Cellular senescence and the host immune system in aging and age-related disorders

Genetically engineered CD276-anchoring biomimetic nanovesicles target senescent escaped tumor cells to overcome chemoresistant and immunosuppressive breast cancer

Chemotherapy-induced cellular senescence leads to an increased proportion of cancer stem cells (CSCs) in breast cancer (BC), contributing to recurrence and metastasis, while effective means to clear them are currently lacking. Herein, we aim to develop new approaches for selectively killing senescent-escape CSCs. High CD276 (95.60%) expression in multidrug-resistant BC cells, facilitates immune evasion by low-immunogenic senescent escape CSCs. CALD1, upregulated in ADR-resistant BC, promoting senescent-escape of CSCs with an anti-apoptosis state and upregulating CD276, PD-L1 to promote chemoresistance and immune escape. We have developed a controlled-released thermosensitive hydrogel containing pH- responsive anti-CD276 scFV engineered biomimetic nanovesicles to overcome BC in primary, recurrent, metastatic and abscopal humanized mice models. Nanovesicles coated anti-CD276 scFV selectively fuses with cell membrane of senescent-escape CSCs, then sequentially delivers siCALD1 and ADR due to pH-responsive MnP shell. siCALD1 together with ADR effectively induce apoptosis of CSCs, decrease expression of CD276 and PD-L1, and upregulate MHC I combined with Mn2+ to overcome chemoresistance and promote CD8+T cells infiltration. This combined therapeutic approach reveals insights into immune surveillance evasion by senescent-escape CSCs, offering a promising strategy to immunotherapy effectiveness in cancer therapy.

Nanoparticles for the Delivery of Pro-regenerative Cardiac Progenitor Secretory Proteins Targeting Cellular Senescence and Vasculogenesis

Contemporary therapies following heart failure center on regenerative approaches to account for the loss of cardiomyocytes and limited regenerative capacity of the adult heart. While the delivery of cardiac progenitor cells has been shown to improve cardiac function and repair following injury, recent evidence has suggested that their paracrine effects (or secretome) provides a significant contribution towards modulating regeneration, rather than the progenitor cells intrinsically. The direct delivery of secretory biomolecules, however, remains a challenge due to their lack of stability and tissue retention, limiting their prolonged therapeutic efficacy. We hypothesized that polyurethane-based nanoparticles with heteropolar-hydrophobic-ionic chemistry (DPHI-NPs) could enable the delivery of a subset of pro-regenerative cardiac progenitor cell proteins [bone morphogenetic protein-4 (BMP-4) and angiotensin 1-7 (Ang1-7)] to promote biological pathways conducive to repair processes such as antisenescence (through the quantification of β-galactosidase and interleukin-6) and vasculogenesis (through the formation of endothelial tubes), demonstrated in vitro with human cardiac fibroblasts (hCFs) and human microvascular endothelial cells (hMECs), respectively. DPHI-NPs with a diameter of 190 ± 2 nm (polydispersity index < 0.2) and a zeta potential of -40 ± 1 mV were generated using an emulsion inversion technique and loaded with both therapeutic proteins (BMP-4 and Ang1-7) by optimizing surface charge, loading solution concentration, coating duration, and coating efficiency. Senescence-induced hCFs treated with functionalized DPHI-NPs were found to exhibit a significant reduction in expressed β-galactosidase and IL-6 (p < 0.05). Additionally, hMECs treated with NPBMP-4 were found to display enhanced vasculogenesis compared to control culture conditions alone (p < 0.05). The development of a DPHI-NP vector for the delivery of pro-regenerative secretome biomolecules may present an effective translatable strategy to improve their therapeutic efficacy with respect to cell function.

A ganglioside-based immune checkpoint enables senescent cells to evade immunosurveillance during aging

Although senescent cells can be eliminated by the immune system, they tend to accumulate with age in various tissues. Here we show that senescent cells can evade immune clearance by natural killer (NK) cells by upregulating the expression of the disialylated ganglioside GD3 at their surface. The increased level of GD3 expression on senescent cells that naturally occurs upon aging in liver, lung, kidney or bones leads to a strong suppression of NK-cell-mediated immunosurveillance. In mice, we found that targeting GD3+ senescent cells with anti-GD3 immunotherapy attenuated the development of experimentally induced or age-related lung and liver fibrosis and age-related bone remodeling. These results demonstrate that GD3 upregulation confers immune privilege to senescent cells. We propose that GD3 acts as a senescence immune checkpoint (SIC) that allows senescent cells to escape immunosurveillance and to trigger immune anergy during aging.

Endothelial Cell Senescence Effect on the Blood-Brain Barrier in Stroke and Cognitive Impairment

Age is an important risk factor of stroke, cognitive decline, and dementia. Senescent endothelial cells (ECs) accumulate with advancing age through exposure to cellular stress, such as that exerted by hypertension and diabetes. These senescent ECs have altered characteristics, such as altered tight junction proteins, use of a more indiscriminate transcellular transport system, increased inflammation, and increased immune cell interactions. ECs are the main component of the blood-brain barrier (BBB), separating the brain from systemic circulation. As senescent ECs accumulate in the BBB, their altered functioning results in the disruption of the barrier. They have inadequate barrier-forming properties, disrupted extracellular matrix, and increased transcytosis, resulting in an overly permeable barrier. This disruption of the BBB can have important effects in stroke and cognitive impairment, as presented in this review. Besides increasing the permeability of the BBB, senescent ECs can also impair angiogenesis and vascular remodeling, which in ischemic stroke may increase risk of hemorrhagic transformation and worsen outcomes. Senescent ECs may also contribute to microvascular dysfunction, with disruption of cerebral perfusion and autoregulation. These may contribute to vascular cognitive impairment along with increased permeability. With an aging population, there is growing interest in targeting senescence. Several ongoing trials have been evaluating whether senolytics can slow aging, improve vascular health, and reduce the risk of stroke and cognitive decline.

PD-L1: From cancer immunotherapy to therapeutic implications in multiple disorders

The PD-L1/PD-1 signaling pathway is the gold standard for cancer immunotherapy. Therapeutic antibodies targeting PD-1, such as nivolumab (Opdivo) and pembrolizumab (Keytruda), and PD-L1, including atezolizumab (Tecentriq), durvalumab (Imfinzi), and avelumab (Bavencio) have received Food and Drug Administration approval and are currently being used to treat various cancers. Traditionally, PD-L1 is known as an immune checkpoint protein that binds to the PD-1 receptor on its surface to inhibit the activity of T cells, which are the primary effector cells in antitumor immunity. However, it also plays a role in cancer progression, which goes beyond traditional understanding. Here, we highlight the multifaceted mechanisms of action of PD-L1 in cancer cell proliferation, transcriptional regulation, and systemic immune suppression. Moreover, we consider the potential role of PD-L1 in the development and pathogenesis of diseases other than cancer, explore PD-L1-focused therapeutic approaches for these diseases, and assess their clinical relevance. Through this review, we hope to provide deeper insights into the PD-L1/PD-1 signaling pathway and present a broad perspective on potential therapeutic approaches for cancer and other diseases.

Senescence and tissue fibrosis: opportunities for therapeutic targeting

Cellular senescence is a key hallmark of aging. It has now emerged as a key mediator in normal tissue turnover and is associated with a variety of age-related diseases, including organ-specific fibrosis and systemic sclerosis (SSc). This review discusses the recent evidence of the role of senescence in tissue fibrosis, with an emphasis on SSc, a systemic autoimmune rheumatic disease. We discuss the physiological role of these cells, their role in fibrosis, and that targeting these cells specifically could be a new therapeutic avenue in fibrotic disease. We argue that targeting senescent cells, with senolytics or senomorphs, is a viable therapeutic target in fibrotic diseases which remain largely intractable.

Therapeutic targeting of senescent cells in the CNS

Senescent cells accumulate throughout the body with advanced age, diseases and chronic conditions. They negatively impact health and function of multiple systems, including the central nervous system (CNS). Therapies that target senescent cells, broadly referred to as senotherapeutics, recently emerged as potentially important treatment strategies for the CNS. Promising therapeutic approaches involve clearing senescent cells by disarming their pro-survival pathways with 'senolytics'; or dampening their toxic senescence-associated secretory phenotype (SASP) using 'senomorphics'. Following the pioneering discovery of first-generation senolytics dasatinib and quercetin, dozens of additional therapies have been identified, and several promising targets are under investigation. Although potentially transformative, senotherapies are still in early stages and require thorough testing to ensure reliable target engagement, specificity, safety and efficacy. The limited brain penetrance and potential toxic side effects of CNS-acting senotherapeutics pose challenges for drug development and translation to the clinic. This Review assesses the potential impact of senotherapeutics for neurological conditions by summarizing preclinical evidence, innovative methods for target and biomarker identification, academic and industry drug development pipelines and progress in clinical trials.

PD-1 immunology in the kidneys: a growing relationship

In recent years, knowledge regarding immune regulation has expanded rapidly, and major advancements have been made in immunotherapy for immune-associated disorders, particularly cancer. The programmed cell death 1 (PD-1) pathway is a cornerstone in immune regulation. It comprises PD-1 and its ligands mediating immune tolerance mechanisms and immune homeostasis. Accumulating evidence demonstrates that the PD-1 axis has a crucial immunosuppressive role in the tumor microenvironment and autoimmune diseases. PD-1 receptors and ligands on immune cells and renal parenchymal cells aid in maintaining immunological homeostasis in the kidneys. Here, we present a comprehensive review of PD-1 immunology in various kidney disorders, including renal cell carcinoma, glomerulonephritis, kidney transplantation, renal aging, and renal immune-related adverse events secondary to PD-1 immunotherapy.

Exploring the Interplay between Cellular Senescence, Immunity, and Fibrosing Interstitial Lung Diseases: Challenges and Opportunities

Fibrosing interstitial lung diseases (ILDs) are characterized by the gradual and irreversible accumulation of scar tissue in the lung parenchyma. The role of the immune response in the pathogenesis of pulmonary fibrosis remains unclear. In recent years, substantial advancements have been made in our comprehension of the pathobiology driving fibrosing ILDs, particularly concerning various age-related cellular disturbances and immune mechanisms believed to contribute to an inadequate response to stress and increased susceptibility to lung fibrosis. Emerging studies emphasize cellular senescence as a key mechanism implicated in the pathobiology of age-related diseases, including pulmonary fibrosis. Cellular senescence, marked by antagonistic pleiotropy, and the complex interplay with immunity, are pivotal in comprehending many aspects of lung fibrosis. Here, we review progress in novel concepts in cellular senescence, its association with the dysregulation of the immune response, and the evidence underlining its detrimental role in fibrosing ILDs.

Lack of Clinically Significant Relationships of Age or Body Mass Index with Merkel Cell Carcinoma Immunotherapy Outcomes

Merkel cell carcinoma (MCC) is a rare and aggressive skin cancer with a high risk of metastasis. The development of anti-PD-1/PD-L1 immunotherapy has improved outcomes for advanced MCC, yet about 50% of such patients do not achieve durable responses. This study analyzed the effects of age and body mass index (BMI) on immunotherapy response in 183 advanced MCC patients from a single-center longitudinal database. Using Fine-Gray or Cox regression models, treatment response, progression-free survival (PFS), MCC-specific survival, and overall survival (OS) were evaluated. Age showed a significant non-linear relationship with treatment response (p = 0.04), with patients much older or younger than 70 years less likely to respond. However, age was not significantly associated with PFS (p = 0.21), MCC-specific survival (p = 0.72), or OS (p = 0.36). Similarly, BMI was not significantly correlated with treatment response (p = 0.41), PFS (p = 0.52), MCC-specific survival (p = 0.78), or OS (p = 0.71). Unlike previous studies suggesting that obesity and advanced age improve outcomes in other cancers, these associations were not observed in MCC. These findings suggest that age and BMI should not influence eligibility for immunotherapy in MCC patients, emphasizing the importance of unbiased patient selection for this treatment.

Chemokine receptor 7 contributes to T- and B-cell filtering in ageing bladder, cystitis and bladder cancer

BACKGROUND

Research has suggested significant correlations among ageing, immune microenvironment, inflammation and tumours. However, the relationships among ageing, immune microenvironment, cystitis and bladder urothelial carcinoma (BLCA) in the bladder have rarely been reported.

METHODS

Bladder single-cell and transcriptomic data from young and old mice were used for immune landscape analysis. Transcriptome, single-cell and The Cancer Genome Atlas Program datasets of BLCA and interstitial cystitis/bladder pain syndrome (IC/BPS) were used to analyse immune cell infiltration and molecular expression. Bladder tissues from mice, IC/BPS and BLCA were collected to validate the results.

RESULTS

Eight types of immune cells (macrophages, B-cells, dendritic cells, T-cells, monocytes, natural killer cells, γδ T-cells and ILC2) were identified in the bladder of mice. Aged mice bladder tissues had a significantly higher number of T-cells, γδ T-cells, ILC2 and B-cells than those in the young group (P < 0.05). Three types of T-cells (NK T-cells, γδ T-cells and naïve T-cells) and three types of B-cells (follicular B-cells, plasma and memory B-cells) were identified in aged mice bladder. Chemokine receptor 7 (CCR7) is highly expressed in aged bladder, IC/BPS and BLCA (P < 0.05). CCR7 is likely to be involved in T- and B-cell infiltration in aged bladder, IC/BPS and BLCA. Interestingly, the high CCR7 expression on BLCA cell membranes was a prognostic protective factor.

CONCLUSIONS

In this study, we characterised the expression profiles of immune cells in bladder tissues of aged and young mice and demonstrated that CCR7-mediated T- and B-cell filtration contributes to the development of bladder ageing, IC/BPS and BLCA.

Gene expression profiling in elderly patients with familial hypercholesterolemia with and without coronary heart disease

BACKGROUND AND AIMS

Elderly familial hypercholesterolemia (FH) patients are at high risk of coronary heart disease (CHD) due to high cholesterol burden and late onset of effective cholesterol-lowering therapies. A subset of these individuals remains free from any CHD event, indicating the potential presence of protective factors. Identifying possible cardioprotective gene expression profiles could contribute to our understanding of CHD prevention and future preventive treatment. Therefore, this study aimed to investigate gene expression profiles in elderly event-free FH patients.

METHODS

Expression of 773 genes was analysed using the Nanostring Metabolic Pathways Panel, in peripheral blood mononuclear cells (PBMCs) from FH patients ≥65 years without CHD (FH event-free, n = 44) and with CHD (FH CHD, n = 39), and from healthy controls ≥70 years (n = 39).

RESULTS

None of the genes were differentially expressed between FH patients with and without CHD after adjusting for multiple testing. However, at nominal p < 0.05, we found 36 (5%) differentially expressed genes (DEGs) between the two FH groups, mainly related to lipid metabolism (e.g. higher expression of ABCA1 and ABCG1 in FH event-free) and immune responses (e.g. lower expression of STAT1 and STAT3 in FH event-free). When comparing FH patients to controls, the event-free group had fewer DEGs than the CHD group; 147 (19%) and 219 (28%) DEGs, respectively.

CONCLUSIONS

Elderly event-free FH patients displayed a different PBMC gene expression profile compared to FH patients with CHD. Differences in gene expression compared to healthy controls were more pronounced in the CHD group, indicating a less atherogenic gene expression profile in event-free individuals. Overall, identification of cardioprotective factors could lead to future therapeutic targets.

Aging like fine wine: Mischievous microbes and other factors influencing senescence

In this issue, a special section is dedicated to the factors affecting senescence. It examines the interplay between immunosenescence and chronic kidney disease, probes into Peto's paradox, and explores how epigenetic switches can potentially mitigate senescence and inflammation. Additionally, insights are offered on understanding a specific Ras mechanism in yeast for potential therapeutic interventions against cancer and for longevity. Furthermore, the remarkable endurance of last year's Nobel Prize winner in Physiology or Medicine is also highlighted. Moreover, the discovery of potential biomarkers for hepatocellular carcinoma, the link between osteoarthritis and the circadian clock, and the multifaceted role of DNAJA3 in B cell lifecycle are discussed. Further, study findings shed light on the influence of extracellular matrix molecules on cleft palate formation, the renal protective effects of combination therapy in diabetic kidney disease, and novel approaches to detect developmental dysplasia of the hip. Finally, a correspondence delves into the role of autonomic regulation in cognitive decline.

Aging-related biomarker discovery in the era of immune checkpoint inhibitors for cancer patients

Older patients with cancer, particularly those over 75 years of age, often experience poorer clinical outcomes compared to younger patients. This can be attributed to age-related comorbidities, weakened immune function, and reduced tolerance to treatment-related adverse effects. In the immune checkpoint inhibitors (ICI) era, age has emerged as an influential factor impacting the discovery of predictive biomarkers for ICI treatment. These age-linked changes in the immune system can influence the composition and functionality of tumor-infiltrating immune cells (TIICs) that play a crucial role in the cancer response. Older patients may have lower levels of TIICs infiltration due to age-related immune senescence particularly T cell function, which can limit the effectivity of cancer immunotherapies. Furthermore, age-related immune dysregulation increases the exhaustion of immune cells, characterized by the dysregulation of ICI-related biomarkers and a dampened response to ICI. Our review aims to provide a comprehensive understanding of the mechanisms that contribute to the impact of age on ICI-related biomarkers and ICI response. Understanding these mechanisms will facilitate the development of treatment approaches tailored to elderly individuals with cancer.

Involvement of regulated cell deaths in aging and age-related pathologies

Aging is a pathophysiological process that causes a gradual and permanent reduction in all biological system functions. The phenomenon is caused by the accumulation of endogenous and exogenous damage as a result of several stressors, resulting in significantly increased risks of various age-related diseases such as neurodegenerative diseases, cardiovascular diseases, metabolic diseases, musculoskeletal diseases, and immune system diseases. In addition, aging appears to be connected with mis-regulation of programmed cell death (PCD), which is required for regular cell turnover in many tissues sustained by cell division. According to the recent nomenclature, PCDs are physiological forms of regulated cell death (RCD) useful for normal tissue development and turnover. To some extent, some cell types are connected with a decrease in RCD throughout aging, whereas others are related with an increase in RCD. Perhaps the widespread decline in RCD markers with age is due to a slowdown of the normal rate of homeostatic cell turnover in various adult tissues. As a result, proper RCD regulation requires a careful balance of many pro-RCD and anti-RCD components, which may render cell death signaling pathways more sensitive to maladaptive signals during aging. Current research, on the other hand, tries to further dive into the pathophysiology of aging in order to develop therapies that improve health and longevity. In this scenario, RCD handling might be a helpful strategy for human health since it could reduce the occurrence and development of age-related disorders, promoting healthy aging and lifespan. In this review we propose a general overview of the most recent RCD mechanisms and their connection with the pathophysiology of aging in order to promote targeted therapeutic strategies.

Targeting Cellular Senescence in Aging and Age-Related Diseases: Challenges, Considerations, and the Emerging Role of Senolytic and Senomorphic Therapies

Cellular senescence is characterized by the permanent arrest of cell proliferation and is a response to endogenous and exogenous stress. The continuous accumulation of senescent cells (SnCs) in the body leads to the development of aging and age-related diseases (such as neurodegenerative diseases, cancer, metabolic diseases, cardiovascular diseases, and osteoarthritis). In the face of the growing challenge of aging and age-related diseases, several compounds have received widespread attention for their potential to target SnCs. As a result, senolytics (compounds that selectively eliminate SnCs) and senomorphics (compounds that alter intercellular communication and modulate the behavior of SnCs) have become hot research topics in the field of anti-aging. In addition, strategies such as combination therapies and immune-based approaches have also made significant progress in the field of anti-aging therapy. In this article, we discuss the latest research on anti-aging targeting SnCs and gain a deeper understanding of the mechanism of action and impact of different anti-aging strategies on aging and age-related diseases, with the aim of providing more effective references and therapeutic ideas for clinical anti-aging treatment in the face of the ever-grave challenges of aging and age-related diseases.

Senolytics: from pharmacological inhibitors to immunotherapies, a promising future for patients' treatment

The involvement of cellular senescence in the initiation and propagation of diseases is clearly characterized, making the elimination of senescent cells essential to treat age-related diseases. The development of senolytic drugs demonstrated that targeting these cells limits the deterioration of patients' condition, by inducing apoptosis. Nevertheless, the first generations of senolytics which has been developed displayed their activities through specific mechanisms and demonstrated several limitations during clinical development. However, the rational to eliminate senescent cells remains evident, with the necessity to develop specific therapies in a context of diseases and tissues. The evolutions in the field of drug discovery open the way to a new generation of senolytic therapies, such as immunological approaches (CAR-T cells, Antibody-Drug Conjugated or vaccines), which require preliminary steps of research to identify markers specifically expressed on senescent cells, demonstrating promising specific effects. Currently, the preclinical development of these strategies appears more challenging to avoid strong side effects, but the expected results are commensurate with patients' hopes for treatments. In this review, we highlight the fact that the classical senolytic approach based on drug repurposing display limited efficacy and probably reached its limits in term of clinical development. The recent development of more complex therapies and the extension of interest in the domain of senescence in different fields of research allow to extend the possibility to discover powerful therapies. The future of age-related diseases treatment is linked to the development of new approaches based on cell therapy or immunotherapy to offer the best treatment for patients.

NAD metabolism: Role in senescence regulation and aging

The geroscience hypothesis proposes that addressing the biology of aging could directly prevent the onset or mitigate the severity of multiple chronic diseases. Understanding the interplay between key aspects of the biological hallmarks of aging is essential in delivering the promises of the geroscience hypothesis. Notably, the nucleotide nicotinamide adenine dinucleotide (NAD) interfaces with several biological hallmarks of aging, including cellular senescence, and changes in NAD metabolism have been shown to be involved in the aging process. The relationship between NAD metabolism and cellular senescence appears to be complex. On the one hand, the accumulation of DNA damage and mitochondrial dysfunction induced by low NAD+ can promote the development of senescence. On the other hand, the low NAD+ state that occurs during aging may inhibit SASP development as this secretory phenotype and the development of cellular senescence are both highly metabolically demanding. However, to date, the impact of NAD+ metabolism on the progression of the cellular senescence phenotype has not been fully characterized. Therefore, to explore the implications of NAD metabolism and NAD replacement therapies, it is essential to consider their interactions with other hallmarks of aging, including cellular senescence. We propose that a comprehensive understanding of the interplay between NAD boosting strategies and senolytic agents is necessary to advance the field.

Immune system rejuvenation—approaches and real achievements

Interest in the mechanisms of aging of the immune system has not faded over the past 100 years, and it is caused by the immune-mediated development of age-related pathology, including autoimmune organ damage, reduced vaccination efficiency, atherosclerosis, the development of cardiovascular pathology, etc. In contrast to many other organs and systems, the immune system aging begins at an early age and has more pronounced changes that lead to the development of secondary pathology, which significantly affects life expectancy. But an effective strategy to restore immune function has not been developed yet. During this time, the mechanisms of age-related dysfunction of organs and cells of both the adaptive and innate immune systems were studied in detail—thymus involution, a decrease in the potential of hematopoietic stem cells, impaired differentiation and functions of immunocompetent cells, as well as the ways of their interaction. Numerous potential therapeutic targets have been identified and various approaches have been used to implement such therapeutic interventions. The review is devoted to replacement therapy using transplantation of hematopoietic stem cells (HSCs) and young lymphoid cells and tissues, cellular and systemic factor exchange in heterochronic parabiosis, and some other widely used life extension approaches. It has been proven that cell therapy using young cells to rejuvenate the old immune system, unfortunately, often turns out to be ineffective because it does not eliminate the root cause of age-related changes. The phenomenon of inflamm-aging that develops with age can significantly affect both the aging of the organism in general and the functioning of immunocompetent cells in particular. Therefore, the most promising direction in the restoration of immune functions during aging is systemic approaches that have a complex effect on the organism as a whole and can slow down the aging process.

"How sad it is! I shall grow old, and horrible, and dreadful" - The ups and downs of cell senescence

This issue of the Biomedical Journal contains a special section about cell senescence. The reader gets an insight into the crosstalk between immune system and senescent cells, into an approach to fight aging by tweaking macronutrient intake, and also learns about the connection that does (not) exist between body mass and cancer risk. Further articles in the current issue give details about the effect of Damask rose on PCOS, illustrate the issues gender bias may exert in research studies, go into a joint drug approach in ischemia-reperfusion injury, and a promising tool to diagnose Parkinsonian disorders. Two articles dive into challenges related to obstructive sleep apnea, another article explores the benefits a composite mixture may have for improving bone cement material, with lastly a research team presenting a modified procedure to managing involutional lower eyelid entropion in individuals of Asian descent. Finally, BMJ issue 46-3 is complemented with a correspondence about mpox spreading from endemic areas to other parts of the world.

Cancer-associated fibroblasts in radiotherapy: Bystanders or protagonists?

BACKGROUND

The primary goal of radiotherapy (RT) is to induce cellular damage on malignant cells; however, it is becoming increasingly recognized the important role played by the tumor microenvironment (TME) in therapy outcomes. Therapeutic irradiation of tumor lesions provokes profound cellular and biological reconfigurations within the TME that ultimately may influence the fate of the therapy.

MAIN CONTENT

Cancer-associated fibroblasts (CAFs) are known to participate in all stages of cancer progression and are increasingly acknowledged to contribute to therapy resistance. Accumulated evidence suggests that, upon radiation, fibroblasts/CAFs avoid cell death but instead enter a permanent senescent state, which in turn may influence the behavior of tumor cells and other components of the TME. Despite the proposed participation of senescent fibroblasts on tumor radioprotection, it is still incompletely understood the impact that RT has on CAFs and the ultimate role that irradiated CAFs have on therapy outcomes. Some of the current controversies may emerge from generalizing observations obtained using normal fibroblasts and CAFs, which are different cell entities that may respond differently to radiation exposure.

CONCLUSION

In this review we present current knowledge on the field of CAFs role in radiotherapy; we discuss the potential tumorigenic functions of radiation-induced senescent fibroblasts and CAFs and we make an effort to integrate the knowledge emerging from preclinical experimentation with observations from the clinics. Video Abstract.