Telomerase activation by hTRT in human normal fibroblasts and hepatocellular carcinomas

A CRISPR base editing approach for the functional assessment of telomere biology disorder-related genes in human health and aging

Telomere Biology Disorders (TBDs) are a group of rare diseases characterized by the presence of short and/or dysfunctional telomeres. They comprise a group of bone marrow failure syndromes, idiopathic pulmonary fibrosis, and liver disease, among other diseases. Genetic alterations (variants) in the genes responsible for telomere homeostasis have been linked to TBDs. Despite the number of variants already identified as pathogenic, an even more significant number must be better understood. The study of TBDs is challenging since identifying these variants is difficult due to their rareness, it is hard to predict their impact on the disease onset, and there are not enough samples to study. Most of our knowledge about pathogenic variants comes from assessing telomerase activity from patients and their relatives affected by a TBD. However, we still lack a cell-based model to identify new variants and to study the long-term impact of such variants on the genes involved in TBDs. Herein, we present a cell-based model using CRISPR base editing to mutagenize the endogenous alleles of 21 genes involved in telomere biology. We identified key residues in the genes encoding 17 different proteins impacting cell growth. We provide functional evidence for variants of uncertain significance in patients with TBDs. We also identified variants resistant to telomerase inhibition that, similar to cells expressing wild-type telomerase, exhibited increased tumorigenic potential using an in vitro tumour growth assay. We believe that such cell-based approaches will significantly advance our understanding of the biology of TBDs and may contribute to the development of new therapies for this group of diseases.

A pan-cancer analysis of Dyskeratosis congenita 1 (DKC1) as a prognostic biomarker

BACKGROUND

Dyskeratosis congenita 1 (DKC1), a critical component of telomerase complex, is highly expressed in a variety of human cancers. However, the association of DKC1 with cancer occurrence and development stages is not clear, making a pan-cancer analysis crucial.

METHODS

We conducted a study using various bioinformatic databases such as TIMER, GEPIA, UALCAN, and KM plotter Analysis to examine the different expressions of DKC1 in multiple tissues and its correlation with pathological stages. Through KEGG analysis, GO enrichment analysis and Venn analysis, we were able to reveal DKC1-associated genes and signaling pathways. In addition, we performed several tests including the CCK, wound healing assay, cell cycle arrest assay, transwell assay and Sa-β-gal staining on DKC1-deleted MDA-231 cells.

RESULTS

Our study demonstrates that DKC1 has relatively low expression specificity in different tissues. Furthermore, we found that in ACC, KICH, KIRP and LIHC, the expression level of DKC1 is positively correlated with pathological stages. Conversely, in NHSC, KIRP, LGG, LIHC, MESO and SARC, we observed a negative influence of DKC1 expression level on the overall survival rate. We also found a significant positive correlation between DKC1 expression and Tumor Mutational Burden in 14 tumors. Additionally, we observed a significantly negative impact of DKC1 DNA methylation on gene expression at the promoter region in BRCA. We also identified numerous phosphorylation sites concentrated at the C-terminus of the DKC1 protein. Our GO analysis revealed a correlation between DKC1 and ribosomal biosynthesis pathways, and the common element UTP14A was identified. We also observed decreased rates of cell proliferation, migration and invasion abilities in DKC1-knockout MDA-MB-231 cell lines. Furthermore, DKC1-knockout induced cell cycle arrest and caused cell senescence.

CONCLUSIONS

Our findings suggest that the precise expression of DKC1 is closely associated with the occurrence and developmental stages of cancer in multiple tissues. Depletion of DKC1 can inhibit the abilities of cancer cells to proliferate, migrate, and invade by arresting the cell cycle and inducing cell senescence. Therefore, DKC1 may be a valuable prognostic biomarker for the diagnosis and treatment of cancer in various tissues.

Integrated analysis of circulating cell free nucleic acids for cancer genotyping and immune phenotyping of tumor microenvironment

The circulating cell-free nucleic acids (ccfNAs) consist of a heterogenous cocktail of both single (ssNA) and double-stranded (dsNA) nucleic acids. These ccfNAs are secreted into the blood circulation by both healthy and malignant cells via various mechanisms including apoptosis, necrosis, and active secretion. The major source of ccfNAs are the cells of hematopoietic system under healthy conditions. These ccfNAs include fragmented circulating cell free DNA (ccfDNA), coding or messenger RNA (mRNA), long non-coding RNA (lncRNA), microRNA (miRNA), and mitochondrial DNA/RNA (mtDNA and mtRNA), that serve as prospective biomarkers in assessment of various clinical conditions. For, e.g., free fetal DNA and RNA migrate into the maternal plasma, whereas circulating tumor DNA (ctDNA) has clinical relevance in diagnostic, prognostic, therapeutic targeting, and disease progression monitoring to improve precision medicine in cancer. The epigenetic modifications of ccfDNA as well as circulating cell-free RNA (ccfRNA) such as miRNA and lncRNA show disease-related variations and hold potential as epigenetic biomarkers. The messenger RNA present in the circulation or the circulating cell free mRNA (ccf-mRNA) and long non-coding RNA (ccf-lncRNA) have gradually become substantial in liquid biopsy by acting as effective biomarkers to assess various aspects of disease diagnosis and prognosis. Conversely, the simultaneous characterization of coding and non-coding RNAs in human biofluids still poses a significant hurdle. Moreover, a comprehensive assessment of ccfRNA that may reflect the tumor microenvironment is being explored. In this review, we focus on the novel approaches for exploring ccfDNA and ccfRNAs, specifically ccf-mRNA as biomarkers in clinical diagnosis and prognosis of cancer. Integrating the detection of circulating tumor DNA (ctDNA) for cancer genotyping in conjunction with ccfRNA both quantitatively and qualitatively, may potentially hold immense promise towards precision medicine. The current challenges and future directions in deciphering the complexity of cancer networks based on the dynamic state of ccfNAs will be discussed.

Strategies for immortalisation of amnion-derived mesenchymal and epithelial cells

Mesenchymal (human amniotic mesenchymal stem cell [HAMSC]) and epithelial cells (human amnion epithelial cell [HAEC]) derived from human amniotic membranes possess characteristics of pluripotency. However, the pluripotency of HAMSC and HAEC are sustained only for a finite period. This in vitro cell growth can be extended by cell immortalisation. Many well-defined immortalisation systems have been used for artificially overexpressing genes such as human telomerase reverse transcriptase in HAMSC and HAEC leading to controlled and prolonged cell proliferation. In recent years, much progress has been made in our understanding of the cellular machinery that regulates the cell cycle when immortalised. This review summarises the current understanding of molecular mechanisms that contribute to cell immortalisation, the strategies that have been employed to immortalise amnion-derived cell types, and their likely applications in regenerative medicine.

An oncolytic virus as a promising candidate for the treatment of radioresistant oral squamous cell carcinoma

We evaluated the usefulness of an oncolytic virus (Suratadenoturev; OBP-301) against radioresistant oral squamous cell carcinoma. We confirmed the expression of human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor in cell lines. Also, we examined the potential presence in a patient who has received existing therapy that is amenable to treatment with OBP-301. We evaluated: (1) the antitumor effects of OBP-301 alone and in combination with radiotherapy on radioresistant cell lines, (2) the molecular mechanism underlying the radiosensitizing effect and cell death increased by the combination therapy, and (3) the antitumor effect of the combination therapy in vivo using xenograft models (a radioresistant cell line-derived xenograft in mouse and a patient-derived xenograft). Human telomerase reverse transcriptase and the coxsackievirus and adenovirus receptor were expressed in all cell lines. OBP-301 decreased the proliferative activity of these cell lines in a concentration-dependent manner, and significantly enhanced the antitumor effect of irradiation. Phosphorylated STAT3 and its downstream molecules, which correlated with apoptosis and autophagy, showed significant changes in expression after treatment with OBP-301. The combination therapy exerted a significant antitumor effect versus radiotherapy alone in both xenograft models. Combination of OBP-301 with radiotherapy exerts a synergistic effect and may represent a promising treatment for radioresistant oral squamous cell carcinoma.

Identification of rs2736099 as a novel cis-regulatory variation for TERT and implications for tumorigenesis and cell proliferation

PURPOSE

Lung cancer is a malignant tumor with obvious genetic predisposition. Association studies have proposed that rs2853677, a SNP localizing at intron region of TERT (telomerase reverse transcriptase), is significantly associated with TERT expression, telomere length and eventually lung cancer risk. However, functional genomics work indicates that rs2853677 is not with the ability to alter gene expression. All these facts make us hypothesize that some other genetic variation(s) are in linkage disequilibrium (LD) with rs2853677 and influence TERT expression.

METHODS

LD pattern in rs2853677 nearby region was analyzed based on 1000 genomes data for three representative populations in the world and functional genomics research was performed for this locus.

RESULTS

Only one SNP, rs2736099, is in strong LD with rs2853677 in East Asian. Dual-luciferase reporter assay verifies that rs2736099 can regulate gene expression and should be the causal SNP for this disease. Through chromosome conformation capture assay, it is disclosed that the enhancer surrounding rs2736099 can interact with TERT promoter. Through chromatin immunoprecipitation, the transcription factor SP1 (Sp1 transcription factor) is recognized for the chromatin segment spanning rs2736099.

CONCLUSIONS

Our results provide the missing piece between genetic variation at this locus and lung cancer risk, which is also applied to tumorigenesis in other tissues and cell proliferation.

Tumor‐targeted fluorescence labeling systems for cancer diagnosis and treatment

Conventional imaging techniques are available for clinical identification of tumor sites. However, detecting metastatic tumor cells that are spreading from primary tumor sites using conventional imaging techniques remains difficult. In contrast, fluorescence‐based labeling systems are useful tools for detecting tumor cells at the single‐cell level in cancer research. The ability to detect fluorescent‐labeled tumor cells enables investigations of the biodistribution of tumor cells for the diagnosis and treatment of cancer. For example, the presence of fluorescent tumor cells in the peripheral blood of cancer patients is a predictive biomarker for early diagnosis of distant metastasis. The elimination of fluorescent tumor cells without damaging normal tissues is ideal for minimally invasive treatment of cancer. To capture fluorescent tumor cells within normal tissues, however, tumor‐specific activated target molecules are needed. This review focuses on recent advances in tumor‐targeted fluorescence labeling systems, in which indirect reporter labeling using tumor‐specific promoters is applied to fluorescence labeling of tumor cells for the diagnosis and treatment of cancer. Telomerase promoter‐dependent fluorescence labeling using replication‐competent viral vectors produces fluorescent proteins that can be used to detect and eliminate telomerase‐positive tumor cells. Tissue‐specific promoter‐dependent fluorescence labeling enables identification of specific tumor cells. Vimentin promoter‐dependent fluorescence labeling is a useful tool for identifying tumor cells that undergo epithelial–mesenchymal transition (EMT). The evaluation of tumor cells undergoing EMT is important for accurately assessing metastatic potential. Thus, tumor‐targeted fluorescence labeling systems represent novel platforms that enable the capture of tumor cells for the diagnosis and treatment of cancer.

A Pleiotropic Role of the Hepatitis B Virus Core Protein in Hepatocarcinogenesis

Chronic hepatitis B virus (HBV) infection is one of the most common factors associated with hepatocellular carcinoma (HCC), which is the sixth most prevalent cancer among all cancers worldwide. However, the pathogenesis of HBV-mediated hepatocarcinogenesis is unclear. Evidence currently available suggests that the HBV core protein (HBc) plays a potential role in the development of HCC, such as the HBV X protein. The core protein, which is the structural component of the viral nucleocapsid, contributes to almost every stage of the HBV life cycle and occupies diverse roles in HBV replication and pathogenesis. Recent studies have shown that HBc was able to disrupt various pathways involved in liver carcinogenesis: the signaling pathways implicated in migration and proliferation of hepatoma cells, apoptosis pathways, and cell metabolic pathways inducing the development of HCC; and the immune system, through the expression and production of proinflammatory cytokines. In addition, HBc can modulate normal functions of hepatocytes through disrupting human host gene expression by binding to promoter regions. This HBV protein also promotes HCC metastasis through epigenetic alterations, such as micro-RNA. This review focuses on the molecular pathogenesis of the HBc protein in HBV-induced HCC.

Impact of aging on primary liver cancer: epidemiology, pathogenesis and therapeutics

Aging involves progressive physiological and metabolic reprogramming to adapt to gradual deterioration of organs and functions. This includes mechanisms of defense against pre-malignant transformations. Thus, certain tumors are more prone to appear in elderly patients. This is the case of the two most frequent types of primary liver cancer, i.e., hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA). Accordingly, aging hallmarks, such as genomic instability, telomere attrition, epigenetic alterations, altered proteostasis, mitochondrial dysfunction, cellular senescence, exhaustion of stem cell niches, impaired intracellular communication, and deregulated nutrient sensing can play an important role in liver carcinogenesis in the elders. In addition, increased liver fragility determines a worse response to risk factors, which more frequently affect the aged population. This, together with the difficulty to carry out an early detection of HCC and iCCA, accounts for the late diagnosis of these tumors, which usually occurs in patients with approximately 60 and 70 years, respectively. Furthermore, there has been a considerable controversy on what treatment should be used in the management of HCC and iCCA in elderly patients. The consensus reached by numerous studies that have investigated the feasibility and safety of different curative and palliative therapeutic approaches in elders with liver tumors is that advanced age itself is not a contraindication for specific treatments, although the frequent presence of comorbidities in these individuals should be taken into consideration for their management.

Controversial roles of cold‑inducible RNA‑binding protein in human cancer (Review)

Cold‑inducible RNA‑binding protein (CIRBP) is a cold‑shock protein comprised of an RNA‑binding motif that is induced by several stressors, such as cold shock, UV radiation, nutrient deprivation, reactive oxygen species and hypoxia. CIRBP can modulate post‑transcriptional regulation of target mRNA, which is required to control DNA repair, circadian rhythms, cell growth, telomere integrity and cardiac physiology. In addition, the crucial function of CIRBP in various human diseases, including cancers and inflammatory disease, has been reported. Although CIRBP is primarily considered to be an oncogene, it may also serve a role in tumor suppression. In the present study, the controversial roles of CIRBP in various human cancers is summarized, with a focus on the interconnectivity between CIRBP and its target mRNAs involved in tumorigenesis. CIRBP may represent an important prognostic marker and therapeutic target for cancer therapy.

Adipose Tissue-Derived Extracellular Vesicles and the Tumor Microenvironment: Revisiting the Hallmarks of Cancer

Extracellular vesicles (EVs) are crucial elements that sustain the communication between tumor cells and their microenvironment, and have emerged as a widespread mechanism of tumor formation and metastasis. In obesity, the adipose tissue becomes hypertrophic and hyperplastic, triggering increased production of pro-inflammatory adipokines, such as tumor necrosis factor α, interleukin 6, interleukin 1, and leptin. Furthermore, obese adipose tissue undergoes dysregulation in the cargo content of the released EVs, resulting in an increased content of pro-inflammatory proteins, fatty acids, and oncogenic microRNAs. These alterations drive obesity-associated inflammatory responses both locally and systemically. After being ignored for a long time, adipose tissues have recently received considerable attention as a major player in tumor microenvironment-linked obesity and cancer. The role of adipose tissue in the establishment and progression of cancer is reinforced by its high plasticity and inflammatory content. Such a relationship may be established by direct contact between adipocytes and cancer cells within the microenvironment or systemically, via EV-mediated cell-to-cell communication. Here, we highlight cues evidencing the influence of adipose tissue-derived EVs on the hallmarks of cancer, which are critical for tumor malignancy.

Telomere shortening and expression of TRF1 and TRF2 in uterine leiomyoma

Uterine leiomyoma is a benign smooth muscle tumor of the uterus that can exhibit histopathological traits that mimic malignancy. Telomere shortening is an early event in tumorigenesis and telomerase activation facilitates tumor progression later in the course of carcinogenesis. Telomeric repeat‑binding factor (TRF)1 and TRF2 protect telomeres, and their gene expression levels are dysregulated in various cancer types. However, the roles of telomeres and telomere protection proteins in uterine leiomyoma remain largely unknown. In this study, telomere length and the mRNA levels of various telomere‑related genes in normal tissues and leiomyoma were determined, and their relationships were evaluated. Uterine leiomyoma and normal myometrium were surgically obtained from 18 and 13 patients, respectively. Telomere length and gene expression were determined by Southern blot analysis and reverse transcription‑quantitative PCR, respectively. In matched samples, telomeres were consistently shorter in leiomyoma tissue than in adjacent normal tissue. TRF1, TRF2, PIN2‑interacting telomerase inhibitor 1 (PINX1), and telomerase RNA component were expressed at comparable levels in both leiomyoma and normal tissues. None of these genes were associated with telomere length in leiomyoma. All tested tissues were negative for telomerase reverse transcriptase, which encodes the catalytic component of telomerase, indicating that cells in uterine leiomyoma were not immortalized. In summary, telomere erosion, which reflects active proliferation during tumor evolution, was evident in uterine leiomyoma. Steady‑state expression of TRF1, TRF2 and PINX1 may be important for maintenance of telomere integrity in leiomyoma, where telomere length is shortened.

Prognostic Alternative Splicing Signatures in Esophageal Carcinoma

Alternative splicing (AS) is a method of increasing the number of proteins that the genome is capable of coding for, by altering the pre-mRNA during its maturation. This process provides the ability of a broad range of proteins to arise from a single gene. AS events are known to occur in up to 94% of human genes. Cumulative data have shown that aberrant AS functionality is a major factor in human diseases. This review focuses on the contribution made by aberrant AS functionality in the development and progression of esophageal cancer. The changes in the pattern of expression of alternately spliced isoforms in esophageal cancer can be used as diagnostic or prognostic biomarkers. Additionally, these can be used as targets for the development of new treatments for esophageal cancer.

Immune Phenotype and Immune Checkpoint Inhibitors for the Treatment of Human Hepatocellular Carcinoma

Immunotherapies are promising approaches for treating hepatocellular carcinomas (HCCs) refractory to conventional therapies. However, a recent clinical trial of immune checkpoint inhibitors (ICIs) revealed that anti-tumor responses to ICIs are not satisfactory in HCC cases. Therefore, it is critical to identify molecular markers to predict outcome and develop novel combination therapies that enhance the efficacy of ICIs. Recently, several attempts have been made to classify HCC based on genome, epigenome, and transcriptome analyses. These molecular classifications are characterized by unique clinical and histological features of HCC, as well immune phenotype. For example, HCCs exhibiting gene expression patterns with proliferation signals and stem cell markers are associated with the enrichment of immune infiltrates in tumors, suggesting immune-proficient characteristics for this type of HCC. However, the presence of activating mutations in β-catenin represents a lack of immune infiltrates and refractoriness to ICIs. Although the precise mechanism that links the immunological phenotype with molecular features remains controversial, it is conceivable that alterations of oncogenic cellular signaling in cancer may lead to the expression of immune-regulatory molecules and result in the acquisition of specific immunological microenvironments for each case of HCC. Therefore, these molecular and immune characteristics should be considered for the management of HCC using immunotherapy.

Bone and Soft-Tissue Sarcoma: A New Target for Telomerase-Specific Oncolytic Virotherapy

Adenovirus serotype 5 (Ad5) is widely and frequently used as a virus vector in cancer gene therapy and oncolytic virotherapy. Oncolytic virotherapy is a novel antitumor treatment for inducing lytic cell death in tumor cells without affecting normal cells. Based on the Ad5 genome, we have generated three types of telomerase-specific replication-competent oncolytic adenoviruses: OBP-301 (Telomelysin), green fluorescent protein (GFP)-expressing OBP-401 (TelomeScan), and tumor suppressor p53-armed OBP-702. These viruses drive the expression of the adenoviral E1A and E1B genes under the control of the hTERT (human telomerase reverse transcriptase-encoding gene) promoter, providing tumor-specific virus replication. This review focuses on the therapeutic potential of three hTERT promoter-driven oncolytic adenoviruses against bone and soft-tissue sarcoma cells with telomerase activity. OBP-301 induces the antitumor effect in monotherapy or combination therapy with chemotherapeutic drugs via induction of autophagy and apoptosis. OBP-401 enables visualization of sarcoma cells within normal tissues by serving as a tumor-specific labeling reagent for fluorescence-guided surgery via induction of GFP expression. OBP-702 exhibits a profound antitumor effect in OBP-301-resistant sarcoma cells via activation of the p53 signaling pathway. Taken together, telomerase-specific oncolytic adenoviruses are promising antitumor reagents that are expected to provide novel therapeutic options for the treatment of bone and soft-tissue sarcomas.

Advances in molecular classification and precision oncology in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) arises from hepatocytes through the sequential accumulation of multiple genomic and epigenomic alterations resulting from Darwinian selection. Genes from various signalling pathways such as telomere maintenance, Wnt/β-catenin, P53/cell cycle regulation, oxidative stress, epigenetic modifiers, AKT/mTOR and MAP kinase are frequently mutated in HCC. Several subclasses of HCC have been identified based on transcriptomic dysregulation and genetic alterations that are closely related to risk factors, pathological features and prognosis. Undoubtedly, integration of data obtained from both preclinical models and human studies can help to accelerate the identification of robust predictive biomarkers of response to targeted biotherapy and immunotherapy. The aim of this review is to describe the main advances in HCC in terms of molecular biology and to discuss how this knowledge could be used in clinical practice in the future.

Telomere Maintenance in Pediatric Cancer

Telomere length has been proposed as a biomarker of biological age and a risk factor for age-related diseases and cancer. Substantial progress has been made in recent decades in understanding the complex molecular relationships in this research field. However, the majority of telomere studies have been conducted in adults. The data on telomere dynamics in pediatric cancers is limited, and interpretation can be challenging, especially in cases where results are contrasting to those in adult entities. This review describes recent advances in the molecular characterization of structure and function of telomeres, regulation of telomerase activity in cancer pathogenesis in general, and highlights the key advances that have expanded our views on telomere biology in pediatric cancer, with special emphasis on the central role of telomere maintenance in neuroblastoma. Furthermore, open questions in the field of telomere maintenance research are discussed in the context of recently published literature.

The role of telomeres and telomerase in cirrhosis and liver cancer

Telomerase is a key enzyme for cell survival that prevents telomere shortening and the subsequent cellular senescence that is observed after many rounds of cell division. In contrast, inactivation of telomerase is observed in most cells of the adult liver. Absence of telomerase activity and shortening of telomeres has been implicated in hepatocyte senescence and the development of cirrhosis, a chronic liver disease that can lead to hepatocellular carcinoma (HCC) development. During hepatocarcinogenesis, telomerase reactivation is required to enable the uncontrolled cell proliferation that leads to malignant transformation and HCC development. Part of the telomerase complex, telomerase reverse transcriptase, is encoded by TERT, and several mechanisms of telomerase reactivation have been described in HCC that include somatic TERT promoter mutations, TERT amplification, TERT translocation and viral insertion into the TERT gene. An understanding of the role of telomeres and telomerase in HCC development is important to develop future targeted therapies and improve survival of this disease. In this Review, the roles of telomeres and telomerase in liver carcinogenesis are discussed, in addition to their potential translation to clinical practice as biomarkers and therapeutic targets.

Multidisciplinary oncolytic virotherapy for gastrointestinal cancer

Replication-selective tumor-specific viruses represent a novel approach for treating neoplastic diseases. These vectors are designed to induce virus-mediated lysis of tumor cells after selective intracellular virus propagation. For targeting cancer cells, the use of tissue- or cell-specific promoters that are expressed in diverse tumor types but silent in normal cells is required. Human telomerase is highly active in more than 85% of primary cancers, regardless of tissue origin, and its activity is closely correlated with human telomerase reverse transcriptase (hTERT) expression. We constructed an attenuated adenovirus 5 vector (telomelysin, OBP-301) in which the hTERT promoter element drives expression of E1 genes. As only tumor cells that express the telomerase can activate this promoter, the hTERT proximal promoter allows for preferential expression of viral genes in tumor cells, leading to selective viral replication and oncolytic cell death. Upon US Food and Drug Administration approval, a phase 1 dose-escalation study of intratumoral injection of telomelysin for various solid tumors has been completed to confirm the safety, tolerability, and feasibility of the agent. Moreover, we found that adenoviral E1B 55-kDa protein in telomelysin inhibits the radiation-induced DNA repair machinery. Thus, tumor cells infected with telomelysin could be rendered sensitive to ionizing radiation. Recently, we assessed the safety and efficacy of intratumoral injection of telomelysin with radiotherapy in esophageal cancer patients not suited for standard treatments. This review highlights some very promising clinical advances in cancer therapeutic technologies using telomerase-specific oncolytic virotherapy.

Clinicopathological Analysis of HIF-1alpha and TERT on Survival Outcome in Glioblastoma Patients: A Prospective, Single Institution Study

Glioblastoma multiforme is a highly malignant and aggressive primary brain tumor with a dismal prognosis. We studied the association of immunohistochemical expression of hypoxia inducible factor-1 alpha (HIF-1α), telomerase reverse transcriptase (TERT), isocitrate dehydrogenase 1 (IDH1) and tumor protein p53 with overall survival (OS) in glioblastoma patients uniformly treated by standard of care, with adequate follow-up. In 87 patient samples studied, 59 were male and 28 were female. The median age was 55 years. The median follow-up was 27.7 months and the median overall survival was 14.9 months. Nuclear staining of HIF-1α was expressed in all samples and scored as strong in 42 (48%) and weak in 45 (52%). Multivariable Cox regression revealed strong HIF-1α expression as an independent poor prognostic factor (Hazard Ratio 2.12, 95% CI 1.20 - 3.74, P = 0.01). There was a statistically significant difference in OS (9.8 months vs. 16.3 months) between the “HIF-1α - strong and TERT - strong” and the “HIF-1α - weak and TERT - weak” patient subgroups, as evaluated by Kaplan-Meier analysis (P = 0.005). In our study, HIF-1α expression was an independent predictor of OS. The subgroup of patients with strong expression of both HIF-1α and TERT had the poorest prognosis.

HPV E6/E7, hTERT, and Ki67 mRNA RT-qPCR Assay for Detecting High-Grade Cervical Lesion with Microscope Slides

After breast and colon cancer, cervical cancer is the third most common cancer of women worldwide. Since human papillomavirus (HPV) infection is known to be the predominant cause of cervical cancer, molecular HPV screening is currently used along with cytological and histological examination methods for precancer diagnosis. Nevertheless, the sensitivity of the current HPV test is less than 80%; thus, many cervical cancer cases are not able to be diagnosed by HPV screening alone, and likewise, patients with cervical cancer are often determined to be HPV-negative by the current screening methods. Therefore, human telomerase reverse transcriptase (hTERT) and Ki67 previously identified as cancer markers were attempted. And cervical exfoliated cells of high-grade squamous intraepithelial lesion (HSIL), the most severe precancerous lesion of cancer, were used in the study. However, it takes a long time to collect enough specimens to conduct statistical analysis. Therefore, in the present study, microscope slides, cervical exfoliated cells on glass slides, were attempted. The results of the analysis demonstrated that hTERT and Ki67 expression levels were useful in distinguishing between cancerous and normal specimens, exhibiting a higher sensitivity and specificity than conventional HPV E6/E7 testing. And the study suggests clinical slide cell samples could be effectively used in the context of retrospective studies to identify novel biomarkers.

Identification of genes involved in the regulation of TERT in hepatocellular carcinoma

Telomerase reverse transcriptase (TERT) promotes immortalization by protecting telomeres in cancer cells. Mutation of the TERT promoter is one of the most common genetic alterations in hepatocellular carcinoma (HCC), indicating that TERT upregulation is a critical event in hepatocarcinogenesis. Regulators of TERT transcription are, therefore, predicted to be plausible targets for HCC treatment. We undertook a genome‐wide shRNA library screen and identified C15orf55 and C7orf43 as regulators of TERT expression in HepG2 cells. Promoter assays showed that C15orf55‐ and C7orf43‐responsive sites exist between base pairs −58 and +36 and −169 and −59 in the TERT promoter, respectively. C15orf55 upregulates TERT expression by binding to two GC motifs in the SP1 binding site of the TERT promoter. C7orf43 upregulates TERT expression through Yes‐associated protein 1. The expression levels of C15orf55 and C7orf43 also correlated with that of TERT, and were significantly increased in both HCC tissues and their adjacent non‐tumor tissues, compared to normal liver tissues from non‐HCC patients. Analysis of 377 HCC patients in The Cancer Genome Atlas dataset showed that overall survival of patients with low levels of C15orf55 and C7orf43 expression in tumor tissues was better compared with patients with high levels of C15orf55 and/or high C7orf43 expression. These results indicate that C15orf55 and C7orf43 are involved in the incidence and progression of HCC by upregulating TERT. In conclusion, we identified C15orf55 and C7orf43 as positive regulators of TERT expression in HCC tissues. These genes are promising targets for HCC treatment.

Correlation of human telomerase reverse transcriptase single nucleotide polymorphisms with in vitro fertilisation outcomes

PURPOSE

To explore whether it is possible to predict the number and quality of the embryo using a few particular hTERT SNPs.

METHODS

We included 997 Han Chinese women who were genetically unrelated and underwent assisted reproduction using IVF from September 2014 to December 2015. DNA was genotyped by using TaqMan real-time quantitative PCR.

RESULTS

Among the 997 patients, individuals with the CC genotype of rs2075786 had a significantly lower number of good-quality embryos than those with the TT+TC genotypes. Compared with the CT+CC genotype carriers, patients carrying the TT genotype of rs2853677 had a significantly lower number of oocytes retrieved, mature oocytes and available embryos. Among the 750 patients aged ≤ 35 years, individuals with the AA+AG genotypes of rs2853691 had a significantly higher number of good-quality embryos than those with the GG genotype. The haplotype analysis showed that the TTTG (rs2853672/rs2853669/rs2735940/rs2736108) haplotype was more likely to lead to more than three good-quality embryos in patients aged ≤ 35 years.

CONCLUSIONS

Our study suggests that the hTERT SNP is associated with IVF outcomes.

Preliminary development of an assay for detection of TERT expression, telomere length, and telomere elongation in single cells

The telomerase enzyme enables unlimited proliferation of most human cancer cells by elongating telomeres and preventing replicative senescence. Despite the critical importance of telomerase in cancer biology, challenges detecting telomerase activity and expression in individual cells have hindered the ability to study patterns of telomerase expression and function across heterogeneous cell populations. While sensitive assays to ascertain telomerase expression and function exist, these approaches have proven difficult to implement at the single cell level. Here, we validate in situ RNAscope detection of the telomerase TERT mRNA and couple this assay with our recently described TSQ1 method for in situ detection of telomere elongation. This approach enables detection of TERT expression, telomere length, and telomere elongation within individual cells of the population. Using this assay, we show that the heterogeneous telomere elongation observed across a HeLa cell population is in part driven by variable expression of the TERT gene. Furthermore, we show that the absence of detectable telomere elongation in some TERT-positive cells is the result of inhibition by the telomeric shelterin complex. This combined assay provides a new approach for understanding the integrated expression, function, and regulation of telomerase at the single cell level.

Integrated fluorescent cytology with nano-biologics in peritoneally disseminated gastric cancer

Gastric cancer patients positive for peritoneal cytology are at increased risk of tumor recurrence, but although a certain proportion of cytology‐positive patients relapse rapidly with aggressive progression, others survive longer with conventional chemotherapies. This heterogeneity makes it difficult to stratify patients for more intensive therapy and poses a substantial challenge for the implementation of precision medicine. We developed a new approach to identify biologically malignant subpopulations in cytology‐positive gastric cancer patients, using a green fluorescent protein (GFP)‐expressing attenuated adenovirus in which the telomerase promoter regulates viral replication (TelomeScan, OBP‐401). The fluorescence emitted from TelomeScan‐positive cells was successfully quantified using a multi‐mode microplate reader. We then analyzed clinical peritoneal washes obtained from 68 gastric cancer patients and found that patients positive for TelomeScan had a significantly worse prognosis. In 21 cytology‐positive patients, the median survival time of those who were TelomeScan positive (235 days) was significantly shorter than that for those who were TelomeScan negative (671 days; P = 0.0062). This fluorescent virus‐guided cytology detects biologically malignant cancer cells from the peritoneal washes of gastric cancer patients and may thus be useful for both therapy stratification and precision medicine approaches based on genetic profiling of disseminated cells.

Tumor specific mutations in TERT promoter and CTNNB1 gene in hepatitis B and hepatitis C related hepatocellular carcinoma

Recurrent somatic mutations in the promoter region of telomerase reverse transcriptase (TERT) gene and in the exon 3 of CTNNB1 gene have been recognized as common events in hepatocellular carcinoma (HCC) with variable frequencies depending on etiology and geographical region. We have analyzed TERT promoter and CTNNB1 gene mutations in 122 cases of hepatitis B (HBV) and hepatitis C (HCV) related HCCs, in 7 cases of cholangiocarcinoma (CC) and hepatocholangiocarcinoma (HCC-CC) as well as in autologous cirrhotic tissues. Overall, 50.4% and 26% of HCC as well as 14.3% and none of CC and HCC-CC were mutated in TERT promoter and in CTNNB1 exon 3, respectively. TERT and CTNNB1 mutations were found more frequently in HCV related (53.6% and 26.4%, respectively) than HBV related (41.7% and 16.7%, respectively) HCCs and coexisted in 57.6% of CTNNB1 mutated tumors. Mutations in TERT and CTNNB1 were not associated with the functional promoter polymorphism rs2853669. No mutations were detected in the 129 non-HCC cirrhotic tissues. In conclusion, mutations in TERT promoter and in CTNNB1 gene represent specific cancer signatures in the pathogenesis of viral related HCC and could be promising early biomarkers as well as targets for tailored therapies.

Stretching, scrambling, piercing and entangling: Challenges for telomeres in mitotic and meiotic chromosome segregation

The consequences of telomere loss or dysfunction become most prominent when cells enter the nuclear division stage of the cell cycle. At this climactic stage when chromosome segregation occurs, telomere fusions or entanglements can lead to chromosome breakage, wreaking havoc on genome stability. Here we review recent progress in understanding the mechanisms of detangling and breaking telomere associations at mitosis, as well as the unique ways in which telomeres are processed to allow regulated sister telomere separation. Moreover, we discuss unexpected roles for telomeres in orchestrating nuclear envelope breakdown and spindle formation, crucial processes for nuclear division. Finally, we discuss the discovery that telomeres create microdomains in the nucleus that are conducive to centromere assembly, cementing the unexpectedly influential role of telomeres in mitosis.

Telomeres in cancer

Telomere shortening as a consequence of cell divisions during aging and chronic diseases associates with an increased cancer risk. Experimental data revealed that telomere shortening results in telomere dysfunction, which in turn affects tumorigenesis in two ways. First, telomere dysfunction suppresses tumor progression by the activation of DNA damage checkpoints, which induce cell cycle arrest (senescence) or apoptosis, as well as by inducing metabolic compromise and activation of immune responses directed against senescent cells. Second, telomere dysfunction promotes tumorigenesis by inducing chromosomal instability in tumor initiating cells, by inhibiting proliferative competition of non-transformed cells, and possibly, also by influencing tumor cell plasticity. The tumor promoting effects of telomere dysfunction are context dependent and require the loss of p53-dependent DNA damage checkpoints or other genetic modifiers that attenuate DNA damage responses possibly involving complex interactions of different genes. The activation of telomere stabilizing mechanisms appears as a subsequent step, which is required to enable immortal grotwh of emerging cancer cells. Here, we conceptually discuss our current knowledge and new, unpublished experimental data on telomere dependent influences on tumor initiation and progression.

Assessment of in Vitro Applicability of Reversibly Immortalized NKNT-3 Cells and Clonal Derivatives

In vitro applications of human hepatocytes, such as bioartificial livers and toxicity assays, require thoroughly testing of human cell lines prior to using them as alternative cell sources. The reversibly immortalized NKNT-3 cell line was reported to show clear in vivo functionality. Here, NKNT-3 cells were tested for their in vitro applicability. Low-passage (P2) and high-passage (P28) NKNT-3 cells and clonal derivatives were characterized for reversion of immortalization, heterogeneity, and hepatic functionality. Reversion with reduced expression of immortalizing agent could be established. However, during culturing the cells lost the capacity to be selected for completed reversion. The phenotypic instability is probably associated with heterogeneity in the culture, as clonal derivatives of P2 cells varied in morphology, growth, and reversion characteristics. The mRNA levels of genes related with hepatic differentiation increased 4–20-fold after reversion. However, the levels never exceeded 0.1% of that detected in liver and no urea production nor ammonia elimination was detected. Additionally, activities of different cytochrome P450s were limited. In conclusion, the NKNT-3 culture is heterogeneous and unstable and the in vitro functionality is relatively low. These findings emphasize that in vivo testing of hepatic cell lines is little informative for predicting their value for in vitro applications.

Frequency and geographic distribution of TERT promoter mutations in primary hepatocellular carcinoma

Primary hepatocellular carcinoma (HCC) mainly develops in subjects chronically infected with hepatitis B (HBV) and C (HCV) viruses through a multistep process characterized by the accumulation of genetic alterations in the human genome. Nucleotide changes in coding regions (i.e. TP53, CTNNB1, ARID1A and ARID2) as well as in non-coding regions (i.e. TERT promoter) are considered cancer drivers for HCC development with variable frequencies in different geographic regions depending on the etiology and environmental factors. Recurrent hot spot mutations in TERT promoter (G > A at-124 bp; G > A at -146 bp), have shown to be common events in many tumor types including HCC and to up regulate the expression of telomerases. We performed a comprehensive review of the literature evaluating the differential distribution of TERT promoter mutations in 1939 primary HCC from four continents. Mutation rates were found higher in Europe (56.6%) and Africa (53.3%) than America (40%) and Asia (42.5%). In addition, HCV-related HCC were more frequently mutated (44.8% in US and 69.7% in Asia) than HBV-related HCC (21.4% in US and 45.5% in Africa). HCC cases associated to factors other than hepatitis viruses are also frequently mutated in TERT promoter (43.6%, 52.6% and 57.7% in USA, Asia and Europe, respectively). These results support a major role for telomere elongation in HCV-related and non-viral related hepatic carcinogenesis and suggest that TERT promoter mutations could represent a candidate biomarker for the early detection of liver cancer in subjects with HCV infection or with metabolic liver diseases.

NMI inhibits cancer stem cell traits by downregulating hTERT in breast cancer

N-myc and STAT interactor (NMI) has been proved to bind to different transcription factors to regulate a variety of signaling mechanisms including DNA damage, cell cycle and epithelial–mesenchymal transition. However, the role of NMI in the regulation of cancer stem cells (CSCs) remains poorly understood. In this study, we investigated the regulation of NMI on CSCs traits in breast cancer and uncovered the underlying molecular mechanisms. We found that NMI was lowly expressed in breast cancer stem cells (BCSCs)-enriched populations. Knockdown of NMI promoted CSCs traits while its overexpression inhibited CSCs traits, including the expression of CSC-related markers, the number of CD44⁺CD24⁻ cell populations and the ability of mammospheres formation. We also found that NMI-mediated regulation of BCSCs traits was at least partially realized through the modulation of hTERT signaling. NMI knockdown upregulated hTERT expression while its overexpression downregulated hTERT in breast cancer cells, and the changes in CSCs traits and cell invasion ability mediated by NMI were rescued by hTERT. The in vivo study also validated that NMI knockdown promoted breast cancer growth by upregulating hTERT signaling in a mouse model. Moreover, further analyses for the clinical samples demonstrated that NMI expression was negatively correlated with hTERT expression and the low NMI/high hTERT expression was associated with the worse status of clinical TNM stages in breast cancer patients. Furthermore, we demonstrated that the interaction of YY1 protein with NMI and its involvement in NMI-mediated transcriptional regulation of hTERT in breast cancer cells. Collectively, our results provide new insights into understanding the regulatory mechanism of CSCs and suggest that the NMI-YY1-hTERT signaling axis may be a potential therapeutic target for breast cancers.

The protein subunit of telomerase displays patterns of dynamic evolution and conservation across different metazoan taxa

BACKGROUND

Most animals employ telomerase, which consists of a catalytic subunit known as the telomerase reverse transcriptase (TERT) and an RNA template, to maintain telomere ends. Given the importance of TERT and telomere biology in core metazoan life history traits, like ageing and the control of somatic cell proliferation, we hypothesised that TERT would have patterns of sequence and regulatory evolution reflecting the diverse life histories across the Animal Kingdom.

RESULTS

We performed a complete investigation of the evolutionary history of TERT across animals. We show that although TERT is almost ubiquitous across Metazoa, it has undergone substantial sequence evolution within canonical motifs. Beyond the known canonical motifs, we also identify and compare regions that are highly variable between lineages, but show conservation within phyla. Recent data have highlighted the importance of alternative splice forms of TERT in non-canonical functions and although animals may share some conserved introns, we find that the selection of exons for alternative splicing appears to be highly variable, and regulation by alternative splicing appears to be a very dynamic feature of TERT evolution. We show that even within a closely related group of triclad flatworms, where alternative splicing of TERT was previously correlated with reproductive strategy, we observe highly diverse splicing patterns.

CONCLUSIONS

Our work establishes that the evolutionary history and structural evolution of TERT involves previously unappreciated levels of change and the emergence of lineage specific motifs. The sequence conservation we describe within phyla suggests that these new motifs likely serve essential biological functions of TERT, which along with changes in splicing, underpin diverse functions of TERT important for animal life histories.

Telomerase Inhibitory Effects of Red Pigment Rubropunctatin and Statin Monacolin L Isolated from Red Yeast Rice

In addition to the cholesterol-lowering activity of red yeast rice (RYR), its anticancer activities have been frequently reported. However, the mechanism of action of the anticancer activity of RYR is not yet fully understood. The objective of the current study was to elucidate anticancer compositions and anticancer mechanism of actions of RYR. The isolated compounds from RYR were subjected to anti-proliferation assay, apoptosis assay via flow cytometry, and telomerase inhibitory assay via telomeric repeat amplification protocol-PCR (TRAP-PCR) assay, and Western blotting assay in an in vitro cell culture system. The results showed that a statin, monacolin L, and a red pigment, rubropunctatin, from RYR exhibited very strong cancer cell proliferation inhibitory effects; the rubropunctatin was comparable with anticancer drug cis-platinum, taxol, and 10-hydroxy-camptothecin (HCPT) in their IC₅₀ values. Monacolin L and rubropunctatin exerted their anticancer activity via telomerase inhibitory effects. Monacolin L and rubropunctatin presented the similar telomerase inhibitory effects as the anticancer drug cis-platinum, while the anticancer drug HCPT presented a weak telomerase inhibitory effect in the TRAP-PCR assay. Meanwhile, rubropunctatin and cis-platinum did not present strong apoptosis induction activity as the momacolin L and HCPT did. These results indicate that the RYR may exert anticancer effects through the telomerase inhibitory effect of rubropunctatin and the apoptosis-induction effect of monacolin L.

Variable TERRA abundance and stability in cervical cancer cells

Telomeres are transcribed into long non-coding RNA, referred to as telomeric repeat-containing RNA (TERRA), which plays important roles in maintaining telomere integrity and heterochromatin formation. TERRA has been well characterized in HeLa cells, a type of cervical cancer cell. However, TERRA abundance and stability have not been examined in other cervical cancer cells, at least to the best of our knowledge. Thus, in this study, we measured TERRA levels and stability, as well as telomere length in 6 cervical cancer cell lines, HeLa, SiHa, CaSki, HeLa S3, C-33A and SNU-17. We also examined the association between the TERRA level and its stability and telomere length. We found that the TERRA level was several fold greater in the SiHa, CaSki, HeLa S3, C-33A and SNU-17 cells, than in the HeLa cells. An RNA stability assay of actinomycin D-treated cells revealed that TERRA had a short half-life of ~4 h in HeLa cells, which was consistent with previous studies, but was more stable with a longer half-life (>8 h) in the other 5 cell lines. Telomere length varied from 4 to 9 kb in the cells and did not correlate significantly with the TERRA level. On the whole, our data indicate that TERRA abundance and stability vary between different types of cervical cancer cells. TERRA degrades rapidly in HeLa cells, but is maintained stably in other cervical cancer cells that accumulate higher levels of TERRA. TERRA abundance is associated with the stability of RNA in cervical cancer cells, but is unlikely associated with telomere length.

Telomere G-Overhang Length Measurement Method 2: G-Tail Telomere HPA

Both telomere length and telomere G-tail length are altered in human diseases such as cancer and age-related diseases. While most methods for measurement of G-tail and telomere length require electrophoresis, centrifugation, radioisotope labeling and autoradiography, G-tail telomere HPA provides a convenient and useful tool for the examination of G-tail length with a high-throughput platform using genomic DNA or cell lysate. G-tail telomere HPA may be applicable for clinical diagnostics as well as drug target screening.

Genetic profiling of hepatocellular carcinoma using next-generation sequencing

Hepatocellular carcinoma (HCC) is a highly heterogeneous disease, both clinically and from a molecular standpoint. The advent of next-generation sequencing technologies has provided new opportunities to extensively analyze molecular defects in HCC samples. This has uncovered major cancer driver genes and associated oncogenic pathways operating in HCC. More sophisticated analyses of sequencing data have linked specific nucleotide patterns to external toxic agents and defined so-called 'mutational signatures' in HCC. Molecular signatures, taking into account intra- and inter-tumor heterogeneity, and their functional validation could provide useful data to predict treatment response to molecular therapies. In this review we will focus on the current knowledge of deep sequencing in HCC and its foreseeable clinical impact.

Upregulated long non-coding RNA BC032469 enhances carcinogenesis and metastasis of esophageal squamous cell carcinoma through regulating hTERT expression

Currently, long non-coding RNAs (lncRNAs) have been shown to have critical regulatory roles in various cancers. However, its role in esophageal squamous cell carcinoma (ESCC) remains largely unknown. Here, we focused on lncRNA BC032469, one of the lncRNAs involved in the development of ESCC. The levels of a specific differentially expressed lncRNA (termed lncRNA-BC032469) were measured in 45 paired esophageal squamous cell carcinoma tissue samples by quantitative real-time RT-PCR and then subjected to correlation analysis with clinical parameters and prognosis. The functions of lncRNA-BC032469 were evaluated by silencing and overexpressing the lncRNA in vitro and in vivo. The expression level of BC032469 in esophageal squamous cell carcinoma tissues was higher than that in the corresponding non-cancerous tissues. High BC032469 levels were correlated with lymph node metastasis, TNM stage, and tumor size and lower overall survival. Knockdown of BC032469 in TE13 and Eca109 cells inhibited cell proliferation, migration, and invasion; induced cell cycle arrest in the G0/G1 phase; and promoted apoptosis. Western blot analysis revealed that BC032469 regulated the expression of human telomerase reverse transcriptase (hTERT), which is important for cell proliferation and metastasis. Moreover, the restored expression of hTERT protein in BC032469-knockdown cells attenuated the suppressive effects of BC032469 on ESCC cells. Collectively, these results indicated that lncRNA-BC032469 is an oncogenic lncRNA that promotes tumor progression and leads us to propose that lncRNAs may serve as key regulatory hubs in ESCC development.

Telomerase Prolongs the Lifespan of Normal Human Ovarian Surface Epithelial Cells Without Inducing Neoplastic Phenotype

OBJECTIVE

The aim of this study was to determine the effects of exogenous expression of the catalytic subunit of telomerase (hTERT) on the lifespan, growth characteristics, and tumorigenicity of normal human ovarian surface epithelial (OSE) cells.

METHODS

Low-passage primary cultures of normal human OSE cells were transfected with hTERT and the resulting cell lines were characterized.

RESULTS

The ectopic expression of hTERT stabilized the telomeres of the OSE cultures above 8 kb. The hTERT-transfected OSE cell lines grew beyond the normal lifespan seen in OSE cells and propagated in culture for more than 40 passages before senescing. Moreover, the hTERT-transfected cells demonstrated extensive proliferative capacity as evidenced by their ability to continuously grow even when seeded at low dilutions. The morphologic features and normal differentiation patterns seen in normal OSE cells were likewise retained by the hTERT-transfected cells. In addition, the cultures remained responsive to physiologic concentrations of epidermal growth factor and transforming growth factor-beta. Changes associated with neoplastic transformation like anchorage-independent growth, tumorigencity and karyotypic instability were not observed.

CONCLUSIONS

We were able to show that the ectopic expression of hTERT in normal human OSE: 1) resulted in cultures with greater growth potential and longer lifespan and 2) did not induce a transformed phenotype previously seen in viral oncogene-transfected OSE cells. The established cell lines would not only provide sufficient material for comprehensive studies to investigate the normal physiology of OSE cells, but could also help in the understanding of the early steps of ovarian carcinogenesis.

A novel conditional gene silencing method using a tumor-specific and heat-inducible siRNA system

RNAi technology is an invaluable tool for investigating gene function. However, the non-temporal and non-spatial control is the primary limitation, which leads to siRNA leakiness and off-target effects. In this study, we inserted three kinds of HSE into tumor specific promoter hTERT, which aims to construct a temperature-inducible and tumor-specific RNAi plasmid vector. In our system, the expression of mature siRNA is tightly controlled by the heat shock-inducible and tumor-specific promoters. From the expression level of RNA and protein, we determined the efficiency of the inducible siRNA system by targeting SNCG gene in HepG2 and MCF-7 cells. Results showed that the controllable siRNA system could be induced to initiate siRNA expression by heat-induce. The silencing effect of SNCG is on a relative low level (10 %) at 37 °C, while it is significantly increased to 50 or 60 % after heat inducing at 43 °C. This new conditional siRNA system provides a novel approach to drive the siRNA expression by heat-inducible and tumor-specific promoter.

TERT Genetic Mutations as Prognostic Marker in Glioma

Telomerase reverse transcriptase (TERT) encodes the catalytic subunit of telomerase. The role of TERT in gliomagenesis has been extensively investigated. Since the influence of district, population, sample size, and experimental technology, our analysis, based on published articles, was aimed to obtain an accurate estimation of the relationship between TERT mutations and prognosis of glioma patients. PubMed, Web of science and Google Scholar databases were searched for potential articles. Finally, six studies with 2111 patients were included in the meta-analysis. Heterogeneity was evaluated by I² statistics and P value. I² > 50 % and P < 0.05 indicated significant heterogeneity between included studies and random-effects model was used; otherwise, fixed-effects model was used for analysis. The results of meta-analysis was expressed as hazard ratio (HR) and 95 % confidence interval (CI). The pooled results calculated by fixed-effects model suggested that TERT mutations were associated with poor prognosis of glioma patients (HR 1.68, 95 % CI 1.43-1.97). In conclusion, TERT mutations may be associated with shorter survival of glioma patients.

Nrf2-driven TERT regulates pentose phosphate pathway in glioblastoma

Given the involvement of telomerase activation and dysregulated metabolism in glioma progression, the connection between these two critical players was investigated. Pharmacological inhibition of human Telomerase reverse transcriptase (hTERT) by Costunolide induced glioma cell apoptosis in a reactive oxygen species (ROS)-dependent manner. Costunolide induced an ROS-dependent increase in p53 abrogated telomerase activity. Costunolide decreased Nrf2 level; and ectopic Nrf2 expression decreased Costunolide-induced ROS generation. While TERT knock-down abrogated Nrf2 levels, overexpression of Nrf2 increased TERT expression. Inhibition of hTERT either by Costunolide, or by siRNA or dominant-negative hTERT (DN-hTERT) abrogated (i) expression of Glucose-6-phosphate dehydrogenase (G6PD) and Transketolase (TKT) – two major nodes in the pentose phosphate (PPP) pathway; and (ii) phosphorylation of glycogen synthase (GS). hTERT knock-down decreased TKT activity and increased glycogen accumulation. Interestingly, siRNA-mediated knock-down of TKT elevated glycogen accumulation. Coherent with the in vitro findings, Costunolide reduced tumor burden in heterotypic xenograft glioma mouse model. Costunolide-treated tumors exhibited diminished TKT activity, heightened glycogen accumulation, and increased senescence. Importantly, glioblastoma multiforme (GBM) patient tumors bearing TERT promoter mutations (C228T and C250T) known to be associated with increased telomerase activity; exhibited elevated Nrf2 and TKT expression and decreased glycogen accumulation. Taken together, our findings highlight the previously unknown (i) role of telomerase in the regulation of PPP and glycogen accumulation and (ii) the involvement of Nrf2-TERT loop in maintaining oxidative defense responses in glioma cells.

Epigenetic reprogramming in mammalian species after SCNT-based cloning

The birth of "Dolly," the first mammal cloned from an adult mammary epithelial cell, abolished the decades-old scientific dogma implying that a terminally differentiated cell cannot be reprogrammed into a pluripotent embryonic state. The most dramatic epigenetic reprogramming occurs in SCNT when the expression profile of a differentiated cell is abolished and a new embryo-specific expression profile, involving 10,000 to 12,000 genes, and thus, most genes of the entire genome is established, which drives embryonic and fetal development. The initial release from somatic cell epigenetic constraints is followed by establishment of post-zygotic expression patterns, X-chromosome inactivation, and adjustment of telomere length. Somatic cell nuclear transfer may be associated with a variety of pathologic changes of the fetal and placental phenotype in a proportion of cloned offspring, specifically in ruminants, that are thought to be caused by aberrant epigenetic reprogramming. Improvements in our understanding of this dramatic epigenetic reprogramming event will be instrumental in realizing the great potential of SCNT for basic research and for important agricultural and biomedical applications. Here, current knowledge on epigenetic reprogramming after use of SCNT in livestock is reviewed, with emphasis on gene-specific and global DNA methylation, imprinting, X-chromosome inactivation, and telomere length restoration in early development.