Expression level of hTERT is regulated by somatic mutation and common single nucleotide polymorphism at promoter region in glioblastoma

Targeting oncogenic TERT promoter variants by allele-specific epigenome editing

BACKGROUND

Activation of dominant oncogenes by small or structural genomic alterations is a common driver mechanism in many cancers. Silencing of such dominantly activated oncogenic alleles, thus, is a promising strategy to treat cancer. Recently, allele-specific epigenome editing (ASEE) has been described as a means to reduce transcription of genes in an allele-specific manner. In cancer, specificity to an oncogenic allele can be reached by either targeting directly a pathogenic single-nucleotide variant or a polymorphic single-nucleotide variant linked to the oncogenic allele. To investigate the potential of ASEE in cancer, we here explored this approach by targeting variants at the TERT promoter region. The TERT promoter region has been described as one of the most frequently mutated non-coding cancer drivers.

RESULTS

Sequencing of the TERT promoter in cancer cell lines showed 53% (41/77) to contain at least one heterozygous sequence variant allowing allele distinction. We chose the hepatoblastoma cell line Hep-G2 and the lung cancer cell line A-549 for this proof-of-principle study, as they contained two different kinds of variants, namely the activating mutation C228T in the TERT core promoter and the common SNP rs2853669 in the THOR region, respectively. These variants were targeted in an allele-specific manner using sgRNA-guided dCas9-DNMT3A-3L complexes. In both cell lines, we successfully introduced DNA methylation specifically to the on-target allele of the TERT promoter with limited background methylation on the off-target allele or an off-target locus (VEGFA), respectively. We observed a maximum CpG methylation gain of 39% and 76% on the target allele when targeting the activating mutation and the common SNP, respectively. The epigenome editing translated into reduced TERT RNA expression in Hep-G2.

CONCLUSIONS

We applied an ASEE-mediated approach to silence TERT allele specifically. Our results show that the concept of dominant oncogene inactivation by allele-specific epigenome editing can be successfully translated into cancer models. This new strategy may have important advantages in comparison with existing therapeutic approaches, e.g., targeting telomerase, especially with regard to reducing adverse side effects.

Clinicopathological and Prognostic Values of Telomerase Reverse Transcriptase (TERT) Promoter Mutations in Ovarian Clear Cell Carcinoma for Predicting Tumor Recurrence, Platinum Resistance and Survival

BACKGROUND/AIM

A small subset of patients with ovarian clear cell carcinoma (OCCC) harbors telomerase reverse transcriptase promoter (TERTp) mutations. We aimed to analyze the clinicopathological and molecular characteristics of TERTp-mutant OCCC and investigate whether TERTp mutations are associated with the clinicopathological characteristics and outcomes of patients with OCCC.

PATIENTS AND METHODS

We included 11 OCCC cases in our study. Targeted sequencing was performed with a thorough review of pathology slides and electronic medical records.

RESULTS

Eleven OCCCs harbored two hotspot TERTp mutations: c.1-146C>T (6/11) and c.1-124C>T (5/11). All patients (11/11) who underwent postoperative adjuvant chemotherapy experienced tumor recurrence, and eight of them were classified as platinum-resistant. TERTp-mutant OCCC showed significantly higher frequencies of postoperative recurrence and relapse within six months of chemotherapy. TERTp mutations significantly predicted disease-free survival (DFS) in patients with OCCC.

CONCLUSION

We demonstrate that TERTp mutations have significant prognostic value for predicting tumor recurrence, platinum resistance, and worse DFS in patients with OCCC.

Transition Mutations in the hTERT Promoter Are Unrelated to Potential i-motif Formation in the C-Rich Strand

Increased expression of the human telomere reverse transcriptase (hTERT) in tumors promotes tumor cell survival and diminishes the survival of patients. Cytosine-to-thymine (C-to-T) transition mutations (C250T or C228T) in the hTERT promoter create binding sites for transcription factors, which enhance transcription. The G-rich strand of the hTERT promoter can form G-quadruplex structures, whereas the C-rich strand can form an i-motif in which multiple cytosine residues are protonated. We considered the possibility that i-motif formation might promote cytosine deamination to uracil and C-to-T mutations. We computationally probed the accessibility of cytosine residues in an i-motif to attack by water. We experimentally examined regions of the C-rich strand to form i-motifs using pH-dependent UV and CD spectra. We then incubated the C-rich strand with and without the G-rich complementary strand DNA under various conditions, followed by deep sequencing. Surprisingly, deamination rates did not vary substantially across the 46 cytosines examined, and the two mutation hotspots were not deamination hotspots. The appearance of mutational hotspots in tumors is more likely the result of the selection of sequences with increased promoter binding affinity and hTERT expression.

Prognostic role and interaction of TERT promoter status, telomere length and MGMT promoter methylation in newly diagnosed IDH wild-type glioblastoma patients

BACKGROUND

The clinical relevance of promoter mutations and single nucleotide polymorphism rs2853669 of telomerase reverse transcriptase (TERT) and telomere length in patients with isocitrate dehydrogenase (IDH) wild-type glioblastoma (GBM) patients remains unclear. Moreover, some studies speculated that TERT promoter status might influence the prognostic role of O6-methylguanine DNA methyltransferase (MGMT) promoter methylation in newly diagnosed GBM. We carried out a large study to investigate their clinical impact and their interaction in newly diagnosed GBM patients.

PATIENTS AND METHODS

We included 273 newly diagnosed IDH wild-type GBM patients who started treatment at Veneto Institute of Oncology IOV - IRCCS (Padua, Italy) from December 2016 to January 2020. TERT promoter mutations (-124 C>T and -146 C>T) and SNP rs2853669 (-245 T>C), relative telomere length (RTL) and MGMT methylation status were retrospectively assessed in this prospective cohort of patients.

RESULTS

Median overall survival (OS) of 273 newly diagnosed IDH wild-type GBM patients was 15 months. TERT promoter was mutated in 80.2% of patients, and most had the rs2853669 single nucleotide polymorphism as T/T genotype (46.2%). Median RTL was 1.57 (interquartile range 1.13-2.32). MGMT promoter was methylated in 53.4% of cases. At multivariable analysis, RTL and TERT promoter mutations were not associated with OS or progression-free survival (PFS). Notably, patients C carrier of rs2853669 (C/C+C/T genotypes) showed a better PFS compared with those with the T/T genotype (hazard ratio 0.69, P = 0.007). In terms of OS and PFS, all interactions between MGMT, TERT and RTL and between TERT and rs2853669 genotype were not statistically significant.

CONCLUSIONS

Our findings suggest the presence of the C variant allele at the rs2853669 of the TERT promoter as an attractive independent prognostic biomarker of disease progression in IDH wild-type GBM patients. RTL and TERT promoter mutational status were not correlated to survival regardless of MGMT methylation status.

The telomere maintenance mechanism spectrum and its dynamics in gliomas

Background

The activation of the telomere maintenance mechanism (TMM) is one of the critical drivers of cancer cell immortality. In gliomas, TERT expression and TERT promoter mutation are considered to reliably indicate telomerase activation, while ATRX mutation and/or loss indicates an alternative lengthening of telomeres (ALT). However, these relationships have not been extensively validated in tumor tissues.

Methods

Telomerase repeated amplification protocol (TRAP) and C-circle assays were used to profile and characterize the TMM cross-sectionally (n = 412) and temporally (n = 133) across glioma samples. WES, RNA-seq, and NanoString analyses were performed to identify and validate the genetic characteristics of the TMM groups.

Results

We show through the direct measurement of telomerase activity and ALT in a large set of glioma samples that the TMM in glioma cannot be defined solely by the combination of telomerase activity and ALT, regardless of TERT expression, TERT promoter mutation, and ATRX loss. Moreover, we observed that a considerable proportion of gliomas lacked both telomerase activity and ALT. This telomerase activation-negative and ALT negative group exhibited evidence of slow growth potential. By analyzing a set of longitudinal samples from a separate cohort of glioma patients, we discovered that the TMM is not fixed and can change with glioma progression.

Conclusions

This study suggests that the TMM is dynamic and reflects the plasticity and oncogenicity of tumor cells. Direct measurement of telomerase enzyme activity and evidence of ALT should be considered when defining TMM. An accurate understanding of the TMM in glioma is expected to provide important information for establishing cancer management strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-022-01095-x.

Evaluation of possible role of the hTERT gene rs2853669 polymorphism in the development of colorectal cancer as a genetic risk factor

Colorectal cancer (CRC) is the second deadliest malignancy. Human telomerase reverse transcriptase (hTERT) gene has been identified as one of the potential cancer susceptibility genes. We evaluated the relationship between the risk of CRC and CRC's clinicopathological features of the hTERT rs2853669 (A > G/T > C, by the chain direction) polymorphism in Turkish population. The rs2853669 polymorphism was investigated with the LightCycler 96 device in 100 CRC patients and 327 controls. We found that the rs2853669 polymorphism AG/GG genotypes in genetic models reduced the risk of CRC. However, there was no significant relationship between rs2853669 polymorphism and clinicopathological features of CRC in studied population. The results of this study showed that the risk of colorectal cancer is significantly reduced in the individuals having the G (C) allele. Our recommendation is to analyze the hTERT gene expression by studying the hTERT promoter mutations with this polymorphism in colorectal cancer.

Anchored Multiplex PCR Custom Melanoma Next Generation Sequencing Panel for Analysis of Circulating Tumor DNA

Detection of melanoma mutations using circulating tumor DNA (ctDNA) is a potential alternative to using genomic DNA from invasive tissue biopsies. To date, mutations in the GC-rich TERT promoter region, which is commonly mutated in melanoma, have been technically difficult to detect in ctDNA using next-generation sequencing (NGS) panels. In this study, we developed a custom melanoma NGS panel for detection of ctDNA, which encompasses the top 15 gene mutations in melanoma including the TERT promoter. We analyzed 21 stage III and IV melanoma patient samples who were treatment-naïve or on therapy. The overall detection rate of the custom panel, based on BRAF/NRAS/TERT promoter mutations, was 14/21 (67%) patient samples which included a TERT C250T mutation in one BRAF and NRAS mutation negative sample. A BRAF or NRAS mutation was detected in the ctDNA of 13/21 (62%) patients while TERT promoter mutations were detected in 10/21 (48%) patients. Co-occurrence of TERT promoter mutations with BRAF or NRAS mutations was found in 9/10 (90%) patients. The custom ctDNA panel showed a concordance of 16/21 (76%) with tissue based-detection and included 12 BRAF/NRAS mutation positive and 4 BRAF/NRAS mutation negative patients. The ctDNA mutation detection rate for stage IV was 12/16 (75%) and for stage III was 1/5 (20%). Based on BRAF, NRAS and TERT promoter mutations, the custom melanoma panel displayed a limit of detection of ~0.2% mutant allele frequency and showed significant correlation with droplet digital PCR. For one patient, a novel MAP2K1 H119Y mutation was detected in an NRAS/BRAF/TERT promoter mutation negative background. To increase the detection rate to >90% for stage IV melanoma patients, we plan to expand our custom panel to 50 genes. This study represents one of the first to successfully detect TERT promoter mutations in ctDNA from cutaneous melanoma patients using a targeted NGS panel.

Clinical and radiological findings of glioblastomas harboring a BRAF V600E mutation

The aim of this study was to analyze the clinical and radiological characteristics of glioblastomas (GBMs) harboring a BRAF mutation. Sequencing analysis of BRAF, IDH1/2, and TERT promoters was performed on GBM samples of patients older than 15 years. The clinical, pathological, and radiological data of patients were retrospectively reviewed. Patients were classified into three groups according to their BRAF and IDH1/2 status: BRAF group, IDH group, and BRAF/IDH-wild-type (WT) group. Among 179 GBM cases, we identified nine cases with a BRAF mutation and nine with IDH mutation. The WT group had 161 cases. Age at onset in the BRAF group was significantly lower compared to the WT group and was similar to the IDH group. In cases with negative IDH1-R132H staining and age < 55 years, 15.2% were BRAF-mutant cases. Similar to the IDH group, overall survival of the BRAF group was significantly longer compared with the WT group. Among nine cases in the BRAF group, three cases had hemorrhagic onset and prior lesions were observed in two cases. In conclusion, age < 55 years, being IDH1-R132H negative, with hemorrhagic onset or the presence of prior lesions are factors that signal recommendation of BRAF analysis for adult GBM patients.

TERT Promoter Mutations and rs2853669 Polymorphism: Useful Markers for Clinical Outcome Stratification of Patients With Oral Cavity Squamous Cell Carcinoma

Objective

To date, no useful prognostic biomarker exists for patients with oral squamous cell carcinoma (OCSCC), a tumour with uncertain biological behaviour and subsequent unpredictable clinical course. We aim to investigate the prognostic significance of two recurrent somatic mutations (-124 C>T and -146 C>T) within the promoter of telomerase reverse transcriptase (TERT) gene and the impact of TERT single nucleotide polymorphism (SNP) rs2853669 in patients surgically treated for OCSCC.

Methods

The genetic frequencies of rs2853669, -124 C>T and -146 C>T as well as the telomere length were investigated in 144 tumours and 57 normal adjacent mucosal (AM) specimens from OCSCC patients.

Results

Forty-five tumours harboured TERT promoter mutations (31.3%), with -124 C>T and -146 C>T accounting for 64.4% and 35.6% of the alterations respectively. Patients with -124 C>T TERT promoter mutated tumours had the shortest telomeres in the AM (p=0.016) and showed higher risk of local recurrence (hazard ratio [HR]:2.75, p=0.0143), death (HR:2.71, p=0.0079) and disease progression (HR:2.71, p=0.0024) with the effect being potentiated by the co-occurrence of T/T genotype of rs2853669.

Conclusion

-124 C>T TERT promoter mutation as well as the T/T genotype of the rs2853669 SNP are attractive independent prognostic biomarkers in patients surgically treated for OCSCC, with the coexistence of these genetic variants showing a synergistic impact on the aggressiveness of the disease.

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.

Exploring the Interplay of Telomerase Reverse Transcriptase and β-Catenin in Hepatocellular Carcinoma

Simple Summary

Liver cancer is one of the deadliest human cancers. Two of the most common molecular aberrations in liver cancer are: (1) activating mutations in the gene encoding β-catenin (CTNNB1); and (2) promoter mutations in telomerase reverse transcriptase (TERT). Here, we review recent findings regarding the interplay between TERT and β-catenin in order to better understand their role in liver cancer.

Abstract

Hepatocellular carcinoma (HCC) is one of the deadliest human cancers. Activating mutations in the telomerase reverse transcriptase (TERT) promoter (TERTp) and CTNNB1 gene encoding β-catenin are widespread in HCC (~50% and ~30%, respectively). TERTp mutations are predicted to increase TERT transcription and telomerase activity. This review focuses on exploring the role of TERT and β-catenin in HCC and the current findings regarding their interplay. TERT can have contradictory effects on tumorigenesis via both its canonical and non-canonical functions. As a critical regulator of proliferation and differentiation in progenitor and stem cells, activated β-catenin drives HCC; however, inhibiting endogenous β-catenin can also have pro-tumor effects. Clinical studies revealed a significant concordance between TERTp and CTNNB1 mutations in HCC. In stem cells, TERT acts as a co-factor in β-catenin transcriptional complexes driving the expression of WNT/β-catenin target genes, and β-catenin can bind to the TERTp to drive its transcription. A few studies have examined potential interactions between TERT and β-catenin in HCC in vivo, and their results suggest that the coexpression of these two genes promotes hepatocarcinogenesis. Further studies are required with vertebrate models to better understand how TERT and β-catenin influence hepatocarcinogenesis.

TERT and its binding protein: overexpression of GABPA/B in high grade gliomas

Enhanced expression of TERT in gliomas is a result of two hotspot mutations, C228T and C250T, at the promoter region. GA-binding proteins selectively bind at these positions, respectively, causing an activation of the promoter and overexpression of TERT. GABP is a multimeric protein consisting of GABPA and GABPB with its isoforms GABPB1, GABPB1-L, GABPB1-S, GABPB2. In this study, we investigated the mRNA expression and association between TERT and GABPA/B isoforms in tumor samples of different glioma grades. The expression was determined by quantitative real-time PCR and the results were statistically analyzed. We present that TERT is mainly expressed in primary glioblastomas. All GA-binding proteins progress through the glioma grades and have the highest expression levels in secondary glioblastomas. In secondary glioblastomas after chemotherapy, GABPB1 and GABPB1-L are expressed on a lower level than without treatment. In high grades, TERT and GABPA, GAPB1, GABPB1-L, GABPB1-S are upregulated compared to low grades. Between primary and secondary glioblastomas with and without chemotherapy, TERT is elevated in the former while GABPB1 is increased in the secondary glioblastomas. GABPA and GABPB1, GABPB1-L and GABPB1-S positive correlate in primary glioblastomas. The present study confirms the upregulation of TERT in primary glioblastomas while all GABP proteins rise with the malignancy of the gliomas. Further investigations must be made to elucidate the relation between TERT and all GABP proteins as it may play a key role in the gliomagenesis.

The interaction between TERT promoter mutation and MGMT promoter methylation on overall survival of glioma patients: a meta-analysis

Background

There are controversial results concerning the prognostic implication of TERT promoter mutation in glioma patients concerning MGMT status. In this meta-analysis, we investigated whether there are any interactions of these two genetic markers on the overall survival (OS) of glioma patients.

Methods

Electronic databases including PubMed and Web of Science were searched for relevant studies. Hazard ratio (HR) and its 95% confidence interval (CI) for OS adjusted for selected covariates were calculated from the individual patient data (IPD), Kaplan-Meier curve (KMC), or directly obtained from the included studies.

Results

A total of nine studies comprising 2819 glioma patients were included for meta-analysis. Our results showed that TERT promoter mutation was associated with a superior outcome in MGMT-methylated gliomas (HR = 0.73; 95% CI = 0.55–0.98; p-value = 0.04), whereas this mutation was associated with poorer survival in gliomas without MGMT methylation (HR = 1.86; 95% CI = 1.54–2.26; p-value < 0.001). TERT-mutated glioblastoma (GBM) patients with MGMT methylation benefited from temozolomide (TMZ) treatment (HR = 0.33; 95% CI = 0.23–0.47; p-value < 0.001). MGMT methylation was not related with any improvement in OS in TERT-wild type GBMs (HR = 0.80; 95% CI = 0.56–1.15; p-value = 0.23).

Conclusions

The prognostic value of TERT promoter mutation may be modulated by MGMT methylation status. Not all MGMT-methylated GBM patients may benefit from TMZ; it is possible that only TERT-mutated GBM with MGMT methylation, in particular, may respond.

TERT promoter mutation associated with multifocal phenotype and poor prognosis in patients with IDH wild-type glioblastoma

Background

Although mutations in the promoter region of the telomerase reverse transcriptase (TERTp) gene are the most common alterations in glioblastoma (GBM), their clinical significance remains unclear. Therefore, we investigated the impact of TERTp status on patient outcome and clinicopathological features in patients with GBM over a long period of follow-up.

Methods

We retrospectively analyzed 153 cases of GBM. Six patients with isocitrate dehydrogenase 1 (IDH1) or H3F3A gene mutations were excluded from this study. Among the 147 cases of IDH wild-type GBM, 92 (62.6%) had the TERTp mutation. Clinical, immunohistochemical, and genetic factors (BRAF, TP53 gene mutation, CD133, ATRX expression, O⁶-methylguanine-DNA methyltransferase [MGMT] promoter methylation) and copy number alterations (CNAs) were investigated.

Results

GBM patients with the TERTp mutation were older at first diagnosis versus those with TERTp wild type (66.0 vs. 60.0 years, respectively, P = .034), and had shorter progression-free survival (7 vs. 10 months, respectively, P = .015) and overall survival (16 vs. 24 months, respectively, P = .017). Notably, magnetic resonance imaging performed showed that TERTp-mutant GBM was strongly associated with multifocal/distant lesions (P = .004). According to the CNA analysis, TERTp mutations were positively correlated with EGFR amp/gain, CDKN2A deletion, and PTEN deletion; however, these mutations were negatively correlated with PDGFR amp/gain, CDK4 gain, and TP53 deletion.

Conclusions

TERTp mutations were strongly correlated with multifocal/distant lesions and poor prognosis in patients with IDH wild-type GBM. Less aggressive GBM with TERTp wild type may be a distinct clinical and molecular subtype of IDH wild-type GBM.

TERT Promoter Mutations Differently Correlate with the Clinical Outcome of MAPK Inhibitor-Treated Melanoma Patients

Resistance is a major challenge in the management of mitogen-activated protein kinase inhibitor (MAPKi)-treated metastatic melanoma. Tumor genetic alterations can cause MAPK pathway reactivation, leading to lack of response and poor outcome. Characterization of the mutational profile in patients with melanoma might be crucial for patient-tailored treatment choices. Mutations in the promoter region of the telomerase reverse transcriptase gene (TERTprom) lead to increased TERT expression and telomerase activity and are frequent in BRAF^V600 mutant melanoma. Reportedly, TERTprom, and BRAF^V600 mutations cooperate in driving cancer progression and aggressiveness. We evaluated the effect of the TERTprom status on the clinical outcome in 97 MAPKi-treated melanoma patients. We observed that patients with the c.-146C > T mutation showed a significantly worse progression-free survival (PFS) compared to those carrying the c.-124C > T mutation and a two-fold increased risk of progression (median 5.4 vs. 9.5 months; hazard ratio (HR) 1.9; 95% confidence interval (CI) 1.2–3.2; p = 0.013). This trend was also observed for the overall survival (OS); melanoma patients with the c.-146C > T mutation showed a poorer prognosis compared to those with the c.-124C > T mutation (median 13.3 vs. 25.5 months; HR 1.9, 95% CI 1.1–3.3, p = 0.023). Our results disclose a different correlation of the two TERTprom mutations with MAPKi-treated melanoma patient outcome, highlighting a different impact of the pathway blockade.

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.

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.

Spinal cord anaplastic astrocytoma with BRAF V600E mutation: A case report and review of literature

A 17-year-old female complained of lower extremity pain that progressed to low back pain accompanied by paraparesis. Magnetic resonance imaging revealed a mass in the conus medullaris of the spinal cord at the thoracic spine 11-12 level. The patient underwent resection of the mass. The pathological diagnosis was anaplastic astrocytoma based on the densely proliferating astrocytic tumor cells without necrosis or microvascular proliferation. The patient received chemoradiotherapy with oral temozolomide and a total of 54 Gy of local irradiation, followed by 24 courses of temozolomide as maintenance chemotherapy. The patient survived for 8 years without tumor recurrence following the initial treatment. Genetic analysis of the tumor revealed a BRAF V600E mutation that has not yet been reported in spinal cord high-grade gliomas (HGGs). In recent years, the molecular therapy targeting the BRAF V600E mutation has been applied in clinical practice for several cancer types. Although the frequency in spinal cord HGGs is uncertain, it is necessary to investigate BRAF V600E mutation as a potential therapeutic target in the future.

Frequency of somatic mutations in TERT promoter, TP53 and CTNNB1 genes in patients with hepatocellular carcinoma from Southern Italy

Somatic mutations in the TERT promoter and in the TP53 and CTNNB1 genes are considered drivers for hepatocellular carcinoma (HCC) development. They show variable frequencies in different geographic areas, possibly depending on liver disease etiology and environmental factors. TP53, CTNNB1 and TERT genetic mutations were investigated in tumor and non-tumor liver tissues from 67 patients with HCC and liver tissue specimens from 41 control obese subjects from Southern Italy. Furthermore, TERT expression was assessed by reverse transcription-quantitative PCR. Neither CTNNB1 mutations or TP53 R249S substitution were detected in any case. The TP53 R72P polymorphism was found in 10/67 (14.9%) tumors, but was not found in either non-tumor tissues (P=0.001) or controls (P=0.009). TERT gene promoter mutations were found in 29/67 (43.3%) tumor tissues but were not found in either non-tumor (P<0.0001) or control liver specimens (P<0.0001). The most frequent mutation in the tumors was the known hot spot at -124 bp from the TERT ATG start site (-124G>A, 28 cases, 41.8%; P<0.0001). A new previously never reported TERT promoter mutation (at -297 bp from the ATG, -297C>T) was found in 5/67 (7.5%) tumors, in 0/67 (0%) non-tumor (P<0.0001), and in 0/41 (0%) controls (P=0.07). This mutation creates an AP2 consensus sequence, and was found alone (1 case) or in combination (4 cases) with the -124 bp mutation. The mutation at -124 and -297 bp induced a 33-fold (P<0.0001) and 40-fold increase of TERT expression levels, respectively. When both mutations were present, TERT expression levels were increased >300-fold (P=0.001). A new TERT promoter mutation was identified, which generates a de novo binding motif for AP2 transcription factors, and which significantly increases TERT promoter transcriptional activity.

Spectrum of TERT promoter mutations and mechanisms of activation in thyroid cancer

BACKGROUND

Reactivation of telomerase reverse transcriptase (TERT) is an important event in cancer. Two hotspot mutations in the TERT promoter region, c.-124C > T (C228T) and c.-146C > T (C250T), occur in various cancer types including thyroid cancer. They generate de novo binding sites for E-twenty-six (ETS) transcription factors causing increased TERT transcription. The aim of this study was to search for novel TERT promoter mutations and additional mechanisms of TERT activation in thyroid cancer.

METHODS

We studied 198 papillary thyroid carcinomas (PTCs), 34 follicular thyroid carcinomas (FTCs), 40 Hürthle cell carcinomas (HCCs), 14 poorly differentiated/anaplastic thyroid carcinomas (PDTC/ATC), and 15 medullary thyroid carcinomas (MTCs) for mutations in an -424 bp to +64 bp region of TERT. The luciferase reporter assay was used to functionally characterize the identified alterations. Copy number variations (CNVs) in the TERT region were analyzed using TaqMan copy number assay and validated with fluorescence in situ hybridization (FISH).

RESULTS

We detected the hotspot c.-124C > T and c.-146C > T mutations in 7% PTC, 18% FTC, 25% HCC, and 86% PDTC/ATC. One PTC carried a c.-124C > A mutation. Furthermore, we identified two novel mutations resulting in the formation of de novo ETS-binding motifs: c.-332C > T in one MTC and c.-104_-83dup in one PTC. These genetic alterations, as well as other detected mutations, led to a significant increase in TERT promoter activity when assayed using luciferase reporter system. In addition, 5% of thyroid tumors were found to have ≥3 copies of TERT.

CONCLUSIONS

This study confirms the increased prevalence of TERT promoter mutations and CNV in advanced thyroid cancers and describes novel functional alterations in the TERT gene promoter, including a point mutation and small duplication. These mutations, as well as TERT copy number alterations, may represent an additional mechanism of TERT activation in thyroid cancer.

Prognostic significance of human telomerase reverse transcriptase promoter region mutations C228T and C250T for overall survival in spinal chordomas

BACKGROUND

Spinal chordomas, a subtype of primary spinal column malignancies (PSCM), are rare tumors with poor prognosis, and we have limited understanding of the molecular drivers of neoplasia.

METHODS

Study design was a retrospective review of prospectively collected data with cross-sectional survival. Archived paraffin embedded pathologic specimens were collected for 133 patients from 6 centers within Europe and North America between 1987 and 2012. Tumor DNA was extracted and the human telomerase reverse transcriptase (hTERT) promoter was sequenced. The hTERT mutational status was correlated with overall survival (OS) and time to first local recurrence.

RESULTS

Ninety-two chordomas, 26 chondrosarcomas, 7 osteosarcomas, 3 Ewing's sarcomas, and 5 other malignant spinal tumors were analyzed. Median OS following surgery was 5.8 years (95% CI: 4.6 to 6.9) and median time to first local recurrence was 3.9 years (95% CI: 2.5 to 6.7). Eight chordomas, 2 chondrosarcomas, 1 Ewing's sarcoma, and 1 other malignant spinal tumor harbored either a C228T or C250T mutation in the hTERT promoter. In the overall cohort, all patients with hTERT mutation were alive at 10 years postoperative with a median OS of 5.1 years (95% CI: 4.5 to 6.6) (P = 0.03). hTERT promoter mutation was observed in 8.7% of spinal chordomas, and 100% of chordoma patients harboring the mutation were alive at 10 years postoperative compared with 67% patients without the mutation (P = 0.05).

CONCLUSIONS

We report for the first time that hTERT promoter mutations C228T and C250T are present in approximately 8.7% of spinal chordomas. The presence of hTERT mutations conferred a survival benefit and could potentially be a valuable positive prognostic molecular marker in spinal chordomas.

Telomere Maintenance Mechanisms in Cancer

Tumour cells can adopt telomere maintenance mechanisms (TMMs) to avoid telomere shortening, an inevitable process due to successive cell divisions. In most tumour cells, telomere length (TL) is maintained by reactivation of telomerase, while a small part acquires immortality through the telomerase-independent alternative lengthening of telomeres (ALT) mechanism. In the last years, a great amount of data was generated, and different TMMs were reported and explained in detail, benefiting from genome-scale studies of major importance. In this review, we address seven different TMMs in tumour cells: mutations of the TERT promoter (TERTp), amplification of the genes TERT and TERC, polymorphic variants of the TERT gene and of its promoter, rearrangements of the TERT gene, epigenetic changes, ALT, and non-defined TMM (NDTMM). We gathered information from over fifty thousand patients reported in 288 papers in the last years. This wide data collection enabled us to portray, by organ/system and histotypes, the prevalence of TERTp mutations, TERT and TERC amplifications, and ALT in human tumours. Based on this information, we discuss the putative future clinical impact of the aforementioned mechanisms on the malignant transformation process in different setups, and provide insights for screening, prognosis, and patient management stratification.

Association between TERT rs2853669 polymorphism and cancer risk: A meta-analysis of 9,157 cases and 11,073 controls

Background

It has been reported that the functional telomerase reverse transcriptase (TERT) rs2853669 polymorphism might contribute to different types of human cancer. However, the association of this mutation with cancer remains controversial. Here, we conducted a meta-analysis to characterize this relationship.

Materials and methods/Main results

A systematic search of studies on the association of TERT rs2853669 polymorphism with all types of cancer was conducted in PubMed, Embase and Cochrane Library. The summary odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs) were used to pool the effect size in a fixed-effects model or a random-effects model where appropriate. A total of 13 articles and 15 case-control studies, including 9,157 cases and 11,073 controls, were included in this meta-analysis. Overall, the pooled results indicated that the rs2853669 polymorphism was significantly associated with increased cancer risk in a homozygote comparison model (CT vs. TT: OR = 1.085, 95% CI: 1.015–1.159, P = 0.016). In the stratified analyses, a significant increased cancer risk was observed in Asian, but not Caucasian patients. A subgroup analysis by cancer type also revealed a significant increase in the risk of lung cancer, but not breast cancer.

Conclusions

The results of this meta-analysis suggest that the TERT rs2853669 polymorphism is associated with a significantly increased risk of cancer, particularly lung cancer, in Asian populations.

Elevated TERT Expression in TERT-Wildtype Adult Diffuse Gliomas: Histological Evaluation with a Novel TERT-Specific Antibody

Telomerase reverse transcriptase (TERT) is important for the biology of diffuse gliomas. TERT promoter mutations are selectively observed among 1p/19q-codeleted oligodendrogliomas and isocitrate dehydrogenase gene- (IDH-) wildtype glioblastoma (GBM). However, TERT transcripts range widely in various cancers including gliomas, and TERT protein expression has been rarely investigated thus far. It would be thus critical to examine the expression level of TERT in tumors in addition to its mutational status, and sensitive and specific methods are urgently needed to examine TERT protein expression for the assessment of TERT biology in gliomas. Using our newly developed TERT-specific monoclonal antibody (TMab-6) applicable to human tissue, we found an unexpected increase in TERT expression in TERT-wildtype as well as TERT-mutated gliomas and in tumor vasculature. This is the first extensive analysis on the expression of TERT immunoreactivity in human glioma tissue, suggesting that TERT protein expression may be regulated by several mechanisms in addition to its promoter mutation.

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

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

TERT promoter mutations and their correlation with BRAF and RAS mutations in a consecutive cohort of 145 thyroid cancer cases

Papillary thyroid carcinoma (PTC) is the most common type of endocrine malignancy and accounts for ~80% of thyroid carcinomas in adults and 90% in children. Risk stratification is important for identifying patients at higher risk and, for this reason, recent advances in molecular genetics of thyroid cancer can be applied to provide novel biomarkers useful in understanding tumor behavior. B-Raf proto-oncogene, serine/threonine kinase (BRAF) and rat sarcoma (RAS) mutations have been widely studied and appear to have an important role in thyroid tumorigenesis. Somatic telomerase reverse transcriptase (TERT) promoter mutations have been recently identified in several types of malignant tumors, including thyroid neoplasia; however, the actual role of TERT mutations in thyroid tumorigenesis is still under debate. In the present study, the mutational status of BRAF, RAS and TERT was analyzed in order to elucidate the roles of these genes in thyroid tumorigenesis. The TERT mutational analysis was also correlated with an immunohistochemical study of TERT protein expression. According to the literature, our data provide evidence of the BRAF and RAS roles in thyroid tumorigenesis, supporting an association between BRAF (V600E) mutations and the more aggressive clinical and pathological features of thyroid tumors. By contrast, TERT mutations were not significantly associated with any clinical parameters; therefore, its role in initial tumorigenesis should be further investigated.

Comprehensive molecular characterization of multifocal glioblastoma proves its monoclonal origin and reveals novel insights into clonal evolution and heterogeneity of glioblastomas

Background

The evolution of primary glioblastoma (GBM) is poorly understood. Multifocal GBM (ie, multiple synchronous lesions in one patient) could elucidate GBM development.

Methods

We present the first comprehensive study of 12 GBM foci from 6 patients using array-CGH, spectral karyotyping, gene expression arrays, and next-generation sequencing.

Results

Multifocal GBMs genetically resemble primary GBMs. Comparing foci from the same patient proved their monoclonal origin. All tumors harbored alterations in the 3 GBM core pathways: RTK/PI3K, p53, and RB regulatory pathways with aberrations of EGFR and CDKN2A/B in all (100%) patients. This unexpected high frequency reflects a distinct genetic signature of multifocal GBMs and might account for their highly malignant and invasive phenotype. Surprisingly, the types of mutations in these genes/pathways were different in tumor foci from the same patients. For example, we found distinct mutations/aberrations in PTEN, TP53, EGFR, and CDKN2A/B, which therefore must have occurred independently and late during tumor development. We also identified chromothripsis as a late event and in tumors with wild-type TP53. Only 2 events were found to be early in all patients: single copy loss of PTEN and TERT promoter point mutations.

Conclusions

Multifocal GBMs develop through parallel genetic evolution. The high frequency of alterations in 3 main pathways suggests that these are essential steps in GBM evolution; however, their late occurrence indicates that they are not founder events but rather subclonal drivers. This might account for the marked genetic heterogeneity seen in primary GBM and therefore has important implications for GBM therapy.

Primary Astrocytic Tumours and Paired Recurrences have Similar Biological Features in IDH1, TP53 and TERTp Mutation and MGMT, ATRX Loss

Astrocytic tumours are the most common type of primary malignant brain tumour. Most astrocytic tumours will recur at some point after surgery. Currently, the combination of radiotherapy and chemotherapy does not prevent the recurrence of astrocytic tumours. In this study, we investigated the consistency in isocitrate dehydrogenase 1 (IDH1), tumour protein p53 (TP53) and telomerase reverse transcriptase promoter (TERTp) mutations during astrocytic tumour recurrence. We also evaluated the protein loss of O-6-methylguanine-DNA methyltransferase (MGMT) and alpha-thalassemia/mental retardation, X-linked (ATRX) during disease recurrence. We then determined the prognostic significance of these findings in terms of progression-free survival (PFS) using Kaplan-Meier analysis and Cox regression models. Our results showed that in most cases, IDH1, TP53 and TERTp mutation status and MGMT and ATRX protein expression levels were stable during recurrence, which may indicate that these alterations occurred early in astrocytic tumour development. Furthermore, in IDH1 wild type group, the patients who were negative for MGMT and had a low Ki67 index showed a longer PFS. Therefore, we suggest that IDH1 mutation combined with MGMT expression level and Ki67 index might be an effective biomarker panel for evaluating the PFS of patients with astrocytic tumours.

TERT promoter mutation and its interaction with IDH mutations in glioma: Combined TERT promoter and IDH mutations stratifies lower-grade glioma into distinct survival subgroups-A meta-analysis of aggregate data

The clinical significance of telomerase reverse transcriptase (TERT) promoter mutation in glioma remains unclear. The aim of our meta-analysis is to investigate the prognostic impact TERT promoter mutation in glioma patients and its interaction with other molecular markers, particularly Isocitrate Dehydrogenase (IDH) mutation from aggregate level data. Relevant articles were searched in four electronic databases including PubMed, Scopus, Web of Science and Virtual Health Library. Pooled HRs were calculated using random effect model weighted by inverse variance method. From 1010 studies, we finally included 28 studies with 11519 patients for meta-analyses. TERT mutation is significantly associated with compromised overall survival (OS) (HR=1.38; 95% CI=1.15-1.67) and progression-free survival (PFS) (HR=1.31; 95% CI=1.06-1.63) in glioma patients. In studying its reaction with IDH, TERT promoter mutation was associated with reduced OS in both IDH-mutant (IDH-mut) and IDH-wild type (IDH-wt) glioblastomas but shown to have inverse effects on IDH-mut and IDH-wt grade II/III tumors. Our analysis categorized WHO grade II/III glioma patients into four distinct survival subgroups with descending survival as follow: TERT-mut/IDH-mut≫TERT-wt/IDH-mut≫TERT-wt/IDH-wt≫TERT-mut/IDH-wt. Prognostic value of TERT promoter mutations in gliomas is dependent on tumor grade and the IDH mutational status. With the same tumor grade in WHO grade II and III tumors and the same IDH mutation status, TERT-mut is a prognostic factor.

Human TERT promoter mutation enables survival advantage from MGMT promoter methylation in IDH1 wild-type primary glioblastoma treated by standard chemoradiotherapy

Background

Promoter mutation in the human telomerase reverse transcriptase gene (hTERT) occurs in ~75% of primary glioblastoma (GBM). Although the mutation appears to upregulate telomerase expression and contributes to the maintenance of telomere length, its clinical significance remains unclear.

Methods

We performed hTERT promoter genotyping on 303 isocitrate dehydrogenase 1 wild-type GBM tumors treated with standard chemoradiotherapy. We also stratified 190 GBM patients from the database of The Cancer Genome Atlas (TCGA) by hTERT gene expression. We analyzed overall and progression-free survival by Kaplan-Meier and Cox regression.

Results

We detected hTERT promoter mutation in 75% of the patients. When included as the only biomarker, hTERT mutation was not prognostic in our patient cohort by Cox regression analysis. However, when hTERT and O6-DNA methylguanine-methyltransferase (MGMT) were included together, we observed an interaction between these 2 factors. To further investigate this interaction, we performed pairwise comparison of the 4 patient subcohorts grouped by hTERT-MGMT status (MUT-M, WT-M, MUT-U, and WT-U). MGMT methylated patients showed improved survival only in the presence of hTERT promoter mutation: MUT-M versus MUT-U (overall survival of 28.3 vs 15.9 mos, log-rank P < .0001 and progression-free survival of 15.4 vs 7.86 mo, log-rank P < .0001). These results were confirmed by Cox analyses. Analogously, the cohort from TCGA demonstrated survival benefit of MGMT promoter methylation only in patients with high hTERT expression. In addition, hTERT mutation was negatively prognostic in our MGMT unmethylated patients, while the analogous association with high expression was not observed in the cohort from TCGA.

Conclusion

The prognostic influence of MGMT promoter methylation depends on hTERT promoter mutation. This interaction warrants further mechanistic investigation.

TERT promoter status and gene copy number gains: effect on TERT expression and association with prognosis in breast cancer

Upregulation of the telomerase reverse transcriptase (TERT) gene in human cancers leads to telomerase activation, which contributes to the growth advantage and survival of tumor cells. Molecular mechanisms of TERT upregulation are complex, tumor-specific and can be clinically relevant. To investigate these mechanisms in breast cancer, we sequenced the TERT promoter, evaluated TERT copy number changes and assessed the expression of the MYC oncogene, a known transcriptional TERT regulator, in two breast cancer cohorts comprising a total of 122 patients. No activating TERT promoter mutations were found, suggesting that this mutational mechanism is not likely to be involved in TERT upregulation in breast cancer. The T349C promoter polymorphism found in up to 50% of cases was not correlated with TERT expression, but T349C carriers had significantly shorter disease-free survival. TERT gains (15-25% of cases) were strongly correlated with increased TERT mRNA expression and worse patient prognosis in terms of disease-free and overall survival. Particularly aggressive breast cancers were characterized by an association of TERT gains with MYC overexpression. These results evidence a significant effect of gene copy number gain on the level of TERT expression and provide a new insight into the clinical significance of TERT and MYC upregulation in breast cancer.

BRAF Mutation is Associated with an Improved Survival in Glioma-a Systematic Review and Meta-analysis

Newly emerged molecular markers in gliomas provide prognostic values beyond the capabilities of histologic classification. BRAF mutation, especially BRAF V600E, is common in a subset of gliomas and may represent a potential prognostic marker. The aim of our study is to investigate the potential use of BRAF mutations on prognosis of glioma patients. Four electronic databases were searched for potential articles, including PubMed, Scopus, ISI Web of Science, and Virtual Health Library (VHL). Data of hazard ratio (HR) for overall survival (OS) and progression-free survival (PFS) were directly obtained from original papers or indirectly estimated from Kaplan Meier curve (KMC). A random effect model weighted by inverse variance method was used to calculate the pooled HR. From 705 articles, we finally included 11 articles with 1308 glioma patients for the final analysis. The overall estimates showed that BRAF V600E was associated with an improved overall survival (OS) in glioma patients (HR = 0.60; 95% CI = 0.44-0.80). Results for progression-free survival (PFS), however, were not statistically significant (HR = 1.39; 95% CI = 0.82-2.34). In subgroup analyses, BRAF V600E showed its effect in improving survival in pediatric and young adult gliomas (under 35 years) but did not have prognostic value in old adult. Additionally, BRAF V600E was only associated with a favorable prognosis in lower grade glioma. Our meta-analysis provides evidence that BRAF mutation has a favorable prognostic impact in gliomas and its prognostic value might be dependent on patient age and tumor grade. This mutation can be used as a prognostic factor in glioma but additional studies are required to clarify its prognostic value taking into account other confounding factors.

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

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

Association between rs2853669 in TERT gene and the risk and prognosis of human cancer: a systematic review and meta-analysis

The polymorphism rs2853669 within the promoter of telomerase reverse transcriptase gene (TERTp) has been debated about its role in cancer risk and prognosis. Additionally, several studies report inconsistent results concerning the modifying effect of rs2853669 on the prognostic value of TERTp mutations in cancer patients. Here, we performed this meta-analysis to comprehensively evaluate the role of rs2853669 in the risk and prognosis of human cancer, and further assess its modifying impact on TERTp mutations in the survival of cancer patients. We systematically searched literature via PubMed, Web of Science, and EMBASE through July 2016, and included 22 eligible studies. The overall analysis (64,119 cases and 78,988 controls) demonstrated that rs2853669 did not increase or decrease the overall cancer risk. Subsequent analyses also did not reveal any association between rs2853669 and overall cancer prognosis. However, we identified a modifying effect of rs2853669 on TERTp mutations in that, among cancer patients with TERTp mutations, only those carrying the TT genotype had a poor survival (Hazard ratio = 1.56, 95% confidence interval = 1.06-2.28); subgroup analyses by cancer type also supported these results. In conclusion, our findings suggest that rs2853669 could be important for assessing the prognostic value of TERTp mutations. Future large studies are required to further validate our results.

The TERT promoter SNP rs2853669 decreases E2F1 transcription factor binding and increases mortality and recurrence risks in liver cancer

A common single-nucleotide polymorphism in the telomerase reverse transcriptase (TERT) promoter, rs2853669 influences patient survival rates and the risk of developing cancer. Recently, several lines of evidence suggest that the rs2853669 suppresses TERT promoter mutation-mediated TERT expression levels and cancer mortality as well as recurrence rates. However, no reports are available on the impact of rs2853669 on TERT expression in hepatocellular carcinoma (HCC) and its association with patient survival. Here, we found that HCC-related overall and recurrence-free survival rates were not associated with TERT promoter mutation individually, but rs2853669 and the TERT promoter mutation in combination were associated with poor survival rates. TERT mRNA expression and telomere fluorescence levels were greater in patients with HCC who had both the combination. The combination caused TERT promoter methylation through regulating the binding of DNA methyltransferase 1 and histone deacetylase 1 to the TERT promoter in HCC cell lines. The TERT expression level was significantly higher in HCC tumor with a methylated promoter than in that with an unmethylated promoter. In conclusion, we demonstrate a substantial role for the rs2853669 in HCC with TERT promoter mutation, which suggests that the combination of the rs2853669 and the mutation indicate poor prognoses in liver cancer.

hTERT promoter methylation in meningiomas and central nervous hemangiopericytomas

In meningiomas, prognostic impact of mutations in the human telomerase reverse transcriptase (hTERT) promoter region was recently shown, while studies of promoter methylation and analyses of hemangiopericytomas are lacking. hTERT promoter methylation was analyzed in 78 meningioma and 38 meningeal hemangiopericytoma samples by methylation-specific polymerase chain reaction (MS-PCR) and compared with histopathological and clinical variables and with immunohistochemical hTERT expression. Promoter methylation was found in 62 samples (53 %) and tended to be higher in meningiomas (N = 19/41, 46 %) than in hemangiopericytomas (N = 8/33, 24 %, p = .057). In meningiomas, methylation was 16, 60 and 77 % in grade I, II and III tumors (p < .001) and higher in recurrent (N = 33/37, 89 %) than in primary diagnosed (N = 19/41, 46 %) tumors (OR 5.14, 95 % CI 1.34-19.71, p = .017). Univariate analyses showed shorter mean progression free and overall survival in methylated than in unmethylated individuals (26 vs. 100 months; p = .045 and 110 vs. 113 months; p = .025, respectively). Moreover, hTERT expression was found in 70 % (N = 53) and was more frequent in methylated than in unmethylated samples (78 vs. 52 %, OR 3.36, 95 % CI 1.20-9.40, p = .021). In hemangiopericytomas, methylation was similar in grade II (24 %) and III (25 %, p > .05) and in primary (24 %) and recurrent tumors (40 %, p > .05). hTERT expression was similar as compared to meningiomas (74 %, N = 28, p > .05) but was independent of promoter methylation (OR 4.26, 95 % CI 0.47-39.0, p = .199). In meningeal tumors, hTERT promoter methylation is more common than mutations and in meningiomas but not in hemangiopericytomas positively correlated with WHO grade and hTERT expression.

TERT Genetic Mutations as Prognostic Marker in Glioma

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

Nrf2-driven TERT regulates pentose phosphate pathway in glioblastoma

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

TERT promoter mutations and polymorphisms as prognostic factors in primary glioblastoma

Telomerase reverse transcriptase (TERT) activity is up-regulated in several types of tumors including glioblastoma (GBM). In the present study, 128 primary glioblastoma patients were examined for single nucleotide polymorphisms of TERT in blood and in 92 cases for TERT promoter mutations in tumors. TERT promoter mutations were observed in 86% of the tumors and of these, C228T (-124 bp upstream start codon) was detected in 75% and C250T (-146 bp) in 25% of cases. TERT promoter mutations were associated with shorter overall survival (11 vs. 20 months p = 0.002 and 12 vs. 20, p = 0.04 for C228T and C250T, respectively). The minor alleles of rs2736100 and rs10069690 SNP's, located in intron 2 and the promotor regions, respectively, were associated with an increased risk of developing GBM (p = 0.004 and 0.001). GBM patients having both TERT promoter mutations and being homozygous carriers of the rs2853669 C-allele displayed significantly shorter overall survival than those with the wild type allele. The rs2853669 SNP is located in a putative Ets2 binding site in the promoter (-246 bp upstream start codon) close to the C228T and C250T mutation hot spots. Interleukin-6 (IL-6) expression regulated by TERT promoter status and polymorphism, what leads us to think that TERT and IL-6 plays a significant role in GBM, where specific SNPs increase the risk of developing GBM while the rs2853669 SNP and specific mutations in the TERT promoter of the tumor lead to shorter survival.

Clinical Characteristics and Prognostic Significance of TERT Promoter Mutations in Cancer: A Cohort Study and a Meta-Analysis

BACKGROUND

The prevalence of telomerase reverse transcriptase (TERT) promoter mutations (pTERTm) in non-small-cell lung cancer (NSCLC) have been investigated, but the results were inconsistent. In addition, several studies have analysed the role of pTERTm in the etiology of various types of cancers, however, the results also remain inconsistent.

METHODS

The genomic DNA sequence of 103 NSCLC samples were analysed to investigate the frequency of pTERTm in these patients and to establish whether these mutations are associated with their clinical data. Furthermore, a meta-analysis based on previously published articles and our cohort study was performed to investigate the association of pTERTm with patient gender, age at diagnosis, metastasis status, tumour stage and cancer prognosis (5-year overall survival rate).

RESULTS

In the cohort study, 4 patients had C228T and 2 had C250T, with a total mutation frequency up to 5.8%. Significant difference of clinical data between pTERTm carriers and noncarriers was only found in age at diagnosis. In the meta-analysis, We found that pTERTm carriers in cancer patients are older than noncarriers (Mean difference (MD) = 5.24; 95% confidence interval [CI], 2.00 to 8.48), male patients were more likely to harbour pTERTm (odds Ratios (OR) = 1.38; 95% CI, 1.22 to 1.58), and that pTERTm had a significant association with distant metastasis (OR = 3.78; 95% CI, 2.45 to 5.82), a higher tumour grade in patients with glioma (WHO grade III, IV vs. I, II: OR, 2.41; 95% CI, 1.88 to 3.08) and a higher tumour stage in other types of cancer (III, IV vs. I, II: OR, 2.48; 95% CI, 1.48 to 4.15). pTERTm was also significantly associated with a greater risk of death (hazard ratio = 1.71; 95% CI, 1.41 to 2.08).

CONCLUSIONS

pTERTm are a moderately prevalent genetic event in NSCLC. The current meta-analysis indicates that pTERTm is associated with patient age, gender and distant metastasis. It may serves as an adverse prognostic factor in individuals with cancers.

TERT promoter mutations and rs2853669 polymorphism: prognostic impact and interactions with common alterations in glioblastomas

TERT promoter (TERTp) mutation is the most common mutation in glioblastomas. It creates a putative binding site for Ets/TCF transcription factors, enhancing telomerase expression and activity, whereas the rs2853669 variant disrupts another Ets/TCF binding. We explore here the interaction between these two alterations, tumor genomic profile and the impact on prognosis. The TERTp and rs2853669 statuses were determined and confronted with the outcome and molecular profile, i.e., loss of chromosome 10q, CDKN2A deletion, IDH mutation, EGFR amplification, MGMT promoter methylation. 651 glioblastomas were selected (sex ratio = 1.35, median age 60.4 years, median survival 13.5 months). The TERTp mutation found in 481 patients (74 %) was independent from rs2853669 genotypes. TERTp mutation, but not rs2853669 status, was associated with older age (61.4 vs. 52.8 years). rs2853669 status had no impact on overall survival (OS) either in mutated TERTp or wild-type TERTp. Neither rs2736100 (TERT, 5q15.33) nor rs192011116 (TERC, 3q26.2) status had any impact on survival or showed any association with a TERTp mutation. The TERTp mutation was associated with EGFR amplification chromosome 10q loss, CDKN2A deletion and IDH wt. EGFR amplification was associated with a better outcome in TERTp mutated GBM, and a worse outcome in TERTp WT. This study-the largest analyzing the TERTp mutation and the rs2853669 polymorphism-fails to find any prognostic impact of rs2853669. It confirms the dual prognostic impact of EGFR amplification depending on TERTp status.

Hotspot TERT promoter mutations are rare events in testicular germ cell tumors

The abnormal activation of telomerase, codified by the telomerase reverse transcriptase (TERT) gene, is related to one of cancer hallmarks. Hotspot somatic mutations in the promoter region of TERT, specifically the c.-124:C>T and c.-146:C>T, were recently identified in a range of human cancers and have been associated with a more aggressive behavior. Testicular germ cell tumors frequently exhibit a good prognosis; however, the development of refractory disease is still a clinical challenge. In this study, we aim to evaluate for the first time the presence of the hotspot telomerase reverse transcriptase gene promoter mutations in testicular germ cell tumors. A series of 150 testicular germ cell tumor cases and four germ cell tumor cell lines were evaluated by PCR followed by direct Sanger sequencing and correlated with patient's clinical pathological features. Additionally, we genotyped the telomerase reverse transcriptase gene promoter single nucleotide polymorphism rs2853669 (T>C) located at -245 position. We observed the presence of the TERT promoter mutation in four patients, one exhibited the c.-124:C>T and three the c.-146:C>T. No association between TERT mutation status and clinicopathological features could be identified. The analysis of the rs2853669 showed that variant C was present in 22.8 % of the cases. In conclusion, we showed for the first time that TERT promoter mutations occur in a small subset (~3 %) of testicular germ cell tumors.

hTERT promoter methylation in pituitary adenomas

Telomerase reverse transcriptase (TERT) expression is a hallmark in tumorigenesis and upregulated due to mutations and methylation of the human (h)TERT promoter. As mutations are rare but methylation is common in pituitary adenomas (PA), we determined promoter methylation and its clinical impact in 85 primary and 15 recurrent PA by methylation-specific PCR. 40 females (47%) and 45 males (53%) with a median age of 53 years harboring micro-, macro-, and giant adenomas in 12, 82, and 6% were included (prolactinomas, corticotroph, somatotroph, gonadotroph, thyreotroph, plurihormonal, and null cell adenomas in 11, 18, 10, 29, 1, 10, and 21%, respectively). In primary diagnosed tumors, methylation rate was 27% and higher in males than in females (40 vs. 13%, p = 0.001) after uni- and multivariate analyses. Methylation differed among PA subtypes (0-42%, p = n.s.) and was not significantly correlated with tumor size, cavernous sinus invasion, or serum hormone levels. Ki67 labeling index and recurrence (N = 16, 19%) were independent of methylation. In recurrent tumors, methylation was similar to primary PA (N = 5/15, 33%) and remained unchanged along follow-up. Thus, while being commonly observed in PA, hTERT promoter methylation is stable along follow-up and independent of most clinical variables, PA subtype, proliferation, and without prognostic value.

TERT promoter mutations and telomere length in adult malignant gliomas and recurrences

In this report on 303 gliomas we show the highest frequency of TERT promoter mutations in gliobastomas (80%) followed by oligodendrogliomas (70%) and astrocytomas (39%). We observed positive association between TERT promoter and IDH mutations in oligodendroglial tumors (OR = 26.3; 95% CI 2.5-250.2) and inverse association in primary glioblastomas (OR = 0.13; 95% CI 0.03-0.58). Tumors with TERT promoter mutations compared to those without showed increased TERT transcription; we also showed difference in the transcription levels due to the two main mutations. Tumors with TERT promoter mutations had shorter telomeres than those without. The patients with only TERT promoter mutations showed worst survival (median survival 14.6 months) and patients with both IDH and TERT promoter mutations showed best survival (246.5 months). In patients with astrocytoma, the TERT promoter mutations only associated with poor survival (P < 0.0001); IDH mutations and 1p/19q deletions associated with increased survival (P = 0.0004). TERT promoter mutations in low grade gliomas associated with reduced progression free survival (HR 10.2; 95% CI 1.9 - 55.9). While our data affirm the role of TERT promoter mutations in glial tumors, effects on transcription and telomere length emphasise the importance of telomere biology in disease genesis and outcome.

Prognostic quality of activating TERT promoter mutations in glioblastoma: interaction with the rs2853669 polymorphism and patient age at diagnosis

BACKGROUND

Expression of the telomerase reverse transcriptase (TERT) might be altered by activating mutations of the rs2853669 polymorphism within the promoter region. Here we investigate the impact of these genomic alterations on telomerase activation and dissect their prognostic potential in glioblastoma (GBM).

METHODS

The respective TERT promoter region was sequenced in 126 GBM tissues and compared with clinical parameters and glioma biomarkers MGMT promoter methylation and IDH1 mutation. TERT mRNA expression, telomerase activity, and telomere lengths were determined by reverse transcriptase PCR, TRAP assay, and real-time PCR, respectively.

RESULTS

Seventy-three percent of GBM patients harbored TERT promoter mutations associated with enhanced telomerase activity and TERT mRNA expression but reduced telomere lengths (P < .001 for all). Patients with mutated tumors exhibited significantly shorter overall survival in the entire cohort (11.5 vs 23.1 months; P < .0001) and in the primary GBM patient subgroup lacking IDH1 mutations (n = 120; P = .0084). This prognostic impact was confined to younger patients (aged <65 years), while the negative prognostic power of enhanced age at diagnosis was limited to those patients lacking TERT promoter mutations. Presence of the common single nucleotide polymorphism rs2853669, disrupting an endogenous Ets2 transcription factor-binding site, was associated with improved survival exclusively in patients with a wild-type TERT promoter. On the contrary, the shortest mean overall survival was detected in those patients harboring both an activating TERT promoter mutation and homozygous rs2853669 alleles.

CONCLUSION

In summary, TERT promoter mutations are powerful prognosticators for worse course of disease in human GBM patients but their prognostic value is influenced by the rs2853669 polymorphism and age at diagnosis.