Exploring the effect of a lifestyle intervention on cancer risk: 43-year follow-up of the randomized Oslo diet and antismoking study.

BACKGROUND/OBJECTIVES: The Oslo diet and antismoking study showed that counselling for a healthy lifestyle reduced lifelong coronary mortality in high-risk men. We explored whether the same counselling reduced also cancer risk. METHODS: The study randomly allocated males at high coronary risk to either a 5-year intervention for lifestyle changes (cholesterol-lowering dietary changes, weight loss and stopping smoking) or a control group (1 : 1) in 1972/73. We explored the incidence and mortality of all cancers and cancer forms related to smoking, BMI or diet up to 43 years after randomization. RESULTS: A total of 595 men in the intervention and 621 in the control group were included. At inclusion median age was 45 years, 588 (48.4%) subjects were overweight (BMI > 25 kg m-2 ) and 925 (76.1%) current smokers. The intervention did not reduce the risk of cancer after 43 years (adjusted hazard ratio (HR) 0.96, 95% confidence interval (CI) 0.80-1.15). In the first 25 years of follow-up, among the 1088 (89.5%) men who were overweight/obese and/or smokers, the intervention reduced the incidence of those cancer forms related to smoking, BMI or diet (including carcinoma of the respiratory, digestive and urinary tracts; adjusted HR 0.69; 95% CI 0.49-0.99). The intervention had no significant effect on incidence beyond 25 years, or on mortality. CONCLUSIONS: The 5-year counselling for a healthy lifestyle did not reduce the overall cancer risk in the very long term. However, in the first 25 years, the counselling reduced the risk of relevant cancer types in overweight/obese subjects and smokers.

Increasing clinical relevance in oral radiology: Benefits and challenges when implementing digital assessment.

AIMS: The aims of the study were to investigate benefits and challenges in implementing a digital examination and study the clinical relevance of the digital examination in relation to clinical training and practice. MATERIAL AND METHOD: The study was based on semi-structured focus-group interviews from two distinct student populations (2016 and 2017) in a bachelor programme in dental hygiene. In addition, conversational data from a plenary discussion from the whole second student population (2017) were collected and analysed. The data were approached on basis of content analysis. RESULTS: A benefit experienced in the digital examination was the ease in typing and editing answers on the computer. This suggests an increased effectiveness in computer-based compared to analogue examinations. An additional advantage was the experienced relevance of the examination related to the clinic. This finding refers not only to the digital presentations of images, but also to the entire setting in the clinic and dental practice. The limitations reported by the students were non-optimal viewing conditions for presenting radiographic images and difficulties in obtaining an overview of the assignments compared to paper-based examinations due to the linear digital examination format. The last finding on lacking overview revealed an influence on student performances which should be taken seriously in designing digital examinations. CONCLUSION: In conclusion, the digital layout increases efficiency and clinical relevance of examinations to a certain extent. Obstacles were found in limitations related to image presentation and lack of overview of the examination. The latter challenge raises questions related to developing suitable assessment software.

Clinical characteristics of patients with suspected cardiac chest pain and angiographically normal coronary arteries in a secondary care hospital.

BACKGROUND: An important number of patients with suspected cardiac chest pain have non-obstructive coronary artery disease. Our purpose was to describe the clinical characteristics of patients with normal or near-normal coronary arteries in routine cardiological practice in a secondary care hospital. METHODS: In 2013, consecutive patients referred for invasive coronary angiography with suspected cardiac chest pain were analysed at a single-centre (Westfriesgasthuis, Hoorn, the Netherlands). Coronary arteries were defined as normal or near-normal if they showed no stenosis or only slight wall irregularities on visual assessment. Patients with a final non-cardiac diagnosis for the chest pain were excluded. RESULTS: A total of 558 patients were included. Of these, 151 (27%) showed normal or near-normal coronary arteries on visual assessment. This group of patients were significantly more often female (p < 0.001), younger (p < 0.001) and non-diabetic (p = 0.002). Forty percent of hospitalised patients who had normal or near-normal coronary arteries at coronary angiography showed an elevated troponin. CONCLUSION: In routine cardiological practice, around 1 out of 4 patients with suspected cardiac chest pain undergoing invasive angiography had normal or near-normal coronary arteries. We suggest that premenopausal women with suspected cardiac chest pain could be considered for non-invasive coronary imaging as a first step in clinical practice.

Human telomeres contain two distinct Myb-related proteins, TRF1 and TRF2.

Human telomeres are composed of long arrays of TTAGGG repeats that form a nucleoprotein complex required for the protection and replication of chromosome ends. One component of human telomeres is the TTAGGG repeat binding factor 1 (TRF1), a ubiquitously expressed protein, related to the protooncogene Myb, that is present at telomeres throughout the cell cycle. Recent evidence has implicated TRF1 in the control of telomere length. TRF1 is proposed to be an inhibitor of telomerase, acting in cis to limit the elongation of individual chromosome ends. Here we report the cloning of TRF2, a distant homologue of TRF1 that carries a very similar Myb-related DNA-binding motif. Like TRF1, TRF2 was ubiquitously expressed, bound specifically to duplex TTAGGG repeats in vitro and localized to all human telomeres in metaphase chromosomes. TRF2 was shown to have an architecture similar to that of TRF1 in that it carries a C-terminal Myb motif and a large TRF1-related dimerization domain near its N terminus. However, the dimerization domains of TRF1 and TRF2 did not interact, suggesting that these proteins exist predominantly as homodimers. While having similar telomere binding activity and domain organization, TRF2 differed from TRF1 in that its N terminus was basic rather than acidic, and TRF2 was much more conserved than TRF1. The results indicate that the TTAGGG repeat arrays at the ends of human and mouse chromosomes bind to two related proteins. Because TRF1 and TRF2 showed significant differences, we suggest that these factors have distinct functions at telomeres.

Cell-cycle-regulated association of RAD50/MRE11/NBS1 with TRF2 and human telomeres.

Telomeres allow cells to distinguish natural chromosome ends from damaged DNA and protect the ends from degradation and fusion. In human cells, telomere protection depends on the TTAGGG repeat binding factor, TRF2 (refs 1-4), which has been proposed to remodel telomeres into large duplex loops (t-loops). Here we show by nanoelectrospray tandem mass spectrometry that RAD50 protein is present in TRF2 immunocomplexes. Protein blotting showed that a small fraction of RAD50, MRE11 and the third component of the MRE11 double-strand break (DSB) repair complex, the Nijmegen breakage syndrome protein (NBS1), is associated with TRF2. Indirect immunofluorescence demonstrated the presence of RAD50 and MRE11 at interphase telomeres. NBS1 was associated with TRF2 and telomeres in S phase, but not in G1 or G2. Although the MRE11 complex accumulated in irradiation-induced foci (IRIFs) in response to gamma-irradiation, TRF2 did not relocate to IRIFs and irradiation did not affect the association of TRF2 with the MRE11 complex, arguing against a role for TRF2 in DSB repair. Instead, we propose that the MRE11 complex functions at telomeres, possibly by modulating t-loop formation.

Withdrawal time as a quality indicator for colonoscopy - a nationwide analysis.

BACKGROUND AND STUDY AIMS: A withdrawal time of at least 6 min has been recommended as a quality indicator for colonoscopy. One drawback of many of the studies that have investigated withdrawal time and produced conflicting results has been their single-center design involving few endoscopists. Therefore, the validity of withdrawal time as a quality measure remains unclear. This study explores the value of individual withdrawal time in a nationwide analysis. PATIENTS AND METHODS: This prospective cohort study comprised data from outpatient colonoscopies performed at 19 Norwegian centers from January to September 2009 and registered in the Norwegian Gastronet Quality Assurance (QA) program. The participating endoscopists were characterized by their median withdrawal time for visual colonoscopies (diagnostic colonoscopies without biopsy or therapy) and categorized into two visual withdrawal time (VWT) groups (< 6 min or ≥ 6 min) to analyze the predictive value of VWT for detection of one or more polyps ≥ 5 mm in diameter using multiple logistic regression models. RESULTS: The study included 4429 consecutive colonoscopies performed by 67 endoscopists. The adjusted odds ratio for the detection of polyps ≥ 5 mm was 1.21 (95 %CI 0.94 - 1.56, P = 0.14) for endoscopists with a median VWT ≥ 6 min compared with endoscopists with a median VWT < 6 min. CONCLUSION: Withdrawal time using 6 min as the threshold is not a strong predictor of the likelihood of finding a polyp during colonoscopy and should not be used as a quality indicator.

Incontinence after colonoscopy--an unrecognized and preventable problem. A cross-sectional study from the Gastronet quality assurance program.

BACKGROUND: Colonoscopy requires insufflation of gas for visualization of the bowel wall. Worldwide, this is usually done using air. The aim of the present study was to assess the risk of postcolonoscopy incontinence, and to investigate whether insufflation of CO2 instead of air may reduce this risk, since it is easily absorbed through the bowel mucosa. METHODS: This is a prospective multicenter study of colonoscopy patients undergoing bowel insufflation using air or CO2. A successive series of colonoscopies were reported to a national quality assurance program in Norway between January and December 2009 from 21 endoscopy centers with varying insufflation practices. The study comprised 7812 patients aged 18 years or older who were referred for outpatient colonoscopy. Of these, 5015 underwent colonoscopy performed using air and 2797 colonoscopy using CO2 insufflation. RESULTS: Patient-reported incontinence up to 24 h after colonoscopy was compared using binary logistic regression analysis for the type of gas used for insufflation. The air and CO2 patient groups were comparable with regard to age, sex, indication for colonoscopy, and sedation practice. Incontinence was reported by 336 out of 7812 patients (4.3%). Incontinence was significantly less frequent in the CO2 group than in the air group [2.1% versus 5.5%; adjusted odds ratio (OR) 0.38; 95%CI 0.28-0.50; P < 0.001]. Female patients had a higher risk of incontinence than men (adjusted OR 1.77; 95% CI 1.39-2.24; P < 0.001). CONCLUSION: About every 20th patient undergoing colonoscopy using standard air insufflation experiences postexamination incontinence. This proportion can be reduced by 60% by converting from air insufflation to insufflation with the absorbable CO2.

Structure, subnuclear distribution, and nuclear matrix association of the mammalian telomeric complex.

Mammalian telomeres are composed of long arrays of TTAGGG repeats complexed with the TTAGGG repeat binding factor, TRF. Biochemical and ultrastructural data presented here show that the telomeric DNA and TRF colocalize in individual, condensed structures in the nuclear matrix. Telomeric TTAGGG repeats were found to carry an array of nuclear matrix attachment sites occurring at a frequency of at least one per kb. The nuclear matrix association of the telomeric arrays extended over large domains of up to 20-30 kb, encompassing the entire length of most mammalian telomeres. TRF protein and telomeric DNA cofractionated in nuclear matrix preparations and colocalized in discrete, condensed sites throughout the nuclear volume. FISH analysis indicated that TRF is an integral component of the telomeric complex and that the presence of TRF on telomeric DNA correlates with the compact configuration of telomeres and their association with the nuclear matrix. Biochemical fractionation of TRF and telomeric DNA did not reveal an interaction with the nuclear lamina. Furthermore, ultrastructural analysis indicated that the mammalian telomeric complex occupied sites throughout the nuclear volume, arguing against a role for the nuclear envelope in telomere function during interphase. These results are consistent with the view that mammalian telomeres form nuclear matrix-associated, TRF-containing higher order complexes at dispersed sites throughout the nuclear volume.

Tankyrase, a poly(ADP-ribose) polymerase at human telomeres.

Tankyrase, a protein with homology to ankyrins and to the catalytic domain of poly(adenosine diphosphate-ribose) polymerase (PARP), was identified and localized to human telomeres. Tankyrase binds to the telomeric protein TRF1 (telomeric repeat binding factor-1), a negative regulator of telomere length maintenance. Like ankyrins, tankyrase contains 24 ankyrin repeats in a domain responsible for its interaction with TRF1. Recombinant tankyrase was found to have PARP activity in vitro, with both TRF1 and tankyrase functioning as acceptors for adenosine diphosphate (ADP)-ribosylation. ADP-ribosylation of TRF1 diminished its ability to bind to telomeric DNA in vitro, suggesting that telomere function in human cells is regulated by poly(ADP-ribosyl)ation.

p53- and ATM-dependent apoptosis induced by telomeres lacking TRF2.

Although broken chromosomes can induce apoptosis, natural chromosome ends (telomeres) do not trigger this response. It is shown that this suppression of apoptosis involves the telomeric-repeat binding factor 2 (TRF2). Inhibition of TRF2 resulted in apoptosis in a subset of mammalian cell types. The response was mediated by p53 and the ATM (ataxia telangiectasia mutated) kinase, consistent with activation of a DNA damage checkpoint. Apoptosis was not due to rupture of dicentric chromosomes formed by end-to-end fusion, indicating that telomeres lacking TRF2 directly signal apoptosis, possibly because they resemble damaged DNA. Thus, in some cells, telomere shortening may signal cell death rather than senescence.

A human telomeric protein.

Telomeres are multifunctional elements that shield chromosome ends from degradation and end-to-end fusions, prevent activation of DNA damage checkpoints, and modulate the maintenance of telomeric DNA by telomerase. A major protein component of human telomeres has been identified and cloned. This factor, TRF, contains one Myb-type DNA-binding repeat and an amino-terminal acidic domain. Immunofluorescent labeling shows that TRF specifically colocalizes with telomeric DNA in human interphase cells and is located at chromosome ends during metaphase. The presence of TRF along the telomeric TTAGGG repeat array demonstrates that human telomeres form a specialized nucleoprotein complex.

Tankyrase promotes telomere elongation in human cells.

Human telomeres are maintained by telomerase, a reverse transcriptase that adds telomeric repeats to chromosome ends [1,2]. In human tumors and immortalized cells, telomeres are often maintained at a constant length setting [3,4], indicating that telomerase-mediated telomere elongation is tightly regulated. Tankyrase, a telomeric poly(ADP-ribose) polymerase (PARP) [5], was identified through its interaction with TRF1 [6], a negative regulator of telomere extension by telomerase [7]. Tankyrase-mediated ADP-ribosylation inhibits binding of TRF1 to telomeric repeats in vitro [5], suggesting that tankyrase might regulate TRF1 and therefore control telomere dynamics in vivo. Here, we present evidence that tankyrase acts as a positive regulator of telomere elongation in vivo, apparently by inhibiting TRF1. Overexpression of tankyrase in the nucleus diminished the level of unmodified TRF1 in immunoblots and led to reduced immunofluorescence of TRF1 at interphase telomeres. Long-term overexpression of tankyrase in telomerase-positive human cells resulted in a gradual and progressive elongation of telomeres. A PARP-deficient form of tankyrase failed to affect TRF1 and did not alter telomere length dynamics, consistent with ADP-ribosylation of TRF1 as the main cause of altered telomere homeostasis. Our results indicate that tankyrase can induce telomere elongation in human cells. We propose that tankyrase-mediated ADP-ribosylation of TRF1 opens the telomeric complex, allowing access to telomerase.

TRF1, a mammalian telomeric protein.

Telomerase adds TTAGGG repeats onto mammalian chromosome ends, replenishing the terminal sequence loss incurred during DNA replication. This maintenance of telomeric DNA preserves binding sites for telomeric proteins, which form a protective nucleoprotein complex at chromosome ends. The recent isolation of TRF1, the mammalian telomeric-repeat binding factor, should now allow the structure and function of the telomeric complex to be examined in detail.

Unusual chromatin in human telomeres.

We report that human telomeres have an unusual chromatin structure characterized by diffuse micrococcal nuclease patterns. The altered chromatin manifested itself only in human telomeres that are relatively short (2 to 7 kb). In contrast, human and mouse telomeres with telomeric repeat arrays of 14 to 150 kb displayed a more canonical chromatin structure with extensive arrays of tightly packed nucleosomes. All telomeric nucleosomes showed a shorter repeat size than bulk nucleosomes, and telomeric mononucleosomal particles were found to be hypersensitive to micrococcal nuclease. However, telomeric nucleosomes were similar to bulk nucleosomes in the rate at which they sedimented through sucrose gradients. We speculate that mammalian telomeres have a bipartite structure with unusual chromatin near the telomere terminus and a more canonical nucleosomal organization in the proximal part of the telomere.

A mammalian factor that binds telomeric TTAGGG repeats in vitro.

We have identified a DNA-binding activity with specificity for the TTAGGG repeat arrays found at mammalian telomeres. This factor, called TTAGGG repeat factor (TRF), is present in nuclear extracts of human, mouse, and monkey cells. TRF from HeLa cells was characterized in detail by electrophoretic mobility shift assays. It binds double-stranded TTAGGG repeats in linear and circular DNAs. Single-stranded repeats are not recognized. The optimal site for TRF appears to contain more than six contiguous TTAGGG repeats. Tandem arrays of TAGGG, TTTAGGG, TTTTAGGG, TTGGGG, and TTAGGC repeats do not bind TRF well, indicating that TRF preferentially recognizes the telomeric repeat sequence present at mammalian chromosome ends. The apparent molecular mass of this factor, based on recovery of TRF from sodium dodecyl sulfate-polyacrylamide gels, is approximately 50 kDa. We suggest that TRF binds along the length of mammalian telomeres.

Control of human telomere length by TRF1 and TRF2.

Telomere length in human cells is controlled by a homeostasis mechanism that involves telomerase and the negative regulator of telomere length, TRF1 (TTAGGG repeat binding factor 1). Here we report that TRF2, a TRF1-related protein previously implicated in protection of chromosome ends, is a second negative regulator of telomere length. Overexpression of TRF2 results in the progressive shortening of telomere length, similar to the phenotype observed with TRF1. However, while induction of TRF1 could be maintained over more than 300 population doublings and resulted in stable, short telomeres, the expression of exogenous TRF2 was extinguished and the telomeres eventually regained their original length. Consistent with their role in measuring telomere length, indirect immunofluorescence indicated that both TRF1 and TRF2 bind to duplex telomeric DNA in vivo and are more abundant on telomeres with long TTAGGG repeat tracts. Neither TRF1 nor TRF2 affected the expression level of telomerase. Furthermore, the presence of TRF1 or TRF2 on a short linear telomerase substrate did not inhibit the enzymatic activity of telomerase in vitro. These findings are consistent with the recently proposed t loop model of telomere length homeostasis in which telomerase-dependent telomere elongation is blocked by sequestration of the 3' telomere terminus in TRF1- and TRF2-induced telomeric loops.

Definition of regions in human c-myc that are involved in transformation and nuclear localization.

To study the relationship between the primary structure of the c-myc protein and some of its functional properties, we made in-frame insertion and deletion mutants of the normal human c-myc coding domain that was expressed from a retroviral promoter-enhancer. We assessed the effects of these mutations on the ability of c-myc protein to cotransform normal rat embryo cells with a mutant ras gene, induce foci in a Rat-1-derived cell line (Rat-1a), and localize in nuclei. Using the cotransformation assay, we found two regions of the protein (amino acids 105 to 143 and 321 to 439) where integrity was critical: one region (amino acids 1 to 104) that tolerated insertion and small deletion mutations, but not large deletions, and another region (amino acids 144) to 320) that was largely dispensable. Comparison with regions that were important for transformation of Rat-1a cells revealed that some are essential for both activities, but others are important for only one or the other, suggesting that the two assays require different properties of the c-myc protein. Deletion of each of three regions of the c-myc protein (amino acids 106 to 143, 320 to 368, and 370 to 412) resulted in partial cytoplasmic localization, as determined by immunofluorescence or immunoprecipitation following subcellular fractionation. Some abnormally located proteins retained transforming activity; most proteins lacking transforming activity appeared to be normally located.

Telomerase activation in mouse mammary tumors: lack of detectable telomere shortening and evidence for regulation of telomerase RNA with cell proliferation.

Activation of telomerase in human cancers is thought to be necessary to overcome the progressive loss of telomeric DNA that accompanies proliferation of normal somatic cells. According to this model, telomerase provides a growth advantage to cells in which extensive terminal sequence loss threatens viability. To test these ideas, we have examined telomere dynamics and telomerase activation during mammary tumorigenesis in mice carrying a mouse mammary tumor virus long terminal repeat-driven Wnt-1 transgene. We also analyzed Wnt-1-induced mammary tumors in mice lacking p53 function. Normal mammary glands, hyperplastic mammary glands, and mammary carcinomas all had the long telomeres (20 to 50 kb) typical of Mus musculus and did not show telomere shortening during tumor development. Nevertheless, telomerase activity and the RNA component of the enzyme were consistently upregulated in Wnt-1-induced mammary tumors compared with normal and hyperplastic tissues. The upregulation of telomerase activity and RNA also occurred during tumorigenesis in p53-deficient mice. The expression of telomerase RNA correlated strongly with histone H4 mRNA in all normal tissues and tumors, indicating that the RNA component of telomerase is regulated with cell proliferation. Telomerase activity in the tumors was elevated to a greater extent than telomerase RNA, implying that the enzymatic activity of telomerase is regulated at additional levels. Our data suggest that the mechanism of telomerase activation in mouse mammary tumors is not linked to global loss of telomere function but involves multiple regulatory events including upregulation of telomerase RNA in proliferating cells.

Structure and variability of human chromosome ends.

Mammalian telomeres are thought to be composed of a tandem array of TTAGGG repeats. To further define the type and arrangement of sequences at the ends of human chromosomes, we developed a direct cloning strategy for telomere-associated DNA. The method involves a telomere enrichment procedure based on the relative lack of restriction endonuclease cutting sites near the ends of human chromosomes. Nineteen (TTAGGG)n-bearing plasmids were isolated, two of which contain additional human sequences proximal to the telomeric repeats. These telomere-flanking sequences detect BAL 31-sensitive loci and thus are located close to chromosome ends. One of the flanking regions is part of a subtelomeric repeat that is present at 10 to 25% of the chromosome ends in the human genome. This sequence is not conserved in rodent DNA and therefore should be a helpful tool for physical characterization of human chromosomes in human-rodent hybrid cell lines; some of the chromosomes that may be analyzed in this manner have been identified, i.e., 7, 16, 17, and 21. The minimal size of the subtelomeric repeat is 4 kilobases (kb); it shows a high frequency of restriction fragment length polymorphisms and undergoes extensive de novo methylation in somatic cells. Distal to the subtelomeric repeat, the chromosomes terminate in a long region (up to 14 kb) that may be entirely composed of TTAGGG repeats. This terminal segment is unusually variable. Although sperm telomeres are 10 to 14 kb long, telomeres in somatic cells are several kilobase pairs shorter and very heterogeneous in length. Additional telomere reduction occurs in primary tumors, indicating that somatic telomeres are unstable and may continuously lose sequences from their termini.

Mammalian meiotic telomeres: protein composition and redistribution in relation to nuclear pores.

Mammalian telomeres consist of TTAGGG repeats, telomeric repeat binding factor (TRF), and other proteins, resulting in a protective structure at chromosome ends. Although structure and function of the somatic telomeric complex has been elucidated in some detail, the protein composition of mammalian meiotic telomeres is undetermined. Here we show, by indirect immunofluorescence (IF), that the meiotic telomere complex is similar to its somatic counterpart and contains significant amounts of TRF1, TRF2, and hRap1, while tankyrase, a poly-(ADP-ribose)polymerase at somatic telomeres and nuclear pores, forms small signals at ends of human meiotic chromosome cores. Analysis of rodent spermatocytes reveals Trf1 at mouse, TRF2 at rat, and mammalian Rap1 at meiotic telomeres of both rodents. Moreover, we demonstrate that telomere repositioning during meiotic prophase occurs in sectors of the nuclear envelope that are distinct from nuclear pore-dense areas. The latter form during preleptotene/leptotene and are present during entire prophase I.