Heterocyclic Diamidine DNA Ligands as HOXA9 Transcription Factor Inhibitors: Design, Molecular Evaluation, and Cellular Consequences in a HOXA9-Dependant Leukemia Cell Model.

Most transcription factors were for a long time considered as undruggable targets because of the absence of binding pockets for direct targeting. HOXA9, implicated in acute myeloid leukemia, is one of them. To date, only indirect targeting of HOXA9 expression or multitarget HOX/PBX protein/protein interaction inhibitors has been developed. As an attractive alternative by inhibiting the DNA binding, we selected a series of heterocyclic diamidines as efficient competitors for the HOXA9/DNA interaction through binding as minor groove DNA ligands on the HOXA9 cognate sequence. Selected DB818 and DB1055 compounds altered HOXA9-mediated transcription in luciferase assays, cell survival, and cell cycle, but increased cell death and granulocyte/monocyte differentiation, two main HOXA9 functions also highlighted using transcriptomic analysis of DB818-treated murine Hoxa9-transformed hematopoietic cells. Altogether, these data demonstrate for the first time the propensity of sequence-selective DNA ligands to inhibit HOXA9/DNA binding both in vitro and in a murine Hoxa9-dependent leukemic cell model.

Amino substituted benzimidazo[1,2-a]quinolines: Antiproliferative potency, 3D QSAR study and DNA binding properties.

We describe the synthesis, 3D-derived quantitative structure-activity relationship (QSAR), antiproliferative activity and DNA binding properties of a series of 2-amino, 5-amino and 2,5-diamino substituted benzimidazo[1,2-a]quinolines prepared by environmentally friendly uncatalyzed microwave assisted amination. The antiproliferative activities were assessed in vitro against colon, lung and breast carcinoma cell lines; activities ranged from submicromolar to micromolar. The strongest antiproliferative activity was demonstrated by 2-amino-substituted analogues, whereas 5-amino and or 2,5-diamino substituted derivatives resulted in much less activity. Derivatives bearing 4-methyl- or 3,5-dimethyl-1-piperazinyl substituents emerged as the most active. DNA binding properties and the mode of interaction of chosen substituted benzimidazo[1,2-a]quinolines prepared herein were studied using melting temperature studies, a series of spectroscopic studies (UV/Visible, fluorescence, and circular dichroism), and biochemical experiments (topoisomerase I-mediated DNA relaxation and DNase I footprinting experiments). Both compound 36 and its bis-quaternary iodide salt 37 intercalate between adjacent base pairs of the DNA helix while compound 33 presented a very weak topoisomerase I poisoning activity. A 3D-QSAR analysis was performed to identify hydrogen bonding properties, hydrophobicity, molecular flexibility and distribution of hydrophobic regions as these molecular properties had the highest impact on the antiproliferative activity against the three cell lines.

Mixed up minor groove binders: Convincing A·T specific compounds to recognize a G·C base pair.

DNA minor-groove-binding compounds have limited biological applications, in part due to problems with sequence specificity that cause off-target effects. A model to enhance specificity has been developed with the goal of preparing compounds that bind to two AT sites separated by G·C base pairs. Compounds of interest were probed using thermal melting, circular dichroism, mass spectrometry, biosensor-SPR, and molecular modeling methods. A new minor groove binder that can strongly and specifically recognize a single G·C base pair with flanking AT sequences has been prepared. This multi-site DNA recognition mode offers novel design principles to recognize entirely new DNA motifs.

Novel phenyl and pyridyl substituted derivatives of isoindolines: Synthesis, antitumor activity and DNA binding features.

Novel phenyl-substituted (3a-3d, 4a, 5, 8a, 8b and 9a) and pyridyl-substituted (3e-3i, 4b, 8c-8e, 9b and 9c) isoindolines were prepared in the reaction of o-phthalaldehyde and corresponding substituted aromatic and heteroaromatic amines by modification of reaction conditions from low to high temperature and from neutral to acidic environment. The antiproliferative activity of chosen substituted isoindolines was assessed on a panel of tumour cell lines and normal human fibroblasts. The majority of tested compounds was active at the highest tested concentrations phenyl-substituted isoindolines 3a and 3b and pyridyl-substituted isoindoline 3g showed a selective effect at micromolar concentrations on HepG2 cell line in comparison with other tested tumour cell lines and normal human fibroblasts. The strongest yet non-selective effect was observed for the pyridyl-substituted isoindoline 8c. These isoindoline derivatives showed diverse mechanism of action on tumour cell death induction as compounds 3a and 8c probably induced mitotic catastrophe while compound 3b induced apoptosis. Indeed, DNA binding properties evidenced that compounds 8a, 8c and 8d bind to DNA as highly potent DNA intercalators. By contrast, compounds 3b, 3e, 3i, 4a and 5 did not target the DNA. At last, the phenyl-substituted compound 8b proved to be a strong DNA binding compound with sequence selective binding and without DNA intercalation profile.

Synthesis, antiproliferative activity and DNA binding properties of novel 5-aminobenzimidazo[1,2-a]quinoline-6-carbonitriles.

The synthesis of 5-amino substituted benzimidazo[1,2-a]quinolines prepared by microwave assisted amination from halogeno substituted precursor was described. The majority of compounds were active at micromolar concentrations against colon, lung and breast carcinoma cell lines in vitro. The N,N-dimethylaminopropyl 9 and piperazinyl substituted derivative 19 showed the most pronounced activity towards all of the three tested tumor cell lines, which could be correlated to the presence of another N heteroatom and its potential interactions with biological targets. The DNA binding studies, consisting of UV/Visible absorbency, melting temperature studies, and fluorescence and circular dichroism titrations, revealed that compounds 9, 19 and 20 bind to DNA as strong intercalators. The cellular distribution analysis, based on compounds' intrinsic fluorescence, showed that compound 20 does not enter the cell, while compounds 9 and 19 do, which is in agreement with their cytotoxic effects. Compound 9 efficiently targets the nucleus whereas 19, which also showed DNA intercalating properties in vitro, was mostly localised in the cytoplasm suggesting that the antitumor mechanism of action is DNA-independent.

Anilides and quinolones with nitrogen-bearing substituents from benzothiophene and thienothiophene series: synthesis, photochemical synthesis, cytostatic evaluation, 3D-derived QSAR analysis and DNA-binding properties.

A series of new anilides (2a-c, 4-7, 17a-c, 18) and quinolones (3a-b, 8a-b, 9a-b, 10-15, 19) with nitrogen-bearing substituents from benzo[b]thiophene and thieno[2,3-c]thiophene series are prepared. Benzo[b]thieno[2,3-c]- and thieno[3',2':4,5]thieno[2,3-c]quinolones (3a-b, 8a-b) are synthesized by the reaction of photochemical dehydrohalogenation from corresponding anilides. Anilides and quinolones were tested for the antiproliferative activity. Fused quinolones bearing protonated aminium group, quaternary ammonium group, N-methylated and protonated aminium group, amino and protonated amino group (8a, 9b, 10-12) showed very prominent anticancer activity, whereby the hydrochloride salt of N',N'-dimethylaminopropyl-substituted quinolone (14) was the most active one, having the IC50 concentration at submicromolar range in accordance with previous QSAR predictions. On the other hand, flexible anilides were among the less active. Chemometric analysis of investigated compounds was performed. 3D-derived QSAR analysis identified solubility, metabolitic stability and the possibility of the compound to be ionized at pH 4-8 as molecular properties that are positively correlated with anticancer activity of investigated compounds, while molecular flexibility, polarizability and sum of hydrophobic surface areas were found to be negatively correlated. Anilides 2a-b, 4-7 and quinolones 3a-b, 8a-b, 9b and 10-14 were evaluated for DNA binding propensities and topoisomerases I/II inhibition as part of their mechanism of action. Among the anilides, only compound 7 presented some DNA binding propensity whereas the quinolones 8b, 9b and 10-14 intercalate in the DNA base pairs, compounds 8b, 9b and 14 being the most efficient ones. The strongest DNA intercalators, compounds 8b, 9b and 14, were clearly distinguished from the other compounds according to their molecular descriptors by the PCA and PLS analysis.

Structure-dependent binding of arylimidamides to the DNA minor groove.

Heterocyclic diamidines are strong DNA minor-groove binders and have excellent antiparasitic activity. To extend the biological activity of these compounds, a series of arylimidamides (AIAs) analogues, which have better uptake properties in Leishmania and Trypanosoma cruizi than diamidines, was prepared. The binding of the AIAs to DNA was investigated by Tm , fluorescence displacement titration, circular dichroism, DNase I footprinting, biosensor surface plasmon resonance, X-ray crystallography and molecular modeling. These compounds form 1:1 complexes with AT sequences in the DNA minor groove, and the binding strength varies with substituent size, charge and polarity. These substituent-dependent structure and properties provide a SAR that can be used to estimate K values for binding to DNA in this series. The structural results and molecular modeling studies provide an explanation for the differences in binding affinities for AIAs.

New anticancer active and selective phenylene-bisbenzothiazoles: synthesis, antiproliferative evaluation and DNA binding.

Novel amidino-derivatives of phenylene-bisbenzothiazoles were synthesized and tested for their antiproliferative activity against several human cancer cell lines, as well as DNA-binding properties. The synthetic approach used for preparation of isomeric amidino substituted-phenylene-bis-benzothyazoles 3a-3f was achieved by condensation reaction of isophthaloyl dichloride 1a and terephthaloyl dichloride 1b or with phthalic acid 1c with 5-amidinium-2-aminobenzothiolate 2a and 5-(imidazolinium-2-yl)-2-aminobenzothiolate 2b in good yields. The targeted compounds were converted in the desired water soluble dihydrochloride salts by reaction of appropriate free base with concd HCl in ethanol or acetic acid. All tested compounds (3a-3f) showed antiproliferative effects on tumour cells in a concentration-dependant manner. The strongest activity and cytotoxicity was observed for diimidazolinyl substituted phenylene-bisbenzothiazole compound 3b. These effects were shown to be related to DNA-binding properties, topoisomerase I and II poisoning effects and apoptosis induction. The highest tested selectivity towards tumour cells was observed for the imidazolyl substituted phenylene-benzothiazole 3d that showed no cytotoxic effects on normal fibroblasts making it an excellent candidate for further chemical optimization and preclinical evaluation.

Targeting the DNA-binding activity of the human ERG transcription factor using new heterocyclic dithiophene diamidines.

Direct modulation of gene expression by targeting oncogenic transcription factors is a new area of research for cancer treatment. ERG, an ETS-family transcription factor, is commonly over-expressed or translocated in leukaemia and prostate carcinoma. In this work, we selected the di-(thiophene-phenyl-amidine) compound DB1255 as an ERG/DNA binding inhibitor using a screening test of synthetic inhibitors of the ERG/DNA interaction followed by electrophoretic mobility shift assays (EMSA) validation. Spectrometry, footprint and biosensor-surface plasmon resonance analyses of the DB1255/DNA interaction evidenced sequence selectivity and groove binding as dimer. Additional EMSA evidenced the precise DNA-binding sequence required for optimal DB1255/DNA binding and thus for an efficient ERG/DNA complex inhibition. We further highlighted the structure activity relationships from comparison with derivatives. In cellulo luciferase assay confirmed this modulation both with the constructed optimal sequences and the Osteopontin promoter known to be regulated by ERG and which ERG-binding site was protected from DNaseI digestion on binding of DB1255. These data showed for the first time the ERG/DNA complex modulation, both in vitro and in cells, by a heterocyclic diamidine that specifically targets a portion of the ERG DNA recognition site.

Novel substituted benzothiophene and thienothiophene carboxanilides and quinolones: synthesis, photochemical synthesis, DNA-binding properties, antitumor evaluation and 3D-derived QSAR analysis.

A series of new N,N-dimethylaminopropyl- and 2-imidazolinyl-substituted derivatives of benzo[b]thienyl- and thieno[2,3-b]thienylcarboxanilides and benzo[b]thieno[2,3-c]- and thieno[3',2':4,5]thieno[2,3-c]quinolones were prepared. Quinolones were prepared by the reaction of photochemical dehydrohalogenation of corresponding anilides. Carboxanilides and quinolones were tested for the antiproliferative activity. 2-Imidazolinyl-substituted derivatives showed very prominent activity. By use of the experimentally obtained antitumor measurements, 3D-derived QSAR analysis was performed for the set of compounds. Highly predictive 3D-derived QSAR models were obtained, and molecular properties that have the highest impact on antitumor activity were identified. Carboxanilides 6a-c and quinolones 9a-c and 11a were evaluated for DNA binding propensities and topoisomerases I and II inhibition as part of their mechanism of action assessment. The evaluated differences in the mode of action nicely correlate with the results of the 3D-QSAR analysis. Taken together, the results indicate which modifications of the compounds from the series should further improve their anticancer properties.

Water-mediated binding of agents that target the DNA minor groove.

Small molecule complexes with DNA that incorporate linking water molecules are rare, and the DB921-DNA complex has provided a unique and well-defined system for analysis of water-mediated binding in the context of a DNA complex. DB921 has a benzimidazole-biphenyl system with terminal amidines that results in a linear conformation that does not possess the appropriate radius of curvature to match the minor groove shape and represents a new paradigm that does not fit the classical model of minor groove interactions. To better understand the role of the bound water molecule observed in the X-ray crystal structure of the DB921 complex, synthetic modifications have been made in the DB921 structure, and the interactions of the new compounds with DNA AT sites have been evaluated with an array of methods, including DNase I footprinting, biosensor-surface plasmon resonance, isothermal titration microcalorimetry, and circular dichroism. The interaction of a key compound, which has the amidine at the phenyl shifted from the para position in DB921 to the meta position, has also been examined by X-ray crystallography. The detailed structural, thermodynamic, and kinetic results provide valuable new information for incorporation of water molecules in the design of new lead scaffolds for targeting DNA in chemical biology and therapeutic applications.

Synthesis and biological evaluation of N-substituted benzo[c]phenanthrolines and benzo[c]phenanthrolinones as antiproliferative agents.

Benzo[c]phenanthrolines and benzo[c]phenanthrolinones substituted by dialkylaminoalkyl side chains at position N5 and C6, respectively, were synthesised and their biological activity evaluated. They displayed interessant cytotoxicity associated with some DNA interactions. However, the low topoisomerase 1 affinity suggests that other cellular targets are responsible for the antiproliferative activity.

DNA minor groove induced dimerization of heterocyclic cations: compound structure, binding affinity, and specificity for a TTAA site.

With the increasing number and variations of genome sequences available, control of gene expression with synthetic, cell-permeable molecules is within reach. The variety of sequence-specific binding agents is, however, still quite limited. Many minor groove binding agents selectivity recognize AT over GC sequences but have less ability to distinguish among different AT sequences. The goal with this article is to develop compounds that can bind selectively to different AT sequences. A number of studies indicate that AATT and TTAA sequences have significantly different physical and interaction properties and different requirements for minor groove recognition. Although it has been difficult to get minor groove binding at TTAA, DB293, a phenyl-furan-benzimidazole diamidine, was found to bind as a strong, cooperative dimer at TTAA but with no selectivity over AATT. In order to improve selectivity, we made modifications to each unit of DB293. Binding affinities and stoichiometries obtained from biosensor-surface plasmon resonance experiments show that DB1003, a furan-furan-benzimidazole diamidine, binds strongly to TTAA as a dimer and has selectivity (K(TTAA)/K(AATT)=6). CD and DNase I footprinting studies confirmed the preference of this compound for TTAA. In summary, (i) a favorable stacking surface provided by the pi system, (ii) H-bond donors to interact with TA base pairs at the floor of the groove provided by a benzimidazole (or indole) -NH and amidines, and (iii) appropriate curvature of the dimer complex to match the curvature of the minor groove play important roles in differentiating the TTAA and AATT minor grooves.

Novel diamidino-substituted derivatives of phenyl benzothiazolyl and dibenzothiazolyl furans and thiophenes: synthesis, antiproliferative and DNA binding properties.

A series of new diamidino-, diisopropylamidino-, and diimidazolinyl-substituted derivatives of phenyl benzothiazolyl and dibenzothiazolyl furans and thiophenes were successfully prepared and evaluated for their antiproliferative activity on tumor cell lines in vitro, DNA binding propensity, and sequence selectivity as well as cellular distribution. A strong antiproliferative effect of the tested compounds was observed on all tested cell lines in a concentration-dependent response pattern. In general, imidazolinyl-substituted derivatives and/or the thiophene core were in correlation with increased antiproliferative activity. Two compounds (2b and 3b) were chosen for biological studies due to their differential antiproliferative properties. The DNA binding properties of this new series of compounds were assessed and evidenced their efficient minor groove binding properties with preferential interaction at AT-rich sites. Both compounds also present nuclear subcellular localization, suggesting that their cellular mode of action implies localization in the DNA compartment and direct inhibition of DNA replication and induction of apoptosis.