Role In Chromosome Stability Research Articles

Big data analysis identified a telomere-related signature predicting the prognosis and drug sensitivity in lung adenocarcinoma.

Telomeres exert a critical role in chromosome stability and aberrant regulation of telomerase may result in telomeres dysfunction and genomic instability, which are involved in the occurrence of cancers. However, limited studies have been performed to fully clarify the immune infiltration and clinical significance of telomeres-related genes (TRGs) in lung adenocarcinoma (LUAD). The number of clusters of LUAD was determined by consensus clustering analysis. The prognostic signature was constructed and verified using TCGA and GSE42127 dataset with Least Absolute Shrinkage and Selection Operator cox regression analysis. The correlation between different clusters and risk-score and drug therapy response was analyzed using TIDE and IMvigor210 dataset. Using several miRNA and lncRNA related databases, we constructed a lncRNA-miRNA-mRNA regulatory axis. We identified 2 telomeres-related clusters in LUAD, which had distinct differences in prognostic stratification, TMB score, TIDE score, immune characteristics and signal pathways and biological effects. A prognostic model was developed based on 21 TRGs, which had a better performance in risk stratification and prognosis prediction compared with other established models. TRGs-based risk score could serve as an independent risk factor for LUAD. Survival prediction nomogram was also developed to promote the clinical use of TRGs risk score. Moreover, LUAD patients with high risk score had a high TMB score, low TIDE score and IC50 value of common drugs, suggesting that high risk score group might benefit from receiving immunotherapy, chemotherapy and target therapy. We also developed a lncRNA KCNQ1QT1/miR-296-5p/PLK1 regulatory axis. Our study identified 2 telomeres-related clusters and a prognostic model in LUAD, which could be helpful for risk stratification, prognosis prediction and treatment approach selection.

Downregulation of MUS81 expression inhibits cell migration and maintains EBV latent infection through miR-BART9-5p in EBV-associated gastric cancer.

Epstein-Barr virus (EBV) infection is associated with the occurrence and development of gastric cancer (GC). Methyl methanesulfonate and ultraviolet-sensitive gene 81 (MUS81) is the catalytic component of a structure-specific endonuclease and plays an important role in chromosomal stability. However, the link between EBV infection and MUS81 remains unclear. In the present study, we found that MUS81 expression was much lower in EBV-associated GC cells than in EBV-negative GC. MUS81 acts as an oncogene in GC by inducing the cell migration and proliferation. Western blot and luciferase reporter assays revealed that miR-BART9-5p directly targeted MUS81 and downregulated its expression. Additionally, overexpression of MUS81 in EBV-positive GC cells inhibited the expression of EBV nuclear antigen 1 (EBNA1). EBNA1 is critical for the pathogenesis of EBV-associated tumors and the maintenance of a stable copy number of the viral genomes. Altogether, these results indicated that the lowering MUS81 expression might be a mechanism by EBV to maintain its latent infection.

Abnormal function of telomere protein TRF2 induces cell mutation and the effects of environmental tumor‑promoting factors (Review).

Recent studies have found that somatic gene mutations and environmental tumor-promoting factors are both indispensable for tumor formation. Telomeric repeat-binding factor (TRF)2 is the core component of the telomere shelterin complex, which plays an important role in chromosome stability and the maintenance of normal cell physiological states. In recent years, TRF2 and its role in tumor formation have gradually become a research hot topic, which has promoted in-depth discussions into tumorigenesis and treatment strategies, and has achieved promising results. Some cells bypass elimination, due to either aging, apoptosis via mutations or abnormal prolongation of the mitotic cycle, and enter the telomere crisis period, where large-scale DNA reorganization occurs repeatedly, which manifests as the precancerous cell cycle. Finally, at the end of the crisis cycle, the mutation activates either the expression level of telomerase or activates the alternative lengthening of telomere mechanism to extend the local telomeres. Under the protection of TRF2, chromosomes are gradually stabilized, immortal cells are formed and the stagewise mutation-driven transformation of normal cells to cancer cells is completed. In addition, TRF2 also shares the characteristics of environmental tumor-promoting factors. It acts on multiple signal transduction pathway-related proteins associated with cell proliferation, and affects peripheral angiogenesis, inhibits the immune recognition and killing ability of the microenvironment, and maintains the stemness characteristics of tumor cells. TRF2 levels are abnormally elevated by a variety of tumor control proteins, which are more conducive to the protection of telomeres and the survival of tumor cells. In brief, the various regulatory mechanisms which tumor cells rely on to survive are organically integrated around TRF2, forming a regulatory network, which is conducive to the optimization of the survival direction of heterogeneous tumor cells, and promotes their survival and adaptability. In terms of clinical application, TRF2 is expected to become a new type of cancer prognostic marker and a new tumor treatment target. Inhibition of TRF2 overexpression could effectively cut off the core network regulating tumor cell survival, reduce drug resistance, or bypass the mutation under the pressure of tumor treatment selection, which may represent a promising therapeutic strategy for the complete eradication of tumors in the clinical setting. Based on recent research, the aim of the present review was to systematically elaborate on the basic structure and functional characteristics of TRF2 and its role in tumor formation, and to analyze the findings indicating that TRF2 deficiency or overexpression could cause severe damage to telomere function and telomere shortening, and induce DNA damage response and chromosomal instability.

TP53BP1 regulates chromosome alignment and spindle bipolarity in mouse oocytes.

Meiotic oocytes lack classic centrosomes; therefore, bipolar spindle assembly depends on the clustering of acentriolar microtubule-organizing centers (MTOCs) into two poles. The bipolar spindle is an essential cellular component that ensures accurate chromosome segregation during anaphase. If the spindle does not form properly, it can result in aneuploidy or cell death. However, the molecular mechanism by which the bipolar spindle is established is not yet fully understood. Tumor suppressor p53-binding protein 1 (TP53BP1) is known to mediate the DNA damage response. Several recent studies have indicated that TP53BP1 has noncanonical roles in processes, such as spindle formation; however, the role of TP53BP1 in oocyte meiosis is currently unclear. Our results show that TP53BP1 knockdown affects spindle bipolarity and chromatin alignment by altering MTOC stability during oocyte maturation. TP53BP1 was localized in the cytoplasm and displayed an irregular cloud pattern around the spindle/chromosome region. TP53BP1 was also required for the correct localization of MTOCs into the two spindle poles during pro-meiosis I. TP53BP1 deletion altered the MTOC-localized Aurora Kinase A. TP53BP1 knockdown caused the microtubules to detach from the kinetochores and increased the rate of aneuploidy. Taken together, our data show that TP53BP1 plays crucial roles in chromosome stability and spindle bipolarity during meiotic maturation.

Depletion of ATP-Citrate Lyase (ATPCL) Affects Chromosome Integrity Without Altering Histone Acetylation in Drosophila Mitotic Cells.

The Citrate Lyase (ACL) is the main cytosolic enzyme that converts the citrate exported from mitochondria by the SLC25A1 carrier in Acetyl Coenzyme A (acetyl-CoA) and oxaloacetate. Acetyl-CoA is a high-energy intermediate common to a large number of metabolic processes including protein acetylation reactions. This renders ACL a key regulator of histone acetylation levels and gene expression in diverse organisms including humans. We have found that depletion of ATPCL, the Drosophila ortholog of human ACL, reduced levels of Acetyl CoA but, unlike its human counterpart, does not affect global histone acetylation and gene expression. Nevertheless, reduced ATPCL levels caused evident, although moderate, mitotic chromosome breakage suggesting that this enzyme plays a partial role in chromosome stability. These defects did not increase upon X-ray irradiation, indicating that they are not dependent on an impairment of DNA repair. Interestingly, depletion of ATPCL drastically increased the frequency of chromosome breaks (CBs) associated to mutations in scheggia, which encodes the ortholog of the mitochondrial citrate carrier SLC25A1 that is also required for chromosome integrity and histone acetylation. Our results indicate that ATPCL has a dispensable role in histone acetylation and prevents massive chromosome fragmentation when citrate efflux is altered.

At the Beginning of the End and in the Middle of the Beginning: Structure and Maintenance of Telomeric DNA Repeats and Interstitial Telomeric Sequences.

Tandem DNA repeats derived from the ancestral (TTAGGG)n run were first detected at chromosome ends of the majority of living organisms, hence the name telomeric DNA repeats. Subsequently, it has become clear that telomeric motifs are also present within chromosomes, and they were suitably called interstitial telomeric sequences (ITSs). It is well known that telomeric DNA repeats play a key role in chromosome stability, preventing end-to-end fusions and precluding the recurrent DNA loss during replication. Recent data suggest that ITSs are also important genomic elements as they confer its karyotype plasticity. In fact, ITSs appeared to be among the most unstable microsatellite sequences as they are highly length polymorphic and can trigger chromosomal fragility and gross chromosomal rearrangements. Importantly, mechanisms responsible for their instability appear to be similar to the mechanisms that maintain the length of genuine telomeres. This review compares the mechanisms of maintenance and dynamic properties of telomeric repeats and ITSs and discusses the implications of these dynamics on genome stability.

Genetic and Epigenetic Features of Rapidly Progressing IDH-Mutant Astrocytomas.

IDH-mutant astrocytomas are significantly less aggressive than their IDH-wildtype counterparts. We analyzed The Cancer Genome Atlas dataset (TCGA) and identified a small group of IDH-mutant, WHO grade II-III astrocytomas (n = 14) with an unexpectedly poor prognosis characterized by a rapid progression to glioblastoma and death within 3 years of the initial diagnosis. Compared with IDH-mutant tumors with the typical, extended progression-free survival in a control group of age-similar patients, the tumors in the rapidly progressing group were characterized by a markedly increased level of overall copy number alterations ([CNA]; p = 0.006). In contrast, the mutation load was similar, as was the methylation pattern, being consistent with IDH-mutant astrocytoma. Two of the gliomas (14%) in the rapidly progressing, IDH-mutant group but none of the other grade II-III gliomas in the TCGA (n = 283) had pathogenic mutations in genes (FANCB and APC) associated with maintaining chromosomal stability. These results suggest that chromosomal instability can negate the beneficial effect of IDH mutations in WHO II-III astrocytomas. The mechanism of the increased CNA is unknown but in some cases appears to be due to mutations in genes with a role in chromosomal stability. Increased CNA could serve as a biomarker for tumors at risk for rapid progression.

HHV-6A/B Integration and the Pathogenesis Associated with the Reactivation of Chromosomally Integrated HHV-6A/B.

Unlike other human herpesviruses, human herpesvirus 6A and 6B (HHV-6A/B) infection can lead to integration of the viral genome in human chromosomes. When integration occurs in germinal cells, the integrated HHV-6A/B genome can be transmitted to 50% of descendants. Such individuals, carrying one copy of the HHV-6A/B genome in every cell, are referred to as having inherited chromosomally-integrated HHV-6A/B (iciHHV-6) and represent approximately 1% of the world’s population. Interestingly, HHV-6A/B integrate their genomes in a specific region of the chromosomes known as telomeres. Telomeres are located at chromosomes’ ends and play essential roles in chromosomal stability and the long-term proliferative potential of cells. Considering that the integrated HHV-6A/B genome is mostly intact without any gross rearrangements or deletions, integration is likely used for viral maintenance into host cells. Knowing the roles played by telomeres in cellular homeostasis, viral integration in such structure is not likely to be without consequences. At present, the mechanisms and factors involved in HHV-6A/B integration remain poorly defined. In this review, we detail the potential biological and medical impacts of HHV-6A/B integration as well as the possible chromosomal integration and viral excision processes.

Nuclear PTEN interferes with binding of Ku70 at double-strand breaks through post-translational poly(ADP-ribosyl)ation

PTEN is a tumor suppressor gene characterized as a phosphatase that antagonizes the phosphatidylinositol 3-kinase signaling pathway in the cytoplasm. Nuclear PTEN plays roles in chromosomal stability, in which the double-strand breaks (DSB) repair mediated by homologous recombination (HR) and non-homologous end joining (NHEJ) is critical. Herein, the role of nuclear PTEN in DSB repair and the underlying molecular mechanism was investigated in this study. Using human breast cancer BT549 and MDA-MB-231 cell lines, we reveal a specific feature of PTEN that controls poly(ADP-ribosyl)ation of Ku70 and interferes with binding of Ku70 at DSB. Plasmid-based end joining and reporter assays showed that nuclear PTEN restrained NHEJ efficacy. Electrophoretic mobility shift assays showed that nuclear PTEN impaired Ku70 complex binding to DSB by 3-fold. Co-immunoprecipitation assay showed PTEN regulated poly(ADP-ribosyl)ation of Ku70 instead of directly interacting with Ku70, while PTEN promoted the poly(ADP-ribosyl)ation of PARP1 and induced the degradation of PARP1 in PTEN-WT cells exposed to DSB agents. Of note, the role of PTEN in DSB repair mostly depends on its nuclear localization rather than its phosphatase activity. As a result, the absence of nuclear PTEN rather than phosphatase-negative PTEN confers cell hypersensitivity to anti-tumor DNA damage drugs. This finding contributes to understanding the effect of PTEN in repair of DSB and using defined anti-tumor DSB drugs to treat tumor cells with aberrant PTEN.

RbAp48 is essential for viability of vertebrate cells and plays a role in chromosome stability.

RbAp46/48, histone chaperone, is a family of evolutionarily conserved WD40 repeat-containing proteins, which are involved in various chromatin-metabolizing processes, but their in vivo functional relevance is yet unclear. In order to examine the biological role of pRbAp48 in chicken DT40 cells, we generated a tetracycline-inducible system for conditional RbAp48-knockout cells. Depletion of RbAp48 led to delayed S phase progression associated with slow DNA synthesis and nascent nucleosome formation, followed by accumulation in G2/M phase, finally leading to cell death. Prior to cell death, these cells exhibited aberrant mitosis such as highly condensed and abnormal chromosome alignment on the metaphase plate, leading to chromosome missegregation. Depletion of RbAp48 also caused dissociation of heterochromatin protein 1 (HP1) from pericentromeric heterochromatin. Furthermore, depletion of RbAp48 from cells led to elevated levels of acetylation and slightly decreased levels of methylation, specifically at Lys-9 residue of histone H3. These results suggest that RbAp48 plays an important role in chromosome stability for proper organization of heterochromatin structure through the regulation of epigenetic mark.

ASPP1/2-PP1 complexes are required for chromosome segregation and kinetochore-microtubule attachments.

Regulated interactions between kinetochores and spindle microtubules are critical for maintaining genomic stability during chromosome segregation. Defects in chromosome segregation are widespread phenomenon in human cancers that are thought to serve as the fuel for tumorigenic progression. Tumor suppressor proteins ASPP1 and ASPP2, two members of the apoptosis stimulating proteins of p53 (ASPP) family, are frequently down-regulated in human cancers. Here we report that ASPP1/2 are required for proper mitotic progression. In ASPP1/2 co-depleted cells, the persistence of unaligned chromosomes and the reduction of tension across sister kinetochores on aligned chromosomes resulted in persistent spindle assembly checkpoint (SAC) activation. Using protein affinity purification methods, we searched for functional partners of ASPP1/2, and found that ASPP1/2 were associated with a subset of kinetochore proteins (Hec1, KNL-1, and CENP-F). It was found that ASPP1/2 act as PP1-targeting subunits to facilitate the interaction between PP1 and Hec1, and catalyze Hec1 (Ser165) dephosphorylation during late mitosis. These observations revealed a previously unrecognized function of ASPP1/2 in chromosome segregation and kinetochore-microtubule attachments that likely contributes to their roles in chromosome stability and tumor suppression.

Expression and clinical significance of the securin in colorectal cancer

Purpose: Securin is a regulatory protein, which plays a central role in chromosome stability and control of the metaphase-anaphase transition and anaphase onset. Securin blocks separase/extra spindle pole bodies homolog 1 function, preventing the proteolysis of the subsequent dissociation of the chromosome. Securin is expressed at low level in most tissues, but many patient suffering epithelial neoplasms are over-expressed. The aim our study was to evaluate whether securin affects tumorigenesis and prognosis in patients of colorectal cancer. Methods: To clarify the roles of securin in colorectal tumorigenesis, its expression was examined by immunohistochemistry on a tissue microarray with its comparison with clinicopathologic parameters and prognosis survivals of the colorectal carcinomas. Results: Securin was overexpressedin 272 (76.2%) of 357 colorectal carcinomas. Overexpression of securin was correlated with gender (P=0.060), pathologic T stage (P=0.006) and tumor node metastasis stage (P=0.002), but securin overexpression was not correlated with lymphovascular invasions. Securin overexpression was not correlated with 5-year survival rate by Kaplan-Miere survival model. Conclusion: Securin expression was correlated with T stage and TNM (tumor node and metastasis) stage in colorectal cancer. Our study showed a possible role for securin in colorectal tumorigenesis. These findings indicate that securin has a function of tumorigenesis with tumor enlargement, not of lymphovasculogenesis. Keywords: Carcinogenesis, Chromosomal instability, Colorectal neoplasms, Pituitary tumor-transforming gene protein

Abstract P6-04-14: mRNA expressions of lamin B1 and lamin B receptor: Clinical correlations with human breast cancer

Abstract BACKGROUND: Lamin B (LMNB) and lamin B receptor (LBR) are key components of the nuclear envelope, with roles in chromosomal stability, DNA repair, and cell differentiation. Lamins provide structural support to the nuclear envelope, while LBR is believed to anchor lamin B to the envelope. In addition, LBR also has a number of downstream mediators which affect cell cycle and cell differentiation. Classically, they have been implicated in a spectrum of largely congenital ailments including certain forms of muscle dystrophy and progeria. These conditions are collectively referred to as “laminopathies”. More recently, defects in the expression of lamins have been implicated in neoplasias of the colon, prostate, liver and ovaries. In this study, we have endeavoured to elucidate the relationships between the mRNA expressions of LMNB1 and LBR and the clinicopathological parameters of human breast cancer. METHODS: Breast cancer tissues (n = 115) and associated non-cancerous tissue (ANCT) (n = 30) underwent reverse transcription and quantitative PCR. Transcript levels were correlated with clinicopathological data. RESULTS: LMNB1 mRNA expression was higher in ANCT as compared to cancerous tissue (ANCT vs. cancerous tissue: 0.12 vs. 0.00; p = <0.0001). This difference remained highly significant in all patient categories by tumour grade and clinical stage. In addition, the expression of LMNB1 declined with worsening clinical outcome. This association was statistically significant when comparing patient with disease-free survival with disease related mortalities (Disease-free vs. mortalities: 0.0011 vs. 0.000; p = 0.0177). LBR mRNA expression was found to be directly associated with tumour grade (grade 1 vs.3: 0.00 vs. 0.00; p = 0.0479) and the Nottingham Prognostic Index (NPI1 vs. 3: 0.00 vs. 0.00; p = 0.0551). CONCLUSIONS: To our knowledge, this is the first study to suggest such a role for LMNB1 and LBR in human breast cancer. The contrasting relationships of LMNB1 and LBR expressions with the clinicopathological parameters of human breast cancer may suggest that disruptions in the physiologically normal interactions between these molecules in the nuclear envelope may serve as pathway leading towards the pathogenesis of human breast cancer. Potentially this may be a significant pathway requiring further investigation to be better understood, in order to identify further potential areas for therapeutic intervention. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-04-14.

RTEL1, une hélicase de l’ADN essentielle à la stabilité du génome

RTEL1 (regulator of telomere length helicase 1) is a DNA helicase that has been identified more than 10 years ago. Many works since, mainly in the nematode Caenorhabditis elegans and the mouse, have highlighted its role in chromosomal stability, maintenance of telomere length, and DNA repair. Recently, four laboratories have characterized RTEL1 mutations in patients with dyskeratosis congenita (DC) and Hoyeraal-Hreidarsson (HH) syndrome, a rare and severe variant of DC. We here summarize the current knowledge on RTEL1 and discuss the possible other functions that RTEL1 could play.

Centromere Binding and a Conserved Role in Chromosome Stability for SUMO-Dependent Ubiquitin Ligases

The Saccharomyces cerevisiae Slx5/8 complex is the founding member of a recently defined class of SUMO-targeted ubiquitin ligases (STUbLs). Slx5/8 has been implicated in genome stability and transcription, but the precise contribution is unclear. To characterise Slx5/8 function, we determined genome-wide changes in gene expression upon loss of either subunit. The majority of mRNA changes are part of a general stress response, also exhibited by mutants of other genome integrity pathways and therefore indicative of an indirect effect on transcription. Genome-wide binding analysis reveals a uniquely centromeric location for Slx5. Detailed phenotype analyses of slx5Δ and slx8Δ mutants show severe mitotic defects that include aneuploidy, spindle mispositioning, fish hooks and aberrant spindle kinetics. This is associated with accumulation of the PP2A regulatory subunit Rts1 at centromeres prior to entry into anaphase. Knockdown of the human STUbL orthologue RNF4 also results in chromosome segregation errors due to chromosome bridges. The study shows that STUbLs have a conserved role in maintenance of chromosome stability and links SUMO-dependent ubiquitination to a centromere-specific function during mitosis.

Acacetin and Chrysin, Two Polyphenolic Compounds, Alleviate Telomeric Position Effect in Human Cells

We took advantage of the ability of human telomeres to silence neighboring genes (telomere position effect or TPE) to design a high-throughput screening assay for drugs altering telomeres. We identified, for the first time, that two dietary flavones, acacetin and chrysin, are able to specifically alleviate TPE in human cells. We further investigated their influence on telomere integrity and showed that both drugs drastically deprotect telomeres against DNA damage response. However, telomere deprotection triggered by shelterin dysfunction does not affect TPE, indicating that acacetin and chrysin target several functions of telomeres. These results show that TPE-based screening assays represent valuable methods to discover new compounds targeting telomeres.

A Dual Role for UVRAG in Maintaining Chromosomal Stability Independent of Autophagy

Autophagy defects have recently been associated with chromosomal instability, a hallmark of human cancer. However, the functional specificity and mechanism of action of autophagy-related factors in genome stability remain elusive. Here we report that UVRAG, an autophagic tumor suppressor, plays a dual role in chromosomal stability, surprisingly independent of autophagy. We establish that UVRAG promotes DNA double-strand-break repair by directly binding and activating DNA-PK in nonhomologous end joining. Disruption of UVRAG increases genetic instability and sensitivity of cells to irradiation. Furthermore, UVRAG was also found to be localized at centrosomes and physically associated with CEP63, an integral component of centrosomes. Disruption of the association of UVRAG with centrosomes causes centrosome instability and aneuploidy. UVRAG thus represents an autophagy-related molecular factor that also has a convergent role in patrolling both the structural integrity and proper segregation of chromosomes, which may confer autophagy-independent tumor suppressor activity.

Surrogate tissue telomere length and cancer risk: Shorter or Longer?

Telomeres play a critical role in chromosome stability. Telomere length (TL) shortening is a risk factor for cancers. Measuring TL in surrogate tissues that can be easily collected may provide a potential tool for early detection of cancers. A number of studies on surrogate tissue TL and cancer risks have been conducted and results are inconsistent, including positive, negative, or null associations. In this article, we reviewed the published data on surrogate tissue TL in relation to cancer risks, discussed the possible reasons for the differences in the results and future directions and challenges for this line of research.

Satellite 2 demethylation induced by 5-azacytidine is associated with missegregation of chromosomes 1 and 16 in human somatic cells

Satellite sequences are an important part of the pericentromeric regions in mammalian genomes; they play a relevant role in chromosome stability and DNA hypomethylation of these sequences has been reported in ICF syndrome and in some cancers that are closely associated with chromosomal abnormalities. Epigenetic modifications of satellite sequences and their consequences have not been extensively studied in human cells. In the present work, we evaluated satellite 2 methylation patterns in human lymphocytes exposed to 5-azacytidine (5-azaC) and assessed the relationship between these patterns and chromosome missegregation. Human lymphocytes were exposed to 10μM 5-azaC for 24, 48, and 72h. Segregation errors were evaluated in binucleate cells using FISH against pericentromeric regions of chromosomes 1, 9, and 16. DNA methylation patterns were evaluated by immunodetection, and by bisulfite plus urea conversion and sequencing. We have identified that 5-azaC induced missegregation of chromosomes 1 and 16, which have highly methylated satellite 2, after 72h of exposure. Chromosome methylation patterns showed a notable decrease in pericentromeric methylation. Bisulfite conversion and sequencing analysis demonstrated demethylation of satellite 2 associated to 5-azaC exposure, principally after 72h of treatment. This change occurred in a non-specific pattern. Our study demonstrates an association between loss of satellite 2 DNA methylation and chromosome loss in human lymphocytes.

A prospective study of telomere length measured by monochrome multiplex quantitative PCR and risk of lung cancer

Purpose Telomere length plays an important role in chromosomal stability and tumorigenesis, and its measurement in peripheral white blood cell DNA may be a predictor of the development of lung cancer. Experimental design Using a new method – monochrome multiplex quantitative PCR – which reduces measurement variability, we compared telomere length relative to standard DNA in white blood cell DNA in 229 incident male lung cancer cases and 229 matched controls within the prospective Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study of male smokers. Results Median (10th, 90th percentile) telomere length was 1.13 (0.86, 1.45) in cases and 1.08 (0.85, 1.38) in controls ( P = 0.038). Telomere length was inversely associated with pack-years of smoking (Spearman's correlation r = −0.16, P = 0.02) among controls. Compared to subjects with shorter telomere length (≤median), subjects with greater telomere length (>median) had a 1.6-fold (95% CI, 1.06–2.36) increased risk of lung cancer. There was a significant linear relationship between quartiles of telomere length and risk of lung cancer (odds ratios (95% confidence intervals) by quartile: 1.00, 0.98 (0.55–1.73), 1.62 (0.95–2.77), and 1.50 (0.84–2.68); P trend = 0.05). In addition, subgroup analysis showed that greater telomere length was associated with an increased risk of lung cancer among longer-term smokers (>38 years) (OR, 1.90; 95% CI, 1.00–3.59) but not among shorter-term smokers (≤38 years) (OR, 1.08; 95% CI, 0.56–2.11) ( P interaction = 0.01). Conclusions Our results suggest that greater telomere length may be associated with higher risk of lung cancer among male smokers.