A functional variant of tandem repeats in human telomerase gene was associated with survival of patients with early stages of non-small cell lung cancer

Blood-Derived Exosomal hTERT mRNA in Patients with Lung Cancer: Characterization and Correlation with Response to Therapy

Background: Telomerase (human telomerase reverse transcriptase (hTERT) is considered a hallmark of cancer, being active in cancer cells but repressed in human somatic cells. As such, it has the potential to serve as a valid cancer biomarker. Exosomal hTERT mRNA can be detected in the serum of patients with solid malignancies but not in healthy individuals. We sought to evaluate the feasibility of measuring serum exosomal hTERT transcripts levels in patients with lung cancer. Methods: A prospective analysis of exosomal hTERT mRNA levels was determined in serum-derived exosomes from 76 patients with stage III-IV lung cancer (11 SCLC and 65 NSCLC). An hTERT level above RQ = 1.2 was considered "detectable" according to a previous receiver operating characteristic curve (ROC) curve. Sequential measurements were obtained in 33 patients. Demographic and clinical data were collected retrospectively from patients' charts. Data on response to systemic therapy (chemotherapy, immunotherapy, and tyrosine kinase inhibitors) were collected by the treating physicians. Results: hTERT was detected in 53% (40/76) of patients with lung cancer (89% of SCLC and 46% of NSLCC). The mean hTERT levels were 3.7 in all 76 patients, 5.87 in SCLC patients, and 3.62 in NSCLC patients. In total, 25 of 43 patients with sequential measurements had detectable levels of hTERT. The sequential exosomal hTERT mRNA levels reflected the clinical course in 23 of them. Decreases in hTERT levels were detected in 17 and 5 patients with partial and complete response, respectively. Eleven patients with a progressive disease had an increase in the level of exosomal hTERT, and seven with stable disease presented increases in its exosomal levels. Another patient who progressed on the first line of treatment and had a partial response to the second line of treatment exhibited an increase in exosomal hTERT mRNA levels during the progression and a decrease during the response. Conclusions: Exosomal hTERT mRNA levels are elevated in over half of patients with lung cancer. The potential association between hTERT levels and response to therapy suggests its utility as a promising cancer biomarker for response to therapy. This issue should be further explored in future studies.

Analysis of MNS16A VNTR polymorphic sequence variations of the TERT gene and associated risk for development of bladder cancer

Background:

The MNS16A variable number tandem repeat (VNTR) polymorphism of the human telomerase reverse transcriptase (hTERT) gene acts as a regulator of hTERT promoter activity and has been shown to have a role in the predisposition toward various cancers. The current study aimed to investigate the association between MNS16A VNTR alleles and genetic predisposition to bladder cancer in the Kashmir region of northern India.

Materials and methods:

A total of 130 patients with bladder cancer and 170 age- and gender-matched healthy controls were included in this study. Primer-specific polymerase chain reaction was used to genotype the different variants of VNTR alleles of the MNS16A VNTR polymorphism.

Results:

Short allele VNTR-243 (SS) genotype frequency significantly differed between cases (9.23%) and controls (3.52%) (OR = 3.08 [95% CI = 1.10–8.61], p = 0.042). The VNTR-243 short allele (S) was found significantly more frequent in bladder cancer cases (28.46%) than controls (20.88%) (OR = 1.50 [95% CI = 1.03–2.19], p = 0.034). Likewise, the long allele (LL) hTERT MNS16A genotype was distributed more frequently in low stage disease versus high stage disease (60.29% vs. 39.70%) (OR = 0.79 [95% CI = 0.39–1.60], p = 0.595).

Conclusion:

The MNS16A VNTR short allele (S) was associated with a higher risk for bladder cancer in our population as compared to long alleles.

The MNS16A VNTR polymorphism of the TERT gene in bladder cancer

OBJECTIVE

Bladder cancer (BC) is a complex disease that has a high morbidity rate. The MNS16A polymorphism in the TERT gene has been indicated to play a role in the presence of various cancer types and multiple tumor populations. In the present study, our goal was to investigate whether the MNS16A (VNTRs) in the TERT gene was associated with bladder cancer.

MATERIAL AND METHODS

A total of 70 patients with BC and 120 normal controls were included in the study. The MNS16A (VNTRs) in the TERT gene was amplified using polymerase chain reaction (PCR). The PCR products were visualized on 3% high resolution agarose gel and under a UV light.

RESULTS

The MNS16A VNTR-302 allele was found to be the most common allele in both, the patient group (64%) and the control group (62%). The second most common allele was the VNTR-243 allele that occurred at a frequency of around 34% in BC patients and 33% in the controls. VNTR-333 (patient group, 1%; control group, 3%) and VNTR-274 (patient group, 2%; control group, 1%) alleles were reported as the least common alleles in this study.

CONCLUSION

When comparing the frequencies of genetic variants between cases and controls, we observed that our findings did not support the hypothesis that the MNS16A VNTR polymorphism of the TERT gene might regulate cancer susceptibility.

Leukocyte Telomere Length Shortening, hTERT Genetic Polymorphisms and Risk of Childhood Acute Lymphoblastic Leukemia

Background: Telomeres are involved in chromosomal stability, cellular immortality and tumorigenesis. Human telomerase reverse transcriptase (TERT) is essential for the maintenance of telomere DNA length. Recently, a variable tandem-repeats polymorphism, MNS16A, located in the downstream region of the TERT gene, was reported to have an effect on TERT expression and telomerase activity. Previous studies have linked both relative telomere length (RTL) and TERT variants with cancer. Therefore, we evaluated associations between RTL, TERT gene polymorphisms (hTERT, rs2735940 C/T and MNS16A Ins/Del) and risk of childhood acute lymphoblastic leukemia (ALL) in an Iranian population. Methods: RTL was determined by a multiplex quantitative PCR-based method, and variants of the hTERT, rs2735940 C/T and MNS16A Ins/Del, were genotyped by amplification refractory mutation system PCR (ARMS-PCR), and PCR, respectively. Results: Our results indicated that RTL was shorter in ALL patients (1.53±0.12) compared to the control group (2.04±0.19) (P=0.029). However, no associations between hTERT gene variants or haplotypes and the risk of childhood ALL were observed (P>0.05). Also hTERT polymorphisms were not associated with RTL or patient clinicopathological characteristics, including age (P=0.304), sex (P=0.061) organomegally (P=0.212) CSF involvement (P=0.966) or response to treatment (P=0.58). Conclusions: We found that telomere attrition may be related to the pathogenesis of childhood ALL, irrespective to TERT variants.

MNS16A tandem repeat minisatellite of human telomerase gene: functional studies in colorectal, lung and prostate cancer

MNS16A, a functional polymorphic tandem repeat minisatellite, is located in the promoter region of an antisense transcript of the human telomerase reverse transcriptase gene. MNS16A promoter activity depends on the variable number of tandem repeats (VNTR) presenting varying numbers of transcription factor binding sites for GATA binding protein 1. Although MNS16A has been investigated in multiple cancer epidemiology studies with incongruent findings, functional data of only two VNTRs (VNTR-243 and VNTR-302) were available thus far, linking the shorter VNTR to higher promoter activity.

For the first time, we investigated promoter activity of all six VNTRs of MNS16A in cell lines of colorectal, lung and prostate cancer using Luciferase reporter assay. In all investigated cell lines shorter VNTRs showed higher promoter activity. While this anticipated indirect linear relationship was affirmed for colorectal cancer SW480 (P = 0.006), a piecewise linear regression model provided significantly better model fit in lung cancer A-427 (P = 6.9 × 10⁻⁹) and prostate cancer LNCaP (P = 0.039). In silico search for transcription factor binding sites in MNS16A core repeat element suggested a higher degree of complexity involving X-box binding protein 1, general transcription factor II–I, and glucocorticoid receptor alpha in addition to GATA binding protein 1.

Further functional studies in additional cancers are requested to extend our knowledge of MNS16A functionality uncovering potential cancer type-specific differences. Risk alleles may vary in different malignancies and their determination in vitro could be relevant for interpretation of genotype data.

Common variants of human TERT and TERC genes and susceptibility to sporadic Alzheimers disease

Studies investigating telomere length in association with cognitive decline, dementia, and sporadic Alzheimer's disease (AD) have frequently found shorter telomeres to be associated with the development of AD and telomerase expression with pathological processes in AD. Human telomerase is constituted by two components: the telomerase reverse transcriptase (TERT) and the telomerase RNA component (TERC). Genetic variation at the two loci has been investigated in relation to telomere length, longevity, and common diseases of advanced age, but not in relation to AD. We examined three polymorphisms of the TERT gene (VNTR MNS16A, rs2853691, rs33954691) and three polymorphisms of the TERC gene (rs12696304, rs3772190, rs16847897) in a sample of 220 AD patients and 146 controls. MNS16A LL genotype was found to be associated with an increased risk of AD only in males [interaction term adjusted OR=3.55 (95% CI 1.2-10.2)]. The three TERC single nucleotide polymorphisms are in strict linkage disequilibrium and their genotype combinations influenced the age at AD onset (AAO). The combined genotype GG-TT-CC was associated with a mean AAO six years lower (70.5±6.7) than that associated with the other genotype combinations (76.04±6.7, p=0.01). The fact that the MNS16 L allele has been reported to lower TERT expression, and that the TERC alleles G, T, C (rs12696304, rs3772190, rs16847897 in this order have been repeatedly found associated with shorter LTL, seems to corroborate the hypothesis of a role of telomere length and telomerase in AD susceptibility.

PTEN Inhibits Cell Proliferation, Promotes Cell Apoptosis, and Induces Cell Cycle Arrest via Downregulating the PI3K/AKT/hTERT Pathway in Lung Adenocarcinoma A549 Cells

PTEN plays an essential role in tumorigenesis and both its mutation and inactivation can influence proliferation, apoptosis, and cell cycle progression in tumor cells. However, the precise role of PTEN in lung cancer cells has not been well studied. To address this, we have generated lung adenocarcinoma A549 cells overexpressing wild-type or mutant PTEN as well as A549 cells expressing a siRNA directed toward endogenous PTEN. Overexpression of wild-type PTEN profoundly inhibited cell proliferation, promoted cell apoptosis, caused cell cycle arrest at G1, downregulated p-AKT, and decreased expression of the telomerase protein hTERT. In contrast, in cells expressing a PTEN directed siRNA, the opposite effects on cell proliferation, apoptosis, cell cycle arrest, p-AKT levels, and hTERT protein expression were observed. A549 cells transfected with a PTEN mutant lacking phosphatase activity (PTEN-C124A) or an empty vector (null) did not show any effect. Furthermore, using the PI3K/AKT pathway blocker LY294002, we confirmed that the PI3K/AKT pathway was involved in mediating these effects of PTEN. Taken together, we have demonstrated that PTEN downregulates the PI3K/AKT/hTERT pathway, thereby suppressing the growth of lung adenocarcinoma cells. Our study may provide evidence for a promising therapeutic target for the treatment of lung adenocarcinoma.

The MNS16A polymorphism in the TERT gene in peri-centenarians from the Han Chinese population

MNS16A, a variable number of tandem repeats polymorphism in the TERT gene, has been suggested to regulate telomerase activity. As telomerase activity has been reported to be related to life-span, we hypothesized that this polymorphism might affect human longevity by controlling the length of the telomere. To test this hypothesis, we collected 446 unrelated pericentenarian individuals (age[Symbol: see text]90, mean 94.45±3.45 years) and 332 normal controls (age 22-53, mean 35.0±12.0 years) from Dujiangyan, Sichuan, China. We typed the MNS16A polymorphism in both groups, and compared the allele and genotype frequencies between the peri-centenarian and control groups using the chi-squared test. There was no significant difference between the peri-centenarian and control groups. Thus, the MNS16A polymorphism in TERT might not influence human life-span, at least in the Han Chinese population studied here.

MNS16A tandem repeat minisatellite of human telomerase gene and prostate cancer susceptibility

Telomere dysfunction is an early event in the development of prostate cancer and telomerase (TERT) activity is detectable in the majority of prostate cancers. Genetic variation in TERT and its regulatory elements may influence prostate carcinogenesis. MNS16A, a functional polymorphic tandem repeat minisatellite of TERT, has been studied in several malignancies. We determined MNS16A genotypes in an Austrian case-control study for the first time in the context of prostate cancer, comprising 1165 prostate cancer cases and 674 benign prostate hyperplasia controls with PCR. In addition to the five reported variable number of tandem repeats (VNTRs), we identified VNTR-212, a rare variant, for the first time in a European population. Multiple logistic regression analysis revealed no differences in genotype distribution between cases and controls. However, in stratified analysis, MNS16A VNTR-274 (OR = 0.25, 95% CI = 0.06-0.79, P = 0.016) and genotype 274/302 (OR = 0.13, 95% CI = 0.01-0.58, P = 0.005) were associated with a significantly decreased risk of prostate cancer in the age group >70 years. Our finding of a MNS16A genotype conferring a protective effect against prostate cancer in older men suggests a potential role of this polymorphism in prostate cancer susceptibility but demands to be validated in further studies.

A functional tandem-repeats polymorphism in the downstream of TERT is associated with the risk of nasopharyngeal carcinoma in Chinese population

BACKGROUND

Increases in human telomerase reverse transcriptase (TERT) expression and telomerase activity are frequently seen in nasopharyngeal carcinoma (NPC). Recently, a variable tandem-repeats polymorphism, MNS16A, located in the downstream region of the TERT gene, was identified and reported to have an effect on TERT expression and telomerase activity. We examined whether the functional MNS16A was related to the risk of occurrence or progression of NPC in the Chinese population.

METHODS

We genotyped the MNS16A polymorphism in a case-control study of 855 patients with NPC and 1036 cancer-free controls using PCR, and determined genotype by classifying the DNA band of 243 or 272 base pairs (bp) as the short (S) allele and 302 or 333 bp as the long (L) allele. The genetic associations with the risk of NPC were analyzed by logistic regression.

RESULTS

The MNS16A genotype was not associated with the progression of NPC. However, individuals carrying the S alleles (SL + SS genotype) had a significantly reduced risk of NPC occurrence compared with those carrying the LL genotype (odds ratio (OR) = 0. 71, 95% confidence interval (CI) = 0. 52 to 0. 96, P = 0. 025). Using a immunohistochemical assay on the NPC tissues, the SL genotype carriers were found to have lower TERT expression than the LL genotype carriers (P = 0. 035).

CONCLUSIONS

Our study indicates that the TERT MNS16A polymorphism may contribute to the risk of NPC onset in Chinese population.

MNS16A tandem repeats minisatellite of human telomerase gene: a risk factor for colorectal cancer

Telomerase reactivation and expression of human telomerase gene [human telomerase reverse transcriptase (hTERT)] are hallmarks of unlimited proliferation potential of cancer cells. A polymorphic tandem repeats minisatellite of hTERT gene, termed MNS16A was reported to influence hTERT expression. To assess the role of MNS16A as potential biomarker for colorectal cancer (CRC), we investigated for the first time the association of MNS16A genotypes with risk of colorectal polyps and CRC. In the ongoing colorectal cancer study of Austria (CORSA), 3842 Caucasian participants were recruited within a large screening project in the province Burgenland including 90 CRC cases, 308 high-risk polyps, 1022 low-risk polyps and 1822 polyp free controls verified by colonoscopy. MNS16A genotypes were determined by polymerase chain reaction from genomic DNA. Associations of MNS16A genotypes with CRC risk were estimated by logistic regression analysis computing odds ratios (ORs) and 95% confidence intervals (CIs). We identified five different variable number of tandem repeats (VNTRs) of MNS16A including VNTR-364, a newly discovered rare variant. VNTR-274 allele was associated with a 2.7-fold significantly increased risk of CRC compared with the VNTR-302 wild-type (OR = 2.69; 95% CI = 1.11-6.50; P = 0.028). In our CORSA study, the medium length VNTR-274 was identified as risk factor for CRC. Although, this population-based study herewith reports the largest cohort size concerning MNS16A thus far, further large-scale studies in diverse populations are warranted to confirm hTERT MNS16A genotype as potential biomarker for assessment of CRC risk.