of the major DNA lesion of 'classical' cisplatin. In the present study differential scanning calorimetry and spectroscopic techniques were employed to characterize the influence of this crosslink on the thermal stability and energetics of 20 bp DNA duplexes site-specifically modified by 1,1/t,t. Thermal denaturation data revealed that the crosslink of 1,1/t,t reduced thermal and thermodynamical stability of the duplex noticeably more than that of 'classical' cisplatin. The energetic consequences of the intrastrand crosslink at the d(GG) site are discussed in relation to the structural distortions induced by this adduct in DNA and to its recognition and binding by HMG domain proteins. It has been suggested that the results of the present work are consistent with different DNA binding modes of cisplatin and polynuclear bifunctional DNA-binding drugs, which might be relevant to their distinct biological effectiveness.

• MeSH
• DNA Adducts chemistry   genetics   metabolism   MeSH
• Circular Dichroism MeSH
• Cisplatin metabolism   MeSH
• Nucleic Acid Denaturation MeSH
• Calorimetry, Differential Scanning MeSH
• DNA-Binding Proteins chemistry   metabolism   MeSH
• Entropy MeSH
• Guanine metabolism   MeSH
• Mutagenesis, Site-Directed * MeSH
• Oligodeoxyribonucleotides chemistry   genetics   metabolism   MeSH
• Platinum chemistry   metabolism   MeSH
• High Mobility Group Proteins chemistry   metabolism   MeSH
• Antineoplastic Agents chemistry   metabolism   MeSH
• Cross-Linking Reagents chemistry   metabolism   MeSH
• Base Sequence MeSH
• Spectrophotometry, Ultraviolet MeSH
• Temperature MeSH
• Protein Structure, Tertiary MeSH
• Thermodynamics MeSH
• Binding Sites MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA Adducts MeSH
• Cisplatin MeSH
• DNA-Binding Proteins MeSH
• Guanine MeSH
• Oligodeoxyribonucleotides MeSH
• Platinum MeSH
• High Mobility Group Proteins MeSH
• Antineoplastic Agents MeSH
• Cross-Linking Reagents MeSH

Modifications of natural DNA and synthetic oligodeoxyribonucleotide duplexes in a cell-free medium by analogs of antitumor cisplatin containing enantiomeric amine ligands, such as cis-[PtCl(2)(RR-DAB)] and cis-[PtCl(2)(SS-DAB)] (DAB = 2,3-diaminobutane), were studied by various methods of molecular biophysics and biophysical chemistry. These methods include DNA binding studies by pulse polarography and atomic absorption spectrophotometry, mapping of DNA adducts using transcription assay, interstrand cross-linking assay using gel electrophoresis under denaturing conditions, differential scanning calorimetry, chemical probing, and bending and unwinding studies of the duplexes containing single, site-specific cross-link. The major differences resulting from the modification of DNA by the two enantiomers are the thermodynamical destabilization and conformational distortions induced in DNA by the 1,2-d(GpG) intrastrand cross-link. It has been suggested that these differences are associated with a different biological activity of the two enantiomers observed previously. In addition, the results of the present work are also consistent with the view that formation of hydrogen bonds between the carbonyl oxygen of the guanine residues and the "quasi equatorial" hydrogen of the cis amine in the 1, 2-d(GpG) intrastrand cross-link plays an important role in determining the character of the distortion induced in DNA by this lesion.

• MeSH
• DNA Adducts chemistry   MeSH
• Amines chemistry   MeSH
• Biophysics MeSH
• Biophysical Phenomena MeSH
• Cisplatin analogs & derivatives   chemistry   pharmacology   MeSH
• Calorimetry, Differential Scanning MeSH
• DNA chemistry   drug effects   genetics   MeSH
• Transcription, Genetic MeSH
• Nucleic Acid Conformation MeSH
• Ligands MeSH
• Molecular Sequence Data MeSH
• Antineoplastic Agents chemistry   pharmacology   MeSH
• Cross-Linking Reagents MeSH
• Base Sequence MeSH
• Cattle MeSH
• Stereoisomerism MeSH
• In Vitro Techniques MeSH
• Thermodynamics MeSH
• Binding Sites MeSH
• Animals MeSH
• Check Tag
• Cattle MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA Adducts MeSH
• Amines MeSH
• Cisplatin MeSH
• DNA MeSH
• Ligands MeSH
• Antineoplastic Agents MeSH
• Cross-Linking Reagents MeSH