TERT Polymorphism rs2853669 Influences on Lung Cancer Risk in the Korean Population

Atypical Case of Highly Mutated h-TERT Promoter in Germline Genome from Buccal Mucosa Cancer

Buccal mucosa cancer has an aggressive nature as it rapidly grows and penetrates with high recurrence rate. Strikingly, carcinoma of buccal mucosa is the most common cancer of oral cavity in India. Recently, telomerase and telomere biology have been implicated in the pathogenesis and progression in various cancers via regulation of telomere maintenance by telomerase expression which is controlled by telomerase reverse transcriptase (TERT) promoter. Strikingly, h-TERT promoter mutations have been incriminated in regulation of telomerase gene expression. Here, we present a 35 years old male with intense coughing, short breathlessness and fever since 15 days, was admitted to the pulmonary unit. He was a chronic smoker and gutka user. The cytopathological analysis of gastric aspirate revealed buccal mucosa carcinoma of IV stage. We identified h-TERT promoter mutations in isolated genomic DNA from whole blood using DNA sequencer. Genetic analysis disclosed that h-TERT promoter region was highly mutated in this patient. Identified mutations include C.-248 del G, C.-272 del G, C.-279 del G, C.-331 del G, C.-349 del G, C.-351 del C, C.-360 G > A, C.-362 T > A, C.-371 del T and C.-372 del T. Further, all identified mutations were subjected to predict the pathologic functional consequences using bioinformatics tools viz TFsitescan and CiiiDER which showed either loss or gain of transcription factors binding sites in h-TERT promoter. This is a unique case in which total 9 mutations were observed in h-TERT promoter in a single case. In conclusion, all together these mutations in h-TERT promoter may alter the epigenetics and subsequently the tenacity of binding transcription factors which are of functional significance.

Identification of h-TERT Promoter Mutations in Germline DNA from North Indian Lung Carcinoma Patients

Lung cancer is a severe and the leading cause of cancer related deaths worldwide. The recurrent h-TERT promoter mutations have been implicated in various cancer types. Thus, the present study is extended to analyze h-TERT promoter mutations from the North Indian lung carcinoma patients. Total 20 histopathologically and clinically confirmed cases of lung cancer were enrolled in this study. The genomic DNA was extracted from venous blood and subjected to amplification using appropriate h-TERT promoter primers. Amplified PCR products were subjected for DNA Sanger sequencing for the identification of novel h-TERT mutations. Further, these identified h-TERT promoter mutations were analysed for the prediction of pathophysiological consequences using bioinformatics tools such as Tfsitescan and CIIDER. The average age of patients was 45 ± 8 years which was categorized in early onset of lung cancer with predominance of male patients by 5.6 fold. Interestingly, h-TERT promoter mutations were observed highly frequent in lung cancer. Identified mutations include c. G272A, c. T122A, c. C150A, c. 123 del C, c. C123T, c. G105A, c. 107 Ins A, c. 276 del C corresponding to -168 G>A, -18 T>A, -46 C>A, -19 del C, -19 C>T, -1 G>A, -3 Ins A, -172 del C respectively from the translation start site in the promoter of the telomerase reverse transcriptase gene which are the first time reported in germline genome from lung cancer. Strikingly, c. -18 T>A [C.T122A] was found the most prevalent variant with 75% frequency. Notwithstanding, other mutations viz c. -G168A [c. G272A] and c. -1 G>A [c. G105A] were found to be at 35% and 15% frequency respectively whilst the rest of the mutations were present at 10% and 5% frequency. Additionally, bioinformatics analysis revealed that these mutations can lead to either loss or gain of various transcription factor binding sites in the h-TERT promoter region. Henceforth, these mutations may play a pivotal role in h-TERT gene expression. Taken together, these identified novel promoter mutations may alter the epigenetics and subsequently various transcription factor binding sites which are of great functional significance. Thereby, it is plausible that these germline mutations may involve either as predisposing factor or direct participation in the pathophysiology of lung cancer through entangled molecular mechanisms.

Human TERT promoter polymorphism rs2853669 is associated with cancers: an updated meta-analysis

The polymorphism rs2853669 in the telomerase reverse transcriptase gene (TERT) promoter region is widely investigated for the risk of different cancers. However, previous results remained inconclusive. Thus, we performed this updated meta-analysis to comprehensively evaluate the association between rs2853669 and the susceptibility of human cancer. A systematic literature search via PubMed, EMBASE, Cochrane Library, and Web of Science databases was conducted that produced a total of 19 eligible studies containing 23,085 subjects. The relationship was calculated with the odds ratio (OR) and 95% confidence intervals (CIs). Statistical analyses were performed using the RevMan 5.4 software. The analysis indicated that rs2853669 is associated with an enhanced risk of overall cancer risk. From subgroup analysis, a significantly increased association in five genetic models (p < 0.05) was found among Asians, but no association was observed in Caucasians. Although we did not find any significant correlation between rs2853669 and breast cancer, an increased and statistically significant association was found for both lung cancer and acute myeloid leukemia. We did not find any association in other cancer types during stratified analysis. Our meta-analysis suggests that rs2853669 polymorphism in TERT gene is associated with an increased risk of overall cancer susceptibility, particularly in the Asian population. Moreover, rs2853669 is significantly associated with lung cancer and acute myeloid lymphoma. However, large-scale studies are needed to confirm our findings.

Regulatory Single Nucleotide Polymorphism Increases TERT Promoter Activity in Thyroid Carcinoma Cells

BACKGROUND/AIM

The telomerase reverse transcriptase (TERT) promoter has a regulatory single nucleotide polymorphism (rSNP), rs2853669, and occasionally shows point mutations C228T and C250T. Although C228T and C250T have been well examined to increase TERT promoter activity and are known as risk factors for thyroid carcinoma, the significance of rs2853669 has not been well investigated. This study aimed to clarify the influence of rs2853669 on TERT promoter activity in thyroid carcinoma cells.

MATERIALS

Seven of 8 examined thyroid cell lines had rs2853669, 5 had C228T, and 1 had C250T.

RESULTS

Three papillary thyroid carcinoma cell lines, harboring both rs2853669 and C228T, showed higher TERT mRNA expression on real-time PCR than the other cell lines. Anaplastic thyroid carcinoma cell lines, in contrast, showed variable TERT mRNA expression depending on the combination of rs2853669, C228T, and C250T. Luciferase assays, performed to compare the influences of rs2853669, C228T, and C250T on TERT promoter activity in thyroid carcinoma, showed that rs2853669, as well as C228T, increased the promoter activity, and the combination of rs2853669 and C228T increased the promoter activity even more strongly than C228T alone.

CONCLUSION

We conclude that the presence of rs2853669 within the TERT promoter could be as significant as the C228T mutation in thyroid carcinoma.

TERT-Regulation and Roles in Cancer Formation

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

Association of strong risk of hTERT gene polymorphic variants to malignant glioma and its prognostic implications with respect to different histological types and survival of glioma cases

BACKGROUND

Germline genetic variants of human telomerase reverse transcriptase (hTERT) are known to predispose for various malignancies, including glioma. The present study investigated genetic variation of hTERT T/G (rs2736100) and hTERT G/A (rs2736098) with respect to glioma risk.

METHODS

Confirmed cases (n = 106) were tested against 210 cancer-free healthy controls by the polymerase chain reaction-restriction fragment length polymorphism technique for genotyping.

RESULTS

Homozygous variant 'GG' genotype of rs2736100 frequency was > 4-fold significantly different in cases versus controls (39.6% 17.2%; p < 0.0001). Furthermore, variant 'G' allele was found to be significantly associated with cases (0.5 versus 0.2 in controls; p < 0.0001). Homozygous variant rs2736098 'AA' genotype (35.8% versus 23.8%) and allele 'A' (0.49 versus 0.34) showed a marked significant difference in cases and controls, respectively (p < 0.05). In hTERT rs2736100, the GG genotype significantly presented more in higher grades and GBM (p < 0.0001). Furthermore, the GG variant of hTERT rs2736100 had a poor probability with respect to the overall survival of patients compared to TG and TT genotypes (log rank p = 0.03). Interestingly, two haplotypes of hTERT rs2736100/rs2736098 were identified as GG and GA that conferred a > 3- and 5-fold risk to glioma patients respectively, where variant G/A haplotype was observed to have the highest impact with respect to glioma risk (p < 0.0001).

CONCLUSIONS

The results of the present study indicate that hTERT rs2736098 and rs2736100 variants play an important role in conferring a strong risk of developing glioma. Furthermore, hTERT rs2736100 GG variant appears to play a role in the bad prognosis of glioma patients. Haplotypes GG and GA could prove to be vital tools for monitoring risk in glioma patients.

Association of TERT, OGG1, and CHRNA5 Polymorphisms and the Predisposition to Lung Cancer in Eastern Algeria

Lung cancer remains the most common cancer in the world. The genetic polymorphisms (rs2853669 in TERT, rs1052133 in OGG1, and rs16969968 in CHRNA5 genes) were shown to be strongly associated with the risk of lung cancer. Our study's aim is to elucidate whether these polymorphisms predispose Eastern Algerian population to non-small-cell lung cancer (NSCLC). To date, no study has considered this association in the Algerian population. This study included 211 healthy individuals and 144 NSCLC cases. Genotyping was performed using TaqMan probes and Sanger sequencing, and the data were analyzed using multivariate logistic regression adjusted for covariates. The minor allele frequencies (MAFs) of TERT rs2853669, CHRNA5 rs16969968, and OGG1 rs1052133 polymorphisms in controls were C: 20%, A: 31%, and G: 29%, respectively. Of the three polymorphisms, none shows a significant association, but stratified analysis rs16969968 showed that persons carrying the AA genotype are significantly associated with adenocarcinoma risk (pAdj = 0.03, ORAdj = 2.55). Smokers with an AA allele have a larger risk of lung cancer than smokers with GG or GA genotype (pAdj = 0.03, ORAdj = 3.91), which is not the case of nonsmokers. Our study suggests that CHRNA5 rs16969968 polymorphism is associated with a significant increase of lung adenocarcinoma risk and with a nicotinic addiction.

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.

Clinicopathological significance of the single nucleotide polymorphism, rs2853669 within the TERT promoter in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy. Point mutations in the telomerase reverse transcriptase (TERT) promoter, C228T and C250T and oncogene BRAF^V600E have been investigated as risk factors for PTC. However, little research has been done on the single nucleotide polymorphism rs2853669 in the TERT promoter in PTC. This study aimed to clarify the clinicopathological significance of rs2853669 in Japanese patients with PTC. The genetic frequencies of rs2853669, C228T, C250T and BRAF^V600E were investigated in 58 patients with PTC and compared with the clinicopathological parameters of PTC. rs2853669, C228T, C250T and BRAF^V600E were found in 58.6%, 17.2%, 5.2% and 37.0% of the PTC patients, respectively. PTC with rs2853669 and C228T were associated only with tumor sizes larger than 2.0 cm (P < 0.05). Furthermore, the coexistence of rs2853669 and C228T was strongly associated with tumor size (P < 0.01), with an odds ratio of 6.4 (P < 0.05). We showed that rs2853669, as well as C228T, may be a risk factor for the aggressiveness of PTC, and the coexistence of these mutations might represent greater risk.

Effect of single-nucleotide polymorphism in TERT promoter on follicular thyroid tumor development

Follicular thyroid neoplasm is a common tumor, and consists of follicular thyroid adenoma (FTA) and carcinoma (FTC). The mechanisms of tumor development of FTA and FTC are not well-understood. Single-nucleotide polymorphisms (SNPs) and point mutations in the telomerase reverse transcriptase (TERT) promoter have been associated with tumor development of many cancers. In order to clarify the significance of TERT promoter SNPs and mutations, including rs2853669 (-245T>C), C228T, and C250T, we analyzed 59 FTA patients and 19 FTC patients. Rs2853669 was found in 67.8% (40/59) and 57.9% (11/19) of FTAs and FTCs, respectively, and homozygous rs2853669 (CC) was more frequently found in FTC than in FTA. Furthermore, in FTA, rs2853669 was significantly associated with tumor size greater than 2.0 cm (P < 0.05). C228T was found in 5.1% and 36.8% of FTAs and FTCs, respectively. Frequencies of rs2853669 or/and C228T mutation were 71.2% in FTAs and 73.7%, in FTCs, and were significantly associated with larger tumor sizes in FTAs (P < 0.05). Rs2853669 is considered to be associated with tumor development in FTA and FTC.

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.

Characterization of melanoma susceptibility genes in high-risk patients from Central Italy

Genetic susceptibility to cutaneous melanoma has been investigated in Italian high-risk melanoma patients from different geographical regions. CDKN2A, CDK4, and MC1R genes have been screened in most studies, MITF and POT1 were screened in only one study, and none analyzed the TERT promoter. We carried out a mutational analysis of CDKN2A, CDK4 exon 2, POT1 p.S270N, MITF exon 10, MC1R, and the TERT promoter in 106 high-risk patients with familial melanoma (FM) and sporadic multiple primary melanoma (spMPM) from Central Italy and evaluated mutations according to the clinicopathological characteristics of patients and lesions. In FM, CDKN2A mutations were detected in 8.3% of the families, including one undescribed exon 1β mutation (p.T31M), and their prevalence increased with the number of affected relatives within the family. MC1R variants were identified in 65% of the patients and the TERT rs2853669 promoter polymorphism was identified in 58% of the patients. A novel synonymous mutation detected in MITF exon 10 (c.861A>G, p.E287E), although predicted as a splice site mutation by computational tools, could not functionally be confirmed to alter splicing. For spMPM, 3% carried CDKN2A mutations, 79% carried MC1R variants, and 47% carried the TERT rs2853669 promoter polymorphism. MC1R variants were associated with fair skin type and light hair color both in FM and in spMPM, and with a reduction of age at diagnosis in FM patients. Mutations in CDK4 exon 2 and the POT1 p.S270N mutation were not detected. A low frequency of CDKN2A mutations and a high prevalence of MC1R variants characterize high-risk melanoma patients from Central Italy.

TERT rs2736098 (Ex2-659G>A) polymorphism and cancer susceptibility: evidence from a comprehensive meta-analysis

Increasing researches have been performed regarding the relationship between TERT rs2736098 and cancer risk, but no consensus has been reached about the relationship. Here, we conducted this updated meta-analysis, aiming to comprehensively evaluate the role of TERT rs2736098 in cancer risk. We systematically searched potential relevant articles through PubMed, EMBASE, CNKI, and WanFang database before August 2017. A total of 33 studies with 18685 cases and 23820 controls were finally included in the current meta-analysis. We then adopted odds ratios (ORs) and 95% confidence intervals (CIs) to analyze the contributions of TERT rs2736098 to cancer risk. We found that the TERT rs2736098 polymorphism was associated with risk of cancer in overall analysis (AA vs. GG: OR = 1.26, 95% CI = 1.09–1.47; AA vs. AG/GG: OR = 1.22, 95% CI = 1.09–1.36; AA/AG vs. GG: OR = 1.13, 95% CI = 1.02–1.24; A vs. G: OR = 1.11, 95% CI = 1.04–1.20). Furthermore, in analysis stratified by cancer type, ethnicity, control source, quality score, and Hardy-Weinberg equilibrium (HWE) in controls, we found increased risk of cancer among lung cancer, bladder cancer, breast cancer, colorectal cancer, other cancers, Asians, hospital-based subgroup, score > 9 group, as well as controls agreement with HWE group. Despite some limitations, the current meta-analysis represented the largest and the most comprehensive investigations, with the strongest conclusion than ever before. To further explicit the association between TERT rs2736098 and cancer risk, more well-design case-control studies with larger sample size are warranted in the future.

Polymorphisms in human telomerase reverse transcriptase (hTERT) gene, gene- gene and gene-smoking interaction with susceptibility to gastric cancer in Chinese Han population

Aims

To investigate the association of telomerase reverse transcriptase (TERT) gene polymorphisms and additional gene-gene and gene- environment interaction with gastric cancer (GC) risk.

Results

GC risk was significantly higher in carriers of G allele of rs2736100 than those with TT genotype (TG+ GG versus TT), adjusted OR (95%CI) =1.68 (1.26-2.17), and higher in carriers of G allele of rs2853669 than those with AA genotype (AG+ GG versus AA), adjusted OR (95%CI) = 1.72 (1.19-2.33). We also found that interaction between rs2736100 and smoking was associated with higher GC risk. Smokers with TG or GG of rs2736100 genotype have elevated GC risk, compared to never- smokers with TT of rs2736100 genotype, OR (95%CI) = 3.12 (1.82 -4.61). Pairwise linkage equilibrium (LD) analysis between SNPs was measured and the D’ value between rs2736100 and rs2736109 was more than 0.8. A haplotype containing the rs2736100- G and rs2736109- A alleles was associated with a statistically increased GC risk (OR= 2.66, 95%CI= 1.28 – 4.12, p<0.0001).

Materials and Methods

A total of 1088 participants (686 males, 402 females) were selected, including 360 GC patients and 728 normal participants. Logistic regression was performed to investigate association between single nucleotide polymorphisms (SNPs) within TERT gene and GC susceptibility. Generalized multifactor dimensionality reduction (GMDR) model was used to screen gene- gene and gene- environment interaction combinations.

Conclusions

We found that G allele of rs2736100 and G allele of rs2853669 in TERT gene, interaction between rs2736100 and smoking, and haplotype containing the rs2736100- G and rs2736109- A alleles were all associated with increased GC risk.

Mutation of the TERT promoter leads to poor prognosis of patients with non-small cell lung cancer

Mutations in the promoter region of telomerase reverse transcriptase (TERT) and alterations in telomere length (TL) have been the focus of research in various types of cancer. In the present study, the frequency and clinical characteristics of TERT promoter mutations and TL were studied in non-small cell lung cancers (NSCLC). TERT promoter mutations and TL were analyzed in 188 patients using DNA sequencing and the reverse transcription-quantitative polymerase chain reaction, respectively. The TERT promoter mutation rate was observed to be 2.2% (4/188 NSCLC cases), and it was significantly associated with regional lymph node invasion (P<0.001). No significant difference in TL was observed between the patients with and without TERT promoter mutations. TL was decreased in males (P=0.058 vs. females) and smokers (P=0.008 vs. non-smokers). Survival analyses demonstrated poor prognoses for patients with NSCLC with TERT promoter mutations (P<0.001). Multivariate survival analyses demonstrated that TERT promoter mutations were an independent prognostic marker for poor overall survival (P=0.045). The results of the present study demonstrated that TERT promoter mutation was not frequent in NSCLC; however, it may have value as a prognostic marker in NSCLC.

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.

Skin phenotypes can offer some insight about the association between telomere length and cancer susceptibility

The role of telomere biology in cancer has been studied for a wide variety of different cancers but the association with telomere length has been controversial. This is because some cancers have been found to be associated with longer telomeres in circulating white cells whilst other cancer types are more common in individuals with shorter telomeres. Hence, there has been some skepticism as to whether telomere length may be helpful in estimating cancer risk. For melanoma, however, results have been fairly consistent showing that longer telomeres are associated with an increased risk. This link was first discovered because of a link between longer telomeres and a high number of naevi. In contrast, for cutaneous squamous cell carcinomas, the relationship is reversed with higher risk in individuals with shorter telomeres. Differences in skin phenotypes with the presence of high number of naevi versus photoageing with solar elastosis and solar keratoses have already been valuable for dermatologists as the former phenotype is associated with melanoma whilst the latter is more common in patients with squamous cell carcinoma of the skin. The hypothesis is that the differences in cutaneous phenotypes already observed by dermatologists for skin cancers may, in fact, be useful as well for cancer prediction in general as it may reflect underlying telomere biology. This manuscript will address the evidence for links between telomere biology, skin phenotypes and cancer risk.

Understanding TERT Promoter Mutations: A Common Path to Immortality

Telomerase (TERT) activation is a fundamental step in tumorigenesis. By maintaining telomere length, telomerase relieves a main barrier on cellular lifespan, enabling limitless proliferation driven by oncogenes. The recently discovered, highly recurrent mutations in the promoter of TERT are found in over 50 cancer types, and are the most common mutation in many cancers. Transcriptional activation of TERT, via promoter mutation or other mechanisms, is the rate-limiting step in production of active telomerase. Although TERT is expressed in stem cells, it is naturally silenced upon differentiation. Thus, the presence of TERT promoter mutations may shed light on whether a particular tumor arose from a stem cell or more differentiated cell type. It is becoming clear that TERT mutations occur early during cellular transformation, and activate the TERT promoter by recruiting transcription factors that do not normally regulate TERT gene expression. This review highlights the fundamental and widespread role of TERT promoter mutations in tumorigenesis, including recent progress on their mechanism of transcriptional activation. These somatic promoter mutations, along with germline variation in the TERT locus also appear to have significant value as biomarkers of patient outcome. Understanding the precise molecular mechanism of TERT activation by promoter mutation and germline variation may inspire novel cancer cell-specific targeted therapies for a large number of cancer patients.

Polymorphisms in human telomerase reverse transcriptase (hTERT) gene and susceptibility to gastric cancer in a Turkish population: Hospital-based case-control study

Erosion of telomeres, tandem nucleotide repeats (TTAGGG)n that cap the end of eukaryotic chromosomes, has been related with carcinogenesis. The human telomerase reverse transcriptase (hTERT) gene is encoded the rate-limiting catalytic subunit of the telomerase complexes, which is essential for the protection of telomeric DNA length and chromosomal stability. The purpose of this study was to examine the effect of four functional single nucleotide polymorphisms (SNPs) of hTERT (rs2736109 G>A, rs2735940 T>C, rs2853669 A>G and rs2736100 T>G) on susceptibility to gastric cancer (GC) in Turkish population. The genotype frequency of hTERT rs2736109 G>A, rs2735940 T>C, rs2853669 A>G and rs2736100 T>G polymorphisms were determined by using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and TaqMan methods in 104 subjects with GC and 209 healthy control subjects. We found that hTERT rs2736109 G>A (AA+AG vs. GG OR=1.68 95% CI=1.01-2.81, P=0.04), rs2735940 T>C (CC vs. CT+TT: OR=2.53 95% CI=1.01-6.13, P=0.03), and rs2736100 T>G (TT vs. TG+GG: OR=2.27 95% CI=1.23-4.17, P=0.006) polymorphisms were associated with risk of GC. In the haplotype analysis, hTERT Grs2736109/Trs2735940/Ars2853669/Grs2736100 haplotype was also related with an increased risk of GC (OR=1.75; 95% CI: 1.05-2.93, P=0.03). Because this is the first study regarding the hTERT rs2736109 G>A, rs2735940 T>C, rs2853669 A>G and rs2736100 T>G polymorphisms and the risk of GC susceptibility in the literature, further independent studies are needed to verify our results in a larger sample sizes, as well as in patients of different populations.

TERT promoter mutations in melanoma survival

Despite advances in targeted therapies, the treatment of advanced melanoma remains an exercise in disease management, hence a need for biomarkers for identification of at-risk primary melanoma patients. In this study, we aimed to assess the prognostic value of TERT promoter mutations in primary melanomas. Tumors from 300 patients with stage I/II melanoma were sequenced for TERT promoter and BRAF/NRAS mutations. Cumulative curves were drawn for patients with and without mutations with progression-free and melanoma-specific survival as outcomes. Cox proportional hazard regression models were used to determine the effect of the mutations on survivals. Individually, presence of TERT promoter and BRAF/NRAS mutations associated with poor disease-free and melanoma-specific survival with modification of the effect by the rs2853669 polymorphism within the TERT promoter. Hazard ratio (HR) for simultaneous occurrence of TERT promoter and BRAF/NRAS mutations for disease-free survival was 2.3 (95% CI 1.2-4.4) and for melanoma-specific survival 5.8 (95% CI 1.9-18.3). The effect of the mutations on melanoma-specific survival in noncarriers of variant allele of the polymorphism was significant (HR 4.5, 95% CI 1.4-15.2) but could not be calculated for the carriers due to low number of events. The variant allele per se showed association with increased survival (HR 0.3, 95% CI 0.1-0.9). The data in this study provide preliminary evidence that TERT promoter mutations in combination with BRAF/NRAS mutations can be used to identify patients at risk of aggressive disease and the possibility of refinement of the classification with inclusion of the rs2853669 polymorphism within TERT promoter.