Sensitization of ovarian tumor to immune checkpoint blockade by boosting senescence-associated secretory phenotype

Cellular senescence offers distinct immunological vulnerabilities in cancer

Chronic damage following oncogene induction or cancer therapy can produce cellular senescence. Senescent cells not only exit the cell cycle but communicate damage signals to their environment that can trigger immune responses. Recent work has revealed that senescent tumor cells are highly immunogenic, leading to new ways to activate antitumor immunosurveillance and potentiate T cell-directed immunotherapies. However, other studies have determined that heterogeneous senescent stromal cell populations contribute to immunosuppression and tumor progression, sparking the development of senotherapeutics to target senescent cells that evade immune detection. We review current findings that provide deeper insights into the mechanisms contributing to the dichotomous role of senescence in immune modulation and how that can be leveraged for cancer immunotherapy.

Cellular senescence in tumor immune escape: Mechanisms, implications, and therapeutic potential

Cellular senescence, a hallmark of aging, has emerged as a captivating area of research in tumor immunology with profound implications for cancer prevention and treatment. In the tumor microenvironment, senescent cells exhibit a dual role, simultaneously hindering tumor development through collaboration with immune cells and evading immune cell attacks by upregulating immunoinhibitory proteins. However, the intricate immune escape mechanism of cellular senescence in the tumor microenvironment remains a subject of intense investigation. Chronic inflammation is exacerbated by cellular senescence through the upregulation of pro-inflammatory factors such as interleukin-1β, thereby augmenting the risk of tumorigenesis. Additionally, the interplay between autophagy and cellular senescence adds another layer of complexity. Autophagy, known to slow down the aging process by reducing p53/p21 levels, may be downregulated by cellular senescence. To harness the therapeutic potential of cellular senescence, targeting its immunological aspects has gained significant attention. Strategies such as immune checkpoint inhibitors and T-cell senescence inhibition are being explored in the context of cellular senescence immunotherapy. In this comprehensive review, we provide a compelling overview of the regulation of cellular senescence and delve into the influencing factors, including chronic inflammation, autophagy, and circadian rhythms, associated with senescence in the tumor microenvironment. We specifically focus on unraveling the enigmatic dual role of cellular senescence in tumor immune escape. By deciphering the intricate nature of cellular senescence in the tumor microenvironment, this review aims to advance our understanding and pave the way for leveraging senescence as a promising target for tumor immunotherapy applications.

Immunosenescence, Physical Exercise, and their Implications in Tumor Immunity and Immunotherapy

Aging is associated with a decline in immune function, termed immunosenescence, which compromises host defences and increases susceptibility to infections and cancer. Physical exercise is widely recognized for its myriad health benefits, including the potential to modulate the immune system. This review explores the bidirectional relationship between immunosenescence and physical exercise, focusing on their interplay in shaping antitumor immunity. We summarize the impact of aging on innate and adaptive immune cells, highlighting alterations that contribute to immunosenescence and cancer development. We further delineate the effects of exercise on immune cell function, demonstrating its potential to mitigate immunosenescence and enhance antitumor responses. We also discuss the implications of immunosenescence for the efficacy of immunotherapies, such as immune checkpoint inhibitors and adoptive T cell therapy, and explore the potential benefits of combining exercise with these interventions. Collectively, this review underscores the importance of understanding the complex relationship between immunosenescence, physical exercise, and antitumor immunity, paving the way for the development of innovative strategies to improve cancer outcomes in the aging population.

Identification of Cellular Senescence-Related Critical Genes and Molecular Classification and Revealing the Drug-Resistant Therapeutic Effect of IGFBP2 in Chronic Myeloid Leukemia

Background

The occurrence and development of hematologic tumors are closely linked to cellular senescence. However, the molecular characteristics associated with this phenomenon in chronic myeloid leukemia (CML) have not been thoroughly investigated.

Methods

The cellular senescence score was calculated using gene set variation analysis. Consensus clustering algorithm was used to identify the molecular subtypes associated with cellular senescence. Clinical samples were collected for sequencing analysis to verify the expression of critical cellular senescence-related genes (CSRG). The effect of targeted inhibition of IGFBP2 on the malignant phenotype of CML-resistant cells was studied by cell experiments.

Results

The cellular senescence score in CML samples was significantly lower compared to normal samples. Higher expression of immune checkpoint markers correlated with increased cellular senescence scores. We identified two distinct molecular subtypes (C1 and C2) related to cellular senescence. The C1 subtype exhibited enhanced metabolic function and DNA damage repair capacity, while the C2 subtype showed higher infiltration of immune effector cells and activity in immune-related signaling pathways. We also discovered a group of drugs that displayed significant sensitivity differences between these two molecular subtypes, with the C2 subtype showing greater responsiveness to immunotherapy. Four critical cellular senescence-related genes (CSRGs), namely IGFBP2, IL7R, PLAU, and SUN1 demonstrated high diagnostic value for CML. We validated the expression levels of these four genes using clinical samples and confirmed through cell experiments that targeted inhibition of IGFBP2 effectively suppressed proliferation of resistant CML cells, promoted apoptosis, and enhanced therapeutic sensitivity to imatinib.

Conclusion

Our study conducted a comprehensive analysis on CSRG expression characteristics in CML and explored potential correlations between cellular senescence and immune function. The identification of molecular subtypes provides valuable insights into assessing individual patients' biological characteristics for guiding clinical treatment decisions. Additionally, IGFBP2 has emerged as a promising therapeutic target for therapy-resistant cases of CML.

The up-regulation of PD-L1 during boningmycin-induced senescence in human cancer cells depends on the activation of the JAK/STAT signaling pathway mediated by SASP

Therapy-induced senescence can regulate both the innate and adaptive immune systems, thereby affecting therapeutic efficacy. Bleomycin is a major component of combined chemotherapy regimens, utilized for the treatment of multiple tumors, whereas pulmonary toxicity severely restricts its clinical benefits. As a member of the bleomycin family, boningmycin (BON) exhibits potent anticancer activity with minimal pulmonary toxicity, making it a potential alternative to bleomycin. Low concentrations of BON can induce senescence, but the impact of BON-induced senescence on anticancer immunity remains unclear. This study investigates the effects of BON-induced senescence on PD-L1 expression and the underlying mechanisms in human cancer cells. Firstly, the elevation of PD-L1 protein during BON-induced senescence was confirmed by a senescence β-galactosidase staining assay, detection of the senescence-associated secretory phenotype (SASP), western blot and flow cytometry in human lung cancer NCI-H460 cells and breast cancer MDA-MB-231 cells. Subsequently, it was shown that the increase in PD-L1 protein is mediated by SASP, as evidenced by the use of conditional media, knockdown of cyclic GMP-AMP synthase and inhibition of stimulator of interferon genes. Ultimately, it was demonstrated that SASP-mediated PD-L1 up-regulation is dependent on the activation of the JAK/STAT pathway through the use of specific inhibitors and siRNAs. These findings clarify the impact of BON-induced senescence on PD-L1 expression and may contribute to the optimization of the therapeutic efficacy of bleomycin-related compounds and the clinical transformation of BON.

Cellular senescence and metabolic reprogramming: Unraveling the intricate crosstalk in the immunosuppressive tumor microenvironment

The intrinsic oncogenic mechanisms and properties of the tumor microenvironment (TME) have been extensively investigated. Primary features of the TME include metabolic reprogramming, hypoxia, chronic inflammation, and tumor immunosuppression. Previous studies suggest that senescence-associated secretory phenotypes that mediate intercellular information exchange play a role in the dynamic evolution of the TME. Specifically, hypoxic adaptation, metabolic dysregulation, and phenotypic shifts in immune cells regulated by cellular senescence synergistically contribute to the development of an immunosuppressive microenvironment and chronic inflammation, thereby promoting the progression of tumor events. This review provides a comprehensive summary of the processes by which cellular senescence regulates the dynamic evolution of the tumor-adapted TME, with focus on the complex mechanisms underlying the relationship between senescence and changes in the biological functions of tumor cells. The available findings suggest that components of the TME collectively contribute to the progression of tumor events. The potential applications and challenges of targeted cellular senescence-based and combination therapies in clinical settings are further discussed within the context of advancing cellular senescence-related research.

Targeting senescence-associated secretory phenotypes to remodel the tumour microenvironment and modulate tumour outcomes

Tumour cell senescence can be induced by various factors, including DNA damage, inflammatory signals, genetic toxins, ionising radiation and nutrient metabolism. The senescence-associated secretory phenotype (SASP), secreted by senescent tumour cells, possesses the capacity to modulate various immune cells, including macrophages, T cells, natural killer cells and myeloid-derived suppressor cells, as well as vascular endothelial cells and fibroblasts within the tumour microenvironment (TME), and this modulation can result in either the promotion or suppression of tumorigenesis and progression. Exploring the impact of SASP on the TME could identify potential therapeutic targets, yet limited studies have dissected its functions. In this review, we delve into the causes and mechanisms of tumour cell senescence. We then concentrate on the influence of SASP on the tumour immune microenvironment, angiogenesis, extracellular matrix and the reprogramming of cancer stem cells, along with their associated tumour outcomes. Last, we present a comprehensive overview of the diverse array of senotherapeutics, highlighting their prospective advantages and challenge for the treatment of cancer patients. KEY POINTS: Senescence-associated secretory phenotype (SASP) secretion from senescent tumour cells significantly impacts cancer progression and biology. SASP is involved in regulating the remodelling of the tumour microenvironment, including immune microenvironment, vascular, extracellular matrix and cancer stem cells. Senotherapeutics, such as senolytic, senomorphic, nanotherapy and senolytic vaccines, hold promise for enhancing cancer treatment efficacy.

Therapy-Induced Senescence: Novel Approaches for Markers Identification

Therapy-induced senescence (TIS) represents a major cellular response to anticancer treatments. Both malignant and non-malignant cells in the tumor microenvironment undergo TIS and may be harmful for cancer patients since TIS cells develop a senescence-associated secretory phenotype (SASP) that can sustain tumor growth. The SASP also modulates anti-tumor immunity, although the immune populations involved and the final results appear to be context-dependent. In addition, senescent cancer cells are able to evade senescence growth arrest and to resume proliferation, likely contributing to relapse. So, research data suggest that TIS induction negatively affects therapy outcomes in cancer patients. In line with this, new interventions aimed at the removal of senescent cells or the reprogramming of their SASP, called senotherapy, have become attractive therapeutic options. To date, the lack of reliable, cost-effective, and easy-to-use TIS biomarkers hinders the application of recent anti-senescence therapeutic approaches in the clinic. Hence, the identification of biomarkers for the detection of TIS tumor cells and TIS non-neoplastic cells is a high priority in cancer research. In this review article, we describe the current knowledge about TIS, outline critical gaps in our knowledge, and address recent advances and novel approaches for the discovery of TIS biomarkers.

Therapy-Induced Cellular Senescence: Potentiating Tumor Elimination or Driving Cancer Resistance and Recurrence?

Cellular senescence has been increasingly recognized as a hallmark of cancer, reflecting its association with aging and inflammation, its role as a response to deregulated proliferation and oncogenic stress, and its induction by cancer therapies. While therapy-induced senescence (TIS) has been linked to resistance, recurrence, metastasis, and normal tissue toxicity, TIS also has the potential to enhance therapy response and stimulate anti-tumor immunity. In this review, we examine the Jekyll and Hyde nature of senescent cells (SnCs), focusing on how their persistence while expressing the senescence-associated secretory phenotype (SASP) modulates the tumor microenvironment through autocrine and paracrine mechanisms. Through the SASP, SnCs can mediate both resistance and response to cancer therapies. To fulfill the unmet potential of cancer immunotherapy, we consider how SnCs may influence tumor inflammation and serve as an antigen source to potentiate anti-tumor immune response. This new perspective suggests treatment approaches based on TIS to enhance immune checkpoint blockade. Finally, we describe strategies for mitigating the detrimental effects of senescence, such as modulating the SASP or targeting SnC persistence, which may enhance the overall benefits of cancer treatment.

A cellular senescence-related signature for predicting prognosis, immunotherapy response, and candidate drugs in patients treated with transarterial chemoembolization (TACE)

BACKGROUND

Cellular senescence is essential to TME development, progression, and remodeling. Few studies have examined cellular senescence in HCC after TACE. Investigating the relationship between cellular senescence, post-TACE prognosis, the TME, and immune treatment responses is crucial.

METHODS

We analyzed the GSE104580 dataset to identify DEGs. A cellular senescence-related signature was developed using LASSO Cox regression in the GSE14520 dataset and validated in the ICGC dataset. High- and low-risk subgroups were compared using GSVA and GSEA. Correlation studies were conducted to explore the relationship between the prognostic model, immune infiltration, immunotherapy response, and drug sensitivity.

RESULTS

A cellular senescence-related signature comprising FOXM1, CDK1, CHEK1, and SERPINE1 was created and validated. High-risk patients showed significantly lower OS than low-risk patients. High-risk patients had carcinogenetic pathways activated, immunosuppressive cells infiltrated, and immunomodulatory genes overexpressed. They also showed higher sensitivity to EPZ004777_1237 and MK-2206_1053 and potential benefits from GSK-3 inhibitor IX, nortriptyline, lestaurtinib, and JNK-9L.

CONCLUSIONS

This study constructed a cellular senescence-related signature that could be used to predict HCC patients' responses to and prognosis after TACE treatment, aiding in the development of personalized treatment plans.

The Role of Aging and Senescence in Immune Checkpoint Inhibitor Response and Toxicity

Cellular senescence accumulates with age and has been shown to impact numerous physiological and pathological processes, including immune function. The role of cellular senescence in cancer is multifaceted, but the impact on immune checkpoint inhibitor response and toxicity has not been fully evaluated. In this review, we evaluate the impact of cellular senescence in various biological compartments, including the tumor, the tumor microenvironment, and the immune system, on immune checkpoint inhibitor efficacy and toxicity. We provide an overview of the impact of cellular senescence in normal and pathological contexts and examine recent studies that have connected aging and cellular senescence to immune checkpoint inhibitor treatment in both the pre-clinical and clinical contexts. Overall, senescence plays a multi-faceted, context-specific role and has been shown to modulate immune-related adverse event incidence as well as immune checkpoint inhibitor response.

Senescence-associated secretory phenotype (SASP) and uterine fibroids: Association with PD-L1 activation and collagen deposition

Uterine fibroids (or uterine leiomyoma, UFs) are one of the most prevalent benign uterine tumors with high proliferation and collagen synthesis capabilities. UFs are a significant worldwide health issue for women, affecting their physical and financial well-being. Risk factors for UFs include age, racial disparities, obesity, uterine infections, hormonal variation, and lifestyle (i.e., diet, exercise, stress, and smoking). Senescence and its associated secretory phenotypes (SASPs) are among the most salient changes accompanying the aging process. As a result, SASPs are suggested to be one of the major contributors to developing UFs. Interleukin 6 (IL-6), IL-8, IL-1, chemokine ligand 20 (CCL-20), and transforming growth factor-beta (TGF-β) are the most prominent SASPs associated with aging. In addition, different processes contribute to UFs such as collagen deposition and the changes in the immune microenvironment. Programmed death ligand 1 is a major player in the tumor immune microenvironment, which helps tumor cells evade immune attacks. This review focuses on the correlation of SASPs on two axes of tumor progression: immune suppression and collagen deposition. This review opens the door towards more investigations regarding changes in the UF immune microenvironment and age-UFs correlation and thus, a novel targeting approach for UF treatment.

Macrophages and tumor-associated macrophages in the senescent microenvironment: From immunosuppressive TME to targeted tumor therapy

In-depth studies of the tumor microenvironment (TME) have helped to elucidate its cancer-promoting mechanisms and inherent characteristics. Cellular senescence, which acts as a response to injury and can the release of senescence-associated secretory phenotypes (SASPs). These SASPs release various cytokines, chemokines, and growth factors, remodeling the TME. This continual development of a senescent environment could be associated with chronic inflammation and immunosuppressive TME. Additionally, SASPs could influence the phenotype and function of macrophages, leading to the recruitment of tumor-associated macrophages (TAMs). This contributes to tumor proliferation and metastasis in the senescent microenvironment, working in tandem with immune regulation, angiogenesis, and therapeutic resistance. This comprehensive review covers the evolving nature of the senescent microenvironment, macrophages, and TAMs in tumor development. We also explored the links between chronic inflammation, immunosuppressive TME, cellular senescence, and macrophages. Moreover, we compiled various tumor-specific treatment strategies centered on cellular senescence and the current challenges in cellular senescence research. This study aimed to clarify the mechanism of macrophages and the senescent microenvironment in tumor progression and advance the development of targeted tumor therapies.

De Novo Purine Metabolism is a Metabolic Vulnerability of Cancers with Low p16 Expression

p16 is a tumor suppressor encoded by the CDKN2A gene whose expression is lost in approximately 50% of all human cancers. In its canonical role, p16 inhibits the G1-S-phase cell cycle progression through suppression of cyclin-dependent kinases. Interestingly, p16 also has roles in metabolic reprogramming, and we previously published that loss of p16 promotes nucleotide synthesis via the pentose phosphate pathway. However, the broader impact of p16/CDKN2A loss on other nucleotide metabolic pathways and potential therapeutic targets remains unexplored. Using CRISPR knockout libraries in isogenic human and mouse melanoma cell lines, we determined several nucleotide metabolism genes essential for the survival of cells with loss of p16/CDKN2A. Consistently, many of these genes are upregulated in melanoma cells with p16 knockdown or endogenously low CDKN2A expression. We determined that cells with low p16/CDKN2A expression are sensitive to multiple inhibitors of de novo purine synthesis, including antifolates. Finally, tumors with p16 knockdown were more sensitive to the antifolate methotrexate in vivo than control tumors. Together, our data provide evidence to reevaluate the utility of these drugs in patients with p16/CDKN2Alow tumors as loss of p16/CDKN2A may provide a therapeutic window for these agents.

SIGNIFICANCE

Antimetabolites were the first chemotherapies, yet many have failed in the clinic due to toxicity and poor patient selection. Our data suggest that p16 loss provides a therapeutic window to kill cancer cells with widely-used antifolates with relatively little toxicity.

A senescence-mimicking (senomimetic) VEGFR TKI side-effect primes tumor immune responses via IFN/STING signaling

Tyrosine kinase inhibitors (TKIs) that block the vascular endothelial growth factor receptors (VEGFRs) disrupt tumor angiogenesis but also have many unexpected side-effects that impact tumor cells directly. This includes the induction of molecular markers associated with senescence, a form of cellular aging that typically involves growth arrest. We have shown that VEGFR TKIs can hijack these aging programs by transiently inducting senescence-markers (SMs) in tumor cells to activate senescence-associated secretory programs that fuel drug resistance. Here we show that these same senescence-mimicking ('senomimetic') VEGFR TKI effects drive an enhanced immunogenic signaling that, in turn, can alter tumor response to immunotherapy. Using a live-cell sorting method to detect beta-galactosidase, a commonly used SM, we found that subpopulations of SM-expressing (SM+) tumor cells have heightened interferon (IFN) signaling and increased expression of IFN-stimulated genes (ISGs). These ISG increases were under the control of the STimulator of INterferon Gene (STING) signaling pathway, which we found could be directly activated by several VEGFR TKIs. TKI-induced SM+ cells could stimulate or suppress CD8 T-cell activation depending on host:tumor cell contact while tumors grown from SM+ cells were more sensitive to PD-L1 inhibition in vivo, suggesting that offsetting immune-suppressive functions of SM+ cells can improve TKI efficacy overall. Our findings may explain why some (but not all) VEGFR TKIs improve outcomes when combined with immunotherapy and suggest that exploiting senomimetic drug side-effects may help identify TKIs that uniquely 'prime' tumors for enhanced sensitivity to PD-L1 targeted agents.

Understanding Cancer's Defense against Topoisomerase-Active Drugs: A Comprehensive Review

In recent years, the emergence of cancer drug resistance has been one of the crucial tumor hallmarks that are supported by the level of genetic heterogeneity and complexities at cellular levels. Oxidative stress, immune evasion, metabolic reprogramming, overexpression of ABC transporters, and stemness are among the several key contributing molecular and cellular response mechanisms. Topo-active drugs, e.g., doxorubicin and topotecan, are clinically active and are utilized extensively against a wide variety of human tumors and often result in the development of resistance and failure to therapy. Thus, there is an urgent need for an incremental and comprehensive understanding of mechanisms of cancer drug resistance specifically in the context of topo-active drugs. This review delves into the intricate mechanistic aspects of these intracellular and extracellular topo-active drug resistance mechanisms and explores the use of potential combinatorial approaches by utilizing various topo-active drugs and inhibitors of pathways involved in drug resistance. We believe that this review will help guide basic scientists, pre-clinicians, clinicians, and policymakers toward holistic and interdisciplinary strategies that transcend resistance, renewing optimism in the ongoing battle against cancer.

Metabolic and senescence characteristics associated with the immune microenvironment in ovarian cancer

Ovarian cancer is a highly malignant gynecological cancer influenced by the immune microenvironment, metabolic reprogramming, and cellular senescence. This review provides a comprehensive overview of these characteristics. Metabolic reprogramming affects immune cell function and tumor growth signals. Cellular senescence in immune and tumor cells impacts anti-tumor responses and therapy resistance. Targeting immune cell metabolism and inducing tumor cell senescence offer potential therapeutic strategies. However, challenges remain in identifying specific targets and biomarkers. Understanding the interplay of these characteristics can lead to innovative therapeutic approaches. Further research is needed to elucidate mechanisms, validate strategies, and improve patient outcomes in ovarian cancer.

Combination of PARP inhibitor and CDK4/6 inhibitor modulates cGAS/STING-dependent therapy-induced senescence and provides "one-two punch" opportunity with anti-PD-L1 therapy in colorectal cancer

Although PARP inhibitor (PARPi) has been proven to be a promising anticancer drug in cancer patients harboring BRCA1/2 mutation, it provides limited clinical benefit in colorectal cancer patients with a low prevalence of BRCA1/2 mutations. In our study, we found PARPi talazoparib significantly induced cellular senescence via inhibiting p53 ubiquitination and activating p21. Furthermore, CDK4/6i palbociclib amplified this therapy-induced senescence (TIS) in vitro and in vivo. Mechanistically, talazoparib and palbociclib combination induced senescence-associated secretory phenotype (SASP), and characterization of SASP components revealed type I interferon (IFN)-related mediators, which were amplified by cGAS/STING signaling. More importantly, RNA sequencing data indicated that combination therapy activated T cell signatures and combination treatment transformed the tumor microenvironment (TME) into a more antitumor state with increased CD8 T cells and natural killer (NK) cells and decreased macrophages and granulocytic myeloid-derived suppressor cells (G-MDSCs). Moreover, clearance of the TIS cells by αPD-L1 promoted survival in immunocompetent mouse colorectal cancer models. Collectively, we elucidated the synergistic antitumor and immunomodulatory mechanisms of the talazoparib-palbociclib combination. Further combination with PD-L1 antibody might be a promising "one-two punch" therapeutic strategy for colorectal cancer patients.

Identification of cellular senescence-related signature for predicting prognosis and therapeutic response of acute myeloid leukemia

Cellular senescence is closely related to the occurrence, development, and immune regulation of cancer. However, the predictive value of cellular senescence-related signature in clinical outcome and treatment response in acute myeloid leukemia (AML) remains unexplored. By analyzing the expression profile of cellular senescence-related genes (CSRGs) in AML samples in the TCGA database, we found that cellular senescence is closely related to the prognosis and tumor microenvironment of AML patients, and compared with normal samples, the overall expression level of senescent inducing genes in AML samples was down-regulated, while inhibitory genes were up-regulated. The risk score model further constructed and verified based on CSRGs could be used as an independent prognostic predictor for AML patients, and the overall survival (OS) of high-risk patients was significantly shortened. The area under ROC curve (AUC) values for the prediction of 1-, 3- and 5-year OS were 0.759, 0.749, and 0.806, respectively. In addition, patients with high-risk scores are more sensitive to treatment with cytarabine and may benefit from anti-PD-1 immunotherapy. In conclusion, our results suggest that the cellular senescence-related signature is a strong biomarker of immunotherapy response and prognosis in AML.

De novo purine metabolism is a metabolic vulnerability of cancers with low p16 expression

p16 is a tumor suppressor encoded by the CDKN2A gene whose expression is lost in ~50% of all human cancers. In its canonical role, p16 inhibits the G1-S phase cell cycle progression through suppression of cyclin dependent kinases. Interestingly, p16 also has roles in metabolic reprogramming, and we previously published that loss of p16 promotes nucleotide synthesis via the pentose phosphate pathway. Whether other nucleotide metabolic genes and pathways are affected by p16/CDKN2A loss and if these can be specifically targeted in p16/CDKN2A-low tumors has not been previously explored. Using CRISPR KO libraries in multiple isogenic human and mouse melanoma cell lines, we determined that many nucleotide metabolism genes are negatively enriched in p16/CDKN2A knockdown cells compared to controls. Indeed, many of the genes that are required for survival in the context of low p16/CDKN2A expression based on our CRISPR screens are upregulated in p16 knockdown melanoma cells and those with endogenously low CDKN2A expression. We determined that cells with low p16/Cdkn2a expression are sensitive to multiple inhibitors of de novo purine synthesis, including anti-folates. Tumors with p16 knockdown were more sensitive to the anti-folate methotrexate in vivo than control tumors. Together, our data provide evidence to reevaluate the utility of these drugs in patients with p16/CDKN2A-low tumors as loss of p16/CDKN2A may provide a therapeutic window for these agents.

Targeting Senescence as a Therapeutic Opportunity for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is associated with an elevated risk of recurrence and poor prognosis. Historically, only chemotherapy was available as systemic treatment, but immunotherapy and targeted therapies currently offer prolonged benefits. TNBC is a group of diseases with heterogeneous treatment sensitivity, and resistance is inevitable and early for a large proportion of the intrinsic subtypes. Although senescence induction by anticancer therapy offers an immediate favorable clinical outcome once the rate of tumor progression reduces, these cells are commonly dysfunctional and metabolically active, culminating in treatment-resistant repopulation associated with worse prognosis. This heterogeneous response can also occur without therapeutic pressure in response to damage or oncogenic stress, playing a relevant role in the carcinogenesis. Remarkably, there is preclinical and exploratory clinical evidence to support a relevant role of senescence in treatment resistance. Therefore, targeting senescent cells has been a scientific effort in many malignant tumors using a variety of targets and strategies, including increasing proapoptotic and decreasing antiapoptotic stimuli. Despite promising results, there are some challenges to applying this technology, including the best schedule of combination, assessment of senescence, specific vulnerabilities, and the best clinical scenarios. This review provides an overview of senescence in TNBC with a focus on future-proofing senotherapy strategies.

Senescence and Immunotherapy: Redundant Immunomodulatory Pathways Promote Resistance

Senescent cancer cells alter their microenvironment through secretion of pro-inflammatory cytokines and chemokines called the senescence-associated secretory phenotype (SASP) and upregulation of immunoinhibitory proteins such as CD80 and programmed death-ligand 1. The senescence field is just beginning to explore the role of these changes on antitumor immunity and response to immunotherapy. In this Perspective, we highlight a new study that aimed to determine how senescent breast cancer cells are shielded from immunosurveillance via upregulation of redundant immunoinhibitory proteins in two distinct senescent populations. We also discuss recent articles regarding how the SASP alters the tumor immune microenvironment and response to immunotherapy. As many therapies used to treat cancers induce senescence, future work will need to better refine the composition of the SASP and heterogeneity of senescence in the tumor microenvironment to more completely understand how the immune compartment is regulated by senescent tumors.

TGF-β in the microenvironment induces a physiologically occurring immune-suppressive senescent state

TGF-β induces senescence in embryonic tissues. Whether TGF-β in the hypoxic tumor microenvironment (TME) induces senescence in cancer and how the ensuing senescence-associated secretory phenotype (SASP) remodels the cellular TME to influence immune checkpoint inhibitor (ICI) responses are unknown. We show that TGF-β induces a deeper senescent state under hypoxia than under normoxia; deep senescence correlates with the degree of E2F suppression and is marked by multinucleation, reduced reentry into proliferation, and a distinct 14-gene SASP. Suppressing TGF-β signaling in tumors in an immunocompetent mouse lung cancer model abrogates endogenous senescent cells and suppresses the 14-gene SASP and immune infiltration. Untreated human lung cancers with a high 14-gene SASP display immunosuppressive immune infiltration. In a lung cancer clinical trial of ICIs, elevated 14-gene SASP is associated with increased senescence, TGF-β and hypoxia signaling, and poor progression-free survival. Thus, TME-induced senescence may represent a naturally occurring state in cancer, contributing to an immune-suppressive phenotype associated with immune therapy resistance.

Aging microenvironment and antitumor immunity for geriatric oncology: the landscape and future implications

The tumor microenvironment (TME) has been extensively investigated; however, it is complex and remains unclear, especially in elderly patients. Senescence is a cellular response to a variety of stress signals, which is characterized by stable arrest of the cell cycle and major changes in cell morphology and physiology. To the best of our knowledge, senescence leads to consistent arrest of tumor cells and remodeling of the tumor-immune microenvironment (TIME) by activating a set of pleiotropic cytokines, chemokines, growth factors, and proteinases, which constitute the senescence-associated secretory phenotype (SASP). On the one hand, the SASP promotes antitumor immunity, which enhances treatment efficacy; on the other hand, the SASP increases immunosuppressive cell infiltration, including myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), M2 macrophages, and N2 neutrophils, contributing to TIME suppression. Therefore, a deeper understanding of the regulation of the SASP and components contributing to robust antitumor immunity in elderly individuals with different cancer types and the available therapies is necessary to control tumor cell senescence and provide greater clinical benefits to patients. In this review, we summarize the key biological functions mediated by cytokines and intercellular interactions and significant components of the TME landscape, which influence the immunotherapy response in geriatric oncology. Furthermore, we summarize recent advances in clinical practices targeting TME components and discuss potential senescent TME targets.

Senescent cancer cell vaccines induce cytotoxic T cell responses targeting primary tumors and disseminated tumor cells

BACKGROUND

Immune tolerance contributes to resistance to conventional cancer therapies such as radiation. Radiotherapy induces immunogenic cell death, releasing a burst of tumor antigens, but this appears insufficient to stimulate an effective antitumor immune response. Radiation also increases infiltration of cytotoxic T lymphocytes (CTLs), but their effector function is short lived. Although CTL exhaustion may be at fault, combining immune checkpoint blockade with radiation is insufficient to restore CTL function in most patients. An alternative model is that antigen presentation is the limiting factor, suggesting a defect in dendritic cell (DC) function.

METHODS

Building on our prior work showing that cancer cells treated with radiation in the presence of the poly(ADP-ribose) polymerase-1 inhibitor veliparib undergo immunogenic senescence, we reexamined senescent cells (SnCs) as preventative or therapeutic cancer vaccines. SnCs formed in vitro were cocultured with splenocytes and evaluated by scRNA-seq to examine immunogenicity. Immature bone-marrow-derived DCs cocultured with SnCs were examined for maturation and activation by flow cytometry and T cell proliferation assays. Viable SnCs or SnC-activated DCs were injected subcutaneously, and vaccine effects were evaluated by analysis of immune response, prevention of tumor engraftment, regression of established tumors and/or potentiation of immunotherapy or radiotherapy.

RESULTS

Murine CT26 colon carcinoma or 4T1 mammary carcinoma cells treated with radiation and veliparib form SnCs that promote DC maturation and activation in vitro, leading to efficient, STING-dependent CTL priming. Injecting mice with SnCs induces antigen-specific CTLs and confers protection from tumor engraftment. Injecting immunogenic SnCs into tumor-bearing mice increases inflammation with activated CTLs, suppresses tumor growth, potentiates checkpoint blockade, enhances radiotherapy and blocks colonization by disseminated tumor cells. Addressing the concern that reinjecting tumor cells into patients may be impractical, DCs activated with SnCs in vitro were similarly effective to SnCs in suppressing established tumors and blocking metastases.

CONCLUSIONS

Therapeutic vaccines based on senescent tumor cells and/or SnC-activated DCs have the potential to improve genotoxic and immune therapies and limit recurrence or metastasis.

IL-1 and senescence: Friends and foe of EGFR neutralization and immunotherapy

Historically, senescence has been considered a safe program in response to multiple stresses in which cells undergo irreversible growth arrest. This process is characterized by morphological and metabolic changes, heterochromatin formation, and secretion of inflammatory components, known as senescence-associated secretory phenotype (SASP). However, recent reports demonstrated that anti-cancer therapy itself can stimulate a senescence response in tumor cells, the so-called therapy-induced senescence (TIS), which may represent a temporary bypass pathway that promotes drug resistance. In this context, several studies have shown that EGFR blockage, by TKIs or moAbs, promotes TIS by increasing IL-1 cytokine production, thus pushing cells into a "pseudo-senescent" state. Today, senotherapeutic agents are emerging as a potential strategy in cancer treatment thanks to their dual role in annihilating senescent cells and simultaneously preventing their awakening into a resistant and aggressive form. Here, we summarize classic and recent findings about the cellular processes driving senescence and SASP, and we provide a state-of-the-art of the anti-cancer strategies available so far that exploits the activation and/or blockade of senescence-based mechanisms.

Obesity triggers tumoral senescence and renders poorly immunogenic malignancies amenable to senolysis

Obesity is a major risk factor for cancer. Conventional thought suggests that elevated adiposity predisposes to heightened inflammatory stress and potentiates tumor growth, yet underlying mechanisms remain ill-defined. Here, we show that tumors from patients with a body mass index >35 carry a high burden of senescent cells. In mouse syngeneic tumor models, we correlated a pronounced accretion of senescent cancer cells with poorly immunogenic tumors when mice were subjected to diet-induced obesity (DIO). Highly immunogenic tumors showed lesser senescence burden suggesting immune-mediated elimination of senescent cancer cells, likely targeted as a consequence of their senescence-associated secretory phenotype. Treatment with the senolytic BH3 mimetic small molecule inhibitor ABT-263 selectively stalled tumor growth in mice with DIO to rates comparable to regular diet-fed mice. Thus, consideration of body adiposity in the selection of cancer therapy may be a critical determinant for disease outcome in poorly immunogenic malignancies.

Intrinsic and Extrinsic Transcriptional Profiles That Affect the Clinical Response to PD-1 Inhibitors in Patients with Non-Small Cell Lung Cancer

Using a machine learning method, we investigated the intrinsic and extrinsic transcriptional profiles that affect the clinical response to PD-1 inhibitors in 57 patients with non-small cell lung cancer (NSCLC). Among the top 100 genes associated with the responsiveness to PD-1 inhibitors, the proportion of intrinsic genes in lung adenocarcinoma (LUAD) (69%) was higher than in NSCLC overall (36%) and lung squamous cell carcinoma (LUSC) (33%). The intrinsic gene signature of LUAD (mean area under the ROC curve (AUC) = 0.957 and mean accuracy = 0.9) had higher predictive power than either the intrinsic gene signature of NSCLC or LUSC or the extrinsic gene signature of NSCLC, LUAD, or LUSC. The high intrinsic gene signature group had a high overall survival rate in LUAD (p = 0.034). When we performed a pathway enrichment analysis, the cell cycle and cellular senescence pathways were related to the upregulation of intrinsic genes in LUAD. The intrinsic signature of LUAD also showed a positive correlation with other immune checkpoint targets, including CD274, LAG3, and PDCD1LG2 (Spearman correlation coefficient > 0.25). PD-1 inhibitor-related intrinsic gene patterns differed significantly between LUAD and LUSC and may be a particularly useful biomarker in LUAD.

Role of the Hypoxic-Secretome in Seed and Soil Metastatic Preparation

During tumor growth, the delivery of oxygen to cells is impaired due to aberrant or absent vasculature. This causes an adaptative response that activates the expression of genes that control several essential processes, such as glycolysis, neovascularization, immune suppression, and the cancer stemness phenotype, leading to increased metastasis and resistance to therapy. Hypoxic tumor cells also respond to an altered hypoxic microenvironment by secreting vesicles, factors, cytokines and nucleic acids that modify not only the immediate microenvironment but also organs at distant sites, allowing or facilitating the attachment and growth of tumor cells and contributing to metastasis. Hypoxia induces the release of molecules of different biochemical natures, either secreted or inside extracellular vesicles, and both tumor cells and stromal cells are involved in this process. The mechanisms by which these signals that can modify the premetastatic niche are sent from the primary tumor site include changes in the extracellular matrix, recruitment and activation of different stromal cells and immune or nonimmune cells, metabolic reprogramming, and molecular signaling network rewiring. In this review, we will discuss how hypoxia might alter the premetastatic niche through different signaling molecules.

Integration of local and systemic immunity in ovarian cancer: Implications for immunotherapy

Cancer is a disease that induces many local and systemic changes in immunity. The difficult nature of ovarian cancer stems from the lack of characteristic symptoms that contributes to a delayed diagnosis and treatment. Despite the enormous progress in immunotherapy, its efficacy remains limited. The heterogeneity of tumors, lack of diagnostic biomarkers, and complex immune landscape are the main challenges in the treatment of ovarian cancer. Integrative approaches that combine the tumor microenvironment - local immunity - together with periphery - systemic immunity - are urgently needed to improve the understanding of the disease and the efficacy of treatment. In fact, multiparametric analyses are poised to improve our understanding of ovarian tumor immunology. We outline an integrative approach including local and systemic immunity in ovarian cancer. Understanding the nature of both localized and systemic immune responses will be crucial to boosting the efficacy of immunotherapies in ovarian cancer patients.

Senescence and the tumor-immune landscape: Implications for cancer immunotherapy

Cancer therapies, including conventional chemotherapy, radiation, and molecularly targeted agents, can lead to tumor eradication through a variety of mechanisms. In addition to their effects on tumor cell growth and survival, these regimens can also influence the surrounding tumor-immune microenvironment in ways that ultimately impact therapy responses. A unique biological outcome of cancer therapy is induction of cellular senescence. Senescence is a damage-induced stress program that leads to both the durable arrest of tumor cells and remodeling the tumor-immune microenvironment through activation of a collection pleiotropic cytokines, chemokines, growth factors, and proteinases known as the senescence-associated secretory phenotype (SASP). Depending on the cancer context and the mechanism of action of the therapy, the SASP produced following therapy-induced senescence (TIS) can promote anti-tumor immunity that enhances therapeutic efficacy, or alternatively chronic inflammation that leads to therapy failure and tumor relapse. Thus, a deeper understanding of the mechanisms regulating the SASP and components necessary for robust anti-tumor immune surveillance in different cancer and therapy contexts are key to harnessing senescence for tumor control. Here we draw a roadmap to modulate TIS and its immune-stimulating features for cancer immunotherapy.

Upregulation of PD-L1 in Senescence and Aging

Cellular senescence is a stable form of cell cycle arrest associated with proinflammatory responses. Senescent cells can be cleared by the immune system as a part of normal tissue homeostasis. However, senescent cells can also accumulate in aged and diseased tissues, contributing to inflammation and disease progression. The mechanisms mediating the impaired immune-mediated clearance of senescent cells are poorly understood. Here, we report that senescent cells upregulate the immune checkpoint molecule PD-L1, the ligand for PD-1 on immune cells, which drives immune cell inactivation. The induction of PD-L1 in senescence is dependent on the proinflammatory program. Furthermore, the secreted factors released by senescent cells are sufficient to upregulate PD-L1 in nonsenescent control cells, mediated by the JAK-STAT pathway. In addition, we show that prolongevity intervention rapamycin downregulates PD-L1 in senescent cells. Last, we found that PD-L1 is upregulated in several tissues in naturally aged mice and in the lungs of idiopathic pulmonary fibrosis patients. Together, our results report that senescence and aging are associated with upregulation of a major immune checkpoint molecule, PD-L1. Targeting PD-L1 may offer new therapeutic opportunities in treating senescence and age-associated diseases.

High Hemin Concentration Induces Escape from Senescence of Normoxic and Hypoxic Colon Cancer Cells

Simple Summary

High red-meat consumption as well as bleeding or bruising can promote oxidative stress and, in consequence, cancer development. However, the mechanism of that phenomenon is not understood. The induction of therapy-induced senescence (TIS) might also be induced by oxidative stress. Recently, TIS cells, despite their inhibited proliferation potential, have been identified as one of the sources of tumor re-growth. Here, with the use of molecular analyses, we found that oxidative stress, promoted by high doses of hemin or H₂O₂, can trigger TIS escape and cell re-population. It is closely related to the activity of antioxidative enzymes, especially heme oxygenase-1. Hypoxia might accelerate these effects. Therefore, we propose that the prevention of excessive oxidative stress could be a potential target in senolytic therapies.

Abstract

Hemoglobin from either red meat or bowel bleeding may promote oxidative stress and increase the risk of colorectal cancer (CRC). Additionally, solid cancers or their metastases may be present with localized bruising. Escape from therapy-induced senescence (TIS) might be one of the mechanisms of tumor re-growth. Therefore, we sought to study whether hemin can cause escape from TIS in CRC. To induce senescence, human colon cancer cells were exposed to a chemotherapeutic agent irinotecan (IRINO). Cells treated with IRINO exhibited common hallmarks of TIS. To mimic bleeding, colon cancer cells were additionally treated with hemin. High hemin concentration activated heme oxygenase-1 (HO-1), induced escape from TIS and epithelial-to-mesenchymal transition, and augmented progeny production. The effect was even stronger in hypoxic conditions. Similar results were obtained when TIS cells were treated with another prooxidant agent, H₂O₂. Silencing of antioxidative enzymes such as catalase (CAT) or glutathione peroxidase-1 (GPx-1) maintained colon cancer cells in a senescent state. Our study demonstrates that a high hemin concentration combined with an increased activity of antioxidative enzymes, especially HO-1, leads to escape from the senescence of colon cancer cells. Therefore, our observations could be used in targeted anti-cancer therapy.

STING mediates nuclear PD-L1 targeting-induced senescence in cancer cells

Immune checkpoint molecule programmed death-ligand 1 (PD-L1) is overexpressed in cancer cells and imparts resistance to cancer therapy. Although membrane PD-L1 has been targeted for cancer immune therapy, nuclear PD-L1 was reported to confer cancer resistance. Therefore, it is important to regulate the nuclear PD-L1. The mechanisms underlying the therapeutic efficacy of PD-L1 targeting have not been well-established. Cellular senescence has been considered a pivotal mechanism to prevent cancer progression, and recently, PD-L1 inhibition was shown to be involved in cancer cell senescence. However, the relevance of PD-L1 targeting-induced senescence and the role of stimulator of interferon genes (STING) has not been reported. Therefore, we aimed to identify the role of PD-L1 in cancer progression and how it regulates cancer prevention. In this study, we found that PD-L1 depletion-induced senescence via strong induction of STING expression in mouse melanoma B16-F10 and colon cancer CT26 cells, and in human melanoma A375 and lung cancer A549 cells. Interestingly, nuclear PD-L1 silencing increased STING promoter activity, implying that PD-L1 negatively regulates STING expression via transcriptional modulation. Furthermore, we showed that PD-L1 binds to the STING promoter region, indicating that PD-L1 directly controls STING expression to promote cancer growth. In addition, when we combined PD-L1 silencing with the senescence-inducing chemotherapeutic agent doxorubicin, the effect of PD-L1-targeting was even more powerful. Overall, our findings can contribute to the understanding of the role of PD-L1 in cancer therapy by elucidating a novel mechanism for PD-L1 targeting in cancer cells.

Cellular senescence and the tumour microenvironment

The senescence-associated secretory phenotype (SASP), where senescent cells produce a variety of secreted proteins including inflammatory cytokines, chemokines, matrix remodelling factors, growth factors and so on, plays pivotal but varying roles in the tumour microenvironment. The effects of SASP on the surrounding microenvironment depend on the cell type and process of cellular senescence induction, which is often associated with innate immunity. Via SASP-mediated paracrine effects, senescent cells can remodel the surrounding tissues by modulating the character of adjacent cells, such as stromal, immune cells, as well as cancer cells. The SASP is associated with both tumour-suppressive and tumour-promoting effects, as observed in senescence surveillance effects (tumour-suppressive) and suppression of anti-tumour immunity in most senescent cancer-associated fibroblasts and senescent T cells (tumour-promoting). In this review, we discuss the features and roles of senescent cells in tumour microenvironment with emphasis on their context-dependency that determines whether they promote or suppress cancer development. Potential usage of recently developed drugs that suppress the SASP (senomorphics) or selectively kill senescence cells (senolytics) in cancer therapy are also discussed.

Immunosenescence, inflammaging, and cancer immunotherapy efficacy

INTRODUCTION

Immunosenescence is a progressive remodeling of immune functions associated with a decreased ability of the immune system to set up an efficient immune response, both innate and adaptive, with an increase of highly differentiated T cells at the expense of naive T cells. The incidence and prevalence of most cancers increase with age, which can partly be explained by tumor escape mechanisms and decreased immunosurveillance. Aging is also associated with inflammaging, a low-grade proinflammatory state characterized by an increase in inflammatory mediators. Anti-cancer immunotherapy has profoundly changed the landscape of oncology therapy in the last 10 years. Modern T-cell targeted therapies such as bispecific T cell engagers, CAR-T cells, or immune checkpoint blockers may be theoretically affected by immunosenescence or inflammaging.

AREAS COVERED

A bibliographic review through PubMed and Embase was carried out using the following search terms: 'immunosenescence,' 'immunotherapy,' 'inflammaging,' 'bispecific antibodies,' 'CAR-T cells,' 'immune checkpoint blockers,' and 'older patients.'

EXPERT OPINION

This review explores the potential impact of immunosenescence and inflammaging on anti-cancer immunotherapy and therapeutic strategies that could counter immune senescence. A more dedicated research on immunosenescence biomarkers in future clinical trials is warranted for the development of new, more effective and safer therapies.

The senescence-associated secretory phenotype in ovarian cancer dissemination

Ovarian cancer is a highly aggressive disease with poor survival rates in part due to diagnosis after dissemination throughout the peritoneal cavity. It is well-known that inflammatory signals affect ovarian cancer dissemination. Inflammation is a hallmark of cellular senescence, a stable cell cycle arrest induced by a variety of stimuli including many of the therapies used to treat patients with ovarian cancer. Indeed, recent work has illustrated that ovarian cancer cells in vitro, mouse models, and patient tumors undergo senescence in response to platinum-based or poly(ADP-ribose) polymerase (PARP) inhibitor therapies, standard-of-care therapies for ovarian cancer. This inflammatory response, termed the senescence-associated secretory phenotype (SASP), is highly dynamic and has pleiotropic roles that can be both beneficial and detrimental in cell-intrinsic and cell-extrinsic ways. Recent data on other cancer types suggest that the SASP promotes metastasis. Here, we outline what is known about the SASP in ovarian cancer and discuss both how the SASP may promote ovarian cancer dissemination and strategies to mitigate the effects of the SASP.

Endowing universal CAR T-cell with immune-evasive properties using TALEN-gene editing

Universal CAR T-cell therapies are poised to revolutionize cancer treatment and to improve patient outcomes. However, realizing these advantages in an allogeneic setting requires universal CAR T-cells that can kill target tumor cells, avoid depletion by the host immune system, and proliferate without attacking host tissues. Here, we describe the development of a novel immune-evasive universal CAR T-cells scaffold using precise TALEN-mediated gene editing and DNA matrices vectorized by recombinant adeno-associated virus 6. We simultaneously disrupt and repurpose the endogenous TRAC and B2M loci to generate TCRαβ- and HLA-ABC-deficient T-cells expressing the CAR construct and the NK-inhibitor named HLA-E. This highly efficient gene editing process enables the engineered T-cells to evade NK cell and alloresponsive T-cell attacks and extend their persistence and antitumor activity in the presence of cytotoxic levels of NK cell in vivo and in vitro, respectively. This scaffold could enable the broad use of universal CAR T-cells in allogeneic settings and holds great promise for clinical applications.

Targeting cellular senescence to combat cancer and aging

Senescence is a complex cellular process that is implicated in various physiological and pathological processes. It is characterized by a stable state of cell growth arrest and by a secretome of diverse pro‐inflammatory factors, chemokines and growth factors. In this review, we summarize the context‐dependent role of cellular senescence in ageing and in age‐related diseases, such as cancer. We discuss current approaches to targeting senescence to develop therapeutic strategies to combat cancer and to promote healthy ageing, and we outline our vision for future research directions for senescence‐based interventions in these fields.

Neoadjuvant Immunotherapy in Gastrointestinal Cancers - The New Standard of Care?

The development of immune checkpoint inhibitors (ICI) offers novel treatment possibilities for solid cancers, with the crucial benefit of providing higher cure rates. These agents have become part of standard treatments in the metastatic and adjuvant setting for select cancers, such as melanoma, non-small cell lung cancer (NSCLC) or urological malignancies. Currently, there is ample clinical interest in employing ICI in a neoadjuvant setting with a curative intent. This approach is especially supported by the scientific rationale that ICI primarily stimulate the host immune system to eradicate tumor cells, rather than being inherently cytotoxic. Aside from tumor downstaging, neoadjuvant immunotherapy offers the potential of an in situ cancer vaccination, leading to a systemic adjuvant immunological effect after tumor resection. Moreover, preclinical data clearly demonstrate a synergistic effect of ICI with radiotherapy (RT), chemoradiotherapy (CRT) or chemotherapy (ChT). This review harmonizes preclinical concepts with real world data (RWD) in the field of neoadjuvant ICI in gastrointestinal (GI) cancers and discusses their limitations. We believe this is a crucial approach, since up to now, neoadjuvant strategies have been primarily developed by clinicians, whereas the advances in immunotherapy primarily originate from preclinical research. Currently there is limited published data on neoadjuvant ICI in GI cancers, even though neoadjuvant treatments including RT, CRT or ChT are frequently employed in locally advanced/oligometastatic GI cancers (i.e. rectal, pancreatic, esophagus, stomach, etc.). Utilizing established therapies in combination with ICI provides an abundance of opportunities for innovative treatment regimens to further improve survival rates.

Senescence induction dictates response to chemo- and immunotherapy in preclinical models of ovarian cancer

Efforts to understand and find new treatment options for high-grade serous ovarian cancer (HGSOC) have been confounded by a paucity of immune-competent models that accurately reflect the genetics and biology of the disease. Here, we leverage somatic tissue engineering to develop a fast and flexible immune-competent mouse model of HGSOC and reveal mechanistic insights into factors that dictate the response of ovarian tumors to conventional chemotherapy and immune checkpoint blockade. Our results identify a genotype-dependent therapy-induced senescence program that mediates sensitivity and resistance to first line chemotherapy and point to strategies to harness the senescence program to sensitize ovarian tumors to immune checkpoint blockade.

High-grade serous ovarian carcinoma (HGSOC) is a cancer with dismal prognosis due to the limited effectiveness of existing chemo- and immunotherapies. To elucidate mechanisms mediating sensitivity or resistance to these therapies, we developed a fast and flexible autochthonous mouse model based on somatic introduction of HGSOC-associated genetic alterations into the ovary of immunocompetent mice using tissue electroporation. Tumors arising in these mice recapitulate the metastatic patterns and histological, molecular, and treatment response features of the human disease. By leveraging these models, we show that the ability to undergo senescence underlies the clinically observed increase in sensitivity of homologous recombination (HR)–deficient HGSOC tumors to platinum-based chemotherapy. Further, cGas/STING-mediated activation of a restricted senescence-associated secretory phenotype (SASP) was sufficient to induce immune infiltration and sensitize HR-deficient tumors to immune checkpoint blockade. In sum, our study identifies senescence propensity as a predictor of therapy response and defines a limited SASP profile that appears sufficient to confer added vulnerability to concurrent immunotherapy and, more broadly, provides a blueprint for the implementation of electroporation-based mouse models to reveal mechanisms of oncogenesis and therapy response in HGSOC.

AKT1 Is Required for a Complete Palbociclib-Induced Senescence Phenotype in BRAF-V600E-Driven Human Melanoma

Cellular senescence is a carefully regulated process of proliferative arrest accompanied by functional and morphologic changes. Senescence allows damaged cells to avoid neoplastic proliferation; however, the induction of the senescence-associated secretory phenotype (SASP) can promote tumor growth. The complexity of senescence may limit the efficacy of anti-neoplastic agents, such as CDK4/6 inhibitors (Cdk4/6i), that induce a senescence-like state in tumor cells. The AKT kinase family, which contains three isoforms that play both unique and redundant roles in cancer progression, is commonly hyperactive in many cancers including melanoma and has been implicated in the regulation of senescence. To interrogate the role of AKT isoforms in Cdk4/6i-induced cellular senescence, we generated isoform-specific AKT knockout human melanoma cell lines. We found that the CDK4/6i Palbociclib induced a form of senescence in these cells that was dependent on AKT1. We then evaluated the activity of the cGAS-STING pathway, recently implicated in cellular senescence, finding that cGAS-STING function was dependent on AKT1, and pharmacologic inhibition of cGAS had little effect on senescence. However, we found SASP factors to require NF-κB function, in part dependent on a stimulatory phosphorylation of IKKα by AKT1. In summary, we provide the first evidence of a novel, isoform-specific role for AKT1 in therapy-induced senescence in human melanoma cells acting through NF-κB but independent of cGAS.

Chromatin basis of the senescence-associated secretory phenotype

Cellular senescence is a stable cell growth arrest. Senescent cells are metabolically active, as exemplified by the secretion of inflammatory cytokines, chemokines, and growth factors, which is termed senescence-associated secretory phenotype (SASP). The SASP exerts a range of functions in both normal health and pathology, which is possibly best characterized in cancers and physical aging. Recent studies demonstrated that chromatin is instrumental in regulating the SASP both through nuclear transcription and via the innate immune cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in the cytoplasm. Here, we will review these regulatory mechanisms, with an emphasis on most recent developments in the field. We will highlight the challenges and opportunities in developing intervention approaches, such as targeting chromatin regulatory mechanisms, to alter the SASP as an emerging approach to combat cancers and achieve healthy aging.

Transcriptome-based stemness indices analysis reveals platinum-based chemo-theraputic response indicators in advanced-stage serous ovarian cancer

Serous ovarian cancer (SOC) is a main histological subtype of ovarian cancer, in which cancer stem cells (CSC) are responsible for its chemoresistance. However, the underlying modulation mechanisms of chemoresistance led by cancer stemness are still undefined. We aimed to investigate potential drug-response indicators among stemness-associated biomarkers in advanced SOC samples. The mRNA expression-based stemness index (mRNAsi) of The Cancer Genome Atlas (TCGA) was evaluated and corrected by tumor purity. Weighted gene co-expression network analysis (WGCNA) was utilized to explore the gene modules and key genes involved in stemness characteristics. We found that mRNAsi and corrected mRNAsi scores were both greater in tumors of Grade 3 and 4 than that of Grade 1 and 2. Forty-two key genes were obtained from the most significant mRNAsi-related gene module. Functional annotation revealed that these key genes were mainly involved in the mitotic division. Thirteen potential platinum-response indicators were selected from the genes enriched to platinum-response associated pathways. Among them, we identified 11 genes with prognostic value of progression-free survival (PFS) in advanced SOC patients treated with platinum and 7 prognostic genes in patients treated with a combination of platinum and taxol. The expressions of the 13 key genes were also validated between platinum-resistant and -sensitive SOC samples of advanced stages in two Gene Expression Omnibus (GEO) datasets. The results revealed that CDC20 was a potential platinum-sensitivity indicator in advanced SOC. These findings may provide a new insight for chemotherapies in advanced SOC patients clinically.

Senescence-Induced Chemoresistance in Triple Negative Breast Cancer and Evolution-Based Treatment Strategies

Triple negative breast cancer (TNBC) is classically treated with combination chemotherapies. Although, initially responsive to chemotherapies, TNBC patients frequently develop drug-resistant, metastatic disease. Chemotherapy resistance can develop through many mechanisms, including induction of a transient growth-arrested state, known as the therapy-induced senescence (TIS). In this paper, we will focus on chemoresistance in TNBC due to TIS. One of the key characteristics of senescent cells is a complex secretory phenotype, known as the senescence-associated secretory proteome (SASP), which by prompting immune-mediated clearance of senescent cells maintains tissue homeostasis and suppresses tumorigenesis. However, in cancer, particularly with TIS, senescent cells themselves as well as SASP promote cellular reprograming into a stem-like state responsible for the emergence of drug-resistant, aggressive clones. In addition to chemotherapies, outcomes of recently approved immune and DNA damage-response (DDR)-directed therapies are also affected by TIS, implying that this a common strategy used by cancer cells for evading treatment. Although there has been an explosion of scientific research for manipulating TIS for prevention of drug resistance, much of it is still at the pre-clinical stage. From an evolutionary perspective, cancer is driven by natural selection, wherein the fittest tumor cells survive and proliferate while the tumor microenvironment influences tumor cell fitness. As TIS seems to be preferred for increasing the fitness of drug-challenged cancer cells, we will propose a few tactics to control it by using the principles of evolutionary biology. We hope that with appropriate therapeutic intervention, this detrimental cellular fate could be diverted in favor of TNBC patients.

Overcoming the senescence-associated secretory phenotype (SASP): a complex mechanism of resistance in the treatment of cancer

Senescence is a cellular state in which cells undergo persistent cell cycle arrest in response to nonlethal stress. In the treatment of cancer, senescence induction is a potent method of suppressing tumour cell proliferation. In spite of this, senescent cancer cells and adjacent nontransformed cells of the tumour microenvironment can remain metabolically active, resulting in paradoxical secretion of pro-inflammatory factors, collectively termed the senescence-associated secretory phenotype (SASP). The SASP plays a critical role in tumorigenesis, affecting numerous processes including invasion, metastasis, epithelial-to-mesenchymal transition (EMT) induction, therapy resistance and immunosuppression. With increasing evidence, it is becoming clear that cell type, tissue of origin and the primary cellular stressor are key determinants in how the SASP will influence tumour development and progression, including whether it will be pro- or antitumorigenic. In this review, we will focus on recent evidence regarding therapy-induced senescence (TIS) from anticancer agents, including chemotherapy, radiation, immunotherapy, and targeted therapies, and how each therapy can trigger the SASP, which in turn influences treatment efficacy. We will also discuss novel pharmacological manipulation of senescent cancer cells and the SASP, which offers an exciting and contemporary approach to cancer therapeutics. With future research, these adjuvant options may help to mitigate many of the negative side effects and protumorigenic roles that are currently associated with TIS in cancer.