Tumor suppressor mechanisms in immune aging

The Interplay Between the Immune System, Tumor Suppressor Genes, and Immune Senescence in Mesothelioma Development and Response to Immunotherapy

Despite efforts to ban asbestos mining and manufacturing, mesothelioma deaths in the United States have remained stable at approximately 2500 cases annually. This trend is not unique to the United States but is also a global phenomenon, associated with increased aging of populations worldwide. Although geoeconomic factors such as lack of regulations and continued asbestos manufacturing in resource-poor countries play a role, it is essential to consider biological factors such as immune senescence and increased genetic instability associated with aging. Recognizing that mesothelioma shares genetic instability and immune system effects with other age-related cancers is crucial because the impact of aging on mesothelioma is frequently assessed in the context of disease latency after asbestos exposure. Nevertheless, the long latency period, often cited as a reason for mesothelioma's elderly predominance, should not overshadow the shared mechanisms. This communication focuses on the role of immune surveillance in mesothelioma, particularly exploring the impact of immune escape resulting from altered TSG function during aging, contributing to the phylogenetic development of gene mutations and mesothelioma oncogenesis. The interplay between the immune system, TSGs, and aging not only shapes the immune landscape in mesothelioma but also contributes to the development of heterogeneous tumor microenvironments, significantly influencing responses to immunotherapy approaches and survival rates. By understanding the complex interplay between aging, TSG decline, and immune senescence, health care professionals can pave the way for more effective and personalized immunotherapies, ultimately offering hope for better outcomes in the fight against mesothelioma.

Caloric Restriction Intervention Alters Specific Circulating Biomarkers of the Senescence-Associated Secretome in Middle-Aged and Older Adults With Obesity and Prediabetes in an 18-Week Randomized Controlled Trial

Cellular senescence is a biological aging process that is exacerbated by obesity and leads to inflammation and age- and obesogenic-driven chronic diseases including type 2 diabetes. Caloric restriction (CR) may improve metabolic function in part by reducing cellular senescence and the pro-inflammatory senescence-associated phenotype (SASP). We conducted an ancillary investigation of an 18-week randomized controlled trial (RCT) of CR (n = 31) or Control (n = 27) in 58 middle-aged/older adults (57.6 ± 5.8 years; 75% Women) with obesity and prediabetes. We measured mRNA expression of select senescence and apoptosis genes in blood CD3 + T cells (qRT-PCR) and a panel of 25 plasma SASP proteins (Luminex/multiplex; ELISA). Participants randomized to CR lost -10.8 ± 0.9 kg (-11.3% ± 5.4%) over 18 weeks compared with +0.5 ± 0.9 kg (+0.03% ± 3.5%) in Control group. T-cell expression of senescence biomarkers, p16INK4a and p21CIP1/WAF1, and apoptosis markers, BCL2L1 and BAK1, was not different between CR and Control groups in age, race, and sex-adjusted mixed models (p > .05, all). Iterative principal axis factor analysis was used to develop composite SASP Factors, and the Factors comprising TNFRI, TNFRII, uPAR, MMP1, GDF15, OPN, Fas, and MPO were significantly altered with CR intervention (age, sex, race-adjusted mixed model time × treatment F = 4.17, p ≤ .05) and associated with the degree of weight loss (R2 = 0.12, p ≤ .05). Our study provides evidence from an RCT that specific circulating biomarkers of senescent cell burden are changed by CR in middle-aged and older adults with obesity and prediabetes. Future studies compare tissue and circulating levels of p16INK4a and pro-inflammatory SASP biomarkers in other populations, and interventions.

Comprehensive single cell aging atlas of mammary tissues reveals shared epigenomic and transcriptomic signatures of aging and cancer

Aging is the greatest risk factor for breast cancer; however, how age-related cellular and molecular events impact cancer initiation is unknown. We investigate how aging rewires transcriptomic and epigenomic programs of mouse mammary glands at single cell resolution, yielding a comprehensive resource for aging and cancer biology. Aged epithelial cells exhibit epigenetic and transcriptional changes in metabolic, pro-inflammatory, or cancer-associated genes. Aged stromal cells downregulate fibroblast marker genes and upregulate markers of senescence and cancer-associated fibroblasts. Among immune cells, distinct T cell subsets (Gzmk+, memory CD4+, γδ) and M2-like macrophages expand with age. Spatial transcriptomics reveal co-localization of aged immune and epithelial cells in situ. Lastly, transcriptional signatures of aging mammary cells are found in human breast tumors, suggesting mechanistic links between aging and cancer. Together, these data uncover that epithelial, immune, and stromal cells shift in proportions and cell identity, potentially impacting cell plasticity, aged microenvironment, and neoplasia risk.

Exploiting pivotal mechanisms behind the senescence-like cell cycle arrest in cancer

Senescence-like cell cycle arrest is a critical state of cancer initiation and progression. Senescence is an irreversible cell cycle arrest in response to stress induced by extrinsic and intrinsic stimuli, including oxidative/genotoxic stress, oncogenic activation, irradiation, mitochondrial malfunction, or chemotherapeutic drugs. Several signaling pathways are involved in senescence-like cell cycle arrest, which is primarily induced by the activation of p53/p21-dependent apoptotic pathways and suppressing p16INK4A/retinoblastoma protein (pRB)-dependent oncogenic pathways. p21 is necessary for proper cell cycle advancement, is involved in cell death, and mediates p53-dependent cell cycle arrest caused by DNA damage. pRB's role in tumor suppression is through modulation of the G1 checkpoint in the cell cycle, as it has the ability to block S-phase entry and cell growth. The aforementioned pathways are also highly interconnected with significant crosstalk, such as cyclin-dependent kinases (CDK)/cyclin complexes, and the dimerization partner, RB-like, E2F and multi-vulval class B (DREAM) complex. The primary regulators of transcription are p53 and pRB, which maintain the senescent state through negative control of the cell cycle and process of tumorigenesis. Because CDK inhibitors comprise negative regulators of cell cycle progress, they are fundamental parts of each route. Prolonged overexpression of any of these four fundamental elements (p16, p53, p21, and pRB) suffices to induce senescence, demonstrating how the regulatory DREAM complex causes senescence and how its malfunction results in cell cycle progression. The present chapter aims at revealing the pivotal mechanisms behind the senescence-like cell cycle arrest in cancer.

Oxidative Stress-Induced Cellular Senescence in Aging Retina and Age-Related Macular Degeneration

Aging leads to a gradual decline of function in multiple organs. Cataract, glaucoma, diabetic retinopathy, and age-related macular degeneration (AMD) are age-related ocular diseases. Because their pathogenesis is unclear, it is challenging to combat age-related diseases. Cellular senescence is a cellular response characterized by cell cycle arrest. Cellular senescence is an important contributor to aging and age-related diseases through the alteration of cellular function and the secretion of senescence-associated secretory phenotypes. As a driver of stress-induced premature senescence, oxidative stress triggers cellular senescence and age-related diseases by inducing senescence markers via reactive oxygen species and mitochondrial dysfunction. In this review, we focused on the mechanism of oxidative stress-induced senescence in retinal cells and its role in the pathogenesis of AMD.

Tumor suppressor gene mutations correlate with prognosis and immunotherapy benefit in hepatocellular carcinoma

INTRODUCTION

The tumor microenvironment (TME) has profound impacts on prognosis and immunotherapy. The TME can be altered by the genomic mutations on specific tumor-suppressor genes (TSG), thus, comprehending the association between TME and TSG in hepatocellular carcinoma (HCC) is imperative.

METHODS

With a total of 1699 HCC patients from 6 international multicenter cohorts, we delineated the mutational landscape of TSG and summarized the proportion of TSG mutated HCC in different countries. Using the genomic and transcriptomic data, we comprehensively explored the impacts of TSG mutations on TME and immunity in HCC. A dataset of 31 HCC patients from the cBioPortal database was utilized to evaluate the predictive value of TSG subtypes for immunotherapy response.

RESULTS

Interestingly, TSG non-mutated HCC will have more "immune-hot" tumors, and display the infiltration abundance of immune cells such as B cell, CD4+/CD8+T cell, and neutrophil. Moreover, TSG non-mutated HCC was characterized by the higher expression level of three immune checkpoints, including CD40, CD40LG, and TNFRSF4. In line with the TME characterization and immune checkpoint profiles, TSG non-mutated HCC displayed prolonged overall survival and relapse-free survival, notably, are more likely to respond to immune checkpoint inhibitors.

CONCLUSIONS

Our findings suggested the TSG subtypes could serve as a promising biomarker for guiding surveillance protocol and immunotherapeutic decisions for patients with HCC.

Integrative Genomic and Transcriptomic Analyses of Tumor Suppressor Genes and Their Role on Tumor Microenvironment and Immunity in Lung Squamous Cell Carcinoma

Non-small-cell lung cancers (NSCLCs) are largely classified into lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), which have different therapeutic options according to its molecular profiles and immune checkpoint expression, especially PD-L1, which is a suppressive factor in the tumor microenvironment. The tumor microenvironment can be altered by the genomic mutations on specific innate immune genes as well as tumor suppressor genes, so it is essential to comprehend the association between tumor microenvironment and tumor suppressor genes to discover the promising immunotherapeutic strategy to overcome the resistance of immune check point blockade. In this study, we aimed to analyze how the somatic mutations in tumor suppressor genes affect the tumor immune microenvironment through a comprehensive analysis of mutational profiling on the representative tumor suppressor genes (TP53, CDKN2A, PTEN, RB1, BRCA1, BRCA2) and immune gene expression in The Cancer Genome Atlas (TCGA) 155 lung squamous cell carcinoma (LUSC) and 196 lung adenocarcinoma (LUAD) samples. Several microenvironmental factors, such as the infiltrating immune and stromal cells, were suppressed by the mutated tumor suppressor genes in LUSC, unlike in the LUAD samples. In particular, infiltrating immune cells such as macrophage, neutrophil, and dendritic cells were significantly reduced in tumors with mutated tumor suppressor genes' group. In addition, the gene expressions for interleukin production and lymphocyte differentiation and PGC, C7, HGF, PLA2G2A, IL1RL1, CCR2, ALOX15B, CXCL11, FCN3 were significantly down-regulated, which were key immune genes for the cross-talk between LUSC microenvironment and tumor suppressors. Therefore, we generated evidence that TSG mutations in LUSC have an impact on tumor immune microenvironment, which suggests that TSG non-mutated patients will have the more inflamed tumors and are more likely to respond to immune checkpoint blockade therapy.

Hallmarks and detection techniques of cellular senescence and cellular ageing in immune cells

The ageing of the global population brings about unprecedented challenges. Chronic age‐related diseases in an increasing number of people represent an enormous burden for health and social care. The immune system deteriorates during ageing and contributes to many of these age‐associated diseases due to its pivotal role in pathogen clearance, tissue homeostasis and maintenance. Moreover, in order to develop treatments for COVID‐19, we urgently need to acquire more knowledge about the aged immune system, as older adults are disproportionally and more severely affected. Changes with age lead to impaired responses to infections, malignancies and vaccination, and are accompanied by chronic, low‐degree inflammation, which together is termed immunosenescence. However, the molecular and cellular mechanisms that underlie immunosenescence, termed immune cell senescence, are mostly unknown. Cellular senescence, characterised by an irreversible cell cycle arrest, is thought to be the cause of tissue and organismal ageing. Thus, better understanding of cellular senescence in immune populations at single‐cell level may provide us with insight into how immune cell senescence develops over the life time of an individual. In this review, we will briefly introduce the phenotypic characterisation of aged innate and adaptive immune cells, which also contributes to overall immunosenescence, including subsets and function. Next, we will focus on the different hallmarks of cellular senescence and cellular ageing, and the detection techniques most suitable for immune cells. Applying these techniques will deepen our understanding of immune cell senescence and to discover potential druggable pathways, which can be modulated to reverse immune ageing.

Role of PARP-catalyzed ADP-ribosylation in the Crosstalk Between DNA Strand Breaks and Epigenetic Regulation

Covalent linkage of ADP-ribose units to proteins catalyzed by poly(ADP-ribose) polymerases (PARPs) plays important signaling functions in a plethora of cellular processes including DNA damage response, chromatin organization, and gene transcription. Poly- and mono-ADP-ribosylation of target macromolecules are often responsible both for the initiation and for coordination of these processes in mammalian cells. Currently, the number of cellular targets for ADP-ribosylation is rapidly expanding, and the molecular mechanisms underlying the broad substrate specificity of PARPs present enormous interest. In this review, the roles of PARP-mediated modifications of protein and nucleic acids, the readers of ADP-ribosylated structures, and the origin and function of programmed DNA strand breaks in PARP activation, transcription regulation, and DNA demethylation are discussed.

TP53INP1 deficiency maintains murine B lymphopoiesis in aged bone marrow through redox-controlled IL-7R/STAT5 signaling

Bone marrow (BM) produces all blood and immune cells deriving from hematopoietic stem cells (HSCs). The decrease of immune cell production during aging is one of the features of immunosenescence. The impact of redox dysregulation in BM aging is still poorly understood. Here we use TP53INP1-deficient (KO) mice endowed with chronic oxidative stress to assess the influence of aging-associated redox alterations in BM homeostasis. We show that TP53INP1 deletion has no impact on aging-related accumulation of HSCs. In contrast, the aging-related contraction of the lymphoid compartment is mitigated in TP53INP1 KO mice. B cells that accumulate in old KO BM are differentiating cells that can mature into functional B cells. Importantly, this phenotype results from B cell-intrinsic events associated with defective redox control. Finally, we show that oxidative stress in aged TP53INP1-deficient mice maintains STAT5 expression and activation in early B cells, driving high Pax5 expression, which provides a molecular mechanism for maintenance of B cell development upon aging.

High CpG island methylation of p16 gene and loss of p16 protein expression associate with the development and progression of tetralogy of Fallot

We examined CpG island methylation in p16 gene and its effect on p16 protein expression in tetralogy of Fallot (ToF) patients to explore its potential implications in the development and progression of ToF. The study subjects consisted of 75 healthy controls and 63 ToF patients recruited at Linyi People's Hospital between January 2012 and June 2014. The 4 mL of peripheral venous blood of each subject was obtained and saved in ethylene diamine tetraacetic acid (EDTA) tubes. Methylation-specific polymerase chain reaction (MSP) was employed to detect CpG island methylation in p16 promoter region andWestern blotting was used to detect p16 expression of all subjects. Real-time fluorescence quantitative polymerase chain reaction (FQ-PCR) was performed to test p16 mRNA expression. The results showed that p16-methylation rates in ToF group were significantly higher than the control group (ToF group, 58.73%; control group, 13.33%; P < 0.001). Remarkably, Western blotting and FQ-PCR results derived from RVOT revealed that p16 protein expression was significantly lower in ToF group compared tothe control group (0.76 ± 0.21 versus 2.31 ± 0.35; P < 0.001), and p16 gene expression was also markedly decreased in ToF group (1.212 ± 0.152 versus 1.346 ± 0.191, P < 0.001). Additionally, our analysis suggested that CpG island methylation in p16 promoters in ToF patients was negatively correlated with p16 protein and gene expression (both P < 0.05). Our study reports that high CpG island methylation of p16 gene and loss of p16 protein expression associate with the development and progression of ToF, which may have significant therapeutic applications for ToF.

Milush J, Cunha-Neto E, G. Kallas E, Kalil J, D. Passero LF, W. Hunt P, G. Deeks S, F. Nixon D, SenGupta D. p16INK4a Expression and Immunologic Aging in Chronic HIV Infection

Chronic HIV infection is characterized by increased immune activation and immunosenescence. p16 ^INK4a (p16) is a member of the cyclin-dependent kinase antagonist family that inhibits cellular proliferation, and its protein expression increases during normal chronological aging. However, some infectious diseases can increase the expression of this anti-proliferative protein, potentially accelerating immunological aging and dysfunction. In order to investigate the immunological aging in HIV patients, p16 protein expression was evaluated by flow cytometry, in T cell subsets in a cohort of chronically HIV-infected patients on and off ART as well as age-matched healthy controls. Results showed that untreated HIV-infected subjects exhibited increased per-cell p16 protein expression that was discordant with chronological aging. ART restored p16 protein expression to levels comparable with HIV-negative subjects in the CD4 compartment, but not in CD8 T cells, which can be an indicative of an irreversible activation/exhaustion status on these cells. Additionally, the frequency of activated CD4+ and CD8+ T cells was positively correlated with p16 expression in CD4+ and CD8+ T cells in untreated subjects. In contrast to healthy controls, untreated HIV-infected individuals had increased p16 levels within the effector memory (T_EM) subset, indicating a possible role for this marker in impaired clonal expansion during antiviral effector function. Taken together, these data demonstrate that chronic HIV infection is associated with elevated expression of the cellular aging marker p16 in T cells. ART restored normal p16 levels in the CD4+ T cell compartment, indicating that use of therapy can be of fundamental importance to normal cell cycling and maintaining immune homeostasis.

Forging a signature of in vivo senescence

'Cellular senescence', a term originally defining the characteristics of cultured cells that exceed their replicative limit, has been broadened to describe durable states of proliferative arrest induced by disparate stress factors. Proposed relationships between cellular senescence, tumour suppression, loss of tissue regenerative capacity and ageing suffer from lack of uniform definition and consistently applied criteria. Here, we highlight caveats in interpreting the importance of suboptimal senescence-associated biomarkers, expressed either alone or in combination. We advocate that more-specific descriptors be substituted for the now broadly applied umbrella term 'senescence' in defining the suite of diverse physiological responses to cellular stress.

Age-Associated Failure To Adjust Type I IFN Receptor Signaling Thresholds after T Cell Activation

With increasing age, naive CD4 T cells acquire intrinsic defects that compromise their ability to respond and differentiate. Type I IFNs, pervasive constituents of the environment in which adaptive immune responses occur, are known to regulate T cell differentiation and survival. Activated naive CD4 T cells from older individuals have reduced responses to type I IFN, a defect that develops during activation and that is not observed in quiescent naive CD4 T cells. Naive CD4 T cells from young adults upregulate the expression of STAT1 and STAT5 after activation, lowering their threshold to respond to type I IFN stimulation. The heightened STAT signaling is critical to maintain the expression of CD69 that regulates lymphocyte egress and the ability to produce IL-2 and to survive. Although activation of T cells from older adults also induces transcription of STAT1 and STAT5, failure to exclude SHP-1 from the signaling complex blunts their type I IFN response. In summary, our data show that type I IFN signaling thresholds in naive CD4 T cells after activation are dynamically regulated to respond to environmental cues for clonal expansion and memory cell differentiation. Naive CD4 T cells from older adults have a defect in this threshold calibration. Restoring their ability to respond to type I IFN emerges as a promising target to restore T cell responses and to improve the induction of T cell memory.

Involvement of oxysterols in age-related diseases and ageing processes

Ageing is accompanied by increasing vulnerability to major pathologies (atherosclerosis, Alzheimer's disease, age-related macular degeneration, cataract, and osteoporosis) which can have similar underlying pathoetiologies. All of these diseases involve oxidative stress, inflammation and/or cell death processes, which are triggered by cholesterol oxide derivatives, also named oxysterols. These oxidized lipids result either from spontaneous and/or enzymatic oxidation of cholesterol on the steroid nucleus or on the side chain. The ability of oxysterols to induce severe dysfunctions in organelles (especially mitochondria) plays key roles in RedOx homeostasis, inflammatory status, lipid metabolism, and in the control of cell death induction, which may at least in part contribute to explain the potential participation of these molecules in ageing processes and in age related diseases. As no efficient treatments are currently available for most of these diseases, which are predicted to become more prevalent due to the increasing life expectancy and average age, a better knowledge of the biological activities of the different oxysterols is of interest, and constitutes an important step toward identification of pharmacological targets for the development of new therapeutic strategies.

Busulfan inhibits growth of human osteosarcoma through miR-200 family microRNAs in vitro and in vivo

Osteosarcoma typically arises in tissues of mesenchymal origin, and is the most malignant bone tumor characterized by high local aggressiveness, with poor therapeutic outcome. Busulfan has been widely used to treat CML. So far, there are no reports on the therapeutic effect of busulfan on osteosarcoma. Here, we showed that busulfan dose-dependently reduced the cell viability and proliferation, and induced cell apoptosis, senescence, and reactive oxygen species levels in two osteosarcoma cell lines. Moreover, a series of loss-of-function and gain-of-function experiments further indicated that busulfan may have its anti-osteosarcoma effect by upregulating the microRNA-200 (miR-200) family which subsequently downregulated its target genes ZEB1 and ZEB2. Furthermore, treatment with busulfan potentially inhibited the growth of implanted osteosarcoma in nude mice. Taken together, our data suggest that busulfan may have an anti-osteosarcoma effect through downregulating ZEB1 and ZEB2 through activating the miR-200 family, highlighting a possibility of using busulfan as a novel therapy for osteosarcoma.

The molecular balancing act of p16(INK4a) in cancer and aging

p16(INK4a), located on chromosome 9p21.3, is lost among a cluster of neighboring tumor suppressor genes. Although it is classically known for its capacity to inhibit cyclin-dependent kinase (CDK) activity, p16(INK4a) is not just a one-trick pony. Long-term p16(INK4a) expression pushes cells to enter senescence, an irreversible cell-cycle arrest that precludes the growth of would-be cancer cells but also contributes to cellular aging. Importantly, loss of p16(INK4a) is one of the most frequent events in human tumors and allows precancerous lesions to bypass senescence. Therefore, precise regulation of p16(INK4a) is essential to tissue homeostasis, maintaining a coordinated balance between tumor suppression and aging. This review outlines the molecular pathways critical for proper p16(INK4a) regulation and emphasizes the indispensable functions of p16(INK4a) in cancer, aging, and human physiology that make this gene special.

Understanding immunosenescence to improve responses to vaccines

In the older adult, the benefits of vaccination to prevent infectious disease are limited, mainly because of the adaptive immune system's inability to generate protective immunity. The age-dependent decrease in immunological competence, often referred to as 'immunosenescence', results from the progressive deterioration of innate and adaptive immune responses. Most insights into mechanisms of immunological aging have been derived from studies of mouse models. In this Review, we explore how well such models are applicable to understanding the aging process throughout the 80-100 years of human life and discuss recent advances in identifying and characterizing the mechanisms that underlie age-associated defective adaptive immunity in humans.

Expression of p16(INK4a) as a biomarker of T-cell aging in HIV-infected patients prior to and during antiretroviral therapy

The p16(INK4a) tumor suppressor gene is a mediator of cellular senescence and has been suggested to be a biomarker of 'molecular' age in several tissues including T cells. To determine the association of both active and suppressed HIV infection with T-cell aging, T-cell p16(INK4a) expression was compared between 60 HIV+ suppressed subjects, 23 HIV+ untreated subjects, and 18 contemporaneously collected HIV-negative controls, as well as 148 HIV-negative historical samples. Expression did not correlate with chronologic age in untreated HIV+ patients, consistent with an effect of active HIV replication on p16(INK4a) expression. In patients on cART with suppressed viral loads, however, p16(INK4a) levels were similar to uninfected controls and correlated with chronologic age, with a trend toward an inverse correlation with CD4 count. These data show that p16(INK4a) is a reliable biomarker of T-cell aging in HIV+ patients with suppressed viral loads and suggest that poor CD4 cell recovery on cART may be associated with increased T-cell expression of p16(INK4a), a marker of cellular senescence.

Fibroblast growth factor-7 partially reverses murine thymocyte progenitor aging by repression of Ink4a

Involution of the thymus results in reduced production of naive T cells, and this in turn is thought to contribute to impaired immunity in the elderly. Early T-cell progenitors (ETPs), the most immature intrathymic T-cell precursors, harvested from the involuted thymus exhibit a diminished proliferative potential and increased rate of apoptosis and as a result their number is significantly reduced. In the present study, we show that these age-induced alterations result in part from increased expression of the Ink4a tumor-suppressor gene in ETPs. We also show that repression of Ink4a in aged ETPs results in their partial rejuvenation and that this can be accomplished by in vivo fibroblast growth factor 7 administration. These results define a genetic basis for thymocyte progenitor aging and demonstrate that the senescence-associated gene Ink4a can be pharmacologically repressed in ETPs to partially reverse the effects of aging.

Shelterin dysfunction and p16(INK4a)-mediated growth inhibition in HIV-1-specific CD8 T cells

HIV-1-specific cytotoxic T cell responses are expanded during advanced HIV-1 infection but seem unable to effectively protect the host against disease progression. These cells are able to produce gamma interferon and remain metabolically active but have defective proliferative activities, shortened telomeric DNA, and other signs of accelerated aging. To investigate the molecular mechanisms underlying the premature senescence of HIV-1-specific T cells, we focused here on the expression and function of a group of six nucleoproteins that are responsible for protecting and maintaining the structural integrity of telomeric DNA and are commonly referred to as "shelterin." We show that in progressive HIV-1 infection, the two major shelterin components TRF2 and TPP1 are selectively reduced in HIV-1-specific CD8 T cells, but not in T cells recognizing alternative viral species. This coincided with increased recruitment of 53BP1, a prominent DNA damage response factor, to telomeric DNA sites and was associated with elevated expression of the tumor suppressor p16(INK4a), which causes cellular growth inhibition in response to structural DNA damage. Notably, defective shelterin function and upregulation of p16(INK4a) remained unaffected by experimental blockade of PD-1, indicating a possibly irreversible structural defect in HIV-1-specific CD8 T cells in progressors that cannot be overcome by manipulation of inhibitory cell-signaling pathways. These data suggest that shelterin dysfunction and ensuing upregulation of the tumor suppressor p16(INK4a) promote accelerated aging of HIV-1-specific T cells during progressive HIV-1 infection.

Prognostic significance of CDKN2A (p16) promoter methylation and loss of expression in 902 colorectal cancers: Cohort study and literature review

A cyclin-dependent kinase inhibitor CDKN2A (p16/Ink4a) is a tumor suppressor and upregulated in cellular senescence. CDKN2A promoter methylation and gene silencing are associated with the CpG island methylator phenotype (CIMP) in colon cancer. However, prognostic significance of CDKN2A methylation or loss of CDKN2A (p16) expression independent of CIMP status remains uncertain. Using a database of 902 colorectal cancers in 2 independent cohort studies (the Nurses' Health Study and the Health Professionals Follow-up Study), we quantified CDKN2A promoter methylation and detected hypermethylation in 269 tumors (30%). By immunohistochemistry, we detected loss of CDKN2A (p16) expression in 25% (200/804) of tumors. We analyzed for LINE-1 hypomethylation and hypermethylation at 7 CIMP-specific CpG islands (CACNA1G, CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1); microsatellite instability (MSI); KRAS, BRAF and PIK3CA mutations; and expression of TP53 (p53), CTNNB1 (β-catenin), CDKN1A (p21), CDKN1B (p27), CCND1 (cyclin D1), FASN (fatty acid synthase) and PTGS2 (cyclooxygenase-2). CDKN2A promoter methylation and loss of CDKN2A (p16) were associated with shorter overall survival in univariate Cox regression analysis [hazard ratio (HR): 1.36, 95% CI: 1.10-1.66, p = 0.0036 for CDKN2A methylation; HR: 1.30, 95% CI: 1.03-1.63, p = 0.026 for CDKN2A (p16) loss] but not in multivariate analysis that adjusted for clinical and tumor variables, including CIMP, MSI and LINE-1 methylation. Neither CDKN2A promoter methylation nor loss of CDKN2A (p16) was associated with colorectal cancer-specific mortality in uni- or multivariate analysis. Despite its well-established role in carcinogenesis, CDKN2A (p16) promoter methylation or loss of expression in colorectal cancer is not independently associated with patient prognosis.

Ageing and immunity: addressing immune senescence to ensure healthy ageing

Among the greatest achievements of the 20th century, prolongation of life expectancy has been the result of improved health conditions, decreased childhood mortality, lower incidence of infectious diseases. The consequence is the rapid ageing of the world population, with the elderly representing over 25% of the entire population by the year 2030, of which 75% living in less developed countries. Ageing thus represents one of the major public health challenges of the 21st century. Indeed, unhealthy ageing and frailty of the aged population has an important impact on the economic development and social costs of a country, a problem even more acute in less developed countries. A better knowledge of immune senescence and the design of customised vaccination strategies for the elderly are the immediate challenges posed to scientists and physicians. The conference "Ageing and immunity", recently held in Siena (Italy), has addressed these issues and defined the global strategic priorities for research and health policies aimed at ensuring healthy ageing.