SASP mediates chemoresistance and tumor-initiating-activity of mesothelioma cells

Multi-omics and single cell characterization of cancer immunosenescence landscape

Cellular senescence (CS) is closely related to tumor progression. However, the studies about CS genes across human cancers have not explored the relationship between cancer senescence signature and telomere length. Additionally, single-cell analyses have not revealed the evolutionary trends of malignant cells and immune cells at the CS level. We defined a CS-associated signature, called "senescence signature", and found that patients with higher senescence signature had worse prognosis. Higher senescence signature was related to older age, higher genomic instability, longer telomeres, increased lymphocytic infiltration, higher pro-tumor immune infiltrates (Treg cells and MDSCs), and could predict responses to immune checkpoint inhibitor therapy. Single-cell analysis further reveals malignant cells and immune cells share a consistent evolutionary trend at the CS level. MAPK signaling pathway and apoptotic processes may play a key role in CS, and senescence signature may effectively predict sensitivity of MEK1/2 inhibitors, ERK1/2 inhibitors and BCL-2 family inhibitors. We also developed a new CS prediction model of cancer survival and established a portal website to apply this model ( https://bio-pub.shinyapps.io/cs_nomo/ ).

Celastrol mediates CAV1 to attenuate pro-tumorigenic effects of senescent cells

BACKGROUND

Cellular senescence is an emerging hallmark of cancers, primarily fuels cancer progression by expressing senescence-associated secretory phenotype (SASP). Caveolin-1 (CAV1) is a key mediator of cell senescence. Previous studies from our group have evidenced that the expression of CAV1 is downregulated by Celastrol (CeT).

PURPOSE

To investigate the impact of CeT on cellular senescence and its subsequent influence on post-senescence-driven invasion, migration, and stemness of clear cell renal cell carcinoma (ccRCC).

STUDY DESIGN AND METHODS

The expression levels of CAV1, canonical senescence markers, and markers associated with epithelial-mesenchymal transition (EMT) and stemness in clinical samples were assessed through Pearson correlation analysis. Senescent cell models were induced using DOX, and their impact on migration, invasion, and stemness was evaluated. The effects of CeT treatment on senescent cells and their pro-tumorigenic effects were examined. Subsequently, the underlying mechanism of CeT were explored using lentivirus transfection and CRISPR/Cas9 technology to silence CAV1.

RESULTS

In human ccRCC clinical samples, the expression of the canonical senescence markers p53, p21, and p16 are associated with ccRCC progression. Senescent cells facilitated migration, invasion, and enhanced stemness in both ccRCC cells and ccRCC tumor-bearing mice. As expected, CeT treatment reduced senescence markers (p16, p53, p21, SA-β-gal) and SASP factors (IL6, IL8, CXCL12), alleviating cell cycle arrest. However, it did not restore the proliferation of senescent cells. Additionally, CeT suppressed senescence-driven migration, invasion, and stemness. Further investigations into the underlying mechanism demonstrated that CAV1 is a critical mediator of cell senescence and represents a potential target for CeT to attenuate cellular senescence.

CONCLUSIONS

This study presents a pioneering investigation into the intricate interplay between cellular senescence and ccRCC progression. We unveil a novel mechanism of CeT to mitigate cellular senescence by downregulating CAV1, thereby inhibiting the migration, invasion and stemness of ccRCC driven by senescent cells. These findings provide valuable insights into the underlying mechanisms of CeT and its potential as a targeted therapeutic approach for alleviating the aggressive phenotypes associated with senescent cells in ccRCC.

Cytolethal Distending Toxin Modulates Cell Differentiation and Elicits Epithelial to Mesenchymal Transition

BACKGROUND

The bacterial genotoxin, cytolethal distending toxin (CDT), causes DNA damage in host cells, a risk factor for carcinogenesis. Previous studies have shown that CDT induces phenotypes reminiscent of epithelial to mesenchymal transition (EMT), a process involved in cancer initiation and progression.

METHODS

We investigated different steps of EMT in response to Helicobacter hepaticus CDT and its active CdtB subunit using in vivo and in vitro models.

RESULTS

Most of the steps of the EMT process were induced by CDT/CdtB and observed throughout the study in murine and epithelial cell culture models. CdtB induced cell-cell junction disassembly, causing individualization of cells and acquisition of a spindle-like morphology. The key transcriptional regulators of EMT (SNAIL and ZEB1) and some EMT markers were upregulated at both RNA and protein levels in response to CDT/CdtB. CdtB increased the expression and proteolytic activity of matrix metalloproteinases, as well as cell migration. A range of these results were confirmed in Helicobacter hepaticus-infected and xenograft murine models. In addition, colibactin, a genotoxic metabolite produced by Escherichia coli, induced EMT-like effects in cell culture.

CONCLUSIONS

Overall, these data show that infection with genotoxin-producing bacteria elicits EMT process activation, supporting their role in tumorigenesis.

Effects of senescence on the tumour microenvironment and response to therapy

Cellular senescence is a state of durable cell arrest that has been identified both in vitro and in vivo. It is associated with profound changes in gene expression and a specific secretory profile that includes pro-inflammatory cytokines, growth factors and matrix-remodelling enzymes, referred to as the senescence-associated secretory phenotype (SASP). In cancer, senescence can have anti- or pro-tumour effects. On one hand, it can inhibit tumour progression in a cell autonomous manner. On the other hand, senescence can also promote tumour initiation, progression, metastatic dissemination and resistance to therapy in a paracrine manner. Therefore, despite efforts to target senescence as a potential strategy to inhibit tumour growth, senescent cancer and microenvironmental cells can eventually lead to uncontrolled proliferation and aggressive tumour phenotypes. This can happen either through overcoming senescence growth arrest or through SASP-mediated effects in adjacent tumour cells. This review will discuss how senescence affects the tumour microenvironment, including extracellular matrix remodelling, the immune system and the vascular compartment, to promote tumourigenesis, metastasis and resistance to DNA-damaging therapies. It will also discuss current approaches used in the field to target senescence: senolytics, improving the immune clearance of senescent cells and targeting the SASP.

Adaptations of membrane trafficking in cancer and tumorigenesis

Membrane trafficking, a fundamental cellular process encompassing the transport of molecules to specific organelles, endocytosis at the plasma membrane and protein secretion, is crucial for cellular homeostasis and signalling. Cancer cells adapt membrane trafficking to enhance their survival and metabolism, and understanding these adaptations is vital for improving patient responses to therapy and identifying therapeutic targets. In this Review, we provide a concise overview of major membrane trafficking pathways and detail adaptations in these pathways, including COPII-dependent endoplasmic reticulum (ER)-to-Golgi vesicle trafficking, COPI-dependent retrograde Golgi-to-ER trafficking and endocytosis, that have been found in cancer. We explore how these adaptations confer growth advantages or resistance to cell death and conclude by discussing the potential for utilising this knowledge in developing new treatment strategies and overcoming drug resistance for cancer patients.

Mesothelioma-Associated Fibroblasts Modulate the Response of Mesothelioma Patient-Derived Organoids to Chemotherapy via Interleukin-6

Malignant pleural mesothelioma (MPM) remains an incurable disease. This is partly due to the lack of experimental models that fully recapitulate the complexity and heterogeneity of MPM, a major challenge for therapeutic management of the disease. In addition, the contribution of the MPM microenvironment is relevant for the adaptive response to therapy. We established mesothelioma patient-derived organoid (mPDO) cultures from MPM pleural effusions and tested their response to pemetrexed and cisplatin. We aimed to evaluate the contribution of mesothelioma-associated fibroblasts (MAFs) to the response to pemetrexed and cisplatin (P+C). Organoid cultures were obtained from eight MPM patients using specific growth media and conditions to expand pleural effusion-derived cells. Flow cytometry was used to verify the similarity of the organoid cultures to the original samples. MAFs were isolated and co-cultured with mPDOs, and the addition of MAFs reduced the sensitivity of mPDOs to P+C. Organoid formation and expression of cancer stem cell markers such as ABCG2, NANOG, and CD44 were altered by conditioned media from treated MAFs. We identified IL-6 as the major contributor to the attenuated response to chemotherapy. IL-6 secretion by MAFs is correlated with increased resistance of mPDOs to pemetrexed and cisplatin.

Emerging Roles of Vitamin B12 in Aging and Inflammation

Vitamin B12 (cobalamin) is an essential nutrient for humans and animals. Metabolically active forms of B12-methylcobalamin and 5-deoxyadenosylcobalamin are cofactors for the enzymes methionine synthase and mitochondrial methylmalonyl-CoA mutase. Malfunction of these enzymes due to a scarcity of vitamin B12 leads to disturbance of one-carbon metabolism and impaired mitochondrial function. A significant fraction of the population (up to 20%) is deficient in vitamin B12, with a higher rate of deficiency among elderly people. B12 deficiency is associated with numerous hallmarks of aging at the cellular and organismal levels. Cellular senescence is characterized by high levels of DNA damage by metabolic abnormalities, increased mitochondrial dysfunction, and disturbance of epigenetic regulation. B12 deficiency could be responsible for or play a crucial part in these disorders. In this review, we focus on a comprehensive analysis of molecular mechanisms through which vitamin B12 influences aging. We review new data about how deficiency in vitamin B12 may accelerate cellular aging. Despite indications that vitamin B12 has an important role in health and healthy aging, knowledge of the influence of vitamin B12 on aging is still limited and requires further research.

Tumor-Associated Senescent Macrophages, Their Markers, and Their Role in Tumor Microenvironment

Tumor-associated macrophages (TAMs) are an important component of the tumor microenvironment (TME) and the most abundant population of immune cells infiltrating a tumor. TAMs can largely determine direction of anti-tumor immune response by promoting it or, conversely, contribute to formation of an immunosuppressive TME that allows tumors to evade immune control. Through interactions with tumor cells or other cells in the microenvironment and, as a result of action of anti-cancer therapy, macrophages can enter senescence. In this review, we have attempted to summarize information available in the literature on the role of senescent macrophages in tumors. With the recent development of senolytic therapeutic strategies aimed at removing senescent cells from an organism, it seems important to discuss functions of the senescent macrophages and potential role of the senolytic drugs in reprogramming TAMs to enhance anti-tumor immune response and improve efficacy of cancer treatment.

Immune cell senescence and exhaustion promote the occurrence of liver metastasis in colorectal cancer by regulating epithelial-mesenchymal transition

BACKGROUND

Liver metastasis (LM) stands as a primary cause of mortality in metastatic colorectal cancer (mCRC), posing a significant impediment to long-term survival benefits from targeted therapy and immunotherapy. However, there is currently a lack of comprehensive investigation into how senescent and exhausted immune cells contribute to LM.

METHODS

We gathered single-cell sequencing data from primary colorectal cancer (pCRC) and their corresponding matched LM tissues from 16 mCRC patients. In this study, we identified senescent and exhausted immune cells, performed enrichment analysis, cell communication, cell trajectory, and cell-based in vitro experiments to validate the results of single-cell multi-omics. This process allowed us to construct a regulatory network explaining the occurrence of LM. Finally, we utilized weighted gene co-expression network analysis (WGCNA) and 12 machine learning algorithms to create prognostic risk model.

RESULTS

We identified senescent-like myeloid cells (SMCs) and exhausted T cells (TEXs) as the primary senescent and exhausted immune cells. Our findings indicate that SMCs and TEXs can potentially activate transcription factors downstream via ANGPTL4-SDC1/SDC4, this activation plays a role in regulating the epithelial-mesenchymal transition (EMT) program and facilitates the development of LM, the results of cell-based in vitro experiments have provided confirmation of this conclusion. We also developed and validated a prognostic risk model composed of 12 machine learning algorithms.

CONCLUSION

This study elucidates the potential molecular mechanisms underlying the occurrence of LM from various angles through single-cell multi-omics analysis in CRC. It also constructs a network illustrating the role of senescent or exhausted immune cells in regulating EMT.

RSK3 switches cell fate: from stress-induced senescence to malignant progression

BACKGROUND

TGFβ induces several cell phenotypes including senescence, a stable cell cycle arrest accompanied by a secretory program, and epithelial-mesenchymal transition (EMT) in normal epithelial cells. During carcinogenesis cells lose the ability to undergo senescence in response to TGFβ but they maintain an EMT, which can contribute to tumor progression. Our aim was to identify mechanisms promoting TGFβ-induced senescence escape.

METHODS

In vitro experiments were performed with primary human mammary epithelial cells (HMEC) immortalized by hTert. For kinase library screen and modulation of gene expression retroviral transduction was used. To characterize gene expression, RNA microarray with GSEA analysis and RT-qPCR were used. For protein level and localization, Western blot and immunofluorescence were performed. For senescence characterization crystal violet assay, Senescence Associated-β-Galactosidase activity, EdU staining were conducted. To determine RSK3 partners FLAG-baited immunoprecipitation and mass spectrometry-based proteomic analyses were performed. Proteosome activity and proteasome enrichment assays were performed. To validate the role of RSK3 in human breast cancer, analysis of METABRIC database was performed. Murine intraductal xenografts using MCF10DCIS.com cells were carried out, with histological and immunofluorescence analysis of mouse tissue sections.

RESULTS

A screen with active kinases in HMECs upon TGFβ treatment identified that the serine threonine kinase RSK3, or RPS6KA2, a kinase mainly known to regulate cancer cell death including in breast cancer, reverted TGFβ-induced senescence. Interestingly, RSK3 expression decreased in response to TGFβ in a SMAD3-dependent manner, and its constitutive expression rescued SMAD3-induced senescence, indicating that a decrease in RSK3 itself contributes to TGFβ-induced senescence. Using transcriptomic analyses and affinity purification coupled to mass spectrometry-based proteomics, we unveiled that RSK3 regulates senescence by inhibiting the NF-κΒ pathway through the decrease in proteasome-mediated IκBα degradation. Strikingly, senescent TGFβ-treated HMECs display features of epithelial to mesenchymal transition (EMT) and during RSK3-induced senescence escaped HMECs conserve EMT features. Importantly, RSK3 expression is correlated with EMT and invasion, and inversely correlated with senescence and NF-κΒ in human claudin-low breast tumors and its expression enhances the formation of breast invasive tumors in the mouse mammary gland.

CONCLUSIONS

We conclude that RSK3 switches cell fate from senescence to malignancy in response to TGFβ signaling.

High-Throughput Drug Screening Revealed That Ciclopirox Olamine Can Engender Gastric Cancer Stem-like Cells

Cancer stem cells (CSCs) are relevant therapeutic targets for cancer treatment. Still, the molecular circuits behind CSC characteristics are not fully understood. The low number of CSCs can sometimes be an obstacle to carrying out assays that explore their properties. Thus, increasing CSC numbers via small molecule-mediated cellular reprogramming appears to be a valid alternative tool. Using the SORE6-GFP reporter system embedded in gastric non-CSCs (SORE6-), we performed a high-throughput image-based drug screen with 1200 small molecules to identify compounds capable of converting SORE6- to SORE6+ (CSCs). Here, we report that the antifungal agent ciclopirox olamine (CPX), a potential candidate for drug repurposing in cancer treatment, is able to reprogram gastric non-CSCs into cancer stem-like cells via activation of SOX2 expression and increased expression of C-MYC, HIF-1α, KLF4, and HMGA1. This reprogramming depends on the CPX concentration and treatment duration. CPX can also induce cellular senescence and the metabolic shift from oxidative phosphorylation (OXPHOS) to glycolysis. We also disclose that the mechanism underlying the cellular reprogramming is similar to that of cobalt chloride (CoCl2), a hypoxia-mimetic agent.

Interrogating colorectal cancer metastasis to liver: a search for clinically viable compounds and mechanistic insights in colorectal cancer Patient Derived Organoids

BACKGROUND

Approximately 20-50% of patients presenting with localized colorectal cancer progress to stage IV metastatic disease (mCRC) following initial treatment and this is a major prognostic determinant. Here, we have interrogated a heterogeneous set of primary colorectal cancer (CRC), liver CRC metastases and adjacent liver tissue to identify molecular determinants of the colon to liver spreading. Screening Food and Drug Administration (FDA) approved drugs for their ability to interfere with an identified colon to liver metastasis signature may help filling an unmet therapeutic need.

METHODS

RNA sequencing of primary colorectal cancer specimens vs adjacent liver tissue vs synchronous and asynchronous liver metastases. Pathways enrichment analyses. The Library of Integrated Network-based Cellular Signatures (LINCS)-based and Connectivity Map (CMAP)-mediated identification of FDA-approved compounds capable to interfere with a 22 gene signature from primary CRC and liver metastases. Testing the identified compounds on CRC-Patient Derived Organoid (PDO) cultures. Microscopy and Fluorescence Activated Cell Sorting (FACS) based analysis of the treated PDOs.

RESULTS

We have found that liver metastases acquire features of the adjacent liver tissue while partially losing those of the primary tumors they derived from. We have identified a 22-gene signature differentially expressed among primary tumors and metastases and validated in public databases. A pharmacogenomic screening for FDA-approved compounds capable of interfering with this signature has been performed. We have validated some of the identified representative compounds in CRC-Patient Derived Organoid cultures (PDOs) and found that pentoxyfilline and, to a minor extent, dexketoprofen and desloratadine, can variably interfere with number, size and viability of the CRC -PDOs in a patient-specific way. We explored the pentoxifylline mechanism of action and found that pentoxifylline treatment attenuated the 5-FU elicited increase of ALDHhigh cells by attenuating the IL-6 mediated STAT3 (tyr705) phosphorylation.

CONCLUSIONS

Pentoxifylline synergizes with 5-Fluorouracil (5-FU) in attenuating organoid formation. It does so by interfering with an IL-6-STAT3 axis leading to the emergence of chemoresistant ALDHhigh cell subpopulations in 5-FU treated PDOs. A larger cohort of CRC-PDOs will be required to validate and expand on the findings of this proof-of-concept study.

Mitochondria in cell senescence: A Friend or Foe?

Cell senescence denotes cell growth arrest in response to continuous replication or stresses damaging DNA or mitochondria. Mounting research suggests that cell senescence attributes to aging-associated failing organ function and diseases. Conversely, it participates in embryonic tissue maturation, wound healing, tissue regeneration, and tumor suppression. The acute or chronic properties and microenvironment may explain the double faces of senescence. Senescent cells display unique characteristics. In particular, its mitochondria become elongated with altered metabolomes and dynamics. Accordingly, mitochondria reform their function to produce more reactive oxygen species at the cost of low ATP production. Meanwhile, destructed mitochondrial unfolded protein responses further break the delicate proteostasis fostering mitochondrial dysfunction. Additionally, the release of mitochondrial damage-associated molecular patterns, mitochondrial Ca²⁺ overload, and altered NAD⁺ level intertwine other cellular organelle strengthening senescence. These findings further intrigue researchers to develop anti-senescence interventions. Applying mitochondrial-targeted antioxidants reduces cell senescence and mitigates aging by restoring mitochondrial function and attenuating oxidative stress. Metformin and caloric restriction also manifest senescent rescuing effects by increasing mitochondria efficiency and alleviating oxidative damage. On the other hand, Bcl2 family protein inhibitors eradicate senescent cells by inducing apoptosis to facilitate cancer chemotherapy. This review describes the different aspects of mitochondrial changes in senescence and highlights the recent progress of some anti-senescence strategies.

Cellular Senescence, a Novel Area of Investigation for Metastatic Diseases

Metastasis is a systemic condition and the major challenge among cancer types, as it can lead to multiorgan vulnerability. Recently, attention has been drawn to cellular senescence, a complex stress response condition, as a factor implicated in metastatic dissemination and outgrowth. Here, we examine the current knowledge of the features required for cells to invade and colonize secondary organs and how senescent cells can contribute to this process. First, we describe the role of senescence in placentation, itself an invasive process which has been linked to higher rates of invasive cancers. Second, we describe how senescent cells can contribute to metastatic dissemination and colonization. Third, we discuss several metabolic adaptations by which senescent cells could promote cancer survival along the metastatic journey. In conclusion, we posit that targeting cellular senescence may have a potential therapeutic efficacy to limit metastasis formation.

The role of cellular senescence and SASP in tumour microenvironment

Cellular senescence refers to a state of irreversible cell cycle arrest that can be induced by various cellular stresses and is known to play a pivotal role in tumour suppression. While senescence-associated growth arrest can inhibit the proliferation of cancer-prone cells, the altered secretory profile of senescent cells, termed the senescence-associated secretory phenotype, can contribute to the microenvironment that promotes tumour development. Although the senescence-associated secretory phenotype and its effects on tumorigenesis are both highly context dependent, mechanisms underlying such diversity are becoming better understood, thereby allowing the creation of new strategies to effectively target the senescence-associated secretory phenotype and senescent cells for cancer therapy. In this review, we discuss the current knowledge on cellular senescence and the senescence-associated secretory phenotype to develop a structural understanding of their roles in the tumour microenvironment and provide perspectives for future research, including the possibility of senotherapy for the treatment of cancer.

The Potential of Senescence as a Target for Developing Anticancer Therapy

Senescence occurs in response to various stimuli. Senescence has attracted attention because of its potential use in anticancer therapy as it plays a tumor-suppressive role. It also promotes tumorigeneses and therapeutic resistance. Since senescence can induce therapeutic resistance, targeting senescence may help to overcome therapeutic resistance. This review provides the mechanisms of senescence induction and the roles of the senescence-associated secretory phenotype (SASP) in various life processes, including therapeutic resistance and tumorigenesis. The SASP exerts pro-tumorigenic or antitumorigenic effects in a context-dependent manner. This review also discusses the roles of autophagy, histone deacetylases (HDACs), and microRNAs in senescence. Many reports have suggested that targeting HDACs or miRNAs could induce senescence, which, in turn, could enhance the effects of current anticancer drugs. This review presents the view that senescence induction is a powerful method of inhibiting cancer cell proliferation.

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

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

Phosphoinositide species and filamentous actin formation mediate engulfment by senescent tumor cells

Cancer cells survive chemotherapy and cause lethal relapse by entering a senescent state that facilitates expression of many phagocytosis/macrophage-related genes that engender a novel cannibalism phenotype. We used biosensors and live-cell imaging to reveal the basic steps and mechanisms of engulfment by senescent human and mouse tumor cells. We show filamentous actin in predator cells was localized to the prey cell throughout the process of engulfment. Biosensors to various phosphoinositide (PI) species revealed increased concentration and distinct localization of predator PI(4) P and PI(4,5)P2 at the prey cell during early stages of engulfment, followed by a transient burst of PI(3) P before and following internalization. PIK3C2B, the kinase responsible for generating PI(3)P, was required for complete engulfment. Inhibition or knockdown of Clathrin, known to associate with PIK3C2B and PI(4,5)P2, severely impaired engulfment. In sum, our data reveal the most fundamental cellular processes of senescent cell engulfment, including the precise localizations and dynamics of actin and PI species throughout the entire process.

Palbociclib Enhances Migration and Invasion of Cancer Cells via Senescence-Associated Secretory Phenotype-Related CCL5 in Non-Small-Cell Lung Cancer

Palbociclib is the first CDK4/6 inhibitor approved by FDA and has been studied in many types of cancer. However, some studies showed that it could induce epithelial-mesenchymal transition (EMT) of cancer cells. To test the effect of palbociclib on non-small-cell lung cancer (NSCLC) cells, we treated NSCLC cells with different concentrations of palbociclib and detected its effects via MTT, migration and invasion assays, and apoptosis test. Further RNA sequencing was performed in the cells treated with 2 μM palbociclib or control. And Gene Ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA), and protein-protein interaction network (PPI) were analyzed to explore the mechanism of palbociclib. The results showed that palbociclib significantly inhibited the growth of NSCLC cells and promoted apoptosis of cells, however, enhanced the migration and invasion abilities of cancer cells. RNA sequencing showed that cell cycle, inflammation-/immunity-related signaling, cytokine-cytokine receptor interaction, and cell senescence pathways were involved in the process, and CCL5 was one of the significantly differential genes affected by palbociclib. Further experiments showed that blocking CCL5-related pathways could reverse the malignant phenotype induced by palbociclib. Our results revealed that palbociclib-induced invasion and migration might be due to senescence-associated secretory phenotype (SASP) rather than EMT and suggested that SASP could act as a potential target to potentiate the antitumor effects of palbociclib in cancer treatment.

Senescence of Tumor Cells in Anticancer Therapy—Beneficial and Detrimental Effects

Cellular senescence process results in stable cell cycle arrest, which prevents cell proliferation. It can be induced by a variety of stimuli including metabolic stress, DNA damage, telomeres shortening, and oncogenes activation. Senescence is generally considered as a process of tumor suppression, both by preventing cancer cells proliferation and inhibiting cancer progression. It can also be a key effector mechanism for many types of anticancer therapies such as chemotherapy and radiotherapy, both directly and through bioactive molecules released by senescent cells that can stimulate an immune response. Senescence is characterized by a senescence-associated secretory phenotype (SASP) that can have both beneficial and detrimental impact on cancer progression. Despite the negatives, attempts are still being made to use senescence to fight cancer, especially when it comes to senolytics. There is a possibility that a combination of prosenescence therapy—which targets tumor cells and causes their senescence—with senotherapy—which targets senescent cells, can be promising in cancer treatment. This review provides information on cellular senescence, its connection with carcinogenesis and therapeutic possibilities linked to this process.

Global research trends in atherosclerosis: A bibliometric and visualized study

Background

Increasing evidence has spurred a considerable evolution of concepts related to atherosclerosis, prompting the need to provide a comprehensive view of the growing literature. By retrieving publications in the Web of Science Core Collection (WoSCC) of Clarivate Analytics, we conducted a bibliometric analysis of the scientific literature on atherosclerosis to describe the research landscape.

Methods

A search was conducted of the WoSCC for articles and reviews serving exclusively as a source of information on atherosclerosis published between 2012 and 2022. Microsoft Excel 2019 was used to chart the annual productivity of research relevant to atherosclerosis. Through CiteSpace and VOSviewer, the most prolific countries or regions, authors, journals, and resource-, intellectual-, and knowledge-sharing in atherosclerosis research, as well as co-citation analysis of references and keywords, were analyzed.

Results

A total of 20,014 publications were retrieved. In terms of publications, the United States remains the most productive country (6,390, 31,93%). The most publications have been contributed by Johns Hopkins Univ (730, 3.65%). ALVARO ALONSO produced the most published works (171, 0.85%). With a betweenness centrality of 0.17, ERIN D MICHOS was the most influential author. The most prolific journal was identified as Atherosclerosis (893, 4.46%). Circulation received the most co-citations (14,939, 2.79%). Keywords with the ongoing strong citation bursts were “nucleotide-binding oligomerization (NOD), Leucine-rich repeat (LRR)-containing protein (NLRP3) inflammasome,” “short-chain fatty acids (SCFAs),” “exosome,” and “homeostasis,” etc.

Conclusion

The research on atherosclerosis is driven mostly by North America and Europe. Intensive research has focused on the link between inflammation and atherosclerosis, as well as its complications. Specifically, the NLRP3 inflammasome, interleukin-1β, gut microbiota and SCFAs, exosome, long non-coding RNAs, autophagy, and cellular senescence were described to be hot issues in the field.

Therapy-induced senescence promotes breast cancer cells plasticity by inducing Lipocalin-2 expression

The acquisition of novel detrimental cellular properties following exposure to cytotoxic drugs leads to aggressive and metastatic tumors that often translates into an incurable disease. While the bulk of the primary tumor is eliminated upon exposure to chemotherapeutic treatment, residual cancer cells and non-transformed cells within the host can engage a stable cell cycle exit program named senescence. Senescent cells secrete a distinct set of pro-inflammatory factors, collectively termed the senescence-associated secretory phenotype (SASP). Upon exposure to the SASP, cancer cells undergo cellular plasticity resulting in increased proliferation, migration and epithelial-to-mesenchymal transition. The molecular mechanisms by which the SASP regulates these pro-tumorigenic features are poorly understood. Here, we report that breast cancer cells exposed to the SASP strongly upregulate Lipocalin-2 (LCN2). Furthermore, we demonstrate that LCN2 is critical for SASP-induced increased migration in breast cancer cells, and its inactivation potentiates the response to chemotherapeutic treatment in mouse models of breast cancer. Finally, we show that neoadjuvant chemotherapy treatment leads to LCN2 upregulation in residual human breast tumors, and correlates with worse overall survival. These findings provide the foundation for targeting LCN2 as an adjuvant therapeutic approach to prevent the emergence of aggressive tumors following chemotherapy.

Anti-Tumorigenic Effect of a Novel Derivative of 2-Hydroxyoleic Acid and the Endocannabinoid Anandamide on Neuroblastoma Cells

Modulation of the endogenous cannabinoid system has been suggested as a potential anticancer strategy. In the search for novel and less toxic therapeutic options, structural modifications of the endocannabinoid anandamide and the synthetic derivative of oleic acid, Minerval (HU-600), were done to obtain 2-hydroxy oleic acid ethanolamide (HU-585), which is an HU-600 derivative with the anandamide side chain. We showed that treatment of SK-N-SH neuroblastoma cells with HU-585 induced a better anti-tumorigenic effect in comparison to HU-600 as evidenced by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide assay, colony-forming assay, and migration assay. Moreover, HU-585 demonstrated pro-apoptotic properties shown by increased levels of activated caspase-3 following treatment and a better senescence induction effect in comparison to HU-600, as demonstrated by increased activity of lysosomal β-galactosidase. Finally, we observed that combined treatment of HU-585 with the senolytic drugs ABT-263 in vitro, and ABT-737 in vivo resulted in enhanced anti-proliferative effects and reduced neuroblastoma xenograft growth in comparison to treatment with HU-585 alone. Based on these results, we suggest that HU-585 is a pro-apoptotic and senescence-inducing compound, better than HU-600. Hence, it may be a beneficial option for the treatment of resistant neuroblastoma especially when combined with senolytic drugs that enhance its anti-tumorigenic effects.

Cellular senescence and the tumor 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.

Targeting tumor cell senescence and polyploidy as potential therapeutic strategies

Senescence is a unique state of growth arrest that develops in response to a plethora of cellular stresses, including replicative exhaustion, oxidative injury, and genotoxic insults. Senescence has been implicated in the pathogenesis of multiple aging-related pathologies, including cancer. In cancer, senescence plays a dual role, initially acting as a barrier against tumor progression by enforcing a durable growth arrest in premalignant cells, but potentially promoting malignant transformation in neighboring cells through the secretion of pro-tumorigenic drivers. Moreover, senescence is induced in tumor cells upon exposure to a wide variety of conventional and targeted anticancer drugs (termed Therapy-Induced Senescence-TIS), representing a critical contributing factor to therapeutic outcomes. As with replicative or oxidative senescence, TIS manifests as a complex phenotype of macromolecular damage, energetic dysregulation, and altered gene expression. Senescent cells are also frequently polyploid. In vitro studies have suggested that polyploidy may confer upon senescent tumor cells the ability to escape from growth arrest, thereby providing an additional avenue whereby tumor cells escape the lethality of anticancer treatment. Polyploidy in tumor cells is also associated with persistent energy production, chromatin remodeling, self-renewal, stemness and drug resistance - features that are also associated with escape from senescence and conversion to a more malignant phenotype. However, senescent cells are highly heterogenous and can present with variable phenotypes, where polyploidy is one component of a complex reversion process. Lastly, emerging efforts to pharmacologically target polyploid tumor cells might pave the way towards the identification of novel targets for the elimination of senescent tumor cells by the incorporation of senolytic agents into cancer therapeutic strategies.

Dexamethasone: Insights into Pharmacological Aspects, Therapeutic Mechanisms, and Delivery Systems

Dexamethasone (DEX) has been widely used to treat a variety of diseases, including autoimmune diseases, allergies, ocular disorders, cancer, and, more recently, COVID-19. However, DEX usage is often restricted in the clinic due to its poor water solubility. When administered through a systemic route, it can elicit severe side effects, such as hypertension, peptic ulcers, hyperglycemia, and hydro-electrolytic disorders. There is currently much interest in developing efficient DEX-loaded nanoformulations that ameliorate adverse disease effects inhibiting advancements in scientific research. Various nanoparticles have been developed to selectively deliver drugs without destroying healthy cells or organs in recent years. In the present review, we have summarized some of the most attractive applications of DEX-loaded delivery systems, including liposomes, polymers, hydrogels, nanofibers, silica, calcium phosphate, and hydroxyapatite. This review provides our readers with a broad spectrum of nanomedicine approaches to deliver DEX safely.

The application of cancer stem cell model in malignant mesothelioma

The high mortality rate of malignant pleural mesothelioma led to study the mechanisms for chemoresistance. The cancer stem cell (CSC) model has been proposed to explain chemoresistance. CSCs are characterized by self-renewal capacity, that is detected through tumor-initiating cell assays. As in other malignancies, many studies sought to identify surface markers to isolate CSCs from malignant mesothelioma. Other studies characterized malignant mesothelioma CSCs for the expression of specific genes involved in stemness and the expression of proteins involved in chemoresistance. However, the main methods to characterize isolated CSCs include sphere formation, invasiveness, tumor-initiating capacity and expression of specific surface markers. The better knowledge of malignant mesothelioma CSCs allowed exploring new potential targets to develop specific treatments.

Preclinical studies for improving radiosensitivity of non-small cell lung cancer cell lines by combining glutaminase inhibition and senolysis

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Abnormal glutaminolysis is common in cancer cells with mutations.

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The glutaminase inhibitor CB839 enhanced radiosensitivity in A549 and H460 cells.

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Glutaminolysis inhibition led to an increase in cell senescence.

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The Bcl-2 family inhibitor ABT-263 induced transition from senescence to apoptosis.

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Combined glutaminolysis and senolysis may improve radiosensitivity in cancer cells.

Glutamine metabolism, known as glutaminolysis, is abnormally activated in many cancer cells with KRAS or BRAF mutations or active c-MYC. Glutaminolysis plays an important role in the proliferation of cancer cells with oncogenic mutations. In this study, we characterized radiation-induced cell death, which was enhanced by glutaminolysis inhibition in non-small cell lung cancer A549 and H460 cell lines with KRAS mutation. A clonogenic survival assay revealed that treatment with a glutaminase inhibitor, CB839, enhanced radiosensitivity. X-irradiation increased glutamate production, mitochondrial oxygen consumption, and ATP production, whereas CB839 treatment suppressed these effects. The data suggest that the enhancement of glutaminolysis-dependent energy metabolism for ATP production is important for survival after X-irradiation. Evaluation of the cell death phenotype revealed that glutaminolysis inhibitory treatment with CB839 or a low-glutamine medium significantly promoted the proliferation of β-galactosidase-positive and IL-6/IL-8 secretory cells among X-irradiated tumor cells, corresponding to an increase in the senescent cell population. Furthermore, treatment with ABT263, a Bcl-2 family inhibitor, transformed senescent cells into apoptotic cells. The findings suggest that combination treatment with a glutaminolysis inhibitor and a senolytic drug is useful for efficient radiotherapy.

Impact of Cancer Stem Cells on Therapy Resistance in Gastric Cancer

Gastric cancer (GC) is the fourth leading cause of cancer death worldwide, with an average 5-year survival rate of 32%, being of 6% for patients presenting distant metastasis. Despite the advances made in the treatment of GC, chemoresistance phenomena arise and promote recurrence, dissemination and dismal prognosis. In this context, gastric cancer stem cells (gCSCs), a small subset of cancer cells that exhibit unique characteristics, are decisive in therapy failure. gCSCs develop different protective mechanisms, such as the maintenance in a quiescent state as well as enhanced detoxification procedures and drug efflux activity, that make them insusceptible to current treatments. This, together with their self-renewal capacity and differentiation ability, represents major obstacles for the eradication of this disease. Different gCSC regulators have been described and used to isolate and characterize these cell populations. However, at the moment, no therapeutic strategy has achieved the effective targeting of gCSCs. This review will focus on the properties of cancer stem cells in the context of therapy resistance and will summarize current knowledge regarding the impact of the gCSC regulators that have been associated with GC chemoradioresistance.

Activatable senoprobes and senolytics: Novel strategies to detect and target senescent cells

Pharmacologically active compounds that manipulate cellular senescence (senotherapies) have recently shown great promise in multiple pre-clinical disease models, and some of them are now being tested in clinical trials. Despite promising proof-of-principle evidence, there are known on- and off-target toxicities associated with these compounds, and therefore more refined and novel strategies to improve their efficacy and specificity for senescent cells are being developed. Preferential release of drugs and macromolecular formulations within senescent cells has been predominantly achieved by exploiting one of the most widely used biomarkers of senescence, the increase in lysosomal senescence-associated β-galactosidase (SA-β-gal) activity, a common feature of most reported senescent cell types. Galacto-conjugation is a versatile therapeutic and detection strategy to facilitate preferential targeting of senescent cells by using a variety of existing formulations, including modular systems, nanocarriers, activatable prodrugs, probes, and small molecules. We discuss the benefits and drawbacks of these specific senescence targeting tools and how the strategy of galacto-conjugation might be utilised to design more specific and sophisticated next-generation senotherapeutics, as well as theranostic agents. Finally, we discuss some innovative strategies and possible future directions for the field.

p53 Signaling on Microenvironment and Its Contribution to Tissue Chemoresistance

Chemoresistance persists as a significant, unresolved clinical challenge in many cancer types. The tumor microenvironment, in which cancer cells reside and interact with non-cancer cells and tissue structures, has a known role in promoting every aspect of tumor progression, including chemoresistance. However, the molecular determinants of microenvironment-driven chemoresistance are mainly unknown. In this review, we propose that the TP53 tumor suppressor, found mutant in over half of human cancers, is a crucial regulator of cancer cell-microenvironment crosstalk and a prime candidate for the investigation of microenvironment-specific modulators of chemoresistance. Wild-type p53 controls the secretion of factors that inhibit the tumor microenvironment, whereas altered secretion or mutant p53 interfere with p53 function to promote chemoresistance. We highlight resistance mechanisms promoted by mutant p53 and enforced by the microenvironment, such as extracellular matrix remodeling and adaptation to hypoxia. Alterations of wild-type p53 extracellular function may create a cascade of spatial amplification loops in the tumor tissue that can influence cellular behavior far from the initial oncogenic mutation. We discuss the concept of chemoresistance as a multicellular/tissue-level process rather than intrinsically cellular. Targeting p53-dependent crosstalk mechanisms between cancer cells and components of the tumor environment might disrupt the waves of chemoresistance that spread across the tumor tissue, increasing the efficacy of chemotherapeutic agents.

Senescent tumor cells: an overlooked adversary in the battle against cancer

Senescent cells in cancer tissue, including senescent fibroblasts and macrophages, have been reported to increase the malignant potency of cancer cells by secreting senescence-associated secretory phenotype (SASP). Otherwise, Senescence of tumor cells has been believed to inhibit tumor growth by halting the massive proliferation and increasing the chances of immune clearance. In particular, senescent tumor cells (STCs) have been thought that they rarely exist in carcinomas because oncogene-induced senescence needs to be overcome for protumorigenic cells to become malignant. However, recent studies have revealed that a considerable number of STCs are present in cancer tissue, even in metastatic sites. In fact, STCs are widely involved in cancer progression by leading to collective invasion and building a cytokine barrier to protect nonsenescent tumor cells from immune attack. Furthermore, therapy-induced STCs can induce tumor progression and recurrence by increasing stemness. However, obscure causative factors and their heterogeneity in various cancers make it difficult to establish the physiological role of STCs. Here, we summarize and review the current knowledge of the pathophysiology and role of STCs. We also outline the current status of therapeutic strategies for directly removing STCs or modulating the SASPs to maximize the positive functions of STCs while suppressing the negative functions.

Construction and validation of a novel aging-related gene signature and prognostic nomogram for predicting the overall survival in ovarian cancer

BACKGROUND

Ovarian cancer (OC) is the most lethal gynecological malignancy. The objective of this study was to establish and validate an individual aging-related gene signature and a clinical nomogram that can powerfully predict independently the overall survival rate of patients with ovarian cancer.

METHODS

Data on transcriptomic profile and relevant clinical information were retrieved from The Cancer Genome Atlas (TCGA) database as a training group, and the same data from three public Gene Expression Omnibus (GEO) databases as validation groups. Univariate Cox regression analysis, lasso regression analysis, and multiple multivariate Cox analysis were analyzed sequentially to select the genes to be included in the aging-associated signature. A risk scoring model was established and verified, the predictive value of the model was evaluated, and a clinical nomogram was established.

RESULTS

We found eight genes that were most relevant to prognosis and constructed an eight-mRNA signature. Based on the model, each OC patient's risk score was able to be calculated and patients were split into groups of low and high risks with a distinct outcome. Survival analysis confirmed that the outcome of patients in the high-risk group was dramatically shorter than that of those in the low-risk group, and the eight-mRNA signature can be considered as a powerful and independent predictor that could predict the outcome of OC patient. Additionally, the risk score and age can be used to construct a clinical nomogram as a simpler tool for predicting prognosis. We also explored the association between the risk score and immunity and drug sensitivity.

CONCLUSION

This study suggested that the aging-related gene signature could be used as an intervention point and latent prognostic predictor in OC, which may provide new perceptions for postoperative treatment strategies.

Mesothelioma Malignancy and the Microenvironment: Molecular Mechanisms

Several studies have reported that cellular and soluble components of the tumor microenvironment (TME) play a key role in cancer-initiation and progression. Considering the relevance and the complexity of TME in cancer biology, recent research has focused on the investigation of the TME content, in terms of players and informational exchange. Understanding the crosstalk between tumor and non-tumor cells is crucial to design more beneficial anti-cancer therapeutic strategies. Malignant pleural mesothelioma (MPM) is a complex and heterogenous tumor mainly caused by asbestos exposure with few treatment options and low life expectancy after standard therapy. MPM leukocyte infiltration is rich in macrophages. Given the failure of macrophages to eliminate asbestos fibers, these immune cells accumulate in pleural cavity leading to the establishment of a unique inflammatory environment and to the malignant transformation of mesothelial cells. In this inflammatory landscape, stromal and immune cells play a driven role to support tumor development and progression via a bidirectional communication with tumor cells. Characterization of the MPM microenvironment (MPM-ME) may be useful to understand the complexity of mesothelioma biology, such as to identify new molecular druggable targets, with the aim to improve the outcome of the disease. In this review, we summarize the known evidence about the MPM-ME network, including its prognostic and therapeutic relevance.

Insights into Intra-Tumoral Heterogeneity: Transcriptional Profiling of Chemoresistant MPM Cell Subpopulations Reveals Involvement of NFkB and DNA Repair Pathways and Contributes a Prognostic Signature

Chemoresistance is a hallmark of malignant pleural mesothelioma (MPM) management and the expression of ALDH1A3 is responsible for the survival and activity of MPM chemoresistant cell subpopulations (ALDH^bright cells). We enriched mesothelioma ALDH^bright cells to near homogeneity by FACS sorting and an Aldefluor assay and performed unbiased Affymetrix gene expression profiling. Viability and ELISA assays were used to rule out significant apoptosis in the sorted cell subpopulations and to assess target engagement by butein. Statistical analysis of the results, pathway enrichment and promoter enrichment were employed for the generation of the data. Q-RTPCR was used to validate a subset of the identified, modulated mRNAs In this work, we started from the observation that the mRNA levels of the ALDH1A3 isoform could prognostically stratify MPM patients. Thus, we purified MPM ALDH^bright cells from NCI-H2595 cells and interrogated their gene expression (GES) profile. We analyzed the GES of the purified cells at both a steady state and upon treatment with butein (a multifunctional tetrahydroxy-chalcone), which abates the ALDH^bright cell number, thereby exerting chemo-sensitizing effects in vitro and in vivo. We identified 924 genes modulated in a statistically significant manner as a function of ALDH status and of the response to the inhibitor. Pathway and promoter enrichment identified the molecular determinant of high ALDH status and how butein treatment altered the molecular portrait of those chemoresistant cell subpopulations. Further, we unraveled an eighteen-gene signature with high prognostic significance for MPM patients, and showed that most of the identified prognostic contributors escaped the analysis of unfractionated samples. This work proves that digging into the unexplored field of intra-tumor heterogeneity (ITH) by working at the cell subpopulation level may provide findings of prognostic relevance, in addition to mechanistic insights into tumor resistance to therapy.

Arachidonic acid drives adaptive responses to chemotherapy-induced stress in malignant mesothelioma

Background High resistance to therapy and poor prognosis characterizes malignant pleural mesothelioma (MPM). In fact, the current lines of treatment, based on platinum and pemetrexed, have limited impact on the survival of MPM patients. Adaptive response to therapy-induced stress involves complex rearrangements of the MPM secretome, mediated by the acquisition of a senescence-associated-secretory-phenotype (SASP). This fuels the emergence of chemoresistant cell subpopulations, with specific gene expression traits and protumorigenic features. The SASP-driven rearrangement of MPM secretome takes days to weeks to occur. Thus, we have searched for early mediators of such adaptive process and focused on metabolites differentially released in mesothelioma vs mesothelial cell culture media, after treatment with pemetrexed.

METHODS

Mass spectrometry-based (LC/MS and GC/MS) identification of extracellular metabolites and unbiased statistical analysis were performed on the spent media of mesothelial and mesothelioma cell lines, at steady state and after a pulse with pharmacologically relevant doses of the drug. ELISA based evaluation of arachidonic acid (AA) levels and enzyme inhibition assays were used to explore the role of cPLA2 in AA release and that of LOX/COX-mediated processing of AA. QRT-PCR, flow cytometry analysis of ALDH expressing cells and 3D spheroid growth assays were employed to assess the role of AA at mediating chemoresistance features of MPM. ELISA based detection of p65 and IkBalpha were used to interrogate the NFkB pathway activation in AA-treated cells.

RESULTS

We first validated what is known or expected from the mechanism of action of the antifolate. Further, we found increased levels of PUFAs and, more specifically, arachidonic acid (AA), in the transformed cell lines treated with pemetrexed. We showed that pharmacologically relevant doses of AA tightly recapitulated the rearrangement of cell subpopulations and the gene expression changes happening in pemetrexed -treated cultures and related to chemoresistance. Further, we showed that release of AA following pemetrexed treatment was due to cPLA2 and that AA signaling impinged on NFkB activation and largely affected anchorage-independent, 3D growth and the resistance of the MPM 3D cultures to the drug.

CONCLUSIONS

AA is an early mediator of the adaptive response to pem in chemoresistant MPM and, possibly, other malignancies.

The Contribution of Physiological and Accelerated Aging to Cancer Progression Through Senescence-Induced Inflammation

Senescent cells are found to accumulate in aged individuals, as well as in cancer patients that receive chemotherapeutic treatment. Although originally believed to halt cancer progression due to their characteristic growth arrest, senescent cells remain metabolically active and secrete a combination of inflammatory agents, growth factors and proteases, collectively known as the senescence-associated secretory phenotype (SASP). In this review, we discuss the contribution of senescent cells to cancer progression through their ability to alter cancer cells’ properties and to generate a microenvironment that promotes tumor growth. Furthermore, recent evidence suggests that senescent cells are able resume proliferation and drive cancer relapse, pointing to the use of senolytics and SASP modulators as a potential approach to prevent tumor resurgence following treatment cessation. Thus, a better understanding of the hallmarks of senescence and the impact of the SASP will allow the development of improved targeted therapeutic strategies to leverage vulnerabilities associated with this cellular state.

Delineating the Switch between Senescence and Apoptosis in Cervical Cancer Cells under Ciclopirox Treatment

Simple Summary

Novel treatment options for cervical cancer are urgently required. Ciclopirox (CPX), an iron chelator, has shown promising anti-tumorigenic potential in several preclinical tumor models, including cervical cancer cells. In these cells, CPX can induce apoptosis, a form of cell death, or senescence, an irreversible cellular growth arrest. These different phenotypic outcomes may influence therapy response. Here, we show that the decision of cervical cancer cells to induce apoptosis or senescence is strongly dependent on glucose availability: CPX induces apoptosis under limited glucose availability, whereas under increased glucose supply, CPX treatment results in senescence. Further, we link the pro-apoptotic and pro-senescent activities of CPX to its capacity to block oxidative phosphorylation and to chelate iron, respectively. In addition, we show that the combined treatment of CPX and glycolysis inhibitors blocks the proliferation of cervical cancer cells in a synergistic manner. Collectively, we provide novel insights into the anti-proliferative activities of CPX in cervical cancer cells, elucidate the cellular decision between apoptosis or senescence induction, and provide a rationale to combine CPX with glycolysis inhibitors.

Abstract

The iron-chelating drug ciclopirox (CPX) may possess therapeutic potential for cancer treatment, including cervical cancer. As is observed for other chemotherapeutic drugs, CPX can induce senescence or apoptosis in cervical cancer cells which could differently affect their therapy response. The present study aims to gain insights into the determinants which govern the switch between senescence and apoptosis in cervical cancer cells. We performed proteome analyses, proliferation studies by live-cell imaging and colony formation assays, senescence and apoptosis assays, and combination treatments of CPX with inhibitors of oxidative phosphorylation (OXPHOS) or glycolysis. We found that CPX downregulates OXPHOS factors and facilitates the induction of apoptosis under limited glucose availability, an effect which is shared by classical OXPHOS inhibitors. Under increased glucose availability, however, CPX-induced apoptosis is prevented and senescence is induced, an activity which is not exerted by classical OXPHOS inhibitors, but by other iron chelators. Moreover, we show that the combination of CPX with glycolysis inhibitors blocks cervical cancer proliferation in a synergistic manner. Collectively, our results reveal that the phenotypic response of cervical cancer cells towards CPX is strongly dependent on glucose availability, link the pro-apoptotic and pro-senescent activities of CPX to its bifunctionality as an OXPHOS inhibitor and iron chelator, respectively, and provide a rationale for combining CPX with glycolysis inhibitors.

Cellular senescence in cancer: from mechanisms to detection

Senescence refers to a cellular state featuring a stable cell-cycle arrest triggered in response to stress. This response also involves other distinct morphological and intracellular changes including alterations in gene expression and epigenetic modifications, elevated macromolecular damage, metabolism deregulation and a complex pro-inflammatory secretory phenotype. The initial demonstration of oncogene-induced senescence in vitro established senescence as an important tumour-suppressive mechanism, in addition to apoptosis. Senescence not only halts the proliferation of premalignant cells but also facilitates the clearance of affected cells through immunosurveillance. Failure to clear senescent cells owing to deficient immunosurveillance may, however, lead to a state of chronic inflammation that nurtures a pro-tumorigenic microenvironment favouring cancer initiation, migration and metastasis. In addition, senescence is a response to post-therapy genotoxic stress. Therefore, tracking the emergence of senescent cells becomes pivotal to detect potential pro-tumorigenic events. Current protocols for the in vivo detection of senescence require the analysis of fixed or deep-frozen tissues, despite a significant clinical need for real-time bioimaging methods. Accuracy and efficiency of senescence detection are further hampered by a lack of universal and more specific senescence biomarkers. Recently, in an attempt to overcome these hurdles, an assortment of detection tools has been developed. These strategies all have significant potential for clinical utilisation and include flow cytometry combined with histo- or cytochemical approaches, nanoparticle-based targeted delivery of imaging contrast agents, OFF-ON fluorescent senoprobes, positron emission tomography senoprobes and analysis of circulating SASP factors, extracellular vesicles and cell-free nucleic acids isolated from plasma. Here, we highlight the occurrence of senescence in neoplasia and advanced tumours, assess the impact of senescence on tumorigenesis and discuss how the ongoing development of senescence detection tools might improve early detection of multiple cancers and response to therapy in the near future.

Androgen-deprivation induced senescence in prostate cancer cells is permissive for the development of castration-resistance but susceptible to senolytic therapy

Prostate cancer (PCa) is one of the leading causes of cancer-related deaths in men. Although androgen deprivation therapies (ADT) and antiandrogens confer increased survival rates, most patients eventually develop castration resistant disease (CRPC). Previous studies have shown that these treatments have limited cytotoxicity, and instead, promote tumor cell growth arrest. We show here that PCa cells grown in either charcoal-stripped serum or exposed to the antiandrogen, bicalutamide, undergo a senescent growth arrest marked by morphological changes, upregulated senescence-associated-β-galactosidase (SA-β-Gal), cathepsin D accumulation, and expression of the senescence-associated secretory phenotype (SASP). The senescent growth arrest is, however, transient, as cells can resume proliferation upon restoration of normo-androgenic conditions. Intriguingly, enrichment for senescent cells confirmed that ADT-induced senescent cells recover their proliferative capacity, even under prolonged androgen deprivation, and form androgen-independent outgrowths. Transplantation of the enriched senescent population into castrated, syngeneic mice confirmed that senescent cells escape the growth arrest and form castration-resistant tumors in vivo. Outgrowth from senescence was associated with increased expression of constitutively active androgen receptor splice variants, a common mechanism of resistance to ADT. Finally, the selective elimination of senescent PCa cells following ADT in vitro by the senolytic navitoclax (ABT-263) interfered with the development of androgen-independent outgrowth. Taken together, these data support the premise that ADT-induced senescence is a transient cell state from which CRPC populations can emerge, identifying senescence as a potential driver of disease progression. Furthermore, it is feasible that senolytic therapy to eliminate senescent PCa cells could delay disease recurrence and/or progression to androgen independence.

Cellular Plasticity: A Route to Senescence Exit and Tumorigenesis

Senescence is a dynamic, multistep program that results in permanent cell cycle arrest and is triggered by developmental or environmental, oncogenic or therapy-induced stress signals. Senescence is considered as a tumor suppressor mechanism that prevents the risk of neoplastic transformation by restricting the proliferation of damaged cells. Cells undergoing senescence sustain important morphological changes, chromatin remodeling and metabolic reprogramming, and secrete pro-inflammatory factors termed senescence-associated secretory phenotype (SASP). SASP activation is required for the clearance of senescent cells by innate immunity. Therefore, escape from senescence and the associated immune editing would be a prerequisite for tumor initiation and progression as well as therapeutic resistance. One of the possible mechanisms for overcoming senescence could be the acquisition of cellular plasticity resulting from the accumulation of genomic alterations and genetic and epigenetic reprogramming. The modified composition of the SASP produced by these reprogrammed cancer cells would create a permissive environment, allowing their immune evasion. Additionally, the SASP produced by cancer cells could enhance the cellular plasticity of neighboring cells, thus hindering their recognition by the immune system. Here, we propose a comprehensive review of the literature, highlighting the role of cellular plasticity in the pro-tumoral activity of senescence in normal cells and in the cancer context.

Profile of soluble factors in pleural effusions predict prognosis in mesothelioma

BACKGROUND:

Pleural mesothelioma is a deadly asbestos induced cancer. Less than 10% of mesothelioma patients survive 5 years post diagnosis. However survival can range from a few months to a number of years. Accurate prediction of survival is important for patients to plan for their remaining life, and for clinicians to determine appropriate therapy. One unusual feature of mesothelioma is that patients frequently present with tumor-associated pleural effusions early in the course of the disease.

OBJECTIVE:

To study whether cells and molecules present in pleural effusions provide prognostic information for mesothelioma.

METHODS:

We profiled the cellular constituents and concentrations of 40 cytokines, chemokines and cellular factors (collectively “soluble factors”) involved in inflammatory and immune signalling pathways in pleural effusion samples from 50 mesothelioma patients.

Associations with survival were evaluated by Cox proportional hazards regression methods. Results for the two soluble factors most significantly and independently associated with survival were validated in an independent set of samples (n= 51) using a separate assay system.

RESULTS:

Survival analysis revealed that IL8, IL2Ra (CD25) and PF4 were independent determinants of a more negative prognosis in mesothelioma patients, independent of other known prognostic factors. Lipocalin2 and IL4 were associated with better prognosis.

CONCLUSIONS:

This study demonstrates that pleural effusions rich in a range of soluble factors are associated with poor prognosis. These findings will enhance our ability to prognosticate outcomes in mesothelioma patients.

The Paradoxical Role of Cellular Senescence in Cancer

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

Role of Clusterin/NF-κB in the secretion of senescence-associated secretory phenotype in Cr(VI)-induced premature senescent L-02 hepatocytes

Hexavalent chromium [Cr(VI)] and its compounds have caused serious environmental pollution and health damage. Senescent cells can actively change the surrounding environment by secreting some factors, which are called senescence associated secretory phenotype (SASP). Our previous work has confirmed that premature senescent hepatocytes induced by Cr(VI) expressed high level of Clusterin (CLU) and secrete interleukin-6 (IL-6) and IL-8. CLU is involved in the regulation of tumor development and drug resistance, but whether CLU regulates SASP components and participates in Cr(VI)-induced malignant transformation is unclear. In this study we demonstrated that Cr(VI) induced the secretion of tumor promoting components of SASP such as IL-6, IL-8, and granulocyte-macrophage colony stimulating factor (GM-CSF) in senescent L-02 hepatocytes, while the levels of the anti-tumor components of SASP such as chemokine (c-x-c motif) ligand-1 (CXCL-1) and monocyte chemoattractant protein-1 (MCP-1) were not altered. CLU shRNA interference significantly reduced the levels of IL-6, IL-8, and GM-CSF in the culture medium of senescent cells, suggesting CLU may regulate SASP. The NF-κB inhibitor PDTC significantly alleviated Cr(VI)-induced increase of IL-6, IL-8, and GM-CSF, confirming that NF-κB can regulate the tumor promoting components of SASP. CLU shRNA interference aggravated the inhibitory effect of PDTC on SASP secretion, indicating that CLU regulated the secretion of SASP in Cr(VI)-induced senescent hepatocytes through the NF-κB signaling. We speculated that SASP secreted by Cr(VI)-induced premature senescent hepatocytes was tightly related to the carcinogenic effect of Cr(VI). Therefore, elucidation of upstream regulatory mechanism of SASP is of great significance. In addition to further clarifying the carcinogenic mechanisms associated with Cr(VI), we could also seek out new targets for treatment of Cr(VI)-related cancer.

Senescent cells in cancer therapy: why and how to remove them

Cellular senescence is a stress response that imposes a growth arrest on cancer and nonmalignant cells during cancer therapy. By secreting a plethora of proinflammatory factors collectively termed the senescence-associated secretory phenotype (SASP), therapy-induced senescent cells can promote tumorigenesis. Moreover, the SASP from senescent cells is also able to drive therapy resistance and mediate many adverse effects of cancer therapy. Because senescent cell production often occurs during cancer therapy, it is important to carefully consider these potential detrimental effects. Senotherapy, which refers to selective removal of senescent cells, has been proposed as a promising adjuvant approach to eliminate the adverse effects of senescent cells. Thus, in this review we summarize in detail the mechanisms by which senescent cells contribute to tumorigenesis and therapeutic resistance. Also, we thoroughly discuss the potential strategies regarding how to effectively circumvent the undesirable effects of therapy-induced senescent cells.

Prognostic Significance of JMJD3 Expression in Pleural Mesotheliomas

Pleural mesothelioma is a disease associated with asbestos exposure and patients often have poor prognosis. Biomarkers that can stratify tumours more efficiently are much sought after to enable more personalized treatment options and predict prognosis. Jumonji domain-containing protein D3 (JMJD3) has variable expression in a range of tumours. However, there has been much discordance in the immunohistochemical labelling of JMJD3 between cancers at different sites and ambiguity exists regarding its functional significance. Recent evidence suggests that although nuclear expression of JMJD3 has a demethylase role in most cancers, there are also demethylase-independent actions of JMJD3 that need to be explored including its cytoplasmic expression. We analysed JMJD3 labelling in 99 pleural mesothelioma tissues and correlated nuclear and cytoplasmic expression with survival outcomes. We found that low nuclear and high cytoplasmic expression were associated with poor survival outcomes in our cohort (p = 0.014 and p = 0.041, respectively). Additionally, we found that low nuclear expression of JMJD3 was frequent in the sarcomatoid subtype (p < 0.001). Finally, we showed that cytoplasmic labelling is an independent prognostic marker of poor survival. Our cohort only contained a small number of tumours with high cytoplasmic expression of JMJD3, and a larger cohort study may provide clearer stratification.

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.

Mechanisms of cancer stem cell senescence: Current understanding and future perspectives

Cancer stem cells (CSCs) are a small population of heterogeneous tumor cells with the capacity of self-renewal and aberrant differentiation for immortality and divergent lineages of cancer cells. In contrast to bulky tumor cells, CSCs remain less differentiated and resistant to therapy even when targeted with tissue-specific antigenic markers. This makes CSCs responsible for not only tumor initiation, development, but also tumor recurrence. Emerging evidence suggests that CSCs can undergo cell senescence, a non-proliferative state of cells in response to stress. While cell senescence attenuates tumor cell proliferation, it is commonly regarded as a tumor suppressive mechanism. However, mounting research indicates that CSC senescence also provides these cells with the capacity to evade cytotoxic effects from cancer therapy, exacerbating cancer relapse and metastasis. Recent studies demonstrate that senescence drives reprogramming of cancer cell toward stemness and promotes CSC generation. In this review, we highlight the origin, heterogeneity and senescence regulatory mechanisms of CSCs, the complex relationship between CSC senescence and tumor therapy, and the recent beneficial effects of senotherapy on eliminating senescent tumor cells.

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.