Role of telomeres and telomerase in the pathogenesis of human cancer

Complete analysis of G-quadruplex forming sequences in the gapless assembly of human chromosome Y

Recent advancements have finally delivered a complete human genome assembly, including the elusive Y chromosome. This accomplishment closes a significant knowledge gap. Prior efforts were hampered by challenges in sequencing repetitive DNA structures such as direct and inverted repeats. We used the G4Hunter algorithm to analyze the presence of G-quadruplex forming sequences (G4s) within the current human reference genome (GRCh38) and the new telomere-to-telomere (T2T) Y chromosome assemblies. This analysis served a dual purpose: identifying the location of potential G4s within the genomes and exploring their association with functionally annotated sequences. Compared to GRCh38, the T2T assembly exhibited a significantly higher prevalence of G-quadruplex forming sequences. Notably, these repeats were abundantly located around precursor RNA, exons, genes, and within protein binding sites. This remarkable co-occurrence of G4-forming sequences with these critical regulatory regions suggests their role in fundamental DNA regulation processes. Our findings indicate that the current human reference genome significantly underestimated the number of G4s, potentially overlooking their functional importance.

High-throughput single telomere analysis using DNA microarray and fluorescent in situ hybridization

The human telomere system is highly dynamic. Both short and long leucocyte average telomere lengths (aTL) are associated with an increased risk of cancer and early death, illustrating the complex relationship between TL and human health and the importance of assessing TL distributions with single TL analysis. A DNA microarray and telomere fluorescent in situ hybridization (DNA-array-FISH) approach was developed to measure the base-pair (bp) lengths of single telomeres. On average 32000 telomeres were measured per DNA sample with one microarray chip assaying 96 test DNA samples. Various telomere parameters, i.e. aTL and the frequency of short/long telomeres, were computed to delineate TL distribution. The intra-assay and inter-assay coefficient of variations of aTL ranged from 1.37% to 3.98%. The correlation coefficient (r) of aTL in repeated measurements ranged from 0.91 to 1.00, demonstrating high measurement precision. aTLs measured by DNA-array-FISH predicted aTLs measured by terminal restriction fragment (TRF) analysis with r ranging 0.87-0.99. A new accurate and high-throughput method has been developed to measure the bp lengths of single telomeres. The large number of single TL data provides an opportunity for an in-depth analysis of telomere dynamics and the complex relationship between telomere and age-related diseases.

Effect and interaction of TNKS genetic polymorphisms and environmental factors on telomere damage in COEs-exposure workers

Coke oven emissions (COEs) contain many carcinogenic polycyclic aromatic hydrocarbons (PAHs). Telomere damage is an early biological marker reflecting long-term COEs-exposure. Whereas, whether the genetic variations of telomere-regulated gene TNKS have an effect on the COEs-induced telomere damage is unknown. So we detected the environmental exposure levels, relative telomere length (RTL), and TNKS genetic polymorphisms among 544 COEs-exposure workers and 238 healthy participants. We found that the RTL of the wild homozygous GG genotype in rs1055328 locus was statistically shorter compared with the CG+CC genotype for the healthy participants using covariance analysis(P = 0.008). In the Generalized linear model (GLM) analysis, TNKS rs1055328 GG could accelerate telomere shortening (P = 0.011); and the interaction between TNKS rs1055328 GG and COEs-exposure had an effect on RTL (P = 0.002). In conclusion, this study was the first to discover the role of TNKS rs1055328 locus in COEs-induced telomere damage, and proved that chromosomal damage was a combined consequence of environmental and genetic factors.

Role of mismatch repair in aging

A common feature of aging is the accumulation of genetic damage throughout life. DNA damage can lead to genomic instability. Many diseases associated with premature aging are a result of increased accumulation of DNA damage. In order to minimize these damages, organisms have evolved a complex network of DNA repair mechanisms, including mismatch repair (MMR). In this review, we detail the effects of MMR on genomic instability and its role in aging emphasizing on the association between MMR and the other hallmarks of aging, serving to drive or amplify these mechanisms. These hallmarks include telomere attrition, epigenetic alterations, mitochondrial dysfunction, altered nutrient sensing and cell senescence. The close relationship between MMR and these markers may provide prevention and treatment strategies, to reduce the incidence of age-related diseases and promote the healthy aging of human beings.

Telomerase Dysfunction in the Tumorigenesis of Genetic Disorders

Telomeres are nucleoprotein complexes present at the ends of chromosome to maintain its integrity. Telomere length is maintained by an enzyme called "telomerase". Thus, telomerase activity and telomere length are crucial for the initiation of cancer and tumors survival. Also, oxidative stress will cause DNA, protein, and/or lipid damage, which end with changes in chromosome instability, genetic mutation, and may affect cell growth and lead to cancer. Some genetic diseases such as chromosomal instability syndrome, overgrowth syndrome, and neurofibromatosis make the patients at higher risk for developing different types of cancers. Therefore, we aimed to estimate telomerase activity and oxidative stress in these patients. Blood samples were collected from 31 patients (10 with neurofibromatosis, 11 with chromosomal breakage, and 10 with overgrowth syndrome) and 12 healthy subjects. Blood hTERT mRNA was detected by real time quantitative reverse-transcription PCR (RT-qPCR). All patients were subjected to chromosomal examination and chromosome breakage study using diepoxybutane method. Moreover, serum glutathione (GSH), glutathione-s-transferase (GST) activity and nitric oxide (NO) levels were measured among the control and patients groups. Receiver operating characteristic (ROC) curve was drawn to evaluate the efficiency of telomerase activity as a biomarker for the prediction of cancer occurrence. The relative telomerase activity in neurofibromatosis patients was significantly higher than controls (P = 0.014), while it was non-significantly higher in chromosomal breakage and overgrowth patients (P = 0.424 and 0.129, respectively). NO levels in neurofibromatosis, chromosomal breakage and overgrowth patients significantly increased with respect to control (P = 0.021, 0.002, 0.050, respectively). GSH levels were non-significantly lower in neurofibromatosis and chromosomal breakage patients in comparison with the control group, while it remained unchanged in overgrowth patients. The GST activity was significantly upregulated in neurofibromatosis, chromosomal breakage and overgrowth groups in comparison with the control group (P = 0.001, 0.009, and 0.025, respectively). Chromosomal examination revealed normal karyotype in all four chromosomal breakage patients with positive diepoxybutane test. The results of the present study revealed altered telomerase activity and oxidative stress in the studied genetic disorders. More research studies with a larger number of patients are required to confirm whether this alteration is related to cancer occurrence risk or not.

IL-15 Upregulates Telomerase Expression and Potently Increases Proliferative Capacity of NK, NKT-Like, and CD8 T Cells

Interleukin-15 (IL-15) is a cytokine that has been shown to expand CD8 T cell and natural killer (NK) cell populations, and therefore has potential for potentiating adoptive immune cell therapy for cancer. Previously, IL-15 has been shown to induce proliferation of CD8 memory T cells through activation of telomerase. Here, we investigated whether telomerase is also activated during the IL-15 mediated proliferation of NK and NKT-like (CD56+CD3+) cells. We also examined the extent that each of the three signaling pathways known to be stimulated by IL-2/IL-15 (JAK-STAT, PI3K-AKT Ras-RAF/MAPK) were activated and involved in the telomerase expression in the three cell types NK, NKT, or CD8 T cells. To assess cell proliferation and doubling, peripheral blood mononuclear cells (PBMCs) or isolated NK, NKT-like or CD8 T cells were incubated with varying concentrations of IL-15 or IL-2 for 7 days. CD8 T, NK, and NKT cell expansion was determined by fluorophore-conjugated antibody staining and flow cytometry. Cell doubling was investigated using carboxyfluorescein-succinimidyl-ester (CFSE). Telomerase expression was investigated by staining cells with anti-telomerase reverse transcriptase (anti-TERT). Telomerase activity in CD56+ and CD8 T cells was also measured via Telomerase Repeat Amplification Protocol (TRAP). Analysis of cellular expansion, proliferation and TERT expression concluded that IL-15 increased cellular growth of NK, NKT, and CD8 T cells more effectively than IL-2 using low or high doses. IL-15, increased TERT expression in NK and NKT cells by up to 2.5 fold, the same increase seen in CD8 T cells. IL-2 had effects on TERT expression only at high doses (100–1000 ng/ml). Proteome profiling identified that IL-15 activated selected signaling proteins in the three pathways (JAK-STAT, PI3K-AKT, Ras-MAPK) known to mediate IL-2/IL-15 signaling, more strongly than IL-2. Evaluation by signaling pathway inhibitors revealed that JAK/STAT and PI3K/AKT pathways are important in IL-15’s ability to upregulate TERT expression in NK and NKT cells, whereas all three pathways were involved in CD8 T cell TERT expression. In conclusion, this study shows that IL-15 potently stimulates TERT upregulation in NK and NKT cells in addition to CD8 T cells and is therefore a valuable tool for adoptive cell therapies.

Telomere attrition and dysfunction: a potential trigger of the progeroid phenotype in nijmegen breakage syndrome

Background: Nibrin, as part of the NBN/MRE11/RAD50 complex, is mutated in Nijmegen breakage syndrome (NBS), which leads to impaired DNA damage response and lymphoid malignancy.

Results: Telomere length (TL) was markedly reduced in homozygous patients (and comparably so in all chromosomes) by ~40% (qPCR) and was slightly reduced in NBS heterozygotes older than 30 years (~25% in qPCR), in accordance with the respective cancer rates. Humanized cancer-free NBS mice had normal TL. Telomere elongation was inducible by telomerase and/or alternative telomere lengthening but was associated with abnormal expression of telomeric genes involved in aging and/or cell growth. Lymphoblastoid cells from NBS patients with long survival times (>12 years) displayed the shortest telomeres and low caspase 7 activity.

Conclusions: NBS is a secondary telomeropathy. The two-edged sword of telomere attrition enhances the cancer-prone situation in NBS but can also lead to a relatively stable cellular phenotype in tumor survivors. Results suggest a modular model for progeroid syndromes with abnormal expression of telomeric genes as a molecular basis.

Methods: We studied TL and function in 38 homozygous individuals, 27 heterozygotes, one homozygous fetus, six NBS lymphoblastoid cell lines, and humanized NBS mice, all with the same founder NBN mutation: c.657_661del5.

Prognostic Value of Peripheral Blood Lymphocyte Telomere Length in Gynecologic Malignant Tumors

Background: Lymphocyte telomere length is strongly correlated with patient prognosis in several malignant tumor types and is thought to be related to tumor immunity. However, this correlation has not been studied in gynecological cancers. We determined the prognostic significance of peripheral blood lymphocyte telomere length in gynecologic cancers. Methods: Telomere length of lymphocytes from patients with gynecological malignant tumors (ovarian cancer (OC), N = 72; cervical cancer (CC), N = 63; endometrial cancer (EC), N = 87) was examined by quantitative reverse-transcription PCR of isolated mononuclear cells. Kaplan–Meier and Cox proportional hazard analyses were used to determine the association between lymphocyte telomere length and clinicopathological factors. Results: The overall survival (OS) and progression-free survival (PFS) of patients were based on the dichotomized lymphocyte telomere length using the median as a threshold (OC: 0.75, CC: 1.94, and EC: 1.09). A short telomere length was significantly correlated with residual tumors (≥1 cm) in OC and with advanced stage (III and IV) of CC. In OC and CC, patients with shorter relative lymphocyte telomere length (RLT) had significantly poorer OS and PFS than patients with longer RLT (p = 0.002, p = 0.003, and p = 0.001, p = 0.001, respectively). However, in EC, RLT was not significantly associated with OS or PFS (p = 0.567 and p = 0.304, log-rank test). Multivariate analysis showed that shorter RLT was a significant independent prognostic factor of PFS and OS for OC (p = 0.03 and p = 0.04, respectively) and CC (p = 0.02 and p = 0.03, respectively). Conclusions: Patients with OC and CC with shorter lymphocyte telomeres have significantly reduced survival; therefore, the peripheral blood lymphocyte telomere length is a prognostic biomarker in OC and CC.

Prospects for the involvement of cancer stem cells in the pathogenesis of osteosarcoma

Osteosarcoma (OS) is one of the most common bone tumors in children and adolescents that cause a high rate of mortality in this age group and tends to be metastatic, in spite of chemotherapy and surgery. The main reason for this can be returned to a small group of malignant cells called cancer stem cells (CSCs). OS-CSCs play a key role in the resistance to treatment and relapse and metastasis through self-renewal and differentiation abilities. In this review, we intend to go through the different aspects of this malignant disease, including the cancer stem cell-phenotype, methods for isolating CSCs, signaling pathways, and molecular markers in this disease, and drugs showing resistance in treatment efforts of OS.

APE1 deficiency promotes cellular senescence and premature aging features

Base excision repair (BER) handles many forms of endogenous DNA damage, and apurinic/apyrimidinic endonuclease 1 (APE1) is central to this process. Deletion of both alleles of APE1 (a.k.a. Apex1) in mice leads to embryonic lethality, and deficiency in cells can promote cell death. Unlike most other BER proteins, APE1 expression is inversely correlated with cellular senescence in primary human fibroblasts. Depletion of APE1 via shRNA induced senescence in normal human BJ fibroblasts, a phenotype that was not seen in counterpart cells expressing telomerase. APE1 knock-down in primary fibroblasts resulted in global DNA damage accumulation, and the induction of p16^INK4a and p21^WAF1 stress response pathways; the DNA damage response, as assessed by γ-H2AX, was particularly pronounced at telomeres. Conditional knock-out of Apex1 in mice at post-natal day 7/12 resulted in impaired growth, reduced organ size, and increased cellular senescence. The effect of Apex1 deletion at post-natal week 6 was less obvious, other than cellular senescence, until ∼8-months of age, when premature aging characteristics, such as hair loss and impaired wound healing, were seen. Low APE1 expression in patient cancer tissue also correlated with increased senescence. Our results point to a key role for APE1 in regulating cellular senescence and aging features, with telomere status apparently affecting the outcome.

Serum Level of Total Lipids and Telomere Length in the Male Population: A Cross-Sectional Study

Telomeres contain TTAGGG (T; Thymine, A; Adenine and G; Guanine) repetitive sequences and are placed at the end of human chromosomes. Telomere dysfunction is implicated in some age-related and chronic diseases, but its association with total serum lipids and obesity is unknown. Our objective was to determine influenced of total serum lipids on leukocyte telomere lengths (TLs). Participants were selected by cluster sampling from 22 districts of Tehran. The questionnaires were completed by 500 subjects and after the initial assessment in terms of lifestyle, nutrition, home, and job, 300 healthy people, aged 25-40 years were finally selected. TLs and serum level of total lipids were measured by quantitative real-time PCR and the Phillips method, respectively. The average telomere length (T/S) and total lipids were 1.05 ± 0.3 mg/dl and 643.3 ± 70.8 mg/dl, respectively. We found that a one unit difference in the following parameters were associated with kilo base pair differences in TL: Age -0.0002 (95% CI [-0.0022, -0.0018]), BMI -0.0019 (95% CI [-0.0003, -0.0034]), TC 0.0001 (95% CI [-0.0006, -0.0007]), TG -0.0010 (95% CI [-0.0015, -0.0004]), PL 0.0001 (95% CI [-0.0005, -0.0007]), and TSL -0.0003 (95% CI [-0.0008, 0.0001]). Spearman correlation analysis revealed an inverse relationship between TC (R = -0.53; 95% CI [-0.61, -0.44]), TG (R = -0.50; 95% CI [-0.58, -0.41]), PL (R = -0.46; 95% CI [-0.54-0.36]), and TSL (R = -0.63; 95% CI [-0.69, -0.56]) with T/S. Our research suggests that the inverse relationship was found between TL and weight, BMI, age, and TSL which were associated with obesity. High serum lipids concentration may be associated with systemic inflammation and atherosclerosis and may lead to oxidative stress, resulting in telomere shortening.

Autophagy induction reduces telomerase activity in HeLa cells

Autophagy is a cellular homeostatic process whereby damaged proteins and organelles are encapsulated into double membrane vesicles, called autophagosomes, for lysosomal digestion. Beclin1 plays a key role in the initial steps of autophagosome formation. In this study, we evaluated the effect of Beclin 1 overexpression in induction of autophagy and the relationship between autophagy induction and telomerase activity in HeLa cells. We found that overexpression of Beclin 1 in HeLa cells leads to autophagosome formation as shown by intracellular autophagosomal marker LC3-II staining. Expression of Beclin1 reduced telomerase activity for about 100 fold compared with the control while it did not affect TERT expression level. The results of cell cycle analysis indicated that the cell cycle and proliferation progressed normally up to 48h post-transfection. Understanding the role of autophagy induction and telomerase in the pathophysiology of aging and human cancer reveal new strategies that hold much promise for intervention and therapeutic uses.

Overcoming Therapeutic Resistance of Bone Sarcomas: Overview of the Molecular Mechanisms and Therapeutic Targets for Bone Sarcoma Stem Cells

Bone sarcomas are heterogeneous malignant tumors that exhibit clinical, histological, and molecular heterogeneity. Recent progress in their multimodal treatment has gradually improved patient prognosis; however, drug resistance and distant metastasis remain unresolved clinical problems. Recent investigations have suggested the existence of cancer stem-like cells (CSCs) in bone sarcomas, which represent a subpopulation of tumor cells with high tumor-forming ability. The hallmarks of CSCs include tumor- and metastasis-forming potential and drug resistance, which are responsible for poor prognoses of bone sarcoma patients. Therefore, elucidation of the molecular mechanisms of CSCs and identification of therapeutic targets could contribute to novel treatment strategies for bone sarcomas and improve patient prognosis. This paper provides an overview of the accumulating knowledge on bone sarcoma stem cells and preclinical analyses to overcome their lethal phenotypes, in addition to a discussion of their potential for novel therapeutics for bone sarcomas.

Impaired telomere length and telomerase activity in peripheral blood leukocytes and granulosa cells in patients with biochemical primary ovarian insufficiency

STUDY QUESTION

Are telomere length and telomerase activity associated with biochemical primary ovarian insufficiency (POI)?

SUMMARY ANSWER

Shortened telomere length and diminished telomerase activity were associated with biochemical POI.

WHAT IS KNOWN ALREADY

POI is a result of pathological reproductive aging and encompasses occult, biochemical and overt stages. Studies have indicated telomere length as a biomarker for biological aging.

STUDY DESIGN, SIZE, DURATION

A total of 120 patients with biochemical POI and 279 control women were recruited by the Center for Reproductive Medicine of Shandong University.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Telomere length in peripheral blood leukocytes (LTL) and granulosa cells (GTL) was measured using a modified Quantitative Polymerase Chain Reaction technique. The relative telomerase activity (RTA) in granulosa cells was detected using a modified quantitative-telomeric repeat amplification protocol assay.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjusting for age, patients with biochemical POI (n = 120) exhibited significantly shorter LTLs (0.75 ± 0.09 vs 1.79 ± 0.12, P < 0.001; OR = 0.54, 95% CI = 0.43-0.68) and GTLs (0.78 ± 0.09 vs 1.90 ± 0.23, P < 0.001; OR = 0.54, 95% CI = 0.41-0.70) than the controls (n = 279 for LTLs; n = 90 for GTLs). Significantly diminished RTAs in granulosa cells were detected in patients with biochemical POI (n = 31) compared with the controls (n = 38) (1.57 ± 0.59 vs 4.63 ± 0.93, P = 0.025; OR = 0.84, 95% CI = 0.72-0.98).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The cross-sectional nature of this study might have its limit in telomere length as well as telomerase activity along with the progressing decline in ovarian function.

WIDER IMPLICATIONS OF THE FINDINGS

These findings suggest that telomere length and telomerase activity may be considered as indicators for progression of ovarian decline.

STUDY FUNDING/COMPETING INTERESTS

This research was supported by the National Basic Research Program of China (973 Program) (2012CB944700), Science research foundation item of no-earnings health vocation (201402004) and the National Natural Science Foundation of China (31471352, 81270662, 81471509, 81300461, 81522018). The authors have no potential conflict of interest to declare.

Differences in telomere length between sporadic and familial cutaneous melanoma

BACKGROUND

Several pieces of evidence indicate that a complex relationship exists between constitutional telomere length (TL) and the risk of cutaneous melanoma. Although the general perception is that longer telomeres increase melanoma risk, some studies do not support this association. We hypothesize that discordant data are due to the characteristics of the studied populations.

OBJECTIVES

To evaluate the association of TL with familial and sporadic melanoma.

MATERIALS AND METHODS

TL was measured by multiplex quantitative polymerase chain reaction in leukocytes from 310 patients with melanoma according to familial/sporadic and single/multiple cancers and 216 age-matched controls.

RESULTS

Patients with sporadic melanoma were found to have shorter telomeres compared with those with familial melanoma. In addition, shorter telomeres, while tending to reduce the risk of familial melanoma regardless of single or multiple tumours, nearly trebled the risk of single sporadic melanoma.

CONCLUSIONS

This is the first time that TL has been correlated to opposite effects on melanoma risk according to the presence or absence of familial predisposition. Individual susceptibility to melanoma should be taken into account when assessing the role of TL as a risk factor.

The association between telomere length and cancer risk in population studies

Telomeres are crucial in the maintenance of chromosome integrity and genomic stability. A series of epidemiological studies have examined the association between telomere length and the risk of cancers, but the findings remain conflicting. We performed literature review and meta-analysis to demonstrate the relationship between telomere length and cancer risk. A total of 23,379 cases and 68,792 controls from 51 publications with 62 population studies were included in this meta-analysis to assess the association between overall cancer or cancer-specific risk and telomere length. General association and dose-response relationship were evaluated based on two and three groups, respectively. The estimates of association were evaluated with odds ratios and 95% confidence intervals by the random-effects or fixed-effects model based on heterogeneity test. We observed a non-significant association between short telomeres and overall risk of cancer. Convincing evidence was observed for the association of short telomeres with an increased risk of gastrointestinal tumor and head and neck cancer. Significant dose-response associations were also observed for gastrointestinal tumor and head and neck cancer. Our findings indicate that telomeres may play diverse roles in different cancers, and short telomeres may be risk factors for the tumors of digestive system.

Transgenic rat model of childhood-onset dermatitis by overexpressing telomerase reverse transcriptase (TERT)

Childhood-onset dermatitis is one of the most common skin disorders in children. Although various mouse models that mirror aspects of dermatitis have become available, there is still a need for an animal model that develops dermatitis in childhood and is more suitable for performing tissue transplantation experiments. There is emerging evidence that peripheral blood T lymphocytes from patients with dermatitis have significantly increased telomerase activity. Here, we developed telomerase reverse transcriptase (TERT)-expressing transgenic (Tg) rats that spontaneously developed eczematous skin inflammation in childhood. Newborn TERT-Tg rats developed visible dermatitis in 56 % of cases, and the skin lesions microscopically showed spongiosis and acanthosis with infiltration of lymphocytes, eosinophils and mast cells. TERT-Tg rats with dermatitis exhibited increased CD4 (2.5-fold) and CD8 (fivefold) T cell numbers compared with dermatitis-free TERT-Tg rats. Stronger TERT activity was observed in the peripheral lymphocytes of dermatitis-positive TERT-Tg rats than those of dermatitis-free TERT-Tg rats. RT-PCR analysis revealed that IL-4 was markedly elevated in the spleen of dermatitis-positive TERT-Tg rats, and that interferon-gamma was increased in the dermatitis lesions. Moreover, skin grafting of TERT-Tg rats with dermatitis onto T cell-deficient nude rats demonstrated that the inflamed skin lesions could not be maintained. Taken together, the results suggest that TERT activation in T lymphocytes is one of the potential predisposing factors for dermatitis. Moreover, our results demonstrated that the TERT-Tg rats mirror aspects of human childhood-onset dermatitis and that these animals represent a potential animal model system for studying childhood-onset dermatitis.

Association of leukocyte telomere length in peripheral blood leukocytes with endometrial cancer risk in Caucasian Americans

Telomeres are the protective structure at the ends of each chromosome and play an important role in maintaining genomic integrity. Interindividual variation of telomere length in peripheral blood leukocytes has been associated with the risks of developing many human diseases including several cancers. The association between leukocyte telomere length (LTL) and endometrial cancer risk is still inconsistent. Using a case-control study of endometrial cancer patients (n = 139) and control subjects (n = 139) in a Caucasian population, we assessed the association of relative LTL with the risk of endometrial cancer. We calculated odds ratios and 95% confidence intervals using multivariate logistic regression. We also determined the joint effects of LTL with established risk factors of endometrial cancer. The normalized LTL was significantly longer in endometrial cancer cases (median, 0.93; range, 0.19-1.62) than in controls (median, 0.70; range, 0.03-2.14) (P < 0.001). When individuals were dichotomized into long and short groups based on the median LTL value in the controls, individuals with long LTL had a significantly increased risk of endometrial cancer (adjusted OR, 3.84; 95%CI, 2.16-6.85; P < 0.001) compared to those with short LTL. When individuals were categorized into three groups or four groups according to tertile or quartile LTL value in the controls, there was a significant dose-response association between LTL and the risk of endometrial cancer (P < 0.001). Joint effects between LTL and smoking status, body mass index and a history of hypertension or diabetes in elevating endometrial cancer risk were observed. Long telomere length in peripheral blood leukocytes is associated with a significantly increased risk of endometrial cancer.

Smoking habits and leukocyte telomere length dynamics among older adults: Results from the ESTHER cohort

BACKGROUND & AIMS

Leukocyte telomere length (LTL) shortens with age and short LTL has been associated with increased mortality and increased risk for some age-related outcomes. This study aims to analyse the associations of smoking habits with LTL and rate of LTL change per year in older adults.

METHODS

LTL was measured by quantitative PCR at baseline in 3600 older adults, who were enrolled in a population-based cohort study in Germany. For longitudinal analyses, measurements were repeated in blood samples obtained at 8-year follow-up from 1000 participants. Terminal Restriction Fragment analysis was additionally performed in a sub-sample to obtain absolute LTL in base pairs. Multivariate linear regression models were used to estimate associations of smoking habits with baseline LTL and changes in LTL over time.

RESULTS

LTL was inversely associated with age (r=-0.090, p<0.0001). Women had longer LTL than men (p<0.0001). Smoking was inversely associated with LTL. On average, current smokers had 73 base pairs (BP) shorter LTL compared to never smokers. Smoking intensity and pack-years of smoking were also inversely associated with LTL, and a positive association was observed with years since smoking cessation. Slower LTL attrition rates were observed in ever smokers over 8years of follow-up.

CONCLUSIONS

Our cross-sectional analysis supports suggestions that smoking might contribute to shortening of LTL but this relationship could not be shown longitudinally. The overall rather small effect sizes observed for smoking-related variables suggest that LTL reflects smoking-related health hazards only to a very limited extent.

The relationship between telomere length and clinicopathologic characteristics in colorectal cancers among Tunisian patients

Alterations in telomere dynamics have emerged as having a causative role in carcinogenesis. Both the telomere attrition contribute to tumor initiation via increasing chromosomal instability and that the telomere elongation induces cell immortalization and leads to tumor progression. The objectives of this study are to investigate the dynamics of telomere length in colorectal cancer (CRC) and the clinicopathological parameters implicated. We measured the relative telomere length (RTL) in cancerous tissues and in corresponding peripheral blood leukocytes (PBL) using quantitative PCR (Q-PCR) from 94 patients with CRC. Telomere length correlated significantly in cancer tissues and corresponding PBL (r = 0.705). Overall, cancer tissue had shorter telomeres than PBL (p = 0.033). In both cancer tissue and PBL, the RTL was significantly correlated with age groups (p = 0.008 and p = 0.012, respectively). The RTL in cancer tissue was significantly longer in rectal tumors (p = 0.04) and in the late stage of tumors (p = 0.01). In PBL, the RTL was significantly correlated with the macroscopic aspect of tumors (p = 0.02). In addition, the telomere-length ratio of cancer to corresponding PBL increased significantly with late-stage groups. Shortening of the telomere was detected in 44.7%, elongation in 36.2%, and telomeres were unchanged in 19.1% of 94 tumors. Telomere shortening occurred more frequently in the early stage of tumors (p = 0.01). This study suggests that the telomere length in PBL is affected by the macroscopic aspect of tumors and that telomere length in cancer tissues is a marker for progression of CRC and depends on tumor-origin site.

Prognostic value of telomere function in gastric cancers with and without microsatellite instability

OBJECTIVE

To identify molecular markers that may be useful in the selection of gastric cancer patients with different prognoses, we investigated telomere function in gastric cancers with and without microsatellite instability (MSI).

MATERIALS AND METHODS

We analyzed 83 gastric cancers and its paired-normal tissues to investigate MSI and telomere function. MSI was established using five polymorphic human repeat DNA markers. Telomere function was evaluated by determining telomerase activity, telomere length, and telomere-repeat factors 1 and 2 (TRF1 and TRF2) expression.

RESULTS

Patients with high microsatellite instability (MSI-H) gastric cancers showed a significantly better prognosis than those affected by microsatellite stable or low microsatellite instability (MSS/MSI-L) tumors (P = 0.03). The lowest expression levels of TRF1 and TRF2 were associated with MSI-H gastric cancers (P = 0.008 and 0.006, respectively). Moreover, a clear trend toward a worse prognosis was found in the group of patients who had tumors with the shortest telomeres (P = 0.01). Cox multivariate analysis showed that MSI emerged as a protective prognostic factor; MSS/MSI-L tumors conferred a significantly poor prognosis in patients (relative risk = 4.862-fold greater than the MSI-H group) (P = 0.033). Telomere length of gastric tumors less than 2.86 kbp was a factor that led to a poor prognosis (relative risk = 4.420, with respect to tumors showing telomere length ≥ 2.86 kbp) (P = 0.002).

CONCLUSION

We propose telomere status as a potential molecular marker with usefulness in the establishment of the prognosis of gastric cancers both for the mutator phenotype and for the suppressor pathway.

Transcriptome analysis reveals molecular profiles associated with evolving steps of monoclonal gammopathies

A multistep model has been proposed of disease progression starting in monoclonal gammopathy of undetermined significance continuing through multiple myeloma, sometimes with an intermediate entity called smoldering myeloma, and ending in extramedullary disease. To gain further insights into the role of the transcriptome deregulation in the transition from a normal plasma cell to a clonal plasma cell, and from an indolent clonal plasma cell to a malignant plasma cell, we performed gene expression profiling in 20 patients with monoclonal gammopathy of undetermined significance, 33 with high-risk smoldering myeloma and 41 with multiple myeloma. The analysis showed that 126 genes were differentially expressed in monoclonal gammopathy of undetermined significance, smoldering myeloma and multiple myeloma as compared to normal plasma cell. Interestingly, 17 and 9 out of the 126 significant differentially expressed genes were small nucleolar RNA molecules and zinc finger proteins. Several proapoptotic genes (AKT1 and AKT2) were down-regulated and antiapoptotic genes (APAF1 and BCL2L1) were up-regulated in multiple myeloma, both symptomatic and asymptomatic, compared to monoclonal gammopathy of undetermined significance. When we looked for those genes progressively modulated through the evolving stages of monoclonal gammopathies, eight snoRNA showed a progressive increase while APAF1, VCAN and MEGF9 exhibited a progressive downregulation. In conclusion, our data show that although monoclonal gammopathy of undetermined significance, smoldering myeloma and multiple myeloma are not clearly distinguishable groups according to their gene expression profiling, several signaling pathways and genes were significantly deregulated at different steps of the transformation process.

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 shortening: a biological marker of sporadic colorectal cancer with normal expression of p53 and mismatch repair proteins

Uncontrolled growth of cells, a main criterion of cancer, is merged with pathologic telomere length alteration. Thereby, measurement of telomere length could provide important information on cell proliferation and senescence in cancer tissues. Telomere shortening and its potential correlation with clinicopathological predictive markers in sporadic colorectal cancer (CRC) with normal expression of mismatch repair (MMR) proteins (including Mlh1, Msh2, Pms2, and Msh6) and normal p53 expression was completely explored. Relative telomere length (RTL) was quantitatively measured in a cohort of 164 samples (68 patients with sporadic CRC and 96 healthy unrelated controls). Our results demonstrated a significant shortening of RTL in the tumor-derived tissue of patients compared with the control group (p<0.001). Interestingly, significant telomere shortening was observed in tumors from an ascending and sigmoid colon in comparison with tumors located in a descending colon. Additionally, the telomere length was significantly shorter in those with lymph node metastasis (p<0.05). The results suggest that pathological telomere shortening, leading to genome instability and lymphatic transformation, could serve as a potential sensitive detection and also as a classification marker for facilitating diagnosis and management of CRC.

Enrichment of human osteosarcoma stem cells based on hTERT transcriptional activity

Telomerase is crucial for the maintenance of stem/progenitor cells in adult tissues and is detected in most malignant cancers, including osteosarcoma. However, the relationship between telomerase expression and cancer stem cells remains unknown. We observed that sphere-derived osteosarcoma cells had higher telomerase activity, indicating that telomerase activity might be enriched in osteosarcoma stem cells. We sorted subpopulations with high or low telomerase activity (TEL) using hTERT transcriptional promoter-induced green fluorescent protein (GFP). The TELpos cells showed an increased sphere and tumor propagating capacity compared to TELneg cells, and enhanced stem cell-like properties such as invasiveness, metastatic activity and resistance to chemotherapeutic agents both in vitro and in vivo. Furthermore, the telomerase inhibitor MST312 prevented tumorigenic potential both in vitro and in vivo, preferentially targeting the TELpos cells. These data support telomerase inhibition as a potential targeted therapy for osteosarcoma stem-like cells.

Impact of Hepatitis C Virus (HCV) infection on biomolecular markers influencing the pathogenesis of bladder cancer

Objective

The present study was designed to determine the possible impact of hepatitis C virus (HCV) infection on the expression of telomerase (TERT), retinoblastoma (RB1), E2F3, TP53, CDKN1A (p21) and fibroblast growth factor receptor- 3 (FGFR3) genes in patients with bladder cancer (BC).

Materials and methods

100 patients with bladder cancer (15 female and 85 male) were divided into 2 groups; Group I: 50 HCV negative subjects (age range 36–79), and Group II: 50 HCV positive subjects (age range 42–80). Expressions of the telomerase, retinoblastoma (Rb), E2F3, TP53 and FGFR3 genes were tested by immunohistochemistry and real time PCR in tumour tissues and healthy bladder tissues. Also, telomerase activity was assessed by telomeric repeats amplification protocol (TRAP).

Results

Bladder tumors associated with HCV infection were of high grade and invasive squamous cell carcinomas (SCCs). Expressions of hTERT, Rb, E2F3, TP53 and FGFR3 as well as telomerase activity were significantly higher in bladder tissues of HCV-infected patients compared with bladder tissues of non infected patients (p<0.05). On the contrary, CDKN1A (p21) expression was significantly lower in bladder tissues of HCV-infected patients compared to bladder tissues of non infected patients (p<0.05).

Conclusion

The expressions of hTERT, Rb, E2F3, TP53 and FGFR3 as well as the activity of telomerase were significantly high in malignant bladder tissues associated with HCV infection. On the other hand, CDKN1A (p21) expression was low in bladder tissues of HCV-infected subjects. Moreover, there was a positive correlation between HCV infection and expression of telomerase, E2F3, TP53 and FGFR3. There was a negative correlation between HCV infection and expression of Rb and p21.

Telomere, aging and age-related diseases

Aging is an inevitable biological process that affects most living organisms. The process of aging is regulated at the level of the organism, as well as at the level of tissues and cells. Despite the enormous consequences associated with the aging process, relatively little systematic effort has been expended on the scientific understanding of this important life process. Many theories have been proposed to explain the aging process, the centerpiece of which is molecular damage. Located at the ends of eukaryotic chromosomes and synthesized by telomerase, telomeres maintain the stabilization of chromosomes. Thus, the loss of telomeres may lead to DNA damage. The relationship between cellular senescence and telomere shortening is well established. Furthermore, telomere attrition occurs with age, and is proposed to be a fundamental factor in the aging process. Here, we review the contemporary literatures to explore the current views on the correlation of telomere loss and telomerase action with aging and age-related diseases.

Overexpression of hTERT in potentially malignant colorectal laterally spreading tumors

Human telomerase reverse transcriptase (hTERT) is the main subunit of the core enzyme telomerase, which consists of three subunits. Telomeres are essential for chromosomal stability and integrity, protecting the ends of chromosomes from degradation and preventing chromosomal end fusions and recombination. A loss of telomere function is a major mechanism for the generation of chromosomal abnormalities. Telomere shortening leads to mutations, chromosome rearrangements and translocations. Colorectal laterally spreading tumors (LSTs) are a special type of superficial colorectal tumor. They are considered to have a high malignancy potential. The aim of the present study was to characterize the expression of hTERT in an LST cell line and paraffin sections. Immunohistochemistry was utilized to examine the protein expression of hTERT in the LST cell line, 48 resected LSTs, 48 protruded-type colorectal adenomas (PAs) and 48 normal mucosa samples. Statistical analyses were applied to test the associations between hTERT expression and clinicopathological parameters. The present study demonstrated that the positive expression levels of hTERT in LSTs, PAs and normal mucosa were 60.4, 22.9 and 10%, respectively. Compared with polypi and normal mucosa, the expression levels of hTERT were significantly increased in LSTs. The expression of hTERT was also observed in the LST cell line. The expression of hTERT was significantly higher in LSTs, which may indicate a potential for malignancy.

What is recent in pancreatic cancer immunotherapy?

Pancreatic cancer (PC) represents an unresolved therapeutic challenge, due to the poor prognosis and the reduced response to currently available treatments. Pancreatic cancer is the most lethal type of digestive cancers, with a median survival of 4-6 months. Only a small proportion of PC patients is curative by surgical resection, whilst standard chemotherapy for patients in advanced disease generates only modest effects with considerable toxic damages. Thus, new therapeutic approaches, specially specific treatments such as immunotherapy, are needed. In this paper we analyze recent preclinical and clinical efforts towards immunotherapy of pancreatic cancer, including passive and active immunotherapy approaches, designed to target pancreatic-cancer-associated antigens and to elicit an antitumor response in vivo.

Telomere length of tumor tissues and survival in patients with early stage non-small cell lung cancer

Telomere shortening leads to genomic instability that drives oncogenesis through the activation of telomerase and the generation of other mutations necessary for tumor progression. This study was conducted to determine the impact of telomere shortening on the survival of patients with early stage non-small cell lung cancer (NSCLC). Relative telomere length in tumor tissues was measured by quantitative polymerase chain reaction in 164 patients with surgically resected NSCLC. The association between telomere length and overall survival (OS) and disease-free survival (DFS) was analyzed. When the patients were categorized into quartiles based on telomere length, those patients with the 1st quartile (shortest) of telomere length had a significantly worse OS and DFS compared to patients with the 2nd to the 4th quartiles of telomere length (adjusted hazard ratio for OS = 2.67, 95% confidence interval = 1.50-4.75, P = 0.001; and adjusted hazard ratio for DFS = 1.92, 95% confidence interval = 1.17-3.14, P = 0.01). An association between telomere length and survival outcome was more pronounced in squamous cell carcinomas than adenocarcinomas (P-value of test for homogeneity for OS and DFS = 0.05 and 0.02, respectively). Telomere length of tumor tissues is an independent prognostic factor in patients with surgically resected early stage NSCLC.

Telomere length and LINE1 methylation is associated with chromosomal aberrations in peripheral blood

The frequency of chromosomal aberrations in peripheral blood predicts a probable cancer risk. The individual telomere length and methylation of repetitive elements may be susceptibility factors for chromosomal aberrations. A cohort of healthy Norwegian men (N = 364) recruited during 1980-1999 were analyzed for chromosomal aberrations in phytohemagglutinin-stimulated lymphocytes from peripheral blood. Chromosome-type or chromatid-type aberrations were scored. DNA was extracted from slides cytogenetically analyzed and relative average telomere length and methylation of LINE1 repeats were determined by quantitative polymerase chain reaction and bisulfite pyrosequencing, respectively. Information about individuals with malignant tumors (N = 49) diagnosed after chromosomal aberrations testing until end of 2008 was obtained and two matched controls per case were used in a nested case-control analysis. Shorter relative telomere length and higher methylation of LINE1 were associated with higher frequency of total chromosomal aberrations (β = -0.76, P = 0.022; and β = 0.042, P = 0.048, respectively; age-adjusted ordinal regression). The telomere length was stronger associated with chromosome-type (β = -1.00, P = 0.006) than with chromatid-type aberrations (β = -0.49, P = 0.115). The LINE1 methylation was stronger associated with chromatid-type (β = 0.062, P = 0.003) than with chromosome-type aberrations (β = 0.018, P = 0.41). Telomere length [individuals with short telomeres odds ratio (OR) = 0.87, 95% confidence interval (CI) 0.38-2.0], LINE1 (individuals with high methylation OR = 1.04, 95% CI 0.43-2.5) and chromosomal aberrations (individuals with high frequency OR = 1.6, 95% CI 0.63-3.9) at baseline did not predict cancer risk, but the conclusions were hampered by low statistical precision. The results suggest that shorter telomere length and higher LINE1 methylation in peripheral blood lymphocytes are predisposition factors for increased frequency of chromosomal aberrations.

Telomere loss in Philadelphia-negative hematopoiesis after successful treatment of chronic myeloid leukemia: evidence for premature aging of the myeloid compartment

Telomere shortening, a well-known marker of aging and cellular stress, occurs under several conditions in the hematopoietic compartment, including aplastic anemia and following iatrogenic noxae. We decided to verify whether pathological telomere erosion also arises in restored Philadelphia-negative (Ph-negative) hematopoiesis following successful treatment of chronic myeloid leukemia (CML). Eighty-one CML patients in complete cytogenetic remission were compared to 76 age-matched healthy subjects. Myeloid cells of CML patients had shorter telomeres than controls (6521 bp vs 7233 bp, p<0.001). This difference was specific for the myeloid compartment, since it was not observed in lymphoid cells (6774 bp vs 6909 bp, p=0.620). Acquired Ph-negative cytogenetic abnormalities (p=0.010), lack of complete molecular remission (p=0.016) and age (p=0.013) were independent predictors of telomere shortening. Telomere dynamics were assessed over a median follow-up period of 22 months. We documented accelerated non-physiological ongoing telomere shortening in 17/59 CML patients (28%). Patients experiencing grade 2-4 hematological toxicity, during CML remission possessed significantly shorter telomeres compared to those lacking toxicity (p=0.005 for any toxicity, p=0.007 for anemia). CML patients suffer from significant and often ongoing telomere stress resulting in premature and selective aging of the myeloid compartment which might have long-term consequences on function and integrity of Ph-negative hematopoiesis.

Telomerase mRNA detection in serum of patients with prostate cancer

Telomerase functions as a reverse transcriptase enzyme in the process of telomere synthesis and telomerase activity have been detected in a large part of neoplastic tissues, whereas in normal somatic cells they were low or undetectable. The aim of this study was to investigate the telomerase mRNA detection in the serum of patients with a prostate tumor by using real-time reverse transcription PCR. The results were compared with biological samples obtained by age-matched normal donors and by patients with cardiovascular or metabolic diseases. Our data demonstrated that telomerase mRNA is detectable in the serum of patients with prostate cancer whereas it is not amplifiable in normal donors. This marker, assayed with the molecular method of quantitative PCR in serum, may be useful for diagnosing and monitoring prostate cancer patients.

Telomeres and telomerase in normal and malignant B-cells

The telomeric checkpoint is emerging as a critical sensor of cellular damage, playing a major role in human aging and cancer development. In the meantime, telomere biology is rapidly evolving from a basic discipline to a translational branch, capable of providing major hints for biomarker development, risk assessment and targeted treatment of cancer. These advances have a number of implications in the biology of lymphoid tumours. Moreover, there is considerable interest in the potential role of telomeric dysfunction in the wide array of immunological abnormalities, grouped under the definition of 'immunosenescence'. This review will summarize the impact of recent advances in telomere biology on the physiology and pathology of the B lymphocyte, with special interest in immunosenescence and lymphomagenesis.

Androgens stimulate telomerase expression, activity and phosphorylation in ovarian adenocarcinoma cells

Androgens have been implicated in increasing ovarian cancer risk. Most ovarian cancer cells have high telomerase activity which is effective in inducing ovarian carcinogenesis. The purpose of this study was to investigate the effects of testosterone and androstenedione on the viability of an ovarian adenocarcinoma cell line, the activity and expression of telomerase, and the phosphorylation status of its catalytic subunit in these cells. Results showed that androgens significantly increased the viability of ovarian cancer cells and that these hormones induced the expression, activity and phosphorylation of telomerase. This upregulation was blocked by phosphatidylinositol 3-kinase pathway inhibitors. These findings might have implications for understanding the role of androgens in ovarian carcinogenesis.

Donor cell leukemia: a review

Relapse of acute leukemia following hematopoietic stem cell transplantation (HSCT) usually represents return of an original disease clone, having evaded eradication by pretransplant chemo-/radiotherapy, conditioning, or posttransplant graft-versus-leukemia (GVL) effect. Rarely, acute leukemia can develop de novo in engrafted cells of donor origin. Donor cell leukemia (DCL) was first recognized in 1971, but for many years, the paucity of reported cases suggested it to be a rare phenomenon. However, in recent years, an upsurge in reported cases (in parallel with advances in molecular chimerism monitoring) suggest that it may be significantly more common than previously appreciated; emerging evidence suggests that DCL might represent up to 5% of all posttransplant leukemia "relapses." Recognition of DCL is important for several reasons. Donor-derivation of the leukemic clone has implications when selecting appropriate therapy, because seeking to enhance an allogeneic GVL effect would intuitively not have the same role as in standard recipient-derived relapses. There are also broader implications for donor selection and workup, particularly given the growing popularity of nonmyeloblative HSCT and corresponding rising age of the potential donor pool. Identification of DCL raises potential concerns over future health of the donor, posing ethical dilemmas regarding responsibilities toward donor notification (particularly in the context of cord blood transplantation). The entity of DCL is also of research interest, because it might provide a unique human model for studying the mechanisms of leukemogenesis in vivo. This review presents and collates all reported cases of DCL, and discusses the various strategies, controversies, and pitfalls when investigating origin of posttransplant relapse. Putative etiologic factors and mechanisms are proposed, and attempts made to address the difficult ethical questions posed by discovery of donor-derived malignancy within a HSCT recipient.

Expression and biological-clinical significance of hTR, hTERT and CKS2 in washing fluids of patients with bladder cancer

BACKGROUND

at present, pathogenesis of bladder cancer (BC) has not been fully elucidated. Aim of this study is to investigate the role of human telomerase RNA (hTR), human telomerase reverse transcriptase (hTERT) and CDC28 protein kinase regulatory subunit 2 (CKS2) in bladder carcinogenesis and their possible clinical significance;

METHODS

the transcript levels of hTR, hTERT and CKS2 were quantified by Real time reverse transcriptase chain reaction in exfoliated cells from bladder washings of 36 patients with BC and 58 controls. The statistical significance of differences between BC bearing patients and control groups, in the general as well as in the stratified analysis (superficial or invasive BC), was assessed by Student's t test. Non parametric Receiver Operating Characteristics analysis (ROC) was performed to ascertain the accuracy of study variables to discriminate between BC and controls. The clinical value of concomitant examination of hTR, hTERT and CKS2 was evaluated by logistic regression analysis;

RESULTS

a significant decrease in hTR and a significant increase in hTERT or CKS2 gene expression were found between BC bearing patients and controls, as well as in the subgroups analysis. The area under the curve (AUC) indicated an average discrimination power for the three genes, both in the general and subgroups analysis, when singularly considered. The ability to significantly discriminate between superficial and invasive BC was observed only for hTR transcript levels. A combined model including hTR and CKS2 was the best one in BC diagnosis;

CONCLUSIONS

our results, obtained from a sample set particularly rich of exfoliated cells, provide further molecular evidence on the involvement of hTR, hTERT and CKS2 gene expression in BC carcinogenesis. In particular, while hTERT and CKS2 gene expression seems to have a major involvement in the early stages of the disease, hTR gene expression, seems to be more involved in progression. In addition, our findings suggest that the studied genes have a clinical role in discriminating between BC and controls in the general as well as in the stratified analysis, when singularly considered. A combined model improved over the single marker BC diagnosis.

Expression of TRF1, TRF2, TIN2, TERT, KU70, and BRCA1 proteins is associated with telomere shortening and may contribute to multistage carcinogenesis of gastric cancer

PURPOSE

Telomere dysfunction is believed to be a significant factor in carcinogenesis. To elucidate the carcinogenesis mechanism in gastric cancer, the expression of telomeric proteins and changes in telomere length were investigated during multistage carcinogenesis of gastric cancer.

METHODS

Tissue samples were obtained during surgical operations from the normal gastric mucosa of 10 patients, the precancerous lesions of 15 patients, the gastric cancer tissues (GC) of 20 patients, and of tumors due to gastric cancer with lymph node metastasis (GCLM) from 5 patients. The expression of TRF1, TRF2, and TIN2 proteins was measured by Western blotting, while the expression of TERT, KU70, and BRCA1 proteins was detected using the immunohistochemical method. The mean telomere length was determined by Southern blotting.

RESULTS

Compared with normal gastric mucosa tissues, the expression of TRF1, TRF2, and TIN2 proteins was significantly higher in precancerous lesions, GC, and GCLM (P < 0.01). The expression of TRF1, TRF2, and TIN2 proteins was significantly higher in GC and GCLM than in precancerous lesions (P < 0.01). The expression of TERT and Ku70 proteins in precancerous lesions and GC tissues was significantly higher than that in normal gastric mucosa tissues (P < 0.01). The expression of TERT and Ku70 proteins in GC tissues was significantly higher than in precancerous lesions (P < 0.01). In normal gastric mucosa, the BRCA1 protein was primarily located in the cell nucleus. In precancerous lesions and GC, the expression of the BRCA1 protein was apparent in the cell cytoplasm. The mean telomere length in precancerous lesions, GC, and GCLM was significantly shorter than that in normal gastric mucosa tissues (P < 0.05). The mean telomere length in GC and GCLM was significantly shorter than that in precancerous lesions (P < 0.05). The mean telomere length in all tissue samples was inversely correlated with the level of TRF1, TRF2, TIN2, TERT, and Ku70 proteins.

CONCLUSIONS

Our results suggest that the over-expression of telomeric proteins, TRF1, TRF2, TIN2, TERT, and Ku70, and the transposition of the BRCA1 protein may work together to reduce the telomere length in precancerous lesions and gastric cancer, and could contribute to the multistage carcinogenesis of gastric cancer. These findings offer new insight into the mechanism of carcinogenesis in gastric cancer.

Irradiation-induced telomerase activity and gastric cancer risk: a case-control analysis in a Chinese Han population

BACKGROUND

Telomerase expression is one of the characteristics of gastric cancer (GC) cells and telomerase activity is frequently up-regulated by a variety of mechanisms during GC development. Therefore, we hypothesized that elevated levels of activated telomerase might enhance GC risk due to increased propagation of cells with DNA damage, such as induced by gamma-radiation.

METHODS

To explore this hypothesis, 246 GC cases and 246 matched controls were recruited in our case-control study. TRAP-ELISA was used to assess the levels of telomerase activity at baseline and after gamma-radiation and the gamma-radiation-induced telomerase activity (defined as after gamma-irradiation/baseline) in cultured peripheral blood lymphocytes (PBLs).

RESULTS

Our data showed that there was no significant difference for the baseline telomerase activity between GC cases and controls (10.17 +/- 7.21 vs. 11.02 +/- 8.03, p = 0.168). However, after gamma-radiation treatment, gamma-radiation-induced telomerase activity was significantly higher in the cases than in the controls (1.51 +/- 0.93 vs. 1.22 +/- 0.66, p < 0.001). Using the median value of gamma-radiation-induced telomerase activity in the controls as a cutoff point, we observed that high gamma-radiation-induced telomerase activity was associated with a significantly increased GC risk (adjusted odds ratio, 2.45; 95% confidence interval, 1.83-3.18). Moreover, a dose response association was noted between gamma-radiation-induced telomerase activity and GC risk. Age, but not sex, smoking and drinking status seem to have a modulating effect on the gamma-radiation-induced telomerase activities in both cases and controls.

CONCLUSION

Overall, our findings for the first time suggest that the increased gamma-radiation-induced telomerase activity in PBLs might be associated with elevated GC risk. Further confirmation of this association using a prospective study design is warranted.