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The role of telomerase reverse transcriptase (TERT) induction and telomere maintenance in carcinogenesis including cervical cancer (CC) pathogenesis has been well established. However, it remains unclear whether they affect infection of high-risk human papillomavirus (hrHPV), an initiating event for CC development. Similarly, genetic variants at the TERT locus are shown to be associated with susceptibility to CC, but it is unclear whether these SNPs modify the risk for cervical HPV infection. Here we show that in CC-derived HeLa cells, TERT overexpression inhibits, while its depletion upregulates expression of Syndecan-1 (SDC-1), a key component for HPV entry receptors. The TCGA cohort of CC analyses reveals an inverse correlation between TERT and SDC-1 expression (R = -0.23, P = 0.001). We further recruited 1330 females (520 non-HPV and 810 hrHPV-infected) without CC or high-grade cervical intraepithelial neoplasia to analyze telomeres in cervical epithelial cells and SNPs at rs2736098, rs2736100 and rs2736108, previously identified TERT SNPs for CC risk. Non-infected females exhibited age-related telomere shortening in cervical epithelial cells and their telomeres were significantly longer than those in hrHPV-infected group (1.31 ± 0.62 vs 1.19 ± 0.48, P < 0.001). There were no differences in rs2736098 and rs2736100 genotypes, but non-infected individuals had significantly a higher C-allele frequency (associated with higher TERT expression) while lower T-allele levels at rs2736108 compared with those in the hrHPV group (P = 0.020). Collectively, appropriate telomere maintenance and TERT expression in normal cervical cells may prevent CC by modulating hrHPV infection predisposition, although they are required for CC development and progression., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: The essential hypertension (EH) pathophysiology remains poorly understood. Many studies indicate that reduced leukocyte telomere length (LTL) is involved in the EH pathogenesis, however, the direct analysis of arterial telomere length (ATL) from EH patients and normotensive individuals did not show a difference. To address these discrepant observations between LTL and ATL, we performed comprehensive analyses of LTL, telomerase gene expression and their genetic variants in healthy normotensive controls and EH patients. Methods: Sex-matched 206 EH patients and equal numbers of healthy controls were recruited. LTL, and the expression of two key telomerase components, telomerase reverse transcriptase (TERT) and internal RNA template (TERC) were determined using qPCR. Genetic variants of rs2736100 at the TERT and rs12696304 at the TERC loci were determined using TaqMan genotyping kits. Results: LTL was significantly shorter in EH patients than in their normotensive controls (0.96 ± 0.52 vs 1.19 ± 0.58, P = 0.001). Moreover, TERT and TERC expression in patients' leukocytes were substantially lower compare to that in healthy controls (TERT, 0.98 ± 0.98 vs 1.76 ± 1.75, P = 0.003; TERC, 1.26 ± 1.62 vs 4.69 ± 3.61, P < 0.001). However, there were no differences in the genetic variants of rs2736100 and rs12696304 between patient and control groups. Conclusions: EH patients have significantly shorter LTL, which may result from defective TERT and TERC expression in leukocytes. Collectively, lower telomerase expression contributes to shorter LTL observed in EH patients, and telomerase activators may be considered for EH therapy., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Telomeres are structurally nucleoprotein complexes at termini of linear chromosomes and essential to chromosome stability/integrity. In normal human cells, telomere length erodes progressively with each round of cell divisions, which serves as an important barrier to uncontrolled proliferation and malignant transformation. In sharp contrast, telomere maintenance is a key feature of human malignant cells and required for their infinite proliferation and maintenance of other cancer hallmarks as well. Thus, a telomere-based anti-cancer strategy has long been suggested. However, clinically efficient and specific drugs targeting cancer telomere-maintenance have still been in their infancy thus far. To achieve this goal, it is highly necessary to elucidate how exactly cancer cells maintain functional telomeres. In the last two decades, numerous studies have provided profound mechanistic insights, and the identified mechanisms include the aberrant activation of telomerase or the alternative lengthening of telomere pathway responsible for telomere elongation, dysregulation and mutation of telomereassociated factors, and other telomere homeostasis-related signaling nodes. In the present review, these various strategies employed by malignant cells to regulate their telomere length, structure and function have been summarized, and potential implications of these findings in the rational development of telomere- based cancer therapy and other clinical applications for precision oncology have been discussed., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Telomere length (TL) is considered an indicator of aging and age-related diseases, but longitudinal studies on TL changes and mortality are few. We therefore analyzed TL and longitudinal changes in TL in relation to all-cause, cardiovascular, and cancer mortality in 247 elderly Swedish men. TL was determined by the qPCR method at ages 71 and 81 and subsequent mortality cases were identified from the Swedish cause-of-death registry. Cox proportional hazard ratios were calculated during a mean follow-up of 7.4 years, during which 178 deaths occurred. Short telomeres at baseline was strongly associated with mortality risks, with a 40 to 70% increased risk of all-cause mortality, and a 2-fold increased risk of cancer mortality. Longitudinal changes in TL revealed shortening in 83% of individuals, whilst 10% extended their telomeres. TL attrition did not predict all-cause or cancer mortality, but we found a 60% decreased risk for cardiovascular mortality in those who shortened their telomeres. Our data show an increased risk of mortality in individuals with short baseline telomeres, but no relations to all-cause, and cancer mortality for changes in TL. Intriguingly, our data indicate lower risk of cardiovascular mortality with shortening of telomeres. The latter should be interpreted cautiously.

DNA methyltransferase inhibitors (DNMTIs) such as 5-azacytidine (5-AZA) have been used for treatment of acute myeloid leukemia (AML) and other malignancies. Although inhibiting global/gene-specific DNA methylation is widely accepted as a key mechanism behind DNMTI anti-tumor activity, other mechanisms are likely involved in DNMTI's action. Because telomerase reverse transcriptase (TERT) plays key roles in cancer through telomere elongation and telomere lengthening-independent activities, and TERT has been shown to confer chemo- or radio-resistance to cancer cells, we determine whether DNMTIs affect telomere function and whether TERT/telomerase interferes with their anti-cancer efficacy. We showed that 5-AZA induced DNA damage and telomere dysfunction in AML cell lines by demonstrating the presence of 53-BP1 foci and the co-localization of 53-BP1 foci with telomere signals, respectively. Telomere dysfunction was coupled with diminished TERT expression, shorter telomere and apoptosis in 5-AZA-treated cells. However, 5-AZA treatment did not lead to changes in the methylation status of subtelomere regions. Down-regulation of TERT expression similarly occurred in primary leukemic cells derived from AML patients exposed to 5-AZA. TERT over-expression significantly attenuated 5-AZA-mediated DNA damage, telomere dysfunction and apoptosis of AML cells. Collectively, 5-AZA mediates the down-regulation of TERT expression, and induces telomere dysfunction, which consequently exerts an anti-tumor activity.

The serotonin transporter gene (5-HTT)-linked polymorphic region (5-HTTLPR) plays an important role in modulating mood and behavior by regulating 5-HTT expression and thereby controlling the concentration of serotonin (5-HT) in brain synapses: The homozygous shorter allele (S/S) in 5-HTTLPR results in lower 5-HTT expression coupled with stronger psycho-pathological reactions to stressful experiences compared to the homozygous long (L/L) and heterozygous (S/L) alleles. Psychological insults and mood disorders have been shown to cause accelerated telomere shortening, a marker of biological aging, however, it is currently unclear whether the allelic variants of 5-HTTLPR affect telomere length (TL) in the healthy population without mood disorders. In the present study, we determined the relationship between TL and the 5-HTTLPR variants in healthy Han Chinese. The 5-HTTLPR genotyping and leukocyte TL analysis of 280 young female Han Chinese freshmen showed a significantly shorter TL in 149 of them carrying the 5-HTTLPR S/S version compared to those (131) with the L/S or L/S plus L/L genotypes (mean ± SD, 0.533±0.241 for S/S vs 0.607±0.312 for L/S, P  =  0.034; or vs 0.604±0.313 for L/S plus L/L, P  =  0.038). Similar results were achieved in the other cohort including 220 adult healthy individuals of different age, gender and profession (0.691±0.168 for S/S vs 0.729±0.211 for L/S, P  =  0.046, or vs 0.725±0.213 for L/S plus L/L, P  =  0.039). Taken together, shorter leukocyte TL is significantly associated with the 5-HTTLPR S/S allelic variant, which may be implicated in psychological stress-related health problems.

Telomeres play an important role in the maintenance of genomic stability/integrity and are synthesized by the RNA-dependent polymerase telomerase. Progressive telomere shortening contributes to both in vitro and in vivo aging, and telomere length dynamics and telomerase expression profile in human tissues during extrauterine life have been well characterized. However, little is known about these changes in the early stage of gestation. In the present study, we determined telomere length and the expression of telomerase core units (telomerase reverse transcriptase, hTERT, and telomerase RNA component, hTERC) in human fetus tissues from 6 to 11 weeks of gestational age. A sharp decline in telomere length occurred between 6 and 7 weeks of gestational age, and a relatively stable or slightly shortened telomere length was thereafter maintained until birth. The inverse correlation between TERT or TERC expression and gestational age was steadily observed in these fetus tissues. Taken together, there is a rapid reduction followed by a slow erosion of telomere length in human fetus from gestational age 6-11 weeks, while hTERT and hTERC expression decreases steadily during this period. The present findings not only contribute to better understandings of telomere/telomerase biology in human embryonic development, but also are implicated in telomere/telomerase-related diseases or problems., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The number of long-term survivors of patients with various malignancies (>5 years) is increasing mainly owing to advances in cancer therapeutics, but long-term side effects of the cancer treatment in this population have emerged as an important health and socio-economical issue. Telomeres and telomerase are known to be essential for regulation of cellular life-span and maintenance of genomic stability, and earlier studies have demonstrated that cancer patients who receive chemotherapy have shorter telomeres in their blood cells, indicating accelerated telomere erosion and a potential contribution of telomere loss to late side-effects. Little is currently known about the effect of chemotherapeutic agents and radiation on telomere dynamics including potential effects on telomere length, structure, function, telomerase activity, and telomere shelterin proteins in normal human cells. In the present study, we had addressed this issue experimentally. The treatment of normal human T lymphocytes and fibroblasts with chemotherapeutic agents doxorubicin (DOX) or etoposide (VP16) led to significant shortening of telomeres, down-regulation of telomerase activity, and diminished expression of telomerase reverse transcriptase (hTERT) and the telomere binding proteins TPP1 and POT1. More importantly, telomere dysfunction was observed in cells treated with DOX or VP16. Furthermore, all the above alterations were similarly found in the cells receiving γ-irradiation. Taken together, both chemotherapy and radiotherapy significantly impair telomere maintenance and function in normal human cells. Conceivably telomere dysfunction causes shortened life-span and genomic instability of normal human cells, and thereby contributes to tissue/organ damage and secondary malignancies in long-term survivors of cancer., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: The mechanism by which human cytomegalovirus (HCMV) stimulates oncogenesis is unclear. Because cellular immortalization and transformation require telomerase activation by expression of the telomerase reverse transcriptase (hTERT) gene, we examined the role of HCMV in telomerase activation., Methods: Normal human diploid fibroblasts (HDFs) and human malignant glioma (MG) cell lines were infected with HCMV or transfected with expression vectors encoding HCMV immediate early (IE) antigen 72 or 86. hTERT expression and promoter activity and telomerase activity were evaluated using reverse transcription-polymerase chain reaction, a luciferase reporter assay, and a telomeric repeat amplification protocol, respectively. hTERT promoter occupancy by the transcription factor Sp1, IE antigens, and histone deacetylases (HDACs) was assessed by chromatin immunoprecipitation. hTERT and IE protein expression in human primary glioblastoma multiforme (GBM) was determined immunohistochemically. All statistical tests were two-sided., Results: In telomerase and hTERT-negative HDFs, HCMV infection induced constitutive hTERT expression and telomerase activation. The hTERT promoter activity in HDFs and MG cell lines was statistically significantly enhanced by HCMV in a dose-dependent manner (mean luciferase activity [arbitrary units] in control HDFs and in HDFs infected with HCMV at multiplicities of infection [MOIs] of 0.1 = 6 and 521, respectively, difference = 515, 95% CI = 178 to 850; mean activity at MOI of 1 and 10 = 8828 and 59,923, respectively; P < .001 comparing control with HCMV-infected cells at all MOIs). Ectopic expression of HCMV IE-72 protein also stimulated hTERT promoter activity in HDFs. HCMV-mediated transactivation of the hTERT gene was dependent on the presence of Sp1-binding sites in the hTERT promoter and was accompanied by increases in Sp1 binding, acetylation of histone H3, and a reduction in HDAC binding at the core promoter. In specimens of GBM, HCMV IE and hTERT proteins were colocalized in malignant cells and their levels paralleled each other., Conclusions: HCMV activates telomerase in both HDFs and malignant cells. These findings begin to reveal a novel mechanism by which HCMV infection may be linked to or modulate oncogenesis through telomerase activation.

Although human papillomavirus (HPV) has been defined as the pathogen for cervical carcinomas, molecular events underlying the oncogenic process are unclear. As telomere dysfunction-mediated chromosomal instability and telomerase activation have been suggested as key events in carcinogenesis, we dissected the dynamic changes in telomere length, checkpoint response, and temporal profile of telomerase expression during the evolution from precursor lesions (cervical intraepithelial neoplasia, CINs) to invasive cancers of the uterine cervix in sequential samples from 16 patients. Telomeres were significantly shortened in all CIN samples and no further substantial attritions occurred in most cases with the acquisition of malignant phenotype. Very short telomeres were coupled with constitutive activation of the DNA damage response pathway (Chk2 phosphorylation) and increased cellular proliferation in those cervical specimens. Telomerase reverse transcriptase (hTERT) expression was preferably induced at advanced CINs or invasive cancers. The present finding demonstrates that excessive telomere shortening predominantly occurs in the early carcinogenesis of the uterine cervix largely prior to telomerase activation. Widespread over-erosion of telomeres or telomere dysfunction in very early stages of cervical tumorigenesis might fuel transformation processes by driving chromosomal instability.

Cri du chat syndrome (CdCS) results from loss of the distal portion of chromosome 5p, where the telomerase reverse transcriptase (hTERT) gene is localized (5p15.33). hTERT is the rate-limiting component for telomerase activity that is essential for telomere-length maintenance and sustained cell proliferation. Here, we show that a concomitant deletion of the hTERT allele occurs in all 10 patients with CdCS whom we examined. Induction of hTERT mRNA in proliferating lymphocytes derived from five of seven patients was lower than that in unaffected control individuals (P<.05). The patient lymphocytes exhibited shorter telomeres than age-matched unaffected individuals (P<.0001). A reduction in replicative life span and a high rate of chromosome fusions were observed in cultured patient fibroblasts. Reconstitution of telomerase activity by ectopic expression of hTERT extended the telomere length, increased the population doublings, and prevented the end-to-end fusion of chromosomes. We conclude that hTERT is limiting and haploinsufficient for telomere maintenance in humans in vivo. Accordingly, the hTERT deletion may be one genetic element contributing to the phenotypic changes in CdCS.

Telomere maintenance is a critical requirement for enabling replicative immortality and tumour development. Here, telomerase expression and activity, telomere length (TL) and potential regulatory factors that can underlie telomerase machinery alterations in small intestinal neuroendocrine tumours (SI-NETs) were analyzed. Telomerase activity assessed by TRAP assay was increased in SI-NETs compared to normal ileum (P < 0.001). The telomerase reverse transcriptase gene (TERT) was over-expressed in SI-NETs vs. normal ileal samples (P = 0.01). Furthermore, relative TL assessed by qPCR was found shorter in tumours compared with normal ileum (P = 0.02) and in distant metastasis samples compared to primary tumours and local metastases (P= 0.02). TERT promoter hotspot mutations were not present and TERT copy number gain was only observed in 3/70 tumour samples. TERT or chromosome 18 copy number alterations were not associated with telomerase expression and activity or TL. However, hypermethylation of TERT promoter in Region B – in the proximity of the transcription start site – was inversely correlated with TERT expression and telomerase activity and positively correlated with TL. Global LINE1 methylation was positively correlated with TERT promoter Region B methylation and was inversely correlated with telomerase activity, TERT expression and the upstream Region A methylation. The results show that telomerase activation, TERT expression and shorter telomeres are commonly found in SI-NETs. Aberrant DNA methylation of TERT promoter and of LINE1 can be implicated in abnormal regulation of TERT in SI-NETs. [ABSTRACT FROM AUTHOR]

DNA helicases are essential to genomic stability by regulating DNA metabolisms and their loss-of-function mutations lead to genomic instability and predisposition to cancer. Paradoxically, overexpression of DNA helicases is observed in several cancers. Here we analyzed genomic and molecular alterations in 12 important DNA helicases in TCGA pan-cancers to provide an overview of their aberrations. Significant expression heterogeneity of 12 DNA helicases was observed. We calculated DNA helicase score (DHS) based on their expression, and categorized tumors into high, low and intermediate subtypes. High DHS subtypes were robustly associated with stemness, proliferation, hyperactivated oncogenic signaling, longer telomeres, total mutation burden, copy number alterations (CNAs) and shorter survival. Importantly, tumors with high DHSs exhibited stronger expression of alternative end-join (alt-EJ) factors, indicative of sensitivity to chemo- and radio-therapies. High DHSs were also associated with homologous recombination deficiency (HRD), BRCA1/2 mutations and sensitivity to PARP inhibitors. Moreover, several drugs are identified to inhibit DNA helicases, with the Auror A kinase inhibitor Danusertib as the strongest candidate that was confirmed experimentally. The aberrant expression of DNA helicases was associated with CNAs, DNA methylation and m6A regulators. Our findings thus reveal widespread dysregulation of DNA helicases and their broad connection with featured oncogenic aberrations across human cancers. The close association of DHS with the alt-EJ pathway and HRD, and identification of Danusertib as a putative DNA helicase inhibitor have translational significance. Taken together, these findings will contribute to DNA helicase-based cancer therapy. • Dysregulation of DNA helicases is widespread across human cancer. • Higher DNA helicase scores are associated with proliferation, stemness and genomic alterations. • Higher DNA helicase scores are correlated Alt-EJ pathway, indicative of sensitivity to chemo-/radio-therapies. • Auror A kinase inhibitor Danusertib is identified as a putative DNA helicase inhibitor. [ABSTRACT FROM AUTHOR]

Adrenocortical carcinoma (ACC) is one of the deadliest endocrine malignancies and telomere maintenance by activated telomerase is critically required for ACC development and progression. Because telomerase reverse transcriptase (TERT) and regulator of telomere elongation helicase 1 (RTEL1) play key roles in telomere homeostasis, we determined their effect on ACC pathogenesis and outcomes. Analyses of TCGA and GEO datasets showed significantly higher expression of RTEL1 but not TERT in ACC tumors, compared to their benign or normal counterparts. Furthermore, gains/amplifications of both TERT and RTEL1 genes were widespread in ACC tumors and their expression correlated with their gene copy numbers. Higher expression of either TERT or RTEL1 was associated with shorter overall and progression-free survival (OS and PFS) in the TCGA ACC patient cohort, and higher levels of both TERT and RTEL1 mRNA predicted the shortest patient OS and PFS. However, multivariate analyses showed that only RTEL1 independently predicted patient OS and PFS. Gene set enrichment analysis further showed enrichments of wnt/β-catenin, MYC, glycolysis, MTOR, and DNA repair signaling pathways in ACC tumors expressing high TERT and RTEL1 mRNA levels. Taken together, TERT and RTEL1 promote ACC aggressiveness synergistically and may serve as prognostic factors and therapeutic targets for ACC. • Dysregulation of TERT and RTEL1 is widespread in ACC. • Higher expression of both TERT and RTEL1 is associated with important oncogenic pathways and metabolic reprograming in ACC. • TERT and RTEL1 are prognostic factors and therapeutic targets for ACC. [ABSTRACT FROM AUTHOR]

Abstract: Prevention of graft rejection in renal transplant recipients depends on chronic treatment with immunosuppressive agents. However, impaired immune functions and immunosurveillance may cause infection, cancer and many other problems, which subsequently compromise quality of life and survival of patients. In the present study, we assessed potential premature immune-senescence in long-term survivors of kidney transplant patients receiving immunosuppressive agents. Peripheral blood lymphocytes derived from patients had significantly shorter telomeres than those from age- and sex-matched healthy individuals. Consistent with this, lower expression of telomerase reverse transcriptase (hTERT) and telomerase activity was observed in patients’ lymphocytes. The level of p16ink4A expression was elevated in patients’ cells. Moreover, the CD8+/CD28− fraction of late-stage differentiated T cells was significantly increased in the patients. In vitro studies further showed that cyclosporine A, a widely used immunosuppressive drug in transplant patients, attenuated induction of hTERT and telomerase activation in T cells treated with the mitogenic agent concanavalin A. Taken together, immunosuppressant-mediated premature senescence of T lymphocytes occurs in renal transplant recipients. [Copyright &y& Elsevier]