Polyfunctional KLRG-1+CD57+ Senescent CD4+ T Cells Infiltrate Tumors and Are Expanded in Peripheral Blood From Breast Cancer Patients

CD8+ T cells in breast cancer tumors and draining lymph nodes: PD-1 levels, effector functions and prognostic relevance

CD8+ T cells shape the antitumor immune response. Here, we evaluated CD8+ T cells expressing different levels of PD-1, their functional status, and distribution in different tissues of luminal breast cancer (BC) patients. We characterized the exhaustion stages of CD8+ T cells in tumors, juxtatumoral tissues (JTs), and tumor-draining lymph nodes (TDLNs). Terminal exhausted CD8+ T cells (PD-1High CD8+) were predominant in tumors and nearly absent in other tissues. However, in all tissues evaluated, most CD8+ T cells exhibited a pre-exhausted phenotype (PD-1Int CD8+) or did not express PD-1. PD-1High and PD-1Int CD8+ T cells from tumors and JTs presented central and effector memory phenotypes, while in TDLNs were primarily central memory. TCR-β sequencing revealed higher clonality among CD8+ T cells from tumor than TDLNs, with tumor-enriched clones also detected in TDLNs. Analysis of scRNA-seq datasets from tumors and JTs of colorectal and non-small cell lung cancer patients, identified a CD8+ terminal exhaustion and a CD8+ pre-exhausted signatures. High expression of exhaustion-associated genes in BC tumors correlated with improved overall survival. Overall, PD-1 expression effectively distinguishes exhaustion stages in CD8+ T cells. PD-1Int cells found in tumors, JTs, and TDLNs represent a promising therapeutic target for cancer immunotherapy.

T-cell senescence: Unlocking the tumor immune "Dark Box" - A multidimensional analysis from mechanism to tumor immunotherapeutic intervention

Immunosenescence is the dysfunction of the immune system that occurs with age, a process that is complex and characterized by several features, of which T-cell senescence is one of the key manifestations. In the tumor microenvironment, senescent T cells lead to the inability of tumor cells to be effectively eliminated, triggering immunosuppression, which in turn affects the efficacy of immunotherapy. This is a strong indication that T-cell senescence significantly weakens the immune function of the body, making individuals, especially elderly patients with cancer, more vulnerable to cancer attacks. Despite the many challenges, T-cell senescence is important as a potential therapeutic target. This review provides insights into the molecular mechanisms of T-cell senescence and its research advances in patients with cancer, especially in older adults, and systematically analyzes potential intervention strategies, including molecular mechanism-based interventions, the use of immune checkpoint inhibitors, and CAR-T cell therapy. It is hoped that this will establish a theoretical framework for T-cell senescence in the field of tumor immunology and provide a scientific and prospective reference basis for subsequent in-depth research and clinical practice on senescent T cells.

T-cell Senescence in the Tumor Microenvironment

T-cell senescence occurs in the tumor microenvironment (TME) and influences cancer outcomes as well as the effectiveness of immunotherapies. The TME triggers this T-cell senescence via multiple pathways, including persistent stimulation with tumor-associated antigens, altered metabolic pathways, and activation of chronic inflammatory responses. Senescent T cells exhibit characteristics such as genomic instability, loss of protein homeostasis, metabolic dysregulation, and epigenetic alterations. Direct cross-talk between senescent T cells and other immune cells further exacerbates the immunosuppressive TME. This immune-tumor cell interaction within the TME contributes to impaired tumor antigen recognition and surveillance by T cells. The presence of senescent T cells is often associated with poor prognosis and reduced efficacy of immunotherapies; thus, targeting the tumor-promoting mechanisms of T-cell senescence may provide novel insights into improving tumor immunotherapy and patient outcomes. This review explores the contributors to tumor-derived T-cell senescence, the link between T-cell senescence and tumor prognosis, and the potential for targeting T-cell senescence to enhance tumor immunotherapy.

KLRG1 identifies regulatory T cells with mitochondrial alterations that accumulate with aging

Recent studies using single-cell RNA sequencing technology have uncovered several subpopulations of CD4+ T cells that accumulate with aging. These age-associated T cells are emerging as relevant players in the onset of inflammaging and tissue senescence. Here, based on information provided by single-cell RNA sequencing data, we present a flow cytometry panel that allows the identification of age-associated T cell subsets in systematic larger analysis in mice. We use this panel to evaluate at the single-cell level mitochondrial and senescence marks in the different age-associated CD4+ T cell subpopulations. Our analysis identifies a subpopulation of regulatory T (Treg) cells that is characterized by the extracellular expression of the co-inhibitory molecule killer cell lectin-like receptor subfamily G member 1 (KLRG1) and accumulates with aging in humans and mice. KLRG1-expressing Treg cells display senescence features such as mitochondrial alterations, increased expression of cell-cycle regulators and genomic DNA damage. Functionally, KLRG1+ Treg cells show a reduced suppressive activity in vivo accompanied by a pro-inflammatory phenotype.

Dysfunctional Senescent Herpes Simplex Virus-Specific CD57+CD8+ T Cells Are Associated with Symptomatic Recurrent Ocular Herpes in Humans

Herpes simplex virus (HSV)-specific CD8+ T cells protect mice from herpes infection and disease. However, the phenotype and function of HSV-specific CD8+ T cells that play a key role in the "natural" protection seen in HSV-1-seropositive healthy asymptomatic (ASYMP) patients (who have never had clinical herpes disease) remain to be determined. We previously reported that symptomatic (SYMP) patients (who have frequent bouts of recurrent ocular herpes disease) had more undifferentiated and dysfunctional HSV-specific CD8+ T cells. In contrast, healthy ASYMP individuals maintained a significantly higher proportion of differentiated polyfunctional CD8+ T cells. Here, we report that HSV-specific CD8+ T cells from 10 SYMP patients, but not HSV-specific CD8+ T cells from 10 ASYMP patients, have phenotypic and functional characteristics of cellular senescence, including: (i) high frequency of senescent (CD57+) and exhausted (PD-1+) CD8+ T cells; (ii) late terminally differentiated (KLRG1+), non-proliferating CD8+ T cells; (iii) HSV-specific CD8+ T cells which decreased in number over time and were not homeostatically maintained, as indicated by a reduction in the number of CD127+CD8+ T cells; (iv) loss of the co-stimulatory molecule CD28 on HSV-specific CD8+ T cells; and (v) decreased production of effector molecules (granzyme B and perforin) by HSV-specific CD8+ T cells. Our findings provide insights into the role of senescence in HSV-specific CD8+ T cells in susceptibility to recurrent herpes and have implications for T-cell-based immunotherapeutic strategies against recurrent herpes in humans.

Leveraging Vγ9Vδ2 T cells against prostate cancer through a VHH-based PSMA-Vδ2 bispecific T cell engager

Vγ9Vδ2 T cells constitute a homogeneous effector T cell population that lyses tumors of different origin, including the prostate. We generated a bispecific T cell engager (bsTCE) to direct Vγ9Vδ2 T cells to PSMA+ prostate cancer (PCa) cells. The PSMA-Vδ2 bsTCE triggered healthy donor and PCa patient-derived Vγ9Vδ2 T cells to lyse PSMA+ PCa cell lines and patient-derived tumor cells while sparing normal prostate cells and enhanced Vγ9Vδ2 T cell antigen cross-presentation to CD8+ T cells. Vγ9Vδ2 T cell expressed NKG2D and DNAM-1 contributed to Vγ9Vδ2 T cell activation and tumor lysis at low PSMA-Vδ2 bsTCE concentrations. In vivo models confirmed the antitumor efficacy of the bsTCE and demonstrated a half-life of 6-7 days. Tissue-cross reactivity analysis was in line with known tissue distribution of PSMA and Vγ9Vδ2 T cells. Together these data show the PSMA-Vδ2 bsTCE to represent a promising anti-tumor strategy and supports its ongoing evaluation in a phase 1/2a clinical trial in therapy refractory metastatic castration-resistant PCa.

Time-restricted eating reveals a "younger" immune system and reshapes the intestinal microbiome in human

Time-restricted eating (TRE) has been shown to extent lifespans in drosophila and mouse models by affecting metabolic and anti-inflammatory activities. However, the effect of TRE on the human immune system, especially on immunosenescence, intestinal microbiome, and metabolism remains unclear. We conducted a 30-day 16:8 TRE single-arm clinical trial with 49 participants. Participants consumed daily meals from 9 a.m. to 5 p.m., provided by a nutrition canteen with a balanced, calorie-appropriate nutrition, which is designed by clinical nutritionists (ChiCTR2200058137). We monitored weight changes and weight-related parameters and focused on changes in the frequency of CD4+ senescent T cells, immune repertoire from peripheral blood, as well as serum metabolites and gut microbiota. We found that up to 95.9 % of subjects experienced sustained weight loss after TRE. The frequency of circulating senescent CD4+ T cells was decreased, while the frequency of Th1, Treg, Tfh-like, and B cells was increased. Regarding the immune repertoire, the proportions of T cell receptor alpha and beta chains were increased, whereas B cell receptor kappa and lambda chains were reduced. In addition, a reduced class switch recombination from immunoglobulin M (IgM) to immunoglobulin A (IgA) was observed. TRE upregulated the levels of anti-inflammatory and anti-aging serum metabolites named sphingosine-1-phosphate and prostaglandin-1. Additionally, several anti-inflammatory bacteria and probiotics were increased, such as Akkermansia and Rikenellaceae, and the composition of the gut microbiota tended to be "younger". Overall, TRE showed multiple anti-aging effects, which may help humans maintain a healthy lifestyle to stay "young". Clinical Trial Registration URL: https://www.chictr.org.cn/showproj.html?proj=159876.

Benefit delayed immunosenescence by regulating CD4+T cells: A promising therapeutic target for aging-related diseases

CD4+T cells play a notable role in immune protection at different stages of life. During aging, the interaction between the body's internal and external environment and CD4+T cells results in a series of changes in the CD4+T cells pool making it involved in immunosenescence. Many studies have extensively examined the subsets and functionality of CD4+T cells within the immune system, highlighted their pivotal role in disease pathogenesis, progression, and therapeutic interventions. However, the underlying mechanism of CD4+T cells senescence and its intricate association with diseases remains to be elucidated and comprehensively understood. By summarizing the immunosenescent progress and network of CD4+T cell subsets, we reveal the crucial role of CD4+T cells in the occurrence and development of age-related diseases. Furthermore, we provide new insights and theoretical foundations for diseases targeting CD4+T cell subsets aging as a treatment focus, offering novel approaches for therapy, especially in infections, cancers, autoimmune diseases, and other diseases in the elderly.

Dysregulation of peripheral and intratumoral KLRG1+ CD8+T cells is associated with immune evasion in patients with non-small-cell lung cancer

OBJECTIVES

Killer cell lectin like receptor G1 (KLRG1) is identified as a co-inhibitory receptor for NK cells and antigen-experienced T cells. The role of KLRG1 in immune regulation in patients with non-small cell lung cancer (NSCLC) remains poorly understood.

MATERIALS AND METHODS

We measured the proportion and immune function of KLRG1+CD8+T cells derived from peripheral blood in patients with NSCLC by flow cytometry. Besides, using data from the gene expression profiles and single-cell sequencing, we explored the expression and immune role of KLRG1 in tumor tissues of patients with NSCLC. We further determined the prognostic value of KLRG1 in terms of overall survival (OS) in NSCLC patients.

RESULTS

We found that the proportion of KLRG1+CD8+T cells in peripheral blood significantly increased in patients with NSCLC as compared to those with benign pulmonary nodules and healthy donors. Peripheral KLRG1+CD8+T cell proportion was increased in elder subjects compared to that in younger ones, implying an immunosenescence phenotype. Moreover, the KLRG1+CD8+T cell levels were positively correlated with tumor size and TNM stage in the NSCLC cohort. In vitro stimulation experiments demonstrated that the KLRG1+CD8+T cells from peripheral blood expressed higher levels of Granzyme B and perforin than the KLRG1-CD8+ T cells. However, single-cell RNA sequencing data revealed that the KLRG1+CD8+ T cells were less infiltrated in tumor microenvironment and exhibited impaired cytotoxicity. The KLRG1 gene expression levels were significantly lower in tumor tissues than that in normal lung tissues, and were inversely correlated with CDH1 expression levels. Moreover, higher expression of CDH1 in tumor tissues predicted worse overall survival only in patients with KLRG1-high expression, but not in the KLRG1-low subset.

CONCLUSION

This study demonstrates that KLRG1+CD8+T cells were associated with tumor immune evasion in NSCLC and suggests KLRG1 as a potential immunotherapy target.

Quantification and Profiling of Early and Late Differentiation Stage T Cells in Mantle Cell Lymphoma Reveals Immunotherapeutic Targets in Subsets of Patients

With the aim to advance the understanding of immune regulation in MCL and to identify targetable T-cell subsets, we set out to combine image analysis and spatial omic technology focused on both early and late differentiation stages of T cells. MCL patient tissue (n = 102) was explored using image analysis and GeoMx spatial omics profiling of 69 proteins and 1812 mRNAs. Tumor cells, T helper (TH) cells and cytotoxic (TC) cells of early (CD57-) and late (CD57+) differentiation stage were analyzed. An image analysis workflow was developed based on fine-tuned Cellpose models for cell segmentation and classification. TC and CD57+ subsets of T cells were enriched in tumor-rich compared to tumor-sparse regions. Tumor-sparse regions had a higher expression of several key immune suppressive proteins, tentatively controlling T-cell expansion in regions close to the tumor. We revealed that T cells in late differentiation stages (CD57+) are enriched among MCL infiltrating T cells and are predictive of an increased expression of immune suppressive markers. CD47, IDO1 and CTLA-4 were identified as potential targets for patients with T-cell-rich MCL TIME, while GITR might be a feasible target for MCL patients with sparse T-cell infiltration. In subgroups of patients with a high degree of CD57+ TC-cell infiltration, several immune checkpoint inhibitors, including TIGIT, PD-L1 and LAG3 were increased, emphasizing the immune-suppressive features of this highly differentiated T-cell subset not previously described in MCL.

The role of KLRG1: a novel biomarker and new therapeutic target

Killer cell lectin-like receptor G1 (KLRG1) is an immune checkpoint receptor expressed predominantly in NK and T-cell subsets that downregulates the activation and proliferation of immune cells and participates in cell-mediated immune responses. Accumulating evidence has demonstrated the importance of KLRG1 as a noteworthy disease marker and therapeutic target that can influence disease onset, progression, and prognosis. Blocking KLRG1 has been shown to effectively mitigate the effects of downregulation in various mouse tumor models, including solid tumors and hematologic malignancies. However, KLRG1 inhibitors have not yet been approved for human use, and the understanding of KLRG1 expression and its mechanism of action in various diseases remains incomplete. In this review, we explore alterations in the distribution, structure, and signaling pathways of KLRG1 in immune cells and summarize its expression patterns and roles in the development and progression of autoimmune diseases, infectious diseases, and cancers. Additionally, we discuss the potential applications of KLRG1 as a tool for tumor immunotherapy.

A comprehensive analysis of the immune system in healthy Vietnamese people

Lifestyle, diet, socioeconomic status and genetics all contribute to heterogeneity in immune responses. Vietnam is plagued with a variety of health problems, but there are no available data on immune system values in the Vietnamese population. This study aimed to establish reference intervals for immune cell parameters specific to the healthy Vietnamese population by utilizing multi-color flow cytometry (MCFC). We provide a comprehensive analysis of total leukocyte count, quantitative and qualitative shifts within lymphocyte subsets, serum and cytokine and chemokine levels and functional attributes of key immune cells including B cells, T cells, natural killer (NK) cells and their respective subpopulations. By establishing these reference values for the Vietnamese population, these data contribute significantly to our understanding of the human immune system variations across diverse populations. These data will be of substantial comparative value and be instrumental in developing personalized medical approaches and optimizing diagnostic strategies for individuals based on their unique immune profiles.

A 2-week time-restricted feeding attenuates psoriasis-like lesions with reduced inflammatory cytokines and immunosenescence in mice

Psoriasis, a well-established T-cell mediated dermatosis, exhibits a robust correlation with obesity and systemic inflammation, manifesting psoriasis skin lesions and premature immunosenescence within the peripheral blood and lesion. Intermittent fasting (IF) has exhibited various beneficial effects in reducing inflammation, resisting oxidative stress and slowing ageing, as well as losing weight. A form of IF known as time-restricted feeding (TRF) restricts daily caloric intake within 4-8 h. Nonetheless, the advantageous impacts of TRF on psoriasis still require further verification. We measured the acanthosis in Imiquimod (IMQ)-induced psoriasis mice and evaluated their pathological phenotypes. Our study examined the effects of a 2-week TRF on body weight and metabolic parameters. The subsets of T cells in spleens and skin lesions were accessed by flow cytometry. Cytokines and senescence-associated genes were evaluated by immunofluorescence and RT-qPCR. RNA sequencing was conducted on skin lesions. According to our findings, a 2-week TRF attenuates psoriasis-like lesions in mice with reduced inflammatory cytokines and mitigated immunosenescence. TRF increased the counts of CD4+ Treg cells in skin lesions while reducing the counts of Th2 and Th17 cells in spleens. Furthermore, the administration of TRF resulted in a decrease in the population of CD4+ senescent T cells in both the dermis and spleens, concomitant with the expression of senescence-associated genes in spleen CD4+ T cells. The outcomes mentioned above provide valuable evidence in support of TRF for the management of psoriasis.

Therapeutic dosing and targeting efficacy of Pt-Mal-LHRH towards triple negative breast cancer

OBJECTIVE

Pt-Mal-LHRH is a newly synthesized chemotherapeutic agent that was designed to selectively target the luteinizing hormone-releasing hormone (LHRH) receptor expressed by triple negative breast cancer (TNBC). The aim of this study was to evaluate the therapeutic dosing, tumor reduction efficacy, and selective distribution of Pt-Mal-LHRH in-vivo.

METHODS AND RESULTS

LHRH tissue expression levels in-vivo were investigated using western blotting and LHRH was found to be increased in reproductive tissues (mammary, ovary, uterus). Further, Pt-Mal-LHRH was found to have increased TNBC tumor tissue platinum accumulation compared to carboplatin by inductively coupled plasma mass spectrometry analysis. The platinum family, compound carboplatin, was selected for comparison due to its similar chemical structure and molar equivalent doses were evaluated. Moreover, in-vivo distribution data indicated selective targeting of Pt-Mal-LHRH by enhanced reproductive tissue accumulation compared to carboplatin. Further, TNBC tumor growth was found to be significantly attenuated by Pt-Mal-LHRH compared to carboplatin in both the 4T1 and MDA-MB-231 tumor models. There was a significant reduction in tumor volume in the 4T1 tumor across Pt-Mal-LHRH doses (2.5-20 mg/kg/wk) and in the MDA-MB-231 tumor at the dose of 10 mg/kg/wk in models conducted by an independent contract testing laboratory.

CONCLUSION

Our data indicates Pt-Mal-LHRH is a targeting chemotherapeutic agent towards the LHRH receptor and reduces TNBC tumor growth in-vivo. This study supports drug conjugation design models using the LHRH hormone for chemotherapeutic delivery as Pt-Mal-LHRH was found to be a more selective and efficacious than carboplatin. Further examination of Pt-Mal-LHRH is warranted for its clinical use in TNBCs, along with, other reproductive cancers overexpressing the LHRH receptor.

The role of CD4+ T cells in tumor and chronic viral immune responses

Immunotherapies are mainly aimed to promote a CD8+ T cell response rather than a CD4+ T cell response as cytotoxic T lymphocytes (CTLs) can directly kill target cells. Recently, CD4+ T cells have received more attention due to their diverse roles in tumors and chronic viral infections. In antitumor and antichronic viral responses, CD4+ T cells relay help signals through dendritic cells to indirectly regulate CD8+ T cell response, interact with B cells or macrophages to indirectly modulate humoral immunity or macrophage polarization, and inhibit tumor blood vessel formation. Additionally, CD4+ T cells can also exhibit direct cytotoxicity toward target cells. However, regulatory T cells exhibit immunosuppression and CD4+ T cells become exhausted, which promote tumor progression and chronic viral persistence. Finally, we also outline immunotherapies based on CD4+ T cells, including adoptive cell transfer, vaccines, and immune checkpoint blockade. Overall, this review summarizes diverse roles of CD4+ T cells in the antitumor or protumor and chronic viral responses, and also highlights the immunotherapies based on CD4+ T cells, giving a better understanding of their roles in tumors and chronic viral infections.

COVID-19 patients display changes in lymphocyte subsets with a higher frequency of dysfunctional CD8lo T cells associated with disease severity

This work examines cellular immunity against SARS-CoV-2 in patients from Córdoba, Argentina, during two major waves characterized by different circulating viral variants and different social behavior. Using flow cytometry, we evaluated the main lymphocyte populations of peripheral blood from hospitalized patients with moderate and severe COVID-19 disease. Our results show disturbances in the cellular immune compartment, as previously reported in different cohorts worldwide. We observed an increased frequency of B cells and a significant decrease in the frequency of CD3+ T cells in COVID-19 patients compared to healthy donors (HD). We also found a reduction in Tregs, which was more pronounced in severe patients. During the first wave, the frequency of GZMB, CD107a, CD39, and PD-1-expressing conventional CD4+ T (T conv) cells was significantly higher in moderate and severe patients than in HD. During the second wave, only the GZMB+ T conv cells of moderate and severe patients increased significantly. In addition, these patients showed a decreased frequency in IL-2-producing T conv cells. Interestingly, we identified two subsets of circulating CD8+ T cells with low and high CD8 surface expression in both HD and COVID-19 patients. While the percentages of CD8hi and CD8lo T cells within the CD8+ population in HD are similar, a significant increase was observed in CD8lo T cell frequency in COVID-19 patients. CD8lo T cell populations from HD as well as from SARS-CoV-2 infected patients exhibited lower frequencies of the effector cytokine-producing cells, TNF, IL-2, and IFN-γ, than CD8hi T cells. Interestingly, the frequency of CD8lo T cells increased with disease severity, suggesting that this parameter could be a potential marker for disease progression. Indeed, the CD8hi/CD8lo index helped to significantly improve the patient's clinical stratification and disease outcome prediction. Our data support the addition of, at least, a CD8hi/CD8lo index into the panel of biomarkers commonly used in clinical labs, since its determination may be a useful tool with impact on the therapeutic management of the patients.

CD39+ conventional CD4+ T cells with exhaustion traits and cytotoxic potential infiltrate tumors and expand upon CTLA-4 blockade

Conventional CD4+ T (Tconv) lymphocytes play important roles in tumor immunity; however, their contribution to tumor elimination remains poorly understood. Here, we describe a subset of tumor-infiltrating Tconv cells characterized by the expression of CD39. In several mouse cancer models, we observed that CD39+ Tconv cells accumulated in tumors but were absent in lymphoid organs. Compared to tumor CD39- counterparts, CD39+ Tconv cells exhibited a cytotoxic and exhausted signature at the transcriptomic level, confirmed by high protein expression of inhibitory receptors and transcription factors related to the exhaustion. Additionally, CD39+ Tconv cells showed increased production of IFNγ , granzyme B, perforin and CD107a expression, but reduced production of TNF. Around 55% of OVA-specific Tconv from B16-OVA tumor-bearing mice, expressed CD39. In vivo CTLA-4 blockade induced the expansion of tumor CD39+ Tconv cells, which maintained their cytotoxic and exhausted features. In breast cancer patients, CD39+ Tconv cells were found in tumors and in metastatic lymph nodes but were less frequent in adjacent non-tumoral mammary tissue and not detected in non-metastatic lymph nodes and blood. Human tumor CD39+ Tconv cells constituted a heterogeneous cell population with features of exhaustion, high expression of inhibitory receptors and CD107a. We found that high CD4 and ENTPD1 (CD39) gene expression in human tumor tissues correlated with a higher overall survival rate in breast cancer patients. Our results identify CD39 as a biomarker of Tconv cells, with characteristics of both exhaustion and cytotoxic potential, and indicate CD39+ Tconv cells as players within the immune response against tumors.

Tofacitinib treatment of rheumatoid arthritis increases senescent T cell frequency in patients and limits T cell function in vitro

Unraveling the immune signatures in rheumatoid arthritis (RA) patients receiving various treatment regimens can aid in comprehending the immune mechanisms' role in treatment efficacy and side effects. Given the critical role of cellular immunity in RA pathogenesis, we sought to identify T-cell profiles characterizing RA patients under specific treatments. We compared 75 immunophenotypic and biochemical variables in healthy donors (HD) and RA patients, including those receiving different treatments as well as treatment-free patients. Additionally, we conducted in vitro experiments to evaluate the direct effect of tofacitinib on purified naïve and memory CD4+ and CD8+ T cells. Multivariate analysis revealed that tofacitinib-treated patients segregated from HD at the expense of T-cell activation, differentiation, and effector function-related variables. Additionally, tofacitinib led to an accumulation of peripheral senescent memory CD4+ and CD8+ T cells. In vitro, tofacitinib impaired the activation, proliferation, and effector molecules expression and triggered senescence pathways in T-cell subsets upon TCR-engagement, with the most significant impact on memory CD8+ T cells. Our findings suggest that tofacitinib may activate immunosenescence pathways while simultaneously inhibiting effector functions in T cells, both effects likely contributing to the high clinical success and reported side effects of this JAK inhibitor in RA.

Senescent T cells: Beneficial and detrimental roles

As the thymus involutes during aging, the T-cell pool has to be maintained by the periodic expansion of preexisting T cells during adulthood. A conundrum is that repeated episodes of activation and proliferation drive the differentiation of T cells toward replicative senescence, due to telomere erosion. This review discusses mechanisms that regulate the end-stage differentiation (senescence) of T cells. Although these cells, within both CD4 and CD8 compartments, lose proliferative activity after antigen-specific challenge, they acquire innate-like immune function. While this may confer broad immune protection during aging, these senescent T cells may also cause immunopathology, especially in the context of excessive inflammation in tissue microenvironments.

Extremely Differentiated T Cell Subsets Contribute to Tissue Deterioration During Aging

There is a dramatic remodeling of the T cell compartment during aging. The most notorious changes are the reduction of the naive T cell pool and the accumulation of memory-like T cells. Memory-like T cells in older people acquire a phenotype of terminally differentiated cells, lose the expression of costimulatory molecules, and acquire properties of senescent cells. In this review, we focus on the different subsets of age-associated T cells that accumulate during aging. These subsets include extremely cytotoxic T cells with natural killer properties, exhausted T cells with altered cytokine production, and regulatory T cells that gain proinflammatory features. Importantly, all of these subsets lose their lymph node homing capacity and migrate preferentially to nonlymphoid tissues, where they contribute to tissue deterioration and inflammaging.

Exploring tumor-normal cross-talk with TranNet: role of the environment in tumor progression

There is a growing awareness that tumor-adjacent normal tissues used as control samples in cancer studies do not represent fully healthy tissues. Instead, they are intermediates between healthy tissues and tumors. The factors that contribute to the deviation of such control samples from healthy state include exposure to the tumor-promoting factors, tumor-related immune response, and other aspects of tumor microenvironment. Characterizing the relation between gene expression of tumor-adjacent control samples and tumors is fundamental for understanding roles of microenvironment in tumor initiation and progression, as well as for identification of diagnostic and prognostic biomarkers for cancers. To address the demand, we developed and validated TranNet, a computational approach that utilizes gene expression in matched control and tumor samples to study the relation between their gene expression profiles. TranNet infers a sparse weighted bipartite graph from gene expression profiles of matched control samples to tumors. The results allow us to identify predictors (potential regulators) of this transition. To our knowledge, TranNet is the first computational method to infer such regulation. We applied TranNet to the data of several cancer types and their matched control samples from The Cancer Genome Atlas (TCGA). Many predictors identified by TranNet are genes associated with regulation by the tumor microenvironment as they are enriched in G-protein coupled receptor signaling, cell-to-cell communication, immune processes, and cell adhesion. Correspondingly, targets of inferred predictors are enriched in pathways related to tissue remodelling (including the epithelial-mesenchymal Transition (EMT)), immune response, and cell proliferation. This implies that the predictors are markers and potential stromal facilitators of tumor progression. Our results provide new insights for the relationships between tumor adjacent control sample, tumor and the tumor environment. Moreover, the set of predictors identified by TranNet will provide a valuable resource for future investigations. The TranNet method was implemented in python, source codes and the data sets used for and generated during this study are available at the Github site https://github.com/ncbi/TranNet .

Cellular Senescence as a Brake or Accelerator for Oncogenic Transformation and Role in Lymphatic Metastasis

Cellular senescence-the irreversible cell cycle arrest driven by a variety of mechanisms and, more specifically, the senescence-associated secretory phenotype (SASP)-is an important area of research in the context of different age-related diseases, such as cardiovascular disease and cancer. SASP factors play both beneficial and detrimental roles in age-related disease progression depending on the source of the SASPs, the target cells, and the microenvironment. The impact of senescence and the SASP on different cell types, the immune system, and the vascular system has been widely discussed. However, the impact of replicative or stress-induced senescence on lymphatic biology and pathological lymphangiogenesis remains underexplored. The lymphatic system plays a crucial role in the maintenance of body fluid homeostasis and immune surveillance. The perturbation of lymphatic function can hamper normal physiological function. Natural aging or stress-induced premature aging influences the lymphatic vessel structure and function, which significantly affect the role of lymphatics in tumor dissemination and metastasis. In this review, we focus on the role of senescence on lymphatic pathobiology, its impact on cancer, and potential therapeutic interventions to manipulate the aged or senescent lymphatic system for disease management.

Immunohistochemical Phenotype of T Cells Invading Muscle in Inclusion Body Myositis

Inclusion body myositis (IBM) is an inflammatory myopathy of aged people with poor response to therapy. To characterize muscle-invading inflammatory cells, we performed immunohistochemical and ultrastructural studies on muscle biopsies from 10 patients with IBM with durations of illness from 3 to 84 months. At the surface of muscle fibers, 79% and 48% of CD8+ cells were positive for killer cell lectin-like receptor subfamily G, member 1 (KLRG1) and CD57, respectively. CD8+KLRG1+ cells are highly differentiated cytotoxic cells. On an average, 27% of CD8-CD57+KLRG1+ cells at the surface were CD4+. Proportions of CD28+ cells among KLRG1+ cells showed a negative correlation with duration of illness (r = -0.68). These changes indicated progressive differentiation of CD8+ T cells. Moreover, PD-1 expression on CD57+ and CD8+ cells increased early, then fluctuated, and reincreased in later stages. PD ligand-1 (PD-L1) and PD-L2 were expressed on adjacent cells including muscle fibers. T cell large granular lymphocytes (LGLs) are potent effector cells and cells with ultrastructure indistinguishable from LGLs were seen in the sarcoplasm along with lymphocytes undergoing degeneration. Together, along the course of IBM, some inflammatory cells retained the potential for cytotoxicity whereas others indicated suppression by exhaustion, senescence, or through the PD-1 pathway.

Ascitic Senescent T Cells Are Linked to Chemoresistance in Patients With Advanced High-Grade Serous Ovarian Cancer

Senescent T cells are reported to be increased in patients with cancer and are poor prognostic indicators. However, the distribution of senescent T cells and their correlation with clinical features in high-grade serous ovarian cancer (HGSOC) is unknown. We detected the percentage of senescent T cells in the peripheral blood and ascites of patients with advanced HGSOC (n = 86) at diagnosis by flow cytometry. Compared with healthy donors, patients with HGSOC exhibited an accumulation of CD28−CD57+ (Tsen) CD8+ T cells in the peripheral blood and ascites. The frequency of Tsen CD8+ T cells in the peripheral blood was positively correlated with age and pretreatment serum CA125 and increased in patients with large volume ascites, whereas the frequency of Tsen CD8+ T cells in ascites was elevated in patients with lymph node metastasis. Patients with Tsen-high in ascites (>19.92%), but not in the peripheral blood, were more likely to be resistant to chemotherapy and had shorter progression-free survival. Tsen CD8+ T cells exhibited common senescence features including increased SA-β-gal activity, declines in proliferation, loss of CD27 and gain of KLRG-1, and the production of cytokines. In ascites, the percentage of Tsen CD8+ T cells was positively correlated with levels of interleukin-10 and granzyme B. This study suggests the potential of ascitic Tsen CD8+ T cells at diagnosis as a prognostic biomarker in HGSOC.

Assessment of cell cycle regulators in human peripheral blood cells as markers of cellular senescence

Cellular senescence has gained increasing interest during recent years, particularly due to causal involvement in the aging process corroborated by multiple experimental findings. Indeed, cellular senescence considered to be one of the hallmarks of aging, is defined as a stable growth arrest predominantly mediated by cell cycle regulators p53, p21 and p16. Senescent cells have frequently been studied in the peripheral blood of humans due to its accessibility. This review summarizes ex vivo studies describing cell cycle regulators as markers of senescence in human peripheral blood cells, along with detection methodologies and associative studies examining demographic and clinical characteristics. The utility of techniques such as the quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), microarray, RNA sequencing and nCounter technologies for detection at the transcriptional level, along with Western blotting, enzyme-linked immunosorbent assay and flow cytometry at the translational level, will be brought up at salient points throughout this review. Notably, housekeeping genes or proteins serving as controls such as GAPDH and β-Actin, were found not to be stably expressed in some contexts. As such, optimization and validation of such genes during experimental design were recommended. In addition, the expression of cell cycle regulators was found to vary not only between different types of blood cells such as T cells and B cells but also between stages of cellular differentiation such as naïve T cells and highly differentiated T cells. On the other hand, the associations of the presence of cell cycle regulators with demographics (age, gender, ethnicity, and socioeconomic status), clinical characteristics (body mass index, specific diseases, disease-related parameters) and lifestyle vary in groups of participants. One envisions that increased understanding and insights into the assessment of cell cycle regulators as markers of senescence in human peripheral blood cells will help inform prognostication and clinical intervention in elderly individuals.

Cytokine-Induced Senescence in the Tumor Microenvironment and Its Effects on Anti-Tumor Immune Responses

In contrast to surgical excision, chemotherapy or radiation therapy, immune checkpoint blockade therapies primarily influence cells in the tumor microenvironment, especially the tumor-associated lymphocytes and antigen-presenting cells. Besides complete remission of tumor lesions, in some patients, early tumor regression is followed by a consolidation phase where residing tumors remain dormant. Whereas the cytotoxic mechanisms of the regression phase (i.e., apoptosis, necrosis, necroptosis, and immune cell-mediated cell death) have been extensively described, the mechanisms underlying the dormant state are still a matter of debate. Here, we propose immune-mediated induction of senescence in cancers as one important player. Senescence can be achieved by tumor-associated antigen-specific T helper 1 cells, cytokines or antibodies targeting immune checkpoints. This concept differs from cytotoxic treatment, which often targets the genetic makeup of cancer cells. The immune system's ability to establish "defensive walls" around tumors also places the tumor microenvironment into the fight against cancer. Those "defensive walls" isolate the tumor cells instead of increasing the selective pressure. They also keep the tumor cells in a non-proliferating state, thereby correcting the derailed tissue homeostasis. In conclusion, strengthening the senescence surveillance of tumors by the immune cells of the microenvironment is a future goal to dampen this life-threatening disease.