Genetic variation in telomere maintenance genes, telomere length, and lung cancer susceptibility

Circulating TERT serves as the novel diagnostic and prognostic biomarker for the resectable NSCLC

BACKGROUND

Telomerase reverse transcriptase (TERT) is a catalytic subunit of telomerase and required for cancer development. This study aims to reveal its clinical utility for diagnosis and prognosis of resectable NSCLC.

METHODS

TERT was quantitatively evaluated by the enzyme-linked immunosorbent assay (ELISA) from 69 patients before and after the surgery. The prognostic value was evaluated by disease-free survival (DFS) and overall survival (OS).

RESULTS

Circulating TERT in NSCLC patients were significantly higher than that in the healthy group, possessing the AUC of 0.90. Importantly, TERT change between pre- and post- operation was significantly correlated with OS and DFS (p = 0.022, p = 0.046 respectively), acted as the independent prognostic factors for DFS and OS, indicating it can serve as the promising diagnostic and prognostic biomarker for resectable non-small cell lung cancer (NSCLC).

CONCLUSIONS

TERT change between pre- and post- resection can serve as the promising biomarker for prognosis of resectable NSCLC.

A review of current developments in RNA modifications in lung cancer

Lung cancer has the highest incidence and mortality rates worldwide and is the primary cause of cancer-related death. Despite the rapid development of diagnostic methods and targeted drugs in recent years, many lung cancer patients do not benefit from effective therapies. The emergence of drug resistance has led to a reduction in the therapeutic effectiveness of targeted drugs, highlighting a crucial need to explore novel therapeutic targets. Many studies have found that epigenetic plays an important role in the occurrence of lung cancer. This review describes the biological function of epigenetic RNA modifications, such as m6A, m5C, m7G, and m1A, and recent advancements in their role in the development, progression, and prognosis of lung cancer. This review aims to provide new guidance for the treatment of lung cancer.

Inherited Telomere Biology Disorders: Pathophysiology, Clinical Presentation, Diagnostics, and Treatment

Background

Telomeres are the end-capping structures of all eukaryotic chromosomes thereby protecting the genome from damage and degradation. During the aging process, telomeres shorten continuously with each cell division until critically short telomeres prevent further proliferation whereby cells undergo terminal differentiation, senescence, or apoptosis. Premature aging due to critically short telomere length (TL) can also result from pathogenic germline variants in the telomerase complex or related genes that typically counteract replicative telomere shortening in germline and certain somatic cell populations, e.g., hematopoetic stem cells. Inherited diseases that result in altered telomere maintenance are summarized under the term telomere biology disorder (TBD).

Summary

Since TL both reflects but more importantly restricts the replicative capacity of various human tissues, a sufficient telomere reserve is particularly important in cells with high proliferative activity (e.g., hematopoiesis, immune cells, intestinal cells, liver, lung, and skin). Consequently, altered telomere maintenance as observed in TBDs typically results in premature replicative cellular exhaustion in the respective organ systems eventually leading to life-threatening complications such as bone marrow failure (BMF), pulmonary fibrosis, and liver cirrhosis.

Key Messages

The recognition of a potential congenital origin in approximately 10% of adult patients with clinical BMF is of utmost importance for the proper diagnosis, appropriate patient and family counseling, to prevent the use of inefficient treatment and to avoid therapy-related toxicities including appropriate donor selection when patients have to undergo stem cell transplantation from related donors. This review summarizes the current state of knowledge about TBDs with particular focus on the clinical manifestation patterns in children (termed early onset TBD) compared to adults (late-onset TBD) including typical treatment- and disease course-related complications as well as their prognosis and adequate therapy. Thereby, it aims to raise awareness for a disease group that is currently still highly underdiagnosed particularly when it first manifests itself in adulthood.

Leucocyte Telomere Length and Lung Cancer Risk: A Systematic Review and Meta-Analysis of Prospective Studies

Although numerous epidemiological studies are available, the relationship between leukocyte telomere length (LTL) and lung cancer risk is still controversial. This systematic review and meta-analysis, performed according to the PRISMA statement and MOOSE guidelines, aims to summarize the evidence and calculate the risk of lung cancer associated with LTL. The literature search was performed on PubMed, Web of Science, and Scopus databases through May 2024. A random-effects model was used to calculate the pooled risk. Heterogeneity was assessed using I2 and Cochran's Q statistic. Begg's and Egger's tests were used to detect publication bias. Based on 8055 lung cancer cases and 854,653 controls (nine prospective studies), longer LTL was associated with a significant 42% increment in all types of lung cancer risk (OR 1.42, 95% CI 1.24-1.63). The effect was even more evident for adenocarcinomas (OR 1.98, 95% CI 1.69-2.31), while no association was observed for squamous cell carcinoma (OR 0.87, 95% CI 0.72-1.06). Significantly, no association was found for current smokers (OR 1.08, 95% CI 0.90-1.30), while it remained high for both never-smokers (OR 1.92, 95% CI 1.62-2.28) and former smokers (OR 1.34, 95% CI 1.11-1.62). No significant publication bias was evidenced. Longer LTL is associated with an increment in lung cancer risk particularly in never-smoker subjects.

Conducting polymer composite-based biosensing materials for the diagnosis of lung cancer: A review

The development of a simple and fast cancer detection method is crucial since early diagnosis is a key factor in increasing survival rates for lung cancer patients. Among several diagnosis methods, the electrochemical sensor is the most promising one due to its outstanding performance, portability, real-time analysis, robustness, amenability, and cost-effectiveness. Conducting polymer (CP) composites have been frequently used to fabricate a robust sensor device, owing to their excellent physical and electrochemical properties as well as biocompatibility with nontoxic effects on the biological system. This review brings up a brief overview of the importance of electrochemical biosensors for the early detection of lung cancer, with a detailed discussion on the design and development of CP composite materials for biosensor applications. The review covers the electrochemical sensing of numerous lung cancer markers employing composite electrodes based on the conducting polyterthiophene, poly(3,4-ethylenedioxythiophene), polyaniline, polypyrrole, molecularly imprinted polymers, and others. In addition, a hybrid of the electrochemical biosensors and other techniques was highlighted. The outlook was also briefly discussed for the development of CP composite-based electrochemical biosensors for POC diagnostic devices.

Telomere length is associated with increased risk of cutaneous melanoma: a Mendelian randomization study

RESULTS

The MR analysis using two TL GWAS datasets revealed strong and consistent evidence that long TL is causally associated with an increased risk of CM. The analysis of the Codd et al. dataset found that long TL significantly predicted an elevated risk of CM (IVW OR = 2.411, 95% CI 2.092-2.780, P = 8.05E-34). Similarly, the analysis of the Li et al. dataset yielded consistent positive results across all MR methods, providing further robustness to the causal relationship (IVW OR = 2.324, 95% CI 1.516-3.565, P = 1.11E-04). The study provides evidence for a causal association between TL and CM susceptibility, indicating that longer TL increases the risk of developing CM and providing insight into the unique telomere biology in melanoma pathogenesis. Telomere maintenance pathways may be a potential target for preventing and treating CM.

Associations between telomere attrition, genetic variants in telomere maintenance genes, and non-small cell lung cancer risk in the Jammu and Kashmir population of North India

BACKGROUND

Telomeres are repetitive DNA sequences located at the ends of chromosomes, playing a vital role in maintaining chromosomal integrity and stability. Dysregulation of telomeres has been implicated in the development of various cancers, including non-small cell lung cancer (NSCLC), which is the most common type of lung cancer. Genetic variations within telomere maintenance genes may influence the risk of developing NSCLC. The present study aimed to evaluate the genetic associations of select variants within telomere maintenance genes in a population from Jammu and Kashmir, North India, and to investigate the relationship between telomere length and NSCLC risk.

METHODS

We employed the cost-effective and high-throughput MassARRAY MALDI-TOF platform to assess the genetic associations of select variants within telomere maintenance genes in a population from Jammu and Kashmir, North India. Additionally, we used TaqMan genotyping to validate our results. Furthermore, we investigated telomere length variation and its relation to NSCLC risk in the same population using dual-labeled fluorescence-based qPCR.

RESULTS

Our findings revealed significant associations of TERT rs10069690 and POT1 rs10228682 with NSCLC risk (adjusted p-values = 0.019 and 0.002, respectively), while TERF2 rs251796 and rs2975843 showed no significant associations. The TaqMan genotyping validation further substantiated the associations of TERT rs10069690 and rs2242652 with NSCLC risk (adjusted p-values = 0.02 and 0.003, respectively). Our results also demonstrated significantly shorter telomere lengths in NSCLC patients compared to controls (p = 0.0004).

CONCLUSION

This study highlights the crucial interplay between genetic variation in telomere maintenance genes, telomere attrition, and NSCLC risk in the Jammu and Kashmir population of North India. Our findings suggest that TERT and POT1 gene variants, along with telomere length, may serve as potential biomarkers and therapeutic targets for NSCLC in this population. Further research is warranted to elucidate the underlying mechanisms and to explore the potential clinical applications of these findings.

Relative Leukocyte Telomere Length and Genetic Variants in Telomere-Related Genes and Serum Levels Role in Age-Related Macular Degeneration

Telomere shortening is well known to be associated with ageing. Age is the most decisive risk factor for age-related macular degeneration (AMD) development. The older the individual, the higher the AMD risk. For this reason, we aimed to find any associations between telomere length, distribution of genetic variants in telomere-related genes (TERT, TERT-CLPTM1, TRF1, TRF2, and TNKS2), and serum TERF-1 and TERF2 levels on AMD development.

METHODS

Our study enrolled 342 patients with AMD and 177 healthy controls. Samples of DNA from peripheral blood leukocytes were extracted by DNA salting-out method. The genotyping of TERT rs2736098, rs401681 in TERT-CLPTM1 locus, TRF1 rs1545827, rs10107605, TNKS2 rs10509637, rs10509639, and TRF2 rs251796 and relative leukocyte telomere length (T/S) measurement were carried out using the real-time polymerase chain reaction method. Serum TERF-1 and TERF2 levels were measured by enzymatic immunoassay (ELISA).

RESULTS

We found longer telomeres in early AMD patients compared to the control group. Additionally, we revealed that minor allele C at TRF1 rs10107605 was associated with decreases the odds of both early and exudative AMD. Each minor allele G at TRF2 rs251796 and TRF1 rs1545827 C/T genotype and C/T+T/T genotypes, compared to the C/C genotype, increases the odds of having shorter telomeres. Furthermore, we found elevated TERF1 serum levels in the early AMD group compared to the control group.

CONCLUSIONS

In conclusion, these results suggest that relative leukocyte telomere length and genetic variants of TRF1 and TRF2 play a role in AMD development. Additionally, TERF1 is likely to be associated with early AMD.

Chronic Obstructive Pulmonary Disease and Lung Cancer: A Review for Clinicians

Chronic obstructive pulmonary disease (COPD) and lung cancer are common global causes of morbidity and mortality. Because both diseases share several predisposing risks, the 2 diseases may occur concurrently in susceptible individuals. The diagnosis of COPD has important implications for the diagnostic approach and treatment options if lesions concerning for lung cancer are identified during screening. Importantly, the presence of COPD has significant implications on prognosis and management of patients with lung cancer. In this monograph, we review the mechanistic linkage between lung cancer and COPD, the impact of lung cancer screening on patients at risk, and the implications of the presence of COPD on the approach to the diagnosis and treatment of lung cancer. This manuscript succinctly reviews the epidemiology and common pathogenetic factors for the concurrence of COPD and lung cancer. Importantly for the clinician, it summarizes the indications, benefits, and complications of lung cancer screening in patients with COPD, and the assessment of risk factors for patients with COPD undergoing consideration of various treatment options for lung cancer.

DNA Methylation-Based Age Prediction and Telomere Length Reveal an Accelerated Aging in Induced Sputum Cells Compared to Blood Leukocytes: A Pilot Study in COPD Patients

Aging is the predominant risk factor for most degenerative diseases, including chronic obstructive pulmonary disease (COPD). This process is however very heterogeneous. Defining the biological aging of individual tissues may contribute to better assess this risky process. In this study, we examined the biological age of induced sputum (IS) cells, and peripheral blood leukocytes in the same subject, and compared these to assess whether biological aging of blood leukocytes mirrors that of IS cells. Biological aging was assessed in 18 COPD patients (72.4 ± 7.7 years; 50% males). We explored mitotic and non-mitotic aging pathways, using telomere length (TL) and DNA methylation-based age prediction (DNAmAge) and age acceleration (AgeAcc) (i.e., difference between DNAmAge and chronological age). Data on demographics, life style and occupational exposure, lung function, and clinical and blood parameters were collected. DNAmAge (67.4 ± 5.80 vs. 61.6 ± 5.40 years; p = 0.0003), AgeAcc (-4.5 ± 5.02 vs. -10.8 ± 3.50 years; p = 0.0003), and TL attrition (1.05 ± 0.35 vs. 1.48 ± 0.21 T/S; p = 0.0341) are higher in IS cells than in blood leukocytes in the same patients. Blood leukocytes DNAmAge (r = 0.927245; p = 0.0026) and AgeAcc (r = 0.916445; p = 0.0037), but not TL, highly correlate with that of IS cells. Multiple regression analysis shows that both blood leukocytes DNAmAge and AgeAcc decrease (i.e., younger) in patients with FEV1% enhancement (p = 0.0254 and p = 0.0296) and combined inhaled corticosteroid (ICS) therapy (p = 0.0494 and p = 0.0553). In conclusion, new findings from our work reveal a differential aging in the context of COPD, by a direct quantitative comparison of cell aging in the airway with that in the more accessible peripheral blood leukocytes, providing additional knowledge which could offer a potential translation into the disease management.

Association of Leukocyte Telomere Length and Genes Involved in its Regulation With Oral Carcinoma

BACKGROUND/AIM

This study aimed to determine the relationship between the relative leukocyte telomere length (RLTL) and gene polymorphisms involved in its regulation with the occurrence of oral squamous cell carcinoma (OSCC).

PATIENTS AND METHODS

Patients with OSCC and healthy subjects were examined. Genotyping and RLTL measurement were carried out using rPCR.

RESULTS

The OSCC group had longer telomeres than controls (p=0.001). Minor allele T at TERF1rs1545827 may increase RLTL shortening (p=0.047). TNKS2rs10509639 A/G and A/G+G/G genotypes were associated with a 2.6-fold increased odd (p=0.012) and a 2.4-fold increased odd (p=0.019) of RLTL elongation compared to A/A genotype. The A/G genotype was associated with a 2.6-fold increased odd (p=0.011) compared to the A/A+G/G genotypes. Each G allele was associated with a 2.1-fold increased odd of longer RLTL (p=0.036).

CONCLUSION

Longer telomeres were found in patients with OSCC than in controls. The TERF1 rs1545827 and the TNKS2 rs10509639 polymorphisms were associated with an increase in RLTL.

A genetic variant in telomerase reverse transcriptase (TERT) modifies cancer risk in Lynch syndrome patients harbouring pathogenic MSH2 variants

Individuals with Lynch syndrome (LS), have an increased risk of developing cancer. Common genetic variants of telomerase reverse transcriptase (TERT) have been associated with a wide range of cancers, including colorectal cancer (CRC) in LS. We combined genotype data from 1881 LS patients, carrying pathogenic variants in MLH1, MSH2 or MSH6, for rs2075786 (G>A, intronic variant), 1207 LS patients for rs2736108 (C>T, upstream variant) and 1201 LS patients for rs7705526 (C>A, intronic variant). The risk of cancer was estimated by heterozygous/homozygous odds ratio (OR) with mixed-effects logistic regression to adjust for gene/gender/country of sample origin considering family identity. The AA genotype of SNP rs2075786 is associated with 85% higher odds at developing cancer compared to GG genotype in MSH2 pathogenic variant carriers (p = 0.0160). Kaplan-Meier analysis also shows an association for rs2075786; the AA allele for MSH2 variant carriers confers risk for earlier diagnosis of LS cancer (log-rank p = 0.0011). We report a polymorphism in TERT to be a possible modifier of disease risk in MSH2 pathogenic variant carriers. The rs2075786 SNP in TERT is associated with a differential risk of developing cancer for MSH2 pathogenic variant carriers. Use of this information has the potential to personalise screening protocols for LS patients.

Evaluation of 17 genetic variants in association with leukemia in the north Indian population using MassARRAY Sequenom

Leukemia is a heterogeneous disorder, characterized by elevated proliferation of white blood cells. In this study, we explored the association of 17 genetic variants with leukemia patients in the Jammu and Kashmir region of north India. The variants were genotyped by using a high-throughput Agena MassARRAY platform in 758 individuals (166 cases and 592 controls). Of the 17 single-nucleotide polymorphisms (SNPs) studied, five SNPs were showing significant association with the high risk of leukemia in the north Indian population, which includes rs10069690 of telomere reverse transcriptase (TERT) with OR = 0.34 (95% CI, 0.20-0.58; p = .0008), rs2972392 (​​​PSCA) with OR 1.86 (95% CI, 1.04-3.81; p = .035), rs4986764 (BRIP1) with OR 1.34 (95% CI, 1.00-1.80; p = .04), rs6990097 (TNKS) with OR 1.81 (95% CI, 1.2-2.6; p = .001) and rs12190287 (TCF21) with OR 2.87 (95% CI, 1.72-4.7; p = .0001) by allelic association using Plink and analyzed by SPSS. This is the first study to explore these variants with leukemia in the studied population.

Telomeres in toxicology: Occupational health

The ends of chromosomes shorten at each round of cell division, and this process is thought to be affected by occupational exposures. Occupational hazards may alter telomere length homeostasis resulting in DNA damage, chromosome aberration, mutations, epigenetic alterations and inflammation. Therefore, for the protection of genetic material, nature has provided a unique nucleoprotein structure known as a telomere. Telomeres provide protection by averting an inappropriate activation of the DNA damage response (DDR) at chromosomal ends and preventing recognition of single and double strand DNA (ssDNA and dsDNA) breaks or chromosomal end-to-end fusion. Telomeres and their interacting six shelterin complex proteins in coordination act as inhibitors of DNA damage machinery by blocking DDR activation at chromosomes, thereby preventing the occurrence of genome instability, perturbed cell cycle, cellular senescence and apoptosis. However, inappropriate DNA repair may result in the inadequate distribution of genetic material during cell division, resulting in the eventual development of tumorigenesis and other pathologies. This article reviews the current literature on the association of changes in telomere length and its interacting proteins with different occupational exposures and the potential application of telomere length or changes in the regulatory proteins as potential biomarkers for exposure and health response, including recent findings and future perspectives.

Shortened telomere length in peripheral blood leukocytes of patients with lung cancer, chronic obstructive pulmonary disease in a high indoor air pollution region in China

Lung cancer and chronic obstructive pulmonary disease (COPD) are closely linked diseases. In Xuanwei, China, the extremely high incidence and mortality rates of lung cancer and COPD are associated with exposure to household smoky coal burning. Previous studies found that telomere length was related to lung disease. The objective of this study is to investigate the relationship of peripheral blood leukocyte telomere length to both lung cancer and COPD, as well as indoor coal smoke exposure in Xuanwei. We measured telomere length using quantitative polymerase chain reaction (qPCR) in peripheral blood leukocytes of 216 lung cancer patients, 296 COPD patients, and 426 healthy controls from Xuanwei. The telomere length ratios (mean ± SD) in patients with lung cancer (0.76 ± 0.35) and COPD (0.81 ± 0.35) were significantly shorter than in that of controls (0.95 ± 0.39). Individuals with the shortest tertile telomere length had 3.90- and 4.54-fold increased risks of lung cancer and COPD, respectively, compared with individuals with the longest tertile telomere length. No correlation was found between telomere length and pack-years of smoking. In healthy subjects, coal smoke exposure level affected telomere length. Lung function was positively and negatively associated with telomere length and environmental exposure, respectively, when combination the control and COPD groups. The result suggests that shortened telomere length in peripheral blood leukocytes was associated with lung cancer and COPD and might be affected by coal smoke exposure level in Xuanwei. Whether variation in telomere length caused by environmental exposure has a role in lung cancer and COPD development and exacerbation needs further research.

Role of POT1 in Human Cancer

Simple Summary

The segmentation of eukaryotic genomes into discrete linear chromosomes requires processes to solve several major biological problems, including prevention of the chromosome ends being recognized as DNA breaks and compensation for the shortening that occurs when linear DNA is replicated. A specialized set of six proteins, collectively referred to as shelterin, is involved in both of these processes, and mutations in several of these are now known to be involved in cancer. Here, we focus on Protection of Telomeres 1 (POT1), the shelterin protein that appears to be most commonly involved in cancer, and consider the clinical significance of findings about its biological functions and the prevalence of inherited and acquired mutations in the POT1 gene.

Abstract

Telomere abnormalities facilitate cancer development by contributing to genomic instability and cellular immortalization. The Protection of Telomeres 1 (POT1) protein is an essential subunit of the shelterin telomere binding complex. It directly binds to single-stranded telomeric DNA, protecting chromosomal ends from an inappropriate DNA damage response, and plays a role in telomere length regulation. Alterations of POT1 have been detected in a range of cancers. Here, we review the biological functions of POT1, the prevalence of POT1 germline and somatic mutations across cancer predisposition syndromes and tumor types, and the dysregulation of POT1 expression in cancers. We propose a framework for understanding how POT1 abnormalities may contribute to oncogenesis in different cell types. Finally, we summarize the clinical implications of POT1 alterations in the germline and in cancer, and possible approaches for the development of targeted cancer therapies.

hTERT promoter methylation promotes small cell lung cancer progression and radiotherapy resistance

Small cell lung cancer (SCLC) has been a devastating actuality in clinic and the molecular mechanisms underlying this disease remain unclear. The epigenetic alterations located in the promoter region of human telomerase reverse transcriptase (hTERT) have been demonstrated as one of the most prevalent non-coding genomic modifications in multiple cancers. However, alteration of hTERT promoter methylation in SCLC and the subsequently induced change in tumor cell behavior remains unclear. In this research, we hypothesized that abnormal methylation of hTERT promotor enhanced the progression of SCLC and the outcome of radiotherapy resistance. Quantitative real-time PCR and western blot assays were performed to evaluate the RNA and protein levels of hTERT and enhancer of zeste homolog 2 (EZH2), respectively. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to estimate the viability and X-ray sensitivity of H20 and H446 cell lines. Functionally, upregulation of hTERT promoted the proliferation and migration of H20 and H446 cells, and the high-level of methylation in the promoter region of hTERT induced by radiation caused radio-resistance in SCLC. Mechanically, methylation of hTERT promoter enhanced the progression and radio-resistance of SCLC through upregulating the expression of its downstream effector EZH2.

Effect of TRF1 rs3863242 polymorphism on telomere length in omethoate-exposed workers

Telomere length was found to be associated with omethoate exposure and polymorphisms in certain genes among occupational workers. However, whether the polymorphisms in telomere-binding protein genes influence telomere length remains unclear. To explore the correlation between telomere length and polymorphisms in telomere-binding protein genes, telomere length in peripheral blood leukocytes was determined by real-time quantitative polymerase chain reaction in 180 omethoate-exposed workers and 115 healthy controls. Polymorphisms in 10 pairs of alleles were detected using flight mass spectrometry or polymerase chain reaction-restriction fragment length polymorphism technique. The results showed that individuals with GG genotype in TRF1 rs3863242 had longer telomere lengths than those with AG + AA genotype in the control group (p = 0.005). The multiple regression analysis suggested that both omethoate exposure (b = 0.526, p < 0.001) and TRF1 rs3863242 GG (b = 0.220, p = 0.002) were related to a longer telomere length. In conclusion, GG genotype in TRF1 rs3863242 is linked to prolongation of telomere length, and individuals with GG genotype are recommended to strengthen health protection in a Chinese occupational omethoate-exposed population.

Telomere-associated genes and telomeric lncRNAs are biomarker candidates in lung squamous cell carcinoma (LUSC)

In the past decade, research efforts were made to identify molecular biomarkers useful as therapeutic targets in Non-Small Cell Lung Cancer (NSCLC), the most frequent type of lung carcinoma. NSCLC presents different histological subtypes being the most prevalent LUSC (Lung Squamous Cell Cancer) and LUAD (Lung Adenocarcinoma), and only a subset of LUAD patients' present tumors expressing known targetable genetic alterations. Telomeres and its components, including telomerase, the enzyme that replenishes telomeres, have been considered potential cancer biomarkers due to their crucial role in cell proliferation and genome stability. Our study aims to quantify expression changes affecting telomere-associated genes and ncRNAs associated with telomere regulation and maintenance in NSCLC. We first assessed the transcriptome (RNA-Seq) data of NSCLC patients from The Cancer Genome Atlas (TCGA) and then we tested the expression of telomere-associated genes and telomeric ncRNAs (TERC, telomerase RNA component, and TERRA, telomere repeat-containing RNA) in Brazilian NCSLC patient samples by quantitative RT-PCR, using matched normal adjacent tissue samples as the control. We also estimated the mean size of terminal restriction fragments (TRF) of some Brazilian NSCLC patients using telomeric Southern blot. The TCGA analysis identified alterations in the expression profile of TERT and telomere damage repair genes, mainly in the LUSC subtype. The study of Brazilian NSCLC samples by RT-qPCR showed that LUSC and LUAD express high amounts of TERT and that although the mean TRF size of tumor samples was shorter compared to normal cells, telomeres in NSCLC are probably maintained by telomerase. Also, the expression analysis of Brazilian NSCLC samples identified statistically significant alterations in the expression of genes involved with telomere damage repair, as well as in TERC and TERRA, mainly in the LUSC subtype. We, therefore, concluded that telomere maintenance genes are significantly deregulated in NSCLC, representing potential biomarkers in the LUSC subtype.

The influence of ACYP2 polymorphisms on gastrointestinal cancer susceptibility in the Chinese Han population

BACKGROUND

Gastrointestinal cancer (GI cancer) is a type of cancer that has a high death rate. It has been reported that ACYP2 gene was associated with the development of gastric cancer and colorectal cancer, but it is not clear that the relationship between ACYP2 gene and GI cancer in Chinese Han population. This study aimed to investigate the association between polymorphisms of ACYP2 and GI cancer in the Chinese Han population.

METHODS

We used Agena MassARRAY to determine the genotypes of 1,160 GI cancer patients and 495 healthy controls. The correlation between ACYP2 variants and GI cancer risk was examined by logistic regression analysis.

RESULTS

We identified that rs6713088 (OR = 1.17, 95% CI: 1.00-1.36, p = 0.047), rs843711 (OR = 1.17, 95 CI: 1.01-1.36, p = 0.035), and rs11896604 (OR = 1.20, 95% CI: 1.00-1.45, p = 0.048) were correlated with an increased risk of GI cancer under allele model. Rs11125529 under the recessive model (OR = 2.05, 95% CI: 1.00-4.23, p = 0.038), rs843711 in recessive model (OR = 1.37, 95% CI: 1.04-1.82, p = 0.026), and rs11896604 under log-additive model (OR = 1.23, 95% CI: 1.01-1.51, p = 0.042) were associated with an increased risk of GI cancer.

CONCLUSION

Our study suggested that polymorphisms of ACYP2 gene might be associated with susceptibility to GI cancer.

Telomere length, ZNF208 genetic variants and risk of chronic obstructive pulmonary disease in the Hainan Li population

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a disease characterized by airflow limitation. It is not completely reversible and shows progressive development. ZNF208 rs8105767 affects telomere length, although the impact of telomere on COPD is still controversial. In the present study, we aimed to explore the impact of the ZNF208 gene polymorphism on telomere length and also that of telomere length on COPD in the Hainan Li population.

METHODS

In total, 270 COPD patients and 288 controls were recruited. Telomere length was measured by a quantitative real-time polymerase chain reaction. Five single nucleotide polymorphisms in ZNF208 were selected and genotyping was performed using MassARRAY software (Agena Bioscience Co. Ltd, San Diego, CA, USA). Differences in telomere length among the subjects with three genotypes of related genes were assessed using analysis of variance. Unconditional logistic regression was used to calculate odds ratios (OR) as the indicator of association between telomere length and COPD risk.

RESULTS

Relative telomere length in the COPD group and control group was 0.66 ± 0.47 and 1.44 ± 0.89, respectively. We grouped according to a median of 0.8284 for telomere length and observed that the risk of COPD for individuals with a telomere length less than 0.8284 is 2.92 times that for individuals with a telomere length longer than 0.8284 (OR = 2.92, 95% confidence interval = 2.01-4.25, p = 1.91 × 10^-8 ). Subjects carrying the G allele of rs2188972 had a longer telomere length. Subjects carrying the carrying the CA genotype of rs8103163 and AC genotype of rs7248488 had a longer telomere length compared to wild-type individuals.

CONCLUSIONS

Shorter telomeres increase COPD risk and the ZNF208 polymorphism affects telomere length in COPD patients.

Association of genetic polymorphisms of telomere binding proteins with cholinesterase activity in omethoate-exposed workers

Omethoate, an organophosphorous pesticide, can cause a variety of health effects, especially the decrease of cholinesterase activity. The aim of this study is to explore the association of genetic polymorphisms of telomere binding proteins with cholinesterase activity in omethoate-exposed population. Cholinesterase activities in whole blood, red blood cell and plasma were detected using acetylthiocholine and dithio-bis-(nitrobenzoic acid) method; Genetic Genotyping of POT1 rs1034794, POT1 rs10250202, TERF1 rs3863242 and TERT rs2736098 were performed with PCR-RFLP. The cholinesterase activities of whole blood, red blood cells and plasma in exposure group are significantly lower than that of the control group (P < 0.001). Multivariate analysis indicates that exposure group (b = - 1.016, P < 0.001), agender (b = 0.365, P < 0.001), drinking (b = 0.271, P = 0.004) and TERF1rs3863242 (b = - 0.368, P = 0.016) had an impact on cholinesterase activities. The results suggest that individual carrying AG+GG genotypes in TERF1 gene rs3863242 polymorphism were susceptible to damage in cholinesterase induced by omethoate.

Genetic polymorphisms in the TERT gene and susceptibility to non-small cell lung cancer in a Chinese Han population

Background

Recent studies have revealed that the TERT gene plays crucial roles in cancer initiation and development. Genome-wide analysis studies and case-control studies have demonstrated that polymorphisms in the TERT gene are associated with various cancers.

Materials and methods

In the current study, we analyzed the associations of eight single nucleotide polymorphisms (SNPs) in the TERT gene with non-small cell lung cancer (NSCLC) in a Chinese Han population. A total of 467 NSCLC patients and 526 healthy individuals were recruited for SNP genotyping using a TaqMan assay.

Results

Our results revealed that the allelic frequencies of rs2853677 and rs2853691 were significantly different between the NSCLC and control groups (P=0.004 and 0.001, respectively). Moreover, the T allele of rs2853677 and the A allele of rs2853691 might be the protective factors against NSCLC (OR=0.766; 95%CI: 0.639–0.918 and OR=0.714; 95%CI: 0.584–0.875, respectively). Additionally, stratified association analysis of the eight SNPs with the different pathological NSCLC stages (I+II and III+IV) and different pathological types (adenocarcinoma and squamous cell carcinoma) revealed that none of the SNPs were significantly different between patients with different pathological stages and pathological types.

Conclusion

Our results indicated that rs2853677 and rs2853691 in the TERT gene might be associated with NSCLC in this Chinese Han population.

Nested case-control study of telomere length and lung cancer risk among heavy smokers in the β-Carotene and Retinol Efficacy Trial

Background

Telomeres protect cells from genomic instability. We examined telomere length and lung cancer risk prospectively in heavy smokers.

Methods

In a nested case–control study with 709 cases and 1313 controls, conditional logistic regression was used to evaluate associations between telomere length (global, chromosome 5p, and 13q) and lung cancer risk by histotype, controlling for detailed smoking history.

Results

Risks of overall lung cancer and adenocarcinoma were suggestively elevated among individuals with telomere length in the longest tertile. No clear patterns were observed for other histotypes, or for chromosome 5p or 13q telomere length. Associations with adenocarcinoma were strongest among (OR, 95% CI for longest versus shortest tertile): former smokers (2.26, 1.03–4.96), individuals <65 years (2.22, 1.13–4.35), and women (2.21, 0.99–4.93).

Conclusions

Our large study of heavy smokers adds additional evidence that long telomere length prior to diagnosis is associated with risk of lung adenocarcinoma, but not other histotypes.

Screening and Biosensor-Based Approaches for Lung Cancer Detection

Early diagnosis of lung cancer helps to reduce the cancer death rate significantly. Over the years, investigators worldwide have extensively investigated many screening modalities for lung cancer detection, including computerized tomography, chest X-ray, positron emission tomography, sputum cytology, magnetic resonance imaging and biopsy. However, these techniques are not suitable for patients with other pathologies. Developing a rapid and sensitive technique for early diagnosis of lung cancer is urgently needed. Biosensor-based techniques have been recently recommended as a rapid and cost-effective tool for early diagnosis of lung tumor markers. This paper reviews the recent development in screening and biosensor-based techniques for early lung cancer detection.

Risk factors of Lung Cancer in nonsmoker

Generally, the cause of lung cancer is attributed to tobacco smoking. But many of the new lung cancer cases have been reported in nonsmokers. Apart from smoking; air pollution, environmental exposure, mutations, and single-nucleotide polymorphisms are known to be associated with lung cancer. Improper diet, alcohol consumption, marijuana smoking, estrogen, infections with human papillomavirus (HPV), HIV, and Epstein-Barr virus are suggested to be linked with lung cancer but clear evidences to ascertain their relation is not available. This article provides a comprehensive review of various risk factors and the underlying molecular mechanisms responsible for increasing the incidence of lung cancer. The pathologic, histologic, and genetic differences exist with lung cancer among smokers and nonsmokers. A better understanding of the risk factors, differences in pathology and molecular features of lung cancer in smokers and nonsmokers and the mode of action of various carcinogens will facilitate the prevention and management of lung cancer.

Is Leukocyte Telomere Length Related with Lung Cancer Risk?: A Meta-Analysis

BACKGROUND

Epidemiological studies have probed the correlation between telomere length and the risk of lung cancer, but their findings are inconsistent in this regard. The present meta-analysis study has been carried out to demonstrate the association between relative telomere length in peripheral blood leukocytes and the risk of lung cancer using an established Q-PCR technique.

METHODS

A systematic search was carried out using PubMed, EMBASE, and ISI before 2015. A total of 2925 cases of lung cancer and 2931 controls from 9 studies were employed to probe the relationship between lung cancer and telomere length .ORs were used at 95% CI. Random-effects models were used to investigate this relationship based on the heterogeneity test. Heterogeneity among studies was analyzed employing subgroup analysis based on type studies and the year of publication.

RESULTS

Random-effects meta-analysis revealed that patients with lung cancer were expected to have shorter telomere length than the control (1.13, 95% CI: 0.82-1.81, P=0.46). The summary of the pooled ORs of telomere length in adenocarcinoma lung cancer patients was 1 (95%CI=0.68-1.47, I2=93%) compared to patients with squamous cell lung cancer, which was 1.78 (95% CI=1.25-2.53, I2=3.9%). The meta-regression revealed that the effect of telomere length shortening, decreased and increased with the year of publication and the age of risks to lung cancer, was clearly related to short telomeres lengths.

CONCLUSION

Lung cancer risks clearly related with short telomeres lengths. In patients with breathing problems, lung cancer risk can be predicted by telomere length adjustment with age, sex, and smoking.

Prediagnosis Leukocyte Telomere Length and Risk of Ovarian Cancer

Background: The associations between telomere length and cancer risk are equivocal, and none have examined the association between prediagnosis leukocyte telomere length (LTL) and the risk of developing ovarian cancer.Methods: We prospectively measured LTL collected from 442 ovarian cancer cases and 727 controls in the Nurses' Health Studies and the Northern Sweden Health and Disease Study. Cases were matched to one or two controls on age, menopausal status, and date of blood collection. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression.Results: LTL was measured a median of 9.5 years before ovarian cancer diagnosis among cases. We observed a decreased risk of ovarian cancer with longer LTL. In multivariable models, women in the top quartile of LTL had an OR for ovarian cancer of 0.67 (95% CI, 0.46-0.97) compared with those in the bottom quartile. Inverse associations were stronger for nonserous cases (OR_{quartile 4 vs. quartile 1 of LTL} = 0.55, 95% CI, 0.33-0.94) and rapidly fatal cases (i.e., cases who died within 3 years of diagnosis; OR_{quartile 4 vs. quartile 1 of LTL} = 0.55, 95% CI, 0.32-0.95).Conclusions: Our prospective findings suggest that longer circulating LTL may be associated with a lower ovarian cancer risk, especially for nonserous and rapidly fatal cases. The evaluation of LTL in relation to ovarian cancer risk by tumor subtypes is warranted in larger prospective studies.Impact: Prediagnosis LTL may reflect an early event in the ovarian cancer development and could serve as a biomarker to predict future risk. Cancer Epidemiol Biomarkers Prev; 26(3); 339-45. ©2017 AACR.

Telomere length, genetic variants and risk of squamous cell carcinoma of the head and neck in Southeast Chinese

Telomere dysfunction participates in malignant transformation and tumorigenesis. Previous studies have explored the associations between telomere length (TL) and cancer susceptibility; however, the findings are inconclusive. The associations between genetic variants and TL have been verified by quite a few genome-wide association studies (GWAS). Yet, to date, there was no published study on the relationship between TL, related genetic variants and susceptibility to squamous cell carcinoma of the head and neck (SCCHN) in Chinese. Hence, we detected relative telomere length (RTL) by using quantitative PCR and genotyped seven selected single nucleotide polymorphisms by TaqMan allelic discrimination assay in 510 SCCHN cases and 913 controls in southeast Chinese. The results showed that RTL was significantly associated with SCCHN risk [(adjusted odds ratio (OR) = 1.19, 95% confidence interval (CI) = 1.08–1.32, P = 0.001]. Furthermore, among seven selected SNPs, only G allele of rs2736100 related to RTL in Caucasians was significantly associated with both the decreased RTL (P = 0.002) and the increased susceptibility to SCCHN in Chinese (additive model: adjusted OR = 1.17, 95%CI = 1.00–1.38, P = 0.049). These findings provide evidence that shortened TL is a risk factor for SCCHN, and genetic variants can contribute to both TL and the susceptibility to SCCHN in southeast Chinese population.

Genetic determinants of telomere length and risk of common cancers: a Mendelian randomization study

Epidemiological studies have reported inconsistent associations between telomere length (TL) and risk for various cancers. These inconsistencies are likely attributable, in part, to biases that arise due to post-diagnostic and post-treatment TL measurement. To avoid such biases, we used a Mendelian randomization approach and estimated associations between nine TL-associated SNPs and risk for five common cancer types (breast, lung, colorectal, ovarian and prostate cancer, including subtypes) using data on 51 725 cases and 62 035 controls. We then used an inverse-variance weighted average of the SNP-specific associations to estimate the association between a genetic score representing long TL and cancer risk. The long TL genetic score was significantly associated with increased risk of lung adenocarcinoma (P = 6.3 × 10(-15)), even after exclusion of a SNP residing in a known lung cancer susceptibility region (TERT-CLPTM1L) P = 6.6 × 10(-6)). Under Mendelian randomization assumptions, the association estimate [odds ratio (OR) = 2.78] is interpreted as the OR for lung adenocarcinoma corresponding to a 1000 bp increase in TL. The weighted TL SNP score was not associated with other cancer types or subtypes. Our finding that genetic determinants of long TL increase lung adenocarcinoma risk avoids issues with reverse causality and residual confounding that arise in observational studies of TL and disease risk. Under Mendelian randomization assumptions, our finding suggests that longer TL increases lung adenocarcinoma risk. However, caution regarding this causal interpretation is warranted in light of the potential issue of pleiotropy, and a more general interpretation is that SNPs influencing telomere biology are also implicated in lung adenocarcinoma risk.

Strong association between long and heterogeneous telomere length in blood lymphocytes and bladder cancer risk in Egyptian

Although it is widely recognized that telomere dysfunction plays an important role in cancer, the relationship between telomere function and bladder cancer risk is not well defined. In a case-control study of bladder cancer in Egypt, we examined relationships between two telomere features and bladder cancer risk. Telomere fluorescent in situ hybridization was used to measure telomere features using short-term cultured blood lymphocytes. Logistic regression was used to estimate the strength of association between telomere features and the risk of urothelial carcinoma of the bladder. High telomere length variation (TLV) across all chromosomal ends was significantly associated with an increased risk of bladder cancer [adjusted odds ratios (OR) = 2.22, 95% confidence interval (CI) = 1.48-3.35], as was long average telomere length (OR = 3.19, 95% CI = 2.07, 4.91). Further, TLV and average telomere length jointly affected bladder cancer risk: when comparing individuals with long telomere length and high TLV to those with short telomere length and low TLV, the adjusted OR was 14.68 (95% CI: 6.74-31.98). These associations were stronger among individuals who are 60 years of age or younger. In summary, long and heterogeneous telomere length in blood lymphocytes was strongly associated with an increased bladder cancer risk in Egyptian and the association was modulated by age.

The relationship between COPD and lung cancer

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COPD is a risk factor for lung cancer beyond their shared aetiology.

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Both are driven by oxidative stress.

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Both are linked to cellular aging, senescence and telomere shortening.

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Both have been linked to genetic predisposition.

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Both show altered epigenetic regulation of gene expression.

Both COPD and lung cancer are major worldwide health concerns owing to cigarette smoking, and represent a huge, worldwide, preventable disease burden. Whilst the majority of smokers will not develop either COPD or lung cancer, they are closely related diseases, occurring as co-morbidities at a higher rate than if they were independently triggered by smoking.

Lung cancer and COPD may be different aspects of the same disease, with the same underlying predispositions, whether this is an underlying genetic predisposition, telomere shortening, mitochondrial dysfunction or premature aging. In the majority of smokers, the burden of smoking may be dealt with by the body’s defense mechanisms: anti-oxidants such as superoxide dismutases, anti-proteases and DNA repair mechanisms. However, in the case of both diseases these fail, leading to cancer if mutations occur or COPD if damage to the cell and proteins becomes too great.

Alternatively COPD could be a driving factor in lung cancer, by increasing oxidative stress and the resulting DNA damage, chronic exposure to pro-inflammatory cytokines, repression of the DNA repair mechanisms and increased cellular proliferation. Understanding the mechanisms that drive these processes in primary cells from patients with these diseases along with better disease models is essential for the development of new treatments.

Telomere length variation: A potential new telomere biomarker for lung cancer risk

OBJECTIVES

In this report the associations between telomere length variation (TLV), mean telomere length in blood lymphocytes and lung cancer risk were examined.

MATERIALS AND METHODS

The study design is case-control. Cases (N=191) were patients newly diagnosed with histologically confirmed non-small cell lung cancer. Controls (N=207) were healthy individuals recruited from the same counties as cases and matched to cases on age and gender. Telomere fluorescent in situ hybridization was used to measure telomere features using short-term cultured blood lymphocytes. Logistic regression was used to estimate the strength of association between telomere features and lung cancer risk.

RESULTS

Telomere length variation across all chromosomal ends was significantly associated with lung cancer risk; adjusted odds ratios 4.67 [95% confidence interval (CI): 1.46-14.9] and 0.46 (95% CI: 0.25-0.84) for younger (age≤60) and older (age>60) individuals, respectively. TLV and mean telomere length jointly affected lung cancer risk: when comparing individuals with short telomere length and high TLV to those with long telomere length and low TLV, adjusted odd ratios were 8.21 (95% CI: 1.71-39.5) and 0.33 (95% CI: 0.15-0.72) for younger and older individuals, respectively.

CONCLUSIONS

TLV in blood lymphocytes is significantly associated with lung cancer risk and the associations were modulated by age. TLV in combination with mean telomere length might be useful in identifying high risk population for lung cancer computerized tomography screening.

Prediagnostic telomere length and risk of B-cell lymphoma-Results from the EPIC cohort study

Recent epidemiological investigations have reported on the association between telomere length (TL) and a number of malignancies, including B-cell lymphoma (BCL). The reported results for BCLs are however inconsistent. We carried out a nested case-control study to determine whether TL is associated with future risk of BCL. Using quantitative polymerase chain reaction, the relative TL (i.e. the ratio of telomere repeat copy number to single gene copy number) was measured in mononuclear cell DNA of prediagnostic peripheral blood samples of 464 lymphoma cases and 464 matched controls (median time between blood collection and diagnosis, 4.6 years). Conditional logistic regression was used to analyze the association between TL and the risk of developing lymphoma and histologic subtypes. TL was significantly longer in cases compared to controls (p = 0.01). Multivariable models showed a significantly increased risk of BCL [odds ratio (OR) = 1.66, 1.80 and 3.20 for quartiles 2-4, respectively, p-trend = 0.001], diffuse large B-cell lymphoma (DLBCL) (OR = 1.20, 2.48 and 2.36 for quartiles 2-4, respectively, p-trend = 0.03) and follicular lymphoma (FL) (OR = 1.39, 1.90 and 2.69 for quartiles 2-4, respectively, p-trend = 0.02) with increasing TL. This study suggests an association between longer leucocyte TL and increased risk of BCL which was most pronounced for DLBCL and FL.

Telomere length in white blood cell DNA and lung cancer: a pooled analysis of three prospective cohorts

We investigated the relationship between telomere length and lung cancer in a pooled analysis from three prospective cohort studies: the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, conducted among men and women in the United States, and previously published data from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Trial conducted among male smokers in Finland, and the Shanghai Women's Health Study (SWHS), which is comprised primarily of never-smokers. The pooled population included 847 cases and 847 controls matched by study, age, and sex. Leukocyte telomere length was measured by a monochrome multiplex qPCR assay. We used conditional logistic regression models to calculate ORs and their 95% confidence intervals (CI) for the association between telomere length and lung cancer risk, adjusted for age and pack-years of smoking. Longer telomere length was associated with increased lung cancer risk in the pooled analysis [OR (95% CI) by quartile: 1.00; 1.24 (0.90-1.71); 1.27 (0.91-1.78); and 1.86 (1.33-2.62); P trend = 0.000022]. Findings were consistent across the three cohorts and strongest for subjects with very long telomere length, i.e., lung cancer risks for telomere length [OR (95% CI)] in the upper half of the fourth quartile were 2.41 (1.28-4.52), 2.16 (1.11-4.23), and 3.02(1.39-6.58) for the PLCO trial, the ATBC trial, and the SWHS, respectively. In addition, the association persisted among cases diagnosed more than 6 years after blood collection and was particularly evident for female adenocarcinoma cases. Telomere length in white blood cell DNA may be a biomarker of future increased risk of lung cancer in diverse populations.

Telomere length in peripheral blood leukocytes and lung cancer risk: a large case-control study in Caucasians

Telomere dysfunction is a crucial event in malignant transformation and tumorigenesis. Telomere length in peripheral blood leukocytes has been associated with lung cancer risk, but the relationship has remained controversial. In this study, we investigated whether the association might be confounded by study of different histological subtypes of lung cancer. We measured relative telomere lengths in patients in a large case-control study of lung cancer and performed stratified analyses according to the two major histologic subtypes [adenocarcinoma and squamous cell carcinoma (SCC)]. Notably, patients with adenocarcinoma had longer telomeres than controls, whereas patients with SCC had shorter telomeres compared with controls. Long telomeres were associated with increased risk of adenocarcinoma, with the highest risk associated with female sex, younger age (<60 years), and lighter smoking (<30 pack-years). In contrast, long telomeres were protective against SCC, particularly in male patients. Our results extend the concept that telomere length affects risk of lung cancer in a manner that differs with histologic subtype.

Telomere dynamics in mice and humans

Telomeres are ribonucleoprotein structures capping the end of every linear chromosome. In all vertebrates, they are composed of TTAGGG repeats coated with specific protecting proteins. Telomeres shorten with each mitotic cell division, but telomerase, a reverse transcriptase, elongate telomeres in very specific cells, such as embryonic and adult stem cells. Although telomere sequence is identical in mice and humans and telomeres serve the same role of protecting chromosomes and genetic information from damage and erosion in both species, abnormalities in telomere maintenance and in telomerase function do not coincide in phenotype in humans and mice. The telomeres of most laboratory mice are 5 to 10 times longer than in humans, but their lifespan is 30 times shorter. Complete absence of telomerase has little expression in phenotype over several generations in mice, whereas heterozygosity for telomerase mutations in humans is sufficient to result in organ regeneration defect and cancer development. Patients with telomerase deficiency and very short telomeres may develop aplastic anemia, pulmonary fibrosis, or cirrhosis, whereas telomerase-null murine models display only modest hematopoietic deficiency and develop emphysema when exposed to cigarette smoke. In summary, telomerase deficiency in both humans and mice accelerate telomere shortening, but its consequences in the different organs and in the organism diverge, mainly due to telomere length differences.

A genome-wide association study identifies a locus on TERT for mean telomere length in Han Chinese

Leukocyte telomere length (LTL) is a predictor of aging and a number of age-related diseases. We performed genome-wide association studies of mean LTL in 2632 individuals,with a two-stage replication in 3917 individuals from Chinese populations. To further validate our findings, we get the results of 696 samples from a cohort of European ancestry. We identified two loci associated with LTL that map in telomerase reverse transcriptase (TERT; rs2736100, P = 1.93×10⁻⁵) on chromosome 5p15.33 and near keratin 80 (KRT80; rs17653722, P = 6.96×10⁻⁶) on 12q13.13. In Chinese population each C allele of rs2736100 and T allele of rs17653722 was associated with a longer mean telomere length of 0.026 and 0.059 T/S, respectively, equivalent to about 3 and 7 years of average age-related telomere attrition. Our findings provide new insights into telomere regulatory mechanism and even pathogenesis of age-related diseases.

Telomeres in lung disease

Telomeres are DNA-protein structures that cap the ends of chromosomes; telomerase is the enzyme that ensures their integrity. Telomere biology has recently been implicated in the pathogenesis of a variety of lung diseases, including idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease/emphysema, and lung cancer. This review highlights recent discoveries pertaining to the role of telomere biology in lung disease.

Telomere length varies by DNA extraction method: implications for epidemiologic research

BACKGROUND

Both shorter and longer telomeres in peripheral blood leukocyte (PBL) DNA have been associated with cancer risk. However, associations remain inconsistent across studies of the same cancer type. This study compares DNA preparation methods to determine telomere length from patients with colorectal cancer.

METHODS

We examined PBL relative telomere length (RTL) measured by quantitative PCR (qPCR) in 1,033 patients with colorectal cancer and 2,952 healthy controls. DNA was extracted with phenol/chloroform, PureGene, or QIAamp.

RESULTS

We observed differences in RTL depending on DNA extraction method (P < 0.001). Phenol/chloroform-extracted DNA had a mean RTL (T/S ratio) of 0.78 (range 0.01-6.54) compared with PureGene-extracted DNA (mean RTL of 0.75; range 0.00-12.33). DNA extracted by QIAamp yielded a mean RTL of 0.38 (range 0.02-3.69). We subsequently compared RTL measured by qPCR from an independent set of 20 colorectal cancer cases and 24 normal controls in PBL DNA extracted by each of the three extraction methods. The range of RTL measured by qPCR from QIAamp-extracted DNA (0.17-0.58) was less than from either PureGene or phenol/chloroform (ranges, 0.04-2.67 and 0.32-2.81, respectively).

CONCLUSIONS

RTL measured by qPCR from QIAamp-extracted DNA was less than from either PureGene or phenol/chloroform (P < 0.001).

IMPACT

Differences in DNA extraction method may contribute to the discrepancies between studies seeking to find an association between the risk of cancer or other diseases and RTL.

Telomerase at the intersection of cancer and aging

Although cancer and aging have been studied as independent diseases, mounting evidence suggests that cancer is an aging-associated disease and that cancer and aging share many molecular pathways. In particular, recent studies validated telomerase activation as a potential therapeutic target for age-related diseases; in addition, abnormal telomerase expression and telomerase mutations have been associated with many different types of human tumor. Here, we revisit the connection between telomerase and cancer and aging in light of recent findings supporting a role for telomerase not only in telomere elongation, but also in metabolic fitness and Wnt activation. Understanding the physiological impact of telomerase regulation is fundamental given the therapeutic strategies that are being developed that involve telomerase modulation.

Longer telomere length in peripheral white blood cells is associated with risk of lung cancer and the rs2736100 (CLPTM1L-TERT) polymorphism in a prospective cohort study among women in China

A recent genome-wide association study of lung cancer among never-smoking females in Asia demonstrated that the rs2736100 polymorphism in the TERT-CLPTM1L locus on chromosome 5p15.33 was strongly and significantly associated with risk of adenocarcinoma of the lung. The telomerase gene TERT is a reverse transcriptase that is critical for telomere replication and stabilization by controlling telomere length. We previously found that longer telomere length measured in peripheral white blood cell DNA was associated with increased risk of lung cancer in a prospective cohort study of smoking males in Finland. To follow up on this finding, we carried out a nested case-control study of 215 female lung cancer cases and 215 female controls, 94% of whom were never-smokers, in the prospective Shanghai Women’s Health Study cohort. There was a dose-response relationship between tertiles of telomere length and risk of lung cancer (odds ratio (OR), 95% confidence interval [CI]: 1.0, 1.4 [0.8–2.5], and 2.2 [1.2–4.0], respectively; P trend = 0.003). Further, the association was unchanged by the length of time from blood collection to case diagnosis. In addition, the rs2736100 G allele, which we previously have shown to be associated with risk of lung cancer in this cohort, was significantly associated with longer telomere length in these same study subjects (P trend = 0.030). Our findings suggest that individuals with longer telomere length in peripheral white blood cells may have an increased risk of lung cancer, but require replication in additional prospective cohorts and populations.

Genetic susceptibility to lung cancer--light at the end of the tunnel?

Lung cancer is one of the most common and deadliest cancers in the world. The major socio-environmental risk factor involved in the development of lung cancer is cigarette smoking. Additionally, there are multiple genetic factors, which may also play a role in lung cancer risk. Early work focused on the presence of relatively prevalent but low-penetrance alterations in candidate genes leading to increased risk of lung cancer. Development of new technologies such as genomic profiling and genome-wide association studies has been helpful in the detection of new genetic variants likely involved in lung cancer risk. In this review, we discuss the role of multiple genetic variants and review their putative role in the risk of lung cancer. Identifying genetic biomarkers and patterns of genetic risk may be useful in the earlier detection and treatment of lung cancer patients.

Genetic variant in the telomerase gene modifies cancer risk in Lynch syndrome

Lynch syndrome (LS) is an inherited cancer-predisposing disorder caused by germline mutations in the mismatch repair (MMR) genes. The high variability in individual cancer risk observed among LS patients suggests the existence of modifying factors. Identifying genetic modifiers of risk could help implement personalized surveillance programs based on predicted cancer risks. Here we evaluate the role of the telomerase (hTERT) rs2075786 SNP as a cancer-risk modifier in LS, studying 255 and 675 MMR gene mutation carriers from Spain and the Netherlands, respectively. The study of the Spanish sample revealed that the minor allele (A) confers increased cancer risk at an early age. The analysis of the Dutch sample confirmed the association of the A allele, especially in homozygosity, with increased cancer risk in mutation carriers under the age of 45 (relative riskLSca<45_AA=2.90; 95% confidence interval=1.02-8.26). Rs2075786 is associated with colorectal cancer (CRC) risk neither in the general population nor in non-Lynch CRC families. In silico studies predicted that the SNP causes the disruption of a transcription binding site for a retinoid receptor, retinoid X receptor alpha, probably causing early telomerase activation and therefore accelerated carcinogenesis. Notably, cancer-affected LS patients with the AA genotype have shorter telomeres than those with GG. In conclusion, MMR gene mutation carriers with hTERT rs2075786 are at high risk to develop a LS-related tumor at an early age. Cancer-preventive measures and stricter cancer surveillance at early ages might help prevent or early detect cancer in these mutation carriers.

Association of leukocyte telomere length with colorectal cancer risk: nested case-control findings from the Shanghai Women's Health Study

BACKGROUND

Telomeres are specialized chromatin structures essential for maintenance of chromosomal integrity and stability. Abnormal alteration of telomere length has been linked to several cancers; however, epidemiologic evidence about the association of telomere length with colorectal cancer risk has been conflicting.

METHODS

We conducted a nested case-control study to evaluate the association between telomere length and colorectal cancer risk using peripheral blood samples collected before cancer diagnosis. The study included 441 women with incident colorectal cancer and 549 matched controls. Monochrome multiplex quantitative PCR was applied to measure relative telomere length. Multiple logistic regressions were used to derive adjusted OR with 95% confidence intervals (CI) as the measure of association between telomere length and subsequent colorectal cancer risk.

RESULTS

A U-shaped association was observed between telomere length and colorectal cancer risk (test for nonlinearity P = 0.0112). Women with telomere length in the third quintile (40th-60th percentiles) had the lowest risk of colorectal cancer, and the risks were elevated with a shorter or longer telomere length. This U-shaped association did not statistically differ for colon cancer and rectum cancer.

CONCLUSIONS AND IMPACT

Our prospective study revealed a U-shaped association between telomere length in peripheral blood cells and colorectal cancer risk. Our findings provide strong evidence that both very short and very long telomeres are associated with increased risk of colorectal cancer.