Inhibitor of the human telomerase reverse trancriptase (hTERT) gene promoter induces cell apoptosis via a mitochondrial-dependent pathway

Development of 3D Cell-Based Fluorescent Reporter Assay for Screening of Drugs Downregulating Telomerase Reverse Transcriptase

A fluorescent cell-based assay was developed for the screening of chemicals repressing the expression of human telomerase reverse transcriptase (hTERT). hTERT is reactivated during carcinogenesis and is overexpressed in more than 90% of cancers but is almost silent in normal tissue cells. Because of its critical role in cancer, hTERT is a target in various therapeutic strategies for cancer treatment. In this study, the hTERT promoter was cloned in MCF7 breast cancer cells and used to control the expression of enhanced green fluorescent protein (EGFP). The fluorescence of EGFP indicated the activity of the hTERT promoter, and, in the presence of an hTERT repressor, the EGFP fluorescence signal was reduced as compared to the EGFP fluorescence controlled by the human cytomegalovirus (CMV) promoter, which was not affected by changes in culture conditions and worked as a control. The EGFP reporter cells were cultivated in three-dimensional (3D) microbioreactors to resemble the in vivo tumor physiology and provide in vivo-like responses. The assay's predictability was demonstrated with three known hTERT inhibitors, pristimerin, epigallocatechin gallate, and n-butylidenephthalide, and further evaluated with five widely used anticancer compounds, doxorubicin, cisplatin, paclitaxel, blasticidin, and tamoxifen. The results showed overall accuracy of over 83.3%, demonstrating the feasibility of using the hTERT promoter with EGFP as a reporter for the screening of potential cancer drugs targeting hTERT.

Fabricating niosomal-PEG nanoparticles co-loaded with metformin and silibinin for effective treatment of human lung cancer cells

Background

Despite current therapies, lung cancer remains a global issue and requires the creation of novel treatment methods. Recent research has shown that biguanides such as metformin (MET) and silibinin (SIL) have a potential anticancer effect. As a consequence, the effectiveness of MET and SIL in combination against lung cancer cells was investigated in this study to develop an effective and novel treatment method.

Methods

Niosomal nanoparticles were synthesized via the thin-film hydration method, and field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR), atomic force microscopy (AFM), and dynamic light scattering (DLS) techniques were used to evaluate their physico-chemical characteristics. The cytotoxic effects of free and drug-loaded nanoparticles (NPs), as well as their combination, on A549 cells were assessed using the MTT assay. An apoptosis test was used while under the influence of medication to identify the molecular mechanisms behind programmed cell death. With the use of a cell cycle test, it was determined whether pharmaceutical effects caused the cell cycle to stop progressing. Additionally, the qRT-PCR technique was used to evaluate the levels of hTERT, BAX, and BCL-2 gene expression after 48-h medication treatment.

Results

In the cytotoxicity assay, the growth of A549 lung cancer cells was inhibited by both MET and SIL. Compared to the individual therapies, the combination of MET and SIL dramatically and synergistically decreased the IC50 values of MET and SIL in lung cancer cells. Furthermore, the combination of MET and SIL produced lower IC50 values and a better anti-proliferative effect on A549 lung cancer cells. Real-time PCR results showed that the expression levels of hTERT and BCL-2 were significantly reduced in lung cancer cell lines treated with MET and SIL compared to single treatments (p< 0.001).

Conclusion

It is anticipated that the use of nano-niosomal-formed MET and SIL would improve lung cancer treatment outcomes and improve the therapeutic efficiency of lung cancer cells.

Telomere Length as a marker of biological aging: A critical review of recent literature

INTRODUCTION

Aging is characterized as a syndrome of deleterious, progressive, universal, and irreversible function changes affecting every structural and functional aspect of the organism and accompanied by a generalized increase in mortality. Although a substantial number of candidates for biomarkers of aging have been proposed, none has been validated or universally accepted. Human telomeres constitute hexameric repetitive DNA sequence nucleoprotein complexes that cap chromosome ends, regulating gene expression and modulating stress-related pathways. Telomere length (TL) shortening is observed both in cellular senescence and advanced age, leading to the investigation of TL as a biomarker for aging and a risk factor indicator for the development and progression of the most common age-related diseases.

OBJECTIVE

The present review underlines the connection between TL and the pathophysiology of the diseases associated with telomere attrition.

METHODS

We performed a structured search of the PubMed database for peer-reviewed research of the literature regarding leukocyte TL and cardiovascular diseases (CVD), more specifically stroke and heart disease, and focused on the relevant articles published during the last 5 years. We also applied Hill's criteria of causation to strengthen this association.

RESULTS

We analyzed the recent literature regarding TL length, stroke, and CVD. Although approximately one-third of the available studies support the connection, the results of different studies seem to be rather conflicting as a result of different study designs, divergent methods of TL determination, small study samples, and patient population heterogeneity. After applying Hill's criteria, we can observe that the literature conforms to them weakly, with chronology being the only Hill criterion of causality that probably cannot be contested.

CONCLUSION

The present review attempted to examine the purported relation between leukocyte TL and age-related diseases such as CVD and more specific stroke and heart disease in view of the best established, comprehensive, medical and epidemiological criteria that have characterized the focused recent relevant research. Although several recommendations have been made that may contribute significantly to the field, a call for novel technical approaches and studies is mandatory to further elucidate the possible association.

Caffeine promotes the expression of telomerase reverse transcriptase to regulate cellular senescence and aging

Telomere shortening is one of the main causes of cellular senescence. Caffeine is a natural stimulant most commonly found in coffee and tea. In this study, caffeine was found to promote the expression of telomerase reverse transcriptase (TERT) at both mRNA and protein levels, and consequently extended the telomere length and prevented cellular senescence. Knockdown of TERT eliminated the effect of caffeine on telomere elongation. Moreover, animal studies indicated that caffeine promoted the expression of TERT and extended the telomere length in the thymus and spleen of mice treated with caffeine for a long period of eight months. In addition, caffeine restored the decline of organ index and improved the histological structural change of the thymus, spleen and liver of mice due to aging. These results suggest that caffeine promotes the expression of TERT to delay cellular senescence and aging, which help to understand the mechanism for the beneficial effects of caffeine containing foods on health.

Recent trends in cancer therapy: A review on the current state of gene delivery

Cancer treatment has been always considered one of the most critical and vital themes of clinical issues. Many approaches have been developed, depending on the type and the stage of tumor. Gene therapy has the potential to revolutionize different cancer therapy. With the advent of recent bioinformatics technologies and genetic science, it become possible to identify, diagnose and determine the potential treatment using the technology of gene delivery. Several approaches have been developed and experimented in vitro and vivo for cancer therapy including: naked nucleic acids based therapy, targeting micro RNAs, oncolytic virotherapy, suicide gene based therapy, targeting telomerase, cell mediated gene therapy, and CRISPR/Cas9 based therapy. In this review, we present a straightforward introduction to cancer biology and occurrence, highlighting different viral and non-viral gene delivery systems for gene therapy and critically discussed the current and various strategies for cancer gene therapy.

Silencing hTERT attenuates cancer stem cell-like characteristics and radioresistance in the radioresistant nasopharyngeal carcinoma cell line CNE-2R

Objective: This study aimed to explore the effect of silencing hTERT on the CSC-like characteristics and radioresistance of CNE-2R cells.

Results: Silencing hTERT suppressed CNE-2R cell proliferation and increased the cell apoptosis rate and radiosensitivity in vitro. Moreover, it could also inhibit the growth of xenografts and increase the apoptosis index and radiosensitivity in vivo. Further study discovered that after silencing hTERT, telomerase activity in CNE-2R cells was markedly suppressed, along with remarkably down-regulated stem cell-related protein levels both in vitro and in vivo.

Conclusion: Silencing hTERT can suppress the CSC-like characteristics of CNE-2R cells to enhance their radiosensitivity, revealing that hTERT may become a potential target for treating radioresistant NPC.

Methods: An RNAi lentiviral vector specific to the hTERT gene was constructed to infect CNE-2R cells, the hTERT silencing effect was verified through qPCR and Western blot assays, and telomerase activity was detected by PCR-ELISA. Moreover, radiosensitivity in vitro was detected through colony formation assays, CCK-8 assays and flow cytometry. Tumor growth and radioresistance were also evaluated using xenograft models, while the apoptosis index in xenografts was measured through TUNEL assay. Levels of stem cell-related proteins were determined in vitro and in vivo.

Targeting telomerase for its advent in cancer therapeutics

Telomerase has emerged as an important primary target in anticancer therapy. It is a distinctive reverse transcriptase enzyme, which extends the length of telomere at the 3' chromosomal end, and uses telomerase reverse transcriptase (TERT) and telomerase RNA template-containing domains. Telomerase has a vital role and is a contributing factor in human health, mainly affecting cell aging and cell proliferation. Due to its unique feature, it ensures unrestricted cell proliferation in malignancy and plays a major role in cancer disease. The development of telomerase inhibitors with increased specificity and better pharmacokinetics is being considered to design and develop newer potent anticancer agents. Use of natural and synthetic compounds for the inhibition of telomerase activity can lead to an opening of new vistas in cancer treatment. This review details about the telomerase biochemistry, use of natural and synthetic compounds; vaccines and oncolytic virus in therapy that suppress the telomerase activity. We have discussed structure-activity relationships of various natural and synthetic telomerase inhibitors to help medicinal chemists and chemical biology researchers with a ready reference and updated status of their clinical trials. Suppression of human TERT (hTERT) activity through inhibition of hTERT promoter is an important approach for telomerase inhibition.

Combination of Curcumin and Metformin Inhibits Cell Growth and Induces Apoptosis without Affecting the Cell Cycle in LNCaP Prostate Cancer Cell Line

Side effects and chemotherapy resistance, demand new therapeutics with minimal side effects. Here, we investigated the combined effect of curcumin and metformin on the LNCaP prostate cancer cell line. LNCaP cells were treated with curcumin, metformin, and their combination at different concentrations. Cell viability was assessed by MTT assay and expression of Bax, Bcl-2, mTOR, hTERT, PUMA, p53 and p21 genes was analyzed by real-time PCR. Apoptosis and cell cycle were assessed by flow cytometry. Our results revealed that the viability of cells treated with curcumin, metformin, and their combination was significantly (P < 0.05) reduced with increasing the concentration and prolonging the treatment time. Meanwhile, the combination showed a synergistic effect within 48 h. In the curcumin treated group, the expression of Bcl-2 and hTERT genes diminished. In the metformin treated group, the expression of Bax and PUMA genes was enhanced while the expression of Bcl-2, hTERT, mTOR, and p53 genes declined. Although all treatments induced apoptosis, the combination of curcumin and metformin showed the maximum level of apoptosis, cytotoxicity, and expression of Bax gene. The combination of curcumin and metformin showed synergistic effects within 48 h. This combination could be a potential therapeutic candidate for prostate cancer to be further investigated.

Ligustilide alleviates the insulin resistance, lipid accumulation, and pathological injury with elevated phosphorylated AMPK level in rats with diabetes mellitus

BACKGROUND

Diabetes mellitus (DM) is one of the major risk factors of disability and death worldwide. Despite of the protective role of ligustilide (LIG) in many cell types, we aimed to investigate whether LIG could be a potential to treat DM.

METHODS

Sprague Dawley rats were randomly assigned to five groups. Rats except control were raised on a high-fat diet (HFD). Streptozotocin was intraperitoneally injected into HFD-fed rats to construct DM model. Rats in the LIG intervention groups received intraperitoneal injection of LIG (10, 20, and 40 mg/kg) post-induction of DM. Blood glucose, plasma insulin (p-insulin), adiponectin, HbA1C%, obesity index, HOMA-IR, and biochemical parameters were estimated. Histopathological analysis and apoptosis in liver and kidney, along with proliferation and apoptosis of islet β-cells, were analyzed. Expression of CPT-1 and ACC, and phosphorylation of Nrf2 and AMPKα1, were finally assessed.

RESULTS

DM-induced alterations were all relived by LIG intervention. In brief, obesity index, glucose level, P-insulin content, HbA1C, and HOMA-IR were lowered while adiponectin level was elevated. Meanwhile, levels of TC, TG, ALT, and AST were decreased in the LIG intervention groups, along with up-regulated CPT-1 level and down-regulated ACC level. Pathological changes in liver and kidney tissues were alleviated, and apoptotic cells were reduced by LIG treatment. For islet β-cells, LIG up-regulated Ki67 and c-Myc expression, and mitigated ratios of Bax/Bcl-2 and cleaved cas3(9)/cas3(9). Finally, LIG could promote phosphorylation of Nrf2 and AMPKα1.

CONCLUSIONS

LIG alleviated the insulin resistance, lipid accumulation, and pathological injury with the activation of AMPK pathway in DM rats.

Insights into the New Cancer Therapy through Redox Homeostasis and Metabolic Shifts

Modest levels of reactive oxygen species (ROS) are necessary for intracellular signaling, cell division, and enzyme activation. These ROS are later eliminated by the body’s antioxidant defense system. High amounts of ROS cause carcinogenesis by altering the signaling pathways associated with metabolism, proliferation, metastasis, and cell survival. Cancer cells exhibit enhanced ATP production and high ROS levels, which allow them to maintain elevated proliferation through metabolic reprograming. In order to prevent further ROS generation, cancer cells rely on more glycolysis to produce ATP and on the pentose phosphate pathway to provide NADPH. Pro-oxidant therapy can induce more ROS generation beyond the physiologic thresholds in cancer cells. Alternatively, antioxidant therapy can protect normal cells by activating cell survival signaling cascades, such as the nuclear factor erythroid 2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) pathway, in response to radio- and chemotherapeutic drugs. Nrf2 is a key regulator that protects cells from oxidative stress. Under normal conditions, Nrf2 is tightly bound to Keap1 and is ubiquitinated and degraded by the proteasome. However, under oxidative stress, or when treated with Nrf2 activators, Nrf2 is liberated from the Nrf2-Keap1 complex, translocated into the nucleus, and bound to the antioxidant response element in association with other factors. This cascade results in the expression of detoxifying enzymes, including NADH-quinone oxidoreductase 1 (NQO1) and heme oxygenase 1. NQO1 and cytochrome b5 reductase can neutralize ROS in the plasma membrane and induce a high NAD⁺/NADH ratio, which then activates SIRT1 and mitochondrial bioenergetics. NQO1 can also stabilize the tumor suppressor p53. Given their roles in cancer pathogenesis, redox homeostasis and the metabolic shift from glycolysis to oxidative phosphorylation (through activation of Nrf2 and NQO1) seem to be good targets for cancer therapy. Therefore, Nrf2 modulation and NQO1 stimulation could be important therapeutic targets for cancer prevention and treatment.

Human telomerase reverse transcriptase positively regulates mitophagy by inhibiting the processing and cytoplasmic release of mitochondrial PINK1

Mutations in the phosphatase and tensin homologue-induced putative kinase 1 (PINK1) gene have been linked to an early-onset autosomal recessive form of familial Parkinson′s disease (PD). PINK1, a mitochondrial serine/threonine-protein kinase, plays an important role in clearing defective mitochondria by mitophagy – the selective removal of mitochondria through autophagy. Evidence suggests that alteration of the PINK1 pathway contributes to the pathogenesis of PD, but the mechanisms by which the PINK1 pathway regulates mitochondrial quality control through mitophagy remain unclear. Human telomerase reverse transcriptase (hTERT) is a catalytic subunit of telomerase that functions in telomere maintenance as well as several non-telomeric activities. For example, hTERT has been associated with cellular immortalization, cell growth control, and mitochondrial regulation. We determined that hTERT negatively regulates the cleavage and cytosolic processing of PINK1 and enhances its mitochondrial localization by inhibiting mitochondrial processing peptidase β (MPPβ). Consequently, hTERT promotes mitophagy following carbonyl cyanide m-chlorophenylhydrazone (CCCP)-induced mitochondrial dysfunction and improves the function of damaged mitochondria by modulating PINK1. These findings suggest that hTERT positively regulates PINK1 function, leading to increased mitophagy following mitochondrial damage.

Therapeutic strategies for targeting telomerase in cancer

Telomere and telomerase play important roles in abnormal cell proliferation, metastasis, stem cell maintenance, and immortalization in various cancers. Therefore, designing of drugs targeting telomerase and telomere is of great significance. Over the past two decades, considerable knowledge regarding telomere and telomerase has been accumulated, which provides theoretical support for the design of therapeutic strategies such as telomere elongation. Therefore, the development of telomere-based therapies such as nucleoside analogs, non-nucleoside small molecules, antisense technology, ribozymes, and dominant negative human telomerase reverse transcriptase are being prioritized for eradicating a majority of tumors. While the benefits of telomere-based therapies are obvious, there is a need to address the limitations of various therapeutic strategies to improve the possibility of clinical applications. In this study, current knowledge of telomere and telomerase is discussed, and therapeutic strategies based on recent research are reviewed.

Overexpression of Tumor Protein p53-regulated Apoptosis-inducing Protein 1 Regulates Proliferation and Apoptosis of Breast Cancer Cells through the PI3K/Akt Pathway

Purpose

Tumor protein p53-regulated apoptosis-inducing protein 1 (TP53AIP1) functions in various cancers. We studied the effect and molecular mechanism of TP53AIP1 in breast cancer.

Methods

The degree of correlation between TP53AIP1 expression and overall survival in patients with breast cancer was obtained from the online The Cancer Genome Atlas database. Six of the TP53AIP1 levels in the tumor and adjacent non-tumor tissues randomly selected from 38 breast cancer patients were determined. Transgenic technology was used to enhance the expression of TP53AIP1 in breast cancer cell lines, MDA-MB-415 and MDA-MB-468, and to observe the effects of gene overexpression on the proliferation, cell cycle, and apoptosis of breast cancer cells. The molecular mechanism of association between cell cycle- and apoptosis-related factors and the phosphoinositide 3-kinases/protein kinase B (PI3K/Akt) pathway was also studied.

Results

The messenger RNA and protein expression levels of TP53AIP1 in cancer tissues were significantly lower than those in the control group. TP53AIP1 overexpression inhibits cell viability. The mechanism of TP53AIP1 inhibition of proliferation and growth of breast cancer cells includes cell cycle arrest, apoptosis promotion (p < 0.01), promotion of the expression of cleaved-caspase-3 (p < 0.01), cleaved-caspase-9 (p < 0.01), B cell lymphoma/leukemia-2 (Bcl-2)-associated X protein, and p53 (p < 0.01), and the inhibition of Bcl-2, Ki67, and PI3K/Akt pathways (p < 0.01).

Conclusion

TP53AIP1 may be a novel tumor suppressor gene in breast cancer and can potentially be used as an effective target gene for the treatment of breast cancer.

Advantages and disadvantages of apoptosis in the aging process

Researchers cannot predict as yet how long a human being can live. Life expectancy has been steadily increasing in the last century, but perhaps not always the quality of life in parallel with it. Future generations will be faced with the problems of an increased life expectancy along with the emergence of new age-related diseases. A deeper understanding of the aging process is crucial to ameliorate, if not to prevent, these projected new old-age diseases. One of the mechanisms responsible for healthy aging is through the effective maintenance of physiological, biochemical, and immunological functions. To carry this out, the organism needs to create new cells to replace old ones and to induce the disappearance of old and damaged cells. Apoptosis is involved in all these processes. However, if apoptosis is dysregulated, premature senescence-associated diseases are likely to appear. In our review, the focus will be on a better understanding of the role of apoptosis in the aging process. These signaling pathways will most assuredly be pharmacologically targeted in antiaging medicine therapies.

The telomere world and aging: Analytical challenges and future perspectives

Telomeres, the terminal nucleoprotein structures of eukaryotic chromosomes, play pleiotropic functions in cellular and organismal aging. Telomere length (TL) varies throughout life due to the influence of genetic factors and to a complex balancing between "shortening" and "elongation" signals. Telomerase, the only enzyme that can elongate a telomeric DNA chain, and telomeric repeat-containing RNA (TERRA), a long non-coding RNA involved in looping maintenance, play key roles in TL during life. Despite recent advances in the knowledge of TL, TERRA and telomerase activity (TA) biology and their measurement techniques, the experimental and theoretical issues involved raise a number of problems that should carefully be considered by researchers approaching the "telomere world". The increasing use of such parameters - hailed as promising clinically relevant biomarkers - has failed to be paralleled by the development of automated and standardized measurement technology. Consequently, associating given TL values to specific pathological conditions involves on the one hand technological issues and on the other clinical-biological issues related to the planning of clinically relevant association studies. Addressing these issues would help avoid major biases in association studies involving TL and a number of outcomes, especially those focusing on psychological and bio-behavioral variables. The main challenge in telomere research is the development of accurate and reliable measurement methods to achieve simple and sensitive TL, TERRA, and TA detection. The discovery of the localization of telomeres and TERRA in cellular and extracellular compartments had added an additional layer of complexity to the measurement of these age-related biomarkers. Since combined analysis of TL, TERRA and TA may well provide more exhaustive clinical information than a single parameter, we feel it is important for researchers in the various fields to become familiar with their most common measurement techniques and to be aware of the respective merits and drawbacks of these approaches.

Complexes of lanthanides(iii) with mixed 2,2′-bipyridyl and 5,7-dibromo-8-quinolinoline chelating ligands as a new class of promising anti-cancer agents

MeOMBrQ-Ho induced HeLa cell apoptosis was mediated by inhibition of telomerase activity and dysfunction of mitochondria. Remarkably, MeOMBrQ-Ho obviously inhibited HeLa xenograft tumor growth in vivo.

The prognostic significance of TERT promoter mutations in meningioma: a systematic review and meta-analysis

BACKGROUND

Mutations in the telomerase reverse transcriptase promoter (TERTp) region have been associated with worse prognosis in some cancers. Meningiomas are the most common type of primary central nervous tumors, and evaluation of the prognostic significance of TERTp mutations across the literature is lacking. The aim of this study was to pool all current evidence to assess for clinical relevance of TERTp mutations in meningioma and survival effect.

METHODS

Searches of seven electronic databases from inception to September 2018 were conducted following the appropriate guidelines. Two hundred and twenty seven articles were identified for screening. Hazard ratio (HR) and mean difference (MD) statistics were obtained and pooled utilizing both fixed- and random-effect (RE) models. Meta-regression was utilized to determine potential sources of heterogeneity and statistical influence.

RESULTS

A total of five retrospective observational cohort studies describing 532 meningioma patients satisfied selection criteria. The incidence of TERTp mutations was 8%, and was associated with significantly worse prognosis (HR 3.79; P = 0.005) and significantly shorter overall survival (MD 59.8 months; P = 0.037) by RE modelling. Meningioma grade was not significantly associated with a TERTp mutation effect, however, preliminary meta-regression trends indicated this may be significant once greater statistical power is achieved.

CONCLUSION

The current evidence indicates the presence of a TERTp mutation in meningioma can be associated with worse prognosis, and shorter overall survival. Routine detection in greater numbers will allow for further validation, as well as delineate the effect across histological grades. By identifying this subgroup of meningioma patients early in management, it may support more frequent follow-up and aggressive management to optimize survival outcomes.

Ethenesulfonyl fluoride derivatives as telomerase inhibitors: structure-based design, SAR, and anticancer evaluation in vitro

Based on our previous docking model, in order to carry out more rational drug design, totally 82 vinyl sulfonyl fluorides, including some 2-(hetero)arylethenesulfonyl fluorides and 1,3-dienylsulfonyl fluorides derivatives as potential human telomerase inhibitors were designed and synthesised. The in vitro anticancer activity assay showed that compound 57 (1E,3E)-4-(4-((E)-2-(fluorosulfonyl)vinyl)phenyl)buta-1,3-diene-1-sulfonyl fluoride exhibited high activity against A375 and MDA-MB-231 cell lines with IC₅₀ 1.58 and 3.22 µM, but it manifested obvious un-toxic effect against GES-1 and L-02 with IC₅₀ with IC₅₀ values less than 2.00 mM. By the modified TRAP assay, some compounds including 57 exhibited potent inhibitory activities against telomerase with IC₅₀ values of 0.71–0.97 µM.