Nuclear DNA is the target responsible for anticancer activity of platinum anticancer drugs. Their activity is mediated by altered signals related to programmed cell death and the activation of various signaling pathways. An example is activation of nuclear factor kappaB (NF-κB). Binding of NF-κB proteins to their consensus sequences in DNA (κB sites) is the key biochemical activity responsible for the biological functions of NF-κB. Using gel-mobility-shift assays and surface plasmon resonance spectroscopy we examined the interactions of NF-κB proteins with oligodeoxyribonucleotide duplexes containing κB site damaged by DNA adducts of three platinum complexes. These complexes markedly differed in their toxic effects in tumor cells and comprised highly cytotoxic trinuclear platinum(II) complex BBR3464, less cytotoxic conventional cisplatin and ineffective transplatin. The results indicate that structurally different DNA adducts of these platinum complexes exhibit a different efficiency to affect the affinity of the platinated DNA (κB sites) to NF-κB proteins. Our results support the hypothesis that structural perturbations induced in DNA by platinum(II) complexes correlate with their higher efficiency to inhibit binding of NF-κB proteins to their κB sites and cytotoxicity as well. However, the full generalization of this hypothesis will require to evaluate a larger series of platinum(II) complexes.

• MeSH
• DNA Adducts chemistry   metabolism   MeSH
• Cisplatin chemistry   metabolism   pharmacology   MeSH
• HEK293 Cells MeSH
• Kinetics MeSH
• Coordination Complexes chemistry   metabolism   pharmacology   MeSH
• Consensus Sequence MeSH
• Humans MeSH
• NF-kappa B chemistry   genetics   metabolism   MeSH
• Oligodeoxyribonucleotides chemistry   metabolism   MeSH
• Organoplatinum Compounds chemistry   toxicity   MeSH
• Platinum chemistry   metabolism   MeSH
• Surface Plasmon Resonance MeSH
• Antineoplastic Agents chemistry   metabolism   pharmacology   MeSH
• Recombinant Proteins biosynthesis   chemistry   isolation & purification   MeSH
• Electrophoretic Mobility Shift Assay MeSH
• Thermodynamics MeSH
• Protein Binding MeSH
• Binding Sites MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• DNA Adducts MeSH
• BBR 3464 MeSH Browser
• Cisplatin MeSH
• Coordination Complexes MeSH
• NF-kappa B MeSH
• Oligodeoxyribonucleotides MeSH
• Organoplatinum Compounds MeSH
• Platinum MeSH
• Antineoplastic Agents MeSH
• Recombinant Proteins MeSH

Carboplatin, an analogue of "classical" cis-diamminedichloridoplatinum(II) (cisplatin), is a widely used second-generation platinum anticancer drug. Cytotoxicity of cisplatin and carboplatin is mediated by platinum-DNA adducts. Markedly higher concentrations of carboplatin are required, and the rate of adduct formation is considerably slower. The reduced toxic effects in tumor cells and a more acceptable side-effect profile are attributable to the lower reactivity of carboplatin with nucleophiles, since the cyclobutanedicarboxylate ligand is a poorer leaving group than the chlorides in cisplatin. Recently, platinum complexes were shown to be particularly attractive as potential photochemotherapeutic anticancer agents. Selective photoactivation of platinum complexes by irradiation of cancer cells may avoid enhancement of toxic side-effects, but may increase toxicity selectively in cancer cells and extend the application of photoactivatable platinum complexes to resistant cells and to a wider range of cancer types. Therefore, it was of interest to examine whether carboplatin can be affected by irradiation with light to the extent that its DNA binding and cytotoxic properties are altered. We have found that carboplatin is converted to species capable of enhanced DNA binding by UVA irradiation and consequently its toxicity in cancer cells is markedly enhanced. Recent advances in laser and fiber-optic technologies make it possible to irradiate also internal organs with light of highly defined intensity and wavelength. Thus, carboplatin is a candidate for use in photoactivated cancer chemotherapy.

• MeSH
• DNA chemistry   drug effects   MeSH
• Photochemical Processes radiation effects   MeSH
• Carboplatin chemistry   pharmacology   radiation effects   toxicity   MeSH
• Kinetics MeSH
• Humans MeSH
• Tumor Cells, Cultured MeSH
• Plasmids MeSH
• DNA Damage drug effects   MeSH
• Cell Proliferation drug effects   MeSH
• Antineoplastic Agents chemistry   pharmacology   radiation effects   toxicity   MeSH
• Drug Screening Assays, Antitumor MeSH
• Cattle MeSH
• Ultraviolet Rays MeSH
• Binding Sites drug effects   MeSH
• Cell Survival drug effects   MeSH
• Dose-Response Relationship, Drug MeSH
• Structure-Activity Relationship MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Cattle MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA MeSH
• Carboplatin MeSH
• Antineoplastic Agents MeSH

When antitumor platinum drugs react with DNA they form various types of intrastrand and interstrand cross-links (CLs). One class of new antitumor platinum compounds comprises bifunctional Pt(II) compounds based on the dinuclear or trinuclear geometry of leaving ligands. It has been shown that the DNA-binding modes of dinuclear or trinuclear bifunctional Pt(II) agents are distinct from those of mononuclear cisplatin, forming markedly more intramolecular interstrand CLs. However, at least two types of DNA interstrand cross-linking by bifunctional Pt(II) complexes can be envisaged, depending on whether the platinum complex coordinates to the bases in one DNA molecule (intramolecular interstrand CLs) or in two different DNA duplexes (interduplex CLs). We hypothesized that at least some antitumor bifunctional poly(di/tri)nuclear complexes could fulfill the requirements placed on interduplex DNA cross-linkers. To test this hypothesis we studied the interduplex cross-linking capability of a representative of antitumor polynuclear agents, namely, dinuclear Pt(II) complex [{trans-PtCl(NH(3))(2)}(2)-μ-{trans-(H(2)N(CH(2))(6)NH(2)(CH(2))(2)NH(2)(CH(2))(6)NH(2))}](4+) (BBR3535). The investigations were conducted under molecular crowding conditions mimicking environmental conditions in the cellular nucleus, namely, in medium containing ethanol, which is a commonly used crowding agent. We found with the aid of native agarose gel electrophoresis that the DNA interduplex cross-linking efficiency of BBR3535 under molecular crowding conditions was remarkable: the frequency of these CLs was 54%. In contrast, the interduplex cross-linking efficiency of mononuclear cisplatin or transplatin was markedly lower (approximately 40-fold or 18-fold, respectively). We suggest that the production of interduplex CLs in addition to other DNA intramolecular adducts may provide polynuclear Pt(II) compounds with a wider spectrum of cytotoxicity.

• MeSH
• DNA Adducts chemistry   metabolism   MeSH
• DNA chemistry   metabolism   MeSH
• Intercalating Agents chemistry   pharmacology   MeSH
• Humans MeSH
• Neoplasms drug therapy   MeSH
• Organoplatinum Compounds chemistry   pharmacology   MeSH
• Antineoplastic Agents chemistry   pharmacology   MeSH
• Cross-Linking Reagents chemistry   pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA Adducts MeSH
• DNA MeSH
• Intercalating Agents MeSH
• Organoplatinum Compounds MeSH
• Antineoplastic Agents MeSH
• Cross-Linking Reagents MeSH

The trinuclear BBR3464 ([{trans-PtCl(NH(3))(2)}(2)µ-(trans-Pt(NH(3))(2)(H(2)N(CH(2))(6)NH(2))(2))](4+)) belongs to the polynuclear class of platinum-based anticancer agents. DNA adducts of this complex differ significantly in structure and type from those of clinically used mononuclear platinum complexes, especially, long-range (Pt, Pt) intrastrand and interstrand cross-links are formed in both 5'-5' and 3'-3' orientations. We show employing short oligonucleotide duplexes containing single, site-specific cross-links of BBR3464 and gel electrophoresis that in contrast to major DNA adducts of clinically used platinum complexes, under physiological conditions the coordination bonds between platinum and N7 of G residues involved in the cross-links of BBR3464 can be cleaved. This cleavage may lead to the linkage isomerization reactions between this metallodrug and double-helical DNA. Differential scanning calorimetry of duplexes containing single, site-specific cross-links of BBR3464 reveals that one of the driving forces that leads to the lability of DNA cross-links of this metallodrug is a difference between the thermodynamic destabilization induced by the cross-link and by the adduct into which it could isomerize. The rearrangements may proceed in the way that cross-links originally formed in one strand of DNA can spontaneously translocate from one DNA strand to its complementary counterpart, which may evoke walking of the platinum complex on DNA molecule.

• MeSH
• DNA Adducts chemistry   MeSH
• Calorimetry, Differential Scanning MeSH
• DNA chemistry   MeSH
• Organoplatinum Compounds chemistry   MeSH
• Antineoplastic Agents chemistry   MeSH
• Cross-Linking Reagents chemistry   MeSH
• Thermodynamics MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA Adducts MeSH
• BBR 3464 MeSH Browser
• DNA MeSH
• Organoplatinum Compounds MeSH
• Antineoplastic Agents MeSH
• Cross-Linking Reagents MeSH

Reported herein is a detailed biochemical and molecular biophysics study of the molecular mechanism of action of antitumor dinuclear Pt(II) complex [{PtCl(DACH)}(2)-mu-Y](4+) [DACH=1,2-diaminocyclohexane, Y=H(2)N(CH(2))(6)NH(2)(CH(2))(2)NH(2)(CH(2))(6)NH(2)] (complex 1). This new, long-chain bifunctional dinuclear Pt(II) complex is resistant to metabolic decomposition by sulfur-containing nucleophiles. The results show that DNA adducts of 1 can largely escape repair and yet inhibit very effectively transcription so that they should persist longer than those of conventional cisplatin. Hence, they could trigger a number of downstream cellular effects different from those triggered in cancer cells by DNA adducts of cisplatin. This might lead to the therapeutic effects that could radically improve chemotherapy by platinum complexes. In addition, the findings of the present work make new insights into mechanisms associated with antitumor effects of dinuclear/trinuclear Pt(II) complexes possible.

• MeSH
• Cell-Free System MeSH
• DNA chemistry   MeSH
• Fluorescence MeSH
• Glutathione chemistry   MeSH
• Nucleic Acid Conformation * MeSH
• Molecular Sequence Data MeSH
• DNA Repair MeSH
• Organoplatinum Compounds chemistry   pharmacology   MeSH
• Antineoplastic Agents chemistry   pharmacology   MeSH
• Base Sequence MeSH
• Sulfur chemistry   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA MeSH
• Glutathione MeSH
• Organoplatinum Compounds MeSH
• Antineoplastic Agents MeSH
• Sulfur MeSH

The trinuclear platinum agent BBR3464, a representative of a new class of anticancer drugs, is more potent than conventional mononuclear cisplatin [cis-diamminedichloroplatinum(II)]. BBR3464 retains significant activity in human tumor cell lines and xenografts that are refractory or poorly responsive to cisplatin, and displays a high activity in human tumor cell lines that are characterized by both wild-type and mutant p53 gene. In contrast, on average, cells with mutant p53 are more resistant to the effect of cisplatin. It has been hypothesized that the sensitivity or resistance of tumor cells to cisplatin might be also associated with cell cycle control and repair processes that involve p53. DNA is a major pharmacological target of platinum compounds and DNA binding activity of the p53 protein is crucial for its tumor suppressor function. This study, using gel-mobility-shift assays, was undertaken to examine the interactions of active and latent p53 protein with DNA fragments and oligodeoxyribonucleotide duplexes modified by BBR3464 in a cell free medium and to compare these results with those describing the interactions of these proteins with DNA modified by cisplatin. The results indicate that structurally different DNA adducts of BBR3464 and cisplatin exhibit a different efficiency to affect the binding affinity of the modified DNA to p53 protein. It has been suggested that different structural perturbations induced in DNA by the adducts of BBR3464 and cisplatin produce a differential response to p53 protein activation and recognition and that a 'molecular approach' to control of downstream effects such as protein recognition and pathways of apoptosis induction may consist in design of structurally unique DNA adducts as cell signals.

• MeSH
• DNA Adducts chemistry   drug effects   genetics   metabolism   MeSH
• Cisplatin chemistry   pharmacology   MeSH
• Consensus Sequence genetics   MeSH
• Tumor Suppressor Protein p53 genetics   metabolism   MeSH
• Organoplatinum Compounds chemistry   pharmacology   MeSH
• Antineoplastic Agents chemistry   pharmacology   MeSH
• Response Elements genetics   MeSH
• Base Sequence MeSH
• Substrate Specificity MeSH
• Protein Binding MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Names of Substances
• DNA Adducts MeSH
• BBR 3464 MeSH Browser
• Cisplatin MeSH
• Tumor Suppressor Protein p53 MeSH
• Organoplatinum Compounds MeSH
• Antineoplastic Agents MeSH