Cellular senescence: a promising strategy for cancer therapy

Functional circuits of LYL1 controlled by supraphysiological androgen in prostate cancer cells to regulate cell senescence

BACKGROUND

Prostate cancer (PCa) is a public health problem mostly reported in developed countries. The androgen receptor (AR) regulates the development and physiological function of normal prostate as well as the proliferation of cancerous prostate tissue. Treatment with supraphysiological androgen levels (SAL) is used in bipolar androgen therapy and inhibits PCa growth, suggesting SAL induces a tumor suppressive program. It was shown that SAL induces cellular senescence, in PCa cell lines, human tumor samples and in xenografted mouse tumor model.

METHODS

Transcriptome and ChIP-seq analysis, PCa spheroids, knockdown (KD), co-immunoprecipitation, qRT-PCR, immune detection, in situ histochemistry.

RESULTS

Here we show that LYL1 is upregulated by the clock gene BHLHE40 in both C4-2 and LNCaP cells and mediates SAL-induced cellular senescence. LYL1 is a transcriptional co-factor with oncogenic activity in leukemia. However, analysis of a large cohort of PCa patients shows that LYL1 expression is reduced during PCa development and reduced expression is significantly associated with reduced overall survival. SAL induces the expression of LYL1 through upregulation of BHLHE40. On the other hand, the KD of LYL1 enhances BHLHE40 expression via a negative feedback loop including p27kip1. Regulatory feedback loops were identified by rescue experiments. Functional analysis revealed that KD of BHLHE40 reduces whereas LYL1 KD enhances p27kip1 levels. The KD of p27kip1 suggests that this cell cycle inhibitor is a mediator of cellular senescence by the BHLHE40 - LYL1 regulatory loop. Interestingly, ChIP-seq data revealed recruitment of both AR and BHLHE40 to the LYL1 gene indicating that LYL1 is a novel direct target of both factors. Furthermore, RNA-seq data from C4-2 cells suggests that LYL1 and BHLHE40 encompass a large overlap of genes by SAL suggesting a co-regulatory activity controlled by androgens. In line with this, co-immunoprecipitation suggests LYL1 is in a complex with BHLHE40 and the AR.

CONCLUSIONS

Three novel feed-back loops and a novel AR- BHLHE40 / LYL1 -p27kip1 axis has been identified mediating cellular senescence in PCa cells.

Targeting the p53-p21 axis in liver cancer: Linking cellular senescence to tumor suppression and progression

Liver cancer is a major health epidemic worldwide, mainly due to its high mortality rates and limited treatment options. The association of cellular senescence to tumorigenesis and the cancer hallmarks remains a subject of interest in cancer biology. The p53-p21 signalling axis is an important regulator in restoring the cell's balance by supporting tumor suppression and tumorigenesis in liver cancer. We review the novel molecular mechanisms that p53 and its downstream effector, p21, employ to induce cellular senescence, making it last longer, and halt the proliferation of damaged hepatocytes to become tumorous cells. We also examine how dysregulation of this pathway contributes to HCC pathogenesis, proliferation, survival, acquired resistance to apoptosis, and increased invasiveness. Furthermore, we comprehensively describe the molecular cross-talk between the p53-p21 signalling axis and major cell cycle signalling pathways, including Wnt/β-catenin, PI3K/Akt, and TGF-β in liver cancer and provide an overview of promising candidates for chemoprevention and future therapeutic strategies. This review article explores the roles of the p53-p21 pathway in liver cancer, examining its function in promoting cellular senescence under normal conditions and its potential role in cancer progression. It also highlights novel therapeutic drugs and drug targets within the pathway and discusses the implications for treatment strategies and prognosis in liver cancer.

Treatment of a mutant KRAS lung cancer cell line with polyisoprenylated cysteinyl amide inhibitors activates the MAPK pathway, inhibits cell migration and induces apoptosis

KRAS mutations are the most common oncogenic mutations in lung adenocarcinoma in Black Americans. Polyisoprenylated Cysteinyl amide Inhibitors (PCAIs) constitute a group of potential cancer therapy agents that we designed to specifically disrupt and suppress hyperactive G-protein signaling, such as that caused by mutated RAS proteins. Here we determine the effects of PCAIs on the viability, G-protein levels, downstream mediators, and apoptosis-related proteins on the KRAS-mutated, Black American-derived lung adenocarcinoma cell line, NCI-H23. Of the 17 PCAIs tested, compounds NSL-YHJ-2-27 and NSL-YHJ-2-46 showed the most potency with EC50 values of 2.7 and 3.3 μM, respectively. Western blotting was used to determine the effect of the PCAIs on the phosphorylation levels of MAPK pathway enzymes. After 48 h exposure to 5 μM of the PCAIs, NSL-YHJ-2-46, the MAPK proteins BRAF, MEK1/2, ERK1/2, and p90RSK were activated through phosphorylation by 90, 190, 150 and 120%, respectively. However, CRAF/RAF1 phosphorylation decreased by 40%, suggesting significant changes in the KRAS/MAPK signaling patterns. Furthermore, 5 μM of NSL-YHJ-2-27 depleted the singly polyisoprenylated monomeric G-proteins RAC 1/2/3 and CDC42 by 77 and 76%, respectively. The depletion of these key cytoskeletal proteins may account for the observed inhibition of cell migration and invasion, and spheroid invasion observed on exposure to NSL-YHJ-2-27 and NSL-YHJ-2-46. Treatment with 5 μM of NSL-YHJ-2-27 suppressed full-length inactive caspase 3 and 7 levels by 72 and 91%, respectively. An analysis of cells treated with the fluorescently labeled active caspase 3/7 irreversible inhibitor, CaspaTagTM Caspase-3/7 in situ reagent revealed a 124% increase in active caspase at 3 μM over controls. These findings clearly show the direct effects of the PCAIs on the RAS signaling pathway. Given the profound increases observed in RPS6KA1/p90RSK phosphorylation, future work will involve a determination whether the proapoptotic isoforms of RPS6KA1/p90RSK are phosphorylated due to the PCAIs treatments. These results support the potential use of the PCAIs as targeted therapies against cancers with KRAS mutations.

Prognostic Significance of SASP-Related Gene Signature of Radiation Therapy in Head and Neck Squamous Cell Carcinoma

In this study, we developed and validated the clinical significance of senescence-associated secretory phenotype (SASP)-related gene signature and explored its association with radiation therapy (RT) in patients with head and neck squamous cell carcinoma (HNSCC). First, we searched the three published review literature associated with SASP and selected all 81 genes to develop SASP-related gene signature. Then, 81 SASP-related genes were adapted to gene expression dataset from The Cancer Genome Atlas (TCGA). Patients with HNSCC of TCGA were classified into clusters 1 and 2 via unsupervised clustering according to SASP-related gene signature. Kaplan-Meier plot survival analysis showed that cluster 1 had a poorer prognosis than cluster 2 in 5-year overall survival and recurrence-free survival. Similarly, cluster 1 showed a worse prognosis than cluster 2 in three validation cohorts (E-MTAB-8588, FHCRC, and KHU). Cox proportional hazards regression observed that the SASP-related signature was an independent prognostic factor for patients with HNSCC. We also established a nomogram using a relevant clinical parameter and a risk score. Time-dependent receiver operating characteristic analysis was carried out to assess the accuracy of the prognostic risk model and nomogram. Senescence SASP-related gene signature was associated with the response to RT. Therefore, subsequent, in vitro experiments further validated the association between SASP-related gene signature and RT in HNSCC. In conclusion, we developed a SASP-related gene signature, which could predict survival of patients with HNSCC, and this gene signature provides new clinical evidence for the accurate diagnosis and targeted RT of HNSCC.

Methods to Investigate the Secretome of Senescent Cells

The word "secretome" was first used to describe the proteins that cells secrete under different circumstances; however, recent studies have proven the existence of other molecules such as RNA and chemical compounds in the secretome. The study of secretome has significance for the diagnosis and treatment of disease as it provides insight into cellular functions, including immune responses, development, and homeostasis. By halting cell division, cellular senescence plays a role in both cancer defense and aging by secreting substances known as senescence-associated secretory phenotypes (SASP). A variety of techniques could be used to analyze the secretome: protein-based approaches like mass spectrometry and protein microarrays, nucleic acid-based methods like RNA sequencing, microarrays, and in silico prediction. Each method offers unique advantages and limitations in characterizing secreted molecules. Top-down and bottom-up strategies for thorough secretome analysis are became possible by mass spectrometry. Understanding cellular function, disease causes, and proper treatment targets is aided by these methodologies. Their approaches, benefits, and drawbacks will all be discussed in this review.

Effect of CDK4/6 Inhibitors on Tumor Immune Microenvironment

Cancer is an abnormal proliferation of cells that is stimulated by cyclin-dependent kinases (CDKs) and defective cell cycle regulation. The essential agent that drive the cell cycle, CDK4/6, would be activated by proliferative signals. Activated CDK4/6 results in the phosphorylation of the neuroblastoma protein (RB) and the release of the transcription factor E2F, which promotes the cell cycle progression. CDK4/6 inhibitor (CDK4/6i) has been currently a research focus, which inhibits the CDK4/6-RB-E2F axis, thereby reducing the cell cycle transition from G1 to S phase and mediating the cell cycle arrest. This action helps achieve an anti-tumor effect. Recent research has demonstrated that CDK4/6i, in addition to contributing to cell cycle arrest, is also essential for the interaction between the tumor cells and the host immune system, i.e., activating the immune system, strengthening the tumor antigen presentation, and reducing the number of regulatory T cells (Treg). Additionally, CDK4/6i would elevate the level of PD-L1, an immunosuppressive factor, in tumor cells, and CDK4/6i in combination with anti-PD-L1 therapy would more effectively reduce the tumor growth. Our results showed that CDK4/6i caused autophagy and senescence in tumor cells. Herein, the impact of CDK4/6i on the immune microenvironment of malignant tumors was mainly focused, as well as their interaction with immune checkpoint inhibitors in affecting anti-tumor immunity.

A review for the impacts of circadian disturbance on urological cancers

Circadian rhythm is an internal timing system and harmonizes a variety of cellular, behavioral, and physiological processes to daily environment. Circadian disturbance caused by altered life style or disrupted sleep patterns inevitably contributes to various disorders. As the rapidly increased cancer occurrences and subsequent tremendous financial burdens, more researches focus on reducing the morbidity rather than treating it. Recently, many epidemiologic studies demonstrated that circadian disturbance was tightly related to the occurrence and development of cancers. For urinary system, numerous clinical researches observed the incidence and progress of prostate cancer were influenced by nightshift work, sleep duration, chronotypes, light exposure, and meal timing, this was also proved by many genetic and fundamental findings. Although the epidemiological studies regarding the relationship between circadian disturbance and kidney/bladder cancers were relative limited, some basic researches still claimed circadian disruption was closely correlated to these two cancers. The role of circadian chemotherapy on cancers of prostate, kidney, and bladder were also explored, however, it has not been regularly recommended considering the limited evidence and poor standard protocols. Finally, the researches for the impacts of circadian disturbance on cancers of adrenal gland, penis, testis were not found at present. In general, a better understanding the relationship between circadian disturbance and urological cancers might help to provide more scientific work schedules and rational lifestyles which finally saving health resource by reducing urological tumorigenesis, however, the underlying mechanisms are complex which need further exploration.

The multifaceted role of Fragile X-Related Protein 1 (FXR1) in cellular processes: an updated review on cancer and clinical applications

RNA-binding proteins (RBPs) modulate the expression level of several target RNAs (such as mRNAs) post-transcriptionally through interactions with unique binding sites in the 3'-untranslated region. There is mounting information that suggests RBP dysregulation plays a significant role in carcinogenesis. However, the function of FMR1 autosomal homolog 1(FXR1) in malignancies is just beginning to be unveiled. Due to the diversity of their RNA-binding domains and functional adaptability, FXR1 can regulate diverse transcript processing. Changes in FXR1 interaction with RNA networks have been linked to the emergence of cancer, although the theoretical framework defining these alterations in interaction is insufficient. Alteration in FXR1 expression or localization has been linked to the mRNAs of cancer suppressor genes, cancer-causing genes, and genes involved in genomic expression stability. In particular, FXR1-mediated gene regulation involves in several cellular phenomena related to cancer growth, metastasis, epithelial-mesenchymal transition, senescence, apoptosis, and angiogenesis. FXR1 dysregulation has been implicated in diverse cancer types, suggesting its diagnostic and therapeutic potential. However, the molecular mechanisms and biological effects of FXR1 regulation in cancer have yet to be understood. This review highlights the current knowledge of FXR1 expression and function in various cancer situations, emphasizing its functional variety and complexity. We further address the challenges and opportunities of targeting FXR1 for cancer diagnosis and treatment and propose future directions for FXR1 research in oncology. This work intends to provide an in-depth review of FXR1 as an emerging oncotarget with multiple roles and implications in cancer biology and therapy.

Effective sequential combined therapy with carboplatin and a CDC7 inhibitor in ovarian cancer

BACKGROUND

The enhancement of DNA damage repair is one of the important mechanisms of platinum resistance. Protein cell division cycle 7 (CDC7) is a conserved serine/threonine kinase that plays important roles in the initiation of DNA replication and is associated with chemotherapy resistance in ovarian cancer. However, whether the CDC7 inhibitor XL413 has antitumor activity against ovarian cancer and its relationship with chemosensitivity remain poorly elucidated.

METHODS

We evaluated the antitumor effects of carboplatin combined with XL413 for ovarian cancer in vitro and in vivo. Cell viability inhibition, colony formation and apoptosis were assessed. The molecules related to DNA repair and damage were investigated. The antitumor effects of carboplatin combined with XL413 were also evaluated in SKOV-3 and OVCAR-3 xenografts in subcutaneous and intraperitoneal tumor models.

RESULTS

Sequential administration of XL413 after carboplatin (CBP) prevented cellular proliferation and promoted apoptosis in ovarian cancer (OC) cells. Compared with the CBP group, the expression level of RAD51 was significantly decreased and the expression level of γH2AX was significantly increased in the sequential combination treatment group. The equential combination treatment could significantly inhibit tumor growth in the subcutaneous and intraperitoneal tumor models, with the expression of RAD51 and Ki67 significantly decreased and the expression of γH2AX increased.

CONCLUSIONS

Sequential administration of CDC7 inhibitor XL413 after carboplatin can enhance the chemotherapeutic effect of carboplatin on ovarian cancer cells. The mechanism may be that CDC7 inhibitor XL413 increases the accumulation of chemotherapy-induced DNA damage by inhibiting homologous recombination repair activity.

Therapy-induced senescent tumor cells in cancer relapse

Cellular senescence is characterized by a generally irreversible cell cycle arrest and the secretion of bioactive factors known as the senescence-associated secretory phenotype (SASP). In an oncogenic context, senescence is considered a tumor suppressive mechanism as it prevents cell proliferation and inhibits the progression from pre-malignant to malignant disease. However, recent studies have demonstrated that senescent tumor cells, which could spontaneously exist within cancer tissues or arise in response to various cancer interventions (the so-called therapy-induced senescence, TIS), can acquire pro-tumorigenic properties and are capable of driving local and metastatic relapse. This highlights the complex and multifaceted nature of cellular senescence in cancer biology. Here, we summarize the current knowledge of the pathological function of therapy-induced senescent tumor cells and discuss possible mechanisms by which tumor cell senescence contributes to cancer relapse. We also discuss implications for future studies toward targeting these less appreciated cells.

Doxorubicin-induced senescence promotes resistance to cell death by modulating genes associated with apoptotic and necrotic pathways in prostate cancer DU145 CD133+/CD44+ cells

Cancer stem cells (CSCs) are the most important cause of cancer treatment failure. Traditional cancer treatments, such as chemotherapy and radiotherapy, damage healthy cells alongside malignant cells, leading to severe adverse effects. Therefore, inducing cellular senescence without triggering apoptosis, which further damages healthy cells, may be an alternative strategy. However, there is insufficient knowledge regarding senescence induction in CSCs that show resistance to treatment and stemness properties. The present study aims to elucidate the effects of senescence induction on proliferation, cell cycle, and apoptosis in prostate CSCs and non-CSCs. Prostate CSCs were isolated from DU145 cancer cells using the FACS method. Subsequently, senescence induction was performed in RWPE-1, DU145, prostate CSCs, and non-CSCs by using different concentrations of Doxorubicin (DOX). Cellular senescence was detected using the senescence markers SA-β-gal, Ki67, and senescence-associated heterochromatin foci (SAHF). The effects of senescence on cell cycle and apoptosis were evaluated using the Muse Cell Analyzer, and genes in signaling pathways associated with the apoptotic/necrotic pathway were analyzed by real-time PCR. Prostate CSCs were isolated with 95.6 ± 1.4% purity according to CD133+/CD44+ characteristics, and spheroid formation belonging to stem cells was observed. After DOX-induced senescence, we observed morphological changes, SA-β-gal positivity, SAHF, and the lack of Ki67 in senescent cells. Furthermore; we detected G2/M cell cycle arrest and downregulation of various apoptosis-related genes in senescent prostate CSCs. Our results showed that DOX is a potent inducer of senescence for prostate CSCs, inhibits proliferation by arresting the cell cycle, and senescent prostate CSCs develop resistance to apoptosis.

YPEL3 expression induces cellular senescence via the Hippo signaling pathway in human breast cancer cells

The Hippo pathway is a signaling pathway that controls organ size in animals by regulating cell proliferation and apoptosis. Yes-associated protein 1 (YAP1), an oncogene associated with the development and progression of breast cancer, is downregulated by the Hippo pathway and is associated with the development and progression of breast cancer. Yippee-like 3 (YPEL3) is a target gene of the tumor suppressor protein p53, and its activation has been shown to inhibit cell growth, induce cellular senescence, and suppress tumor cell metastasis. In this study, we found that YAP1 inhibits the expression of YPEL3 expression in breast cancer cells. Furthermore, a decrease in lamin B1, a marker protein of cellular senescence, coupled with the activation of senescence-associated β-galactosidase indicated that upregulating YPEL3 levels through YAP1 downregulation can induce cellular senescence. Additionally, elevated YPEL3 levels resulted in higher levels of oxygen consumption rate in mitochondria, thus promoting apoptosis. This suggests that YPEL3 plays a crucial role in regulating oxidative stress and cell apoptosis in breast cancer cells. Therefore, the interaction between YAP1 and YPEL3 represents a novel mechanism of cellular senescence mediated by the Hippo signaling pathway. Collectively, our findings suggest that the Hippo signaling pathway plays an important role in regulating cellular senescence, which could have implications for the development of new therapeutic strategies for diseases such as cancer.

Mechanisms of cancer cell death induction by triptolide

Drug resistance is a hot topic issue in cancer research and therapy. Although cancer therapy including radiotherapy and anti-cancer drugs can kill malignant cells within the tumor, cancer cells can develop a wide range of mechanisms to resist the toxic effects of anti-cancer agents. Cancer cells may provide some mechanisms to resist oxidative stress and escape from apoptosis and attack by the immune system. Furthermore, cancer cells may resist senescence, pyroptosis, ferroptosis, necroptosis, and autophagic cell death by modulating several critical genes. The development of these mechanisms leads to resistance to anti-cancer drugs and also radiotherapy. Resistance to therapy can increase mortality and reduce survival following cancer therapy. Thus, overcoming mechanisms of resistance to cell death in malignant cells can facilitate tumor elimination and increase the efficiency of anti-cancer therapy. Natural-derived molecules are intriguing agents that may be suggested to be used as an adjuvant in combination with other anticancer drugs or radiotherapy to sensitize cancer cells to therapy with at least side effects. This paper aims to review the potential of triptolide for inducing various types of cell death in cancer cells. We review the induction or resistance to different cell death mechanisms such as apoptosis, autophagic cell death, senescence, pyroptosis, ferroptosis, and necrosis following the administration of triptolide. We also review the safety and future perspectives for triptolide and its derivatives in experimental and human studies. The anticancer potential of triptolide and its derivatives may make them effective adjuvants for enhancing tumor suppression in combination with anticancer therapy.

A predictive molecular signature consisting of lncRNAs associated with cellular senescence for the prognosis of lung adenocarcinoma

The role of long noncoding RNAs (lncRNAs) has been verified by more and more researches in recent years. However, there are few reports on cellular senescence-associated lncRNAs in lung adenocarcinoma (LUAD). Therefore, to explore the prognostic effect of lncRNAs in LUAD, 279 cellular senescence-related genes, survival information and clinicopathologic parameters were derived from the CellAge database and The Cancer Genome Atlas (TCGA) database. Then, we constructed a novel cellular senescence-associated lncRNAs predictive signature (CS-ALPS) consisting of 6 lncRNAS (AC026355.1, AL365181.2, AF131215.5, C20orf197, GAS6-AS1, GSEC). According to the median of the risk score, 480 samples were divided into high-risk and low-risk groups. Furthermore, the clinicopathological and biological functions, immune characteristics and common drug sensitivity were analyzed between two risk groups. In conclusion, the CS-ALPS can independently forecast the prognosis of LUAD, which reveals the potential molecular mechanism of cellular senescence-associated lncRNAs, and provides appropriate strategies for the clinical treatment of patients with LUAD.

Application of Chiral Piperidine Scaffolds in Drug Design

Chiral piperidine scaffolds are prevalent as the common cores of a large number of active pharmaceuticals in medical chemistry. This review outlined the diversity of chiral piperidine scaffolds in recently approved drugs, and also covers the scaffolds in leads and drug candidates. The significance of chiral piperidine scaffolds in drug design is also discussed in this article. With the introduction of chiral piperidine scaffolds into small molecules, the exploration of drug-like molecules can be benefitted from the following aspect: (1) modulating the physicochemical properties; (2) enhancing the biological activities and selectivity; (3) improving pharmacokinetic properties; and (4) reducing the cardiac hERG toxicity. Given above, chiral piperidine-based discovery of small molecules will be a promising strategy to enrich our molecules' library to fight against diseases.

Inhibition of protein kinase C delta leads to cellular senescence to induce anti-tumor effects in colorectal cancer

Protein kinase C delta (PKCδ) is a multifunctional serine-threonine kinase implicated in cell proliferation, differentiation, tumorigenesis, and therapeutic resistance. However, the molecular mechanism of PKCδ in colorectal cancer (CRC) remains unclear. In this study, we showed that PKCδ acts as a negative regulator of cellular senescence in p53 wild-type (wt-p53) CRC. Immunohistochemical analysis revealed that PKCδ levels in human CRC tissues were higher than those in the surrounding normal tissues. Deletion studies have shown that cell proliferation and tumorigenesis in wt-p53 CRC is sensitive to PKCδ expression. We found that PKCδ activates p21 via a p53-independent pathway and that PKCδ-kinase activity is essential for p21 activity. In addition, both repression of PKCδ expression and inhibition of PKCδ activity induced cellular senescence-like phenotypes, including increased senescence-associated β-galactosidase (SA-β-gal) staining, low LaminB1 expression, large nucleus size, and senescence-associated secretory phenotype (SASP) detection. Finally, a kinase inhibitor of PKCδ suppressed senescence-dependent tumorigenicity in a dose-dependent manner. These results offer a mechanistic insight into CRC survival and tumorigenesis. In addition, a novel therapeutic strategy for wt-p53 CRC is proposed.

Basic and translational research on carbon-ion radiobiology

Carbon-ion beam irradiation (IR) has evident advantages over the conventional photon beams in treating tumors. It releases enormous amount of energy in a well-defined range with insignificant scatter in surrounding tissues based on well-localized energy deposition. Over the past 28 years, more than 14,000 patients with various types of cancer have been treated by carbon ion radiotherapy (CIRT) with promising results at QST. I have provided an overview of the basic and translational research on carbon-ion radiobiology including mechanisms underlying high linear energy transfer (LET) carbon-ion IR-induced cell death (apoptosis, autophagy, senescence, mitotic catastrophe etc.) and high radiocurability produced by carbon-ion beams in combination with DNA damaging drugs or with molecular-targeted drugs, micro-RNA therapeutics and immunotherapy. Additionally, I have focused on the application of these treatment in human cancer cells, especially cancer stem cells (CSCs). Finally, I have summarized the current studies on the application of basic carbon-ion beam IR according to the cancer types and clinical outcomes.

Metabolic Flux Analysis Reveals the Roles of Stearate and Oleate on CPT1C-mediated Tumor Cell Senescence

Cellular senescence is a state of proliferative arrest, and the development of carcinoma can be suppressed by conferring tumor cell senescence. Recently, we found that carnitine palmitoyltransferase 1C (CPT1C) controls tumor cell proliferation and senescence via regulating lipid metabolism and mitochondrial function. Here, ¹³C-metabolic flux analysis (¹³C-MFA) was performed and the results revealed that CPT1C knockdown in MDA-MB-231 cells significantly induced cellular senescence accompanied by altered fatty acid metabolism. Strikingly, stearate synthesis was decreased while oleate was increased. Furthermore, stearate significantly inhibited proliferation while oleate reversed the senescent phenotype induced by silencing CPT1C in MDA-MB-231 cells as well as PANC-1 cells. A939572, an inhibitor of stearoyl-Coenzyme A desaturase 1, had the same effect as stearate to inhibit cellular proliferation. These results demonstrated that stearate and oleate are involved in CPT1C-mediated tumor cellular senescence, and the regulation of stearate/oleate rate via inhibition of SCD-1 could be an additional strategy with depletion of CPT1C for cancer therapy.

In Vitro and In Vivo Biological Activity of Ruthenium 1,10-Phenanthroline-5,6-dione Arene Complexes

Ruthenium(II) arene complexes exhibit promising chemotherapeutic properties. In this study, the effect of the counter anion in Ru(II) complexes was evaluated by analyzing the biological effect of two Ru(II) p-cymene derivatives with the 1,10-phenanthroline-5,6-dione ligand of general-formula [(η6-arene)Ru(L)Cl][X] X = CF3SO3 (JHOR10) and PF6 (JHOR11). The biological activity of JHOR10 and JHOR11 was examined in the ovarian carcinoma cell line A2780, colorectal carcinoma cell line HCT116, doxorubicin-resistant HCT116 (HCT116-Dox) and in normal human dermal fibroblasts. Both complexes JHOR10 and JHOR11 displayed an antiproliferative effect on A2780 and HCT116 cell lines, and low cytotoxicity in fibroblasts. Interestingly, JHOR11 also showed antiproliferative activity in the HCT116-Dox cancer cell line, while JHOR10 was inactive. Studies in A2780 cells showed that JHOR11 induced the production of reactive oxygen species (ROS) that trigger autophagy and cellular senescence, but no apoptosis induction. Further analysis showed that JHOR11 presented no tumorigenicity, with no effect in the cellular mobility, as evaluated by thye wound scratch assay, and no anti- or pro-angiogenic effect, as evaluated by the ex-ovo chorioallantoic membrane (CAM) assay. Importantly, JHOR11 presented no toxicity in chicken and zebrafish embryos and reduced in vivo the proliferation of HCT116 injected into zebrafish embryos. These results show that these are suitable complexes for clinical applications with improved tumor cell cytotoxicity and low toxicity, and that counter-anion alteration might be a viable clinical strategy for improving chemotherapy outcomes in multidrug-resistant (MDR) tumors.

Senotherapies: A novel strategy for synergistic anti-tumor therapy

Cellular senescence was initially considered an effective antitumor mechanism, and senescence-induced therapy has previously been regarded as an efficient treatment. However, increasing studies have discovered that persistent senescent cells (SNCs) might have unanticipated negative repercussions for antitumor treatment. The long-term build-up of SNCs exacerbates toxic side effects, treatment resistance, and poor prognosis, and tumor cells that undergo senescence escape can acquire stemness to repopulate the tumor, leading to cancer recurrence. Thus, senotherapies that eliminate SNCs could be used as a new strategy for synergistic antitumor therapy. In this review, we summarize the adverse effects of SNCs in tumor development and the mechanisms by which senescent tumor cells escape senescence, discuss the relationship between senescence and polyploidy, and highlight the potential of senotherapies as an emerging adjuvant antitumor treatment strategy. Such a strategy is expected to provide new approaches for antitumor drug development from the perspective of cellular senescence.

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.

Artesunate Inhibits the Cell Growth in Colorectal Cancer by Promoting ROS-Dependent Cell Senescence and Autophagy

Although artesunate has been reported to be a promising candidate for colorectal cancer (CRC) treatment, the underlying mechanisms and molecular targets of artesunate are yet to be explored. Here, we report that artesunate acts as a senescence and autophagy inducer to exert its inhibitory effect on CRC in a reactive oxygen species (ROS)-dependent manner. In SW480 and HCT116 cells, artesunate treatment led to mitochondrial dysfunction, drastically promoted mitochondrial ROS generation, and consequently inhibited cell proliferation by causing cell cycle arrest at G0/G1 phase as well as subsequent p16- and p21-mediated cell senescence. Senescent cells underwent endoplasmic reticulum stress (ERS), and the unfolded protein response (UPR) was activated via IRE1α signaling, with upregulated BIP, IRE1α, phosphorylated IRE1α (p-IRE1α), CHOP, and DR5. Further experiments revealed that autophagy was induced by artesunate treatment due to oxidative stress and ER stress. In contrast, N-Acetylcysteine (NAC, an ROS scavenger) and 3-Methyladenine (3-MA, an autophagy inhibitor) restored cell viability and attenuated autophagy in artesunate-treated cells. Furthermore, cellular free Ca²⁺ levels were increased and could be repressed by NAC, 3-MA, and GSK2350168 (an IRE1α inhibitor). In vivo, artesunate administration reduced the growth of CT26 cell-derived tumors in BALB/c mice. Ki67 and cyclin D1 expression was downregulated in tumor tissue, while p16, p21, p-IRE1α, and LC3B expression was upregulated. Taken together, artesunate induces senescence and autophagy to inhibit cell proliferation in colorectal cancer by promoting excessive ROS generation.

Argonaute 2 modulates EGFR-RAS signaling to promote mutant HRAS and NRAS-driven malignancies

Activating mutations in RAS GTPases drive nearly 30% of all human cancers. Our prior work described an essential role for Argonaute 2 (AGO2), of the RNA-induced silencing complex, in mutant KRAS-driven cancers. Here, we identified a novel endogenous interaction between AGO2 and RAS in both wild-type (WT) and mutant HRAS/NRAS cells. This interaction was regulated through EGFR-mediated phosphorylation of Y393-AGO2, and utilizing molecular dynamic simulation, we identified a conformational change in pY393-AGO2 protein structure leading to disruption of the RAS binding site. Knockdown of AGO2 led to a profound decrease in proliferation of mutant HRAS/NRAS-driven cell lines but not WT RAS cells. These cells demonstrated oncogene-induced senescence (OIS) as evidenced by β-galactosidase staining and induction of multiple downstream senescence effectors. Mechanistically, we discovered that the senescent phenotype was mediated via induction of reactive oxygen species. Intriguingly, we further identified that loss of AGO2 promoted a novel feed forward pathway leading to inhibition of the PTP1B phosphatase and activation of EGFR-MAPK signaling, consequently resulting in OIS. Taken together, our study demonstrates that the EGFR-AGO2-RAS signaling axis is essential for maintaining mutant HRAS and NRAS-driven malignancies.

LKB1: Can We Target an Hidden Target? Focus on NSCLC

LKB1 (liver kinase B1) is a master regulator of several processes such as metabolism, proliferation, cell polarity and immunity. About one third of non-small cell lung cancers (NSCLCs) present LKB1 alterations, which almost invariably lead to protein loss, resulting in the absence of a potential druggable target. In addition, LKB1-null tumors are very aggressive and resistant to chemotherapy, targeted therapies and immune checkpoint inhibitors (ICIs). In this review, we report and comment strategies that exploit peculiar co-vulnerabilities to effectively treat this subgroup of NSCLCs. LKB1 loss leads to an enhanced metabolic avidity, and treatments inducing metabolic stress were successful in inhibiting tumor growth in several preclinical models. Biguanides, by compromising mitochondria and reducing systemic glucose availability, and the glutaminase inhibitor telaglenastat (CB-839), inhibiting glutamate production and reducing carbon intermediates essential for TCA cycle progression, have provided the most interesting results and entered different clinical trials enrolling also LKB1-null NSCLC patients. Nutrient deprivation has been investigated as an alternative therapeutic intervention, giving rise to interesting results exploitable to design specific dietetic regimens able to counteract cancer progression. Other strategies aimed at targeting LKB1-null NSCLCs exploit its pivotal role in modulating cell proliferation and cell invasion. Several inhibitors of LKB1 downstream proteins, such as mTOR, MEK, ERK and SRK/FAK, resulted specifically active on LKB1-mutated preclinical models and, being molecules already in clinical experimentation, could be soon proposed as a specific therapy for these patients. In particular, the rational use in combination of these inhibitors represents a very promising strategy to prevent the activation of collateral pathways and possibly avoid the potential emergence of resistance to these drugs. LKB1-null phenotype has been correlated to ICIs resistance but several studies have already proposed the mechanisms involved and potential interventions. Interestingly, emerging data highlighted that LKB1 alterations represent positive determinants to the new KRAS specific inhibitors response in KRAS co-mutated NSCLCs. In conclusion, the absence of the target did not block the development of treatments able to hit LKB1-mutated NSCLCs acting on several fronts. This will give patients a concrete chance to finally benefit from an effective therapy.

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.

Melatonin finely tunes proliferation and senescence in hematopoietic stem cells

Human hematopoietic stem/progenitor cells (HSPCs) are pluripotent cells that gradually lose their self-renewal and regenerative potential, to give rise to mature cells of the hematopoietic system by differentiation. HSPC infusion is used to restore hematopoietic function in patients with a variety of onco-hematologic and immune-mediated disorders. The functionality of these cells is therefore of great importance to ensure the homeostasis of the hematopoietic system. Melatonin plays an important role as immunomodulatory and oncostatic hormone. In the present manuscript, we aimed at evaluating the activity of melatonin in modulating HSPC senescence, in the attempt to improve their hemopoietic regenerative potential. We exposed HSPCs to melatonin, in different conditions, and then analyzed the expression of genes regulating cell cycle and cell senescence. Moreover, we assessed cell senescence by β-galactosidase and telomerase activity. Our results showed the ability of melatonin to counteract HSPC senescence, thus paving the way for enhanced efficiency in their clinical application.

Chemosensitization Effect of Seabuckthorn (Hippophae rhamnoides L.) Pulp Oil via Autophagy and Senescence in NSCLC Cells

The research has demonstrated a synergistic anticancer effect of Seabuckthorn pulp oil (SBO) and the standard chemotherapy regimen Docetaxel (DTX) against two non-small cell lung cancer (NSCLC) cell lines: A549 and H23. The synergizing effect of an SBO and DTX combination was detected utilizing SRB assay and combination index (CI) approaches. Flow cytometry was carried out using fluorescent probes to measure cell cycle analysis by DNA content and reactive oxygen species (ROS) generation. Further, we demonstrated that the synergistic anticancer activity of SBO merged with DTX was achieved by caspase-independent autophagy and senescence induction. These changes were concomitant with increased generation of ROS production and microtubule-associated protein 1 light chain 3 (LC3) protein expression, G1-phase arrest, and enhanced senescence-associated β-galactosidase staining activity. Our data also demonstrated that SBO or DTX treatment groups solely upregulated the phosphorylation of ERK, which coincided with the induction of autophagy vacuoles and was functionally associated with ROS activation. Moreover, endogenous LC3 puncta staining was performed and monitored by confocal microscopy. Overall, these results suggest new mechanisms for the antitumor activity of SBO co-treated with DTX through triggering autophagic cell death and senescence against cancer cells as a result of sustained ERK phosphorylation and intracellular ROS production in NSCLC. In addition, we also highlight SBO as an alternative therapeutic option or adjunct therapeutic strategy in combination with chemotherapeutic agents in lung cancer therapy management.

BUB3, beyond the Simple Role of Partner

The BUB3 protein plays a key role in the activation of the spindle assembly checkpoint (SAC), a ubiquitous surveillance mechanism that ensures the fidelity of chromosome segregation in mitosis and, consequently, prevents chromosome mis-segregation and aneuploidy. Besides its role in SAC signaling, BUB3 regulates chromosome attachment to the spindle microtubules. It is also involved in telomere replication and maintenance. Deficiency of the BUB3 gene has been closely linked to premature aging. Upregulation of the BUB3 gene has been found in a variety of human cancers and is associated with poor prognoses. Here, we review the structure and functions of BUB3 in mitosis, its expression in cancer and association with survival prognoses, and its potential as an anticancer target.

Exploring the role of senescence inducers and senotherapeutics as targets for anticancer natural products

During the last few decades, cancer has remained one of the deadliest diseases that endanger human health, emphasizing urgent drug discovery. Cellular senescence has gained a great deal of attention in recent years because of its link to the development of cancer therapy. Senescent cells are incapable of proliferating due to irreversibly inhibited the initiation of the cell cycle pathways. However, senescent cells aggregate in tissues and produce a pro-inflammatory secretome called senescence-associated secretory phenotype (SASP) that can cause serious harmful effects if not managed properly. There is mounting evidence that senescent cells lead to various phases of tumorigenesis in various anatomical sites, owing mostly to the paracrine activities of the SASP. Therefore, a new treatment field called senotherapeutics has been established. Senotherapeutics are newly developed anticancer agents that have been demonstrated to inhibit cancer effectively. In light of recent findings, several promising natural products have been identified as senescence inducers and senotherapeutics, including, miliusanes, epigallocatechin gallate, phloretin, silybin, resveratrol, genistein, sulforaphane, quercetin, allicin, fisetin, piperlongumine, berberine, triptolide, tocotrienols and curcumin analogs. Several of them have already been validated through preclinical trials and exert an enormous potential for clinical trials. This review article focuses on and summarises the latest advances on cellular senescence and its potential as a target for cancer treatment and highlights the well-known natural products as senotherapeutics for cancer treatment.

Caveolin-1 Regulation and Function in Mouse Uterus during Early Pregnancy and under Human In Vitro Decidualization

Decidualization is essential to rodent and primate pregnancy. Senescence is increased during decidualization. Failure of senescence clearance during decidualization will cause pregnancy abnormality. Caveolin-1 is located in plasmalemmal caveolae and involved in senescence. However, whether caveolin-1 is involved in decidualization remains undefined. In this study, we examined the expression, regulation and function of Caveolin-1 during mouse early pregnancy and under mouse and human in vitro decidualization. From days 1 to 8 of pregnancy, Caveolin-1 signals are mainly located in endothelium and myometrium. Estrogen stimulates Caveolin-1 expression in endothelium. Deficiency of estrogen receptor α significantly promotes Caveolin-1 level in uterine stromal cells. Progesterone upregulates Caveolin-1 expression in luminal epithelium. During mouse in vitro decidualization, Caveolin-1 is significantly increased. However, Caveolin-1 is obviously decreased during human in vitro decidualization. Caveolin-1 overexpression and siRNA suppress and upregulate IGFBP1 expression under in vitro decidualization, respectively. Blastocysts-derived tumor necrosis factor α (TNFα) and human Chorionic Gonadotropin (hCG) regulate Caveolin-1 in mouse and human decidual cells, respectively. Caveolin-1 levels are also regulated by high glucose and insulin. In conclusion, a low level of Caveolin-1 should be beneficial for human decidualization.

Long-Term Social Isolation-Induced Autophagy Inhibition and Cell Senescence Aggravate Cognitive Impairment in D(+)Galactose-Treated Male Mice

Aging is associated with physiological and pathological changes and presents health complications, such as dementia. Isolation has also been associated with the experience of growing old. Both have been linked individually to the incidence of cognitive decline. In this present study, the effects of these two phenomena have been looked at in animal models where aging was induced with D(+)Galactose in mice who underwent long-term post-weaned social isolation (L-PWSI). Assessing cognitive function using Y-maze, Morris water maze (MWM), and passive avoidance tests (PATs) confirmed that cognition is impaired in either of the treatments but worsened when the D(+)Galactose mice were subjected to L-PWSI. Moreover, a synaptic protein, PSD95, and dendritic spines density were significantly reduced in the L-PWSI and D(+)Galactose-treated mice. Our previous study revealed that autophagy deficit is involved in cognitive impairment in the L-PWSI model. Here, we first report the inhibited cell cycle in L-PWSI, combined with the decreased autophagy, aggravates cognitive impairment in D(+)Galactose-treated mice. Beyond these, the autophagy and cell cycle mechanisms that link isolation and aging have been explored. The close association between isolation and aging in humans is very real and needs much research attention going forward for possible therapeutic interventions.

Immunotherapeutic HCW9218 augments anti-tumor activity of chemotherapy via NK cell-mediated reduction of therapy-induced senescent cells

Therapy induced senescence (TIS) in tumors and TIS cancer cells secrete proinflammatory senescence-associated secretory phenotype (SASP) factors. SASP factors promote TIS cancer cells to re-enter the growth cycle with stemness characteristics, resulting in chemo-resistance and disease relapse. Herein, we show that the immunotherapeutic HCW9218, comprising transforming growth factor-β (TGF-β) receptor II and interleukin (IL)-15/IL-15 receptor α domains, enhances metabolic and cytotoxic activities of immune cells and reduces TIS tumor cells in vivo to improve the efficacy of docetaxel and gemcitabine plus nab-paclitaxel against B16F10 melanoma and SW1990 pancreatic tumors, respectively. Mechanistically, HCW9218 treatment reduces the immunosuppressive tumor microenvironment and enhances immune cell infiltration and cytotoxicity in the tumors to eliminate TIS cancer cells. Immuno-depletion analysis suggests that HCW9218-activated natural killer cells play a pivotal role in TIS cancer cell removal. HCW9218 treatment following docetaxel chemotherapy further enhances efficacy of tumor antigen-specific and anti-programmed death-ligand 1 (PD-L1) antibodies in B16F10 tumor-bearing mice. We also show that HCW9218 treatment decreases TIS cells and lowers SASP factors in off-target tissues caused by chemotherapy of tumor-bearing mice. Collectively, HCW9218 has the potential to significantly enhance anti-tumor efficacy of chemotherapy, therapeutic antibodies, and checkpoint blockade by eliminating TIS cancer cells while reducing TIS-mediated proinflammatory side effects in normal tissues.

MZF1 mediates oncogene-induced senescence by promoting the transcription of p16INK4A

Oncogene induced senescence is a tumor suppressing defense mechanism, in which the cell cycle-dependent protein kinase (CDK) inhibitor p16INK4A (encoded by the CDKN2A gene) plays a key role. We previously reported that a transcriptional co-activator chromodomain helicase DNA binding protein 7 (CHD7) mediates oncogenic ras-induced senescence by inducing transcription of the p16INK4A gene. In the current study, we identified myeloid zinc finger 1 (MZF1) as the transcriptional factor that recruits CHD7 to the p16INK4A promoter, where it mediates oncogenic ras-induced p16INK4A transcription and senescence through CHD7, in primary human cells from multiple origins. Moreover, the expression of MZF1 is induced by oncogenic ras in senescent cells through the c-Jun and Ets1 transcriptional factors upon their activation by the Ras-Raf-1-MEK-ERK signaling pathway. In non-small cell lung cancer (NSCLC) and pancreatic adenocarcinoma (PAAD) where activating ras mutations occur frequently, reduced MZF1 expression is observed in tumors, as compared to corresponding normal tissues, and correlates with poor patient survival. Analysis of single cell RNA-sequencing data from PAAD patients revealed that among the tumor cells with normal RB expression levels, those with reduced levels of MZF1 are more likely to express lower p16INK4A levels. These findings have identified novel signaling components in the pathway that mediates induction of the p16INK4A tumor suppressor and the senescence response, and suggested that MZF1 is a potential tumor suppressor in at least some cancer types, the loss of which contributes to the inactivation of the p16INK4A/RB pathway and disruption of senescence in tumor cells with intact RB.

Oridonin inhibits SASP by blocking p38 and NF-κB pathways in senescent cells

Cellular senescence is a state of irreversible cell growth arrest that functions as a biological defense mechanism against severe DNA damage. Senescent cells with DNA damage produce pro-inflammatory cytokines, such as IL-6 and IL-8, and this phenomenon is called the senescence-associated secretory phenotype (SASP). SASP factors have been implicated in various disorders, including cancer. We performed a screening assay and identified oridonin as a candidate SASP inhibitor. Oridonin is an active diterpenoid that is isolated from Isodon plants and has been reported to exhibit anti-inflammatory, antibacterial, antioxidant, and antitumor activities. It reduced the secretion of IL-6 and IL-8 in senescent cells at the protein and mRNA levels. Oridonin also inhibited p65 subunit of NF-κB activity. However, oridonin did not affect SA β-gal activity and enhanced the expression of p21. The expression and phosphorylation of p38 were down-regulated by oridonin. The p38 inhibitor SB203580 inhibited the secretion of IL-8, slightly inhibited the secretion of IL-6, and did not affect NF-κB activity. Therefore, the NF-κB and p38 pathways may contribute to the inhibition of SASP by oridonin. Oridonin has potential as a therapeutic agent for SASP-related diseases.

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.

Sorafenib, rapamycin, and venetoclax attenuate doxorubicin-induced senescence and promote apoptosis in HCT116 cells

Emerging evidence has shown that the therapy-induced senescent growth arrest in cancer cells is of durable nature whereby a subset of cells can reinstate proliferative capacity. Promising new drugs named senolytics selectively target senescent cells and commit them into apoptosis. Accordingly, senolytics have been proposed as adjuvant cancer treatment to cull senescent tumor cells, and thus, screening for agents that exhibit senolytic properties is highly warranted. Our study aimed to investigate three agents, sorafenib, rapamycin, and venetoclax for their senolytic potential in doxorubicin-induced senescence in HCT116 cells. HCT116 cells were treated with one of the three agents, sorafenib (5 µM), rapamycin (100 nM), or venetoclax (10 µM), in the absence or presence of doxorubicin (1 µM). Senescence was evaluated using microscopy-based and flow cytometry-based Senescence-associated-β-galactosidase staining (SA-β-gal), while apoptosis was assessed using annexin V-FITC/PI, and Muse caspase-3/-7 activity assays. We screened for potential genes through which the three drugs exerted senolytic-like action using the Human Cancer Pathway Finder PCR array. The three agents reduced doxorubicin-induced senescent cell subpopulations and significantly enhanced the apoptotic effect of doxorubicin compared with those treated only with doxorubicin. The senescence genes IGFBP5 and BMI1 and the apoptosis genes CASP7 and CASP9 emerged as candidate genes through which the three drugs exhibited senolytic-like properties. These results suggest that the attenuation of doxorubicin-induced senescence might have shifted HCT116 cells to apoptosis by exposure to the tested pharmacological agents. Our work argues for the use of senolytics to reduce senescence-mediated resistance in tumor cells and to enhance chemotherapy efficacy.

Skin Aging, Cellular Senescence and Natural Polyphenols

The skin, being the barrier organ of the body, is constitutively exposed to various stimuli impacting its morphology and function. Senescent cells have been found to accumulate with age and may contribute to age-related skin changes and pathologies. Natural polyphenols exert many health benefits, including ameliorative effects on skin aging. By affecting molecular pathways of senescence, polyphenols are able to prevent or delay the senescence formation and, consequently, avoid or ameliorate aging and age-associated pathologies of the skin. This review aims to provide an overview of the current state of knowledge in skin aging and cellular senescence, and to summarize the recent in vitro studies related to the anti-senescent mechanisms of natural polyphenols carried out on keratinocytes, melanocytes and fibroblasts. Aged skin in the context of the COVID-19 pandemic will be also discussed.

Gemcitabine radiosensitization primes irradiated malignant meningioma cells for senolytic elimination by navitoclax

Background

Malignant meningioma is an aggressive tumor that requires adjuvant radiotherapy after surgery, yet there has been no standard systemic therapy established so far. We recently reported that malignant meningioma cells are highly sensitive to gemcitabine; however, it remains unknown whether or how gemcitabine interacts with ionizing radiation (IR) in malignant meningioma cells.

Methods

We examined the radiosensitization effects of gemcitabine using malignant meningioma cell lines and xenografts and explored the underlying mechanisms.

Results

Gemcitabine sensitized malignant meningioma cells to IR through the induction of senescence both in vitro and in vivo. Gemcitabine augmented the intracellular production of reactive oxygen species (ROS) by IR, which, together with cell growth suppression/senescence induced by this combination, was inhibited by N-acetyl-cysteine, suggesting a pivotal role for ROS in these combinatorial effects. Navitoclax, a senolytic drug that inhibits Bcl-2 proteins, further enhanced the effects of the combination of gemcitabine and IR by strongly inducing apoptotic cell death in senescent cells.

Conclusion

These results not only indicate the potential of gemcitabine as a candidate radiosensitizer for malignant meningioma, but also reveal a novel role for gemcitabine radiosensitization as a means to create a therapeutic vulnerability of senescent meningioma cells to senolytics.

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.

Footprints of microRNAs in Cancer Biology

MicroRNAs (miRNAs) are short non-coding RNAs involved in post-transcriptional gene regulation. Over the past years, various studies have demonstrated the role of aberrant miRNA expression in the onset of cancer. The mechanisms by which miRNA exerts its cancer-promoting or inhibitory effects are apparent through the various cancer hallmarks, which include selective proliferative advantage, altered stress response, vascularization, invasion and metastasis, metabolic rewiring, the tumor microenvironment and immune modulation; therefore, this review aims to highlight the association between miRNAs and the various cancer hallmarks by dissecting the mechanisms of miRNA regulation in each hallmark separately. It is hoped that the information presented herein will provide further insights regarding the role of cancer and serve as a guideline to evaluate the potential of microRNAs to be utilized as biomarkers and therapeutic targets on a larger scale in cancer research.

Senescence in HBV-, HCV- and NAFLD- Mediated Hepatocellular Carcinoma and Senotherapeutics: Current Evidence and Future Perspective

Cell senescence constitutes a physiological process that serves as protection from malignant transformation of cells. However, recent scientific discoveries also identify cell senescence as pivotal in hepatocellular cancer (HCC) biology. The review herein aimed to accumulate evidence on senescence as a mediator of HCC occurrence in hepatitis B (HBV), C (HCV) virus infections, and non-alcoholic fatty liver disease (NAFLD). In HBV infection, the carcinogenic HBV X protein frequently mutates during chronic infection, and subsequently exhibits different effects on senescence. In HCV infection, senescent non-functional T-cells do not effectively clear pre-malignant hepatocytes. Furthermore, the HCV Core protein inhibits the occurrence of normal stress-induced hepatocyte senescence, allowing damaged cells to maintain their proliferative potential. In NAFLD-mediated HCC, current data point towards the gut microbiome and hepatic stellate cell senescence. Additionally, senescence contributes in the development of resistance in targeted therapies, such as sorafenib. Finally, the promising role of senotherapeutics in HCC was also explored. Overall, although we may still be at a primitive stage in fully unraveling the role of senescence in cancer, it seems that understanding and harnessing senescence may have the potential to revolutionize the way we treat hepatocellular cancer.

A mechanistic insight into the biological activities of urolithins as gut microbial metabolites of ellagitannins

Urolithins are the gut metabolites produced from ellagitannin-rich foods such as pomegranates, tea, walnuts, as well as strawberries, raspberries, blackberries, and cloudberries. Urolithins are of growing interest due to their various biological activities including cardiovascular protection, anti-inflammatory activity, anticancer properties, antidiabetic activity, and antiaging properties. Several studies mostly based on in vitro and in vivo experiments have investigated the potential mechanisms of urolithins which support the beneficial effects of urolithins in the treatment of several diseases such as Alzheimer's disease, type 2 diabetes mellitus, liver disease, cardiovascular disease, and various cancers. It is now obvious that urolithins can involve several cellular mechanisms including inhibition of MDM2-p53 interaction, modulation of mitogen-activated protein kinase pathway, and suppressing nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity. Antiaging activity is the most appealing and probably the most important property of urolithin A that has been investigated in depth in recent studies, owing to its unique effects on activation of mitophagy and mitochondrial biogenesis. A recent clinical trial showed that urolithin A is safe up to 2,500 mg/day and can improve mitochondrial biomarkers in elderly patients. Regarding the importance of mitochondria in the pathophysiology of many diseases, urolithins merit further research especially in clinical trials to unravel more aspects of their clinical significance. Besides the nutritional value of urolithins, recent studies proved that urolithins can be used as pharmacological agents to prevent or cure several diseases. Here, we comprehensively review the potential role of urolithins as new therapeutic agents with a special focus on the molecular pathways that have been involved in their biological effects. The pharmacokinetics of urolithins is also included.

In Vitro Anticancer Activity and Oxidative Stress Biomarkers Status Determined by Usnea barbata (L.) F.H. Wigg. Dry Extracts

Lichens represent an important resource for common traditional medicines due to their numerous metabolites that can exert diverse pharmacological activities including anticancer effects. To find new anticancer compounds with fewer side effects and low tumor resistance, a bioprospective study of Usnea barbata (L.) F.H. Wigg. (U. barbata), a lichen from the Călimani Mountains (Suceava county, Romania) was performed. The aim of this research was to investigate the anticancer potential, morphologic changes, wound healing property, clonogenesis, and oxidative stress biomarker status of four extracts of U. barbata in different solvents (methanol, ethanol, acetone, and ethyl acetate), and also of usnic acid (UA) as a positive control on the CAL-27 (ATCC^® CRL-2095™) oral squamous carcinoma (OSCC) cell line and V79 (ATCC^® CCL-93™) lung fibroblasts as normal cells. Using the MTT assay and according to IC₅₀ values, it was found that the most potent anticancer property was displayed by acetone and ethyl acetate extracts. All U. barbata extracts determined morphological modifications (losing adhesion capacity, membrane shrinkage, formation of abnormal cellular wrinkles, and vacuolization) with higher intensity in tumor cells than in normal ones. The most intense anti-migration effect was established in the acetone extract treatment. The clonogenic assay showed that some U. barbata extracts decreased the ability of cancer cells to form colonies compared to untreated cells, suggesting a potential anti-tumorigenic property of the tested extracts. Therefore, all the U. barbata extracts manifest anticancer activity of different intensity, based, at least partially, on an imbalance in antioxidant defense mechanisms, causing oxidative stress.

Comparable radiation sensitivity in p53 wild-type and p53 deficient tumor cells associated with different cell death modalities

Studies of radiation interaction with tumor cells often take apoptosis as the desired results. However, mitotic catastrophe and senescence are also promoted by clinically relevant doses of radiation. Furthermore, p53 is a well-known transcription factor that is closely associated with radiosensitivity and radiation-induced cell death. Therefore, we aimed to investigate the involvement of radiosensitivity, cell death modalities and p53 status in response to carbon-ion radiation (CIR) here. Isogenic human colorectal cancer cell lines HCT116 (p53^+/+ and p53^-/-) were irradiated with high-LET carbon ions. Cell survival was determined by the standard colony-forming assay. 53BP1 foci were visualized to identify the repair kinetics of DNA double-strand breaks (DSBs). Cellular senescence was measured by SA-β-Gal and Ki67 staining. Mitotic catastrophe was determined with DAPI staining. Comparable radiosensitivities of p53^+/+ and p53^-/- HCT116 colorectal cells induced by CIR were demonstrated, as well as persistent 53BP1 foci indicated DNA repair deficiency in both cell lines. Different degree of premature senescence in isogenic HCT116 colorectal cancer cells suggested that CIR-induced premature senescence was more dependent on p21 but not p53. Sustained upregulation of p21 played multifunctional roles in senescence enhancement and apoptosis inhibition in p53^+/+ cells. p21 inhibition further increased radiosensitivity of p53^+/+ cells. Complex cell death modalities rather than single cell death were induced in both p53^+/+ and p53^-/- cells after 5 Gy CIR. Mitotic catastrophe was predominant in p53^-/- cells due to inefficient activation of Chk1 and Chk2 phosphorylation in combination with p53 null. Senescence was the major cell death mechanism in p53^+/+ cells via p21-dependent pathway. Taken together, p21-mediated premature senescence might be used by tumor cells to escape from CIR-induced cytotoxicity, at least for a time.

Conditions Mimicking the Cancer Microenvironment Modulate the Functional Outcome of Human Chorionic Villus Mesenchymal Stem/Stromal Cells in vitro

Mesenchymal stem/stromal cells isolated from chorionic villi of human term placentae (CV-MSCs) possess unique biological characters. They exhibit self-renewal, directional migration, differentiation, and immunomodulatory effects on other cell lineages, by virtue of which they can be utilized as therapeutic carriers, for drug targeting, and therapy. Tumors display characteristic features of a damaged tissue microenvironment, which is saturated with conditions such as hypoxia, sustained inflammation, and increased oxidative stress. CV-MSCs function normally in a high oxidative stress environment induced by hydrogen peroxide (H₂O₂) and glucose and also protect endothelial cells from their damaging effects. For their therapeutic applications in a disease like cancer, it is necessary to ascertain the effects of tumor microenvironment on their functional outcome. In this study, we investigated the functional activities, of CV-MSCs in response to conditioned media (CM) obtained from the culture of breast cancer cell line MDA-231 (CM-MDA231). CV-MSCs were exposed to CM-MDA231 for different spatio-temporal conditions, and their biological functions as well as modulation in gene expression were evaluated. Effect of CM-MDA231 on factors responsible for changes in functional outcome were also investigated at the protein levels. CV-MSCs exhibited significant reduction in proliferation but increased adhesion and migration after CM-MDA231 treatment. Interestingly, there was no change in their invasion potential. CM-MDA231 treatment modulated expression of various genes involved in important cellular events including, integration, survival, message delivery and favorable outcome after transplantation. Analysis of pathways related to cell cycle regulation revealed significant changes in the expression of p53, and increased phosphorylation of Retinoblastoma (Rb) and Checkpoint Kinase 2 in CV-MSCs treated with CM-MDA231. To summarize, these data reveal that CV-MSCs retain the ability to survive, adhere, and migrate after sustained treatment with CM-MDA231, a medium that mimics the cancer microenvironment. These properties of CV-MSCs to withstand the inflammatory tumor like microenvironment prove that they may make useful candidate in a stem cell based therapy against cancer. However, further pre-clinical studies are needed to validate their therapeutic usage.

Expression of therapy-induced senescence markers in breast cancer samples upon incomplete response to neoadjuvant chemotherapy

Senescence is a cell stress response induced by replicative, oxidative, oncogenic, and genotoxic stresses. Tumor cells undergo senescence in response to several cancer therapeutics in vitro (Therapy-Induced Senescence, TIS), including agents utilized as neoadjuvant chemotherapy (NAC) in the treatment of invasive breast cancer. TIS has been proposed to contribute to adverse therapy outcomes including relapse. However, there is limited evidence on the induction of senescence in response to NAC in clinical cancer and its contribution to disease outcomes. In this work, the expression of three senescence-associated markers (p21CIP1, H3K9Me3 (histone H3 lysine 9 trimethylation), and Lamin B1) was investigated in breast cancer samples that developed partial or incomplete pathological response to NAC (n=37). Accordingly, 40.54% of all samples showed marker expression consistent with a senescence-like phenotype, while the remainders were either negative or inconclusive for senescence (2.70 and 56.8%, respectively). Moreover, analysis of core-needle biopsies revealed minimal changes in p21CIP1 and H3K9Me3, but significant changes in Lamin B1 expression levels following NAC, highlighting a more predictive role of Lamin B1 in senescence detection. However, our analysis did not establish an association between TIS and cancer relapse as only three patients (8.1%) with a senescence-like profile developed short-term recurrent disease. Our analysis indicates that identification of TIS in tumor samples requires large-scale transcriptomic and protein marker analyses and extended clinical follow-up. Better understanding of in vivo senescence should elucidate its contribution to therapy outcomes and pave the way for the utilization of senolytic approaches as potential adjuvant cancer therapy.

The Role of Senescent Cells in Acquired Drug Resistance and Secondary Cancer in BRAFi-Treated Melanoma

BRAF is the most common gene mutated in malignant melanoma, and predominately it is a missense mutation of codon 600 in the kinase domain. This oncogenic BRAF missense mutation results in constitutive activation of the mitogen-activate protein kinase (MAPK) pro-survival pathway. Several BRAF inhibitors (BRAFi) have been developed to specifically inhibit BRAFV600 mutations that improve melanoma survival, but resistance and secondary cancer often occur. Causal mechanisms of BRAFi-induced secondary cancer and resistance have been identified through upregulation of MAPK and alternate pro-survival pathways. In addition, overriding of cellular senescence is observed throughout the progression of disease from benign nevi to malignant melanoma. In this review, we discuss melanoma BRAF mutations, the genetic mechanism of BRAFi resistance, and the evidence supporting the role of senescent cells in melanoma disease progression, drug resistance and secondary cancer. We further highlight the potential benefit of targeting senescent cells with senotherapeutics as adjuvant therapy in combating melanoma.

B7-H3 suppresses doxorubicin-induced senescence-like growth arrest in colorectal cancer through the AKT/TM4SF1/SIRT1 pathway

Emerging evidence suggests that cellular senescence induced by chemotherapy has been recognized as a new weapon for cancer therapy. This study aimed to research novel functions of B7-H3 in cellular senescence induced by a low dose of doxorubicin (DOX) in colorectal cancer (CRC). Here, our results demonstrated that B7-H3 knockdown promoted, while B7-H3 overexpression inhibited, DOX-induced cellular senescence. B7-H3 knockdown dramatically enhanced the growth arrest of CRC cells after low-dose DOX treatment, but B7-H3 overexpression had the opposite effect. By RNA-seq analysis and western blot, we showed that B7-H3 prevented cellular senescence and growth arrest through the AKT/TM4SF1/SIRT1 pathway. Blocking the AKT/TM4SF1/SIRT1 pathway dramatically reversed B7-H3-induced resistance to cellular senescence. More importantly, B7-H3 inhibited DOX-induced cellular senescence of CRC cells in vivo. Therefore, targeting B7-H3 or the B7-H3/AKT/TM4SF1/SIRT1 pathway might be a new strategy for promoting cellular senescence-like growth arrest during drug treatment in CRC.