Guanine-rich sequences can form G-quadruplexes (G4) in living cells, making these structures promising anti-cancer targets. Compounds able to recognize these structures have been investigated as potential anticancer drugs; however, no G4 binder has yet been approved in the clinic. Here, we describe G4 ligands structure-activity relationships, in vivo effects as well as clinical trials. Addressing G4 ligand characteristics, targeting challenges, and structure-activity relationships, this review provides insights into the development of potent and selective G4-targeting molecules for therapeutic applications.
- MeSH
- antitumorózní látky * farmakologie terapeutické užití MeSH
- G-kvadruplexy * MeSH
- lidé MeSH
- ligandy MeSH
- nádory * farmakoterapie MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
G-quadruplex (G4) structures are non-canonical DNA/RNA secondary structures able to form within guanine rich nucleic acids sequences. They are present in several regions of the human genome including gene promoters, untranslated sequences, and telomeres. Due to their biological relevance G4 structures are considered important drug targets, in particular for anticancer therapies, leading to the development of G4 stabilizing small molecules. Telomeric regions have received special attention in this field since they can fold into several distinct intramolecular G-quadruplexes topologies. Herein, we report the synthesis of 2,9-disubstituted-1,10-phenanthroline derivatives and their ability to stabilize different intramolecular telomeric G4 sequences. We evaluated ligand-induced stabilization, selectivity and specificity of ligands using Förster Resonance Energy Transfer (FRET) melting experiments and circular dichroism (CD). In addition, we assessed the cytotoxicity of ligands against two cancer cell lines (A549 and H1299) and one healthy cell line (NHDF).
- MeSH
- cirkulární dichroismus MeSH
- DNA chemie MeSH
- fenantroliny MeSH
- G-kvadruplexy * MeSH
- guanin MeSH
- lidé MeSH
- ligandy MeSH
- RNA MeSH
- telomery MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
G-rich aptamers such as AS1411 are small oligonucleotides that present several benefits comparatively to monoclonal antibodies, since they are easier to manufacture and store, have small size and do not stimulate an immune response. We analyzed AT11-B1, a modified sequence of AT11 (itself a modified version of AS1411), in which one thymine was removed from the bulge region. We studied G-quadruplex (G4) formation/stabilization using PhenDC3, PDS, BRACO-19, TMPyP4 and 360A ligands by different biophysical techniques, namely circular dichroism (CD), Förster resonance energy transfer (FRET-melting) and nuclear magnetic resonance (NMR). The CD spectra showed that AT11-B1 adopts a predominant G4 of parallel topology when the buffer contains KCl or when ligands are added. PhenDC3 induced a ΔTm of 30 °C or more of the G4 structure as shown by CD- and FRET-melting experiments. The ligands demonstrate high affinity for AT11-B1 G4 and the NMR studies revealed that the AT11-B1 G4 involves four G-tetrad layers. The in silico studies suggest that all ligands bind AT11-B1 G4, namely, by stacking interactions, with the possible exception of PDS that may bind to the loop/groove interface. In addition, molecular dynamics simulations revealed that nucleolin (NCL) interacts with the AT11-B1 G4 structure through the RNA binding domain (RBD) 2 and the 12-residue linker between RBD1,2. Moreover, AT11-B1 G4 was internalized into a NCL-positive tongue squamous cell carcinoma cell line. In a nutshell, this study may help the identification of the ligands scaffolds to bind and stabilize AT11-B1, improving the targeting towards NCL that is overexpressed in cancer cells.
- MeSH
- aptamery nukleotidové * chemie MeSH
- G-kvadruplexy * MeSH
- lidé MeSH
- ligandy MeSH
- nádory jazyka * MeSH
- spinocelulární karcinom * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
A high level of nucleolin (NCL) expression is often associated with a poor prognosis of patients with lung cancer (LC), suggesting that NCL can be used as a possible biomarker. NCL has been shown to display a marked preference for the binding to G-quadruplexes (G4). Here, we investigate the formation of an RNA quadruplex structure in a sequence found in the human precursor pre-MIR150 with the potential to recognize NCL. Circular dichroism (CD) spectra of pre-MIR150 G4-forming sequence (designated by rG4) indicate the formation of a parallel quadruplex structure in KCl or when complexed with the well-known G4 ligand PhenDC3. The thermal stability of rG4 is very high, and further increases in the presence of PhenDC3. The binding affinities of rG4 to PhenDC3 and NCL RBD1,2 are similar with KD values in the nanomolar range. PAGE results suggest the formation of a ternary quadruplex-ligand-protein complex (rG4-PhenDC3-NCL RBD1,2), indicative that PhenDC3 does not prevent the binding of rG4 to NCL RBD1,2. Finally, rG4 can recognize NCL-positive cells and, when fluorescently labeled, can be used as a probe for this protein. ELISA experiments indicate altered NCL expression patterns in liquid biopsies of LC patients in a non-invasive manner, potentially helping the diagnosis, prognosis, and patient response to treatment. Hence, labeled rG4 could be used as a detection probe of LC in liquid biopsies.
- MeSH
- aminokyselinové motivy fyziologie MeSH
- dospělí MeSH
- fosfoproteiny biosyntéza genetika MeSH
- G-kvadruplexy * MeSH
- genový targeting metody MeSH
- kultivované buňky MeSH
- leukocyty mononukleární metabolismus MeSH
- lidé MeSH
- nádory plic genetika metabolismus terapie MeSH
- proteiny vázající RNA biosyntéza genetika MeSH
- regulace genové exprese u nádorů MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The G-quadruplex (G4)-forming sequence within the AS1411 derivatives with alternative nucleobases and backbones can improve the chemical and biological properties of AS1411. Zn(II) phthalocyanine (ZnPc) derivatives have potential as high-affinity G4 ligands because they have similar size and shape to the G-quartets. The interactions of four Zn(II) phthalocyanines with the G4 AS1411 aptamer and its derivatives were determined by biophysical techniques, molecular docking and gel electrophoresis. Cell viability assay was carried out to evaluate the antiproliferative effects of Zn(II) phthalocyanines and complexes. CD experiments showed structural changes after addition of ZnPc 4, consistent with multiple binding modes and conformations shown by NMR and gel electrophoresis. CD melting confirmed that ZnPc 2 and ZnPc 4, both containing eight positive charges, are able to stabilize the AT11 G4 structure (ΔTm > 30 °C and 18.5 °C, respectively). Molecular docking studies of ZnPc 3 and ZnPc 4 suggested a preferential binding to the 3'- and 5'-end, respectively, of the AT11 G4. ZnPc 3 and its AT11 and AT11-L0 complexes revealed pronounced cytotoxic effect against cervical cancer cells and no cytotoxicity to normal human cells. Zn(II) phthalocyanines provide the basis for the development of effective therapeutic agents as G4 ligands.
- MeSH
- antitumorózní látky chemie farmakologie MeSH
- aptamery nukleotidové chemie farmakologie MeSH
- buněčné linie MeSH
- G-kvadruplexy MeSH
- HeLa buňky MeSH
- indoly chemie farmakologie MeSH
- lidé MeSH
- nádory farmakoterapie MeSH
- oligodeoxyribonukleotidy chemie farmakologie MeSH
- organokovové sloučeniny chemie farmakologie MeSH
- simulace molekulového dockingu MeSH
- viabilita buněk účinky léků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Nucleic acid aptamers can specifically bind to target molecules on the cell membrane that mediate their entrance into the cells. Their small size, high binding affinity, specificity, good biocompatibility, stability and low immunogenicity make them ideal drug delivery systems for cancer therapy. These biopharmaceuticals have potential for the delivery of anticancer compounds to diseased tissues, increasing their effectiveness while mitigating the off-target toxicity towards healthy cells. Herein, we have studied two quadruplex-forming DNA sequences derived from the nucleolin-targeted aptamer AS1411 as supramolecular carriers for the cancer-selective delivery of acridine orange derivatives (C3, C5 and C8) in cervical cancer cells. The devised delivery strategy relied on the non-covalent association of the acridine derivatives and the G-quadruplex (G4) structures. This association is done with a high binding strength, as suggested by the obtained KD values in the 10-6-10-7 M range, leading to the thermal stabilization of the G4 structures, particularly for C8. The stability of the resulting supramolecular conjugates was evaluated in fetal bovine serum, which proved their resistance against serum nucleases up to 48 h. Previous studies showed that the tested acridine orange derivatives were cytotoxic towards cervical cancer cells (HeLa) and non-malignant cells. However, when conjugated to AS1411 derivatives, the cytotoxicity of the free ligands towards non-malignant cells was restrained. Furthermore, conjugated C3 showed an enhanced cytotoxicity against HeLa cancer cells. Confocal microscopy indicated that both G4 sequences appear to colocalize with nucleolin, suggesting their ability to recognize and bind nucleolin on the cell surface. Additionally, the results confirmed the internalization of these delivery systems into HeLa cancer cells and their sustained cell trafficking, although being able to dissociate intracellularly to deliver C8 to the nucleoli. Overall, we showed that AS1411-derived G4s can be used as a potential cancer drug delivery system for cervical cancer.
- MeSH
- akridinová oranž aplikace a dávkování analogy a deriváty chemie MeSH
- aptamery nukleotidové aplikace a dávkování chemie MeSH
- buněčné linie MeSH
- G-kvadruplexy * MeSH
- lidé MeSH
- ligandy MeSH
- nádory děložního čípku metabolismus MeSH
- oligodeoxyribonukleotidy aplikace a dávkování chemie MeSH
- systémy cílené aplikace léků * MeSH
- viabilita buněk účinky léků MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
