Genomic, epigenomic, and transcriptomic signatures for telomerase complex components: a pan-cancer analysis.

Telomerase activation is required for malignant transformation. Recent advances in high-throughput technologies have enabled the generation of complex datasets, thus providing alternative approaches to exploring telomerase biology more comprehensively, which has proven to be challenging due to the need for laborious assays required to test for telomerase activity. To solve these issues, several groups have analyzed TCGA pan-cancer tumor datasets by investigating telomerase reverse transcriptase (TERT), the catalytic subunit for telomerase activity, or its surrogates. However, telomerase is a multiunit complex containing not only TERT, but also numerus cofactors required for telomerase function. Here we determined genomic and molecular alterations of 10 well-characterized telomerase components in the TCGA and CCLE datasets. We calculated a telomerase score (TS) based on their expression profiles and clustered tumors into low, high, and intermediate subtypes. To validate the in silico analysis result, we used immunoblotting and telomerase assays. High TS subtypes were significantly associated with stemness, proliferation, epithelial to mesenchymal transition, hyperactivation of oncogenic signaling pathways, shorter patient survival, and infiltration of dysfunctional T-cells or poor response to immunotherapy. Copy number alterations in 10 telomerase components were widespread and associated with the level of their expression. Surprisingly, primary tumors and cancer cell lines frequently displayed a homozygous deletion of the TCAB1 gene, encoding a telomerase protein essential for telomerase trafficking, assembling, and function, as previously reported. However, tumors or cells carrying a TCAB1 deletion still exhibited telomerase activity comparable to or even higher than their wildtype counterparts. Collectively, applying telomerase component-based TS in complex datasets provided a robust tool for telomerase analyses. Our findings also reveal a tight connection between telomerase and other oncogenic signaling pathways; TCAB1 may acts as a dispensable telomerase component. Moreover, TS may serve as a useful biomarker to predict patient outcomes and response to immunotherapy.

The association of telomere maintenance and TERT expression with susceptibility to human papillomavirus infection in cervical epithelium.

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.

Regulatory region mutations of TERT, PLEKHS1 and GPR126 genes as urinary biomarkers in upper tract urothelial carcinomas.

Background: The hotspot regulatory region mutations of the TERT, PLEKHS1 and GPR126 genes have been shown to occur frequently in urothelial bladder carcinoma (UBC). However, it is currently unclear whether these mutations are all present in upper tract urothelial carcinomas (UTUC) including renal pelvic carcinoma (RPC) and ureter carcinoma (UC), although TERT promoter mutations were previously observed in these malignancies. Methods: The hotspot mutations of TERT and PLEKHS1 promoters and GPR126 intron 6 (enhancer) in tumors derived from 164 patients with UTUC were determined using Sanger sequencing, and the obtained results were further compared with the mutation frequency in 106 UBCs. The mutations were also assessed in urine from patients with UTUC and UBC. Results: The mutation frequencies in UTUC tumors were 28%, 5.8% and 11% for TERT and PLEKHS1 promoters and GPR126 intron 6, respectively, which were lower than those (44.3%, 26.4%, and 31.4%, respectively) in UBCs. The total frequencies for the presence of any of these mutations were 50.8% and 34.4% for RPCs and UCs, respectively. All these mutated DNA sequences were detectable in urine from both UTUC and UBC patients and disappeared rapidly in most patients after surgery. Conclusions: This proof-of-concept study demonstrates that the hotspot mutations in the TERT, PLEKHS1 and GPR126 non-coding regions are present in UTUCs, and that urinary assays of these mutated sequences serve as potential biomarkers for UTUC diagnostics and disease monitoring.

Shorter Leukocyte Telomere Length coupled with lower expression of Telomerase Genes in patients with Essential Hypertension.

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.

Patients with benign prostatic hyperplasia show shorter leukocyte telomere length but no association with telomerase gene polymorphisms in Han Chinese males.

OBJECTIVE: Benign prostatic hyperplasia (BPH) is an age-related disease, occurring in >70% of men of age >60. Because telomeres and telomerase play a key role in aging and age-related diseases, and certain telomerase gene single nucleotide polymorphisms (SNPs) are shown to be associated with the susceptibility to age-related diseases, we wanted to determine the relationship between BPH and leukocyte telomere length (LTL) and telomere length-related single nucleotide polymorphisms (SNPs) of the telomerase holoenzyme genes. METHODS: Peripheral blood was collected from both BPH patients and age-matched healthy male controls and genomic DNA was extracted. rs2736100 and rs2736098 at the TERT and rs12696304 at the TERC locus were analysed using pre-designed TaqMan SNP genotyping assay kits. LTL was determined using qPCR. RESULTS: Patients with BPH had significantly shorter LTL (1.231 ± 0.532 vs 0.899 ± 0.322, P < 0.001). The genotyping results show similar frequencies in rs2736100, rs2736098 and rs12696304 between healthy and BPH individuals. CONCLUSIONS: Shorter telomeres but not telomerase SNPs at the TERT and TERC loci, are associated with BPH. Short telomeres may promote senescence of a fraction of prostatic epithelial cells, while senescent cells in turn facilitate epithelial and stromal cell proliferation by the senescence-associated secretory phenotype mechanism, thereby eventually leading to BPH development.

TERT promoter mutations and GABP transcription factors in carcinogenesis: More foes than friends.

The transcriptional de-repression of the telomerase reverse transcriptase (TERT) gene and subsequent activation of telomerase is a prerequisite step in malignant transformation and progression. Recently, the gain-of-function mutation of the TERT promoter was identified in many types of human malignancies, and the mutated promoter acquires de novo ETS binding motifs through which the TERT transcription is activated. The ETS family transcription factors GABPA and GABPB1 have been shown to act as master drivers for the mutant TERT promoter activity. Indeed, GABPA or GABPB1 depletion leads to the down-regulation of TERT expression in the mutant TERT promoter-bearing cancer cells, and is thus proposed as targets for cancer therapy. Surprisingly, however, despite its key role in activating the mutant TERT promoter and telomerase, GABPA may itself function as a potent tumor suppressor in several malignancies. In this review, we address the collaboration between GABPA and mutant TERT promoter in cancer development, discuss selection trade-offs among different activities of GABPA in cancer evolution, and underscore the suppressive function of GABPA in cancer progression and implications in precision oncology.

The telomerase gene polymorphisms, but not telomere length, increase susceptibility to primary glomerulonephritis/end stage renal diseases in females.

BACKGROUND: Primary glomerulonephritis (GN) is the leading cause of chronic kidney disease (CKD) and frequently progresses into end stage renal diseases (ESRDs). Shorter leukocyte telomere length (LTL) has been implicated in the CKD susceptibility and diminished kidney function, however, it is unclear whether the variants in telomerase genes contribute to risk to GN/CKD/ESRD. Here we address this issue by determining their association with the genetic variants of rs12696304 at the telomerase RNA component (TERC) and rs2736100 at the telomerase reverse transcriptase (TERT) loci. METHODS: The study includes 769 patients (243 primary GN-derived CKD and 526 ESRD cases) and sex-/age-matched healthy controls. Genomic DNA was extracted from peripheral blood of both controls and patients. Genotyping of rs12696304 and rs2736100 variants was carried out using PCR-based assays. Leukocyte telomere length (LTL) was determined using quantitative PCR (qPCR). RESULTS: A significantly higher frequency of TERC rs12696304 G allele was observed in patients and associated with increased disease risk (C vs G: OR = 1.334, 95% CI 1.112-1.586, P = 0.001; CC + GC vs GG: OR = 1.334, 95% CI 1.122-1.586, P = 0.001). Further analyses showed that such significant differences were only present between female controls and patients (C vs G: OR = 1.483, 95% CI 1.140-1.929, P = 0.003; CC + GC vs CC: OR = 1.692, 95% CI 1.202-2.383, P = 0.003), but not males. There were no differences in rs2736100 variants between controls and patients, but female ESRD patients carried significantly higher C allele frequencies than did female controls (A vs C: OR = 1.306, 95% CI 1.005-1.698, P = 0.046; AA vs CC: OR = 1.781, 95% CI 1.033-3.070, P = 0.037). There was no difference in LTL between controls and patients. CONCLUSIONS: Our results reveal that the TERC rs12696304 and TERT rs2736100 polymorphisms, but not LTL per se, contribute to GN/CDK/ESRD risk.

Telomere-related Markers for Cancer.

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.

GABPA is a master regulator of luminal identity and restrains aggressive diseases in bladder cancer.

TERT promoter mutations occur in the majority of glioblastoma, bladder cancer (BC), and other malignancies while the ETS family transcription factors GABPA and its partner GABPB1 activate the mutant TERT promoter and telomerase in these tumors. GABPA depletion or the disruption of the GABPA/GABPB1 complex by knocking down GABPB1 was shown to inhibit telomerase, thereby eliminating the tumorigenic potential of glioblastoma cells. GABPA/B1 is thus suggested as a cancer therapeutic target. However, it is unclear about its role in BC. Here we unexpectedly observed that GABPA ablation inhibited TERT expression, but robustly increased proliferation, stem, and invasive phenotypes and cisplatin resistance in BC cells, while its overexpression exhibited opposite effects, and inhibited in vivo metastasizing in a xenograft transplant model. Mechanistically, GABPA directly activates the transcription of FoxA1 and GATA3, key transcription factors driving luminal differentiation of urothelial cells. Consistently, TCGA/GEO dataset analyses show that GABPA expression is correlated positively with luminal while negatively with basal signatures. Luminal tumors express higher GABPA than do basal ones. Lower GABPA expression is associated with the GABPA gene methylation or deletion (especially in basal subtype of BC tumors), and predicted significantly shorter patient survival based on TCGA and our cohort of BC patient analyses. Taken together, GABPA dictates luminal identity of BC cells and inhibits aggressive diseases in BC by promoting cellular differentiation despite its stimulatory effect on telomerase/TERT activation. Given these biological functions and its frequent methylation and/or deletion, GABPA serves as a tumor suppressor rather than oncogenic factor in BC. The GABPA effect on oncogenesis is context-dependent and its targeting for telomerase inhibition in BC may promote disease metastasizing.