Telomeres In Cells Research Articles

Dietary exposure to di (2-ethylhexyl) phthalate (DEHP) for 6months alters markers of female reproductive aging in mice.

The female reproductive system ages before any other physiological system, making it a sensitive indicator of aging. Early reproductive aging is associated with the early onset of infertility and an increased risk of several diseases. During aging, systemic and reproductive oxidative stress and inflammation levels increase through inflammasome activation, leading to ovarian follicle loss. Other markers of reproductive aging include increased fibrosis and shortening of telomeres in ovarian cells. The factors that accelerate reproductive aging are unclear, but likely involve exposure to endocrine-disrupting chemicals such as phthalates. Di(2-ethylhexyl) phthalate (DEHP) is a widely used phthalate and humans are exposed to it daily. Several studies show that DEHP induces reproductive toxicity by affecting estrous cyclicity, follicle numbers, and hormone levels. However, little is known about the mechanisms underlying DEHP-induced early onset of reproductive aging. Thus, this study tested the hypothesis that dietary exposure to DEHP induces early reproductive aging by affecting inflammation, fibrosis, and the expression of telomere regulators and antioxidant enzymes. Adult CD-1 female mice were exposed to vehicle (corn oil) or DEHP (0.5, 1.5, or 1500ppm) via the chow for six months. Exposure to DEHP increased the expression of antioxidant enzymes and Casp3, increased expression of telomere-associated genes, and increased fibrosis levels in the ovary. In addition, DEHP exposure for 6months altered ovarian and systemic inflammatory status. Collectively, our novel data suggest that 6-month dietary exposure to DEHP may accelerate reproductive aging by affecting several reproductive aging markers in female mice.

Low-power red laser and blue LED modulate telomere maintenance and length in human breast cancer cells.

Cancer cells have the ability to undergo an unlimited number of cell divisions, which gives them immortality. Thus, the cancer cell can extend the length of its telomeres, allowing these cells to divide unlimitedly and avoid entering the state of senescence or cellular apoptosis. One of the main effects of photobiomodulation (PBM) is the increase in the production of adenosine triphosphate (ATP) and free radicals, mainly reactive oxygen species (ROS). Existent data indicates that high levels of ROS can cause shortening and dysfunctional telomeres. Therefore, a better understanding of the effects induced by PBM on cancer cell telomere maintenance is needed. This work aimed to evaluate the effects of low-power red laser (658nm) and blue LED (470nm) on the TRF1 and TRF2 mRNA levels and telomere length in human breast cancer cells. MCF-7 and MDA-MB-231 cells were irradiated with a low-power red laser (69J cm-2, 0.77W/cm-2) and blue LED (482J cm-2, 5.35W/cm-2), alone or in combination, and the relative mRNA levels of the genes and telomere length were assessed by quantitative reverse transcription polymerase chain reaction. The results suggested that exposure to certain red laser and blue LED fluences decreased the TRF1 and TRF2 mRNA levels in both human breast cancer cells. Telomere length was increased in MCF-7 cells after exposure to red laser and blue LED. However, telomere length in MDA-MB-231 was shortened after exposure to red laser and blue LED at fluences evaluated. Our research suggests that photobiomodulation induced by red laser and low-power blue LED could alter telomere maintenance and length.

Effect of an 18-Month Meditation Training on Telomeres in Older Adults: A Secondary Analysis of the Age-Well Randomized Controlled Trial

BackgroundShorter telomeres are associated with increased risk of cognitive decline and age-related diseases. Developing interventions to promote healthy aging by preserving telomere integrity is of paramount importance. Here, we investigated the effect of an 18-month meditation intervention on telomere length (TL) measures in older people without cognitive impairment. MethodsA total of 137 adults age ≥65 years were randomized to one of the 3 groups (meditation training, non-native language training, or passive control). We evaluated the 50th and 20th percentile TL and the percentage of critically short telomeres (<3 kbp) in peripheral blood mononuclear cells. ResultsMixed model analysis showed a time effect indicating a general decrease on the 50th percentile TL (F = 80.72, padjusted < .001), without a significant group effect or time × group interaction. No significant effect was detected in the 20th percentile TL or the percentage of critically short telomeres. Secondary analysis showed that only in the meditation training group 1) the 50th percentile TL positively correlated with class attendance time (r = 0.45, padjusted < .011), 2) the 50th and 20th percentile TL positively correlated with responsiveness to the intervention, evaluated through a composite score (r = 0.46, padjusted < .010 and r = 0.41, padjusted = .029, respectively), and 3) lower scores on a measure of the personality trait “openness to experience” correlated with a lower percentage of critically short telomeres after the intervention (r = 0.44, padjusted = .015). ConclusionsIn older adults, we found no evidence for a main effect of an 18-month meditation training program on TL compared with the control groups. Our findings highlight the importance of considering the impact of moderating factors when measuring the effectiveness of meditation-based trainings.

Haplotype-resolved de novo assembly revealed unique characteristics of alternative lengthening of telomeres in mouse embryonic stem cells.

Telomeres protect chromosome ends from DNA damage responses, and their dysfunction triggers genomic alterations like chromosome fusion and rearrangement, which can lead to cellular death. Certain cells, including specific cancer cells, adopt alternative lengthening of telomere (ALT) to counteract dysfunctional telomeres and proliferate indefinitely. While telomere instability and ALT activity are likely major sources of genomic alteration, the patterns and consequences of such changes at the nucleotide level in ALT cells remainunexplored. Here we generated haplotype-resolved genome assemblies for type I ALT mouse embryonic stem cells, facilitated by highly accurateor ultra-long reads and Hi-C reads. High-quality genome revealed ALT-specific complex chromosome end structures and various genomic alterations including over 1000 structural variants (SVs). The unique sequence (mTALT) used as a template for type I ALT telomeres showed traces of being recruited into the genome, with mTALT being replicated with remarkably high accuracy. Subtelomeric regions exhibited distinct characteristics: resistance to the accumulation of SVs and small variants. We genotyped SVs at allele resolution, identifying genes (Rgs6, Dpf3and Tacc2) crucial for maintaining ALT telomere stability. Our genome assembly-based approach elucidated the unique characteristics of ALT genome, offering insights into the genome evolution of cells surviving telomere-derived crisis.

Telomere Length Measurement in Human Tissue Sections by Quantitative Fluorescence In Situ Hybridization (Q-FISH).

Telomeres in most somatic cells shorten with each cell division, and critically short telomeres lead to cellular dysfunction, cell cycle arrest, and senescence. Thus, telomere shortening is an important hallmark of human cellular senescence. Quantitative fluorescence in situ hybridization (Q-FISH) using formalin-fixed paraffin-embedded (FFPE) tissue sections allows the estimation of telomere lengths in individual cells in histological sections. In our Q-FISH method, fluorescently labelled peptide nucleic acid (PNA) probes are hybridized to telomeric and centromeric sequences in FFPE human tissue sections, and relative telomere lengths (telomere signal intensities relative to centromere signal intensities) are measured. This chapter describes our Q-FISH protocols for assessing relative telomere lengths in FFPE human tissue sections.

Genetic analysis from multiple cohorts implies causality between 2200 druggable genes, telomere length, and leukemia

BackgroundClinical therapeutic targets for leukemia remain to be identified and the causality between leukemia and telomere length is unclear. MethodsThis work employed cis expression quantitative trait locus (eQTL) for 2,200 druggable genes from the eQTLGen Consortium and genome-wide association studies (GWAS) summary data for telomere length in seven blood cell types from the UK Biobank, Netherlands Cohort as exposures. GWAS data for lymphoid leukemia (LL) and myeloid leukemia (ML) from FinnGen and Lee Lab were used as outcomes for discovery and replication cohorts, respectively. Robust Mendelian randomization (MR) findings were generated from seven MR models and a series of sensitivity analyses. Summary-data-based MR (SMR) analysis and transcriptome-wide association studies (TWAS) were further implemented to verify the association between identified druggable genes and leukemia. Single-cell type expression analysis was employed to identify the specific expression of leukemia casual genes on human bone marrow and peripheral blood immune cells. Multivariable MR analysis, linkage disequilibrium score regression (LDSC), and Bayesian colocalization analysis were performed to further validate the relationship between telomere length and leukemia. Mediation analysis was used to assess the effects of identified druggable genes affecting leukemia via telomere length. Phenome-wide MR (Phe-MR) analysis for assessing the effect of leukemia causal genes and telomere length on 1,403 disease phenotypes. ResultsCombining the results of the meta-analysis for MR estimates from two cohorts, SMR and TWAS analysis, we identified five LL causal genes (TYMP, DSTYK, PPIF, GDF15, FAM20A) and three ML causal genes (LY75, ADA, ABCA2) as promising drug targets for leukemia. Univariable MR analysis showed genetically predicted higher leukocyte telomere length increased the risk of LL (odds ratio [OR] = 2.33, 95 % confidence interval [95 % CI] 1.70–3.18; P = 1.33E-07), and there was no heterogeneity and horizontal pleiotropy. Evidence from the meta-analysis of two cohorts strengthened this finding (OR = 1.88, 95 % CI 1.06–3.05; P = 0.01). Multivariable MR analysis showed the causality between leukocyte telomere length and LL without interference from the other six blood cell telomere length (OR = 2.72, 95 % CI 1.88–3.93; P = 1.23E-07). Evidence from LDSC supported the positive genetic correlation between leukocyte telomere length and LL (rg = 0.309, P = 0.0001). Colocalization analysis revealed that the causality from leukocyte telomere length on LL was driven by the genetic variant rs770526 in the TERT region. The mediation analysis via two-step MR showed that the causal effect from TYMP on LL was partly mediated by leukocyte telomere length, with a mediated proportion of 12 %. ConclusionOur study identified several druggable genes associated with leukemia risk and provided new insights into the etiology and drug development of leukemia. We also found that genetically predicted higher leukocyte telomere length increased LL risk and its potential mechanism of action.

RIOK2 transcriptionally regulates TRiC and dyskerin complexes to prevent telomere shortening

Telomere shortening is a prominent hallmark of aging and is emerging as a characteristic feature of Myelodysplastic Syndromes (MDS) and Idiopathic Pulmonary Fibrosis (IPF). Optimal telomerase activity prevents progressive shortening of telomeres that triggers DNA damage responses. However, the upstream regulation of telomerase holoenzyme components remains poorly defined. Here, we identify RIOK2, a master regulator of human blood cell development, as a critical transcription factor for telomere maintenance. Mechanistically, loss of RIOK2 or its DNA-binding/transactivation properties downregulates mRNA expression of both TRiC and dyskerin complex subunits that impairs telomerase activity, thereby causing telomere shortening. We further show that RIOK2 expression is diminished in aged individuals and IPF patients, and it strongly correlates with shortened telomeres in MDS patient-derived bone marrow cells. Importantly, ectopic expression of RIOK2 alleviates telomere shortening in IPF patient-derived primary lung fibroblasts. Hence, increasing RIOK2 levels prevents telomere shortening, thus offering therapeutic strategies for telomere biology disorders.

Obesity-Associated Colorectal Cancer.

Colorectal cancer (CRC) affects approximately 2 million people worldwide. Obesity is the major risk factor for CRC. In addition, obesity contributes to a chronic inflammatory stage that enhances tumor progression through the secretion of proinflammatory cytokines. In addition to an increased inflammatory response, obesity-associated cancer presents accrued molecular factors related to cancer characteristics, such as genome instability, sustained cell proliferation, telomere dysfunctions, angiogenesis, and microbial alteration, among others. Despite the evidence accumulated over the last few years, the treatments for obesity-associated CRC do not differ from the CRC treatments in normal-weight individuals. In this review, we summarize the current knowledge on obesity-associated cancer, including its epidemiology, risk factors, molecular factors, and current treatments. Finally, we enumerate possible new therapeutic targets that may improve the conditions of obese CRC patients. Obesity is key for the development of CRC, and treatments resulting in the reversal of obesity should be considered as a strategy for improving antineoplastic CRC therapies.

Macrophage-derived exosomes promote telomere fragility and senescence in tubular epithelial cells by delivering miR-155

BackgroundChronic kidney disease (CKD) is highly prevalent worldwide, and its global burden is substantial and growing. CKD displays a number of features of accelerated senescence. Tubular cell senescence is a common biological process that contributes to CKD progression. Tubulointerstitial inflammation is a driver of tubular cell senescence and a common characteristic of CKD. However, the mechanism by which the interstitial inflammation drives tubular cell senescence remains unclear. This paper aims to explore the role of exosomal miRNAs derived from macrophages in the development of tubular cell senescence.MethodsAmong the identified inflammation-related miRNAs, miR-155 is considered to be one of the most important miRNAs involved in the inflammatory response. Macrophages, the primary immune cells that mediate inflammatory processes, contain a high abundance of miR-155 in their released exosomes. We assessed the potential role of miR-155 in tubular cell senescence and renal fibrosis. We subjected miR-155−/− mice and wild-type controls, as well as tubular epithelial cells (TECs), to angiotensin II (AngII)-induced kidney injury. We assessed kidney function and injury using standard techniques. TECs were evaluated for cell senescence and telomere dysfunction in vivo and in vitro. Telomeres were measured by the fluorescence in situ hybridization.ResultsCompared with normal controls, miR-155 was up-regulated in proximal renal tubule cells in CKD patients and mouse models of CKD. Moreover, the expression of miR-155 was positively correlated with the extent of renal fibrosis, eGFR decline and p16INK4A expression. The overexpression of miR-155 exacerbated tubular senescence, evidenced by increased detection of p16INK4A/p21expression and senescence-associated β-galactosidase activity. Notably, miR-155 knockout attenuates renal fibrosis and tubule cell senescence in vivo. Interestingly, once released, macrophages-derived exosomal miR-155 was internalized by TECs, leading to telomere shortening and dysfunction through targeting TRF1. A dual-luciferase reporter assay confirmed that TRF1 was the direct target of miR-155. Thus, our study clearly demonstrates that exosomal miR-155 may mediate communication between macrophages and TECs, subsequently inducing telomere dysfunction and senescence in TECs.ConclusionsOur work suggests a new mechanism by which macrophage exosomes are involved in the development of tubule senescence and renal fibrosis, in part by delivering miR-155 to target TRF1 to promote telomere dysfunction. Our study may provide novel strategies for the treatment of AngII-induced kidney injury.

P-705 Telomere length of white blood cells is a non-invasive marker of reproductive aging in women

Abstract Study question Can leukocyte telomere length be a marker of ovarian decline? Summary answer The significant correlation found between leukocyte and cumulus cell telomere lengths supports the use of leukocyte telomere length (TL) as a marker of ovarian aging. What is known already The telomere-based theory of reproductive aging proposes that age-related ovarian dysfunction is a consequence of progressive telomere shortening from fetal oogenesis to the adult ovary, compromising genome stability and proper chromosome segregation. Telomere length in cumulus cells (CCTL) is known to be a biomarker of oocyte and embryo quality, but its assessment is not practical. Hence, we previously proposed leukocyte telomere length (LTL) as an alternative to directly measuring telomere length in follicular cells, but so far it has only been assessed in samples of moderate size and homogeneous populations without consistent results. Study design, size, duration This prospective, non-interventional cohort study involved 300 women aged 18 to 46 years undergoing controlled ovarian stimulation over a 24-month period. The cohort included 169 egg donors and 131 IVF patients. Oocyte retrieval was performed 36 hours after maturation induction, with cumulus cells collected during oocyte stripping and blood samples taken via peripheral venous access. Participants/materials, setting, methods Genomic DNA was isolated from leukocytes and cumulus cells of all subjects for TL measurements. Relative TL was determined using a SYBR-Green quantitative real-time PCR protocol. A Taqman assay for the multicopy gene Alu was used to normalize the measurements. A Pearson’s correlation test was used to analyze the correlation between CCTL and LTL, as well as between TL and age, antral follicle count, Anti-Müllerian hormone, and number of mature oocytes retrieved. Main results and the role of chance Mean age of the subjects was 30.70±7.61 years. Anti-Müllerian hormone (AMH) mean level was 2.60±1.87 ng/ml, antral follicle count (AFC) was 17.8±7.4 and the number of mature oocytes was 14.3±9.3. A significant correlation was observed between CCTL and LTL (R = 0.6, p-value=2.2E-16). Notably, the relationship between leukocyte and cumulus cell telomere lengths was stronger in the 97 participants over 35 years (R = 0.67, p-value=1.55E-13), especially those between 39 to 46 years (R = 0.70, p-value=1.19E-12). Telomere length was inversely correlated with age in both leukocytes and cumulus cells (R=-0.23, p-value=6.98E-05; R=-0.4, p-value=2.38E-05), meaning the older the subject, the shorter the telomeres in both cells. Furthermore, longer telomeres in leukocytes and cumulus cells were significantly correlated with higher AFC (R = 0.20, p-value=0.0006; R = 0.25, p-value=1.83E-05), and more mature oocytes retrieved (R = 0.16, p-value=0.0043; R = 0.27, p-value=2.83E-06). However, we did not find any association between AMH levels and LTL or CCTL (R = 0.07, p-value=0.2666; R = 0.07, p-value=0.2747). Limitations, reasons for caution The method used to measure the average telomere length from pooled leukocyte samples may not reflect individual cell variability. Additionally, it allows for relative but not absolute telomere length comparisons. Wider implications of the findings This study is the first to demonstrate in a large and heterogeneous population that LTL could be a viable marker for ovarian aging by reflecting follicular cell telomere length. This finding may provide a valuable tool for assessing and monitoring the reproductive health of IVF patients. Trial registration number Not applicable

O-253 Altered telomerase activity in ovarian follicular cells in patients with polycystic ovary syndrome

Abstract Study question Is telomerase machinery altered in cumulus and granulosa cells of patients with Polycystic ovary syndrome (PCOS) undergoing assisted reproductive treatment (ART)? Summary answer Patients with PCOS presented an altered expression of telomerase inhibitor factors TRF1 and TRF2 and shorter telomeres in cumulus cells (CCs) and granulosa cells (GCs) What is known already PCOS affects 6%-20% of fertile women; one of the most common features is represented by abnormal folliculogenesis, showing a higher number of follicles at all developmental stages. In PCOS, increased levels of reactive oxygen species (ROS) have been related to abnormal follicular development due to oxidative stress-induced DNA damage. Telomeres, present at the ends of the chromosomes, are essential for maintaining their stability during somatic cell proliferation. When guanine-rich telomeric repeats are exposed to oxidative stress including ROS, they undergo oxidative DNA damage that shortens telomeres in non-dividing cells like follicular cells, thereby potentially altering folliculogenesis. Study design, size, duration A prospective experimental study was conducted at IVIRMA Rome and University Unicamillus from September 2022 to January 2024. CCs and GCs were collected from the follicular fluid of patients undergoing in vitro fertilization (IVF). Twenty-eight patients with PCOS and. Thirty-one normal responders were included in the pilot study. Participants/materials, setting, methods Women with PCOS (n = 28), diagnosed according to the Rotterdam criteria, were included in the study. The healthy control group (CONT) included normal responders (n = 31) undergoing IVF. CCs and GCs were collected on the day of oocyte retrieval and subsequently used for immunofluorescence spot counting of TRF1 and TRF2. In addition, telomere length was measured using a specific kit. qRT-PCRs for TRF1, TRF2 and apoptotic marker BAX genes were performed and expressed as 2^-ΔCT values. Main results and the role of chance Immunofluorescence for TRF1 in the PCOS group presented a higher spot number in CCs compared to the CONT (9.90±0.23 vs 7.96±0.33, p = 0.0009) while TRF2 spots significantly decreased (8.85 ±0.24 vs 11.23±0.28; p = 0.0007). An increase of TRF2 gene expression was observed in CCs of the PCOS group when compared to CONT (0.0052±0.0006 vs 0.0030±0.0003; p = 0.062) no differences were found in the expression of TRF1 (0.0343±0.006 vs 0.026±0.047p=0.68; Bax was significantly increased (0.0139±0.001 vs 0.0102±0,0007 p = 0.007) and telomeres have a shortening trend (0.36±0.36 vs 1±0 p = 0.74). In GC a lower number of TRF1 spots in PCOS vs CONT was observed while TRF2 had just an increasing trend (11.16± 0.586 vs 11.70 ± 1.99, p = 0.61; 16.79 ± 3,85 vs 11.34 ± 0.588; p = 0.68). In GCs of PCOS group vs CONT there was an increase in TRF2 gene expression (0,007 ± 0,001 vs 0.003 ± 0.0004; p = 0.03) and no differences were found in TRF1 (0.032± 0.003 vs 0.003± 0.012 p = 0.25). Ultimately Bax was increased in GCs of PCOS samples vs CONT (0.018 ±0.002 vs 0.011 ±0.0005 p = 0.0006) and the telomeres were significantly shorter (0.0246± 0.0349 vs 1± 0 p &amp;lt; 0.0001). Limitations, reasons for caution A limited number of samples were analyzed in the study and different PCOS sub-phenotypes were not considered. The analysis of CCs could be uninformative due to inter-individual variability in the PCOS sub-phenotypes within the same study group. Wider implications of the findings These findings demonstrate that PCOS patients present a higher expression of telomerase-inhibiting factors TRF1 and TRF2, undergo apoptosis and have significantly shorter telomeres supporting the theory that abnormal folliculogenesis in PCOS affects telomere length, therefore shedding new light on this medical condition and possibly explaining its clinical and biochemical features. Trial registration number not applicable

DNA-PKcs Inhibition Sensitizes Human Chondrosarcoma Cells to Carbon Ion Irradiation via Cell Cycle Arrest and Telomere Capping Disruption.

In order to overcome the resistance to radiotherapy in human chondrosarcoma cells, the prevention from efficient DNA repair with a combined treatment with the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) inhibitor AZD7648 was explored for carbon ion (C-ion) as well as reference photon (X-ray) irradiation (IR) using gene expression analysis, flow cytometry, protein phosphorylation, and telomere length shortening. Proliferation markers and cell cycle distribution changed significantly after combined treatment, revealing a prominent G2/M arrest. The expression of the G2/M checkpoint genes cyclin B, CDK1, and WEE1 was significantly reduced by IR alone and the combined treatment. While IR alone showed no effects, additional AZD7648 treatment resulted in a dose-dependent reduction in AKT phosphorylation and an increase in Chk2 phosphorylation. Twenty-four hours after IR, the key genes of DNA repair mechanisms were reduced by the combined treatment, which led to impaired DNA repair and increased radiosensitivity. A time-dependent shortening of telomere length was observed in both cell lines after combined treatment with AZD7648 and 8 Gy X-ray/C-ion IR. Our data suggest that the inhibition of DNA-PKcs may increase sensitivity to X-rays and C-ion IR by impairing its functional role in DNA repair mechanisms and telomere end protection.

The TERT Promoter is Polycomb-Repressed in Neuroblastoma Cells with Long Telomeres.

The epigenetic landscape of the TERT locus is unique in neuroblastoma. The DNA at the TERT locus, unlike other cancer cells and similar to normal cells, are hypomethylated in telomerase-positive neuroblastoma cells. The TERT locus is repressed by polycomb repressive complex-2 complex in neuroblastoma cells that have long telomeres and do not express TERT. Long telomeres in neuroblastoma cells are also associated with repressive chromatin states at the chromosomal termini, suggesting TPE.

Longer prostate stromal cell telomere length is associated with increased risk of death from other cancers.

Telomeres are located at chromosomal termini and function to maintain genomic integrity. Telomere dysfunction is a well-recognized contributor to aging and age-related diseases, such as prostate cancer. Since telomere length is highly heritable, we postulate that stromal cell telomere length in the tissue of a particular solid organ may generally reflect constitutive stromal cell telomere length in other solid organs throughout the body. Even with telomere loss occurring with each round of cell replication, in general, telomere length in prostate stromal cells in mid-life would still be correlated with the telomere length in stromal cells in other organs. Thus, we hypothesize that prostate stromal cell telomere length and/or telomere length variability is a potential indicator of the likelihood of developing future solid cancers, beyond prostate cancer, and especially lethal cancer. To explore this hypothesis, we conducted a cohort study analysis of 1,175 men who were surgically treated for prostate cancer and were followed for death, including from causes other than their prostate cancer. In this cohort study with a median follow-up of 19 years, we observed that longer prostate stromal cell telomere length measured in tissue microarray spots containing prostate cancer was associated with an increased risk of death from other solid cancers. Variability in telomere length among these prostate stromal cells was possibly positively associated with risk of death from other solid cancers. Studying the link between stromal cell telomere length and cancer mortality may be important for guiding the development of cancer interception and prevention strategies.

Abstract LB096: Telomere length as a predictor of therapy response and survival in patients diagnosed with ovarian carcinoma

Abstract Impaired telomere length (TL) maintenance in ovarian tissue may play a pivotal role in epithelial ovarian carcinoma (OvC) onset. TL in either target or surrogate tissue (blood) is currently being investigated as a predictor in anti-OvC therapy or as a biomarker of the disease progression, respectively. There is presently an urgent need for an appropriate approach to chemotherapy response prediction. We performed a monochrome multiplex qPCR measurement of TL in peripheral blood and tumor tissues of 209 OvC patients. Methylation status and gene expression of shelterin complex and telomerase catalytic subunit (hTERT) were determined within tumor tissues by High-Throughput DNA methylation profiling and RNA sequencing (RNA-Seq) analysis, respectively. The patients sensitive to cancer treatment (n=46) had shorter telomeres in peripheral blood cells compared to those treatment-resistant (n=93; P=0.037). Cancer tissue TL lower than the median predisposed to better overall survival (P=0.002). Gene expression of TPP1, which recruits telomerase to telomeres, was positively associated with TL in tumor tissue (P=0.026). TL measured in peripheral blood cells could serve as a marker of platinum therapy response in OvC patients. Additionally, TL determined in tumor tissue provides information on OvC patients' overall survival. The study was financed by the project NPO (LX22NPO05102), the Czech Health Research Council (NU21-03-00145), and the Czech Science Foundation (21-27902S). Citation Format: Kristyna Tomasova, Karolina Seborova, Michal Kroupa, Josef Horak, Ludmila Vodickova, Lukas Rob, Martin Hruda, Marcela Mrhalova, Alena Bartakova, Jiri Bouda, Thomas Fleischer, Vessela Kristensen, Pavel Vodicka, Radka Vaclavikova. Telomere length as a predictor of therapy response and survival in patients diagnosed with ovarian carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB096.

Abstract LB185: High resolution telomere measurements in human cancer and aging using long-read nanopore sequencing

Abstract Telomere length is an important biomarker of cellular replicative potential and aging, but existing measurement methods are limited in resolution and accuracy. During human carcinogenesis, telomeres shorten profoundly in the earliest stages that precede tumor invasion. Telomere shortening can either halt cancer progression by inducing senescence and cell death or can promote cancer development by destabilizing chromosomes and generating chromosomal rearrangements. Stabilization of telomeres, typically by the upregulation of telomerase, is required for progression of nearly all human cancers. Here, we deploy digital telomere measurement by nanopore sequencing to understand how distributions of human telomere length change during aging and following carcinogenesis. We measure telomere attrition and de novo elongation with unprecedented resolution in genetically defined populations of human stem cells, in cells from the peripheral blood of healthy individuals and patients with genetic defects in telomere maintenance, cancer patients, and cancer cell lines. We find that human aging is accompanied by a progressive loss of long telomeres and an accumulation of shorter telomeres in white blood cells. In patients with inherited defects in telomere maintenance, the accumulation of short telomeres is more pronounced and correlates with phenotypic severity. We apply machine learning to train a binary classification model that distinguishes healthy individuals from those with telomere biology disorders. Next, we investigated the telomere lengths of a cohort of twenty colorectal tumors with patient-matched healthy colonic epithelia and found that two-thirds of colorectal tumors have telomere length distributions significantly shorter than the surrounding normal tissue. Finally, we explore the utility of telomere length distributions in cancer cell lines as clinically actionable disease biomarkers. This sequencing and bioinformatic pipeline will advance our understanding of telomere maintenance mechanisms and the use of telomere length as a clinical biomarker of aging and disease. Citation Format: Santiago Sanchez, Jessica Gu, Anudeep Golla, William Shomali, Annika Martin, Dirk Hockemeyer, Sharon Savage, Steven Artandi. High resolution telomere measurements in human cancer and aging using long-read nanopore sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB185.

Ayurveda &amp; Bioactives as Adjuvant for Dna Modulation in Cancer Treatment &amp; Adverse Drug Reaction [ADR] – A Glimpse of Traditional Indian Nanotechnology

Bioactives such as Curcumin and Quercetin and herbs such as “Tulsi”/ Holy basil [_Occimum sanctum_ L.] can provide relief from Adverse drug reaction [ADR] caused by chemotherapy in cancer patients. About 50% patients face moderate ADR issues such as nausea, vomiting, headache, and fewer [20-30%] serious ones [hair loss, loss of fertility and immunity]. The growing recurrence or resistance of cancers to chemotherapy and antimicrobial resistance [AMR] are other emerging challenges in addressing the global cancer burden, among the top causes of death. Two targets of herbal/ bioactive actions include topoisomerase that affects cell replication and telomere length and it may reduce resistance/ recurrence also. Patients with special conditions the old, children and less developed countries with low health budgets can especially develop from it.

Abstract 1639: Telomere dynamics in aging and cancer by nanopore long-read sequencing

Abstract Telomeres are the protective, nucleoprotein structure at the ends of linear eukaryotic chromosomes. The accurate measurement of both telomeric length and composition of individual telomeres in mammalian cells has been challenged by the length and repetitive nature of telomeres. With the advent of third generation sequencing technologies, it is now technically possible to sequence entire telomeres and map them to individual chromosome arms. Here, we report a reliable method to enrich, sequence and analyze human telomeres using Oxford Nanopore Technologies long-read sequencing. To enrich for telomeric sequences we combine the ligation of adapters complementary to the telomeric G-overhang with restriction enzyme digest to sequence the telomeric C-strand and part of the adjacent subtelomere. The subtelomeric information is harvested to map individual telomeric reads to specific chromosome arms and even alleles. We have measured bulk, chromosome-arm-specific telomere length dynamics during cellular aging of cultured primary cells and in a patient-derived aging cohort. To address the impact of the telomere maintenance mechanism on telomere length and composition, we have sequenced matched pairs of fibroblasts and induced pluripotent stem cells, as well as five well-established telomerase- and ALT-positive cancer cell lines. Our results suggest that based on nanopore telomere long-read sequencing ALT-positive cells can be easily discriminated from normal and telomerase-positive cancer cells. Further, telomere sequencing allows to evaluate the methylation status of the subtelomeric CpG islands adjacent to telomeres. In summary, nanopore telomere long-read sequencing allows to measure the length and composition of individual telomeres and their mapping to specific chromosome arms. Telomere long read sequencing methods will be valuable tools to study telomere biology during aging and cancer. Citation Format: Tobias T. Schmidt, Carly Tyer, Preeyesh Rughani, Candy Haggblom, Jeff Jones, Xiaoguang Dai, Kelly A. Frazer, Fred H. Gage, Sissel Juul, Scott Hickey, Jan Karlseder. Telomere dynamics in aging and cancer by nanopore long-read sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1639.

Abstract 1645: Telomere-related genes associated with clinical-pathological in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) stands as one of the leading causes of cancer deaths worldwide. Studies have suggested that telomeres shortening is linked to genetic instability, higher risk of developing pancreatic cancer and pancreatic tumorigenesis. However, previous research has predominantly focused on either telomere length or specific telomere-related genes in pancreatic cancer. Therefore, it is essential to elucidate the association between telomere-related genes and pancreatic cancer to identify novel therapeutic strategies and establish prognostic biomarkers. Telomere-relevant genes were downloaded from the TelNet database. Expression data from primary tumour of The Cancer Genome Atlas-PAAD (TCGA-PAAD) cohort, the Genome Sequence Archive CRA001160 dataset and the GTEx database were obtained for screen for differentially expressed genes (DEGs). Gene set enrichment analisis was performed using the Enrichr software. The gene essentiality queried from the gene dependency database of the Achilles-DepMap project was also assessed. Finally, data of The Cancer Genome Atlas-PanCancer CaPa cohort and healthy pancreas from the GTEx database, obtained from the UCSC Xena project, were used to correlate gene expression with stemness signatures and clinical-pathological variables. We identified 300 telomere-associated DEGs, Of these, 73 genes were common to studies and they were to be enriched in biological processes related to the cell cycle and telomere homeostasis. The differentially expresed of ASS1, S100P, IGF2BP2, MET, ABCC3 and RAC1 genes were significantly associated with overall survival and recurrence-free survival, conferring them prognostic value. Furthermore, the expression profiles of these genes are significantly associated with the histological grade of the disease, as well as with tumour T-N classification, the presence of residual tumour, the degree of response to treatment and stemness signatures. Among these, three genes of particular interest (KLF3, RAC1 and ABI1) were identified and shown to be highly essential in pancreatic cancer cell lines. In summary, we have identified a telomere gene-related signature for pancreatic cancer, highlighting the prognostic value of KLF3, RAC1, and ABI1 genes. This signature is significantly associated with clinical-pathological variables of the disease, potentially offering new insights for individualized therapy. Citation Format: Erika Curiel Gómez, Vilma Maldonado Lagunas, Jorge Meléndez Zajgla. Telomere-related genes associated with clinical-pathological in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1645.

CST-polymerase α-primase solves a second telomere end-replication problem.

Telomerase adds G-rich telomeric repeats to the 3' ends of telomeres1, counteracting telomere shortening caused by loss of telomeric 3' overhangs during leading-strand DNA synthesis ('the end-replication problem'2). Here we report a second end-replication problem that originates from the incomplete duplication of the C-rich telomeric repeat strand (C-strand) by lagging-strand DNA synthesis. This problem is resolved by fill-in synthesis mediated by polymeraseα-primase bound to Ctc1-Stn1-Ten1 (CST-Polα-primase). In vitro, priming for lagging-strand DNA replication does not occur on the 3' overhang and lagging-strand synthesis stops in a zone of approximately 150 nucleotides (nt) more than 26 nt from the end of the template. Consistent with the in vitro data, lagging-end telomeres of cells lacking CST-Polα-primase lost 50-60 nt of telomeric CCCTAA repeats per population doubling. The C-strands of leading-end telomeres shortened by around 100 nt per population doubling, reflecting the generation of 3' overhangs through resection. The measured overall C-strand shortening in the absence of CST-Polα-primase fill-in is consistent with the combined effects of incomplete lagging-strand synthesis and 5' resection at the leading ends. We conclude that canonical DNA replication creates two telomere end-replication problems that require telomerase to maintain the G-rich strand and CST-Polα-primase to maintain the C-strand.