Conformational transition of DNA by dinuclear Pt(II) complexes causes cooperative inhibition of gene expression

Azolato-Bridged Dinuclear Platinum(II) Complexes Exhibit Androgen Receptor-Mediated Anti-Prostate Cancer Activity

Prostate cancer is an androgen-dependent malignancy that presents a marked treatment challenge, particularly after progression to the castration-resistant stage. Traditional treatments such as androgen deprivation therapy often lead to resistance, necessitating novel therapeutic approaches. Previous studies have indicated that some of the azolato-bridged dinuclear platinum(II) complexes (general formula: [{cis-Pt(NH3)2}2(μ-OH)(μ-azolato)]X2, where azolato = pyrazolato, 1,2,3-triazolato, or tetrazolato and X = nitrate or perchlorate) inhibit androgen receptor (AR) signaling. Therefore, here we investigated the potential of 14 such complexes as agents for the treatment of prostate cancer by examining their antiproliferative activity in the human prostate adenocarcinoma cell line LNCaP. Several of the complexes, particularly 5-H-Y ([{cis-Pt(NH3)2}2(μ-OH)(μ-tetrazolato-N2,N3)](ClO4)2), effectively inhibited LNCaP cell growth, even at low concentrations, by direct modulation of AR signaling, and by binding to DNA and inducing apoptosis, which is a common mechanism of action of Pt-based drugs such as cisplatin (cis-diamminedichloridoplatinum(II)). Comparative analysis with cisplatin revealed superior inhibitory effects of these complexes. Further investigation revealed that 5-H-Y suppressed mRNA expression of genes downstream from AR and induced apoptosis, particularly in cells overexpressing AR, highlighting its potential as an AR antagonist. Thus, we provide here insights into the mechanisms underlying the antiproliferative effects of azolato-bridged complexes in prostate cancer.

Quantitative evaluation of DNA double-strand breaks (DSBs) through single-molecule observation

By adapting the method of single molecular observation for individual DNAs, it will be shown that reliable analysis of double-strand breaks, DSBs, becomes possible for various kinds of damage sources. Single DNA above the size of several-tens kilo base-pairs exhibits the length scale above several μm, indicating that their whole conformation is visible with fluorescence microscopy by adding suitable fluoresce dye to the solution. Various examples of the quantitative evaluation on DSBs are described, together with the evaluation of the protective effects of anti-oxidants.

Data on synthesis and structure-activity relationships of tetrazolato-bridged dinuclear platinum(II) complexes

In this data file, the synthetic procedures for the preparation of a series of anticancer tetrazolato-bridged dinuclear platinum(II) complexes ([{cis-Pt(NH₃)₂}₂(μ-OH)(μ-5-R-tetrazolato-N2,N3)]ⁿ⁺ (n = 1 or 2, tetrazolato-bridged complexes)) and of the bridging ligands of 5-substituted 1H-tetrazoles (5-R-1H-tetrazoles) are described. These compounds were characterized by ¹H-, ¹³C-, ¹⁹F- and ¹⁹⁵Pt-NMR spectroscopy and mass spectrometry.

Different Effects of Cisplatin and Transplatin on the Higher-Order Structure of DNA and Gene Expression

Despite the effectiveness of cisplatin as an anticancer agent, its trans-isomer, transplatin, is clinically ineffective. Although both isomers target nuclear DNA, there is a large difference in the magnitude of their biological effects. Here, we compared their effects on gene expression in an in vitro luciferase assay and quantified their effects on the higher-order structure of DNA using fluorescence microscopy (FM) and atomic force microscopy (AFM). The inhibitory effect of cisplatin on gene expression was about 7 times that of transplatin. Analysis of the fluctuation autocorrelation function of the intrachain Brownian motion of individual DNA molecules showed that cisplatin increases the spring and damping constants of DNA by one order of magnitude and these visco-elastic characteristics tend to increase gradually over several hours. Transplatin had a weaker effect, which tended to decrease with time. These results agree with a stronger inhibitory effect of cisplatin on gene expression. We discussed the characteristic effects of the two compounds on the higher-order DNA structure and gene expression in terms of the differences in their binding to DNA.

Kinetic analysis of and platinum(II) migration in the reactions of tetrazolato-bridged dinuclear platinum(II) complexes with nucleotides

The series of tetrazolato-bridged complexes with the formula [{cis‑Pt(NH₃)₂}₂(μ-OH)(μ-5-H-tetrazolato-N1,N2)]²⁺ (5-H-X) or [{cis‑Pt(NH₃)₂}₂(μ-OH)(μ-5-R-tetrazolato-N2,N3)]ⁿ⁺ (R=H (5-H-Y), CH₃ (1), CH₂COOCH₂CH₃ (2), CH₂COO^- (3), n=2 (5-H-Y, 1, 2) or 1 (3)) are promising candidate complexes for formulation as next-generation platinum-based anticancer drugs that form multimodal bindings with DNA molecules. These multimodal bindings involve both non-covalent and covalent interactions, the latter of which are acknowledged to be essential for platinum-based drugs to exert their anticancer activity. In the present study, the tetrazolato-bridged complexes reacted with two molar equivalents of guanosine-5'-monophosphate (GMP) to yield the 1:2 reaction products [{cis‑Pt(NH₃)₂(GMP-N7)}₂(μ-5-R-tetrazolato-N1,N3)]^{2- or 1-}. This reaction was accompanied by an intramolecular Pt(II) migration that contributed to the formation of diverse DNA crosslinking, such as interhelical crosslinks. The second-order reaction rate constants for the reactions performed in phosphate-buffered D₂O solution showed that the reactivity of the complexes decreased in the order 5-H-X≳5-H-Y>2≳1>3 and that reactivity was correlated with the cytotoxicity of the complexes. A similar result was obtained for the reaction of the complexes with calf thymus DNA in which the formation of covalent DNA adducts was quantified by means of inductively coupled plasma mass spectrometry. These results suggest that overall charge affects the kinetics of the reactions of platinum complexes with GMP and calf thymus DNA. Thus, the positive charge of the complexes affects not only the non-covalent but also the covalent interactions between the complexes and nucleotides and DNA, which are negatively charged molecules.