Telomere dysfunction and tumour suppression: the senescence connection

Inhibition of hTERT/telomerase/telomere mediates therapeutic efficacy of osimertinib in EGFR mutant lung cancer

The inevitable acquired resistance to osimertinib (AZD9291), an FDA-approved third-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) for the treatment of patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR activating or T790M resistant mutations, limits its long-term clinical benefit. Telomere maintenance via telomerase reactivation is linked to uncontrolled cell growth and is a cancer hallmark and an attractive cancer therapeutic target. Our effort toward understanding the action mechanisms, including resistance mechanisms, of osimertinib has led to the identification of a novel and critical role in maintaining c-Myc-dependent downregulation of hTERT, a catalytic subunit of telomerase, and subsequent inhibition of telomerase/telomere and induction of telomere dysfunction in mediating therapeutic efficacy of osimertinib. Consequently, osimertinib combined with the telomere inhibitor, 6-Thio-dG, which is currently tested in a phase II trial, effectively inhibited the growth of osimertinib-resistant tumors, regressed EGFRm NSCLC patient-derived xenografts, and delayed the emergence of acquired resistance to osimertinib, warranting clinical validation of this strategy to manage osimertinib acquired resistance.

Principles of Tumor Biology

Cancer is disease of the genome. The Hallmarks of cancer are a way of thinking of cancer to help rationalize what occurs in this disease process. A solid tumor is a complex of normal and neoplastic cells, arising through an evolutionary process to survive and grow. By understanding how normal cellular mechanisms are subverted to promote cancer we can refine our approach to improve outcomes. It gives us opportunities to prevent some cancers and allowing earlier diagnosis. We can refine conventional diagnostic tools and give more accurate prognoses. It offers novel targets to improve treatment of cancers, allowing personalized medicine.

Comparing Length and Telomere Expression at Oral Precancerous and Cancerous Stages

Background & Objective

Telomeres consist of repetitive G-rich nucleotides located at the end of each chromosome, acting as protein binding sites. The aim of this study was to examine the differences in telomere length in blood, saliva, and tissue samples at various stages of oral precancerous and cancerous lesions.

Methods

Samples of blood, tissue, and saliva were collected from patients with oral precancerous and cancerous lesions. DNA extraction was performed. Then, a TRAP assay was conducted to assess and compare the telomere length and telomerase expression.

Results

The levels of telomerase activity (TA) in the DNA samples ranged from 0.19 to 6.91 (2.05+1.37) among oral squamous cell carcinoma (OSCC) patients and from 0.17 to 4.5 (0.28+4.25) among precancerous patients. A significant difference was observed in TA levels between OSCC and precancerous samples (t=3.9691, P= 0.0000).

Conclusion

Assessing the telomerase activity is crucial for studying the behavior of carcinoma in the clinical setting. The augmented telomerase expression and the length of telomere contribute to OSCC progression. Hence, this study adds a diagnostic tool that can serve as a biomarker for the early detection and prognosis of OSCC.

Conditional loss of Ube3d in the retinal pigment epithelium accelerates age-associated alterations in the retina of mice

Several studies have suggested a correlation between the ubiquitin-proteasome system (UPS) and age-related macular degeneration (AMD), with its phenotypic severity ranging from mild visual impairment to blindness, but the mechanism for UPS dysfunction contributing to disease progression is unclear. In this study, we investigated the role of ubiquitin protein ligase E3D (UBE3D) in aging and degeneration in mouse retina. Conditional knockout of Ube3d in the retinal pigment epithelium (RPE) of mice led to progressive and irregular fundus lesions, attenuation of the retinal vascular system, and age-associated deterioration of rod and cone responses. Simultaneously, RPE-specific Ube3d knockout mice also presented morphological changes similar to the histopathological characteristics of human AMD, in which a defective UPS led to RPE abnormalities such as phagocytosis or degradation of metabolites, the interaction with photoreceptor outer segment, and the transport of nutrients or waste products with choroidal capillaries via Bruch's membrane. Moreover, conditional loss of Ube3d resulted in aberrant molecular characterizations associated with the autophagy-lysosomal pathway, oxidative stress damage, and cell-cycle regulation, which are implicated in AMD pathology. Thus, our findings strengthen and expand the impact of UPS dysfunction on retinal pathophysiology during aging, indicating that genetic Ube3d deficiency in the RPE could lead to the abnormal formation of pigment deposits and secondary fundus alterations. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Effects of nanomaterial exposure on telomere dysfunction, hallmarks of mammalian and zebrafish cell senescence, and zebrafish mortality

Environmental and occupational exposure to hazardous substances accelerates biological aging. However, the toxic effects of nanomaterials on telomere and cellular senescence (major hallmarks of the biological aging) remained controversial. This study was to synthesize all published evidence to explore the effects of nanomaterial exposure on the telomere change, cellular senescence and mortality of model animals. Thirty-five studies were included by searching electronic databases (PubMed, Embase and Web of Science). The pooled analysis by Stata 15.0 software showed that compared with the control, nanomaterial exposure could significantly shorten the telomere length [measured as kbp: standardized mean difference (SMD) = -1.88; 95% confidence interval (CI) = -3.13 - - 0.64; % of control: SMD = -1.26; 95%CI = -2.11- - 0.42; < 3 kbp %: SMD = 5.76; 95%CI = 2.92 - 8.60), increase the telomerase activity (SMD = -1.00; 95%CI = -1.74 to -0.26), senescence-associated β-galactosidase levels in cells (SMD = 8.20; 95%CI = 6.05 - 10.34) and zebrafish embryos (SMD = 7.32; 95%CI = 4.70 - 9.94) as well as the mortality of zebrafish (SMD = 3.83; 95%CI = 2.94 - 4.72)]. The expression levels of telomerase TERT, shelterin components (TRF1, TRF2 and POT1) and senescence biomarkers (p21, p16) were respectively identified to be decreased or increased in subgroup analyses. In conclusion, this meta-analysis demonstrates that nanomaterial exposure is associated with telomere attrition, cell senescence and organismal death.

Development of a model for the prediction of biological age

BACKGROUND AND OBJECTIVE

Rates of aging vary markedly among individuals, and biological age serves as a more reliable predictor of current health status than does chronological age. As such, the ability to predict biological age can support appropriate and timely active interventions aimed at improving coping with the aging process. However, the aging process is highly complex and multifactorial. Therefore, it is more scientific to construct a prediction model for biological age from multiple dimensions systematically.

METHODS

Physiological and biochemical parameters were evaluated to gage individual health status. Then, age-related indices were screened for inclusion in a model capable of predicting biological age. For subsequent modeling analyses, samples were divided into training and validation sets for subsequent deep learning model-based analyses (e.g. linear regression, lasso model, ridge regression, bayesian ridge regression, elasticity network, k-nearest neighbor, linear support vector machine, support vector machine, and decision tree models, and so on), with the model exhibiting the best ability to predict biological age thereby being identified.

RESULTS

First, we defined the individual biological age according to the individual health status. Then, after 22 candidate indices (DNA methylation, leukocyte telomere length, and specific physiological and biochemical indicators) were screened for inclusion in a model capable of predicting biological age, 14 age-related indices and gender were used to construct a model via the Bagged Trees method, which was found to be the most reliable qualitative prediction model for biological age (accuracy=75.6%, AUC=0.84) by comparing 30 different classification algorithm models. The most reliable quantitative predictive model for biological age was found to be the model developed using the Rational Quadratic method (R2=0.85, RMSE=8.731 years) by comparing 24 regression algorithm models.

CONCLUSIONS

Both qualitative model and quantitative model of biological age were successfully constructed from a multi-dimensional and systematic perspective. The predictive performance of our models was similar in both smaller and larger datasets, making it well-suited to predicting a given individual's biological age.

Associations between telomere attrition, genetic variants in telomere maintenance genes, and non-small cell lung cancer risk in the Jammu and Kashmir population of North India

BACKGROUND

Telomeres are repetitive DNA sequences located at the ends of chromosomes, playing a vital role in maintaining chromosomal integrity and stability. Dysregulation of telomeres has been implicated in the development of various cancers, including non-small cell lung cancer (NSCLC), which is the most common type of lung cancer. Genetic variations within telomere maintenance genes may influence the risk of developing NSCLC. The present study aimed to evaluate the genetic associations of select variants within telomere maintenance genes in a population from Jammu and Kashmir, North India, and to investigate the relationship between telomere length and NSCLC risk.

METHODS

We employed the cost-effective and high-throughput MassARRAY MALDI-TOF platform to assess the genetic associations of select variants within telomere maintenance genes in a population from Jammu and Kashmir, North India. Additionally, we used TaqMan genotyping to validate our results. Furthermore, we investigated telomere length variation and its relation to NSCLC risk in the same population using dual-labeled fluorescence-based qPCR.

RESULTS

Our findings revealed significant associations of TERT rs10069690 and POT1 rs10228682 with NSCLC risk (adjusted p-values = 0.019 and 0.002, respectively), while TERF2 rs251796 and rs2975843 showed no significant associations. The TaqMan genotyping validation further substantiated the associations of TERT rs10069690 and rs2242652 with NSCLC risk (adjusted p-values = 0.02 and 0.003, respectively). Our results also demonstrated significantly shorter telomere lengths in NSCLC patients compared to controls (p = 0.0004).

CONCLUSION

This study highlights the crucial interplay between genetic variation in telomere maintenance genes, telomere attrition, and NSCLC risk in the Jammu and Kashmir population of North India. Our findings suggest that TERT and POT1 gene variants, along with telomere length, may serve as potential biomarkers and therapeutic targets for NSCLC in this population. Further research is warranted to elucidate the underlying mechanisms and to explore the potential clinical applications of these findings.

Telomerase RNA component lncRNA as potential diagnostic biomarker promotes CRC cellular migration and apoptosis evasion via modulation of β-catenin protein level

Aim

Long non-coding RNA (LncRNA) telomerase RNA component (TERC) has telomerase-dependent and independent activity in numerous cancer types. The present study purposes to demonstrate the role of lncRNA TERC as a diagnostic serum biomarker in colorectal cancer (CRC) patients and the molecular mechanism of lncRNA TERC in inducing tumor in CRC cell lines.

Materials and methods

PCR array was performed to examine lncRNAs dysregulated in CRC. LncRNA TERC expression level was evaluated in 70 CRC patients and 35 control subjects using RT-qPCR. Then transfection was performed to build down-expression models of lncRNA TERC. ROC curve analysis was applied to assess the diagnostic value of serum LncRNA CRC. In addition, RT-qPCR was used to detect expression level of lncRNA TERC and β-catenin mRNA. Moreover, ELISA and Western blot were used to detect the level of β-catenin protein in sera of CRC patients and cell lines. The biological functions such as cell growth and migration of CRC cells were assessed using a wound healing assay. Cell cycle analysis and apoptosis analysis were performed using flow cytometry.

Results

The lncRNA TERC is overexpressed in the sera of CRC patients with high diagnostic and stage discrimination accuracy. Furthermore, lncRNA TERC expression was upregulated in CRC cell lines and lncRNA TERC silencing induced cell arrest and apoptosis and inhibited cell migration. Furthermore, inhibition of lncRNA TERC reduces β-catenin protein levels.

Conclusion

The lncRNA TERC could be considered as an early stages CRC diagnostic biomarker with a good ability to discriminate between CRC stages. lncRNA TERC induces CRC by promoting cell migration and evading apoptosis by elevating the level of β-catenin protein.

NKG2D-CAR T cells eliminate senescent cells in aged mice and nonhuman primates

Cellular senescence, characterized by stable cell cycle arrest, plays an important role in aging and age-associated pathologies. Eliminating senescent cells rejuvenates aged tissues and ameliorates age-associated diseases. Here, we identified that natural killer group 2 member D ligands (NKG2DLs) are up-regulated in senescent cells in vitro, regardless of stimuli that induced cellular senescence, and in various tissues of aged mice and nonhuman primates in vivo. Accordingly, we developed and demonstrated that chimeric antigen receptor (CAR) T cells targeting human NKG2DLs selectively and effectively diminish human cells undergoing senescence induced by oncogenic stress, replicative stress, DNA damage, or P16INK4a overexpression in vitro. Targeting senescent cells with mouse NKG2D-CAR T cells alleviated multiple aging-associated pathologies and improved physical performance in both irradiated and aged mice. Autologous T cells armed with the human NKG2D CAR effectively delete naturally occurring senescent cells in aged nonhuman primates without any observed adverse effects. Our findings establish that NKG2D-CAR T cells could serve as potent and selective senolytic agents for aging and age-associated diseases driven by senescence.

Cytogenetics in Fanconi Anemia: The Importance of Follow-Up and the Search for New Biomarkers of Genomic Instability

Fanconi Anemia (FA) is a disease characterized by genomic instability, increased sensitivity to DNA cross-linking agents, and the presence of clonal chromosomal abnormalities. This genomic instability can compromise the bone marrow (BM) and confer a high cancer risk to the patients, particularly in the development of Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML). The diagnosis of FA patients is complex and cannot be based only on clinical features at presentation. The gold standard diagnostic assay for these patients is cytogenetic analysis, revealing chromosomal breaks induced by DNA cross-linking agents. Clonal chromosome abnormalities, such as the ones involving chromosomes 1q, 3q, and 7, are also common features in FA patients and are associated with progressive BM failure and/or a pre-leukemia condition. In this review, we discuss the cytogenetic methods and their application in diagnosis, stratification of the patients into distinct prognostic groups, and the clinical follow-up of FA patients. These methods have been invaluable for the understanding of FA pathogenesis and identifying novel disease biomarkers. Additional evidence is required to determine the association of these biomarkers with prognosis and cancer risk, and their potential as druggable targets for FA therapy.

Three-dimensional nuclear telomere architecture and differential expression of aurora kinase genes in chronic myeloid leukemia to measure cell transformation

Background

Telomere dysfunction results in aneuploidy, and ongoing chromosomal abnormalities. The three-dimensional (3D) nuclear organization of telomeres allows for a distinction between normal and tumor cells. On the other hand, aurora kinase genes (AURKA and AURKB) play an important role regulating the cell cycle. A correlation between overexpression of aurora kinase genes and clinical aggressiveness has been demonstrated in different types of neoplasias. To better understand cellular and molecular mechanisms of CML evolution, it was examined telomere dysfunction (alterations in the 3D nuclear telomere architecture), and the expression levels of AURKA and AURKB genes in two clinical distinct subgroups of CML samples, from the same patient.

Methods

Eighteen CML patients, in total, 36 bone marrow samples (18 patients, chronic vs. accelerated/blast phase) were eligible for 3D telomeric investigations. Quantitative 3D imaging, cytologic diagnosis and cytogenetic determination of additional chromosomal abnormalities were assessed according to standard protocols.

Results

Using TeloView software, two CML subgroups were defined based on their 3D telomeric profiles, reflecting the different stages of the disease (chronic vs. accelerated/blast phase). Statistical analyses showed significant differences between the CML subgroups (p < 0.001). We also found that AURKA and AURKB mRNA were expressed at significantly higher levels in both CML subgroups, when compared with healthy donors. Our findings suggest that the evolution of CML progresses from a low to a high level of telomere dysfunction, that is, from an early stage to a more aggressive stage, followed by disease transformation, as demonstrated by telomere, additional chromosomal abnormalities, and gene expression profile dynamics.

Conclusions

Thus, we demonstrated that 3D telomere organization, in accordance with the genomic instability observed in CML samples were able to distinguish subgroup CML patients. Classifying CML patients based on these characteristics might represent an important strategy to define better therapeutic strategies.

TERT distal promoter GC islands are critical for telomerase and together with DNMT3B silencing may serve as a senescence-inducing agent in gliomas

Telomerase is reactivated in the majority of cancers. For instance, in gliomas, it is common that the TERT promoter is mutated. Research on telomere promoter GC islands have been focused primarily on proximal TERT promoter but little is known about the distal promoter. Therefore, in this study, we investigated the proximal and distal TERT promoter, in terms of DNA methylation. We did bisulfite sequencing in zebrafish tissue samples for the distal tert promoter. In the zebrafish brain tissues, we identified a hypomethylation site in the tert promoter, and found that this hypomethylation was associated with aging and shortened telomeres. Through site directed mutagenesis in glioma cell lines, we changed 10 GC spots individually, cloned into a reporter vector, and measured promoter activity. Finally, we silenced DNMT3B and measured telomerase activity along with vidaza and adriamycin treatments. Site directed mutagenesis of glioma cell lines revealed that each of the 10 GC spots are critical for telomerase activity. Changing GC to AT abolished promoter activity in all spots when transfected into glioma cell lines. Then, through silencing of DNMT3B, we observed a reduction in hTERT expression levels, while hTR remained the same, and a major increase in senescence-associated beta-galactosidase activity. Finally, we propose a model regarding the efficacy of two chemotherapeutic drugs, adriamycin and azacytidine, on gliomas. Here, we show that distal TERT promoter is critical; changing even one GC to AT abolishes TERT promoter activity. DNMT3B, a de novo methyltransferase, together with GC islands in distal TERT promoter plays an important role in regulation of telomerase expression and senescence.

Oral Papillomatosis: Its Relation with Human Papilloma Virus Infection and Local Immunity—An Update

Oral papilloma lesions may appear as a result of HPV infection, or not, and only special molecular methods could differentiate them. Low-risk and high-risk HPV types could induce oral HPV papillomatosis with different natural evolution, clearance and persistence mechanisms. The pathogenic mechanisms are based on the crosstalk between the oral epithelial and immune cells and this very efficient virus. HPV acts as a direct inducer in the process of transforming a benign lesion into a malignant one, the cancerization process being also debated in this paper. According to the degree of malignity, three types of papillomatous lesions can be described in the oral cavity: benign lesions, potential malign disorders and malignant lesions. The precise molecular diagnostic is important to identify the presence of various virus types and also the virus products responsible for its oncogenicity. An accurate diagnostic of oral papilloma can be established through a good knowledge of etiological and epidemiological factors, clinical examination and laboratory tests. This review intends to update the pathogenic mechanisms driving the macroscopic and histological features of oral papillomatosis having HPV infection as the main etiological factor, focusing on its interreference in the local immunity. In the absence of an accurate molecular diagnostic and knowledge of local immunological conditions, the therapeutic strategy could be difficult to decide.

Cellular Senescence and Ageing: Mechanisms and Interventions

The influence of the activation of a cellular phenotype termed senescence and it’s importance in ageing and age-related diseases is becoming more and more evident. In fact, there is a huge effort to tackle these diseases via therapeutic drugs targeting senescent cells named senolytics. However, a clearer understanding of how senescence is activated and the influence it has on specific cellular types and tissues is needed. Here, we describe general triggers and characteristics of senescence. In addition, we describe the influence of senescent cells in ageing and different age-related diseases.

Association of increased age with decreased response to intravesical instillation of Bacille Calmette-Guérin in patients with high-risk non-muscle invasive bladder cancer: Retrospective multi-institute results from the Japanese Urological Oncology Research Group JUOG-UC-1901-BCG

OBJECTIVE

To compare the therapeutic effect of Bacille Calmette-Guérin (BCG) intravesical instillation in older and younger patients with high-risk non-muscle-invasive bladder cancer (NMIBC). The comparison was performed with propensity score matching (PSM) without terminating the death of the older patients using relatively large-scale retrospective data from multiple institutes in Japan.

MATERIALS AND METHODS

Overall, 3,283 patients diagnosed with NMIBC treated with intravesical BCG instillation during 2000-2018 in 31 institutes were examined; 1,437 and 602 patients with high-grade T1 and Tis tumors were divided into those aged ≥ 75 and < 75 years. Multivariate analysis using the Fine-Gray competing risks regression model before PSM and survival analysis using the cumulative incidence method after PSM were performed.

RESULTS

In the pre-PSM series of high-grade T1 tumors, age ≥ 75 years was an independent prognostic factor for both recurrence and progression in multivariate analysis (p = 0.015 and p = 0.013). In the pre-PSM series with Tis tumor, no variables to predict recurrence and progression was found. In the post-PSM series of 870 high-grade T1 tumors, cumulative probability of recurrence after BCG intravesical instillation were significantly higher in patients aged ≥ 75 years than in those aged < 75 years (p = 0.008). The frequency of discontinuation of BCG instillation in patients aged ≥ 75 years with high-grade T1 and Tis was not significantly different from those in patients aged < 75 years (p = 0.564 and p = 0.869).

CONCLUSIONS

The cumulative probability of recurrence after intravesical BCG instillation was significantly higher in older than in younger patients with high-grade T1 bladder cancer.

Andrographolide, a diterpene lactone from the Traditional Chinese Medicine Andrographis paniculate, induces senescence in human lung adenocarcinoma via p53/p21 and Skp2/p27

BACKGROUND

Senescence leads to permanent cell-cycle arrest and is a potential target for cancer therapy. Andrographolide (AD) is a diterpene lactone isolated from Traditional Chinese Medicine (TCM) Andrographis paniculate, which has been used as an anti-inflammatory drug in clinical practice with the potential to target senescence in recalcitrant lung cancer.

PURPOSE

To determine whether AD can induce senescence in human lung adenocarcinoma in vitro and in vivo and to elucidate the underlying mechanisms.

METHODS

SA-β-Gal staining was used to detect the expression of senescence-associated β-galactosidase (SA-β-Gal) in human lung adenocarcinoma cells A549 and NCI-H1795. DNA damage was examined by the detection of γH2AX foci. Cell cycle was analyzed by flow cytometry. Cancer cell proliferation was determined by ATPlite assay and clonogenic survival assay in vitro. Tumor growth was determined in a mouse model of A549. The expression level of proteins and mRNA was estimated by Western blotting and Quantitative RT-PCR, respectively. Small interfering RNA (siRNA) was used to knock down p21, p27 and p53 to explore the potential mechanism of AD-induced senescence in human lung adenocarcinoma cells.

RESULTS

AD-induced A549 and NCI-H1795 cell senescence determined by increased cell size, flattened morphology, DNA damage, cell cycle arrest as well as the increased expression of β-galactosidase. AD inhibited cell proliferation in lung cells in vitro and lung cells xenograft growth in nude mice. p21 and p27, the major cell cycle regulators and mediators of senescence, were upregulated at the protein level in AD-treated A549 lung adenocarcinoma in vitro and in vivo. Further studies demonstrated that AD induced cell senescence via p53/p21 and Skp2/p27.

CONCLUSION

In the present study, we found that the primary anti-inflammatory drug AD could have a potential antitumor effect in lung cancer. We demonstrated that AD induced lung adenocarcinoma senescence in vitro and in vivo via p53/p21 and Skp2/p27 for the first time. AD is therefore a promising senescence-inducing therapeutic for recalcitrant human lung adenocarcinoma.

Impact of superovulation and in vitro fertilization on LINE-1 copy number and telomere length in C57BL/6 J mice blastocysts

OBJECTIVE

Millions of babies have been conceived by IVF, yet debate about its safety to offspring continues. We hypothesized that superovulation and in vitro fertilization (IVF) promote genomic changes, including altered telomere length (TL) and activation of the retrotransposon LINE-1 (L1), and tested this hypothesis in a mouse model.

MATERIAL AND METHODS

Experimental study analyzing TL and L1 copy number in C57BL/6 J mouse blastocysts in vivo produced from natural mating cycles (N), in vivo produced following superovulation (S), or in vitro produced following superovulation (IVF). We also examined the effects of prolonged culture on TL and L1 copy number in the IVF group comparing blastocysts cultured 96 h versus blastocysts cultured 120 h. TL and L1 copy number were measured by Real Time PCR.

RESULTS

TL in S (n = 77; Mean: 1.50 ± 1.15; p = 0.0007) and IVF (n = 82; Mean: 1.72 ± 1.44; p < 0.0001) exceeded that in N (n = 16; Mean: 0.61 ± 0.27). TL of blastocysts cultured 120 h (n = 15, Mean: 2.14 ± 1.05) was significantly longer than that of embryos cultured for 96 h (n = 67, Mean: 1.63 ± 1.50; p = 0.0414). L1 copy number of blastocysts cultured for 120 h (n = 15, Mean: 1.71 ± 1.49) exceeded that of embryos cultured for 96 h (n = 67, Mean: 0.95 ± 1.03; p = 0.0162).

CONCLUSIONS

Intriguingly ovarian stimulation, alone or followed by IVF, produced embryos with significantly longer telomeres compared to in vivo, natural cycle-produced embryos. The significance of this enriched telomere endowment for the health and longevity of offspring born from IVF merit future studies.

Mechanobiological Implications of Cancer Progression in Space

The human body is normally adapted to maintain homeostasis in a terrestrial environment. The novel conditions of a space environment introduce challenges that changes the cellular response to its surroundings. Such an alteration causes physical changes in the extracellular microenvironment, inducing the secretion of cytokines such as interleukin-6 (IL-6) and tumor growth factor-β (TGF-β) from cancer cells to enhance cancer malignancy. Cancer is one of the most prominent cell types to be affected by mechanical cues via active interaction with the tumor microenvironment. However, the mechanism by which cancer cells mechanotransduce in the space environment, as well as the influence of this process on human health, have not been fully elucidated. Due to the growing interest in space biology, this article reviews cancer cell responses to the representative conditions altered in space: microgravity, decompression, and irradiation. Interestingly, cytokine and gene expression that assist in tumor survival, invasive phenotypic transformation, and cancer cell proliferation are upregulated when exposed to both simulated and actual space conditions. The necessity of further research on space mechanobiology such as simulating more complex in vivo experiments or finding other mechanical cues that may be encountered during spaceflight are emphasized.

Hispanic/Latino Acculturation Profiles and Telomere Length: Latent Class Analysis on a Nationally Representative Sample

Background: Acculturation profiles and their impact on telomere length among foreign-born Hispanics/Latinos living in the United States (US) are relatively unknown. The limited research available has linked acculturation with shortened telomere length. Objectives: To identify acculturation profiles among a US representative sample of Hispanics/Latinos and to then examine telomere length differences between profiles. Methods: We conducted a latent class analysis among a non-institutionalized US-representative sample of Hispanics/Latinos using the 1999-2002 National Health and Nutrition Examination Survey (N = 2,292). The latent variable of acculturation was assessed by length of time in the US and language used as a child, read and spoken, usually spoken at home, used to think, and used with friends (i.e., Spanish and/or English). Telomere length assessed from leukocytes was used as the distal continuous outcome. Results: We identified five profiles: (1) low acculturated [33.2% of sample]; (2) partially integrated [18.6% of sample]; (3) integrated [19.4% of sample]; (4) partially assimilated [15.1% of sample]; and (5) assimilated [13.7% of sample]. Acculturation profiles revealed nuanced differences in conditional probabilities with language use despite the length of time spent in the US. While telomere length did vary, there were no significant differences between profiles. Conclusion: Profiles identified revealed that possible life-course and generational effects may be at play in the partially assimilated and assimilated profiles. Our findings expand public health research using complex survey data to identify and assess the dynamic relationship of acculturation profiles and health biomarkers, while being among the first to examine this context using a person-centered approach.

Transcription Independent Stimulation of Telomerase Enzymatic Activity by HTLV-I Tax Through Stimulation of IKK

The persistence and spreading of HTLV-I infected cells relies upon their clonal expansion through cellular replication. The development of adult T cell leukemia (ATLL) occurs decades following primary infection by HTLV-I. Moreover, identical provirus integration sites have been found in samples recovered several years apart from infected individuals. These observations suggest that infected cells persist in the host for an extended period of time. To endure long term proliferation, HTLV-I pre-leukemic cells must acquire critical oncogenic events, two of which are the bypassing of apoptosis and replicative senescence. In the early stages of disease, interleukin-2 (IL-2)/IL-2R signaling likely plays a major role in combination with activation of anti-apoptotic pathways. Avoidance of replicative senescence in HTLV-I infected cells is achieved through reactivation of human telomerase (hTERT). We have previously shown that HTLV-I viral Tax transcriptionally activates the hTERT promoter. In this study we demonstrate that Tax can stimulate hTERT enzymatic activity independently of its transcriptional effects. We further show that this occurs through Tax-mediated NF-KB activating functions. Our results suggest that in ATLL cells acquire Tax-transcriptional and post-transcriptional events to elevate telomerase activity.

Developmental Acquisition of p53 Functions

Remarkably, the p53 transcription factor, referred to as “the guardian of the genome”, is not essential for mammalian development. Moreover, efforts to identify p53-dependent developmental events have produced contradictory conclusions. Given the importance of pluripotent stem cells as models of mammalian development, and their applications in regenerative medicine and disease, resolving these conflicts is essential. Here we attempt to reconcile disparate data into justifiable conclusions predicated on reports that p53-dependent transcription is first detected in late mouse blastocysts, that p53 activity first becomes potentially lethal during gastrulation, and that apoptosis does not depend on p53. Furthermore, p53 does not regulate expression of genes required for pluripotency in embryonic stem cells (ESCs); it contributes to ESC genomic stability and differentiation. Depending on conditions, p53 accelerates initiation of apoptosis in ESCs in response to DNA damage, but cell cycle arrest as well as the rate and extent of apoptosis in ESCs are p53-independent. In embryonic fibroblasts, p53 induces cell cycle arrest to allow repair of DNA damage, and cell senescence to prevent proliferation of cells with extensive damage.

Exercise training increases telomerase reverse transcriptase gene expression and telomerase activity: A systematic review and meta-analysis

Telomeres protect genomic stability and shortening is one of the hallmarks of ageing. Telomerase reverse transcriptase (TERT) is the major protein component of telomerase, which elongates telomeres. Given that short telomeres are linked to a host of chronic diseases and the therapeutic potential of telomerase-based therapies as treatments and a strategy to extend lifespan, lifestyle factors that increase TERT gene expression and telomerase activity could attenuate telomere attrition and contribute to healthy biological ageing. Physical activity and maximal aerobic fitness are associated with telomere maintenance, yet the molecular mechanisms remain unclear. Therefore, the purpose of this systematic review and meta-analysis was to identify the influence of a single bout of exercise and long-term exercise training on TERT expression and telomerase activity. A search of human and rodent trials using the PubMed, Scopus, Science Direct and Embase databases was performed. Based on findings from the identified and eligible trials, both a single bout of exercise (n; standardised mean difference [95%CI]: 5; SMD: 1.19 [0.41-1.97], p = 0.003) and long-term exercise training (10; 0.31 [0.03-0.60], p = 0.03) up-regulates TERT and telomerase activity in non-cancerous somatic cells. As human and rodent studies were included in the meta-analyses both exhibited heterogeneity (I² = 55-87%, p < 0.05). Endurance athletes also exhibited increased leukocyte TERT and telomerase activity compared to their inactive counterparts. These findings suggest exercise training as an inexpensive lifestyle factor that increases TERT expression and telomerase activity. Regular exercise training could attenuate telomere attrition through a telomerase-dependent mechanism and ultimately extend health-span and longevity.

Telomere Shortening and Fusions: A Link to Aneuploidy in Early Human Embryo Development

Importance

It is known that oocytes undergo aging that is caused by exposure to an aged ovarian microenvironment. Telomere length in mouse and bovine oocytes declines with age, and age-associated telomere shortening in oocytes is considered a sign of poor development competency. Women with advanced age undergoing assisted reproductive technologies have poor outcomes because of increasing aneuploidy rates with age. Research has shown that aneuploidy is associated with DNA damage, reactive oxygen species, and telomere dysfunction.

Objective

In this review, we focus on the possible relationship between telomere dysfunction and aneuploidy in human early embryo development and several reproductive and perinatal outcomes, discussing the mechanism of aneuploidy caused by telomere shortening and fusion in human embryos.

Evidence Acquisition

We reviewed the current literature evidence concerning telomere dysfunction and aneuploidy in early human embryo development.

Results

Shorter telomeres in oocytes, leukocytes, and granulosa cells, related to aging in women, were associated with recurrent miscarriage, trisomy 21, ovarian insufficiency, and decreasing chance of in vitro fertilization success. Telomere length and telomerase activity in embryos have been related to the common genomic instability at the cleavage stage of human development. Complications of assisted reproductive technology pregnancies, such as miscarriage, birth defects, preterm births, and intrauterine growth restriction, also might result from telomere shortening as observed in oocytes, polar body, granulosa cells, and embryos.

Conclusions and Relevance

Telomere length clearly plays an important role in the development of the embryo and fetus, and the abnormal shortening of telomeres is likely involved in embryo loss during early human development. However, telomere fusion studies have yet to be performed in early human development.

External environmental agents influence telomere length and telomerase activity by modulating internal cellular processes: Implications in human aging

External environment affects cellular physiological processes and impact the stability of our genome. The most important structural components of our linear chromosomes which endure the impact by these agents, are the chromosomal ends called telomeres. Telomeres preserve the integrity of our genome by preventing end to end fusions and telomeric loss through by inhibiting DNA damage response (DDR) activation. This is accomplished by the presence of a six membered shelterin complex at telomeres. Further, telomeres cannot be replicated by normal DNA polymerase and require a special enzyme called telomerase which is expressed only in stem cells, few immune cells and germ cells. Telomeres are rich in guanine content and thus become extremely prone to damage arising due to physiological processes like oxidative stress and inflammation. External environmental factors which includes various physical, biological and chemical agents also affect telomere homeostasis by increasing oxidative stress and inflammation. In the present review, we highlight the effect of these external factors on telomerase activity and telomere length. We also discuss how the external agents affect the physiological processes, thus modulating telomere stability. Further, we describe its implication in the development of aging and its related pathologies.

Autism-Associated Vigilin Depletion Impairs DNA Damage Repair

Vigilin (Vgl1) is essential for heterochromatin formation, chromosome segregation, and mRNA stability and is associated with autism spectrum disorders and cancer: vigilin, for example, can suppress proto-oncogene c-fms expression in breast cancer. Conserved from yeast to humans, vigilin is an RNA-binding protein with 14 tandemly arranged nonidentical hnRNP K-type homology (KH) domains. Here, we report that vigilin depletion increased cell sensitivity to cisplatin- or ionizing radiation (IR)-induced cell death and genomic instability due to defective DNA repair. Vigilin depletion delayed dephosphorylation of IR-induced γ-H2AX and elevated levels of residual 53BP1 and RIF1 foci, while reducing Rad51 and BRCA1 focus formation, DNA end resection, and double-strand break (DSB) repair. We show that vigilin interacts with the DNA damage response (DDR) proteins RAD51 and BRCA1, and vigilin depletion impairs their recruitment to DSB sites. Transient hydroxyurea (HU)-induced replicative stress in vigilin-depleted cells increased replication fork stalling and blocked restart of DNA synthesis. Furthermore, histone acetylation promoted vigilin recruitment to DSBs preferentially in the transcriptionally active genome. These findings uncover a novel vigilin role in DNA damage repair with implications for autism and cancer-related disorders.

RGL2 as an age-dependent factor regulates colon cancer progression

Colon cancer is the fourth leading cause of cancer-related death, and exhibited clinical differences among patients of different ages, including malignancy, metastasis, and mortality rate. Few studies, however, focus on the communications between aging and colon cancer. Here we identified age-dependent differentially expressed genes (DEGs) in colon cancer using TCGA transcriptome data. Through analyzing multi-omics high throughput data, including ATAC-Seq, DNaseI-Seq and ChIP-Seq, we obtained six age-dependent transcription factors in colon cancer, and their age-dependent targets, significantly affecting patients' overall survivals. Transcription factor ETS1 potentially functioned in both aging process and colon cancer progression through regulating its targets, RGL2 and SLC2A3. In addition, comparing with its relative lower expression levels in elderly patients, higher levels of RGL2 were detected in young patients, and significantly associated with larger tumor size, higher metastasis, and invasions of colon cancer, consistent with the clinical traits that young patients' colon cancer exhibited late stages with more aggressiveness. Thus, these elements may serve as keys linking aging and colon cancer, and providing new insights and basis for mechanism researches, as well as diagnosis and therapies of colon cancer, especially in young patients.

ORN: Inferring patient-specific dysregulation status of pathway modules in cancer with OR-gate Network

Pathway level understanding of cancer plays a key role in precision oncology. However, the current amount of high-throughput data cannot support the elucidation of full pathway topology. In this study, instead of directly learning the pathway network, we adapted the probabilistic OR gate to model the modular structure of pathways and regulon. The resulting model, OR-gate Network (ORN), can simultaneously infer pathway modules of somatic alterations, patient-specific pathway dysregulation status, and downstream regulon. In a trained ORN, the differentially expressed genes (DEGs) in each tumour can be explained by somatic mutations perturbing a pathway module. Furthermore, the ORN handles one of the most important properties of pathway perturbation in tumours, the mutual exclusivity. We have applied the ORN to lower-grade glioma (LGG) samples and liver hepatocellular carcinoma (LIHC) samples in TCGA and breast cancer samples from METABRIC. Both datasets have shown abnormal pathway activities related to immune response and cell cycles. In LGG samples, ORN identified pathway modules closely related to glioma development and revealed two pathways closely related to patient survival. We had similar results with LIHC samples. Additional results from the METABRIC datasets showed that ORN could characterize critical mechanisms of cancer and connect them to less studied somatic mutations (e.g., BAP1, MIR604, MICAL3, and telomere activities), which may generate novel hypothesis for targeted therapy.

Cellular functions are carried out by a set of gene products. Mutation of a single gene is often sufficient to disrupt certain biological functions and promote tumorigenesis. Therefore, genes participating in the same function are less likely to mutate in the same sample. Such phenomenon is called “mutual exclusivity”. In this study, our algorithm (ORN) has utilized this property to identify gene-level mutations that affect similar biological functions. It also considers mutations’ impact on mRNA expression. Functional modules identified by ORN tends to be mutually exclusive while causing similar differential expression profiles. When we applied ORN to lower-grade glioma and liver cancer datasets, we have identified gene modules significantly related to patient survival. Furthermore, across different types of cancer, ORN has connected well-known cancer driver mutations with genes whose functions remain unclear. These connections, once validated, can generate novel hypothesis for biologist to further investigate cancer mechanism and develop targeted therapy.

Human skin aging is associated with increased expression of the histone variant H2A.J in the epidermis

Cellular senescence is an irreversible growth arrest that occurs as a result of damaging stimuli, including DNA damage and/or telomere shortening. Here, we investigate histone variant H2A.J as a new biomarker to detect senescent cells during human skin aging. Skin biopsies from healthy volunteers of different ages (18–90 years) were analyzed for H2A.J expression and other parameters involved in triggering and/or maintaining cellular senescence. In the epidermis, the proportions of H2A.J-expressing keratinocytes increased from ≈20% in young to ≈60% in aged skin. Inverse correlations between Ki67- and H2A.J staining in germinative layers may reflect that H2A.J-expressing cells having lost their capacity to divide. As cellular senescence is triggered by DNA-damage signals, persistent 53BP1-foci, telomere lengths, and telomere-associated damage foci were analyzed in epidermal keratinocytes. Only slight age-related telomere attrition and few persistent nuclear 53BP1-foci, occasionally colocalizing with telomeres, suggest that unprotected telomeres are not a significant cause of senescence during skin aging. Quantification of integrin-α6+ basal cells suggests that the number and function of stem/progenitor cells decreased during aging and their altered proliferation capacities resulted in diminished tissue renewal with epidermal thinning. Collectively, our findings suggest that H2A.J is a sensitive marker of epidermal aging in human skin.

POT1 Regulates Proliferation and Confers Sexual Dimorphism in Glioma

Germline POT1 mutations are found in a spectrum of cancers and confer increased risk. Recently, we identified a series of novel germline POT1 mutations that predispose carrier families to the development of glioma. Despite these strong associations, how these glioma-associated POT1 mutations contribute to glioma tumorigenesis remains undefined. Here we show that POT1-G95C increases proliferation in glioma-initiating cells in vitro and in progenitor populations in the developing brain. In a native mouse model of glioma, loss of Pot1a/b resulted in decreased survival in females compared with males. These findings were corroborated in human glioma, where low POT1 expression correlated with decreased survival in females. Transcriptomic and IHC profiling of Pot1a/b-deficient glioma revealed that tumors in females exhibited decreased expression of immune markers and increased expression of cell-cycle signatures. Similar sex-dependent trends were observed in human gliomas that had low expression of POT1. Together, our studies demonstrate context-dependent functions for POT1 mutation or loss in driving progenitor proliferation in the developing brain and sexual dimorphism in glioma. SIGNIFICANCE: This study shows that manipulation of POT1 expression in glioma has sex-specific effects on tumorigenesis and associated immune signatures.

Cellular senescence and hematological malignancies: From pathogenesis to therapeutics

Cellular senescence constitutes a permanent state of cell cycle arrest in proliferative cells induced by different stresses. The exploration of tumor pathogenesis and therapies has been a research hotspot in recent years. Cellular senescence is a significant mechanism to prevent the proliferation of potential tumor cells, but it can also promote tumor growth. Increasing evidence suggests that cellular senescence is involved in the pathogenesis and development of hematological malignancies, including leukemia, myelodysplastic syndrome (MDS) and multiple myeloma (MM). Cellular senescence is associated with functional decline of hematopoietic stem cells (HSCs) and increased risk of hematological malignancies. Moreover, the bone marrow (BM) microenvironment has a crucial regulatory effect in the process of these diseases. The senescence-associated secretory phenotype (SASP) in the BM microenvironment establishes a protumor environment that supports the proliferation and survival of tumor cells. Therefore, a series of therapeutic strategies targeting cellular senescence have been gradually developed, including the induction of cellular senescence and elimination of senescent cells. This review systematically summarizes the emerging information describing the roles of cellular senescence in tumorigenesis and potential clinical applications, which may be beneficial for designing rational therapeutic strategies for various hematopoietic malignancies.

DNA folds threaten genetic stability and can be leveraged for chemotherapy

Damaging DNA is a current and efficient strategy to fight against cancer cell proliferation. Numerous mechanisms exist to counteract DNA damage, collectively referred to as the DNA damage response (DDR) and which are commonly dysregulated in cancer cells. Precise knowledge of these mechanisms is necessary to optimise chemotherapeutic DNA targeting. New research on DDR has uncovered a series of promising therapeutic targets, proteins and nucleic acids, with application notably via an approach referred to as combination therapy or combinatorial synthetic lethality. In this review, we summarise the cornerstone discoveries which gave way to the DNA being considered as an anticancer target, and the manipulation of DDR pathways as a valuable anticancer strategy. We describe in detail the DDR signalling and repair pathways activated in response to DNA damage. We then summarise the current understanding of non-B DNA folds, such as G-quadruplexes and DNA junctions, when they are formed and why they can offer a more specific therapeutic target compared to that of canonical B-DNA. Finally, we merge these subjects to depict the new and highly promising chemotherapeutic strategy which combines enhanced-specificity DNA damaging and DDR targeting agents. This review thus highlights how chemical biology has given rise to significant scientific advances thanks to resolutely multidisciplinary research efforts combining molecular and cell biology, chemistry and biophysics. We aim to provide the non-specialist reader a gateway into this exciting field and the specialist reader with a new perspective on the latest results achieved and strategies devised.

The Small Molecule BIBR1532 Exerts Potential Anti-cancer Activities in Preclinical Models of Feline Oral Squamous Cell Carcinoma Through Inhibition of Telomerase Activity and Down-Regulation of TERT

Expression of telomerase reverse transcriptase (TERT) and telomerase activity (TA) is a main feature of cancer, contributing to cell immortalization by causing telomeres dysfunction. BIBR1532 is a potent telomerase inhibitor that showed potential anti-tumor activities in several types of cancer, by triggering replicative senescence and apoptosis. In a previous work, we detected, for the first time, TERT expression and TA in preclinical models of feline oral squamous cell carcinoma (FOSCC); therefore, we aimed at extending our investigation by testing the effects of treatment with BIBR1532, in order to explore the role of telomerase in this tumor and foreshadow the possibility of it being considered as a future therapeutic target. In the present study, treatment of FOSCC cell lines SCCF1, SCCF2, and SCCF3 with BIBR1532 resulted in successful inhibition of TA, with subsequent cell growth stoppage and decrease in cell viability. Molecular data showed that up-regulation of cell cycle inhibitor p21, unbalancing of Bax/Bcl-2 ratio, and down-regulation of survival gene Survivin were mostly involved in the observed cellular events. Moreover, BIBR1532 diminished the expression of TERT and its transcriptional activator cMyc, resulting in the down-regulation of epidermal growth factor receptor (EGFR), phospho-ERK/ERK ratio, and matrix metalloproteinases (MMPs)-1/-2 and−9, likely as a consequence of an impairment of TERT extra-telomeric functions. Taken together, our data suggest that BIBR1532 exerts multiple anti-cancer activities in FOSCC by inhibiting telomerase pathway and interfering with signaling routes involved in cell proliferation, cell survival, and invasion, paving the way for future translational studies aimed at evaluating its possible employment in the treatment of this severe tumor of cats.

Genes and pathways involved in senescence bypass identified by functional genetic screens

Cellular senescence is a state of stable and irreversible cell cycle arrest with active metabolism, that normal cells undergo after a finite number of divisions (Hayflick limit). Senescence can be triggered by intrinsic and/or extrinsic stimuli including telomere shortening at the end of a cell's lifespan (telomere-initiated senescence) and in response to oxidative, genotoxic or oncogenic stresses (stress-induced premature senescence). Several effector mechanisms have been proposed to explain senescence programmes in diploid cells, including the induction of DNA damage responses, a senescence-associated secretory phenotype and epigenetic changes. Senescent cells display senescence-associated-β-galactosidase activity and undergo chromatin remodeling resulting in heterochromatinisation. Senescence is established by the pRb and p53 tumour suppressor networks. Senescence has been detected in in vitro cellular settings and in premalignant, but not malignant lesions in mice and humans expressing mutant oncogenes. Despite oncogene-induced senescence, which is believed to be a cancer initiating barrier and other tumour suppressive mechanisms, benign cancers may still develop into malignancies by bypassing senescence. Here, we summarise the functional genetic screens that have identified genes, uncovered pathways and characterised mechanisms involved in senescence evasion. These include cell cycle regulators and tumour suppressor pathways, DNA damage response pathways, epigenetic regulators, SASP components and noncoding RNAs.

Exploring the Multifaceted Therapeutic Potential of Withaferin A and Its Derivatives

Withaferin A (WA), a manifold studied, C28-steroidal lactone withanolide found in Withania somnifera. Given its unique beneficial effects, it has gathered attention in the era of modern science. Cancer, being considered a "hopeless case and the leading cause of death worldwide, and the available conventional therapies have many lacunae in the form of side effects. The poly pharmaceutical natural compound, WA treatment, displayed attenuation of various cancer hallmarks by altering oxidative stress, promoting apoptosis, and autophagy, inhibiting cell proliferation, reducing angiogenesis, and metastasis progression. The cellular proteins associated with antitumor pathways were also discussed. WA structural modifications attack multiple signal transduction pathways and enhance the therapeutic outcomes in various diseases. Moreover, it has shown validated pharmacological effects against multiple neurodegenerative diseases by inhibiting acetylcholesterinases and butyrylcholinesterases enzyme activity, antidiabetic activity by upregulating adiponectin and preventing the phosphorylation of peroxisome proliferator-activated receptors (PPARγ), cardioprotective activity by AMP-activated protein kinase (AMPK) activation and suppressing mitochondrial apoptosis. The current review is an extensive survey of various WA associated disease targets, its pharmacokinetics, synergistic combination, modifications, and biological activities.

Exploring the multiple roles of guardian of the genome: P53

Background

Cells have evolved balanced mechanisms to protect themselves by initiating a specific response to a variety of stress. TheTP53gene, encoding P53 protein, is one of the many widely studied genes in human cells owing to its multifaceted functions and complex dynamics. The tumour-suppressing activity of P53 plays a principal role in the cellular response to stress. The majority of the human cancer cells exhibit the inactivation of the P53 pathway. In this review, we discuss the recent advancements in P53 research with particular focus on the role of P53 in DNA damage responses, apoptosis, autophagy, and cellular metabolism. We also discussed important P53-reactivation strategies that can play a crucial role in cancer therapy and the role of P53 in various diseases.

Main body

We used electronic databases like PubMed and Google Scholar for literature search. In response to a variety of cellular stress such as genotoxic stress, ischemic stress, oncogenic expression, P53 acts as a sensor, and suppresses tumour development by promoting cell death or permanent inhibition of cell proliferation. It controls several genes that play a role in the arrest of the cell cycle, cellular senescence, DNA repair system, and apoptosis. P53 plays a crucial role in supporting DNA repair by arresting the cell cycle to purchase time for the repair system to restore genome stability. Apoptosis is essential for maintaining tissue homeostasis and tumour suppression. P53 can induce apoptosis in a genetically unstable cell by interacting with many pro-apoptotic and anti-apoptotic factors.

Furthermore, P53 can activate autophagy, which also plays a role in tumour suppression. P53 also regulates many metabolic pathways of glucose, lipid, and amino acid metabolism. Thus under mild metabolic stress, P53 contributes to the cell’s ability to adapt to and survive the stress.

Conclusion

These multiple levels of regulation enable P53 to perform diversified roles in many cell responses. Understanding the complete function of P53 is still a work in progress because of the inherent complexity involved in between P53 and its target proteins. Further research is required to unravel the mystery of this Guardian of the genome “TP53”.

Prednisolone suppresses adriamycin-induced vascular smooth muscle cell senescence and inflammatory response via the SIRT1-AMPK signaling pathway

Cellular senescence is associated with inflammation and the senescence-associated secretory phenotype (SASP) of secreted proteins. Vascular smooth muscle cell (VSMC) expressing the SASP contributes to chronic vascular inflammation, loss of vascular function, and the developments of age-related diseases. Although VSMC senescence is well recognized, the mechanism of VSMC senescence and inflammation has not been established. In this study, we aimed to determine whether prednisolone (PD) attenuates adriamycin (ADR)-induced VSMC senescence and inflammation through the SIRT1-AMPK signaling pathway. We found that PD inhibited ADR-induced VSMC senescence and inflammation response by decreasing p-NF-κB expression through the SIRT1-AMPK signaling pathway. In addition, Western blotting revealed PD not only increased SIRT1 expression but also increased the phosphorylation of AMPK at Ser485 in ADR-treated VSMC. Furthermore, siRNA-mediated downregulation or pharmacological inhibitions of SIRT1 or AMPK significantly augmented ADR-induced inflammatory response and senescence in VSMC despite PD treatment. In contrast, the overexpression of SIRT1 or constitutively active AMPKα (CA-AMPKα) attenuated cellular senescence and p-NF-κB expression. Taken together, the inhibition of p-NF-κB by PD through the SIRT1 and p-AMPK (Ser485) pathway suppressed VSMC senescence and inflammation. Collectively, our results suggest that anti-aging effects of PD are caused by reduced VSMC senescence and inflammation due to reciprocal regulation of the SIRT1/p-AMPK (Ser485) signaling pathway.

Age-related dysfunction of p53-regulated phagocytic activity in macrophages

Aging promotes polarization of M2-like macrophages to M1-like macrophages and reduces their phagocytic ability. However, the molecular mechanisms underlying these aging-related changes remain poorly understood. Here, we demonstrate that p53 regulates phagocytic activity in macrophages from young mice but not in those from old ones. Macrophages from both old and young mice expressed functional p53 to induce target genes including p21 and Mdm2. In macrophages from young mice, chemically induced p53 decreased phagocytic activity and c-Myc levels, with the latter change reducing M2-related genes. However, in macrophages from old mice, phagocytic activity and c-Myc expression were independent of p53 activity. Furthermore, c-Myc suppression did not affect M2-related genes in old-mouse macrophages. These results demonstrate that dysregulation of p53 function is a molecular mechanism underlying reduced phagocytic activity in aged-mouse macrophages.

Cellular Senescence and Anti-Cancer Therapy

BACKGROUND

Cellular senescence is generally understood as a permanent cell cycle arrest stemming from different causes. The mechanism of cellular senescence-induced cell cycle arrest is complex, involving interactions between telomere shortening, inflammations and cellular stresses. In recent years, a growing number of studies have revealed that cellular senescence could mediate the cancer progression of neighboring cells, but this idea is controversial and contradictory evidence argues that cellular senescence also contributes to tumor suppression.

OBJECTIVE

Given that the complicated role of senescence in various physiological and pathological scenarios, we try to clarify the precise contribution role of cellular senescence to tumor progression.

METHODS

Search for the information in a large array of relevant articles to support our opinion.

RESULTS

We discuss the relatively widespread occurrence of cellular senescence in cancer treatment and identify the positive and negative side of senescence contributed to tumor progression.

CONCLUSION

We argue that the availability of pro-senescence therapy could represent as a promising regimen for managing cancer disease, particularly with regard to the poor clinical outcome obtained with other anticancer therapies.

Delayed sleep-onset and biological age: late sleep-onset is associated with shorter telomere length

STUDY OBJECTIVES

We evaluated the relationship between leukocyte telomere length (LTL) and sleep duration, insomnia symptoms, and circadian rhythm, to test whether sleep and chronobiological dysregulations are associated with cellular aging.

METHODS

Data from the Netherlands Study of Depression and Anxiety (N = 2,936) were used at two waves 6 years apart, to measure LTL. Telomeres shorten during the life span and are important biomarkers for cellular aging. LTL was assessed by qualitative polymerase chain reaction and converted into base pair number. Sleep parameters were: sleep duration and insomnia symptoms from the Insomnia Rating Scale. Circadian rhythm variables were: indication of Delayed Sleep Phase Syndrome (DSPS), mid-sleep corrected for sleep debt on free days (MSFsc), sleep-onset time, and self-reported chronotype, from the Munich Chronotype Questionnaire. Generalized estimating equations analyzed the associations between LTL, sleep, and chronobiological factors, adjusted for baseline age, sex, North European ancestry, and additionally for current smoking, depression severity, obesity, and childhood trauma.

RESULTS

Indicators of delayed circadian rhythm showed a strong and consistent effect on LTL, after adjustment for sociodemographic and health indicators. Late MSFsc (B = -49.9, p = .004), late sleep-onset time (B = -32.4, p = .001), indication of DSPS (B = -73.8, p = .036), and moderately late chronotype in adulthood (B = -71.6, p = .003) were associated with significantly shorter LTL across both waves; whereas sleep duration and insomnia symptoms were not. Extremely early chronotype showed significantly less LTL shortening than intermediate chronotype (B = 161.40, p = .037). No predictors showed accelerated LTL attrition over 6 years.

CONCLUSIONS

Individuals with delayed circadian rhythm have significantly shorter LTL, but not faster LTL attrition rates.

Catastrophic Endgames: Emerging Mechanisms of Telomere-Driven Genomic Instability

When cells progress to malignancy, they must overcome a final telomere-mediated proliferative lifespan barrier called replicative crisis. Crisis is characterized by extensive telomere fusion that drives widespread genomic instability, mitotic arrest, hyperactivation of autophagy, and cell death. Recently, it has become apparent that that the resolution of dicentric chromosomes, which arise from telomere fusions during crisis, can initiate a sequence of events that leads to chromothripsis, a form of extreme genomic catastrophe. Chromothripsis is characterized by localized genomic regions containing tens to thousands of rearrangements and it is becoming increasingly apparent that chromothripsis occurs widely across tumor types and has a clinical impact. Here we discuss how telomere dysfunction can initiate genomic complexity and the emerging mechanisms of chromothripsis.

Insertion of Telomeric Repeats in the Human and Horse Genomes: An Evolutionary Perspective

Interstitial telomeric sequences (ITSs) are short stretches of telomeric-like repeats (TTAGGG)n at nonterminal chromosomal sites. We previously demonstrated that, in the genomes of primates and rodents, ITSs were inserted during the repair of DNA double-strand breaks. These conclusions were derived from sequence comparisons of ITS-containing loci and ITS-less orthologous loci in different species. To our knowledge, insertion polymorphism of ITSs, i.e., the presence of an ITS-containing allele and an ITS-less allele in the same species, has not been described. In this work, we carried out a genome-wide analysis of 2504 human genomic sequences retrieved from the 1000 Genomes Project and a PCR-based analysis of 209 human DNA samples. In spite of the large number of individual genomes analyzed we did not find any evidence of insertion polymorphism in the human population. On the contrary, the analysis of ITS loci in the genome of a single horse individual, the reference genome, allowed us to identify five heterozygous ITS loci, suggesting that insertion polymorphism of ITSs is an important source of genetic variability in this species. Finally, following a comparative sequence analysis of horse ITSs and of their orthologous empty loci in other Perissodactyla, we propose models for the mechanism of ITS insertion during the evolution of this order.

Cellular Senescence: The Trojan Horse in Chronic Lung Diseases

Senescence is a cell fate decision characterized by irreversible arrest of proliferation accompanied by a senescence-associated secretory phenotype. Traditionally, cellular senescence has been recognized as a beneficial physiological mechanism during development and wound healing and in tumor suppression. However, in recent years, evidence of negative consequences of cellular senescence has emerged, illuminating its role in several chronic pathologies. In this context, senescent cells persist or accumulate and have detrimental consequences. In this review, we discuss the possibility that in chronic obstructive pulmonary disease, persistent senescence impairs wound healing in the lung caused by secretion of proinflammatory senescence-associated secretory phenotype factors and exhaustion of progenitor cells. In contrast, in idiopathic pulmonary fibrosis, chronic senescence in alveolar epithelial cells exacerbates the accumulation of senescent fibroblasts together with production of extracellular matrix. We review how cellular senescence may contribute to lung disease pathology.

The epigenetic regulation of centromeres and telomeres in plants and animals

The centromere is a chromosomal region where the kinetochore is formed, which is the attachment point of spindle fibers. Thus, it is responsible for the correct chromosome segregation during cell division. Telomeres protect chromosome ends against enzymatic degradation and fusions, and localize chromosomes in the cell nucleus. For this reason, centromeres and telomeres are parts of each linear chromosome that are necessary for their proper functioning. More and more research results show that the identity and functions of these chromosomal regions are epigenetically determined. Telomeres and centromeres are both usually described as highly condensed heterochromatin regions. However, the epigenetic nature of centromeres and telomeres is unique, as epigenetic modifications characteristic of both eu- and heterochromatin have been found in these areas. This specificity allows for the proper functioning of both regions, thereby affecting chromosome homeostasis. This review focuses on demonstrating the role of epigenetic mechanisms in the functioning of centromeres and telomeres in plants and animals.

Poly(ADP-ribose) polymerase enzymes and the maintenance of genome integrity

DNA damage response (DDR) relies on swift and accurate signaling to rapidly identify DNA lesions and initiate repair. A critical DDR signaling and regulatory molecule is the posttranslational modification poly(ADP-ribose) (PAR). PAR is synthesized by a family of structurally and functionally diverse proteins called poly(ADP-ribose) polymerases (PARPs). Although PARPs share a conserved catalytic domain, unique regulatory domains of individual family members endow PARPs with unique properties and cellular functions. Family members PARP-1, PARP-2, and PARP-3 (DDR-PARPs) are catalytically activated in the presence of damaged DNA and act as damage sensors. Family members tankyrase-1 and closely related tankyrase-2 possess SAM and ankyrin repeat domains that regulate their diverse cellular functions. Recent studies have shown that the tankyrases share some overlapping functions with the DDR-PARPs, and even perform novel functions that help preserve genomic integrity. In this review, we briefly touch on DDR-PARP functions, and focus on the emerging roles of tankyrases in genome maintenance. Preservation of genomic integrity thus appears to be a common function of several PARP family members, depicting PAR as a multifaceted guardian of the genome.

Induction of ROS and DNA damage-dependent senescence by icaritin contributes to its antitumor activity in hepatocellular carcinoma cells

Context: Icaritin (ICT), a prenylflavonoid derivative extracted from the Epimedium (Berberidaceae) genus, has been identified to exhibit antitumor effect in hepatocellular carcinoma (HCC) cells by inducing apoptosis. However, its effect on cellular senescence has not been elucidated. Objective: To investigate the mechanism for low concentrations of ICT exerting antitumor activity through induction of cellular senescence. Materials and methods: Human HepG2 and Huh7 cells were treated with low concentrations of ICT (1 and 2 μM) once per day for a week. Cellular senescence was evaluated through cell viability and senescence-associated-β-galactosidase activity. Cell cycle distribution and ROS levels were measured with flow cytometry. Gene expression was detected using qRT-PCR and western blotting. Fluorescent punctuates formation of γH2AX was analyzed by immunofluorescence. Results: ICT (1 and 2 μM) promoted cellular senescence in HepG2 and Huh7 cells, as observed by enlarged and flattened morphology and increased senescence-associated-β-galactosidase activity (∼7-8-fold and ∼11-12-fold of vehicle controls, respectively), accompanied by significant cell cycle arrest and decrease in DNA synthesis. Mechanistically, ICT-induced senescence occurred through accumulation of ROS (∼1.3-fold and ∼1.8-fold of vehicle controls in response to 1 and 2 μM ICT, respectively), which further resulted in DNA damage response, as evidenced by strong induction of γH2AX through immunofluorescence and western blotting assays. Pharmacological inhibition of ROS production with N-acetylcysteine attenuated ICT-induced γH2AX and senescence-associated-β-galactosidase activity (∼0.28-0.30-fold decrease, p < 0.05). Discussion and conclusions: Induction of cellular senescence by ICT defines a novel anticancer mechanism of ICT and provides a rationale for generalizing the study design to a broader study population to further developing ICT as a novel therapeutic agent for treatment of HCC.

Mice with hyper-long telomeres show less metabolic aging and longer lifespans

Short telomeres trigger age-related pathologies and shorter lifespans in mice and humans. In the past, we generated mouse embryonic (ES) cells with longer telomeres than normal (hyper-long telomeres) in the absence of genetic manipulations, which contributed to all mouse tissues. To address whether hyper-long telomeres have deleterious effects, we generated mice in which 100% of their cells are derived from hyper-long telomere ES cells. We observe that these mice have longer telomeres and less DNA damage with aging. Hyper-long telomere mice are lean and show low cholesterol and LDL levels, as well as improved glucose and insulin tolerance. Hyper-long telomere mice also have less incidence of cancer and an increased longevity. These findings demonstrate that longer telomeres than normal in a given species are not deleterious but instead, show beneficial effects.