Naphthalene diimide‐derivatives G‐quadruplex ligands induce cell proliferation inhibition, mild telomeric dysfunction and cell cycle perturbation in U251MG glioma cells

Abstract

In the present paper, the biological effects of three different naphthalene diimides (NDIs) G-quadruplex (G4) ligands (H-NDI-Tyr, H-NDI-NMe2, and tetra-NDI-NMe2) were comparatively evaluated to those exerted by RHPS4, a well-characterized telomeric G4-ligand, in an in vitro model of glioblastoma. Data indicated that NDIs were very effective in blocking cell proliferation at nanomolar concentrations, although displaying a lower specificity for telomere targeting compared to RHPS4. In addition, differently from RHPS4, NDIs failed to enhance the effect of ionizing radiation, thus suggesting that additional targets other than telomeres could be involved in the strong NDI-mediated anti-proliferative effects. In order to test telomeric off-target action of NDIs, a panel of genes involved in tumor progression, DNA repair, telomere maintenance, and cell-cycle regulation were evaluated at transcriptional and translational level. Specifically, the compounds were able to cause a marked reduction of TERT and BCL2 amounts as well as to favor the accumulation of proteins involved in cell cycle control. A detailed cytofluorimetric analysis of cell cycle progression by means of bromodeoxyuridine (BrdU) incorporation and staining of phospho-histone H3 indicated that NDIs greatly reduce the progression through S-phase and lead to G1 accumulation of BrdU-positive cells. Taken together, these data indicated that, besides effects on telomeres and oncogenes such as Tert and Bcl2, nanomolar concentrations of NDIs determined a sustained block of cell proliferation by slowing down cell cycle progression during S-phase. In conclusion, our data indicate that NDIs G4-ligands are powerful antiproliferative agents, which act through mechanisms that ultimately lead to altered cell-cycle control.

G-Quadruplexes at Telomeres: Friend or Foe?

“…It should be borne in mind, however, that some of these effects may be indirect, caused by binding of the ligands elsewhere in the genome. For example, the promoter of the gene encoding the catalytic subunit of telomerase, hTERT, harbors G-quadruplexes [ 52 ], and G4-stabilizing ligands have been shown to decrease levels of hTERT expression [ 53 , 54 , 55 ], which may in turn lead to telomere deprotection [ 56 , 57 ]. G4-stabilizing ligands have also been shown to have widespread effects on gene expression, including genes involved in DNA damage pathways [ 58 , 59 ], likely due either to the enrichment of G-quadruplexes in gene regulatory regions [ 60 , 61 ], in response to the genome-wide DNA damage response triggered by G4 ligands [ 62 , 63 ], or as a result of epigenetic changes affecting gene expression [ 64 , 65 ].…”

Recent Progress of Targeted G-Quadruplex-Preferred Ligands Toward Cancer Therapy

“…One conceivable obstacle impeding the clinical application of G4-interacting molecules seems to rest with selectivity, although the global or multiple G4 targeting approaches may be effective [57,58,59,60,61], and in fact, CX-5461, a DNA G4 stabilizer, is currently at advanced phase I clinical trials for patients with BRCA1/2 deficient tumors [57,58]. Bioinformatics and next-generation sequencing (NGS) analysis estimated that 376,000 or more putative G4-forming sequences exist in the human genome [18,62].…”

A Family of Heterocyclic Naphthalene Diimide (NDI) Analogues: Comparing Parent Isoquinoline Diimides and Phthalazine Diimides with NDI

“…Naphthalene diimides (NDIs) as a member of rylene diimides, have shown potential for applications in a broad range of disciplines such as supramolecular chemistry, catalysis, molecular switching, sensors, optoelectronics and biomedicine . NDIs are robust and planar molecules with tunable electronic properties behaving as an electron‐deficient polycyclic arene with high electron affinity and capability of self‐assembly to form higher architectures that promote high charge mobilities .…”

“…Naphthalene diimides (NDIs) as a member of rylene diimides, have shown potential for applications in a broad range of disciplines such as supramolecular chemistry, catalysis, molecular switching, sensors, optoelectronics and biomedicine. [1][2][3][4][5][6][7][8] NDIs are robust and planar molecules with tunable electronic properties behaving as an electron-deficient polycyclic arene with high electron affinity and capability of self-assembly to form higher architectures that promote high charge mobilities. [5] The chemical versatility, synthetically speaking, of NDIs rely on their functionalisation through the imide nitrogens (N-imide, affecting their solubility and supramolecular packing) or on the naphthalene core (core-substitution, affecting their electronic and chemical properties).…”