Phenyl 1,2,3-triazole-thymidine ligands stabilize G-quadruplex DNA, inhibit DNA synthesis and potentially reduce tumor cell proliferation over 3'-azido deoxythymidine

Withaferin A-Encapsulated PEGylated Nanoliposomes Induce Apoptosis in B16F10 Melanoma Cells by Regulating Bcl2 and Bcl xl Genes and Mitigates Murine Solid Tumor Development

Withaferin A (WA) is a natural steroidal lactone with promising pharmacological activities, but its poor solubility and bioavailability hinder its clinical application. The liposomal drug delivery system has attracted considerable attention to overcome the delivery limitations of pharmacological agents. The present study investigated the effect of WA-loaded pegylated nanoliposomes (LWA) on in vitro and in vivo B16F10 melanoma tumor models. In vitro results showed that LWA had significantly (P < 0.01) higher cytotoxicity than free WA and induced ROS-mediated apoptosis in B16F10 cells. Transwell cell migration and invasion studies demonstrated that LWA treatment significantly (P < 0.01) decreased the migratory and invasive capacities of melanoma cells compared with WA. In vivo study revealed that treatment significantly (P < 0.01) reduced tumor growth in experimental animals compared with WA or tumor control. Also, LWA administration remarkably inhibited tumor cell proliferation by downregulating the expression of Ki-67 and Cyclin D1 and induced apoptosis by regulating the expression of Bax, Bcl2, and Bcl xl levels. Our results strongly suggest that LWA could be a promising therapeutic formulation for treating malignant melanoma.

Design and Synthesis of Xanthone Analogues Conjugated with Aza-aromatic Substituents as Promising G-Quadruplex Stabilizing Ligands and their Selective Cancer Cell Cytotoxic Action

We have examined the stabilization of higher-order noncanonical G-quadruplex (G4) DNA structures formed by the G-rich sequences in the promoter region of oncogenes such as c-MYC, c-KIT, VEGF and BCl2 by newly synthesized, novel nitrogen-containing aromatics conjugated to xanthone moiety. Compounds with N-heterocyclic substituents such as pyridine (XNiso), benzimidazole (XBIm), quinoxaline (XQX) and fluorophore dansyl (XDan) showed greater effectiveness in stabilizing the G4 DNA as well as selective cytotoxicity for cancer cells (mainly A549) over normal cells both in terms of UV-Vis spectral titrations and cytotoxicity assay. Both fluorescence spectral titrimetric measurements and circular dichroism (CD) melting experiments further substantiated the G4 stabilization phenomenon by these small-molecular ligands. In addition, these compounds could induce the formation of parallel G4 structures in the absence of any added salt condition in Tris⋅HCl buffer at 25 °C. In a polymerase stop assay, the formation of stable G4 structures in the promoter of oncogenes and halting of DNA synthesis in the presence of the above-mentioned compounds was demonstrated by using oncogene promoter as the DNA synthesis template. Apoptosis-mediated cell death of the cancer cells was proved by Annexin V-PI dual staining assay and cell-cycle arrest occurred in the S phase of the cell cycles. The plausible mode of binding involves the stacking of the xanthone core on the G4 DNA plane with the possibility of interaction with the 5'-overhang as indicated by molecular dynamics simulation studies.

Developments in the Application of 1,2,3-Triazoles in Cancer Treatment

BACKGROUND

The impact of cancer on modern society cannot be emphasized enough in terms of both economic and human costs. Cancer treatments are known, unfortunately, for their side effects - frequently numerous and severe. Drug resistance is another issue medical professionals have to tackle when dealing with neoplastic illnesses. Cancer rates are rising worldwide due to various factors - low-quality nutrition, air and water pollution, tobacco use, etc. For those and many other reasons, drug discovery in the field of oncology is a top priority in modern medical science.

OBJECTIVE

To present the reader with the latest in cancer drug discovery with regard to 1,2,3-triazole- containing molecules in a clear, concise way so as to make the present review a useful tool for researchers.

METHODS

Available information present on the role of 1,2,3-triazoles in cancer treatment was collected. Data was collected from scientific literature, as well as from patents.

RESULTS

A vast number of triazole-containing molecules with antiproliferative properties have been proposed, synthesized and tested for anticancer activity both in vitro and in vivo. The substances vary greatly when considering molecular structure, proposed mechanisms of action and affected cancer cell types.

CONCLUSION

Triazole-containing molecules with anticancer activity are being widely synthesized and extensively tested. They vary significantly in terms of both structure and mechanism of action. The methods for their preparation and administration are well established and with proven reproducibility. These facts suggest that triazoles may play an important role in the discovery of novel antiproliferative medications with improved effectiveness and safety profile.

Synthesis and Antiviral Evaluation of Nucleoside Analogues Bearing One Pyrimidine Moiety and Two D-Ribofuranosyl Residues

A series of 1,2,3-triazolyl nucleoside analogues in which 1,2,3-triazol-4-yl-β-d-ribofuranosyl fragments are attached via polymethylene linkers to both nitrogen atoms of the heterocycle moiety (uracil, 6-methyluracil, thymine, quinazoline-2,4-dione, alloxazine) or to the C-5 and N-3 atoms of the 6-methyluracil moiety was synthesized. All compounds synthesized were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1) and coxsackievirus B3. Antiviral assays revealed three compounds, 2i, 5i, 11c, which showed moderate activity against influenza virus A H1N1 with IC₅₀ values of 57.5 µM, 24.3 µM, and 29.2 µM, respectively. In the first two nucleoside analogues, 1,2,3-triazol-4-yl-β-d-ribofuranosyl fragments are attached via butylene linkers to N-1 and N-3 atoms of the heterocycle moiety (6-methyluracil and alloxazine, respectively). In nucleoside analogue 11c, two 1,2,3-triazol-4-yl-2′,3′,5′-tri-O-acetyl-β-d-ribofuranose fragments are attached via propylene linkers to the C-5 and N-3 atoms of the 6-methyluracil moiety. Almost all synthesized 1,2,3-triazolyl nucleoside analogues showed no antiviral activity against the coxsackie B3 virus. Two exceptions are 1,2,3-triazolyl nucleoside analogs 2f and 5f, in which 1,2,3-triazol-4-yl-2′,3′,5′-tri-O-acetyl-β-d-ribofuranose fragments are attached to the C-5 and N-3 atoms of the heterocycle moiety (6-methyluracil and alloxazine respectively). These compounds exhibited high antiviral potency against the coxsackie B3 virus with IC₅₀ values of 12.4 and 11.3 µM, respectively, although both were inactive against influenza virus A H1N1. According to theoretical calculations, the antiviral activity of the 1,2,3-triazolyl nucleoside analogues 2i, 5i, and 11c against the H1N1 (A/PR/8/34) influenza virus can be explained by their influence on the functioning of the polymerase acidic protein (PA) of RNA-dependent RNA polymerase (RdRp). As to the antiviral activity of nucleoside analogs 2f and 5f against coxsackievirus B3, it can be explained by their interaction with the coat proteins VP1 and VP2.

G-quadruplexes: a promising target for cancer therapy

DNA and RNA can fold into a variety of alternative conformations. In recent years, a particular nucleic acid structure was discussed to play a role in malignant transformation and cancer development. This structure is called a G-quadruplex (G4). G4 structure formation can drive genome instability by creating mutations, deletions and stimulating recombination events. The importance of G4 structures in the characterization of malignant cells was currently demonstrated in breast cancer samples. In this analysis a correlation between G4 structure formation and an increased intratumor heterogeneity was identified. This suggests that G4 structures might allow breast cancer stratification and supports the identification of new personalized treatment options. Because of the stability of G4 structures and their presence within most human oncogenic promoters and at telomeres, G4 structures are currently tested as a therapeutic target to downregulate transcription or to block telomere elongation in cancer cells. To date, different chemical molecules (G4 ligands) have been developed that aim to target G4 structures. In this review we discuss and compare G4 function and relevance for therapeutic approaches and their impact on cancer development for three cancer entities, which differ significantly in their amount and type of mutations: pancreatic cancer, leukemia and malignant melanoma. G4 structures might present a promising new strategy to individually target tumor cells and could support personalized treatment approaches in the future.

Biogenic synthesis of biopolymer-based Ag-Au bimetallic nanoparticle constructs and their anti-proliferative assessment

This study reports an eco-friendly-based method for the preparation of biopolymer Ag-Au nanoparticles (NPs) by using gum kondagogu (GK; Cochlospermum gossypium), as both reducing and protecting agent. The formation of GK-(Ag-Au) NPs was confirmed by UV-absorption, fourier transformed infrared (FTIR), atomic force microscopy (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The GK-(Ag-Au) NPs were of 1-12 nm in size. The anti-proliferative activity of nanoparticle constructs was assessed by MTT assay, confocal microscopy, flow cytometry and quantitative real-time polymerase chain reaction (PCR) techniques. Expression studies revealed up-regulation of p53, caspase-3, caspase-9, peroxisome proliferator-activated receptors (PPAR) PPARa and PPARb, genes and down-regulation of Bcl-2 and Bcl-x(K) genes, in B16F10 cells treated with GK-(Ag-Au) NPs confirming the anti-proliferative properties of the nanoparticles.

The application of click chemistry for targeting quadruplex nucleic acids

The Cu(i)-catalyzed azide and alkyne 1,3-dipolar cycloaddition (CuAAC), commonly known as the "click reaction", has emerged as a powerful and versatile synthetic tool that finds a broad spectrum of applications in chemistry, biology and materials science. The efficiency, selectivity and versatility of the CuAAC reactions have enabled the preparation of vast arrays of triazole compounds with biological and pharmaceutical applications. In this feature article, we outline the applications and future prospects of click chemistry in the synthesis and development of small molecules that target G-quadruplex nucleic acids and show promising biological activities. Furthermore, this article highlights the template-assisted in situ click chemistry for developing G-quadruplex specific ligands and the use of click chemistry for enhancing drug specificity as well as designing imaging and sensor systems to elucidate the biological functions of G-quadruplex nucleic acids in live cells.

New Fe(iii) and Co(ii) salen complexes with pendant distamycins: selective targeting of cancer cells by DNA damage and mitochondrial pathways

Minor groove binding distamycin like moieties were conjugated with core salens and the corresponding Fe(iii) and Co(ii) complexes were synthesized. Herein, we have shown efficient DNA minor groove binding specificities along with excellent DNA cleavage capacities with metallosalen conjugates. The metal complexes showed toxicity toward various cancer cells over normal cells with high specificity. Interestingly, the Co(ii) complexes exhibited greater activity than the Fe(iii) complexes in accordance with the stronger affinity of the former in the biophysical studies. Active DNA damage, and prominent nuclear condensation along with the release of cytochrome-c from the mitochondria unanimously showed that the metal complexes followed apoptotic pathways to induce cell death.

Antibacterial, tyrosinase, and DNA photocleavage studies of some triazolylnucleosides

In order to explore the biological potential, some synthesized triazolylnucleosides were evaluated for their antibacterial, tyrosinase and DNA photocleavage activities. Triazolylnucleosides (5-12) were screened against Staphylococcus aureus (ATCC 6538), gram-positive and Escherichia coli (ATCC 10536), gram-negative bacterial strains. Among the series, compound 9 exhibited a significant level of antibacterial activity against both strains at higher concentration in reference to the standard drug, Levofloxacin. Tyrosinase activity and inhibition of these compounds were also studied, and it has been found that compounds 8 and 11 displayed more than 50% inhibitory activity. In addition, six compounds (7-12) were evaluated for their DNA photocleavage activity. The compounds 8 and 12 exhibited excellent DNA photocleavage activity at a concentration of 10 μg and may be used as template for antitumor drugs in the future.

One-pot synthesis of a new 2-substituted 1,2,3-triazole 1-oxide derivative from dipyridyl ketone and isonitrosoacetophenone hydrazone: Nickel(II) complex, DNA binding and cleavage properties

An efficient and simple one-pot synthesis of a new 1,2,3-triazole-1-oxide via reaction between isonitrosoacetophenone hydrazone and dipyridyl ketone in the EtOH/AcOH at room temperature has been developed smoothly in high yield. The reaction proceeds via metal salt free, in-situ formation of asymmetric azine followed by cyclization to provide 1,2,3-triazole 1-oxide compound. It has been structurally characterized. The 1:1 ratio reaction of the 1,2,3-triazole 1-oxide ligand with nickel(II) chloride gives the mononuclear complex [Ni(L)(DMF)Cl₂], hexa-coordinated within an octahedral geometry. Characterization of the 1,2,3-triazole compound and its Ni(II) complex with FTIR, ¹H and ¹³C NMR, UV-vis and elemental analysis also confirms the proposed structures of the compounds. The interactions of the compounds with Calf thymus DNA (CT-DNA) have been investigated by UV-visible spectra and viscosity measurements. The results suggested that both ligand and Ni(II) complex bind to DNA in electrostatic interaction and/or groove binding, also with a slight partial intercalation in the case of ligand. DNA cleavage experiments have been also investigated by agarose gel electrophoresis in the presence and absence of an oxidative agent (H₂O₂). Both 1,2,3-triazole 1-oxide ligand and its nickel(II) complex show nuclease activity in the presence of hydrogen peroxide. DNA binding and cleavage affinities of the 1,2,3-triazole 1-oxide ligand is stronger than that of the Ni(II) complex.

Impact of linker between triazolyluracil and phenanthridine on recognition of DNA and RNA. Recognition of uracil-containing RNA

A phenanthridine-triazolyluracilyl multifunctional ligand, linked by a lysine–glycine peptide, binds to poly rA–poly rU with micromolar affinity and selective fluorescence response.

Novel pyrimidine-2,4-dione-1,2,3-triazole and furo[2,3-d]pyrimidine-2-one-1,2,3-triazole hybrids as potential anti-cancer agents: Synthesis, computational and X-ray analysis and biological evaluation

Regioselective 1,4-disubstituted 1,2,3-triazole tethered pyrimidine-2,4-dione derivatives (5-23) were successfully prepared by the copper(I)-catalyzed click chemistry. While known palladium/copper-cocatalyzed method based on Sonogashira cross-coupling followed by the intramolecular 5-endo-dig ring closure generated novel 6-alkylfuro[2,3-d]pyrimidine-2-one-1,2,3-triazole hybrids (24b-37b), a small library of their 5-alkylethynyl analogs (24a-37a) was synthesized and described for the first time by tandem terminal alkyne dimerization and subsequent 5-endo-trig cyclization, which was additionally corroborated with computational and X-ray crystal structure analyses. The nature of substituents on alkynes and thereof homocoupled 1,3-diynes predominantly influenced the ratio of the formed products in both pathways. In vitro antiproliferative activity of prepared compounds evaluated on five human cancer cell lines revealed that N,N-1,3-bis-(1,2,3-triazole)-5-bromouracil (5-7) and 5,6-disubstituted furo[2,3-d]pyrimidine-2-one-1,2,3-triazole 34a hybrids exhibited the most pronounced cytostatic acitivities against hepatocellular carcinoma (HepG2) and cervical carcinoma (HeLa) cells with higher potencies than the reference drug 5-fluorouracil. Cytostatic effect of pyrimidine-2,4-dione-1,2,3-triazole hybrid 7 in HepG2 cells could be attributed to the Wee-1 kinase inhibition and abolishment of sphingolipid signaling mediated by acid ceramidase and sphingosine kinase 1. Importantly, this compound proved to be a non-mitochondrial toxicant, which makes it a promising candidate for further lead optimization and development of a new and more efficient agent for the treatment of hepatocellular carcinoma.

Exploration of biological activities of alkyne arms containing Cu(ii) and Ni(ii) complexes: syntheses, crystal structures and DFT calculations

Several mononuclear Cu(ii) and Ni(ii) Schiff base (N,O-donor) complexes were synthesized and characterized. The binding ability with DNA and BSA and catecholase activity of the complexes were investigated.

Design and synthesis of 2'-deoxy-2'-[(1,2,3)triazol-1-yl]uridines using click chemistry approach

A series of novel nucleosides bearing a 1,2,3-triazole moiety at the 2'-position of the sugar moiety has been synthesized starting from 2'-azidouridine and using the copper (I)-catalyzed Huisgen-Sharpless-Meldal 1,3-dipolar cycloaddition reaction. The reactions proceeded in overall yield of 52-82% and gave almost exclusively the 1,4-disubstituted 1,2,3-triazoles. The 2'-azidouridine was synthesized from uridine in two steps, and reacted with a variety of differently substituted alkynes to give the desired 2'-triazole-substituted uridine derivatives.

Studies on non-covalent interaction of coumarin attached pyrimidine and 1-methyl indole 1,2,3 triazole analogues with intermolecular telomeric G-quadruplex DNA using ESI-MS and spectroscopy

In the present study, electrospray ionization mass spectrometry (ESI-MS) and spectroscopy have been used to evaluate the non-covalent interaction, stoichiometry, and selectivity of two synthetic coumarin-attached nucleoside and non-nucleoside 1,2,3-triazoles, namely, (1-(5-(hydroxymethyl)-4-(4-((2-oxo-2H-chromen-4-yloxy)methyl)-1H-1,2,3-triazol-1-yl)tetrahydro-furan-2-yl)5-methyl pyrimidine-2,4(1H,3H)-dione (Tr1) and 4-((1-((-1-methyl-1H-indol-2-yl)methyl)-1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (Tr2) with two different human telomeric intermolecular G-quadruplex DNA structures formed by d(T2AG3) and d(T2AG3)2 sequences. ESI-MS studies indicate that Tr1 specifically interacts with four-stranded intermolecular parallel quadruplex complex, whereas Tr2 interacts with two hairpin as well as four-stranded intermolecular parallel quadruplex complexes. UV-Visible spectroscopic studies suggest that Tr1 and Tr2 interact with G-quadruplex structure and unwind them. Job plots show that stoichiometry of ligand:quadruplex DNA is 1:1. Circular dichroism (CD) studies of G-quadruplex DNA and Tr1/Tr2 ligands manifest that they unfold DNA on interaction. Fluorescence studies demonstrate that ligand molecules intercalate between the two stacks of quadruplex DNA and non-radiative energy transfer occurs between the excited ligand molecules (donor) and quadruplex DNA (acceptor), resulting in enhancement of fluorescence emission intensity. Thus, these studies suggest that nucleoside and non-nucleoside ligands efficiently interact with d(T2AG3) and d(T2AG3)2 G-quadruplex DNA but the interaction is not alike with all kinds of quadruplex DNA, this is probably due to the variation in the pharmacophores and structure of the ligand molecules.