Subsidiary hydrogen bonding of intercalated anthraquinonic anticancer drugs to DNA phosphate

New approaches of PARP-1 inhibitors in human lung cancer cells and cancer stem-like cells by some selected anthraquinone-derived small molecules

Poly (ADP-ribose) polymerase-1 (PARP-1) and telomerase, as well as DNA damage response pathways are targets for anticancer drug development, and specific inhibitors are currently under clinical investigation. The purpose of this work is to evaluate anticancer activities of anthraquinone-derived tricyclic and tetracyclic small molecules and their structure-activity relationships with PARP-1 inhibition in non-small cell lung cancer (NSCLC) and NSCLC-overexpressing Oct4 and Nanog clone, which show high-expression of PARP-1 and more resistance to anticancer drug. We applied our library selected compounds to NCI's 60 human cancer cell-lines (NCI-60) in order to generate systematic profiling data. Based on our analysis, it is hypothesized that these drugs might be, directly and indirectly, target components to induce mitochondrial permeability transition and the release of pro-apoptotic factors as potential anti-NSCLC or PARP inhibitor candidates. Altogether, the most active NSC747854 showed its cytotoxicity and dose-dependent PARP inhibitory manner, thus it emerges as a promising structure for anti-cancer therapy with no significant negative influence on normal cells. Our studies present evidence that telomere maintenance should be taken into consideration in efforts not only to overcome drug resistance, but also to optimize the use of telomere-based therapeutics. These findings will be of great value to facilitate structure-based design of selective PARP inhibitors, in general, and telomerase inhibitors, in particular. Together, the data presented here expand our insight into the PARP inhibitors and support the resource-demanding lead optimization of structurally related small molecules for human cancer therapy.

NSC746364, NSC746365, and NSC746366: the spectra of cytotoxicity and molecular correlates of response to telomerase activity

NSC746364, NSC746365, and NSC746366 are structurally novel 2,7-diamidoanthraquinone derivatives compared with other clinically used anticancer agents and have exhibited a unique multilog differential pattern of activity in our earlier studies. To systematically evaluate their potential anticancer activity, three selected compounds were tested for their cytotoxicity in vitro against 60 human cancer lines in the National Cancer Institute's anticancer drug screen as well as for dose response curves and telomerase activity. Cell growth was analyzed by the MTT assay, with differences between dose-response curves analyzed nonparametrically. Telomerase activity was detected by a modified version of the PCR-based assay and telomere repeat amplification protocol assay. To elucidate the structure-activity relationships and in-vitro anticancer activity, we correlated their activity profile [GI(50), total growth inhibition (TGI), and LC(50)] in the screening system and also their effects on telomerase activity, human telomerase reverse transcriptase expression, cell proliferations, and cytotoxicity. As a result we found that NSC746364, NSC746365, and NSC746366 have potent activity with 50% net growth inhibition conferred by 0.23-16.0 micromol/l (2.08 micromol/l mean); 0.78-15.9 micromol/l (2.57 micromol/l mean); 1.38-63.1 micromol/l (3.89 micromol/l mean), respectively. Sensitive cell lines exhibit TGI and 50% lethality to NSC746364, exhibited an LC(50) with as little as 2.82 micromol/l and TGI with as little as 0.95 micromol/l; NSC746365, exhibited an LC(50) with as little as 3.30 micromol/l, and TGI with as little as 1.65 micromol/l; NSC746366, exhibited an LC(50) with as little as 8.80 micromol/l; and TGI with as little as 4.06 micromol/l, respectively. Results of the study extend the initial in-vitro observation reported in the data above and confirm the importance of anticancer activity and telomerase inhibition. The unique molecular characterization, cytotoxicity, and telomerase activity profiles warrant further investigation and indicate a potential novel mechanism of anticancer action involved.

Synthesis and Biological Activity of Isoxazolidinyl Polycyclic Aromatic Hydrocarbons: Potential DNA Intercalators

Isoxazolidinyl polycyclic aromatic hydrocarbons (isoxazolidinyl-PAHs) have been synthesized in good yields by 1,3-dipolar cycloaddition methodology promoted by microwave irradiation. The structures of the obtained cycloadducts have been determined by NOE experiments and supported by computational studies at the AM1 level. The cytotoxicity and antiviral activity of the synthesized compounds have been investigated. In particular, compounds 7c and 7e show high levels of cytotoxicity on MOLT-3 leukemia cells; 7e exerts a remarkable enhancing activity on apoptosis caused by anti-fas antibody addition. Furthermore, compounds 7b and 8b exhibit specific antiviral effects against the Punta Toro virus.

Synthesis and cytotoxic activity of N,N-bis-(3-[N-(4-chlorobenzo[g]-phthalazin-1-yl)]aminopropyl)-N-methylamine: a new potential DNA bisintercalator

The synthesis of a new series of mono- and dinuclear 1-alkylamino-4-chlorobenzo[g]phthalazine derivatives 7-10 containing flexible polyaminic chains is reported. It has been achieved by the reaction of 1,4-dichlorobenzo[g]phthalazine with the corresponding polyamines. In vitro antitumoral activity against HT-29 human colon carcinoma cells was evaluated and showed best results for compound 10, in which two heteroaromatic units are linked by a N-methylsubstituted polyaminic chain. Molecular modelling of the complexes of 9 and 10 with DNA strongly suggests the possibility of bisintercalation, and also that the N-methyl group of 10 plays an important role in the formation of a specially stable DNA complex.

Phase transitions and hydrogen bonding in a bipolar phosphocholine evidenced by calorimetry and vibrational spectroscopy

As a model for natural archaebacterial bolalipids, we have synthesized omega-hydroxybehenylphosphocholine (HBPC, HO-(CH(2))(22)-OP(O(-)(2))O-(CH(2))(2)-N+(CH(3))(3)) and investigated it, by Fourier-transform infrared and Raman spectroscopy and differential scanning calorimetry, both as fully hydrated dispersions (varying temperature) and as aligned films (varying hydration) in terms of particular structural features predestining such bipolar lipids for their occurrence in extremophilic organisms. The phase behavior of HBPC in dispersions depends on sample pretreatment as it comprises metastabilities in annealed samples. However, main transition proceeds consistently near 81 degrees C. Some (extra) deal of headgroup (phosphate) hydration accompanying a gel-gel phase transition near 66 degrees C appears to precede chain melting. Studies with HBPC films revealed lamellar interdigitated-like solid phases with an extraordinarily strong omega-OH--OPO(-) omega-OH--OPO(-) omega-OH hydrogen-bond pattern formed along both sides of the resulting monolayers. The "clamping" effect inherent to such structures provides a clue to explain the relatively high main-transition temperature of HBPC assemblies.

NaDNA-bipyridyl-(ethylenediamine)platinum (II) complex: structure in oriented wet-spun films and fibers

Complexes of NaDNA with bipyridyl-(ethylenediamine)platinum(II) (abbreviated [(bipy)Pt(en)](2+)) in solid, oriented films, prepared with a wet-spinning method, have been studied using x-ray diffraction, elastic neutron scattering, two-dimensional magic-angle-spinning nuclear magnetic resonance (NMR), infrared (IR) linear dichroism, and IR absorption. All of these experiments indicate that the DNA in this complex is in the B conformation. The neutron diffraction experiments reveal that the rise per residue is 3.31 A, indicating that the [(bipy)Pt(en)](2+) molecular ion causes a small distortion of the B conformation. The neutron data in the direction perpendicular to the helical axis are consistent with a centered orthorhombic unit cell with a=22.65 A and b=32.2 A. The NMR and IR experiments show that the orientation of phosphate groups in the DNA small middle dot[(bipy)Pt(en)](2+) complex is the same as that observed for pure DNA in the B conformation. The IR experiments also show that the [(bipy)Pt(en)](2+) molecular ion stabilizes the B conformation of DNA down to 59% relative humidity, a low water activity. Mechanochemical experiments on wet-spun NaDNA fibers in 68% ethanol with and without [(bipy)Pt(en)](2+) reveal a 9% elongation of the DNA fibers as the complex is formed.

Electrostatic and non-electrostatic contributions to the binding free energies of anthracycline antibiotics to DNA

The knowledge about molecular factors driving simple ligand-DNA interactions is still limited. The aim of the present study was to investigate the electrostatic and non-electrostatic contributions to the binding free energies of anthracycline compounds with DNA. Theoretical calculations based on continuum methods (Poisson-Boltzmann and solvent accessible surface area) were performed to estimate the binding free energies of five selected anthracycline ligands (daunomycin, adriamycin, 9-deoxyadriamycin, hydroxyrubicin, and adriamycinone) to DNA. The free energy calculations also took into account the conformational change that DNA undergoes upon ligand binding. This conformational change appeared to be very important for estimating absolute free energies of binding. Our studies revealed that the absolute values of all computed contributions to the binding free energy were quite large compared to the total free energy of binding. However, the sum of these large positive and negative values produced a small negative value of the free energy around -10 kcal/mol. This value is in good agreement with experimental data. Experimental values for relative binding free energies were also reproduced for charged ligands by our calculations. Together, it was found that the driving force for ligand-DNA complex formation is the non-polar interaction between the ligand and DNA even if the ligand is positively charged.

Mutagenicity of cytostatic drugs in a bacterial system. I. Ames test

A set of nine cytostatic drugs were tested in the standard plate incorporation method of Ames reversion test using four Salmonella typhimurium his strains. Six of them were classical and commonly used cytostatics, three (cloturin, butocin and oracin) are at different stages of development. The results showed 6-mercaptopurine, cloturin, adriamycin, mitoxantron, cyclophosphamide and lomustine to be mutagenic; butocin, oracin and tris(2-chloroethyl)amine were negative in this test.

An A-form of poly[d(A-C)].poly[d(G-T)] induced by mercury (II) as studied by UV and FTIR spectroscopies

The conformational changes of poly[d(A-C)].poly[d(G-T)] induced by Hg(ClO4)2 in aqueous solution have been studied using UV absorption and fourth derivative spectrophotometries, and FTIR spectroscopy. The UV absorption and fourth derivative spectra reflect changes in the polynucleotide stacking interactions as a result of the metal-polynucleotide interaction. The fourth derivative spectra do not indicate a Z-form either at low or at high metal-to-polynucleotide ratios. Furthermore, the infrared spectrum at high metal-to-polynucleotide ratio (r = 1.2; r = [Hg(ClO4])2/[nucleotide] molar ratio) has the main features of an A-form, in contrast with previous CD studies which proposed that the polynucleotide adopts a Z-form under these conditions. The nature of a different conformation of the polynucleotide induced at low r-ratios (r < or = 0.2) is discussed.

Linear dichroism spectroscopy of nucleic acids

This review will consider solution studies of structure and interactions of DNA and DNA complexes using linear dichroism spectroscopy, with emphasis on the technique of orientation by flow. The theoretical and experimental background to be given may serve, in addition, as a general introduction into the state of the art of linear dichroism spectroscopy, particularly as it is applied to biophysical problems.