TERT biology and function in cancer: beyond immortalisation

Transcriptome Profiling of Mouse Embryonic Fibroblast Spontaneous Immortalization: A Comparative Analysis

Cell immortalization, a hallmark of cancer development, is a process that cells can undergo on their path to carcinogenesis. Spontaneously immortalized mouse embryonic fibroblasts (MEFs) have been used for decades; however, changes in the global transcriptome during this process have been poorly described. In our research, we characterized the poly-A RNA transcriptome changes after spontaneous immortalization. To this end, differentially expressed genes (DEGs) were screened using DESeq2 and characterized by gene ontology enrichment analysis and protein-protein interaction (PPI) network analysis to identify the potential hub genes. In our study, we identified changes in the expression of genes involved in proliferation regulation, cell adhesion, immune response and transcriptional regulation in immortalized MEFs. In addition, we performed a comparative analysis with previously reported MEF immortalization data, where we propose a predicted gene regulatory network model in immortalized MEFs based on the altered expression of Mapk11, Cdh1, Chl1, Zic1, Hoxd10 and the novel hub genes Il6 and Itgb2.

TERC promotes non-small cell lung cancer progression by facilitating the nuclear localization of TERT

The core of telomerase consists of the protein subunit telomerase reverse transcriptase (TERT) and the telomerase RNA component (TERC). So far, the role of TERC in cancer development has remained elusive. Here, we found TERC expression elevated in non-small cell lung cancer (NSCLC) tissues, which was associated with disease progression and poor prognosis in patients. Using NSCLC cell lines and xenograft models, we showed that knockdown of TERC caused cell cycle arrest, and inhibition of cell proliferation and migration. Mechanistically, TERC was exported to the cytoplasm by nuclear RNA export factor 1 (NXF1), where it mediated the interaction of TERT with other telomerase subunits. Depletion of TERC hindered the assembly and subsequent nuclear localization of the telomerase complex, preventing TERT from functioning in telomere maintenance and transcription regulation. Our findings suggest that TERC is a potential biomarker for NSCLC diagnosis and prognosis and can be a target for NSCLC treatment.

LASSO regression and WGCNA-based telomerase-associated lncRNA signaling predicts clear cell renal cell carcinoma prognosis and immunotherapy response

OBJECTIVE

To investigate whether telomerase-associated lncRNA expression affects the prognosis and anti-tumor immunity of patients with renal clear cell carcinoma (ccRCC).

METHODS

A series of analyses were performed to establish a prognostic risk model and validate its accuracy. Immune-related analyses were performed to assess further the association between immune status, tumor microenvironment, and prognostic risk models.

RESULTS

Eight telomerase-associated lncRNAs associated with prognosis were identified and applied to establish a prognostic risk model. Overall survival was higher in the low-risk group.

CONCLUSION

The established prognostic risk model has a good predictive ability for the prognosis of ccRCC patients and provides a new possible therapeutic target for ccRCC.

Mechanistic influence of discreet conformation of human telomerase linker region

Approximately 90% of malignancies have been shown to have human telomerase activity, establishing it as a viable therapeutic target. The crystal structure of telomerase was determined recently. However, the tertiary structure of the non-conserved flexible linker region remains unresolved. This study aims to predict the full-length tertiary structure of the human telomerase reverse transcriptase (hTERT). Two strategies were employed to determine the full-length structure of hTERT (1132 amino acids); iterative threading and a conjoined model generated from machine learning and energy functions. After energy minimization, Ramachandran Plot analysis, and simulation; the conjoined model was considered of better quality and stability. The linker region of the conjoined depicted two helices from approximately 275-284 and 201-211 amino acids respectively in contrast to the iterative threading model which has a single helix. Moreover, the region was observed to undergo major structural changes throughout the simulation. These changes signify its flexibility which might be due to the region having a significant number of glycine and proline and could enhance the clamping movement.Communicated by Ramaswamy H. Sarma.

Multi-omic and functional analysis for classification and treatment of sarcomas with FUS-TFCP2 or EWSR1-TFCP2 fusions

Linking clinical multi-omics with mechanistic studies may improve the understanding of rare cancers. We leverage two precision oncology programs to investigate rhabdomyosarcoma with FUS/EWSR1-TFCP2 fusions, an orphan malignancy without effective therapies. All tumors exhibit outlier ALK expression, partly accompanied by intragenic deletions and aberrant splicing resulting in ALK variants that are oncogenic and sensitive to ALK inhibitors. Additionally, recurrent CKDN2A/MTAP co-deletions provide a rationale for PRMT5-targeted therapies. Functional studies show that FUS-TFCP2 blocks myogenic differentiation, induces transcription of ALK and truncated TERT, and inhibits DNA repair. Unlike other fusion-driven sarcomas, TFCP2-rearranged tumors exhibit genomic instability and signs of defective homologous recombination. DNA methylation profiling demonstrates a close relationship with undifferentiated sarcomas. In two patients, sarcoma was preceded by benign lesions carrying FUS-TFCP2, indicating stepwise sarcomagenesis. This study illustrates the potential of linking precision oncology with preclinical research to gain insight into the classification, pathogenesis, and therapeutic vulnerabilities of rare cancers.

TERT promoter mutations and gene amplification in endometrial cancer

OBJECTIVE

To assess the clinicopathologic, molecular profiles, and survival outcomes of patients with endometrial carcinomas (ECs) harboring telomerase reverse transcriptase (TERT) hotspot mutations or gene amplification.

METHODS

ECs harboring somatic TERT promoter hotspot mutations or gene amplification (TERT-altered) were identified from 1944 ECs that underwent clinical tumor-normal sequencing from 08/2016-12/2021. Clinicopathologic variables, somatic mutation profiles, and survival outcomes of TERT-alt and TERT-wild-type EC were assessed.

RESULTS

We identified 66 TERT-altered ECs (43 TERT-mutated and 23 TERT-amplified), representing 3% of the unselected ECs across histologic subtypes. Most TERT-altered ECs were of copy number (CN)-high/TP53abn molecular subtype (n = 40, 60%), followed by microsatellite-unstable (MSI-H) or CN-low/no specific molecular profile (NSMP)(n = 13, 20% each). TERT-amplified and TERT-mutated ECs were molecularly distinct, with TERT-amplified ECs being more genomically instable and more frequently harboring TP53 and PPP2R1A alterations (q < 0.1). Compared to TERT-wild-type ECs, TERT-altered ECs were more commonly of CN-H/TP53abn molecular subtype (31% vs 57%, p = 0.001), serous histology (10% vs 26%, p = 0.004), and were significantly enriched for TP53, CDKN2A/B, and DROSHA somatic genetic alterations (q < 0.1). Median progression-free survival was 18.7 months (95% CI 11.8-not estimable [NE]) for patients with TERT-altered EC and 80.9 months (65.8-NE) for patients with TERT-wild-type EC (HR 0.33, 95% CI 0.21-0.51, p < 0.001). Similarly, median overall survival was 46.7 months (95% CI 30-NE) for TERT-altered EC patients and not reached for TERT-wild-type EC patients (HR 0.24, 95% CI 0.13-0.44, p < 0.001).

CONCLUSION

TERT-altered ECs, although rare, are enriched for CN-high/TP53abn tumors, TP53, CDKN2A/B and DROSHA somatic mutations, and independently predict worse survival outcomes.

Telomerase Expression Related with Poor Immune Response to HCV Core Antigen in Egyptian HCV Patients' PBMCs

Background

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver.

Aim

This study aimed to assess serum human telomerase enzyme (hTERT) levels and their relation to the progression of liver disease. Also, it aimed to assess the effect of hepatitis C virus (HCV) core protein on memory T-cells in HCV patients with or without HCC and the correlation between memory cell phenotype and the progression of the disease in the same patients.

Methods

HTERT level in serum was assessed through relative quantitative RT-PCR. Flow cytometric analysis was used to assess T-cell responsiveness (as IFN- γ secretion) before and after stimulation with HCV core protein and the memory CD8+ cell phenotype using several differentiation markers.

Results

HTERT was found to be increased in a stepwise manner upon comparing its level in controls, chronic hepatitis patients, cirrhotic patients, and HCC patients. T-cells showed a similar manner of stepwise decrease in response (decreased IFN- γ secretion) in HCC patients compared to HCV patients without HCC and controls. Also, late differentiated memory cells (CD8+, CD27-, CD28-, CD45RA+, and CCR7-) were depleted in HCC patients compared to HCV patients without HCC.

Conclusion

These results suggest a negative correlation between hTERT and IFN- γ secretion by T-cells in HCV patients and that this relationship, along with the depletion of late differentiated memory cells, could help the progression of liver disease to HCC.

The m5 C methyltransferase NSUN2 promotes codon-dependent oncogenic translation by stabilising tRNA in anaplastic thyroid cancer

BACKGROUND

Translation dysregulation plays a crucial role in tumourigenesis and cancer progression. Oncogenic translation relies on the stability and availability of tRNAs for protein synthesis, making them potential targets for cancer therapy.

METHODS

This study performed immunohistochemistry analysis to assess NSUN2 levels in thyroid cancer. Furthermore, to elucidate the impact of NSUN2 on anaplastic thyroid cancer (ATC) malignancy, phenotypic assays were conducted. Drug inhibition and time-dependent plots were employed to analyse drug resistance. Liquid chromatography-mass spectrometry and bisulphite sequencing were used to investigate the m5 C methylation of tRNA at both global and single-base levels. Puromycin intake and high-frequency codon reporter assays verified the protein translation level. By combining mRNA and ribosome profiling, a series of downstream proteins and codon usage bias were identified. The acquired data were further validated by tRNA sequencing.

RESULTS

This study observed that the tRNA m5 C methyltransferase NSUN2 was up-regulated in ATC and is associated with dedifferentiation. Furthermore, NSUN2 knockdown repressed ATC formation, proliferation, invasion and migration both in vivo and in vitro. Moreover, NSUN2 repression enhanced the sensitivity of ATC to genotoxic drugs. Mechanically, NSUN2 catalyses tRNA structure-related m5 C modification, stabilising tRNA that maintains homeostasis and rapidly transports amino acids, particularly leucine. This stable tRNA has a substantially increased efficiency necessary to support a pro-cancer translation program including c-Myc, BCL2, RAB31, JUNB and TRAF2. Additionally, the NSUN2-mediated variations in m5C levels and different tRNA Leu iso-decoder families, partially contribute to a codon-dependent translation bias. Surprisingly, targeting NSUN2 disrupted the c-Myc to NSUN2 cycle in ATC.

CONCLUSIONS

This research revealed that a pro-tumour m5C methyltransferase, dynamic tRNA stability regulation and downstream oncogenes, c-Myc, elicits a codon-dependent oncogenic translation network that enhances ATC growth and formation. Furthermore, it provides new opportunities for targeting translation reprogramming in cancer cells.

Loss of CDH16 expression is a strong independent predictor for lymph node metastasis in Middle Eastern papillary thyroid cancer

Papillary Thyroid Cancer (PTC) is the most common type of thyroid cancer. The membrane-associated glycoprotein cadherin-16 (CDH16) plays a significant role in the embryonal development of thyroid follicles and cell adhesion. Previous studies have indicated a substantial downregulation of CDH16 in PTC. However, its role in Middle Eastern PTC has not been elucidated. We analyzed a tissue microarray comprising 1606 PTC and 240 normal thyroid tissues using immunohistochemistry to assess CDH16 expression and determine its clinico-pathological associations. We also conducted BRAF and TERT mutations analyses through Sanger sequencing. Disease-free survival (DFS) was assessed using Kaplan-Meier curves. CDH16 immunostaining was seen in 100% of normal thyroid tissues but only in 9.4% of PTC tissues (p < 0.0001). The loss of CDH16 expression was associated with aggressive PTC characteristics including bilaterality, multifocality, extrathyroidal extension, tall cell variant, lymph node metastasis (LNM) and distant metastasis. Additionally a correlation between loss of CDH16 expression and BRAF and TERT mutations was identified. Intriguingly, upon conducting multivariate logistic regression analysis, CDH16 was determined to be an independent predictor for LNM (Odds ratio = 2.46; 95% confidence interval = 1.60-3.79; p < 0.0001). Furthermore, CDH16 loss was associated with a shorter DFS (p = 0.0015). However, when we further subdivided CDH16 negative patients based on the co-existence of TERT and/or BRAF mutations, we found that patients with both CDH16 negative expression and TERT mutation exhibited the shortest DFS (p < 0.0001). In conclusion, our results suggest that CDH16 protein expression could serve as a valuable diagnostic tool for PTC. Furthermore, these findings demonstrate that the loss of CDH16 expression is an independent predictor of LNM and may contribute to the aggressiveness of PTC. Therefore, downregulation of CDH16 in PTC might be a potential target for designing novel therapeutic strategies to treat PTC.

An overview of the role of telomeres and telomerase in pre‑neoplastic lesions (Review)

Telomeres are tandem repeats of DNA sequences protecting the end of linear chromosomes. Replicative senescence due to telomere attrition is considered a tumor-preventing mechanism in differentiated somatic cells. However, telomere shortening is associated with genome instability and several disease entities. During carcinogenesis, the development of a telomere maintenance mechanism, predominately through the activation of the telomerase enzyme, represents a hallmark of cancer, since it enables cancer cells to avert senescence and divide indefinitely. Although research of the involvement of telomeres and telomerase in various malignant neoplasms has gained a large amount of interest, the timing and relevance of their role in pre-neoplastic lesions remain to be determined. The present narrative review aims to summarize the evidence regarding the role of telomeres and telomerase in pre-neoplasia across different types of tissues.

Multiple Actions of Telomerase Reverse Transcriptase in Cell Death Regulation

Telomerase reverse transcriptase (TERT), a core part of telomerase, has been known for a long time only for its telomere lengthening function by reverse transcription of RNA template. Currently, TERT is considered as an intriguing link between multiple signaling pathways. The diverse intracellular localization of TERT corresponds to a wide range of functional activities. In addition to the canonical function of protecting chromosome ends, TERT by itself or as a part of the telomerase complex participates in cell stress responses, gene regulation and mitochondria functioning. Upregulation of TERT expression and increased telomerase activity in cancer and somatic cells relate to improved survival and persistence of such cells. In this review, we summarize the data for a comprehensive understanding of the role of TERT in cell death regulation, with a focus on the interaction of TERT with signaling pathways involved in cell survival and stress response.

Spotlight on hTERT Complex Regulation in Cutaneous T-Cell Lymphomas

As a major cancer hallmark, there is a sustained interest in understanding the telomerase contribution to carcinogenesis in order to therapeutically target this enzyme. This is particularly relevant in primary cutaneous T-cell lymphomas (CTCL), a malignancy showing telomerase dysregulation with few investigative data available. In CTCL, we examined the mechanisms involved in telomerase transcriptional activation and activity regulation. We analyzed 94 CTCL patients from a Franco-Portuguese cohort, as well as 8 cell lines, in comparison to 101 healthy controls. Our results showed that not only polymorphisms (SNPs) located at the promoter of human telomerase reverse transcriptase (hTERT) gene (rs2735940 and rs2853672) but also an SNP located within the coding region (rs2853676) could influence CTCL occurrence. Furthermore, our results sustained that the post-transcriptional regulation of hTERT contributes to CTCL lymphomagenesis. Indeed, CTCL cells present a different pattern of hTERT spliced transcripts distribution from the controls, mostly marked by an increase in the hTERT β+ variants proportion. This increase seems to be associated with CTCL development and progression. Through hTERT splicing transcriptome modulation with shRNAs, we observed that the decrease in the α-β+ transcript induced a decrease in the cell proliferation and tumorigenic capacities of T-MF cells in vitro. Taken together, our data highlight the major role of post-transcriptional mechanisms regulating telomerase non canonical functions in CTCL and suggest a new potential role for the α-β+ hTERT transcript variant.

Genetic Variants in Telomerase Reverse Transcriptase Contribute to Solar Lentigines

Solar lentigines (SLs) are a hallmark of human skin aging. They result from chronic exposure to sunlight and other environmental stressors. Recent studies also imply genetic factors, but findings are partially conflicting and lack of replication. Through a multi-trait based analysis strategy, we discovered that genetic variants in telomerase reverse transcriptase were significantly associated with non-facial SL in two East Asian (Taizhou longitudinal cohort, n = 2,964 and National Survey of Physical Traits, n = 2,954) and one Caucasian population (SALIA, n = 462), top SNP rs2853672 (P-value for Taizhou longitudinal cohort = 1.32 × 10^‒28 and P-value for National Survey of Physical Traits = 3.66 × 10^‒17 and P-value for SALIA = 0.0007 and P_meta = 4.93 × 10^‒44). The same variants were nominally associated with facial SL but not with other skin aging or skin pigmentation traits. The SL-enhanced allele/haplotype upregulated the transcription of the telomerase reverse transcriptase gene. Of note, well-known telomerase reverse transcriptase‒related aging markers such as leukocyte telomere length and intrinsic epigenetic age acceleration were not associated with SL. Our results indicate a previously unrecognized role of telomerase reverse transcriptase in skin aging‒related lentigines formation.

AST-487 Inhibits RET Kinase Driven TERT Expression in Bladder Cancer

Mutations in the promoter of the human Telomerase Reverse Transcriptase (hTERT) gene are common and associated with its elevated expression in bladder cancer, melanoma, and glioblastoma. Though these mutations and TERT overexpression are associated with aggressive disease and poor outcome, an incomplete understanding of mutant TERT regulation limits treatment options directed at this gene. Herein, we unravel a signaling pathway that leads to upregulated hTERT expression resulting from the −124 bp promoter mutation, the most frequent variant across human cancer. We employed engineered bladder cancer cells that harbor a GFP insertion at the TSS region on −124 hTERT promoter for high-content screening drug discovery using a focused library of ~800 kinase inhibitors. Studies using in vitro and in vivo models prioritized AST-487, an inhibitor of the wild-type, and mutant RET (rearranged during transfection) proto-oncogene as a novel drug inhibitor of both wild-type and mutant promoter-driven hTERT expression. We also identified the RET kinase pathway, targeted by AST-487, as a novel regulator of mutant hTERT promoter-driven transcription in bladder cancer cells. Collectively, our work provides new potential precision medicine approaches for cancer patients with upregulated hTERT expression, perhaps, especially those harboring mutations in both the RET gene and the hTERT promoter, such as in thyroid cancer.

Do Polymorphisms of the TERT, GSTM1, and GSTT1 Genes Increase Laryngeal Cancer Susceptibility in Smokers of Romanian Descent?

Background and Objectives: The aim of this study was to investigate the association between smoking status and single-nucleotide polymorphism in candidate genes that had a known association with smoking-related tumors in previous studies and to explore their link to laryngeal cancer risk in a population of northern Romanian descent. The genes selected have key functions in xenobiotic metabolism (GSTs: the glutathione S-transferases family: GSTM1 and GSTT1) and chromosomal management (TERT). Materials and Methods: The genotype frequencies of TERT_Rs2736100 and the GST subfamilies (GSTM1 and GSTT1) were determined using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The relationship between the polymorphisms and the risk of laryngeal cancer was analyzed in a retrospective case–control study of 92 laryngeal cancer cases and 101 controls, all of whom were smokers. Results: Subjects presenting the GSTT1-null variant had a two-fold increase in risk (OR = 2.05, 95% CI = 1.07–3.95, p = 0.02). While no individual risk was observed for the TERT_Rs2736100 polymorphism, stratification based on gender revealed a nine-fold increase in risk for carriers of the “C” allele in the heterozygote variant who were male (OR = 9, 65% CI = 3.51–26.51, p = 0.0000). Conclusions: The results showed that the GSTT1-null genotype and the mutant heterozygote variant of TERT_Rs2736100 genes may play a significant role in laryngeal cancer susceptibility in subjects of northern Romanian descent. There may be no association between the susceptibility to laryngeal carcinoma and the GSTM1 polymorphism. The results could not confirm the carcinogenic influence smoking has on laryngeal cancer development for the studied polymorphisms.

Thyroid Carcinoma with NSD3::NUTM1 Fusion: a Case with Thyrocyte Differentiation and Colloid Production

In this report, we present a high-grade thyroid carcinoma with an NSD3::NUTM1 fusion detected on expanded next-generation sequencing testing. Nuclear protein of the testis (NUT) carcinomas comprise high-grade, aggressive tumors characterized by rearrangements of the NUTM1 gene with various partner genes, most commonly the bromodomain protein genes BRD4 and BRD3. Approximately 10% of NUT carcinomas contain an NSD3::NUTM1 fusion. NUT carcinomas manifest as poorly differentiated or undifferentiated squamous carcinomas, and 33% show areas of mature squamous differentiation. Only exceptionally have NUT carcinomas shown histology discordant from poorly differentiated/undifferentiated squamous carcinoma, and a thyroid NUT carcinoma with histologic thyrocyte differentiation has not been described to date. Our patient's tumor exhibited mixed cytologic features suggestive of squamoid cells or papillary thyroid carcinoma cells. Overt squamous differentiation was absent, and the tumor produced colloid in poorly formed follicles. Immunophenotypically, the carcinoma was consistent with thyrocyte differentiation with expression of monoclonal PAX8, TTF1, and thyroglobulin (the last predominantly in extracellular colloid). There was zero to < 2% reactivity for proteins typically diffusely expressed in NUT carcinoma: p40, p63, and cytokeratins 5/6. NUT protein expression was equivocal, but fluorescence in situ hybridization confirmed a NUTM1 rearrangement. This exceptional case suggests that NUTM1 fusions may occur in an unknown number of aggressive thyroid carcinomas, possibly with distinctive histologic features but with thyrocyte differentiation. Recognition of this entity potentially has significant prognostic implications. Moreover, thyroid carcinomas with NUTM1 fusions may be amenable to treatment with NUT carcinoma-targeted therapy such as a bromodomain and extraterminal domain protein small molecular inhibitor (BETi).

Emerging mechanisms of telomerase reactivation in cancer

Mutations in the promoter of human telomerase reverse transcriptase (hTERT) result in hyperactivation of hTERT. Notably, all mutations are G>A transitions, frequently found in a wide range of cancer types, and causally associated with cancer progression. Initially, the mutations were understood to reactivate hTERT by generating novel E26 transformation-specific (ETS) binding sites. Recent work reveals the role of DNA secondary structure G-quadruplexes, telomere binding factor(s), and chromatin looping in hTERT regulation. Here, we discuss these emerging findings in relation to the clinically significant promoter mutations to provide a broader understanding of the context-dependent outcomes that result in hTERT activation in normal and pathogenic conditions.

Telomere Targeting Approaches in Cancer: Beyond Length Maintenance

Telomeres are crucial structures that preserve genome stability. Their progressive erosion over numerous DNA duplications determines the senescence of cells and organisms. As telomere length homeostasis is critical for cancer development, nowadays, telomere maintenance mechanisms are established targets in cancer treatment. Besides telomere elongation, telomere dysfunction impinges on intracellular signaling pathways, in particular DNA damage signaling and repair, affecting cancer cell survival and proliferation. This review summarizes and discusses recent findings in anticancer drug development targeting different “telosome” components.

hTERT DNA Methylation Analysis Identifies a Biomarker for Retinoic Acid-Induced hTERT Repression in Breast Cancer Cell Lines

Telomerase reactivation is responsible for telomere preservation in about 90% of cancers, providing cancer cells an indefinite proliferating potential. Telomerase consists of at least two main subunits: a catalytic reverse transcriptase protein (hTERT) and an RNA template subunit. Strategies to inhibit hTERT expression seem promising for cancer treatment. Previous works showed that all-trans retinoic acid (ATRA) induces hTERT repression in acute promyelocytic leukemia cells, resulting in their death. Here, we investigated the effects of ATRA in a subset of breast cancer cell lines. The mutational status of hTERT promoter and the methylation patterns at a single CpG resolution were assessed. We observed an inverse relationship between hTERT expression after ATRA treatment and the methylation level of a specific CpG at chr5: 1,300,438 in a region of hTERT gene at −5 kb of the transcription initiation site. This observation highlighted the significance of this region, whose methylation profile could represent a promising biomarker to predict the sensitivity to ATRA-induced hTERT repression in specific breast cancer subtypes. As hTERT repression promotes drug-induced cell death, checking the methylation status of this unique region and the specific CpG included can help in decision-making to include ATRA in combination therapy and contributes to a better clinical outcome.

TELOMERASE MEDIATEDS PYROPTOSIS BY NF-κB Chicken telomerase reverse transcriptase mediates LMH cell pyroptosis by regulating the nuclear factor-kappa B signaling pathway

The activation of human telomerase reverse transcriptase is regulated by the nuclear factor kappa B (NF-κB) signaling pathway to various degrees to promote the occurrence and development of tumors. However, the regulatory roles of chicken telomerase reverse transcriptase (chTERT) and the NF-κB signaling pathway in chickens are still elusive, particularly in respect to the regulation of cell pyroptosis. In this study, we found that chTERT upregulated the expression of p65 and p50, downregulated the expression of IκBα, promoted the phosphorylation of p65, p50, and IκBα, and significantly increased the transcript levels of the inflammatory cytokines IFNγ, TNFα, and IL-6 in LMH cells. The activity of NF-κB was significantly decreased after siRNA-mediated chTERT silencing. The expression of chTERT and telomerase activity were also significantly decreased when the NF-κB signaling pathway was blocked by p65 siRNA, MG132 or BAY 11-7082. In cells treated with LPS, the activity of NF-κB signaling pathway and the expression of chTERT were significantly upregulated. All of the results suggested that chTERT and the NF-κB pathway could regulate each other, reciprocally. Moreover, the expression of Caspase-1, NLRP3, GSDMA, IL-18, and IL-1β and caused membrane perforation, suggesting the development of pyroptosis by chTERT in LMH cells. And the expression of caspase-11 did not significantly increased in chTERT overexpression group. Genetic silence of NF-κB p65 or chTERT gene by siRNA suppressed the expression of these proinflammatory cytokines, indicating that chTERT mediates pyroptosis by regulating the NF-κB signaling pathway in LMH cells.

The Multifaceted Profile of Thyroid Disease in the Background of DICER1 Germline and Somatic Mutations: Then, Now and Future Perspectives

DICER1 protein is a member of the ribonuclease (RNAse) III family with a key role in the biogenesis of microRNAs (miRNA) and in microRNA processing, potentially affecting gene regulation at the post-transcriptional level. The role of DICER1 and its relevance to thyroid cellular processes and tumorigenesis have only recently been explored, following the acknowledgement that DICER1 germline and somatic changes can contribute not only to non-toxic multinodule goiter (MNG) lesions detected in individuals of affected families but also to a series of childhood tumours, including thyroid neoplasms, which can be identified from early infancy up until the decade of 40s. In a context of DICER1 germline gene mutation, thyroid lesions have recently been given importance, and they may represent either an index event within a syndromic context or the isolated event that may trigger a deeper and broader genomic analysis screening of individuals and their relatives, thereby preventing the consequences of a late diagnosis of malignancy. Within the syndromic context MNG is typically the most observed lesion. On the other hand, in a DICER1 somatic mutation context, malignant tumours are more common. In this review we describe the role of DICER protein, the genomic events that affect the DICER1 gene and their link to tumorigenesis as well as the frequency and pattern of benign and malignant thyroid lesions and the regulation of DICER1 within the thyroidal environment.

TERT Promoter Mutations Increase Sense and Antisense Transcription from the TERT Promoter

Background: Chief among mechanisms of telomerase reverse transcriptase (TERT) reactivation is the appearance of mutations in the TERT promoter. The two main TERT promoter mutations are C>T transitions located −146C>T and −124C>T upstream from the translational start site. They generate a novel Ets/TCF binding site. Both mutations are mutually exclusive and −124C>T is strikingly overrepresented in most cancers. We investigated whether this mutational bias and mutual exclusion could be due to transcriptional constraints. Methods: We compared sense and antisense transcription of a panel of TERT promoter-luciferase vectors harboring the −124C>T and -146C>T mutations alone or together. lncRNA TAPAS levels were measured by RT-PCR. Results: Both mutations generally increased TERT transcription by 2–4-fold regardless of upstream and downstream regulatory elements. The double mutant increased transcription in an additive fashion, arguing against a direct transcriptional constraint. The −146C>T mutation, alone or in combination with −124C>T, also unleashed antisense transcription. In line with this finding, lncRNA TAPAS was higher in cells with mutated TERT promoter (T98G and U87) than in cells with wild-type promoter, suggesting that lncRNA TAPAS may balance the effect of TERT promoter mutations. Conclusions: −146C>T and −124C>T TERT promoter mutations increase TERT sense and antisense transcription, and the double mutant features higher transcription levels. Increased antisense transcription may contain TERT expression within sustainable levels.

Yes-associated protein 1 as a prognostic biomarker and its correlation with telomerase in various cancers

Objectives

The aims of this study were to investigate the expression of Yes-associated protein 1 (YAP1), its prognostic significance, and the correlation between YAP1 and telomerase in various cancers.

Methods

The Gene Expression Profiling Interactive Analysis database was used to analyze RNA sequencing data and the survival rate of patients with various cancers in The Cancer Genome Atlas (TCGA) database. PrognoScan was used to analyze the prognostic value of YAP1 expression in various cancers. Tumor Immune Estimation Resource was used to determine the correlation between YAP1 expression and telomerase in various cancer types based on TCGA data.

Results

The analysis suggested that YAP1 was differentially expressed between tissues of various cancers and non-tumor tissues. High YAP1 expression was also related to a poor prognosis in adrenocortical carcinoma, bladder urothelial carcinoma, and pancreatic adenocarcinoma. Moreover, YAP1 expression was correlated with the expression of telomerase reverse transcriptase and telomerase RNA component in various cancer types.

Conclusion

These results suggest that YAP1 is a potential biomarker with prognostic significance and relevance for oncogene research in various cancer types. The correlation between the expression of YAP1 and telomere-associated genes will help to understand their cancer-promoting mechanisms and interactions.

Mutual regulation between chicken telomerase reverse transcriptase and the Wnt/β-catenin signalling pathway inhibits apoptosis and promotes the replication of ALV-J in LMH cells

This study aimed to explore the mutual regulation between chicken telomerase reverse transcriptase (chTERT) and the Wnt/β-catenin signalling pathway and its effects on cell growth and avian leukosis virus subgroup J (ALV-J) replication in LMH cells. First, LMH cells stably overexpressing the chTERT gene (LMH-chTERT cells) and corresponding control cells (LMH-NC cells) were successfully constructed with a lentiviral vector expression system. The results showed that chTERT upregulated the expression of β-catenin, Cyclin D1, TCF4 and c-Myc. chTERT expression level and telomerase activity were increased when cells were treated with LiCl. When the cells were treated with ICG001 or IWP-2, the activity of the Wnt/β-catenin signalling pathway was significantly inhibited, and chTERT expression and telomerase activity were also inhibited. However, when the β-catenin gene was knocked down by small interfering RNA (siRNA), the changes in chTERT expression and telomerase activity were consistent with those in cells treated with ICG001 or IWP-2. These results indicated that chTERT and the Wnt/β-catenin signalling pathway can be mutually regulated. Subsequently, we found that chTERT not only shortened the cell cycle to promote proliferation but also inhibited apoptosis by downregulating the expression of Caspase 3, Caspase 9 and BAX; upregulating BCL-2 and BCL-X expression; and promoting autophagy. Moreover, chTERT significantly enhanced the migration ability of LMH cells, upregulated the protein and mRNA expression of ALV-J and increased the virus titre. ALV-J replication promoted chTERT expression and telomerase activity.

[Accelerated telomere erosion in schizophrenia: A literature review]

Schizophrenia is associated with a weighted average of 14.5 years of potential life lost according to a recent meta-analysis. This is partly explained by high rates of suicide and a high prevalence of non-psychiatric comorbidity (cardiovascular diseases, diabetes, cancers…). However, all these causes could not fully explain the loss of life expectancy in people suffering from schizophrenia. Life expectancy has been strongly correlated with telomere length (TL). Telomeres are noncoding structures consisting of DNA TTAGGG tandem repeats and associated proteins located at the end of the chromosomes. Their role is to help preserve genome stability by protecting chromosomal ends from the loss of genetic material. The progressive loss of telomeric material during cell divisions has led researchers to consider telomeres as molecular clocks that measure the number of divisions left until cellular death. The fact that both shorter telomeres and schizophrenia have been associated with a decrease in life expectancy has fueled the interest in the study of TL in schizophrenia. In this article, after a detailed review of the literature on the relationships between telomere length and schizophrenia, we discuss the different pathophysiological mechanisms which might explain this association. Based on this analysis, in the last part of the article we discuss potential research, therapeutic and prevention prospects. To date, the majority of the studies and meta-analyses found a decrease in TL in subjects with schizophrenia compared to control subjects. Conversely, all the studies exploring the TL in subjects suffering from first episode psychosis (FEP) have shown no significant difference from TL in control subjects. This suggests that excessive shortening of telomeres occurs during the course of the disease, thus it seems more probable that schizophrenia (or processes associated with it) affects TL rather than telomere erosion being a cause of the disorder. Several pathophysiological, non-mutually exclusive mechanisms have been proposed to explain the observed data. A first hypothesis to explain the acceleration of the physiological process of telomere erosion in schizophrenia is the activation of inflammation processes and oxidative stress as a consequence of schizophrenia per se. However, it seems more probable that reduced TL may be a result of cumulative exposure to chronic stress related to schizophrenia. Indeed, in healthy individuals a growing body of evidence has linked chronic stress to accelerated shortening of TL. This might explain why telomere erosion is too small to be detected in FEP patients who are younger and have a shorter duration of illness than subjects with schizophrenia. Based on these both explanations, telomere alterations may be considered as a biomarker of illness progression and might be useful for illness staging. Identifying processes associated with TL reduction might improve our understanding of the increased mortality and morbidity in schizophrenia, improve reliability of diagnosis, and hopefully suggest means for prevention and/or treatment. Treatments that prevent exposure and/or vulnerability to stressful life events that ameliorate schizophrenia may also prevent or decelerate telomere erosion. In this perspective, engaging subjects suffering from schizophrenia in a healthy diet and regular activity could be both promising strategies to protect telomere maintenance and improve health span at old age. In addition, the inflammatory process and oxidative stress involved in the physiopathology in at least a subgroup of subjects with schizophrenia could also be responsible for telomere erosion. Thus, an efficient anti-inflammatory therapeutic approach that targets these specific pathways could be of interest in this subgroup to limit telomere erosion. Mindfulness-based stress reduction (MBSR) therapies have been shown to reduce telomere erosion by increasing telomerase activity, although these psychological therapies should be used carefully in psychosis. Finally, advancing our understanding of the relationship between stress, inflammation and TL is of great interest for psychiatric research and for understanding stress effects in this population.

Could We Address the Interplay Between CD133, Wnt/β-Catenin, and TERT Signaling Pathways as a Potential Target for Glioblastoma Therapy?

Glioblastoma multiforme (GBM) is one of the most lethal forms of primary brain tumors. Glioblastoma stem cells (GSCs) play an undeniable role in tumor development by activating multiple signaling pathways such as Wnt/β-catenin and PI3K/AKT/mTOR that facilitate brain tumor formation. CD133, a transmembrane glycoprotein, has been used to classify cancer stem cells (CSCs) in GBM. The therapeutic value of CD133 is a biomarker of the CSC in multiple cancers. It also leads to growth and recurrence of the tumor. More recent findings have confirmed the association of telomerase/TERT with Wnt/β-catenin and the PI3K/AKT/mTOR signaling pathways. Advance studies have shown that crosstalk between CD133, Wnt/β-catenin, and telomerase/TERT can facilitate GBM stemness and lead to therapeutic resistance. Mechanistic insight into signaling mechanisms downstream of surface biomarkers has been revolutionized by facilitating targeting of tumor-specific molecular deregulation. This review also addresses the importance of interplay between CD133, Wnt/β-catenin and TERT signaling pathways in GSCs and outlines the future therapeutic goals for glioblastoma treatment.

Tumor Decelerating and Chemo-Potentiating Action of Methyl Jasmonate on a T Cell Lymphoma In Vivo: Role of Altered Regulation of Metabolism, Cell Survival, Drug Resistance, and Intratumoral Blood Flow

Methyl jasmonate (MJ), a natural oxylipin, possesses a broad spectrum of antineoplastic potential in vitro. However, its tumor growth impeding and chemo-potentiating action has not been adequately investigated in vivo. Using a murine thymus-derived tumor named Dalton’s Lymphoma (DL), in the present study, we examined if intra-tumoral administration of MJ can cause tumor growth impedance. We also explored the associated molecular mechanisms governing cell survival, carbohydrate & lipid metabolism, chemo-potentiation, and angiogenesis. MJ administration to tumor-transplanted mice caused deceleration of tumor growth accompanying prolonged survival of the tumor-bearing mice. MJ-dependent tumor growth retardation was associated with the declined blood supply in tumor milieu, cell cycle arrest, augmented induction of apoptosis and necrosis, deregulated glucose and lipid metabolism, enhanced membrane fragility of tumor cells, and altered cytokine repertoire in the tumor microenvironment. MJ administration modulated molecular network implicating Hsp70, Bcl-2, TERT, p53, Cyt c, BAX, GLUT-1, HK 2, LDH A, PDK-1, HIF-1α, ROS, MCT-1, FASN, ACSS2, SREBP1c, VEGF, cytokine repertoire, and MDR1, involved in the regulation of cell survival, carbohydrate and fatty acid metabolism, pH homeostasis, and drug resistance. Thus, the present study unveils novel molecular mechanisms of the tumor growth decelerating action of MJ. Besides, this preclinical study also establishes the adjunct therapeutic potential of MJ. Hence, the present investigation will help to design novel anti-cancer therapeutic regimens for the treatment of hematological malignancies.

NHP2 downregulation counteracts hTR-mediated activation of the DNA damage response at ALT telomeres

About 10% of cancer cells employ the "alternative lengthening of telomeres" (ALT) pathway instead of re-activating the hTERT subunit of human telomerase. The hTR RNA subunit is also abnormally silenced in some ALT⁺ cells not expressing hTERT, suggesting a possible negative non-canonical impact of hTR on ALT. Indeed, we show that ectopically expressed hTR reduces phosphorylation of ssDNA-binding protein RPA (p-RPA^S33 ) at ALT telomeres by promoting the hnRNPA1- and DNA-PK-dependent depletion of RPA. The resulting defective ATR checkpoint signaling at telomeres impairs recruitment of the homologous recombination protein, RAD51. This induces ALT telomere fragility, increases POLD3-dependent C-circle production, and promotes the recruitment of the DNA damage marker 53BP1. In ALT⁺ cells that naturally retain hTR expression, NHP2 H/ACA ribonucleoprotein levels are downregulated, likely in order to restrain DNA damage response (DDR) activation at telomeres through reduced 53BP1 recruitment. This unexpected role of NHP2 is independent from hTR's non-canonical function in modulating telomeric p-RPA^S33 . Collectively, our study shines new light on the interference between telomerase- and ALT-dependent pathways and unravels a crucial role for hTR and NHP2 in DDR regulation at ALT telomeres.

HIF-1α-Mediated Telomerase Reverse Transcriptase Activation Inducing Autophagy Through Mammalian Target of Rapamycin Promotes Papillary Thyroid Carcinoma Progression During Hypoxia Stress

Background: It is important to properly understand the molecular mechanisms of aggressive tumors among papillary thyroid carcinomas (PTCs) that are often the most indolent. Hypoxia inducible factor-1α (HIF-1α), induced by hypoxia, plays pivotal roles in the development and metastasis of the many tumors, including PTCs. Upregulation of telomerase reverse transcriptase (TERT) activity is found in highly invasive PTCs. Further, previous studies have reported that autophagy serves as a protective mechanism to facilitate PTC cell survival. We, therefore, hypothesized that there was a link between HIF-1α, TERT, and autophagy in promoting PTC progression. Methods: Immunohistochemistry staining was conducted to evaluate the expressions of HIF-1α, TERT, and autophagy marker, LC3-II, in matched PTC tumors and corresponding nontumor tissues. Two PTC cell lines (TPC-1 and BCPAP) were used in subsequent cytological function studies. Cell viability, proliferation, apoptosis, migration, and invasion were assessed during hypoxia, genetic enhancement and inhibition of TERT, and chemical and genetic inhibition of autophagy. The protein expression levels of the corresponding biomarkers were determined by Western blotting, and autophagy flow was detected. We characterized the molecular mechanism of PTC cell progression. Results: The protein expression levels of HIF-1α, TERT, and LC3-II were upregulated in PTCs and were significantly correlated with high tumor-node-metastasis stage. Further, an in vitro study indicated that HIF-1α induced by hypoxia functioned as a transcriptional activator by binding with sequences potentially located in the TERT promoter and was positively correlated with the malignant behavior of PTC cell lines. Overexpression of TERT inhibited the kinase activity of mammalian target of rapamycin (mTOR), resulting in the activation of autophagy. Functionally, TERT-induced autophagy provided a survival advantage to PTC cells during hypoxia stress. Conclusions: We identified a novel molecular mechanism involving the HIF-1α/TERT axis, which promoted PTC progression by inducing autophagy through mTOR during hypoxia stress. These findings may provide a basis for the new treatment of aggressive PTCs.

Association of TERT gene polymorphisms with clinical benign prostatic hyperplasia in a Chinese Han population of the Northwest region

Background

To investigate the association between single nucleotide polymorphisms (rs10078761, rs12696304, rs2853669, rs16847897, rs2736100, rs10069690) of telomerase gene (TERT) and the risk clinical benign prostatic hyperplasia (BPH) in a Chinese Han population of the Northwest region.

Methods

A total of 150 BPH patients and 150 healthy older males from the northwest Chinese Han population were included in this study. The sample size for this unmatched case-control study was estimated by the look-up table method. Meanwhile, the general information and disease data of patients were collected. Age was only collected in healthy control subjects for statistical correction. Genotypes were detected using a multiplex PCR + ligase detection reaction (LDR). Typing results and clinical data were statistically analyzed using multiple linear regression and logistic regression. Pearson correlation was used for Hardy-Weinberg equilibrium.

Results

The included population is in Hardy-Weinberg equilibrium. There was no significant association between SNP and the risk of BPH by correlation analysis. However, 4 haplotypes (TCTGGT, TCTGTC, TGCCTC, and TGTGTC) were identified as risk factors of BPH by haplotype analysis. The SNP rs2853669 is an independent risk factor for smooth muscle type of hyperplasia. Besides, rs2736100, rs10078761, and rs10069690 which are in linkage disequilibrium are associated with the severity of BPH.

Conclusions

Polymorphism of the TERT gene determines the different disease development and pathological manifestations of BPH in the Chinese Han population the Northwest region.

Arms-qPCR Improves Detection Sensitivity of Earlier Diagnosis of Papillary Thyroid Cancers With Worse Prognosis Determined by Coexisting BRAF V600E and Tert Promoter Mutations

OBJECTIVE

The coexistence of BRAF V600E and the telomerase reverse transcriptase (TERT) promoter mutation C228T/C250T is extensively associated with thyroid cancer prognosis. Our study aimed to establish a sensitive method for mutation detection and explore the correlation in detail.

METHODS

The BRAF and TERT promoter mutation status of 250 papillary thyroid cancers was determined using amplification-refractory mutation system quantitative polymerase chain reaction (ARMS-qPCR) and Sanger sequencing to compare the sensitivity of the 2 methods. Associations between the mutation status and clinicopathological features were then analyzed.

RESULTS

ARMS-qPCR was more sensitive than Sanger sequencing (BRAF V600E: 75.2% [188 of 250] vs 52.4% [131 of 250], P < .001; TERT promoter C228T/C250T mutation: 12.0% [30 of 250] vs 3.6% [9 of 250], P = .001; comutation: 9.6% [24 of 250] vs 3.2% [8 of 250], P = .005). Both ARMS-qPCR and Sanger sequencing indicated that patients with coexisting BRAF V600E and TERT promoter mutations had an older diagnosis age, higher recurrence rate, and were associated with a more advanced TNM stage and higher metastasis, age, completeness of resection, invasion, and size score. Moreover, ARMS-qPCR helped identify an earlier group stage, which was younger and had smaller tumors and a lower recurrence rate, compared with the group with coexisting BRAF V600E and TERT promoter mutations identified by Sanger sequencing. The newly identified group had a lower metastasis, age, completeness of resection, invasion, and size score and TNM stage.

CONCLUSION

Patients with coexisting BRAF V600E and TERT promoter mutations had a worse prognosis. ARMS-qPCR, the more sensitive method, can be used to identify patients who have a potentially worse prognosis earlier.

Re-Sensitizing Tumor Cells to Cancer Drugs with Epigenetic Regulators

Cancer drug resistance is a major problem for cancer therapy. While many drugs can be effective in first-line treatments, cancer cells can become resistant due to genetic (mutations and chromosomal aberrations) but also epigenetic changes. Hence, many research studies addressed epigenetic drugs in circumventing resistance to conventional therapeutics in different tumor entities and in increasing the efficiency of immune checkpoint therapies. Furthermore, repositioning of already approved drugs in combination with epigenetic modifiers could potentiate their efficacy and thus could be an attractive strategy for cancer treatment. Summarizing, we recapitulate current data on epigenetic drugs and their targets in modulating sensitivity towards conventional and immune therapies, providing evidence that altering expression profiles by epigenetic modifiers holds great potential to improve the clinical outcome of cancer patients.

Cross-Cancer Genome-Wide Association Study of Endometrial Cancer and Epithelial Ovarian Cancer Identifies Genetic Risk Regions Associated with Risk of Both Cancers

BACKGROUND

Accumulating evidence suggests a relationship between endometrial cancer and ovarian cancer. Independent genome-wide association studies (GWAS) for endometrial cancer and ovarian cancer have identified 16 and 27 risk regions, respectively, four of which overlap between the two cancers. We aimed to identify joint endometrial and ovarian cancer risk loci by performing a meta-analysis of GWAS summary statistics from these two cancers.

METHODS

Using LDScore regression, we explored the genetic correlation between endometrial cancer and ovarian cancer. To identify loci associated with the risk of both cancers, we implemented a pipeline of statistical genetic analyses (i.e., inverse-variance meta-analysis, colocalization, and M-values) and performed analyses stratified by subtype. Candidate target genes were then prioritized using functional genomic data.

RESULTS

Genetic correlation analysis revealed significant genetic correlation between the two cancers (rG = 0.43, P = 2.66 × 10-5). We found seven loci associated with risk for both cancers (P Bonferroni < 2.4 × 10-9). In addition, four novel subgenome-wide regions at 7p22.2, 7q22.1, 9p12, and 11q13.3 were identified (P < 5 × 10-7). Promoter-associated HiChIP chromatin loops from immortalized endometrium and ovarian cell lines and expression quantitative trait loci data highlighted candidate target genes for further investigation.

CONCLUSIONS

Using cross-cancer GWAS meta-analysis, we have identified several joint endometrial and ovarian cancer risk loci and candidate target genes for future functional analysis.

IMPACT

Our research highlights the shared genetic relationship between endometrial cancer and ovarian cancer. Further studies in larger sample sets are required to confirm our findings.

Molecular targets of tyrosine kinase inhibitors in thyroid cancer

Thyroid cancer (TC) is the eighth most frequently diagnosed cancer worldwide with a rising incidence in the past 20 years. Surgery is the primary strategy of therapy for patients with medullary TC (MTC) and differentiated TC (DTC). In DTC patients, radioactive iodine (RAI) is administered after thyroidectomy. Neck ultrasound, basal and thyroid-stimulating hormone-stimulated thyroglobulin are generally performed every three to six months for the first year, with subsequent intervals depending on initial risk assessment, for the detection of possible persistent/recurrent disease during the follow up. Distant metastases are present at the diagnosis in ∼5 % of DTC patients; up to 15 % of patients have recurrences during the follow up, with a survival reduction (70 %-50 %) at 10-year. During tumor progression, the iodide uptake capability of DTC cancer cells can be lost, making them refractory to RAI, with a negative impact on the prognosis. Significant advances have been done recently in our understanding of the molecular pathways implicated in the progression of TCs. Several drugs have been developed, which inhibit signaling kinases or oncogenic kinases (BRAF^V600E, RET/PTC), such as those associated with Platelet-Derived Growth Factor Receptor and Vascular Endothelial Growth Factor Receptor. Tyrosine kinase receptors are involved in cancer cell proliferation, angiogenesis, and lymphangiogenesis. Several tyrosine kinase inhibitors (TKIs) are emerging as new treatments for DTC, MTC and anaplastic TC (ATC), and can induce a clinical response and stabilize the disease. Lenvatinib and sorafenib reached the approval for RAI-refractory DTC, whereas cabozantinib and vandetanib for MTC. These TKIs extend median progression-free survival, but do not increase the overall survival. Severe side effects and drug resistance can develop in TC patients treated with TKIs. Additional studies are needed to identify a potential effective targeted therapy for aggressive TCs, according to their molecular characterization.

Fundamental insights into the interaction between telomerase/TERT and intracellular signaling pathways

Telomerase activity is critical for cancer cells to provide unrestricted proliferation and cellular immortality through maintaining telomeres. Telomerase enzymatic activity is regulatable at the level of DNA, mRNA, post translational modifications, cellular transport and enzyme assembly. More recent studies confirm the interaction of the telomerase with various intracellular signaling pathways including PI3K/AKT/mTOR, NF-κB and Wnt/β-catenin which mainly participating in inflammation, epithelial to mesenchymal transition (EMT) and tumor cell invasion and metastasis. Furthermore, hTERT protein has been detected in non-nuclear sites such as the mitochondria and cytoplasm in cells. Mitochondrial TERT indicates various non-telomere-related functions such as decreasing reactive oxygen species (ROS) generation, boosting the respiration rate, protecting mtDNA by direct binding, interacting with mitochondrial tRNAs and increasing mitochondrial membrane potential which can lead to higher chemoresistance rate in cancer cells during therapies. Understanding the molecular mechanisms of the TERT function and depended interactions in tumor cells can suggest novel therapeutic approaches. Hence, in this review we will explain the telomerase activity regulation in translational and post translational levels besides the established correlations with various cell signaling pathways with possible pathways for therapeutic targeting.

TERT-Regulation and Roles in Cancer Formation

Telomerase reverse transcriptase (TERT) is a catalytic subunit of telomerase. Telomerase complex plays a key role in cancer formation by telomere dependent or independent mechanisms. Telomere maintenance mechanisms include complex TERT changes such as gene amplifications, TERT structural variants, TERT promoter germline and somatic mutations, TERT epigenetic changes, and alternative lengthening of telomere. All of them are cancer specific at tissue histotype and at single cell level. TERT expression is regulated in tumors via multiple genetic and epigenetic alterations which affect telomerase activity. Telomerase activity via TERT expression has an impact on telomere length and can be a useful marker in diagnosis and prognosis of various cancers and a new therapy approach. In this review we want to highlight the main roles of TERT in different mechanisms of cancer development and regulation.

Implications of telomerase reverse transcriptase in tumor metastasis

Metastasis is the main culprit of the great majority of cancerrelated deaths. However, the complicated process of the invasion-metastasis cascade remains the least understood aspect of cancer biology. Telomerase plays a pivotal role in bypassing cellular senescence and sustaining the cancer progression by maintaining telomere homeostasis and genomic integrity. Telomerase reverse transcriptase (TERT) exerts a series of fundamental functions that are independent of its enzymatic cellular activity, including proliferation, inflammation, epithelia-mesenchymal transition (EMT), angiogenesis, DNA repair, and gene expression. Accumulating evidence indicates that TERT may facilitate most steps of the invasion-metastasis cascade. In this review, we summarize important advances that have revealed some of the mechanisms by which TERT facilitates tumor metastasis, providing an update on the non-canonical functions of telomerase beyond telomere maintaining. [BMB Reports 2020; 53(9): 458-465].

TERT Promoter Mutation C228T Increases Risk for Tumor Recurrence and Death in Head and Neck Cancer Patients

Background: Head and neck squamous cell carcinoma (HNSCC) is usually associated to tobacco and alcohol consumption. Increased telomerase activity has been consistently detected in 80–90% of malignant tumors, including HNSCC. Mutations within the promoter region of telomerase reverse transcriptase (TERT) that confer enhanced TERT promoter activity have been reported in two major hotspots, designated C228T and C250T.

Objectives: To evaluate TERT promoter mutations C228T and C250T in HNSCC patients from Brazil and correlate with patients' outcome.

Materials and Methods: Formalin-fixed paraffin-embedded tissues were obtained from 88 HNSCC patients and analyzed for TERT promoter mutations C228T and C250T by pyrosequencing.

Results: The overall prevalence of hotspot TERT mutations in HNSCC samples was of 27.3%, with 6.8% at locus C228T and 20.5% at C250T. The majority (92%) of mutated cases were located in oral cavity, mainly at the tongue. We observed that 94.4% of the patients harboring TERT promoter mutation C250T were alcohol consumers (p = 0.032) and 66.7% of the patients harboring TERT promoter mutation C228T were not alcohol consumers (p = 0.035). The presence of C228T mutation impacted patient outcome, with a significant decrease in disease-free survival (20.0 vs. 63.0%, p =0.017) and in overall survival (16.7 vs. 45.1%, p = 0.017).

Conclusion: This is the first report of a TERT promoter mutations in HNSCC patients from South America. The high prevalence of TERT mutation, as well as its association with poor disease-free survival and overall survival, particular at C228T locus might serve as a prognostic biomarker in HNSCC to help clinicians in the management of treatment.

Telomeres and telomerase in oncogenesis

Telomeres are located at the ends of chromosomes and protect them from degradation. Suppressing the activity of telomerase, a telomere-synthesizing enzyme, and maintaining short telomeres is a protective mechanism against cancer in humans. In most human somatic cells, the expression of telomerase reverse transcriptase (TERT) is repressed and telomerase activity is inhibited. This leads to the progressive shortening of telomeres and inhibition of cell growth in a process called replicative senescence. Most types of primary cancer exhibit telomerase activation, which allows uncontrolled cell proliferation. Previous research indicates that TERT activation also affects cancer development through activities other than the canonical function of mediating telomere elongation. Recent studies have improved the understanding of the structure and function of telomeres and telomerase as well as key mechanisms underlying the activation of TERT and its role in oncogenesis. These advances led to a search for drugs that inhibit telomerase as a target for cancer therapy. The present review article summarizes the organization and function of telomeres, their role in carcinogenesis, and advances in telomerase-targeted therapy.

The Solo Play of TERT Promoter Mutations

The reactivation of telomerase reverse transcriptase (TERT) protein is the principal mechanism of telomere maintenance in cancer cells. Mutations in the TERT promoter (TERTp) are a common mechanism of TERT reactivation in many solid cancers, particularly those originating from slow-replicating tissues. They are associated with increased TERT levels, telomere stabilization, and cell immortalization and proliferation. Much effort has been invested in recent years in characterizing their prevalence in different cancers and their potential as biomarkers for tumor stratification, as well as assessing their molecular mechanism of action, but much remains to be understood. Notably, they appear late in cell transformation and are mutually exclusive with each other as well as with other telomere maintenance mechanisms, indicative of overlapping selective advantages and of a strict regulation of TERT expression levels. In this review, we summarized the latest literature on the role and prevalence of TERTp mutations across different cancer types, highlighting their biased distribution. We then discussed the need to maintain TERT levels at sufficient levels to immortalize cells and promote proliferation while remaining within cell sustainability levels. A better understanding of TERT regulation is crucial when considering its use as a possible target in antitumor strategies.

Genetic alterations of malignant pleural mesothelioma: association with tumor heterogeneity and overall survival

Development of precision medicine for malignant pleural mesothelioma (MPM) requires a deep knowledge of tumor heterogeneity. Histologic and molecular classifications and histo‐molecular gradients have been proposed to describe heterogeneity, but a deeper understanding of gene mutations in the context of MPM heterogeneity is required and the associations between mutations and clinical data need to be refined. We characterized genetic alterations on one of the largest MPM series (266 tumor samples), well annotated with histologic, molecular and clinical data of patients. Targeted next‐generation sequencing was performed focusing on the major MPM mutated genes and the TERT promoter. Molecular heterogeneity was characterized using predictors allowing classification of each tumor into the previously described molecular subtypes and the determination of the proportion of epithelioid‐like and sarcomatoid‐like components (E/S.scores). The mutation frequencies are consistent with literature data, but this study emphasized that TERT promoter, not considered by previous large sequencing studies, was the third locus most affected by mutations in MPM. Mutations in TERT promoter, NF2, and LATS2 were more frequent in nonepithelioid MPM and positively associated with the S.score. BAP1, NF2, TERT promoter, TP53, and SETD2 mutations were enriched in some molecular subtypes. NF2 mutation rate was higher in asbestos unexposed patient. TERT promoter, NF2, and TP53 mutations were associated with a poorer overall survival. Our findings lead to a better characterization of MPM heterogeneity by identifying new significant associations between mutational status and histologic and molecular heterogeneity. Strikingly, we highlight the strong association between new mutations and overall survival.

Association between functional TERT promoter polymorphism rs2853669 and cervical cancer risk in South Indian women

A single nucleotide polymorphism (SNP) rs2853669 (A>G) in the telomerase reverse transcriptase (TERT) promoter has recently been reported in chr5:1,295,349 T>C (T349C), and was shown to be associated with increased cancer risk and poor survival in a specific population. However, at present, the role of this particular SNP with TERT promoter driver mutations and its genetic association with human papilloma virus (HPV) in patients with cervical cancer has not been determined. In the present study, the genetic association of the functional SNP rs2853669 in the presence/absence of TERT promoter hotspot mutations and HPV in patients with cervical cancer of South Indian origin was evaluated. To understand and compare the frequency of the variant allele and its risk association in different cancer types of various populations, the SNP was genotyped in 257 cervical cancer samples and 295 controls, and its associations with TERT promoter hotspot mutations and HPV were analyzed. Furthermore, an extensive search of previously published articles in PubMed, Embase and Web of Science was conducted; a meta-analysis was carried out to elucidate the association of the SNP with different cancer types in global populations. The SNP analysis showed significantly high frequency (41%) of homozygous variant allele rs2853669 (GG) in patients with cervical cancer compared with control samples [Recessive allele model odds ratio (OR)=1.71; 95% CI=1.20-2.43; P=0.003]. No significant interaction was observed between the TERT SNP rs2853669 and HPV status as well as other hotspot TERT promoter (C228T and C250T) mutations determined in our previous study. In addition, the overall meta-analysis revealed a significant association of the SNP rs2853669 with other cancer types in different ethnic populations (OR=1.09; 95% CI=1.03-1.16; P=0.004). The present results suggested that the TERT SNP rs2853669 could play an important role in the risk of cervical cancer in a South Indian population.

Berberine associated photodynamic therapy promotes autophagy and apoptosis via ROS generation in renal carcinoma cells

Renal cell carcinoma (RCC) consists of the most lethal common urological cancer and the clinical practice has shown that resistant RCC to commons therapies is extremely high. Berberine is an isoquinoline alkaloid, presents in different kinds of plants and it has long been used in Chinese medicine. It has several properties, such as antioxidant, anti-inflammatory, anti-diabetic, anti-microbial and anti-cancer. Moreover, berberine has photosensitive characteristics and its association with photodynamic therapy (PDT) is effective against tumor cells. This study aimed to evaluate the effects of berberine associated with PDT in renal carcinoma cell lines. The cellular viability assay showed increased cytotoxicity in concentration and time-dependent manner. Berberine presented efficient internalization in all cell lines analyzed. In addition, after treatment with berberine associated with PDT, it was observed a high phototoxicity effect with less than 20 % of viable cells. In this study we observed that the increase of reactive oxygen species (ROS) levels was accompanied by an increase of autophagy levels and apoptosis by caspase 3 activity, suggesting cell death by both mechanisms. Additionally, three target genes of anti-cancer drugs were differentially expressed in 786-O cells, being that Vascular Endothelial Growth Factor-D (FIGF) and Human Telomerase Reverse Transcriptase (TERT) gene presented low expression and Polo Like Kinase 3 (PLK3) presented overexpression after treatment with berberine associated with PDT. In this study, the proposed treatment triggered metabolites changes related to cell proliferation, tumorigenesis and angiogenesis. Thus, it was possible to suggest that berberine has promising potential as a photosensitizing agent in a photodynamic therapy, because it induced significant anticancer effects on renal carcinoma cells.

Finding prognostic gene pairs for cancer from patient-specific gene networks

BACKGROUND

Molecular characterization of individual cancer patients is important because cancer is a complex and heterogeneous disease with many possible genetic and environmental causes. Many studies have been conducted to identify diagnostic or prognostic gene signatures for cancer from gene expression profiles. However, some gene signatures may fail to serve as diagnostic or prognostic biomarkers and gene signatures may not be found in gene expression profiles.

METHODS

In this study, we developed a general method for constructing patient-specific gene correlation networks and for identifying prognostic gene pairs from the networks. A patient-specific gene correlation network was constructed by comparing a reference gene correlation network from normal samples to a network perturbed by a single patient sample. The main difference of our method from previous ones includes (1) it is focused on finding prognostic gene pairs rather than prognostic genes and (2) it can identify prognostic gene pairs from gene expression profiles even when no significant prognostic genes exist.

RESULTS

Evaluation of our method with extensive data sets of three cancer types (breast invasive carcinoma, colon adenocarcinoma, and lung adenocarcinoma) showed that our approach is general and that gene pairs can serve as more reliable prognostic signatures for cancer than genes.

CONCLUSIONS

Our study revealed that prognosis of individual cancer patients is associated with the existence of prognostic gene pairs in the patient-specific network and the size of a subnetwork of the prognostic gene pairs in the patient-specific network. Although preliminary, our approach will be useful for finding gene pairs to predict survival time of patients and to tailor treatments to individual characteristics. The program for dynamically constructing patient-specific gene networks and for finding prognostic gene pairs is available at http://bclab.inha.ac.kr/pancancer.

Microfluidic Droplet Digital PCR Is a Powerful Tool for Detection of BRAF and TERT Mutations in Papillary Thyroid Carcinomas

We examined the utility of microfluidic digital PCR (dPCR) for detection of BRAF and TERT mutations in thyroid tumors. DNA extracted from 100 thyroid tumors (10 follicular adenomas, 10 follicular cancers, 5 medullary cancers, and 75 papillary thyroid cancer (PTC) were used for detection of BRAF and TERT mutations. Digital PCRs were performed using rare mutation SNP genotyping assays on QuantStudio 3D platform. In PTCs, BRAFV600E was detected by dPCR and Sanger sequencing in 42/75 (56%) and in 37/75 (49%), respectively. BRAFV600E was not detected in other tumors. The ratio of mutant/total BRAF alleles varied from 4.7% to 47.5%. These ratios were higher in classical PTCs (27.1%) as compared to follicular variant PTCs (9.4%) p = 0.001. In PTCs with and without metastases, the ratios of mutant/total BRAF alleles were 27.6% and 18.4%, respectively, (p = 0.03). In metastatic lesions percentages of mutant/total BRAF alleles were similar to those detected in primary tumors. TERTC228T and TERTC250T were found in two and one cases, respectively, and these tumors concomitantly harbored BRAFV600E. These tumors exhibited gross extra-thyroidal extension, metastases to lymph nodes, and pulmonary metastases (one case). Our results showed that dPCR allows quantitative assessment of druggable targets in PTCs and could be helpful in a molecular-based stratification of prognosis in patients with thyroid cancer.

Replication of GWAS identifies RTEL1, CDKN2A/B, and PHLDB1 SNPs as risk factors in Portuguese gliomas patients

Diffuse gliomas are the most common malignant primary brain tumors and remain incurable. A better knowledge of the tumor etiology is required. Specific single nucleotides polymorphisms (SNPs) rs4977756 (CDKN2A/B), rs6010620 (RTEL1), rs498872 (PHLDB1), rs2736100 (TERT), and rs4295627 (CCDC26) have been associated with glioma susceptibility and are potential risk biomarkers. This study aimed to analyze five SNPs associated with glioma susceptibility, in the Portuguese population. SNPs were genotyped using the Sequenom MassARRAY platform in 127 gliomas and 180 controls. Unconditional logistic regression models were used to calculate odds ratio (OR) and 95% confidence intervals. The false-positive report probability was also assessed. The associations between polymorphisms and survival were evaluated using the log-rank test. It was found that the AG and GG genotypes of the rs4977756 (CDKN2A/B) were associated with an increased risk of gliomas (OR 1.85 and OR 2.38) and glioblastomas (OR 2.77 and OR 3.94). The GA genotype of the rs6010620 (RTEL1) was associated with a decreased risk of glioblastomas (OR 0.45). We also observed that the GA genotype of the rs498872 (PHLDB1) was associated with an increased risk of gliomas (OR 2.92) and glioblastomas (OR 2.39). No significant risk associations were found for the rs2736100 (TERT) and rs4295627 (CCDC26). In addition, the genotype AA of the rs498872 (PHLDB1) was associated with poor overall survival of gliomas patients (AA vs. GA, p = 0.037). The rs6010620 (RTEL1), rs4977756 (CDKN2A/B), and rs498872 (PHLDB1) are associated with glioma risk in the Portuguese population and these data may contribute to understanding gliomas etiology.

MicroRNAs and Epigenetics Strategies to Reverse Breast Cancer

Breast cancer is a sporadic disease with genetic and epigenetic components. Genomic instability in breast cancer leads to mutations, copy number variations, and genetic rearrangements, while epigenetic remodeling involves alteration by DNA methylation, histone modification and microRNAs (miRNAs) of gene expression profiles. The accrued scientific findings strongly suggest epigenetic dysregulation in breast cancer pathogenesis though genomic instability is central to breast cancer hallmarks. Being reversible and plastic, epigenetic processes appear more amenable toward therapeutic intervention than the more unidirectional genetic alterations. In this review, we discuss the epigenetic reprogramming associated with breast cancer such as shuffling of DNA methylation, histone acetylation, histone methylation, and miRNAs expression profiles. As part of this, we illustrate how epigenetic instability orchestrates the attainment of cancer hallmarks which stimulate the neoplastic transformation-tumorigenesis-malignancy cascades. As reversibility of epigenetic controls is a promising feature to optimize for devising novel therapeutic approaches, we also focus on the strategies for restoring the epistate that favor improved disease outcome and therapeutic intervention.

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.