Ulrika Svenson

Shortened Telomere length is associated with increased risk of cancer: A meta-analysis

Background Telomeres play a key role in the maintenance of chromosome integrity and stability, and telomere shortening is involved in initiation and progression of malignancies. A series of epidemiological studies have examined the association between shortened telomeres and risk of cancers, but the findings remain conflicting. Methods A dataset composed of 11,255 cases and 13,101 controls from 21 publications was included in a meta-analysis to evaluate the association between overall cancer risk or cancer-specific risk and the relative telomere length. Heterogeneity among studies and their publication bias were further assessed by the χ2-based Q statistic test and Eggers test, respectively. Results The results showed that shorter telomeres were significantly associated with cancer risk (OR = 1.35, 95% CI = 1.14–1.60), compared with longer telomeres. In the stratified analysis by tumor type, the association remained significant in subgroups of bladder cancer (OR = 1.84, 95% CI = 1.38–2.44), lung cancer (OR = 2.39, 95% CI = 1.18–4.88), smoking-related cancers (OR = 2.25, 95% CI = 1.83–2.78), cancers in the digestive system (OR = 1.69, 95% CI = 1.53–1.87) and the urogenital system (OR = 1.73, 95% CI = 1.12–2.67). Furthermore, the results also indicated that the association between the relative telomere length and overall cancer risk was statistically significant in studies of Caucasian subjects, Asian subjects, retrospective designs, hospital-based controls and smaller sample sizes. Funnel plot and Eggers test suggested that there was no publication bias in the current meta-analysis (P = 0.532). Conclusions The results of this meta-analysis suggest that the presence of shortened telomeres may be a marker for susceptibility to human cancer, but single larger, well-design prospective studies are warranted to confirm these findings.

Breast Cancer Survival Is Associated with Telomere Length in Peripheral Blood Cells

Telomeres are essential for maintaining chromosomal stability. Previous studies have indicated that individuals with shorter blood telomeres may be at higher risk of developing various types of cancer, such as in lung, bladder, and kidney. We have analyzed relative telomere length (RTL) of peripheral blood cells in relation to breast cancer incidence and prognosis. The study included 265 newly diagnosed breast cancer patients and 446 female controls. RTL was measured by real-time PCR, and our results show that the patient group displayed significantly longer telomeres compared with controls (P < 0.001). Age-adjusted odds ratios (OR) for breast cancer risk increased with increasing telomere length, with a maximal OR of 5.17 [95% confidence interval (95% CI), 3.09-8.64] for the quartile with the longest telomeres. Furthermore, RTL carried prognostic information for patients with advanced disease. Node positive (N+) patients with short telomeres (</=median) showed an increased survival compared with N+ patients with long telomeres (P = 0.001). For patients with ages <50 years with tumors >16 mm (median tumor diameter), short telomeres were associated with a significantly better outcome than longer telomeres (P = 0.006). Cox regression analysis showed that long RTL was a significant independent negative prognostic factor (hazards ratio, 2.92; 95% CI, 1.33-6.39; P = 0.007). Our results indicate that blood RTL may serve as a prognostic indicator in breast cancer patients with advanced disease.

The individual blood cell telomere attrition rate is telomere length dependent.

Age-associated telomere shortening is a well documented feature of peripheral blood cells in human population studies, but it is not known to what extent these data can be transferred to the individual level. Telomere length (TL) in two blood samples taken at ∼10 years interval from 959 individuals was investigated using real-time PCR. TL was also measured in 13 families from a multigenerational cohort. As expected, we found an age-related decline in TL over time (r = –0.164, P<0.001, n = 959). However, approximately one-third of the individuals exhibited a stable or increased TL over a decade. The individual telomere attrition rate was inversely correlated with initial TL at a highly significant level (r = –0.752, P<0.001), indicating that the attrition rate was most pronounced in individuals with long telomeres at baseline. In accordance, the age-associated telomere attrition rate was more prominent in families with members displaying longer telomeres at a young age (r = –0.691, P<0.001). Abnormal blood TL has been reported at diagnosis of various malignancies, but in the present study there was no association between individual telomere attrition rate or prediagnostic TL and later tumor development. The collected data strongly suggest a TL maintenance mechanism acting in vivo, providing protection of short telomeres as previously demonstrated in vitro. Our findings might challenge the hypothesis that individual TL can predict possible life span or later tumor development.

Reproducibility of telomere length assessment: an international collaborative study.

Background: Telomere length is a putative biomarker of ageing, morbidity and mortality. Its application is hampered by lack of widely applicable reference ranges and uncertainty regarding the present limits of measurement reproducibility within and between laboratories. Methods: We instigated an international collaborative study of telomere length assessment: 10 different laboratories, employing 3 different techniques [Southern blotting, single telomere length analysis (STELA) and real-time quantitative PCR (qPCR)] performed two rounds of fully blinded measurements on 10 human DNA samples per round to enable unbiased assessment of intra- and inter-batch variation between laboratories and techniques. Results: Absolute results from different laboratories differed widely and could thus not be compared directly, but rankings of relative telomere lengths were highly correlated (correlation coefficients of 0.63–0.99). Intra-technique correlations were similar for Southern blotting and qPCR and were stronger than inter-technique ones. However, inter-laboratory coefficients of variation (CVs) averaged about 10% for Southern blotting and STELA and more than 20% for qPCR. This difference was compensated for by a higher dynamic range for the qPCR method as shown by equal variance after z-scoring. Technical variation per laboratory, measured as median of intra- and inter-batch CVs, ranged from 1.4% to 9.5%, with differences between laboratories only marginally significant (P = 0.06). Gel-based and PCR-based techniques were not different in accuracy. Conclusions: Intra- and inter-laboratory technical variation severely limits the usefulness of data pooling and excludes sharing of reference ranges between laboratories. We propose to establish a common set of physical telomere length standards to improve comparability of telomere length estimates between laboratories.

Telomere length as a biological marker in malignancy

Telomere maintenance is important for tumor cell growth and survival. Telomere length (TL) is determined by the balance between positive and negative factors impacting telomere homeostasis. In the last decade, TL has emerged as a promising clinical marker for risk and prognosis prediction in patients with malignant disorders. Tumor TL, as well as TL in healthy tissues such as peripheral blood, may carry valuable information for future treatment strategies. Here we discuss the present status of TL as a biological marker in cancer patients.

Blood cell telomere length is a dynamic feature

There is a considerable heterogeneity in blood cell telomere length (TL) for individuals of similar age and recent studies have revealed that TL changes by time are dependent on TL at baseline. TL is partly inherited, but results from several studies indicate that e.g. life style and/or environmental factors can affect TL during life. Collectively, these studies imply that blood cell TL might fluctuate during a life time and that the actual TL at a defined time point is the result of potential regulatory mechanism(s) and environmental factors. We analyzed relative TL (RTL) in subsequent blood samples taken six months apart from 50 individuals and found significant associations between RTL changes and RTL at baseline. Individual RTL changes per month were more pronounced than the changes recorded in a previously studied population analyzed after 10 years’ follow up. The data argues for an oscillating TL pattern which levels out at longer follow up times. In a separate group of five blood donors, a marked telomere loss was demonstrated within a six month period for one donor where after TL was stabilized. PCR determined RTL changes were verified by Southern blotting and STELA (single telomere elongation length analysis). The STELA demonstrated that for the donor with a marked telomere loss, the heterogeneity of the telomere distribution decreased considerably, with a noteworthy loss of the largest telomeres. In summary, the collected data support the concept that individual blood cell telomere length is a dynamic feature and this will be important to recognize in future studies of human telomere biology.

Large-scale parent–child comparison confirms a strong paternal influence on telomere length

Telomere length is documented to have a hereditary component, and both paternal and X-linked inheritance have been proposed. We investigated blood cell telomere length in 962 individuals with an age range between 0 and 102 years. Telomere length correlations were analyzed between parent–child pairs in different age groups and between grandparent–grandchild pairs. A highly significant correlation between the fathers and the childs telomere length was observed (r=0.454, P<0.001), independent of the sex of the offspring (father–son: r=0.465, P<0.001; father–daughter: r=0.484, P<0.001). For mothers, the correlations were weaker (mother–child: r=0.148, P=0.098; mother–son: r=0.080, P=0.561; mother–daughter: r=0.297, P=0.013). A positive telomere length correlation was also observed for grandparent–grandchild pairs (r=0.272, P=0.013). Our findings indicate that fathers contribute significantly stronger to the telomere length of the offspring compared with mothers (P=0.012), but we cannot exclude a maternal influence on the daughters telomeres. Interestingly, the father–child correlations diminished with increasing age (P=0.022), suggesting that nonheritable factors have an impact on telomere length dynamics during life.

Telomere Length in Peripheral Blood Predicts Survival in Clear Cell Renal Cell Carcinoma

Telomeres are repetitive structures located at chromosome ends. Previous studies have indicated that blood cell telomeres may serve as a biomarker for cancer risk. In addition, we recently reported that blood telomere length predicted survival in patients with breast cancer. In the present study, we examined whether blood telomere length may act as a predictor for survival in newly diagnosed patients with clear cell renal cell carcinoma. Furthermore, we analyzed telomere length in tumor samples and corresponding kidney cortex. Relative telomere length (RTL) was measured on extracted DNA using real-time PCR. Interestingly, and in line with our previous findings in breast cancer, patients with the longest blood telomeres (fourth quartile) had a significantly worse prognosis compared with patients with shorter blood RTL (P=0.005). A highly significant association was found between long blood telomeres and a poor outcome in patients with nonmetastatic disease (P<0.001), whereas patients with distant metastases had a poor survival regardless of blood RTL (P=0.432). No correlations were found between blood RTL and various clinical variables, such as erythrocyte sedimentation rate, hemoglobin, and thrombocyte count. Multivariate Cox regression analysis verified long blood RTL as an independent negative prognostic marker. In contrast, telomere length in kidney cortex and tumor tissue did not predict survival. In conclusion, our results indicate that blood RTL may predict kidney cancer survival, with implications for future treatment strategies.

Stand up for health—avoiding sedentary behaviour might lengthen your telomeres: secondary outcomes from a physical activity RCT in older people

Background Telomere length has been associated with a healthy lifestyle and longevity. However, the effect of increased physical activity on telomere length is still unknown. Therefore, the aim was to study the relationship between changes in physical activity level and sedentary behaviour and changes in telomere length. Methods Telomere length was measured in blood cells 6 months apart in 49, 68-year-old, sedentary, overweight individuals taking part in a randomised controlled physical activity intervention trial. The intervention group received individualised physical activity on prescription. Physical activity was measured with a 7-day diary, questionnaires and a pedometer. Sitting time was measured with the short version of The International Physical Activity Questionnaire. Results Time spent exercising as well as steps per day increased significantly in the intervention group. Reported sitting time decreased in both groups. No significant associations between changes in steps per day and changes in telomere length were noted. In the intervention group, there was a negative correlation between changes in time spent exercising and changes in telomere length (rho=−0.39, p=0.07). On the other hand, in the intervention group, telomere lengthening was significantly associated with reduced sitting time (rho=−0.68, p=0.02). Conclusions Reduced sitting time was associated with telomere lengthening in blood cells in sedentary, overweight 68-year-old individuals participating in a 6-month physical activity intervention trial.

Polymorphisms in telomere-associated genes, breast cancer susceptibility and prognosis

Telomeres are essential structures for maintaining chromosomal stability and their length has been reported to correlate with cancer risk and clinical outcome. Single nucleotide polymorphisms (SNPs) in genes encoding telomere-associated proteins could affect telomere length and chromosomal stability by influencing gene expression or protein configuration in the telomeres. Here, we report the results of the first association study on genetic variation in telomere-associated genes and their effect on telomere length, breast cancer (BC) susceptibility and prognosis. We genotyped 14 potentially functional and most informative SNPs in nine telomere-associated genes (TERT, TEP1, TERF1, TERF2, TERF2IP, ACD, POT1, TNKS and TNKS2) in 782 incident BC cases and 1559 matched controls. Relative telomere length (RTL) varied statistically significantly between the genotypes of the SNPs rs446977 (TEP1, p=0.04), rs938886 (TEP1, p=0.04) and rs6990097 (TNKS, p=0.04). However, none of them was associated with BC susceptibility and only rs6990097 correlated with regional lymph node metastasis (odds ratio (OR) 1.38, 95% confidence interval (CI) 1.08-1.77). The strongest association with BC susceptibility was observed for rs3785074 (TERF2, OR 0.51, 95% CI 0.31-0.83) and rs10509637 (TNKS2, OR 1.33, 95% CI 1.08-1.62). Haplotype and diplotype analysis confirmed the association of the TNKS2 gene with BC susceptibility. rs3785074 (TERF2) was additionally associated with histologic grade (OR 1.44, 95% CI 1.08-1.92) and negative oestrogen receptor status (OR 2.93, 95% CI 1.13-7.58). None of the SNPs showed a significant correlation with survival of the breast cancer patients. With these results, none of the SNPs represents any valuable prognostic marker for BC.