Synthesis and testing of a triaza-cyclopenta[b]phenanthrene scaffold as a DNA binding agent

TCH-1030 targeting on topoisomerase I induces S-phase arrest, DNA fragmentation, and cell death of breast cancer cells

Camptothecin (CPT) and its derivatives are powerful anticancer agents, but these compounds are chemically unstable due to their α-hydroxy lactone six-membered E-ring structure, which is essential for trapping topoisomerase I (topo I)-DNA cleavage complexes. Moreover, the reversibility of trapping the topo I-DNA cleavage complex and the tight binding of CPTs to human serum albumin limit the levels of available active drug. CPT analogs are the only clinically available drugs that target topo I. Owing to the clinical importance of CPT analogs, the development of new anticancer agents which inhibit topo I is urgently needed. In the present study, we report the synthesis, biologic evaluation, and molecular mechanism of a series of substituted indeno[1,2-c]quinoline derivatives against the growth of several human cancer cell lines. We found that 9-methoxy-6-(piperazin-1-yl)-11H-indeno[1,2-c]quinoline-11-one O-3-(dimethylamino)propyl oxime (TCH-1030) intercalated into DNA and preferentially inhibited DNA topo I relaxation. Flow cytometric analysis and BrdU incorporation assays indicate that TCH-1030 alters cell cycle progression, induces S-phase arrest, and causes DNA polyploidy (>4 N) that is distinct from the typical G2-M arrest reported with known topoisomerase toxins. Our data indicate that TCH-1030 induces caspase 3 activation, PARP cleavage, γ-H2AX phosphorylation, and, consequently, DNA fragmentation and apoptosis. We also demonstrated that treatment with TCH-1030 significantly inhibits tumor growth in a BT483-xenograft nude mouse model. Taken together, we conclude that the primary mechanism of action of TCH-1030-induced cell cycle retardation and apoptosis-mediated DNA damage involves DNA binding and intercalation as well as topo I inhibition.

Studies on DNA binding behaviour of biologically active transition metal complexes of new tetradentate N2O2 donor Schiff bases: inhibitory activity against bacteria

A series of Cu(II), Ni(II) and Zn(II) complexes of the type ML have been synthesized with Schiff bases derived from o-acetoacetotoluidide, 2-hydroxybenzaldehyde and o-phenylenediamine/1,4-diaminobutane. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the six metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff bases are found to act as tetradentate ligands using N(2)O(2) donor set of atoms leading to a square-planar geometry for the complexes around all the metal ions. The binding properties of metal complexes with DNA were investigated by absorption spectra, viscosity measurements and cyclic voltammetry. Detailed analysis reveals that the metal complexes intercalate into the DNA base stack as intercalators. All the metal complexes cleave the pUC19 DNA in presence of H(2)O(2.) The Schiff bases and their complexes have been screened for their antibacterial activity against five bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae) by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligands.

Study on the interaction of amino phosphine ester derivatives with DNA by spectroscopy, modeling and calorimetry

The binding properties of amino phosphate ester derivatives, compound 1 and 2 with calf thymus DNA (CT-DNA) were investigated by UV spectra, fluorescence spectra, molecular modeling and isothermal titration calorimetry (ITC). The intrinsic binding constants K(b) of compound 1 and 2 with CT-DNA were determined by fluorescence spectroscopy and ITC, respectively. The results indicated that the two compounds bind to CT-DNA with different binding affinity, which is in the order of compound 1>compound 2. At the same time, fluorescence spectra suggested that the mechanism of the binding of the two compounds to CT-DNA is a static enhancing type. According to the ethidium bromide displacement experiments, UV spectra, molecular modeling and ITC studies, it can be concluded that compound 1 and 2 are intercalators that can slide into the G-C rich region of CT-DNA. Furthermore, ITC data showed that compound/DNA binding is enthalpy controlled.

Exploring the Binding of Calothrixin A to the G-Quadruplex from the c-myc Oncogene Promotor

Calothrixin A, a bioactive pentacyclic metabolite from the cyanobacteria Calothrix, has potent antiproliferative behaviour against several cancer cell lines. The in vitro binding of calothrixin A to the DNA quadruplex formed at the promotor region of c-myc was investigated by monitoring changes in the fluorescence emission of 2-aminopurine (2Ap)-substituted analogues of the native Pu22 sequence d(TGAGGGTGGGGAGGGTGGGGAA) on titration with calothrixin A and N-methoxymethyl-calothrixin B. Calothrixin A binds to Pu22 and its constituent loop isomers with a micromolar dissociation constant whereas N-methoxymethyl-calothrixin B has over an order of magnitude lower affinity. Competitive displacement experiments with double-stranded DNA showed preferential binding of calothrixin A to the Pu22 quadruplex compared with double-stranded DNA. The association of calothrixin A with DNA quadruplexes is the first direct evidence that calothrixin A binds to DNA and may aid in the understanding of the bioactivity of the calothrixins.

A hitchhiker's guide to G-quadruplex ligands

Over the past decade, nucleic acid chemists have seen the spectacular emergence of molecules designed to interact efficiently and selectively with a peculiar DNA structure named G-quadruplex. Initially derived from classical DNA intercalators, these G-quadruplex ligands progressively became the focal point of new excitement since they appear to inhibit selectively the growth of cancer cells thereby opening interesting perspectives towards the development of novel anti-cancer drugs. The present article aims to help researchers enter this exciting research field, and to highlight recent advances in the design of G-quadruplex ligands.

Synthesis and evaluation of cationic phthalocyanine derivatives as potential inhibitors of telomerase

A series of water-soluble cationic phthalocyanine derivatives (1-10) were designed and synthesized to develop novel and potent telomerase inhibitors. These phthalocyanine derivatives as inhibitors of telomerase were investigated via modified telomerase repeat amplification protocol (TRAP) assay. The TRAP assay indicates that these cationic compounds had strong telomerase inhibitory activity (IC(50)<1.65 microM). To determine whether the phthalocyanine derivatives binding to G-quadruplex enhance the block to DNA synthesis, primer extension reactions were carried out in the presence of phthalocyanines. The interaction of the G-quadruplex of telomerase DNA with these molecules was examined by CD melting and PCR stop assay. These cationic phthalocyanine derivatives can stabilize G-quadruplex, which is demonstrated by the increased T(m) values. All these results indicate that the phthalocyanine derivatives might be potential lead compounds for the development of new telomerase inhibitor.