Cellular senescence and tumor promotion: Is aging the key?

MEG8 as an antagonistic pleiotropic mechanism in breast cancer

Cellular senescence connects aging and cancer. Cellular senescence is a common program activated by cells in response to various types of stress. During this process, cells lose their proliferative capacity and undergo distinct morphological and metabolic changes. Senescence itself constitutes a tumor suppression mechanism and plays a significant role in organismal aging by promoting chronic inflammation. Additionally, age is one of the major risk factors for developing breast cancer. Therefore, while senescence can suppress tumor development early in life, it can also lead to an aging process that drives the development of age-related pathologies, suggesting an antagonistic pleiotropic effect. In this work, we identified Rian/MEG8 as a potential biomarker connecting aging and breast cancer for the first time. We found that Rian/MEG8 expression decreases with age; however, it is high in mice that age prematurely. We also observed decreased MEG8 expression in breast tumors compared to normal tissue. Furthermore, MEG8 overexpression reduced the proliferative and stemness properties of breast cancer cells both in vitro and in vivo by activating apoptosis. MEG8 could exemplify the antagonistic pleiotropic theory, where senescence is beneficial early in life as a tumor suppression mechanism due to increased MEG8, resulting in fewer breast tumors at an early age. Conversely, this effect could be detrimental later in life due to aging and cancer, when MEG8 is reduced and loses its tumor-suppressive role.

Role of Nicotinamide in the Pathogenesis of Actinic Keratosis: Implications for NAD+/SIRT1 Pathway

Actinic keratosis (AK) is a precursor to invasive squamous cell carcinoma, making early diagnosis and treatment essential to prevent progression. Among available therapeutic options, nicotinamide (NAM) has shown potential in reducing AK progression. NAM is a precursor of nicotinamide adenine dinucleotide (NAD+), which activates sirtuin (SIRT)1, a protein with anti-cancer properties. Although the role of SIRT1 in AK is still debated, no data currently exist on the systemic modulation of this protein in AK. Therefore, this study aims to evaluate whether NAM, by increasing serum NAD+ levels, may promote SIRT1 activation in peripheral blood mononuclear cells (PBMCs) in AK patients. Thirty patients were enrolled and treated with NAM for 24 months. Hematological, biochemical, and skin condition assessments were conducted, alongside the measurement of SIRT1 and NAD+ levels. A decrease in basophils, monocytes, total cholesterol, and blood glucose levels was observed in the study group, along with a reduction in AK lesions. Notably, NAM treatment significantly enhanced serum NAD+ levels, and nuclear SIRT1 activity in PBMCs. In conclusion, NAM administration significantly reduced AK progression in a NAD+/SIRT1-dependent manner, supporting its role as a chemopreventive agent in AK management.

Mechanisms of Transsynaptic Degeneration in the Aging Brain

A prominent feature in many neurodegenerative diseases involves the spread of the pathology from the initial site of damage to anatomically and functionally connected regions of the central nervous system (CNS), referred to as transsynaptic degeneration (TSD). This review covers the possible mechanisms of both retrograde and anterograde TSD in various age-related neurodegenerative diseases, including synaptically and glial mediated changes contributing to TDS and their potential as therapeutic targets. This phenomenon is well documented in clinical and experimental studies spanning various neurodegenerative diseases and their respective models, with a significant emphasis on the visual pathway, to be explored herein. With the increase in the aging population and subsequent rise in age-related neurodegenerative diseases, it is crucial to understand the underlying mechanisms of.

8-Oxoguanine DNA glycosylase protects cells from senescence via the p53-p21 pathway

Cellular senescence is an important factor leading to pulmonary fibrosis. Deficiency of 8-oxoguanine DNA glycosylase (OGG1) in mice leads to alleviation of bleomycin (BLM)-induced mouse pulmonary fibrosis, and inhibition of the OGG1 enzyme reduces the epithelial mesenchymal transition (EMT) in lung cells. In the present study, we find decreased expression of OGG1 in aged mice and BLM-induced cell senescence. In addition, a decrease in OGG1 expression results in cell senescence, such as increases in the percentage of SA-β-gal-positive cells, and in the p21 and p-H2AX protein levels in response to BLM in lung cells. Furthermore, OGG1 promotes cell transformation in A549 cells in the presence of BLM. We also find that OGG1 siRNA impedes cell cycle progression and inhibits the levels of telomerase reverse transcriptase (TERT) and LaminB1 in BLM-treated lung cells. The increase in OGG1 expression results in the opposite phenomenon. The mRNA levels of senescence-associated secretory phenotype (SASP) components, including IL-1α, IL-1β, IL-6, IL-8, CXCL1/CXCL2, and MMP-3, in the absence of OGG1 are obviously increased in A549 cells treated with BLM. Interestingly, we demonstrate that OGG1 binds to p53 to inhibit the activation of p53 and that silencing of p53 reverses the inhibition of OGG1 on senescence in lung cells. Additionally, the augmented cell senescence is shown in vivo in OGG1-deficient mice. Overall, we provide direct evidence in vivo and in vitro that OGG1 plays an important role in protecting tissue cells against aging associated with the p53 pathway.

Immune Escape Strategies in Head and Neck Cancer: Evade, Resist, Inhibit, Recruit

Head and neck cancers (HNCs) arise from the mucosal lining of the aerodigestive tract and are often associated with alcohol use, tobacco use, and/or human papillomavirus (HPV) infection. Over 600,000 new cases of HNC are diagnosed each year, making it the sixth most common cancer worldwide. Historically, treatments have included surgery, radiation, and chemotherapy, and while these treatments are still the backbone of current therapy, several immunotherapies have recently been approved by the Food and Drug Administration (FDA) for use in HNC. The role of the immune system in tumorigenesis and cancer progression has been explored since the early 20th century, eventually coalescing into the current three-phase model of cancer immunoediting. During each of the three phases-elimination, equilibrium, and escape-cancer cells develop and utilize multiple strategies to either reach or remain in the final phase, escape, at which point the tumor is able to grow and metastasize with little to no detrimental interference from the immune system. In this review, we summarize the many strategies used by HNC to escape the immune system, which include ways to evade immune detection, resist immune cell attacks, inhibit immune cell functions, and recruit pro-tumor immune cells.

Senopathies-Diseases Associated with Cellular Senescence

Cellular senescence describes a stable cell cycle arrest state with a characteristic phenotype. Senescent cells accumulate in the human body during normal aging, limiting the lifespan and promoting aging-related, but also several non-related, pathologies. We propose to refer to all diseases whose pathogenesis or progression is associated with cellular senescence as "senopathies". Targeting senescent cells with senolytics or senomorphics is likely to mitigate these pathologies. Examples of senopathies include cardiovascular, metabolic, musculoskeletal, liver, kidney, and lung diseases and neurodegeneration. For all these pathologies, animal studies provide clear mechanistic evidence for a connection between senescent cell accumulation and disease progression. The major persisting challenge in developing novel senotherapies is the heterogeneity of senescence phenotypes, causing a lack of universal biomarkers and difficulties in discriminating senescent from non-senescent cells.

Senescence induces fundamental changes in the secretome of mesenchymal stromal cells (MSCs): implications for the therapeutic use of MSCs and their derivates

Mesenchymal stromal cells (MSCs) are a heterogeneous population containing multipotent adult stem cells with a multi-lineage differentiation capacity, which differentiated into mesodermal derivatives. MSCs are employed for therapeutic purposes and several investigations have demonstrated that the positive effects of MSC transplants are due to the capacity of MSCs to modulate tissue homeostasis and repair via the activity of their secretome. Indeed, the MSC-derived secretomes are now an alternative strategy to cell transplantation due to their anti-inflammatory, anti-apoptotic, and regenerative effects. The cellular senescence is a dynamic process that leads to permanent cell cycle arrest, loss of healthy cells' physiological functions and acquiring new activities, which are mainly accrued through the release of many factors, indicated as senescence-associated secretory phenotype (SASP). The senescence occurring in stem cells, such as those present in MSCs, may have detrimental effects on health since it can undermine tissue homeostasis and repair. The analysis of MSC secretome is important either for the MSC transplants and for the therapeutic use of secretome. Indeed, the secretome of MSCs, which is the main mechanism of their therapeutic activity, loses its beneficial functions and acquire negative pro-inflammatory and pro-aging activities when MSCs become senescent. When MSCs or their derivatives are planned to be used for therapeutic purposes, great attention must be paid to these changes. In this review, we analyzed changes occurring in MSC secretome following the switch from healthy to senescence status.

Radiation-induced pulmonary fibrosis: roles of therapy-induced senescence and microRNAs

PURPOSE

Progressive, irreversible radiation-induced pulmonary fibrosis (RIPF) is a clinically significant intermediate- to a late-occurring side effect of radiotherapy. Known mechanisms of RIPF include oxidative stress-induced activation of TGF-β with activation of SMAD signaling, TNF-α elaboration, and activation of the Angiotensin Converting Enzyme (ACE) mediated production of angiotensin II with resulting activation of profibrotic cytokine signaling and vasoconstriction. The pioneering work of John Moulder, to whom this paper is dedicated, and several of his colleagues demonstrated that inhibiting the conversion of ACE with drugs such as Captopril, Enalapril, and Losartan can ameliorate radiation fibrosis in various tissues. While this work led several groups to probe mechanism-based pharmacological mitigation of RIPF, in this article, we explore and discuss the roles of microRNAs (miRNA) and therapy-induced senescence (TIS) in the pathogenesis of and potential biomarkers for RIPF.

CONCLUSION

Our analysis of the published literature in the last decade on RIPF, miRNA, and TIS identifies TIS as a mechanism in the onset and progression of RIPF, which is regulated through several miRNAs. This work may lead to the discovery and development of the next generation of miRNA therapeutics and/or the repurposing of approved pharmaceutical agents and the development of early biomarker panels to predict RIPF.

Exosome-encapsulated ncRNAs: Emerging yin and yang of tumor hallmarks

Tumorigenesis is a multifaceted process, where multiple physiological traits serving as cancer’s distinctive characteristics are acquired. “Hallmarks of cancer” is a set of cognitive abilities acquired by human cells that are pivotal to their tumor-forming potential. With limited or no protein-coding ability, non-coding RNAs (ncRNAs) interact with their target molecules and yield significant regulatory effects on several cell cycle processes. They play a “yin” and “yang” role, thereby functioning both as oncogenic and tumor suppressor and considered important in the management of various types of cancer entities. ncRNAs serve as important post-transcriptional and translational regulators of not only unrestricted expansion and metastasis of tumor cells but also of various biological processes, such as genomic mutation, DNA damage, immune escape, and metabolic disorder. Dynamical attributes such as increased proliferative signaling, migration, invasion, and epithelial–mesenchymal transition are considered to be significant determinants of tumor malignancy, metastatic dissemination, and therapeutic resistance. Furthermore, these biological attributes engage tumor cells with immune cells within the tumor microenvironment to promote tumor formation. We elaborate the interaction of ncRNAs with various factors in order to regulate cancer intra/intercellular signaling in a specific tumor microenvironment, which facilitates the cancer cells in acquiring malignant hallmarks. Exosomes represent a means of intercellular communication and participate in the maintenance of the tumor hallmarks, adding depth to the intricate, multifactorial character of malignant neoplasia. To summarize, ncRNAs have a profound impact on tumors, affecting their microcirculation, invasiveness, altered metabolism, microenvironment, and the capacity to modify the host immunological environment. Though the significance of ncRNAs in crosstalk between the tumor and its microenvironment is being extensively explored, we intend to review the hallmarks in the light of exosome-derived non-coding RNAs and their impact on the tumor microenvironment.

Biological Mechanisms to Reduce Radioresistance and Increase the Efficacy of Radiotherapy: State of the Art

Cancer treatment with ionizing radiation (IR) is a well-established and effective clinical method to fight different types of tumors and is a palliative treatment to cure metastatic stages. Approximately half of all cancer patients undergo radiotherapy (RT) according to clinical protocols that employ two types of ionizing radiation: sparsely IR (i.e., X-rays) and densely IR (i.e., protons). Most cancer cells irradiated with therapeutic doses exhibit radio-induced cytotoxicity in terms of cell proliferation arrest and cell death by apoptosis. Nevertheless, despite the more tailored advances in RT protocols in the last few years, several tumors show a relatively high percentage of RT failure and tumor relapse due to their radioresistance. To counteract this extremely complex phenomenon and improve clinical protocols, several factors associated with radioresistance, of both a molecular and cellular nature, must be considered. Tumor genetics/epigenetics, tumor microenvironment, tumor metabolism, and the presence of non-malignant cells (i.e., fibroblast-associated cancer cells, macrophage-associated cancer cells, tumor-infiltrating lymphocytes, endothelial cells, cancer stem cells) are the main factors important in determining the tumor response to IR. Here, we attempt to provide an overview of how such factors can be taken advantage of in clinical strategies targeting radioresistant tumors.

Expression of SASP, DNA Damage Response, and Cell Proliferation Factors in Early Gastric Neoplastic Lesions: Correlations and Clinical Significance

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-mediated senescence-associated secretory phenotype (SASP) pathway has recently been identified in the suppression and promotion of cancers. However, its practical role in carcinogenesis remains to be comprehensively elucidated. Here, we describe an investigation analysing SASP activity and its correlations with DNA damage response (DDR), genomic mutations, and cell proliferation in gastric carcinogenesis among 30 cases with available endoscopic submucosal dissection (ESD) specimens of early neoplastic lesions (including low-grade dysplasia [LGD], high-grade dysplasia [HGD], and intramucosal carcinoma). The positive cells of senescence-associated β-galactosidase staining and cGAS, STING, interferon-regulatory factor 3 (IRF3), and signal transducer and activator of transcription 6 (STAT6) expression levels using immunostaining were elevated in HGD and in cancers. Similarly, increased expression of the Fanconi anemia group D2 (FANCD2) protein, tumour suppressor p53 binding protein 1 (TP53BP1), and replication protein A (RPA2) (i.e., primary DDR factors) was detected in HGD and in cancers; these increased expression levels were closely correlated with high expression of Ki67 and minichromosome maintenance complex component 7 (MCM7) proteins. Moreover, genomic mutations in TP53 gene were detected in 56.67% of the evaluated cases (17/30) using next-generation sequencing, and positive staining was verified in HGD and in cancers. Statistical analysis revealed that cell proliferation closely correlated with the expression of DDR factors, of which TP53BP1 was positively associated with SASP factors and IRF3 was positively correlated with cell proliferation. In addition, an analysis evaluating clinical features demonstrated that STAT6-positive cases showed a longer progression-free survival time than STAT6-negative cases. Our evaluation, conducted using a limited number of specimens, suggests SASP may be prevalent in early gastric neoplastic lesions and could be activated by accelerated cell proliferation-induced DDR. The clinical significance of SASP still needs to be determined.

Construction, Validation, and Visualization of Two Web-Based Nomograms for Predicting Overall Survival and Cancer-Specific Survival in Elderly Patients with Primary Osseous Spinal Neoplasms

Background

Primary osseous spinal neoplasms (POSNs) are the rarest tumor type in the spine. Very few studies have presented data on elderly patients with POSNs specifically. The present study was aimed at exploring the prognostic factors and developing two web-based nomograms to predict overall survival (OS) and cancer-specific survival (CSS) for this population.

Method

The data of elderly patients with POSNs was extracted from the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2015. Cox regression analyses were performed to determine independent prognostic factors for OS and CSS, these prognostic factors were incorporated to establish nomograms. The discrimination of the nomograms was evaluated by the receiver operating characteristic (ROC) curve and the value of area under the curve (AUC). Calibration curve was plotted to assess the predictive accuracy of model. Decision curve analysis (DCA) was conducted to determine the net clinical benefit. Furthermore, two web-based survival rate calculators were developed.

Result

A total of 430 patients were finally selected into this study and were randomly assigned to the training set (302 cases) and validation set (128 cases). Of these, 289 patients were further considered for the analysis of CSS and were randomized into training set (205 cases) and validation set (84 cases). Based on the results of univariate and multivariate Cox analyses, variables that significantly correlated with survival outcomes were used to establish nomograms for OS and CSS prediction. Two established nomograms demonstrated good predictive performance. In the training set, the AUCs of the nomogram for predicting 12-, 24-, and 36-month OS were 0.849, 0.903, and 0.889, respectively, and those for predicting 12-, 24-, and 36-month CSS were 0.890, 0.880, and 0.881, respectively. Two web-based survival rate calculators were developed to estimate OS (https://research1.shinyapps.io/DynNomappOS/) and CSS (https://research1.shinyapps.io/DynNomappCSS/).

Conclusion

Novel nomograms based on identified clinicopathological factors were developed and can be used as a tool for clinicians to predict OS and CSS in elderly patients with POSNs. These models could help facilitate a personalized survival evaluation for this population.

Inflammatory Mediators in Oral Cancer: Pathogenic Mechanisms and Diagnostic Potential

Approximately 15% of cancers are attributable to the inflammatory process, and growing evidence supports an association between oral squamous cell carcinoma (OSCC) and chronic inflammation. Different oral inflammatory conditions, such as oral lichen planus (OLP), submucous fibrosis, and oral discoid lupus, are all predisposing for the development of OSCC. The microenvironment of these conditions contains various transcription factors and inflammatory mediators with the ability to induce proliferation, epithelial-to-mesenchymal transition (EMT), and invasion of genetically predisposed lesions, thereby promoting tumor development. In this review, we will focus on the main inflammatory molecules and transcription factors activated in OSCC, with emphasis on their translational potential.

Senescent Cells in Cancer: Wanted or Unwanted Citizens

Over recent decades, the field of cellular senescence has attracted considerable attention due to its association with aging, the development of age-related diseases and cancer. Senescent cells are unable to proliferate, as the pathways responsible for initiating the cell cycle are irreversibly inhibited. Nevertheless, senescent cells accumulate in tissues and develop a pro-inflammatory secretome, known as the senescence-associated secretory phenotype (SASP), which can have serious deleterious effects if not properly regulated. There is increasing evidence suggesting senescent cells contribute to different stages of carcinogenesis in different anatomical sites, mainly due to the paracrine effects of the SASP. Thus, a new therapeutic field, known as senotherapeutics, has developed. In this review, we aim to discuss the molecular mechanisms underlying the senescence response and its relationship with cancer development, focusing on the link between senescence-related inflammation and cancer. We will also discuss different approaches to target senescent cells that might be of use for cancer treatment.

Corrigendum: The Paradoxical Role of Cellular Senescence in Cancer

[This corrects the article DOI: 10.3389/fcell.2021.722205.].

IL-1/IL-1R Signaling in Head and Neck Cancer

Decades ago, the study of cancer biology was mainly focused on the tumor itself, paying little attention to the tumor microenvironment (TME). Currently, it is well recognized that the TME plays a vital role in cancer development and progression, with emerging treatment strategies focusing on different components of the TME, including tumoral cells, blood vessels, fibroblasts, senescent cells, inflammatory cells, inflammatory factors, among others. There is a well-accepted relationship between chronic inflammation and cancer development. Interleukin-1 (IL-1), a potent pro-inflammatory cytokine commonly found at tumor sites, is considered one of the most important inflammatory factors in cancer, and has been related with carcinogenesis, tumor growth and metastasis. Increasing evidence has linked development of head and neck squamous cell carcinoma (HNSCC) with chronic inflammation, and particularly, with IL-1 signaling. This review focuses on the most important members of the IL-1 family, with emphasis on how their aberrant expression can promote HNSCC development and metastasis, highlighting possible clinical applications.

The Ageing Brain: Molecular and Cellular Basis of Neurodegeneration

Ageing is an inevitable event in the lifecycle of all organisms, characterized by progressive physiological deterioration and increased vulnerability to death. Ageing has also been described as the primary risk factor of most neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and frontotemporal lobar dementia (FTD). These neurodegenerative diseases occur more prevalently in the aged populations. Few effective treatments have been identified to treat these epidemic neurological crises. Neurodegenerative diseases are associated with enormous socioeconomic and personal costs. Here, the pathogenesis of AD, PD, and other neurodegenerative diseases has been presented, including a summary of their known associations with the biological hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, mitochondrial dysfunction, cellular senescence, deregulated nutrient sensing, stem cell exhaustion, and altered intercellular communications. Understanding the central biological mechanisms that underlie ageing is important for identifying novel therapeutic targets for neurodegenerative diseases. Potential therapeutic strategies, including the use of NAD+ precursors, mitophagy inducers, and inhibitors of cellular senescence, has also been discussed.

The Paradoxical Role of Cellular Senescence in Cancer

Cellular senescence occurs in proliferating cells as a consequence of various triggers including telomere shortening, DNA damage, and inappropriate expression of oncogenes. The senescent state is accompanied by failure to reenter the cell cycle under mitotic stimulation, resistance to cell death and enhanced secretory phenotype. A growing number of studies have convincingly demonstrated a paradoxical role for spontaneous senescence and therapy-induced senescence (TIS), that senescence may involve both cancer prevention and cancer aggressiveness. Cellular senescence was initially described as a physiological suppressor mechanism of tumor cells, because cancer development requires cell proliferation. However, there is growing evidence that senescent cells may contribute to oncogenesis, partly in a senescence-associated secretory phenotype (SASP)-dependent manner. On the one hand, SASP prevents cell division and promotes immune clearance of damaged cells, thereby avoiding tumor development. On the other hand, SASP contributes to tumor progression and relapse through creating an immunosuppressive environment. In this review, we performed a review to summarize both bright and dark sides of senescence in cancer, and the strategies to handle senescence in cancer therapy were also discussed.

mTOR Activity and Autophagy in Senescent Cells, a Complex Partnership

Cellular senescence is a form of proliferative arrest triggered in response to a wide variety of stimuli and characterized by unique changes in cell morphology and function. Although unable to divide, senescent cells remain metabolically active and acquire the ability to produce and secrete bioactive molecules, some of which have recognized pro-inflammatory and/or pro-tumorigenic actions. As expected, this “senescence-associated secretory phenotype (SASP)” accounts for most of the non-cell-autonomous effects of senescent cells, which can be beneficial or detrimental for tissue homeostasis, depending on the context. It is now evident that many features linked to cellular senescence, including the SASP, reflect complex changes in the activities of mTOR and other metabolic pathways. Indeed, the available evidence indicates that mTOR-dependent signaling is required for the maintenance or implementation of different aspects of cellular senescence. Thus, depending on the cell type and biological context, inhibiting mTOR in cells undergoing senescence can reverse senescence, induce quiescence or cell death, or exacerbate some features of senescent cells while inhibiting others. Interestingly, autophagy—a highly regulated catabolic process—is also commonly upregulated in senescent cells. As mTOR activation leads to repression of autophagy in non-senescent cells (mTOR as an upstream regulator of autophagy), the upregulation of autophagy observed in senescent cells must take place in an mTOR-independent manner. Notably, there is evidence that autophagy provides free amino acids that feed the mTOR complex 1 (mTORC1), which in turn is required to initiate the synthesis of SASP components. Therefore, mTOR activation can follow the induction of autophagy in senescent cells (mTOR as a downstream effector of autophagy). These functional connections suggest the existence of autophagy regulatory pathways in senescent cells that differ from those activated in non-senescence contexts. We envision that untangling these functional connections will be key for the generation of combinatorial anti-cancer therapies involving pro-senescence drugs, mTOR inhibitors, and/or autophagy inhibitors.

Cellular Senescence: Pathogenic Mechanisms in Lung Fibrosis

Pulmonary fibrosis is a chronic and fatal lung disease that significantly impacts the aging population globally. To date, anti-fibrotic, immunosuppressive, and other adjunct therapy demonstrate limited efficacies. Advancing our understanding of the pathogenic mechanisms of lung fibrosis will provide a future path for the cure. Cellular senescence has gained substantial interest in recent decades due to the increased incidence of fibroproliferative lung diseases in the older age group. Furthermore, the pathologic state of cellular senescence that includes maladaptive tissue repair, decreased regeneration, and chronic inflammation resembles key features of progressive lung fibrosis. This review describes regulatory pathways of cellular senescence and discusses the current knowledge on the senescence of critical cellular players of lung fibrosis, including epithelial cells (alveolar type 2 cells, basal cells, etc.), fibroblasts, and immune cells, their phenotypic changes, and the cellular and molecular mechanisms by which these cells contribute to the pathogenesis of pulmonary fibrosis. A few challenges in the field include establishing appropriate in vivo experimental models and identifying senescence-targeted signaling molecules and specific therapies to target senescent cells, known collectively as "senolytic" or "senotherapeutic" agents.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

The role of icIL-1RA in keratinocyte senescence and development of the senescence-associated secretory phenotype

There is compelling evidence that senescent cells, through the senescence-associated secretory phenotype (SASP), can promote malignant transformation and invasion. Interleukin-1 (IL-1) is a key mediator of this cytokine network, but the control of its activity in the senescence programme has not been elucidated. IL-1 signalling is regulated by IL-1RA, which has four variants. Here, we show that expression of intracellular IL-1RA type 1 (icIL-1RA1), which competitively inhibits binding of IL-1 to its receptor, is progressively lost during oral carcinogenesis ex vivo and that the pattern of expression is associated with keratinocyte replicative fate in vitro We demonstrate that icIL-1RA1 is an important regulator of the SASP in mortal cells, as CRISPR/Cas9-mediated icIL-1RA1 knockdown in normal and mortal dysplastic oral keratinocytes is followed by increased IL-6 and IL-8 secretion, and rapid senescence following release from RhoA-activated kinase inhibition. Thus, we suggest that downregulation of icIL-1RA1 in early stages of the carcinogenesis process can enable the development of a premature and deregulated SASP, creating a pro-inflammatory state in which cancer is more likely to arise.

Peroxiredoxin1 Knockdown Inhibits Oral Carcinogenesis via Inducing Cell Senescence Dependent on Mitophagy

Purpose

Cellular senescence is a physiological phenomenon by which cells irreversibly lose their proliferative potential. It is not clear whether senescent cells are related to malignant transformation in oral precancerous lesions. The role of peroxiredoxin1 (Prx1)-induced cell senescence in OLK malignant transformation has not been reported. The aim of this study is to investigate the role and mechanism of cell senescence in oral carcinogenesis.

Methods

In this study, 4-nitro-quinoline-1-oxide (4NQO) induced tongue carcinogenesis model in Prx1^+/+ and Prx1^+/- mice and dysplastic oral keratinocyte (DOK) were used. Prx1 knockdown DOK cells were harvested with shRNA injection, and cell senescence was detected via the senescence-associated β-galactosidase (SA β-gal) assay. The senescence and mitophagy-related proteins were observed by immunohistochemistry (IHC), Western blot and qRT-PCR. The binding of Prx1 with prohibitin 2 (PHB2) and light chain 3 (LC3) was predicted via ZDOCK and measured in mice by Duolink analysis.

Results

Histologically, 4NQO treatment induced epithelial hyperplasia, dysplasia (mild, moderate and severe), carcinomas in situ and oral squamous cell carcinoma (OSCC) in mouse tongue mucosa. The malignant transformation rate in Prx1^+/- mice (37.5%) was significantly lower compared with Prx1^+/+ mice (57.1%). In Prx1^+/+ mice, a higher number of senescent cells and greater expression of p53 and p21 were observed in hyperplastic and dysplastic tongue tissues when compared with those in OSCC tissues. Prx1 knockdown induced a greater number of senescent cells in hyperplastic tissues, and DOK cells accompanied cell cycle arrest at the G1 phase and PHB2/LC3II downregulation. Prx1 was predicted to dock with PHB2 and LC3 via ZDOCK, and the interactions were confirmed by in situ Duolink analysis.

Conclusion

Prx1 silencing inhibits the oral carcinogenesis by inducing cell senescence dependent on mitophagy.

Targeting sphingosine kinase 1 (SK1) enhances oncogene-induced senescence through ceramide synthase 2 (CerS2)-mediated generation of very-long-chain ceramides

Senescence is an antiproliferative mechanism that can suppress tumor development and can be induced by oncogenes such as genes of the Ras family. Although studies have implicated bioactive sphingolipids (SL) in senescence, the specific mechanisms remain unclear. Here, using MCF10A mammary epithelial cells, we demonstrate that oncogenic K-Ras (Kirsten rat sarcoma viral oncogene homolog) is sufficient to induce cell transformation as well as cell senescence-as revealed by increases in the percentage of cells in the G1 phase of the cell cycle, p21WAF1/Cip1/CDKN1A (p21) expression, and senescence-associated β-galactosidase activity (SA-β-gal). Furthermore, oncogenic K-Ras altered SL metabolism, with an increase of long-chain (LC) C18, C20 ceramides (Cer), and very-long-chain (VLC) C22:1, C24 Cer, and an increase of sphingosine kinase 1 (SK1) expression. Since Cer and sphingosine-1-phosphate have been shown to exert opposite effects on cellular senescence, we hypothesized that targeting SK1 could enhance oncogenic K-Ras-induced senescence. Indeed, SK1 downregulation or inhibition enhanced p21 expression and SA-β-gal in cells expressing oncogenic K-Ras and impeded cell growth. Moreover, SK1 knockdown further increased LC and VLC Cer species (C18, C20, C22:1, C24, C24:1, C26:1), especially the ones increased by oncogenic K-Ras. Fumonisin B1 (FB1), an inhibitor of ceramide synthases (CerS), reduced p21 expression induced by oncogenic K-Ras both with and without SK1 knockdown. Functionally, FB1 reversed the growth defect induced by oncogenic K-Ras, confirming the importance of Cer generation in the senescent phenotype. More specifically, downregulation of CerS2 by siRNA blocked the increase of VLC Cer (C24, C24:1, and C26:1) induced by SK1 knockdown and phenocopied the effects of FB1 on p21 expression. Taken together, these data show that targeting SK1 is a potential therapeutic strategy in cancer, enhancing oncogene-induced senescence through an increase of VLC Cer downstream of CerS2.

Proteasome activator PA200 maintains stability of histone marks during transcription and aging

The epigenetic inheritance relies on stability of histone marks, but various diseases, including aging-related disorders, are usually associated with alterations of histone marks. Whether and how the proteasome is responsible for maintaining the histone marks during transcription and aging remain unclear. The core histones can be degraded by the atypical proteasome, which contains the proteasome activator PA200, in an acetylation-dependent manner during somatic DNA damage response and spermiogenesis. Methods: By utilizing a substitute of methionine to label proteins metabolically, we analyzed histone degradation genome-wide by sequencing the DNA fragments following pulse-chase assays. The genome-wide RNA-sequencing analysis was performed to analyze transcription and chromatin-immunoprecipitation (ChIP)-sequencing was used for analyses of histone marks. The experimental models included gene-manipulated cells (including both mouse and yeast), mouse liver, and mice. Results: Degradation of H4 or the transcription-coupled histone variant H3.3 could be suppressed by deletion of PA200 or its yeast ortholog Blm10. The histone deacetylase inhibitor accelerated the degradation rates of H3, while the mutations of the putative acetyl-lysine-binding region of PA200 abolished histone degradation in the G1-arrested cells. Deletion of PA200 dramatically altered deposition of the active transcriptional hallmarks (H3K4me3 and H3K56ac) and transcription, especially during cellular aging. Furthermore, deletion of PA200 or Blm10 accelerated cellular aging. Notably, the PA200-deficient mice displayed a range of aging-related deteriorations, including immune malfunction, anxiety-like behavior and shorter lifespan. Conclusion: PA200 promotes the transcription-coupled degradation of the core histones, and plays an important role in maintaining the stability of histone marks during transcription and aging.

IER2-induced senescence drives melanoma invasion through osteopontin

Expression of the immediate-early response gene IER2 has been associated with the progression of several types of cancer, but its functional role is poorly understood. We found that increased IER2 expression in human melanoma is associated with shorter overall survival, and subsequently investigated the mechanisms through which IER2 exerts this effect. In experimental melanoma models, sustained expression of IER2 induced senescence in a subset of melanoma cells in a p53/MAPK/AKT-dependent manner. The senescent cells produced a characteristic secretome that included high levels of the extracellular phosphoglycoprotein osteopontin. Nuclear localization of the IER2 protein was critical for both the induction of senescence and osteopontin secretion. Osteopontin secreted by IER2-expressing senescent cells strongly stimulated the migration and invasion of non-senescent melanoma cells. Consistently, we observed coordinate expression of IER2, p53/p21, and osteopontin in primary human melanomas and metastases, highlighting the pathophysiological relevance of IER2-mediated senescence in melanoma progression. Together, our study reveals that sustained IER2 expression drives melanoma invasion and progression through stimulating osteopontin secretion via the stochastic induction of senescence.

Repurposing drugs to fight aging: The difficult path from bench to bedside

The steady rise in life expectancy occurred across all developed countries during the last century. This demographic trend is, however, not accompanied by the same healthspan extension. This is since aging is the main risk factor for all age-associated pathological conditions. Therefore, slowing the rate of aging is suggested to be more efficient in preventing or delaying age-related diseases than treat them one by one, which is the common approach in a current pharmacological disease-oriented paradigm. To date, a variety of medications designed to treat particular pathological conditions have been shown to exhibit pro-longevity effects in different experimental models. Among them, there are many commonly used prescription and over-the-counter pharmaceuticals such as metformin, rapamycin, aspirin, statins, melatonin, vitamin antioxidants, etc. All of them are being increasingly investigated in preclinical and clinical trials with the aim of determine whether they have potential for extension of human healthspan. The results from these trials are frequently inconclusive and fall short of initial expectations, suggesting that innovative research ideas and additional translational steps are required to overcome obstacles for implementation of such approaches in clinical practice. In this review, recent advances and challenges in the field of repurposing widely used conventional pharmaceuticals to target the aging process are summarized and discussed.

Pattern-recognition-based Sensor Arrays for Cell Characterization: From Materials and Data Analyses to Biomedical Applications

To capture a broader scope of complex biological phenomena, alternatives to conventional sensing based on specificity for cell detection and characterization are needed. Pattern-recognition-based sensing is an analytical method designed to mimic mammalian sensory systems for analyte identification based on the pattern recognition of multivariate data, which are generated using an array of multiple probes that cross-reactively interact with analytes. This sensing approach is significantly different from conventional specific cell sensing based on highly specific probes, including antibodies against biomarkers. Encouraged by the advantages of this technique, such as the simplicity, rapidity, and tunability of the systems without requiring a priori knowledge of biomarkers, numerous sensor arrays have been developed over the past decade and used in a variety of cell sensing applications; these include disease diagnosis, drug discovery, and fundamental research. This review summarizes recent progress in pattern-recognition-based cell sensing, with a particular focus on guidelines for designing materials and arrays, techniques for analyzing response patterns, and applications of sensor systems that are focused primarily for the biomedical field.

N-Acetyltransferase 10 Promotes Micronuclei Formation to Activate the Senescence-Associated Secretory Phenotype Machinery in Colorectal Cancer Cells

The formation of micronuclei (MN) is prevalent in human cancer cells and its role in activating the senescence-associated secretory phenotype (SASP) machinery has been identified recently. However, the role of MN in regulation of SASP signaling still needs to define in practical cancers. Here, we reported that in colorectal cancer cells the expression of NAT10 (N-acetyltransferase 10) could mediate MN formation through DNA replication and NAT10-positive MN could activate SASP by binding to cGAS. The chemical inhibition of NAT10 by Remodelin or genomic depletion could markedly reduce MN formation, SASP activation, and senescence in colorectal cancer cells. Cell stress such as oxidative or hypoxia could upregulate NAT10 and its associated MN formation senescence and expression of SASP factors. Statistical analysis of clinical specimens revealed correlations between NAT10 expression, MN formation, SASP signaling, and the clinicopathological features of colorectal cancer. Our data suggest that NAT10 increasing MN formation and SASP pathway activation, promoting colorectal cancer progression.

Aging of the cells: Insight into cellular senescence and detection Methods

Cellular theory of aging states that human aging is the result of cellular aging, in which an increasing proportion of cells reach senescence. Senescence, from the Latin word senex, means "growing old," is an irreversible growth arrest which occurs in response to damaging stimuli, such as DNA damage, telomere shortening, telomere dysfunction and oncogenic stress leading to suppression of potentially dysfunctional, transformed, or aged cells. Cellular senescence is characterized by irreversible cell cycle arrest, flattened and enlarged morphology, resistance to apoptosis, alteration in gene expression and chromatin structure, expression of senescence associated- β-galactosidase (SA-β-gal) and acquisition of senescence associated secretory phenotype (SASP). In this review paper, different types of cellular senescence including replicative senescence (RS) which occurs due to telomere shortening and stress induced premature senescence (SIPS) which occurs in response to different types of stress in cells, are discussed. Biomarkers of cellular senescence and senescent assays including BrdU incorporation assay, senescence associated- β-galactosidase (SA-β-gal) and senescence-associated heterochromatin foci assays to detect senescent cells are also addressed.

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.

Role of Nicotinamide in Genomic Stability and Skin Cancer Chemoprevention

Nicotinamide (NAM) is an amide form of vitamin B3 and the precursor of nicotinamide adenine dinucleotide (NAD+), an essential co-enzyme of redox reactions for adenosine triphosphate (ATP) production and for other metabolic processes. As NAD+ status is critical in maintaining cellular energy, vitamin B3 deficiency mainly affects tissues that need high cellular energy causing pellagra and skin sun sensitivity. In animal models, NAD+ deficiency leads to UV sensitivity of the skin, impairs DNA damage response, and increases genomic instability and cancer incidence. Furthermore, NAD+ depletion is associated with human skin aging and cancer. NAM prevents the UV-induced ATP depletion boosting cellular energy and enhances DNA repair activity in vitro and in vivo. Moreover, NAM reduces skin cancer incidence and prevents the immune-suppressive effects of UV in mice. Thus, NAM is involved in the maintenance of genomic stability and may have beneficial effects against skin aging changes and tumor development. Clinical studies showed that topical use of NAM reduces cutaneous aging. Furthermore, oral NAM administration reduces the level of UV-mediated immunosuppression and lowers the rate of non-melanoma skin cancers in high-risk patients. Therefore, NAM replenishment strategy may be a promising approach for skin cancer chemoprevention.

Nuclear receptor HNF4α performs a tumor suppressor function in prostate cancer via its induction of p21-driven cellular senescence

Hepatocyte nuclear factor 4α (HNF4α, NR2A1) is a highly conserved member of the nuclear receptor superfamily. Recent advances reveal that it is a key transcriptional regulator of genes, broadly involved in xenobiotic and drug metabolism and also cancers of gastrointestinal tract. However, the exact functional roles of HNF4α in prostate cancer progression are still not fully understood. In this study, we determined the functional significance of HNF4α in prostate cancer. Our results showed that HNF4α exhibited a reduced expression pattern in clinical prostate cancer tissues, prostate cancer cell lines and xenograft model of castration-relapse prostate cancer. Stable HNF4α knockdown not only could promote cell proliferation and suppress doxorubicin (Dox)-induced cellular senescence in prostate cancer cells, but also confer resistance to paclitaxel treatment and enhance colony formation capacity and in vivo tumorigenicity of prostate cancer cells. On the contrary, ectopic overexpression of HNF4α could significantly inhibit the cell proliferation of prostate cancer cells, induce cell-cycle arrest at G₂/M phase and trigger the cellular senescence in prostate cancer cells by activation of p21 signal pathway in a p53-independent manner via its direct transactivation of CDKN1A. Together, our results show that HNF4α performs a tumor suppressor function in prostate cancer via a mechanism of p21-driven cellular senescence.

Senescence-induced immunophenotype, gene expression and electrophysiology changes in human amniocytes

The aim of the study was to evidence replicative senescence‐induced changes in human amniocytes via flow cytometry, quantitative reverse‐transcription‐polymerase chain reaction (qRT‐PCR) and automated/manual patch‐clamp. Both cryopreserved and senescent amniocytes cultured in BIO‐AMF‐2 medium featured high percentages of pluripotency cell surface antigens SSEA‐1, SSEA‐4, TRA1‐60, TRA1‐81 (assessed by flow cytometry) and expression of pluripotency markers Oct4 (Pou5f1) and Nanog (by qRT‐PCR). We demonstrated in senescent vs cryopreserved amniocytes decreases in mesenchymal stem cell surface markers. Senescence‐associated β‐galactosidase stained only senescent amniocytes, and they showed no deoxyuridine incorporation. The gene expression profile revealed a secretory phenotype of senescent amniocytes (increased interleukin (IL)‐1α, IL‐6, IL‐8, transforming growth factor β, nuclear factor κB p65 expression), increases for cell cycle‐regulating genes (p16^INK4A), cytoskeletal elements (β‐actin); HMGB1, c‐Myc, Bcl‐2 showed reduced changes and p21, MDM2 decreased. Via patch‐clamp we identified five ion current components: outward rectifier K⁺ current, an inactivatable component, big conductance Ca²⁺‐dependent K⁺ channels (BK) current fluctuations, Na⁺ current, and inward rectifier K⁺ current. Iberiotoxin 100 nmol/L blocked 71% of BK fluctuations, and lidocaine 200 μmol/L exerted use‐dependent Na⁺ current block. Transient receptor potential (TRP)M7‐like current density at −120 mV was significantly increased in senescent amniocytes. The proinflammatory profile acquired by senescent amniocytes in vitro may prevent their use in clinical therapies for immunosuppression, antiapoptotic and healing effects.

Placental Ageing in Adverse Pregnancy Outcomes: Telomere Shortening, Cell Senescence, and Mitochondrial Dysfunction

Preeclampsia is a multisystemic pregnancy disorder and a major cause of maternal and neonatal morbidity and mortality worldwide. The exact pathophysiology of preeclampsia remains unclear; however, it is speculated that the various pathologies can be attributed to impaired vascular remodelling and elevated oxidative stress within the placenta. Oxidative stress plays a key role in cell ageing, and the persistent presence of elevated oxidative stress precipitates cellular senescence and mitochondrial dysfunction, resulting in premature ageing of the placenta. Premature ageing of the placenta is associated with placental insufficiency, which reduces the functional capacity of this critical organ and leads to abnormal pregnancy outcomes. The changes brought about by oxidative insults are irreversible and often lead to deleterious modifications in macromolecules such as lipids and proteins, DNA mutations, and alteration of mitochondrial functioning and dynamics. In this review, we have summarized the current knowledge of placental ageing in the aetiology of adverse pregnancy outcomes and discussed the hallmarks of ageing which could be potential markers for preeclampsia and fetal growth restriction.

AURKB as a target in non-small cell lung cancer with acquired resistance to anti-EGFR therapy

Non-small cell lung cancer (NSCLC) tumors harboring mutations in EGFR ultimately relapse to therapy with EGFR tyrosine kinase inhibitors (EGFR TKIs). Here, we show that resistant cells without the p.T790M or other acquired mutations are sensitive to the Aurora B (AURKB) inhibitors barasertib and S49076. Phospho-histone H3 (pH3), a major product of AURKB, is increased in most resistant cells and treatment with AURKB inhibitors reduces the levels of pH3, triggering G1/S arrest and polyploidy. Senescence is subsequently induced in cells with acquired mutations while, in their absence, polyploidy is followed by cell death. Finally, in NSCLC patients, pH3 levels are increased after progression on EGFR TKIs and high pH3 baseline correlates with shorter survival. Our results reveal that AURKB activation is associated with acquired resistance to EGFR TKIs, and that AURKB constitutes a potential target in NSCLC progressing to anti-EGFR therapy and not carrying resistance mutations.

Non-small cell lung cancer with EGFR mutations are known to develop resistance to EGFR tyrosine kinase inhibitors. Here, the authors show AURKB activation to be associated with resistance in EGFR mutant lung cancer cells, and that AURKB is a therapeutic target in resistant tumours that lack the p.T790M or other acquired mutations.

Olaparib induced senescence under P16 or P53 dependent manner in ovarian cancer

Objective

Poly (ADP-ribose) polymerase (PARP) is an important molecule in the early stress response of DNA damage, which is involved in DNA damage repair and cellular senescence. Olaparib, as PARP inhibitor, has an anti-tumor effect on high grade serous ovarian cancer, but its effects on cellular senescence have not been reported. This study intends to explore the role of olaparib in the regulation of senescence in ovarian cancer cells.

Methods

The effects of olaparib on the senescence of ovarian cancer cells were detected by using the senescence-associated β-galactosidase (SA-β-Gal) and senescence-associated heterochromatin aggregation (SAHF). Quantitative real-time polymerase chain reaction was used to analyze the senescence-associated secretory phenotype (SASP). Cell cycle and apoptosis were detected by flow cytometry. The effect of olaparib on tumor growth was analyzed in a nude mouse xenograft transplantation model.

Results

Long-term (6 days) treatment with olaparib (5 μM) significantly inhibited the growth of ovarian cancer cells, leading to arrest the cell cycle at G0/G1 phase, significant increase the number of positive SA-β-Gal stained cells and positive SAHF cells. The expression of P16 and retinoblastoma protein (p-RB) were significantly enhanced in SKOV3 cells under olaparib treated, meanwhile, the expression of P53 and p-RB were upregulated in A2780 cells. In OVCAR-3 cells, the expression of P53 was downregulated and p-RB was upregulated. Mice with SKOV3 xenograft transplantation was given olaparib (10 mg/kg/day) via abdominal cavity administration, the tumor volume was reduced (p<0.01).

Conclusion

Continuous low dosage administration of olaparib induced senescence under P16 or P53 dependent manner in ovarian cancer.

Senolytic Cocktail Dasatinib+Quercetin (D+Q) Does Not Enhance the Efficacy of Senescence-Inducing Chemotherapy in Liver Cancer

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death, which develops in the context of fibrosis and cirrhosis caused by chronic inflammation, in turn due to non-alcoholic fatty liver disease (NAFLD), alcohol consumption and/or hepatitis viral infection. An increased number of senescent cells are associated with age-related tissue degeneration during NAFLD-induced HCC, or during chemotherapeutic treatment. Senolytic agents target selectively senescent cells. A combination of the senolytic drugs dasatinib and quercetin (D+Q) reduced hepatic lipid accumulation and alleviated age-associated physical dysfunction in mice. However, whether D+Q can impact the treatment of HCC, at the end-stage of the NAFLD inflammatory spectrum, is unknown. Here, using two well-established HCC cell lines (HepG2, Huh-7), we demonstrate that the maximal cytostatic doses for D and/or Q (1 + 1 μM) lacked efficacy in removing doxorubicin-induced β-gal-positive senescent cells. Moreover, D+Q did not affect doxorubicin-dependent induction of flattened morphology, activation of p16, expression of SASP-associated genes or formation of γH2AX foci. We then investigated the antitumor efficacy of doxorubicin, D+Q, or the combination, in xenograft studies conducted with HCC cells inoculated in athymic nude mice. Doxorubicin reduced tumor growth by 30% compared to control mice, while D+Q was ineffective in synergizing with doxorubicin and in clearing doxorubicin-induced HCC senescent cells. Unexpectedly, D+Q alone appeared to have acute pro-tumorigenic effects in control mice. While our data need to be confirmed in animal models that fully recapitulate NAFLD, we demonstrate that these compounds are ineffective, alone or in synergy with senescence-inducing chemotherapy, against experimental HCC.

Staurosporine Induces the Generation of Polyploid Giant Cancer Cells in Non-Small-Cell Lung Carcinoma A549 Cells

Cultivation of A549 non-small-cell lung carcinoma (NSCLC) cells in the presence of staurosporine (SSP) leads to a reduction or a lack of proliferation in a concentration-dependent manner. This inhibition of proliferation is accompanied by the generation of polyploid giant cancer cells (PGCCs) that are characterized by cell flattening, increased cell size, polyploidy, and polynucleation as determined by crystal violet staining, BrdU and DiI labelling, and flow cytometry as well as video time-lapse analysis. Continuous SSP treatment of A549 cells can preserve PGCCs for at least two months in a resting state. Upon removal of SSP, A549 PGCCs restart to divide and exhibit a proliferation pattern and cellular morphology indistinguishable from cells where PGCCs originally derived from. Thus, SSP-treated A549 cells represent a simple and reliable experimental model for the reversible generation of PGCCs and their subsequent experimental analysis.

High COX-2 expression contributes to a poor prognosis through the inhibition of chemotherapy-induced senescence in nasopharyngeal carcinoma

Resistance to radiotherapy and chemotherapy currently represents one of the major reasons for therapeutic failure in nasopharyngeal carcinoma (NPC). However, the mechanisms underlying resistance to chemotherapy in NPC remain unclear. In this study, cell counting assay, cell cycle assay and senescence associated β-galactosidase activity were performed to evaluate cell growth, proliferation and senescence, respectively. We found that the aberrant expression of cyclooxygenase-2 (COX-2) was associated with a poor outcome and recurrance in patients with NPC. In NPC cells, COX-2 overexpression increased cell proliferation, inhibited cellular senescence and resulted in chemoresistance, while the knockdown of COX-2 reduced cell proliferation, promoted cellular senescence and overcame chemoresistance. Furthermore, fibroblasts from COX-2 knockout mice exhibited cellular senescence, particularly when treated with chemotherapeutic agents. Mechanistically, COX-2 interacted with p53 protein and inhibited cellular senescence, which resulted in chemotherapeutic resistance. On the whole, these findings indicate that COX-2 may play a critical role in chemotherapeutic resistance in NPC via the inhibition of chemotherapy-induced senescence via the inactivation of p53. This study provides experimental evidence for the preclinical value of increasing chemotherapy-induced senescence by targeting COX-2 as an effective antitumor treatment in patients with recurrent NPC.

Induction and Validation of Cellular Senescence in Primary Human Cells

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a hallmark of various pathophysiological conditions including tumor suppression, tissue remodeling and aging. The inducers of cellular senescence in vivo are still poorly characterized. However, a number of stimuli can be used to promote cellular senescence ex vivo. Among them, most common senescence-inducers are replicative exhaustion, ionizing and non-ionizing radiation, genotoxic drugs, oxidative stress, and demethylating and acetylating agents. Here, we will provide detailed instructions on how to use these stimuli to induce fibroblasts into senescence. This protocol can easily be adapted for different types of primary cells and cell lines, including cancer cells. We also describe different methods for the validation of senescence induction. In particular, we focus on measuring the activity of the lysosomal enzyme Senescence-Associated β-galactosidase (SA-β-gal), the rate of DNA synthesis using 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, the levels of expression of the cell cycle inhibitors p16 and p21, and the expression and secretion of members of the Senescence-Associated Secretory Phenotype (SASP). Finally, we provide example results and discuss further applications of these protocols.

The effects of graded caloric restriction: XII. Comparison of mouse to human impact on cellular senescence in the colon

Calorie restriction (CR) is an effective strategy to delay the onset and progression of aging phenotypes in a variety of organisms. Several molecular players are involved in the anti‐aging effects of CR, but mechanisms of regulation are poorly understood. Cellular senescence—a cellular state of irreversible growth arrest—is considered a basic mechanism of aging. Senescent cells accumulate with age and promote a number of age‐related pathologies. Whether environmental conditions such as diet affect the accumulation of cellular senescence with age is still unclear. Here, we show that a number of classical transcriptomic markers of senescent cells are reduced in adult but relatively young mice under CR. Moreover, we demonstrate that such senescence markers are not induced in the colon of middle‐age human volunteers under CR in comparison with age‐matched volunteers consuming normal Western diets. Our data support the idea that the improvement in health span observed in different organisms under CR might be partly due to a reduction in the number of senescent cells.

Decreased levels of the serum inflammatory biomarkers, sGP130, IL-6, sCRP and BAFF, are associated with increased likelihood of AIDS related Kaposi's sarcoma in men who have sex with men

AIDS-related Kaposi’s sarcoma (AIDS-KS) risk remains substantially elevated compared with the general population, even among patients who receive effective combination antiretroviral therapy. This study investigated the role of inflammatory and immune activating biomarkers in AIDS-KS in men who have sex with men in the Multicenter AIDS Cohort study between 1984 and 2010. Concentrations of 24 serum biomarkers; IL-1β, IL-2, IL-6, IL-8, IL-10, IL-12p70, sGP130, sIL-2Rα, sIL-6R, eotaxin, MCP-1, MCP4, MIP 1β, TARC, BLC-BCA1, IP-10, GM-CSF, IFN-γ, BAFF, sCD14, CD27, sTNFR-2, sCRP, and TNF-α were tested longitudinally in 1,501 men. The concentrations of each biomarker were compared between AIDS-KS cases and controls at multiple time points, 0–1 years, 1–2 years, 2–3 year, 3–5 years and over 5 years, prior to KS diagnosis or study termination, using univariate non-parametric Kruskal-Wallis tests and logistic regression, adjusted for HBV and HCV co-infection, race/ethnicity, age at last visit, education, smoking and CD4+ cell count. In univariate analyses, concentrations of four markers were consistently higher in cases; sIL-2Rα, IP-10, sTNFR-2, MCP-1, and five were higher in controls; GM-CSF, IL-6, MIP-1β, sCRP, sGP130. In the adjusted models concentrations of four markers were significantly inversely associated with AIDS-KS risk including sGP130 (OR=0.14, 95% CI = 0.03–0.73, BAFF (OR=0.60, 95% CI =0.16–0.90), sCRP (OR=0.61, 95% CI = 0.43–0.87) and IL-6 (OR=0.51, 95% CI = 0.35–0.76). These results support a role for markers of immune activation and inflammation in AIDS-KS and may highlight pathways to be targeted for risk stratification or therapeutics.

Targeting DTL induces cell cycle arrest and senescence and suppresses cell growth and colony formation through TPX2 inhibition in human hepatocellular carcinoma cells

Background

Hepatocellular carcinoma (HCC) has an increasing incidence and high mortality. Surgical operation is not a comprehensive strategy for liver cancer. Moreover, tolerating systemic chemotherapy is difficult for patients with HCC because hepatic function is often impaired due to underlying cirrhosis. Therefore, a comprehensive strategy for cancer treatment should be developed. DTL (Cdc10-dependent transcript 2) is a critical regulator of cell cycle progression and genomic stability. In our previous study, the upregulation of DTL expression in aggressive HCC correlated positively with tumor grade and poor patient survival. We hypothesize that targeting DTL may provide a novel therapeutic strategy for liver cancer. DTL small interference RNAs were used to knock down DTL protein expression.

Methods

A clonogenic assay, immunostaining, double thymidine block, imaging flow cytometry analysis, and a tumor spheroid formation assay were used to analyze the role of DTL in tumor cell growth, cell cycle progression, micronucleation, ploidy, and tumorigenicity.

Results

Our results demonstrated that targeting DTL reduced cell cycle regulators and chromosome segregation genes, resulting in increased cell micronucleation. DTL depletion inhibited liver cancer cell growth, increased senescence, and reduced tumorigenesis. DTL depletion resulted in the disruption of the mitotic proteins cyclin B, CDK1, securin, seprase, Aurora A, and Aurora B as well as the upregulation of the cell cycle arrest gene p21. A rescue assay indicated that DTL should be targeted through TPX2 downregulation for cancer cell growth inhibition. Moreover, DTL silencing inhibited the growth of patient-derived primary cultured HCC cells.

Conclusion

Our study results indicate that DTL is a potential novel target gene for treating liver cancer through liver cancer cell senescence induction. Furthermore, our results provide insights into molecular mechanisms for targeting DTL in liver cancer cells. The results also indicate several other starting points for future preclinical and clinical studies on liver cancer treatment.

Transcriptional repression of DNA repair genes is a hallmark and a cause of cellular senescence

Cellular senescence response is (i) activated by numerous stresses, (ii) is characterized by a stable proliferation arrest, and (iii) by a set of specific features. Timely regulated senescence is thought to be beneficial, whereas chronic senescence such as during normal or premature aging is deleterious as it favors most, if not all, age-related diseases. In this study, using in-house or publicly available microarray analyses of transcriptomes of senescent cells, as well as analyses of the level of expression of several DNA repair genes by RT-qPCR and immunoblot, we show that repression of DNA repair gene expression is associated with cellular senescence. This repression is mediated by the RB/E2F pathway and it may play a causal role in senescence induction, as single DNA repair gene repression by siRNA induced features of premature senescence. Importantly, activating RB independently of direct DNA damage also results in repression of DNA repair genes and in the subsequent induction of DNA damage and senescence. The dogma is that DNA damage observed during cellular senescence is directly provoked by DNA lesions following genotoxic attack (UV, IR, and ROS) or by induction of replicative stress upon oncogenic activation. Our in vitro results support a largely unsuspected contribution of the loss of DNA repair gene expression in the induction and the accumulation of the DNA damage observed in most, if not all, kinds of cellular senescence, and thus in the induction of cellular senescence. Further demonstration using in vivo models will help to generalize our findings.

[Soluble PD-1 over-expression enhances the anti-tumor effect of senescence tumor cell vaccine against breast cancer cell growth in tumor-bearing mice]

OBJECTIVE

To investigate whether soluble PD-1 overexpression in 4T1 senescence tumor cells enhances the antitumor effect of senescence tumor cell vaccine (STCV) against breast tumor cells in a tumor-bearing mouse model.

METHODS

4T1 cells were treated with interferon-γ (IFN-γ) and the expression of PD-L1 was detected by flow cytometry. CCK8 assay was used to compare the cell proliferation activity between 4T1 cells and 4T1 cells infected by a lentiviral vector of sPD-1 (4T1/sPD-1 cells), and the expressions of sPD-1 mRNA and protein in 4T1/sPD-1 cells were detected using qPCR and Western blotting. The culture supernatant of 4T1/sPD-1 cells was added in 4T1 cells pre-treated with IFN-γ, and PD-1-positive 4T1 cells were detected with flow cytometry. Senescence β-galactosidase staining kit was used to detect the senescent 4T1 and 4T1/sPD-1 cells following exposure to X-ray radiation and Veliparib. Balb/c mice bearing subcutaneous 4T1 tumor xenografts were treated with injections of PBS, 4T1 STCV, or 4T1/sPD-1 STCV, and tumor growth was observed.

RESULTS

Stimulation with IFN-γ concentration-dependently up-regulated PD-L1 expression by as much as (84.80 ± 1.03)% in 4T1 cells (P < 0.001). sPD-1 overexpression in 4T1 cells did not significantly affect the cell proliferation. Treatment of 4T1 cells with 4T1/sPD-1 cell culture supernatant significantly increased the proportion of PD-1 + cells from (6.893 ± 0.271)% to (55.450 ± 0.555)% (P < 0.001). X-ray irradiation combined with Veliparib caused obvious senescence in 4T1 and 4T1/sPD-1 cells. In the tumor-preventing experiment, tumor formation occurred in all the mice in PBS group; 28.787% of the mice in 4T1 STCV group and 55.556% in 4T1/sPD-1 STCV group showed no tumor formation. In the tumor treatment experiment, tumor formation occurred in all the mice in PBS groups while in 4T1 STCV and 4T1/sPD-1 STCV groups, 11.111% and 38.89% of the mice were tumor-free during the observation period, respectively.

CONCLUSIONS

Senescence tumor cells vaccine has antitumor effect against breast cancer in mice, and sPD-1 overexpression can enhance this effect of the vaccine.