Development of a series of bis-triazoles as G-quadruplex ligands

Patel A., Lewis W., Searle M.S., Stevens M.F., Moody C.J.

The synthesis of a number of 6-arylisocytosines, including linked bis-isocytosines, from the reaction of guanidine with β-ketoesters is described. The compounds were investigated for their ability to form hydrogen-bonded structural networks, and for their potential interactions with the telomeric quadruplex forming sequence AGGG(TTAGGG)3.

Cini M., Bradshaw T.D., Lewis W., Woodward S.

The copper-catalysed (10 mol-% CuBr·SMe2, CuCN·LiCl or CuI/PPh3) addition of RMgBr to the pentafulvene 1-(cyclopenta-2,4-dien-1-ylidenemethyl)-2-methoxybenzene allows the formation of cyclopentadienyl derivatives with α-CHR(2-MeOPh) sidechains (R = Me, Et, nBu, iBu, allyl, Ph) without H– transfer. The deprotonation of these sec-alkyl-substituted cyclopentadienyls followed by the addition of TiCl4 allows the isolation of TiCl2{η5-C5H4CHR(2-OMePh)} as rac/meso mixtures that show activity against human colon, breast and pancreatic cell lines (GI50 2.3–42.4 μM).

Renčiuk D., Zhou J., Beaurepaire L., Guédin A., Bourdoncle A., Mergny J.

Some of the most serious diseases are characterized by the presence of a specific secondary structure within DNA or RNA, often in the promoter or the coding region of the responsible gene, that enhances or disrupts expression of the protein. Structural elements that impact cellular function may also be formed in other genomic regions such as telomeres. Compounds that interact with such structural elements may be useful in diagnosis or treatment of patients. In this report, we present a FRET melting assay that allows testing of libraries of compounds against four different nucleic acid structures. Compounds are tested to determine whether they stabilize preformed secondary structures (i.e., whether they cause an increase in melting temperature (T(m))). This property is described by the ΔT(m) parameter, which is the difference between the T(m) of the compound-stabilized structure and the T(m) of the unbound structure. Model oligonucleotides are labeled with FAM as a fluorescent donor and TAMRA as an acceptor. The intensity of FAM fluorescence is recorded as a function of temperature. Melting temperatures are determined by the FRET method in 96-well plates; this assay could easily be converted into 384-well format.

Gunaratnam M., Fuente M.D., Hampel S.M., Todd A.K., Reszka A.P., Schätzlein A., Neidle S.

The integrity of telomeres in most cancer cells is maintained by the action of the telomerase enzyme complex, which catalyzes the synthesis of telomeric DNA repeats in order to replace those lost during replication. Telomerase is especially up-regulated in metastatic cancer and is thus emerging as a major therapeutic target. One approach to telomerase inhibition involves the sequestration of the single-stranded 3' ends of telomeric DNA into higher-order quadruplex structures. We have recently shown that tetra-substituted naphthalene diimide compounds are potent quadruplex-stabilizing molecules with telomerase inhibitory activity in cells. We show here that one such compound, BMSG-SH-3, which has been optimized by computer modeling, has significant in vivo antitumor activity against a model for pancreatic cancer, a cancer that is especially resistant to current therapies. A large reduction in telomerase activity in treated tumors was observed and the naphthalene diimide compound was found to be selectively localized in the treated tumors. We find that the expression of the therapeutically important chaperone protein HSP90, a regulator of telomerase is also reduced in vivo by BMSG-SH-3 treatment. The compound is a potent stabilizer of two G-quadruplex sequences found in the promoter region of the HSP90 gene, as well as a G-quadruplex from human telomeric DNA. It is proposed that the simultaneous targeting of these quadruplexes may be an effective anti-tumor strategy.

Devarajan-Ketha H., Sloan K.B.

N,N'-Dialkylaminoalkylcarbonyl (DAAC) and aminoalkylcarbonyl (AAC) prodrugs of phenolic drugs acetaminophen (APAP) and naltrexone (NTX) are reported. The effects of incorporation of a basic amine group into the promoiety of an acyl prodrug of a phenolic drug on its skin permeation properties are also presented. DAAC-APAP prodrugs were synthesized via a three-step procedure starting with haloalkylcarbonyl esters which were reacted with five different amines: dimethylamine, diethylamine, dipropylamine, morpholine, and piperidine. The spacing between the amino group and the carbonyl group of the acyl group was 1-3 CH(2). After the hydrolysis of the ester, the carboxylic acid product was subsequently coupled with the parent drug via a dicyclohexyl carbodiimide (DCC) mediated coupling to yield the DAAC-APAP-HCl prodrugs in excellent yields. The AAC prodrugs were synthesized using commercially available Boc-protected amino acids using DCC or EDCI as coupling agents. The yields of the prodrugs synthesized using these two different methods have been compared. Half-lives (t(1/2)) of a few members of the DAAC and AAC series were measured in buffer (pH 6.0, 20mM). The members evaluated in hydrolysis experiments exhibit a t(1/2) range of 15-113min. Among AAC-APAP prodrugs, the isopropyl group in valinate-APAP-HCl exerted a steric effect that increased the t(1/2) value for this prodrug compared to alaninate-APAP-HCl or prolinate-APAP-HCl. The 2-morpholinylacetate-APAP prodrug was able to achieve twice the flux of APAP in in vitro diffusion cell experiments through hairless mouse skin.

Wang X., Wan K., Zhou C.

A series of novel sulfanilamide-derived 1,2,3-triazole compounds were synthesized in excellent yields via 1,3-dipolar cycloaddition and confirmed by MS, IR and NMR spectra as well as elemental analyses. All the compounds were screened in vitro for their antibacterial and antifungal activities. Preliminary results indicated that some target compounds exhibited promising antibacterial potency. Especially, 4-amino-N-((1-dodecyl-1H-1,2,3-triazol-4-yl)methyl) benzenesulfonamide, N-((1-(2,4-dichlorobenzyl)- 1H-1,2,3-triazol-4-yl)methyl)-4-aminobenzenesulfonamide and 4-amino-N-((1-(2,4-difluorobenzyl)- 1H-1,2,3-triazol-4-yl)methyl) benzenesulfonamide were found to be the most potent compounds against all the tested strains except for Candida albicans (ATCC76615) and Candida mycoderma.

Xu Y., Ishizuka T., Kurabayashi K., Komiyama M.

Garner T.P., Williams H.E., Gluszyk K.I., Roe S., Oldham N.J., Stevens M.F., Moses J.E., Searle M.S.

We report CD, ESI-MS and molecular modelling studies of ligand binding interactions with DNA quadruplex structures derived from the human telomeric repeat sequence (h-Tel) and the proto-oncogenic c-kit promoter sequence. These sequences form anti-parallel (both 2 + 2 and 3 + 1) and parallel conformations, respectively, and demonstrate distinctively different degrees of structural plasticity in binding ligands. With h-Tel, we show that an extended heteroaromatic 1,4-triazole (TRZ), designed to exploit pi-stacking interactions and groove-specific contacts, shows some selectivity for parallel folds, however, the polycyclic fluorinated acridinium cation (RHPS4), which is a similarly potent telomerase inhibitor, shows selectivity for anti-parallel conformations implicating favourable interactions with lateral and diagonal loops. In contrast, the unique c-kit parallel-stranded quadruplex shows none of the structural plasticity of h-Tel with either ligand. We show by quantitative ESI-MS analysis that both sequences are able to bind a ligand on either end of the quadruplex. In the case of h-Tel the two sites have similar affinities, however, in the case of the c-kit quadruplex the affinities of the two sites are different and ligand-dependent. We demonstrate that two different small molecule architectures result in significant differences in selectivity for parallel and anti-parallel quadruplex structures that may guide quadruplex targeted drug-design.

Campbell N.H., Patel M., Tofa A.B., Ghosh R., Parkinson G.N., Neidle S.

A series of disubstituted acridine ligands have been cocrystallized with a bimolecular DNA G-quadruplex. The ligands have a range of cyclic amino end groups of varying size. The crystal structures show that the diagonal loop in this quadruplex results in a large cavity for these groups, in contrast to the steric constraints imposed by propeller loops in human telomeric quadruplexes. We conclude that the nature of the loop has a significant influence on ligand selectivity for particular quadruplex folds.

Moorhouse A.D., Haider S., Gunaratnam M., Munnur D., Neidle S., Moses J.E.

Maintenance of telomeres--specialized complexes that protect the ends of chromosomes, is undertaken by the enzyme complex telomerase, which is a key factor that is activated in more than 80% of cancer cells, but is absent in most normal cells. Targeting telomere maintenance mechanisms could potentially halt tumour growth across a broad spectrum of cancer types, with little cytotoxic effect outside cancer cells. Here, we describe in detail a new class of G-quadruplex binding ligands synthesized using a click chemistry approach. These ligands comprise a 1,3-di(1,2,3-triazol-4-yl)benzene pharmacophore, and display high levels of selectivity for interaction with G-quadruplex DNA vs. duplex DNA. The ability of these ligands to inhibit the enzymatic activity of telomerase correlates with their ability to stabilize quadruplex DNA, and with estimates of affinity calculated by molecular modeling.

De Cian A., Lacroix L., Douarre C., Temime-Smaali N., Trentesaux C., Riou J., Mergny J.

Telomeres and telomerase represent, at least in theory, an extremely attractive target for cancer therapy. The objective of this review is to present the latest view on the mechanism(s) of action of telomerase inhibitors, with an emphasis on a specific class of telomere ligands called G-quadruplex ligands, and to discuss their potential use in oncology.

Monchaud D., Teulade-Fichou M.

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.

Phan A.T., Kuryavyi V., Luu K.N., Patel D.J.

Intramolecular G-quadruplexes formed by human telomere sequences are attractive anticancer targets. Recently, four-repeat human telomere sequences have been shown to form two different intramolecular (3 + 1) G-quadruplexes in K(+) solution (Form 1 and Form 2). Here we report on the solution structures of both Form 1 and Form 2 adopted by natural human telomere sequences. Both structures contain the (3 + 1) G-tetrad core with one double-chain-reversal and two edgewise loops, but differ in the successive order of loop arrangements within the G-quadruplex scaffold. Our results provide the structural details at the two ends of the G-tetrad core in the context of natural sequences and information on different loop conformations. This structural information might be important for our understanding of telomere G-quadruplex structures and for anticancer drug design targeted to such scaffolds.

DECIAN A., GUITTAT L., KAISER M., SACCA B., AMRANE S., BOURDONCLE A., ALBERTI P., TEULADEFICHOU M., LACROIX L., MERGNY J.

The telomeric G-rich single-stranded DNA can adopt in vitro an intramolecular quadruplex structure, which has been shown to directly inhibit telomerase activity. The reactivation of this enzyme in immortalized and most cancer cells suggests that telomeres and telomerase are relevant targets in oncology, and telomere ligands and telomerase inhibitors have been proposed as new potential anticancer agents. In this paper, we have analysed the FRET method used to measure the stabilization and selectivity of quadruplex ligands towards the human telomeric G-quadruplex. The stabilization value depends on the nature of the fluorescent tags, the incubation buffer, and the method chosen for T m calculation, complicating a direct comparison of the results obtained by different laboratories.

Al-Karmalawy A.A., Zeidan M.A., Elmaaty A.A., Sharaky M., Yassen A.S., Khaleel E.F., Eldehna W.M., Ashour H.F.

Zeidan M.A., Ashour H.F., Yassen A., Abo Elmaaty A., Farag A.B., Sharaky M., Abdullah Alzahrani A.Y., Mughram M.H., Al-Karmalawy A.A.

Many cancers have displayed resistance to chemotherapeutic drugs over the past few decades. EGFR has emerged as a leading target for cancer therapy via inhibiting tumor angiogenesis. Besides, studies strongly...

Abramovich Maxim S., Zaikina Polina V., Barskaya Elena S., Beloglazkina Elena K.

Nucleic acids are important targets for many anticancer drugs. Apart from the canonical B-DNA double helix, DNA forms a number of non-canonical structures (G-quadruplexes, i-motifs, hairpins, triplexes, etc.), which play an important role in the regulation of biological processes. Binding to non-canonical DNA structures occurs mainly by π–π-stacking. Therefore, aromatic and heteroaromatic compounds such as fused polyaromatic compounds (acridines, anthraquinones, carbazoles), porphyrins, benzothiazoles, benzimidazoles, pyridines, and quinolines, as well as their complexes are used as ligands for secondary structures. These ligands should possess not only high selectivity for non-canonical structures over double-stranded DNA, but also relatively high solubility and ability to penetrate through cell membranes. This review summarizes the achievements of 2020–2024 in the synthesis and biological studies of (hetero)arenes (acridines, anthraquinones, benzazoles, xanthones, porphyrins) and coordination compounds that have exhibited anticancer activity as a result of binding to non-canonical DNA or RNA structures. Ligands of various types of non-canonical nucleic acid structures (G-quadruplexes, i-motifs, triplexes, hairpins) are considered and their cytotoxic activity and structure–property relationships are comparedThe bibliography includes 166 references.

Al-Ali L., Al-Ani R.J., Saleh M.M., Hammad A.M., Abuarqoub D.A., Abu-Irmaileh B., Naser A.Y., Najdawi M.M., Abbas M.M., Alkrad J.A.

The use of tyrosine kinase inhibitors (TKIs) as a treatment for CML has improved the natural history of the disease and increased the duration of survival. Tyrosine kinase inhibitors represent the success of target therapies that work on molecular targets, although some patients still have therapy failure. Vitamin D has anti-proliferative, pro-apoptotic, and anti-angiogenic effects on cells, therefore it can be considered as a potential cancer preventative and treatment agent. Inecalcitol (TX-522) is the14-epi-analogue of Calcitriol (1,25(OH)2-vitamin D3), and inhibits cancer cell proliferation more effectively than Calcitriol. This study was conducted to evaluate the antiproliferative and synergistic effects of the anticancer drugs Imatinib and Dasatinib in combinations with Inecalcitol on human chronic myeloid leukemia K-562 cells. The growth inhibitory activities of Inecalcitol, Imatinib, Dasatinib, and different combinations of one of the two drugs (Imatinib and Dasatinib) with Inecalcitol, were determined in vitro using MTT assay against K-562 cell line. Inecalcitol, Imatinib, and Dasatinib showed potent antiproliferative activities against K-562 cells with GI50 values of 5.6 µM, 0.327 µM, and 0.446 nM, respectively. Combinations of Imatinib or Dasatinib with different concentrations of Inecalcitol increased significantly the antiproliferative activities and potencies of both drugs (****p < 0.0001), with optimal GI50 values of 580 pM (Imatinib) and 0.51 pM (Dasatinib). The study demonstrated that the human chronic myeloid leukemia K-562 cells were subjected to a synergistic growth inhibitory impact when antileukemic drugs (Imatinib or Dasatinib) were combined with Inecalcitol, therefore, it is recommended that these combinations be viewed as promising novel antileukemic medications and used in place of individual medications with lower dosages and negligible side effects in the treatment of CML.

Saleh M.M., Abuarqoub D.A., Hammad A.M., Hossan M.S., Ahmed N., Aslam N., Naser A.Y., Moody C.J., Laughton C.A., Bradshaw T.D.

Here, we describe the anticancer activity of our novel bis-triazoles MS47 and MS49, developed previously as G-quadruplex stabilizers, focusing specifically upon the human melanoma MDA-MB-435 cell line. At the National Cancer Institute (NCI), USA, bis-triazole MS47 (NCS 778438) was evaluated against a panel of sixty human cancer cell lines, and showed selective, distinct multi-log differential patterns of activity, with GI50 and LC50 values in the sub-micromolar range against human cancer cells. MS47 showed highly selective cytotoxicity towards human melanoma, ovarian, CNS and colon cancer cell lines; in contrast, the leukemia cell lines interestingly showed resistance to MS47 cytotoxic activity. Further studies revealed the potent cell growth inhibiting properties of MS47 and MS49 against the human melanoma MDA-MB-435 cell line, as verified by MTT assays; both ligands were more potent against cancer cells than MRC-5 fetal lung fibroblasts (SI > 9). Melanoma colony formation was significantly suppressed by MS47 and MS49, and time- and dose-dependent apoptosis induction was also observed. Furthermore, MS47 significantly arrested melanoma cells at the G0/G1 cell cycle phase. While the expression levels of Hsp90 protein in melanoma cells were significantly decreased by MS49, corroborating its binding to the G4-DNA promoter of the Hsp90 gene. Both ligands failed to induce senescence in the human melanoma cells after 72 h of treatment, corroborating their weak stabilization of the telomeric G4-DNA.

Al-Karmalawy A.A., Nafie M.S., Shaldam M.A., Elmaaty A.A., Antar S.A., El-Hamaky A.A., Saleh M.A., Elkamhawy A., Tawfik H.O.

Saleh M.M., Abuirmeileh A.N., Al-Rousan R.M., Abudoleh S.M., Hassouneh L.K., Zihlif M.A., Taha M.O., Abutayeh R.F., Mansour H., Abu-Irmaileh B.

Here, we describe further cytotoxic studies and reverse pharmacophore mapping (pharmacophore profiling) for bis-triazoles MS44-53, which were designed and synthesized previously to stabilize the G-quadruplex nucleic acids capable of being formed at the telomeric region and promoter sequences of genes involved in cellular proliferation and oncogenes. Pharmacophore-based activity profiling screen demonstrated some biological targets that MS44-53 may modulate their biological response, and thus can be considered as potential drugs to treat different kinds of diseases, such as carcinoma, diabetes type II, bacterial infection and cardiovascular diseases. Potent cell growth inhibitory properties were shown by ligands MS47 and MS49 against human melanoma MDA-MB-435, colon cancer HCT-116 and COLO 205, and pancreatic cancer MIA PaCa-2 cell lines, as evidenced by MTT assay. Both ligands were more potent against cancer cells than in skin normal CCD-1064Sk fibroblasts. Aim: The aim of this study is to identify the molecular target and mechanism of action of our promising anticancer bis-triazoles MS44-53, focusing specifically on the G-quadruplex stabilizers MS47 and MS49. Background: In molecular biology, G-quadruplexes (also known as G4-DNA), one of the higher-order structures of polynucleotides, are four stranded structures formed by nucleic acid sequences which are rich in guanine. They are formed mainly at the single-stranded G-overhang of telomeric DNA and within promoter sequences of genes involved in cellular proliferation and oncogenes such as c-myc, c-kit, and Hsp90. Stabilization of DNA G-quadruplexes is one of the anticancer strategies that has the potential to treat all cancers regardless of the type. A new series of bis-triazoles MS44-53 were developed to stabilize G-quadruplex structures selectively, as G4 ligands and experimental antitumour agents. FRET assay showed that MS47 and MS49 were only the best binders towards the Hsp90 promoter G-guadruplexes. While all bis-triazoles MS44-53 exhibited potent cell growth inhibitory activity against human carcinoma cell lines, suggesting that the ligands perturb molecular targets and mechanisms of action, other than stabilizing G-quadruplexes, contributing to antitumor activity. Therefore, the molecular targets and mechanisms of action of bis-triazoles MS44-53 in different types of human cancer cell lines should be determined by performing further computational studies to MS44-53 and in vitro evaluations for the G-quadruplex stabilizers MS47 and MS49. Objectives: 1- Determining the exact IC50 for bis-triazoles MS47 & MS49 against four different types of human cancer cell lines; melanoma MDA-MB-435, pancreatic cancer MIA PaCa-2, and colon cancer HCT-116 and COLO 205 cell lines. 2- Predicting the biological targets that bis-triazoles MS44-53 may interact with to trigger or block their biological response. Methods: 1- MTT assay was used for in vitro evaluation of the antiproliferative activities of MS47 and MS49, and determination of IC50 values. 2- Reverse pharmacophore mapping (pharmacophore profiling) was used for predicting the biological targets of bis-triazoles MS44-53, and determining the % binding probabilities. Results: MS49 exhibited more potent proliferation inhibitory activity than MS47 and higher IC50 value against skin normal fibroblasts. Pharmacophore profiling demonstrated FGFR1, PDGFR2, FLT3, mTOR, PPAR-gamma, MUR-F and CETP as biological targets for bis-triazoles MS44-53. Conclusion: Bis-triazoles MS47 and MS49 are promising selective innovative compounds with wide spectrum cytotoxic activities against distinct cancer types. Bis-triazoles MS44-53 can be considered as potential drugs to treat different types of carcinoma, in addition to diabetes type II, bacterial infection and cardiovascular diseases. Other: Further in vitro evaluations will be performed for bis-triazoles MS44-53 in order to identify their molecular targets and mechanisms of action in different types of human cancer cell lines.

Zell J., Duskova K., Chouh L., Bossaert M., Chéron N., Granzhan A., Britton S., Monchaud D.

Abstract DNA is intrinsically dynamic and folds transiently into alternative higher-order structures such as G-quadruplexes (G4s) and three-way DNA junctions (TWJs). G4s and TWJs can be stabilised by small molecules (ligands) that have high chemotherapeutic potential, either as standalone DNA damaging agents or combined in synthetic lethality strategies. While previous approaches have claimed to use ligands that specifically target either G4s or TWJs, we report here on a new approach in which ligands targeting both TWJs and G4s in vitro demonstrate cellular effects distinct from that of G4 ligands, and attributable to TWJ targeting. The DNA binding modes of these new, dual TWJ-/G4-ligands were studied by a panel of in vitro methods and theoretical simulations, and their cellular properties by extensive cell-based assays. We show here that cytotoxic activity of TWJ-/G4-ligands is mitigated by the DNA damage response (DDR) and DNA topoisomerase 2 (TOP2), making them different from typical G4-ligands, and implying a pivotal role of TWJs in cells. We designed and used a clickable ligand, TrisNP-α, to provide unique insights into the TWJ landscape in cells and its modulation upon co-treatments. This wealth of data was exploited to design an efficient synthetic lethality strategy combining dual ligands with clinically relevant DDR inhibitors.

Mitra A., Bhowmik S., Ghosh R.

G-quadruplex DNAs (G4 DNAs) are emerging as promising anticancer drug targets due to their presence in the promoter regions of different oncogenes. Utilizing different spectroscopic techniques like UV–Vis absorption titration, thermal denaturation, spectrofluorimetric titration, fluorescence displacement assay, Job plot analysis, circular dichroism spectroscopy and also, molecular docking studies, the interaction of a synthetic nitro-flavone, 2-(4-Nitrophenyl)-4H-chromen-4-one (4NCO), with various G4 DNA structures (c-KIT1, c-KIT2, c-MYC, h-TELO and VEGF) was elucidated. We also investigated the effect of 4NCO on different cancer cell lines. Effect on cell morphology, DNA damage, cell cycle arrest, viability and mode of cell death were evaluated in A375 melanoma cells. Our findings indicated that 4NCO showed preferential binding towards c-MYC promoter G4 to stabilize it with a binding constant (Kb) value of the order of ~105 M−1 and binding stoichiometry of ~1:1. It also showed a unique dual binding mode when bound to c-MYC with a lower binding free energy having multiple strong interactions when compared to the other G4s. In cells, it induced DNA damage resulting in cell cycle arrest at G1/S phase until 24 h, after which, cells strictly underwent apoptosis. It also showed a preferential cytotoxicity towards the A375 melanoma cells. The ability of 4NCO to stabilize the c-MYC G4 to possibly suppress the over-expression of MYC was responsible for inhibition of proliferation of these cells. Hence, these results present a novel finding on the effectiveness of the nitro-flavone derivative 4NCO as a potent ligand for c-MYC G4 DNA thereby, providing possibilities of its use in cancer therapy for regulating the oncogene expression in cancer cells.

Horchani M., Della Sala G., Caso A., D’Aria F., Esposito G., Laurenzana I., Giancola C., Costantino V., Jannet H.B., Romdhane A.

Chemotherapy represents the most applied approach to cancer treatment. Owing to the frequent onset of chemoresistance and tumor relapses, there is an urgent need to discover novel and more effective anticancer drugs. In the search for therapeutic alternatives to treat the cancer disease, a series of hybrid pyrazolo[3,4-d]pyrimidin-4(5H)-ones tethered with hydrazide-hydrazones, 5a–h, was synthesized from condensation reaction of pyrazolopyrimidinone-hydrazide 4 with a series of arylaldehydes in ethanol, in acid catalysis. In vitro assessment of antiproliferative effects against MCF-7 breast cancer cells, unveiled that 5a, 5e, 5g, and 5h were the most effective compounds of the series and exerted their cytotoxic activity through apoptosis induction and G0/G1 phase cell-cycle arrest. To explore their mechanism at a molecular level, 5a, 5e, 5g, and 5h were evaluated for their binding interactions with two well-known anticancer targets, namely the epidermal growth factor receptor (EGFR) and the G-quadruplex DNA structures. Molecular docking simulations highlighted high binding affinity of 5a, 5e, 5g, and 5h towards EGFR. Circular dichroism (CD) experiments suggested 5a as a stabilizer agent of the G-quadruplex from the Kirsten ras (KRAS) oncogene promoter. In the light of these findings, we propose the pyrazolo-pyrimidinone scaffold bearing a hydrazide-hydrazone moiety as a lead skeleton for designing novel anticancer compounds.

Singu P.S., Chilakamarthi U., Mahadik N.S., Keerti B., Valipenta N., Mokale S.N., Nagesh N., Kumbhare R.M.

A series of new benzimidazole-1,2,3-triazole hybrid derivatives have been synthesized via 'click' reaction and evaluated for their in vitro cytotoxicity as well as DNA binding affinity. MTT assay showed that all the six compounds are cytotoxic to PC3 and B16-F10 cancer cell lines. Though all the compounds showed moderate interaction with G4, c-Myc promoter DNA and dsDNA, 4f exhibited selective interaction with G-quadruplex DNA over duplex DNA as demonstrated by spectroscopic experiments like UV-vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, thermal melting and fluorescence lifetime experiments. They also confirm the G-quadruplex DNA stabilizing potential of 4f. Viscosity measurements also confirm that 4f exhibits high G-quadruplex DNA selectivity over duplex DNA. Docking studies supported the spectroscopic observations. Cell cycle analysis showed that 4f induces G2/M phase arrest and induces apoptosis. Hence, from these experimental results it is evident that compound 4f may be a G-quadruplex DNA groove binding molecule with anticancer activity.

Zhang W., Lu F., Zhang C., Guo Q., Quan H.

In this study, we synthesized hydrohalocyclobutenes through the dechlorination of hydrohalocyclobutanes in N,N -dimethylformamide and N,N -dimethylacetamide. The structure of the reaction site −CClR 1 −CClR 2 – (R 1 = H, F; R 2 = H, F, Cl) of the reactants was critical for the efficient reductive dechlorination from the 1- and 2- positions. The reaction proceeded efficiently at the –CFCl–CFCl–, –CFCl−CCl 2 –, and −CHCl−CHCl– groups. Conversely, the –CFCl−CHCl– group could hardly afford the dechlorinated product. Based on these results, we propose a rational reaction mechanism. • Amide solvent is rarely reported as a dechlorination reagent. • No metal catalyst was applied so that this approach was facile and mild. • Dechlorination proceeded efficiently at the –CFCl–CFCl–, –CFCl−CCl 2 –, and −CHCl−CHCl– groups located in the molecular structure of reactants. • The –CFCl−CHCl– group located in the molecular structure of reactants could hardly afford the dechlorinated product. • A series of hydrohalocyclobutenes were prepared with high selectivity. In this study, we synthesized hydrohalocyclobutenes through the dechlorination of hydrohalocyclobutanes in N,N -dimethylformamide and N,N -dimethylacetamide. The structure of the reaction site −CClR 1 −CClR 2 – (R 1 = H, F; R 2 = H, F, Cl) of the reactants was critical for the efficient reductive dechlorination from the 1- and 2- positions. The reaction proceeded efficiently at the –CFCl–CFCl–, –CFCl−CCl 2 –, and −CHCl−CHCl– groups. Conversely, the –CFCl−CHCl– group could hardly afford the dechlorinated product. Based on these results, we propose a rational reaction mechanism.