Primer-Modified G-Quadruplex-Au Nanoparticles for Colorimetric Assay of Human Telomerase Activity and Initial Screening of Telomerase Inhibitors

AbstractTight regulatory mechanisms to maintain repression of human Telomerase (hTERT), the sole protein that synthesizes telomeres, is crucial for normal adult somatic cells. In contrast, enhanced telomerase activity and resulting pathological maintenance of telomeres, is widely understood as causal in >90% of human cancers. These implicate underlying mechanisms connecting hTERT regulation and telomeres, possibly through telomeric proteins, that remain unclear. In light of of recent work by us and others showing non-telomeric function of the telomere-binding protein TRF2, here we examined whether and how TRF2 affected hTERT regulation. Direct binding of TRF2 – spanning ∼450 bp of the hTERT promoter from the Transcriptional Start Site (TSS) – led to TRF2-dependent recruitment of the polycomb repressor complex PRC2 in both normal and cancer cells. This induced repressor histone modifications resulting in TRF2-dependent hTERT repression. Mutations in the hTERT promoter, found frequently in aggressive glioblastoma and reported to destabilize the G-quadruplex structure, resulted in loss of TRF2 binding and consequent hTERT over-expression. Conversely, using G-quadruplex-stabilizing ligands we regained TRF2 binding, hTERT re-suppression, in highly proliferating glioblastoma cells with telomerase hyperactivation due to hTERT promoter mutations. Together, results herein demonstrate direct control of hTERT through TRF2 in a G-quadruplex-dependent manner – implicating mechanisms of how telomerase regulation might be linked to telomeres in normal and cancer cells.

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Water-soluble porphyrinoids as G-quadruplex binders and telomerase inhibitors

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s108842461650053x ◽

2016 ◽

Vol 20 (08n11) ◽

pp. 1041-1048 ◽

Cited By ~ 2

Author(s):

Yoshiya Ikawa ◽

Sho Katsumata ◽

Ryuichi Sakashita ◽

Shinobu Sato ◽

Shigeori Takenaka ◽

...

Keyword(s):

Telomerase Activity ◽

Inhibitory Effect ◽

Water Soluble ◽

Inhibitory Effects ◽

Binding Ability ◽

Telomerase Inhibitors ◽

Expanded Porphyrins ◽

G4 Dna ◽

G Quadruplex ◽

Derivatives Of

Water-soluble derivatives of three kinds of expanded porphyrins (N-fused pentaphyrin, hexaphyrin, and heptaphyrin) were synthesized and their binding ability to G-quadruplex (G4-) DNA was evaluated. The inhibitory effects on enzymatic telomere extension were also investigated together with other tetrapyrrolic porphyrinoids. While expanded porphyrins increased the melting temperature of G4-DNA more effectively than the regular porphyrins, a porphyrin isomer (N-confused porphyrin) showed the highest inhibitory effect on telomerase activity.

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Oligonucleotides and microRNAs Targeting Telomerase Subunits in Cancer Therapy

Cancers ◽

10.3390/cancers12092337 ◽

2020 ◽

Vol 12 (9) ◽

pp. 2337

Author(s):

Adam Eckburg ◽

Joshua Dein ◽

Joseph Berei ◽

Zachary Schrank ◽

Neelu Puri

Keyword(s):

Cancer Therapeutics ◽

Telomerase Activity ◽

Cancer Therapies ◽

Human Telomerase Reverse Transcriptase ◽

Conceptual Foundation ◽

Telomerase Inhibitors ◽

Current State ◽

Anti Cancer ◽

Cancer Types ◽

Human Telomerase

Telomerase provides cancer cells with replicative immortality, and its overexpression serves as a near-universal marker of cancer. Anti-cancer therapeutics targeting telomerase have garnered interest as possible alternatives to chemotherapy and radiotherapy. Oligonucleotide-based therapies that inhibit telomerase through direct or indirect modulation of its subunits, human telomerase reverse transcriptase (hTERT) and human telomerase RNA gene (hTERC), are a unique and diverse subclass of telomerase inhibitors which hold clinical promise. MicroRNAs that play a role in the upregulation or downregulation of hTERT and respective progression or attenuation of cancer development have been effectively targeted to reduce telomerase activity in various cancer types. Tumor suppressor miRNAs, such as miRNA-512-5p, miRNA-138, and miRNA-128, and oncogenic miRNAs, such as miRNA-19b, miRNA-346, and miRNA-21, have displayed preclinical promise as potential hTERT-based therapeutic targets. Antisense oligonucleotides like GRN163L and T-oligos have also been shown to uniquely target the telomerase subunits and have become popular in the design of novel cancer therapies. Finally, studies suggest that G-quadruplex stabilizers, such as Telomestatin, preserve telomeric oligonucleotide architecture, thus inhibiting hTERC binding to the telomere. This review aims to provide an adept understanding of the conceptual foundation and current state of therapeutics utilizing oligonucleotides to target the telomerase subunits, including the advantages and drawbacks of each of these approaches.

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Oligonucleotides Targeting Telomeres and Telomerase in Cancer

Molecules ◽

10.3390/molecules23092267 ◽

2018 ◽

Vol 23 (9) ◽

pp. 2267 ◽

Cited By ~ 20

Author(s):

Zachary Schrank ◽

Nabiha Khan ◽

Chike Osude ◽

Sanjana Singh ◽

Rachel Miller ◽

...

Keyword(s):

Telomerase Activity ◽

Therapeutic Approaches ◽

Comprehensive Understanding ◽

Telomerase Inhibitors ◽

G Quadruplex ◽

Dna Damage Responses ◽

Anticancer Therapeutics ◽

Stabilizing Ligands ◽

Cell Immortality ◽

Novel Therapeutic

Telomeres and telomerase have become attractive targets for the development of anticancer therapeutics due to their involvement in cancer cell immortality. Currently, several therapeutics have been developed that directly target telomerase and telomeres, such as telomerase inhibitors and G-quadruplex stabilizing ligands. Telomere-specific oligonucleotides that reduce telomerase activity and disrupt telomere architecture are also in development as novel anticancer therapeutics. Specifically, GRN163L and T-oligos have demonstrated promising anticancer activity in multiple cancers types via induction of potent DNA damage responses. Currently, several miRNAs have been implicated in the regulation of telomerase activity and may prove to be valuable targets in the development of novel therapies by reducing expression of telomerase subunits. Targeting miRNAs that are known to increase expression of telomerase subunits may be another strategy to reduce carcinogenesis. This review aims to provide a comprehensive understanding of current oligonucleotide-based anticancer therapies that target telomeres and telomerase. These studies may help design novel therapeutic approaches to overcome the challenges of oligonucleotide therapy in a clinical setting.

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Berberine Inhibits Telomerase Activity and Induces Cell Cycle Arrest and Telomere Erosion in Colorectal Cancer Cell Line, HCT 116

Molecules ◽

10.3390/molecules26020376 ◽

2021 ◽

Vol 26 (2) ◽

pp. 376

Author(s):

Muhammad Azizan Samad ◽

Mohd Zuwairi Saiman ◽

Nazia Abdul Majid ◽

Saiful Anuar Karsani ◽

Jamilah Syafawati Yaacob

Keyword(s):

Colorectal Cancer ◽

Cell Cycle ◽

Cell Line ◽

Cancer Cell ◽

Telomerase Activity ◽

Telomerase Inhibitor ◽

Telomerase Inhibitors ◽

Hct 116 ◽

Human Telomerase ◽

Telomere Erosion

Colorectal cancer (CRC) is the most common cancer among males and females, which is associated with the increment of telomerase level and activity. Some plant-derived compounds are telomerase inhibitors that have the potential to decrease telomerase activity and/or level in various cancer cell lines. Unfortunately, a deeper understanding of the effects of telomerase inhibitor compound(s) on CRC cells is still lacking. Therefore, in this study, the aspects of telomerase inhibitors on a CRC cell line (HCT 116) were investigated. Screening on HCT 116 at 48 h showed that berberine (10.30 ± 0.89 µg/mL) is the most effective (lowest IC50 value) telomerase inhibitor compared to boldine (37.87 ± 3.12 µg/mL) and silymarin (>200 µg/mL). Further analyses exhibited that berberine treatment caused G0/G1 phase arrest at 48 h due to high cyclin D1 (CCND1) and low cyclin-dependent kinase 4 (CDK4) protein and mRNA levels, simultaneous downregulation of human telomerase reverse transcriptase (TERT) mRNA and human telomerase RNA component (TERC) levels, as well as a decrease in the TERT protein level and telomerase activity. The effect of berberine treatment on the cell cycle was time dependent as it resulted in a delayed cell cycle and doubling time by 2.18-fold. Telomerase activity and level was significantly decreased, and telomere erosion followed suit. In summary, our findings suggested that berberine could decrease telomerase activity and level of HCT 116, which in turn inhibits the proliferative ability of the cells.

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A multicolor DNA tetrahedron nanoprobe for analyzing human telomerase in living cells

Chemical Communications ◽

10.1039/d0cc07893j ◽

2021 ◽

Author(s):

Ruiyuan Zhang ◽

Ruixue Zhang ◽

Wei Jiang ◽

Xiaowen Xu

Keyword(s):

Real Time ◽

Length Distribution ◽

Telomerase Activity ◽

Living Cells ◽

Real Time Monitoring ◽

Dna Tetrahedron ◽

Human Telomerase

A sequentially lighting-up multicolor DNA tetrahedron nanoprobe is constructed for imaging telomerase activity, real-time monitoring telomerase action and determining product length distribution in living cells.

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