Oncogene- and tumor suppressor gene-mediated suppression of cellular senescence

MiR-125b-1-3p-mediated UQCRB inhibition facilitates mitochondrial metabolism disorders in a rat cellular senescencemodel

BACKGROUD

Cellular senescence is closely related to human aging and multiple aging-related diseases, and impaired mitochondrial energy metabolism is an important mechanism of cellular senescence. Notably, microRNA-125b-1-3p (miR-125b-1-3p) is a microRNA (miR, miRNA) that may be associated with mitochondrial energy metabolism. Ubiquinol-cytochrome c reductase binding protein (UQCRB) gene, predicted by bioinformatics tools to be targeted by miR-125b-1-3p, could serve as a novel diagnostic indicator and therapeutic target for cellular senescence-associated diseases, as well as a new idea for delaying aging.

METHODS

First, the dual-luciferase reporter gene assay was used to identify UQCRB as a target gene of miR-125b-1-3p. Next, miRNA interference technology was conducted to verify that miR-125b-1-3p could negatively regulate the expression of UQCRB. Subsequently, the influence of miR-125b-1-3p on mitochondrial energy metabolism function was explored by observing the internal substances and ultrastructure of mitochondria. Further, an in vitro model of cellular senescence was established in rat renal tubular epithelial cells, which was characterized by detecting senescence-related proteins p16 and p21 and beta-galactosidase (β-gal) activity. Finally, the mitochondrial energy metabolism function of hydrogen peroxide (H2O2)-incubated cells was explored.

RESULTS

The experimental results revealed that miR-125b-1-3p affected the mitochondrial energy metabolism function by inhibiting the target gene UQCRB. Meanwhile, the level of mitochondrial energy metabolism function in H2O2-incubated senescent cells was lower than that in normal cells.

CONCLUSION

In this study, we identified the target gene, UQCRB, of miR-125b-1-3p, and demonstrated its role in the pathway of mitochondrial energy metabolism, as well as its possible effect on cellular senescence through this pathway. The ameliorative effects on cellular senescence can be further explored in subsequent studies to provide additional options for delaying aging or treating aging-related diseases.

p53/MDM2 signaling pathway in aging, senescence and tumorigenesis

A wealth of evidence has emerged that there is an association between aging, senescence and tumorigenesis. Senescence, a biological process by which cells cease to divide and enter a status of permanent cell cycle arrest, contributes to aging and aging-related diseases, including cancer. Aging populations have the higher incidence of cancer due to a lifetime of exposure to cancer-causing agents, reduction of repairing DNA damage, accumulated genetic mutations, and decreased immune system efficiency. Cancer patients undergoing cytotoxic therapies, such as chemotherapy and radiotherapy, accelerate aging. There is growing evidence that p53/MDM2 (murine double minute 2) axis is critically involved in regulation of aging, senescence and oncogenesis. Therefore, in this review, we describe the functions and mechanisms of p53/MDM2-mediated senescence, aging and carcinogenesis. Moreover, we highlight the small molecular inhibitors, natural compounds and PROTACs (proteolysis targeting chimeras) that target p53/MDM2 pathway to influence aging and cancer. Modification of p53/MDM2 could be a potential strategy for treatment of aging, senescence and tumorigenesis.

A new perspective on prostate cancer treatment: the interplay between cellular senescence and treatment resistance

The emergence of resistance to prostate cancer (PCa) treatment, particularly to androgen deprivation therapy (ADT), has posed a significant challenge in the field of PCa management. Among the therapeutic options for PCa, radiotherapy, chemotherapy, and hormone therapy are commonly used modalities. However, these therapeutic approaches, while inducing apoptosis in tumor cells, may also trigger stress-induced premature senescence (SIPS). Cellular senescence, an entropy-driven transition from an ordered to a disordered state, ultimately leading to cell growth arrest, exhibits a dual role in PCa treatment. On one hand, senescent tumor cells may withdraw from the cell cycle, thereby reducing tumor growth rate and exerting a positive effect on treatment. On the other hand, senescent tumor cells may secrete a plethora of cytokines, growth factors and proteases that can affect neighboring tumor cells, thereby exerting a negative impact on treatment. This review explores how radiotherapy, chemotherapy, and hormone therapy trigger SIPS and the nuanced impact of senescent tumor cells on PCa treatment. Additionally, we aim to identify novel therapeutic strategies to overcome resistance in PCa treatment, thereby enhancing patient outcomes.

METTL3-mediated HSPA9 m6A modification promotes malignant transformation and inhibits cellular senescence by regulating exosomal mortalin protein in cervical cancer

The role of RNA methyltransferase 3 (METTL3) in tumor progression when tethered to aberrantly expressed oncogenes remains unknown. In especial, the correlation between cervical cancer (CCa)-derived exosomes and m6A methylation in malignant traits of cervical epithelium is currently elusive. Mortalin expression was found to be up-regulated in plasma exosomes isolated from CCa patients. Furthermore, mortalin gained increased mRNA stability and enhanced translation efficiency via the m6A methylation in the HSPA9 mRNA 3'UTR, which was catalysed by METTL3 in CCa cells. Exosomal mortalin overexpression significantly promoted the proliferation, migration and invasion of CCa both in vitro and in vivo. Additionally, exosome-encapsulated mortalin suppressed cellular senescence and facilitated malignant transformation by blocking nuclear transport of p53, thereby preventing the p53-Gadd45A interaction and resulting in inactivation of p53. Our studies demonstrated the significant role of METTL3 mediated exosomal mortalin in malignant transformation and cellular senescence suppression of CCa. Exosomal mortalin could clinically serve as a potential early-diagnosis biomarker and therapeutic target for CCa given its abundance and propensity to be found.

The ATR inhibitor elimusertib exhibits anti-lymphoma activity and synergizes with the PI3K inhibitor copanlisib

The DNA damage response (DDR) is the cellular process of preserving an intact genome and is often deregulated in lymphoma cells. The ataxia telangiectasia and Rad3-related (ATR) kinase is a crucial factor of DDR in the response to DNA single-strand breaks. ATR inhibitors are agents that have shown considerable clinical potential in this context. We characterized the activity of the ATR inhibitor elimusertib (BAY 1895344) in a large panel of lymphoma cell lines. Furthermore, we evaluated its activity combined with the clinically approved PI3K inhibitor copanlisib in vitro and in vivo. Elimusertib exhibits potent anti-tumour activity across various lymphoma subtypes, which is associated with the expression of genes related to replication stress, cell cycle regulation and, as also sustained by CRISPR Cas9 experiments, CDKN2A loss. In several tumour models, elimusertib demonstrated widespread anti-tumour activity stronger than ceralasertib, another ATR inhibitor. This activity is present in both DDR-proficient and DDR-deficient lymphoma models. Furthermore, a combination of ATR and PI3K inhibition by treatment with elimusertib and copanlisib has in vitro and in vivo anti-tumour activity, providing a potential new treatment option for lymphoma patients.

The effect of Dendrobium officinale extract in inhibiting the senescence of H2 O2 -induced fibroblasts based on the senescence-associated secretory phenotype

BACKGROUND

Dendrobium officinale is widely used for a long time in China, with effect of antioxidation, antitumor, enhancing immunity and so on. In recent years, Dendrobium officinale has been gradually used in cosmetics due to its powerful beauty effects.

AIMS

Based on senescence-associated secretory phenotype (SASP), we studied the antiaging effect of Dendrobium officinale extract (DOE) on skin.

METHODS

The senescent model of human skin fibroblasts was established by the induction of H2 O2 , and the content of SASP factors was tested after the treatment of DOE, such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-1 (MMP-1).

RESULTS

It was found that after the treatment with different concentrations of DOE, the contents of IL-6, MCP-1 and MMP-1 all decreased in different degrees.

CONCLUSIONS

It indicated that DOE could inhibit the secretion of SASP factors and was a promising natural antiaging agent.

Biosynthesis of anticancer phytochemical compounds and their chemistry

Cancer is a severe health issue, and cancer cases are rising yearly. New anticancer drugs have been developed as our understanding of the molecular mechanisms behind diverse solid tumors, and metastatic malignancies have increased. Plant-derived phytochemical compounds target different oncogenes, tumor suppressor genes, protein channels, immune cells, protein channels, and pumps, which have attracted much attention for treating cancer in preclinical studies. Despite the anticancer capabilities of these phytochemical compounds, systemic toxicity, medication resistance, and limited absorption remain more significant obstacles in clinical trials. Therefore, drug combinations of new phytochemical compounds, phytonanomedicine, semi-synthetic, and synthetic analogs should be considered to supplement the existing cancer therapies. It is also crucial to consider different strategies for increased production of phytochemical bioactive substances. The primary goal of this review is to highlight several bioactive anticancer phytochemical compounds found in plants, preclinical research, their synthetic and semi-synthetic analogs, and clinical trials. Additionally, biotechnological and metabolic engineering strategies are explored to enhance the production of bioactive phytochemical compounds. Ligands and their interactions with their putative targets are also explored through molecular docking studies. Therefore, emphasis is given to gathering comprehensive data regarding modern biotechnology, metabolic engineering, molecular biology, and in silico tools.

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

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

Detection of Cellular Senescence in Human Primary Melanocytes and Malignant Melanoma Cells In Vitro

Detection and quantification of senescent cells remain difficult due to variable phenotypes and the absence of highly specific and reliable biomarkers. It is therefore widely accepted to use a combination of multiple markers and cellular characteristics to define senescent cells in vitro. The exact choice of these markers is a subject of ongoing discussion and usually depends on objective reasons such as cell type and treatment conditions, as well as subjective considerations including feasibility and personal experience. This study aims to provide a comprehensive comparison of biomarkers and cellular characteristics used to detect senescence in melanocytic systems. Each marker was assessed in primary human melanocytes that overexpress mutant BRAFV600E, as it is commonly found in melanocytic nevi, and melanoma cells after treatment with the chemotherapeutic agent etoposide. The combined use of these two experimental settings is thought to allow profound conclusions on the choice of senescence biomarkers when working with melanocytic systems. Further, this study supports the development of standardized senescence detection and quantification by providing a comparative analysis that might also be helpful for other cell types and experimental conditions.

Prognostic and Immunotherapeutic Roles of KRAS in Pan-Cancer

KRAS is one well-established tumor-driver gene associated with cancer initiation, development, and progression. Nonetheless, comparative studies of the relevance of KRAS across diverse tumors remain sparse. We explored the KRAS expression and prognostic values in diverse cancer types via multiple web-based bioinformatics tools, including cBioPortal, Oncomine, PrognoScan, Kaplan–Meier Plotter, etc. We found that KRAS is highly expressed in various malignancies compared to normal cohorts (BRCA, CHOL, ESCA, HNSC, LIHC, LUAD, LUSC, and STAD) and less expressed in COAD, KIRC, READ, and THCA than in normal samples. We observed the dysregulation of the DNA methylation of KRAS in cancers and discovered that numerous oncogenic and tumor-suppressive transcription factors bind the KRAS promoter region. Pan-cancer analysis also showed that a high level of KRAS is associated with poor outcomes. Additionally, KRAS is remarkably correlated with the level of immune cell infiltration and tumorigenic gene signatures. In conclusion, our findings reveal novel insights into KRAS expression and its biological functions in diverse cancer types, indicating that KRAS could serve as a prognostic biomarker and is associated with immune infiltrates.

Role of Lysosomal Acidification Dysfunction in Mesenchymal Stem Cell Senescence

Mesenchymal stem cell (MSC) transplantation has been widely used as a potential treatment for a variety of diseases. However, the contradiction between the low survival rate of transplanted cells and the beneficial therapeutic effects has affected its clinical use. Lysosomes as organelles at the center of cellular recycling and metabolic signaling, play essential roles in MSC homeostasis. In the first part of this review, we summarize the role of lysosomal acidification dysfunction in MSC senescence. In the second part, we summarize some of the potential strategies targeting lysosomal proteins to enhance the therapeutic effect of MSCs.

The Epithelial-Stromal Microenvironment in Early Colonic Neoplasia

Stromal cells play a central role in promoting the progression of colorectal cancer. Here, we analyze molecular changes within the epithelial and stromal compartments of dysplastic aberrant crypt foci (ACF) formed in the ascending colon, where rapidly developing interval cancers occur. We found strong activation of numerous neutrophil/monocyte chemokines, consistent with localized inflammation. The data also indicated a decrease in interferon signaling and cell-based immunity. The immune checkpoint and T-cell exhaustion gene PDCD1 was one of the most significantly upregulated genes, which was accompanied by a decrease in cytotoxic T-cell effector gene expression. In addition, CDKN2A expression was strongly upregulated in the stroma and downregulated in the epithelium, consistent with diverse changes in senescence-associated signaling on the two tissue compartments. IMPLICATIONS: Decreased CD8 T-cell infiltration within proximal colon ACF occurs within the context of a robust inflammatory response and potential stromal cell senescence, thus providing new insight into potential promotional drivers for tumors in the proximal colon.

CKAP2L, as an Independent Risk Factor, Closely Related to the Prognosis of Glioma

Recent studies have found that cytoskeleton-associated protein 2 like (CKAP2L), an important oncogene, is involved in the biological behavior of many malignant tumors, but its function in the malignant course of glioma has not been confirmed. The main purpose of this study was to clarify the relationship between prognostic clinical characteristics of glioma patients and CKAP2L expression using data collected from the GEPIA, HPA, CGGA, TCGA, and GEO databases. CKAP2L expression was significantly increased in glioma. Further, Kaplan-Meier plots revealed that increased expression of CKAP2L was associated with shorter survival time of glioma patients in datasets retrieved from multiple databases. Cox regression analysis indicated that CKAP2L can serve as an independent risk factor but also has relatively reliable diagnostic value for the prognosis of glioma patients. The results of gene set enrichment analysis suggested that CKAP2L may play a regulatory role through the cell cycle, homologous recombination, and N-glycan biosynthesis cell signaling pathways. Several drugs with potential inhibitory effects on CKAP2L were identified in the CMap database that may have therapeutic effects on glioma. Finally, knockdown of CKAP2L inhibited the proliferation and invasion of cells by reducing the expression level of cell cycle-related proteins. This is the first study to demonstrate that high CKAP2L expression leads to poor prognosis in glioma patients, providing a novel target for diagnosis and treatment of glioma.

Expression of oncogenic HRAS in human Rh28 and RMS-YM rhabdomyosarcoma cells leads to oncogene-induced senescence

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma. The two predominant histologic variants of RMS, embryonal and alveolar rhabdomyosarcoma (eRMS and aRMS, respectively), carry very different prognoses. While eRMS is associated with an intermediate prognosis, the 5-year survival rate of aRMS is less than 30%. The RMS subtypes are also different at the molecular level-eRMS frequently has multiple genetic alterations, including mutations in RAS and TP53, whereas aRMS often has chromosomal translocations resulting in PAX3-FOXO1 or PAX7-FOXO1 fusions, but otherwise has a "quiet" genome. Interestingly, mutations in RAS are rarely found in aRMS. In this study, we explored the role of oncogenic RAS in aRMS. We found that while ectopic oncogenic HRAS expression was tolerated in the human RAS-driven eRMS cell line RD, it was detrimental to cell growth and proliferation in the human aRMS cell line Rh28. Growth inhibition was mediated by oncogene-induced senescence and associated with increased RB pathway activity and expression of the cyclin-dependent kinase inhibitors p16 and p21. Unexpectedly, the human eRMS cell line RMS-YM, a RAS wild-type eRMS cell line, also exhibited growth inhibition in response to oncogenic HRAS in a manner similar to aRMS Rh28 cells. This work suggests that oncogenic RAS is expressed in a context-dependent manner in RMS and may provide insight into the differential origins and therapeutic opportunities for RMS subtypes.

Simultaneous Targeting Tumor Cells and Cancer-Associated Fibroblasts with a Paclitaxel-Hyaluronan Bioconjugate: In Vitro Evaluation in Non-Melanoma Skin Cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs) facilitate many aspects of cancer development by providing a structural framework rich in bioactive compounds. There are emerging studies proposing a combination of conventional anti-cancer therapies directed against neoplastic cells to molecules targeting tumor microenvironments.

METHODS

The study evaluated the pharmacological properties of the anti-tumor agent paclitaxel conjugated to hyaluronic acid (HA) regarding non-melanoma skin cancer (NMSC) and the surrounding fibroblasts. This molecule, named Oncofid-P20 (Onco-P20), preferentially targets cells expressing high levels of CD44, the natural ligand of HA.

RESULTS

Consistent with paclitaxel's mechanism of action involving interference with the breakdown of microtubules during cell division, highly sensitive carcinoma cells rapidly underwent apoptotic cell death. Interestingly, less sensitive cells, such as dermal fibroblasts, resisted the Onco-P20 treatment and experienced a prolonged growth arrest characterized by morphological change and significant modification of the gene expression profile. Onco-P20-treated fibroblasts exhibited reduced growth factor production, downmodulation of the Wnt signaling pathway, and the acquisition of a marked pro-inflammatory profile. Independently of direct exposure to taxol, in the presence of Onco-P20-treated fibroblasts or in their conditioned medium, carcinoma cells had a reduced proliferation rate. Similar to NHF, fibroblasts isolated from skin cancer lesions or from adjacent tissue acquired anti-neoplastic activity under Onco-P20 treatment.

CONCLUSION

Collectively, our data demonstrate that Onco-P20, exerting both a direct and an NHF-mediated indirect effect on carcinoma cells, is a candidate for an innovative therapy alternative to surgery for the treatment of NMSC.

Molecular mechanisms and cardiovascular implications of cancer therapy-induced senescence

Cancer treatment has been associated with accelerated aging that can lead to early-onset health complications typically experienced by older populations. In particular, cancer survivors have an increased risk of developing premature cardiovascular complications. In the last two decades, cellular senescence has been proposed as an important mechanism of premature cardiovascular diseases. Cancer treatments, specifically anthracyclines and radiation, have been shown to induce senescence in different types of cardiovascular cells. Additionally, clinical studies identified increased systemic markers of senescence in cancer survivors. Preclinical research has demonstrated the potential of several approaches to mitigate cancer therapy-induced senescence. However, strategies to prevent and/or treat therapy-induced cardiovascular senescence have not yet been translated to the clinic. In this review, we will discuss how therapy-induced senescence can contribute to cardiovascular complications. Thereafter, we will summarize the current in vitro, in vivo, and clinical evidence regarding cancer therapy-induced cardiovascular senescence. Then, we will discuss interventional strategies that have the potential to protect against therapy-induced cardiovascular senescence. To conclude, we will highlight challenges and future research directions to mitigate therapy-induced cardiovascular senescence in cancer survivors.

Targeting Premature Renal Aging: from Molecular Mechanisms of Cellular Senescence to Senolytic Trials

The biological process of renal aging is characterized by progressive structural and functional deterioration of the kidney leading to end-stage renal disease, requiring renal replacement therapy. Since the discovery of pivotal mechanisms of senescence such as cell cycle arrest, apoptosis inhibition, and the development of a senescence-associated secretory phenotype (SASP), efforts in the understanding of how senescent cells participate in renal physiological and pathological aging have grown exponentially. This has been encouraged by both preclinical studies in animal models with senescent cell clearance or genetic depletion as well as due to evidence coming from the clinical oncologic experience. This review considers the molecular mechanism and pathways that trigger premature renal aging from mitochondrial dysfunction, epigenetic modifications to autophagy, DNA damage repair (DDR), and the involvement of extracellular vesicles. We also discuss the different pharmaceutical approaches to selectively target senescent cells (namely, senolytics) or the development of systemic SASP (called senomorphics) in basic models of CKD and clinical trials. Finally, an overview will be provided on the potential opportunities for their use in renal transplantation during ex vivo machine perfusion to improve the quality of the graft.

Small Molecule Inhibitors Targeting Key Proteins in the DNA Damage Response for Cancer Therapy

DNA damage response (DDR) is a complicated interactional pathway. Defects that occur in subordinate pathways of the DDR pathway can lead to genomic instability and cancer susceptibility. Abnormal expression of some proteins in DDR, especially in the DNA repair pathway, are associated with the subsistence and resistance of cancer cells. Therefore, the development of small molecule inhibitors targeting the chief proteins in the DDR pathway is an effective strategy for cancer therapy. In this review, we summarize the development of small molecule inhibitors targeting chief proteins in the DDR pathway, particularly focusing on their implications for cancer therapy. We present the action mode of DDR molecule inhibitors in preclinical studies and clinical cancer therapy, including monotherapy and combination therapy with chemotherapeutic drugs or checkpoint suppression therapy.

Non-Coding RNAs Steering the Senescence-Related Progress, Properties, and Application of Mesenchymal Stem Cells

The thirst to postpone and even reverse aging progress has never been quenched after all these decades. Unequivocally, mesenchymal stem cells (MSCs), with extraordinary abilities such as self-renewal and multi-directional differentiation, deserve the limelight in this topic. Though having several affable clinical traits, MSCs going through senescence would, on one hand, contribute to age-related diseases and, on the other hand, lead to compromised or even counterproductive therapeutical outcomes. Notably, increasing evidence suggests that non-coding RNAs (ncRNAs) could invigorate various regulatory processes. With even a slight dip or an uptick of expression, ncRNAs would make a dent in or even overturn cellular fate. Thereby, a systematic illustration of ncRNAs identified so far to steer MSCs during senescence is axiomatically an urgent need. In this review, we introduce the general properties and mechanisms of senescence and its relationship with MSCs and illustrate the ncRNAs playing a role in the cellular senescence of MSCs. It is then followed by the elucidation of ncRNAs embodied in extracellular vesicles connecting senescent MSCs with other cells and diversified processes in and beyond the skeletal system. Last, we provide a glimpse into the clinical methodologies of ncRNA-based therapies in MSC-related fields. Hopefully, the intricate relationship between senescence and MSCs will be revealed one day and our work could be a crucial stepping-stone toward that future.

Methods to Study Myc-Regulated Cellular Senescence: An Update

Cellular senescence plays a role in several physiological processes including aging, embryonic development, tissue remodeling, and wound healing and is considered one of the main barriers against tumor development. Studies of normal and tumor cells both in culture and in vivo suggest that MYC plays an important role in regulating senescence, thereby contributing to tumor development. We have previously described different common methods to measure senescence in cell cultures and in tissues. Unfortunately, there is no unique marker that unambiguously defines a senescent state, and it is therefore necessary to combine measurements of several different markers in order to assure the correct identification of senescent cells. Here we describe protocols for simultaneous detection of multiple senescence markers in situ, a quantitative fluorogenic method to measure senescence-associated β-galactosidase activity (SA-β-gal), and a new method to detect senescent cells based on the Sudan Black B (SBB) analogue GL13, which is applicable to formalin-fixed paraffin-embedded tissues. The application of these methods in various systems will hopefully shed further light on the role of MYC in regulation of senescence, and how that impacts normal physiological processes as well as diseases and in particular cancer development.

Ageing and mesenchymal stem cells derived exosomes: Molecular insight and challenges

Ageing induces a great risk factor that participates in progressing various degenerative diseases morbidities. The main characteristic of ageing is the failure in maintaining homeostasis in the organs with a cellular senescence. Senescence is characterized by reduced cell growth, evade cellular death, and acquiring a senescence-associated secretory phenotype (SASP). Mesenchymal stem cells (MSCs) are advantageous cells in regenerative medicine, exerting pleiotropic functions by producing soluble factors, such as exosomes. MSCs and their exosomes (MSCs-Exo) kinetic are affected by ageing and other aged exosomes. Exosomes biogenesis from aged MSCs is accelerated and their exosomal cargoes, such as miRNAs, vary as compared to those of normal cells. Besides, exosomes from aged MSCs loss their regenerative potential and may negatively influence the function of recipient cells. MSCs-Exo can improve ageing and age-related diseases; however, the detailed mechanisms remain yet elusive. Although exosomes-therapy may serve as a new approach to combat ageing, the translation of preclinical results to clinic needs more extensive investigation on exosomes both on their biology and related techniques. Overall, scrutiny on the effect of ageing on MSCs and vice versa is vital for designing novel therapy using MSCs with focus on the management of older individuals.

Cellular senescence and cancer: Focusing on traditional Chinese medicine and natural products

Cancer is the principal cause of death and a dominant public health problem which seriously threatening human life. Among various ways to treat cancer, traditional Chinese medicine (TCM) and natural products have outstanding anti‐cancer effects with their unique advantages of high efficiency and minimal side effects. Cell senescence is a physiological process of cell growth stagnation triggered by stress, which is an important line of defence against tumour development. In recent years, active ingredients of TCM and natural products, as an interesting research hotspot, can induce cell senescence to suppress the occurrence and development of tumours, by inhibiting telomerase activity, triggering DNA damage, inducing SASP, and activating or inactivating oncogenes. In this paper, the recent research progress on the main compounds derived from TCM and natural products that play anti‐cancer roles by inducing cell senescence is systematically reviewed, aiming to provide a reference for the clinical treatment of pro‐senescent cancer.

Phenotypic screening using large-scale genomic libraries to identify drug targets for the treatment of cancer

During malignant progression to overt cancer cells, normal cells accumulate multiple genetic and non-genetic changes, which result in the acquisition of various oncogenic properties, such as uncontrolled proliferation, drug resistance, invasiveness, anoikis-resistance, the ability to bypass oncogene-induced senescence and cancer stemness. To identify potential novel drug targets contributing to these malignant phenotypes, researchers have performed large-scale genomic screening using various in vitro and in vivo screening models and identified numerous promising cancer drug target genes. However, there are issues with these identified genes, such as low reproducibility between different datasets. In the present study, the recent advances in the functional screening for identification of cancer drug target genes are summarized, and current issues and future perspectives are discussed.

Mesenchymal Stem Cell Derived Extracellular Vesicles in Aging

Aging is associated with high prevalence of chronic degenerative diseases that take a large part of the increasing burden of morbidities in a growing demographic of elderly people. Aging is a complex process that involves cell autonomous and cell non-autonomous mechanisms where senescence plays an important role. Senescence is characterized by the loss of proliferative potential, resistance to cell death by apoptosis and expression of a senescence-associated secretory phenotype (SASP). SASP includes pro-inflammatory cytokines and chemokines, tissue-damaging proteases, growth factors; all contributing to tissue microenvironment alteration and loss of tissue homeostasis. Emerging evidence suggests that the changes in the number and composition of extracellular vesicles (EVs) released by senescent cells contribute to the adverse effects of senescence in aging. In addition, age-related alterations in mesenchymal stem/stromal cells (MSCs) have been associated to dysregulated functions. The loss of functional stem cells necessary to maintain tissue homeostasis likely directly contributes to aging. In this review, we will focus on the characteristics and role of EVs isolated from senescent MSCs, the potential effect of MSC-derived EVs in aging and discuss their therapeutic potential to improve age-related diseases.

Identification of COMMD1 as a novel lamin A binding partner

Lamin A, which is encoded by the LMNA gene, regulates gene expression and genome stability through interactions with a variety of proteins. Mutations in LMNA lead to a diverse set of inherited human diseases, collectively referred to as laminopathies. To gain insight into the protein interactions of lamin A, a yeast two-hybrid screen was conducted using the carboxy-terminus of lamin A. The screen identified copper metabolism MURR1 domain-containing 1 (COMMD1) as a novel lamin A binding partner. Colocalization experiments using fluorescent confocal microscopy revealed that COMMD1 colocalized with lamin A in 293 cells. Furthermore, the COMMD1-lamin A protein interaction was also demonstrated in co-immunoprecipitation experiments. Collectively, the present study demonstrated a physical interaction between COMMD1 and lamin A, which may aid to elucidate the mechanisms of lamin A in the aging process.

Cellular plasticity and metastasis in breast cancer: a pre- and post-malignant problem

As a field we have made tremendous strides in treating breast cancer, with a decline in the past 30 years of overall breast cancer mortality. However, this progress is met with little affect once the disease spreads beyond the primary site. With a 5-year survival rate of 22%, 10-year of 13%, for those patients with metastatic breast cancer (mBC), our ability to effectively treat wide spread disease is minimal. A major contributing factor to this ineffectiveness is the complex make-up, or heterogeneity, of the primary site. Within a primary tumor, secreted factors, malignant and pre-malignant epithelial cells, immune cells, stromal fibroblasts and many others all reside alongside each other creating a dynamic environment contributing to metastasis. Furthermore, heterogeneity contributes to our lack of understanding regarding the cells' remarkable ability to undergo epithelial/non-cancer stem cell (CSC) to mesenchymal/CSC (E-M/CSC) plasticity. The enhanced invasion & motility, tumor-initiating potential, and acquired therapeutic resistance which accompanies E-M/CSC plasticity implicates a significant role in metastasis. While most work trying to understand E-M/CSC plasticity has been done on malignant cells, recent evidence is emerging concerning the ability for pre-malignant cells to undergo E-M/CSC plasticity and contribute to the metastatic process. Here we will discuss the importance of E-M/CSC plasticity within malignant and pre-malignant populations of the tumor. Moreover, we will discuss how one may potentially target these populations, ultimately disrupting the metastatic cascade and increasing patient survival for those with mBC.

Synaptotagmin-7, a binding protein of P53, inhibits the senescence and promotes the tumorigenicity of lung cancer cells

Lung cancer has been one of the most common malignancies in the world. Cell senescence has been recognized as the avenue to inhibit tumor progression. However, the mechanisms remain poorly understood. In the present study, we have shown that synaptotagmin-7 (SYT7) expression was up-regulated in lung cancer. SYT7 also promoted the growth and colony formation of lung cancer cells and inhibited their senescence. In a molecular mechanism study, SYT7 was shown to interact with P53 and to potentiate the interaction between P53 and MDM2. Taken together, the present study demonstrates the oncogenic roles of SYT7 in lung cancer, and suggests that SYT7 may be a good therapeutic target for lung cancer treatment.

ID1-induced p16/IL6 axis activation contributes to the resistant of hepatocellular carcinoma cells to sorafenib

Sorafenib is the only approved drug for the treatment of advanced hepatocellular carcinoma (HCC). However, its efficacy is limited by the emergence of primary and/or acquired resistance. Senescence-associated secretory phenotype (SASP)-mediated chemo-resistance, which depends on the secreted bioactive molecules, has attracted increasing attention but never revealed in HCC. In this study, we investigated the effect of SASP-related p16/IL6 axis on sorafenib resistance in HCC. Initially, we noticed that HCC cells with a high level of p16/IL6 axis exhibited a low sensitivity to sorafenib. Further in vivo and in vitro studies demonstrated that such a primary resistance resulted from ID1-mediated activation of p16/IL6 axis. Overexpression of ID1 or IL6 blocking in sorafenib-resistant HCC cells could increase the cytotoxicity of sorafenib. Moreover, SASP-related p16/IL6 axis contributed to the formation of acquired resistance in cells received long-term exposure to sorafenib. In acquired sorafenib-resistant cells, ID1 low expression, p16/IL6 axis up-regulation, and AKT phosphorylation activation were observed. A reduced cytotoxicity of sorafenib was detected when sorafenib-sensitive cells incubated with conditioned media from the resistant cells, accompanied by the stimulation of AKT phosphorylation. The reversal of sorafenib resistance could be achieved through ID1 overexpression, IL6 blocking, and AKT pathway inhibition. Our study reveals that SASP-related p16/IL6 axis activation is responsible for sorafenib resistance, which will be a novel strategy to prevent the drug resistance.

Genomic and Functional Approaches to Understanding Cancer Aneuploidy

Aneuploidy, whole chromosome or chromosome arm imbalance, is a near-universal characteristic of human cancers. In 10,522 cancer genomes from The Cancer Genome Atlas, aneuploidy was correlated with TP53 mutation, somatic mutation rate, and expression of proliferation genes. Aneuploidy was anti-correlated with expression of immune signaling genes, due to decreased leukocyte infiltrates in high-aneuploidy samples. Chromosome arm-level alterations show cancer-specific patterns, including loss of chromosome arm 3p in squamous cancers. We applied genome engineering to delete 3p in lung cells, causing decreased proliferation rescued in part by chromosome 3 duplication. This study defines genomic and phenotypic correlates of cancer aneuploidy and provides an experimental approach to study chromosome arm aneuploidy.

Molecular mechanisms and therapeutic targets in neuroblastoma

Neuroblastoma is the most common extracranical tumor of childhood and the most deadly tumor of infancy. It is characterized by early age onset and high frequencies of metastatic disease but also the capacity to spontaneously regress. Despite intensive therapy, the survival for patients with high-risk neuroblastoma and those with recurrent or relapsed disease is low. Hence, there is an urgent need to develop new therapies for these patient groups. The molecular pathogenesis based on high-throughput omics technologies of neuroblastoma is beginning to be resolved which have given the opportunity to develop personalized therapies for high-risk patients. Here we discuss the potential of developing targeted therapies against aberrantly expressed molecules detected in sub-populations of neuroblastoma patients and how these selected targets can be drugged in order to overcome treatment resistance, improve survival and quality of life for these patients and also the possibilities to transfer preclinical research into clinical testing.

Cellular senescence in gastrointestinal diseases: from pathogenesis to therapeutics

Senescence is a durable cell cycle arrest that can be induced in response to various stress factors, such as telomere erosion, DNA damage or the aberrant activation of oncogenes. In addition to its well-established role as a stress response programme, research has revealed important physiological roles of senescence in nondisease settings, such as embryonic development, wound healing, tissue repair and ageing. Senescent cells secrete various cytokines, chemokines, matrix remodelling proteases and growth factors, a phenotype collectively referred to as the senescence-associated secretory phenotype. These factors evoke immune responses that, depending on the pathophysiological context, can either prevent or even fuel disease and tumorigenesis. Remarkably, even the gut microbiota can influence senescence in various organs. In this Review, we provide an introduction to cellular senescence, addressed particularly to gastroenterologists and hepatologists, and discuss the implications of senescence for the pathogenesis of malignant and nonmalignant gastrointestinal and hepatobiliary diseases. We conclude with an outlook on how modulation of cellular senescence might be used for therapeutic purposes.

The Immortal Senescence

Activation of oncogenic signaling paradoxically results in the permanent withdrawal from cell cycle and induction of senescence (oncogene-induced senescence (OIS)). OIS is a fail-safe mechanism used by the cells to prevent uncontrolled tumor growth, and, as such, it is considered as the first barrier against cancer. In order to progress, tumor cells thus need to first overcome the senescent phenotype. Despite the increasing attention gained by OIS in the past 20 years, this field is still rather young due to continuous emergence of novel pathways and processes involved in OIS. Among the many factors contributing to incomplete understanding of OIS are the lack of unequivocal markers for senescence and the complexity of the phenotypes revealed by senescent cells in vivo and in vitro. OIS has been shown to play major roles at both the cellular and organismal levels in biological processes ranging from embryonic development to barrier to cancer progression. Here we will briefly outline major advances in methodologies that are being utilized for induction, identification, and characterization of molecular processes in cells undergoing oncogene-induced senescence. The full description of such methodologies is provided in the corresponding chapters of the book.

Noncoding RNAs in DNA Damage Response: Opportunities for Cancer Therapeutics

DNA repair machinery preserves genomic integrity, which is frequently challenged through endogenous and exogenous toxic insults, and any sort of repair machinery malfunctioning ultimately manifests in the form of several types of terrible human diseases such as cancers (Hoeijmakers, Nature 411(6835): 366-374, 2001). Noncoding RNAs (ncRNAs) are crucial players of DNA repair machinery in a cell and play a vital role in maintaining genomic stability, which is essential for its survival and normal functioning thus preventing tumorigenesis. To preserve the integrity of the genome, cells initiate a specific cellular response, recognized as DNA damage response (DDR), which includes several distinct DNA repair pathways. These repair pathways permit normal cells to repair DNA damage or induce apoptosis and cell cycle arrest in case the damage is irreparable. Disruption of these pathways in cancer leads to an increase in genomic instability and mutagenesis. Recently, emerging evidence suggests that ncRNAs play a critical role in the regulation of DDR. There is an extensive crosstalk between ncRNAs and the canonical DDR signaling pathway. DDR-induced expression of ncRNAs can provide a regulatory mechanism to accurately control the expression of DNA damage responsive genes in a spatio-temporal manner. DNA damage alters expression of a variety of ncRNAs at multiple levels including transcriptional regulation, post-transcriptional regulation, and RNA degradation and vice versa, wherein ncRNAs can directly regulate cellular processes involved in DDR by altering expression of their targeting genes, with a particular emphasis on microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). Relationship between the defects in the DDR and deregulation of related ncRNAs in human cancers is one of the established, which is growing stronger with the advent of high-throughput sequencing techniques such as next-generation sequencing. Understanding of the mechanisms that explain the association between ncRNAs and DDR/DNA repair pathways will definitely increase our understanding on human tumor biology and on different responses to diverse drugs. Different ncRNAs interact with distinct DDR components and are promising targets for improving the effects to overcome the resistance to conventional chemotherapeutic agents. In this chapter, we will focus the role of ncRNAs in the DNA damage, repair, and cancer.

Cellular senescence, senescence-associated secretory phenotype, and chronic kidney disease

Chronic kidney disease (CKD) is increasingly being accepted as a type of renal ageing. The kidney undergoes age-related alterations in both structure and function. To date, a comprehensive analysis of cellular senescence and senescence-associated secretory phenotype (SASP) in CKD is lacking. Hence, this review mainly discusses the relationship between the two phenomena to show the striking similarities between SASP and CKD-associated secretory phenotype (CASP). It has been reported that replicative senescence, stress-induced premature ageing, and epigenetic abnormalities participate in the occurrence and development of CKD. Genomic damage and external environmental stimuli cause increased levels of oxidative stress and a chronic inflammatory state as a result of irreversible cell cycle arrest and low doses of SASP. Similar to SASP, CASP factors activate tissue repair by multiple mechanisms. Once tissue repair fails, the accumulated SASP or CASP species aggravate DNA damage response (DDR) and cause the senescent cells to secrete more SASP factors, accelerating the process of cellular ageing and eventually leading to various ageing-related changes. It is concluded that cellular senescence and SASP participate in the pathological process of CKD, and correspondingly CKD accelerated the progression of cell senescence and the secretion of SASP. These results will facilitate the integration of these mechanisms into the care and management of CKD and other age-related diseases.

p53 loss does not permit escape from BrafV600E-induced senescence in a mouse model of lung cancer

Lung cancer arises through the acquisition of a number of genetic lesions, with a preponderance of activating mutations in the canonical mitogen-activated protein kinase (MAPK) cascade (RTK-RAS-RAF-MEK). Braf^V600E expression induces benign lung adenomas that fail to progress to adenocarcinoma because of oncogene-induced senescence (OIS). Braf^V600E expression, coupled with simultaneous p53 ablation, permits bypass of senescence and progression to lung adenocarcinoma. However, spontaneous human tumors sustain mutations in a temporally separated manner. Here, we use a mouse lung cancer model where oncogene activation (Braf^V600E expression) and tumor suppressor loss (p53 ablation) are independently controlled through the actions of Flp and Cre recombinase, respectively. We show that p53 loss before OIS is permissive for the transition from lung adenoma to adenocarcinoma. In contrast, p53 loss after senescence is established fails to enable escape from senescence and disease progression. This study demonstrates that Braf^V600E induced senescence is irreversible in vivo and suggests that therapy-induced senescence would halt further tumor progression.

Induction of accelerated senescence by the microtubule-stabilizing agent peloruside A

Chemotherapeutic agents can induce accelerated senescence in tumor cells, an irreversible state of cell cycle arrest. Paclitaxel, a microtubule-stabilizing agent used to treat solid tumors of the breast, ovary, and lung and discodermolide, another stabilizing agent from a marine sponge, induce senescence in cultured cancer cells. The aim of this study was to determine if the microtubule-stabilizing agent peloruside A, a polyketide natural product from a marine sponge, can induce accelerated senescence in a breast cancer cell line MCF7. Doxorubicin, a DNA-damaging agent, paclitaxel, and discodermolide were used as positive controls. Senescence-associated-β-galactosidase activity was increased by peloruside A, similar to paclitaxel, discodermolde, and doxorubicin, with a potency heirarchy of doxorubicin > paclitaxel > discodermolide > peloruside, based on IC₂₅ concentrations that inhibit proliferation. Clonogenic survival was significantly decreased by peloruside A, similar to doxorubicin and the two other microtubule-stabilizing agents. The tumor suppressor protein p53 increased after treatment, whereas pRb decreased in response to all four compounds. It was concluded that in addition to apoptosis, peloruside A causes accelerated senescence in a subpopulation of MCF7 cells that contributes to its potential anticancer activity in a breast cancer cell line.

Asxl1 deficiency in embryonic fibroblasts leads to cellular senescence via impairment of the AKT-E2F pathway and Ezh2 inactivation

Although ASXL1 mutations are frequently found in human diseases, including myeloid leukemia, the cell proliferation-associated function of ASXL1 is largely unknown. Here, we explored the molecular mechanism underlying the growth defect found in Asxl1-deficient mouse embryonic fibroblasts (MEFs). We found that Asxl1, through amino acids 371 to 655, interacts with the kinase domain of AKT1. In Asxl1-null MEFs, IGF-1 was unable to induce AKT1 phosphorylation and activation; p27Kip1, which forms a ternary complex with ASXL1 and AKT1, therefore remained unphosphorylated. Hypophosphorylated p27Kip1 is able to enter the nucleus, where it prevents the phosphorylation of Rb; this ultimately leads to the down-regulation of E2F target genes as confirmed by microarray analysis. We also found that senescence-associated (SA) genes were upregulated and that SA β-gal staining was increased in Asxl1 ^-/- MEFs. Further, the treatment of an AKT inhibitor not only stimulated nuclear accumulation of p27Kip1 leading to E2F inactivation, but also promoted senescence. Finally, Asxl1 disruption augmented the expression of p16Ink4a as result of the defect in Asxl1-Ezh2 cooperation. Overall, our study provides the first evidence that Asxl1 both activates the AKT-E2F pathway and cooperates with Ezh2 through direct interactions at early embryonic stages, reflecting that Asxl1 disruption causes cellular senescence.

MYC Modulation around the CDK2/p27/SKP2 Axis

MYC is a pleiotropic transcription factor that controls a number of fundamental cellular processes required for the proliferation and survival of normal and malignant cells, including the cell cycle. MYC interacts with several central cell cycle regulators that control the balance between cell cycle progression and temporary or permanent cell cycle arrest (cellular senescence). Among these are the cyclin E/A/cyclin-dependent kinase 2 (CDK2) complexes, the CDK inhibitor p27^KIP1 (p27) and the E3 ubiquitin ligase component S-phase kinase-associated protein 2 (SKP2), which control each other by forming a triangular network. MYC is engaged in bidirectional crosstalk with each of these players; while MYC regulates their expression and/or activity, these factors in turn modulate MYC through protein interactions and post-translational modifications including phosphorylation and ubiquitylation, impacting on MYC's transcriptional output on genes involved in cell cycle progression and senescence. Here we elaborate on these network interactions with MYC and their impact on transcription, cell cycle, replication and stress signaling, and on the role of other players interconnected to this network, such as CDK1, the retinoblastoma protein (pRB), protein phosphatase 2A (PP2A), the F-box proteins FBXW7 and FBXO28, the RAS oncoprotein and the ubiquitin/proteasome system. Finally, we describe how the MYC/CDK2/p27/SKP2 axis impacts on tumor development and discuss possible ways to interfere therapeutically with this system to improve cancer treatment.

High-Speed Atomic Force Microscopy Reveals Loss of Nuclear Pore Resilience as a Dying Code in Colorectal Cancer Cells

Nuclear pore complexes (NPCs) are the sole turnstile implanted in the nuclear envelope (NE), acting as a central nanoregulator of transport between the cytosol and the nucleus. NPCs consist of ∼30 proteins, termed nucleoporins. About one-third of nucleoporins harbor natively unstructured, intrinsically disordered phenylalanine-glycine strings (FG-Nups), which engage in transport selectivity. Because the barriers insert deeply in the NPC, they are nearly inaccessible. Several in vitro barrier models have been proposed; however, the dynamic FG-Nups protein molecules themselves are imperceptible in vivo. We show here that high-speed atomic force microscopy (HS-AFM) can be used to directly visualize nanotopographical changes of the nuclear pore inner channel in colorectal cancer (CRC) cells. Furthermore, using MLN8237/alisertib, an apoptotic and autophagic inducer currently being tested in relapsed cancer clinical trials, we unveiled the functional loss of nucleoporins, particularly the deformation of the FG-Nups barrier, in dying cancer cells. We propose that the loss of this nanoscopic resilience is an irreversible dying code in cells. These findings not only illuminate the potential application of HS-AFM as an intracellular nanoendoscopy but also might aid in the design of future nuclear targeted nanodrug delivery tailored to the individual patient.

Expression of CDCA3 Is a Prognostic Biomarker and Potential Therapeutic Target in Non-Small Cell Lung Cancer

INTRODUCTION

NSCLC is the leading cause for cancer-related deaths worldwide. New therapeutic targets are needed, as development of resistance to current treatment, such as platinum-based chemotherapy, is inevitable. The purpose of this study was to determine the functional relevance and therapeutic potential of cell division cycle associated 3 protein (CDCA3) in NSCLC.

METHODS

The expression of CDCA3 in squamous and nonsquamous NSCLC was investigated by using bioinformatics, Western blot analysis of matched tumor and normal tissue, and immunohistochemistry of a tissue microarray. The function of CDCA3 in NSCLC was determined by using several in vitro assays with small interfering RNA depleting CDCA3 in a panel of three immortalized human bronchial epithelial cell (HBEC) lines and seven NSCLC cell lines.

RESULTS

In this study, cell division cycle associated 3 gene (CDCA3) transcripts were identified as highly increased in NSCLC versus in nonmalignant tissue, with high levels of CDCA3 being associated with poor patient prognosis. CDCA3 protein was also increased in NSCLC tissue and expression was limited to tumor cells. CDCA3 expression was similarly increased in a panel of NSCLC cell lines compared with in three HBEC lines. Although depletion of CDCA3 in the HBEC lines did not affect cellular proliferation, depletion of CDCA3 expression markedly reduced the proliferation of all NSCLC cell lines. CDCA3 depletion caused a defective G2/M-phase cell cycle progression, upregulation of p21 independent of p53, and induction of cellular senescence.

CONCLUSIONS

Our findings highlight CDCA3 as a prognostic factor and potential novel therapeutic target in NSCLC through inhibition of tumor growth and promotion of tumor senescence.

Genomics of Hairy Cell Leukemia

Hairy cell leukemia (HCL) is a chronic mature B-cell neoplasm with unique clinicopathologic features and an initial exquisite sensitivity to chemotherapy with purine analogs; however, the disease relapses, often repeatedly. The enigmatic pathogenesis of HCL was recently clarified by the discovery of its underlying genetic cause, the BRAF-V600E kinase-activating mutation, which is somatically and clonally present in almost all patients through the entire disease spectrum and clinical course. By aberrantly activating the RAF-MEK-ERK signaling pathway, BRAF-V600E shapes key biologic features of HCL, including its specific expression signature, hairy morphology, and antiapoptotic behavior. Accompanying mutations of the KLF2 transcription factor or the CDKN1B/p27 cell cycle inhibitor are recurrent in 16% of patients with HCL and likely cooperate with BRAF-V600E in HCL pathogenesis. Conversely, BRAF-V600E is absent in other B-cell neoplasms, including mimickers of HCL that require different treatments (eg, HCL-variant and splenic marginal zone lymphoma). Thus, testing for BRAF-V600E allows for a genetics-based differential diagnosis between HCL and HCL-like tumors, even noninvasively in routine blood samples. BRAF-V600E also represents a new therapeutic target. Patients' leukemic cells exposed ex vivo to BRAF inhibitors are spoiled of their HCL identity and then undergo apoptosis. In clinical trials of patients with HCL who have experienced multiple relapses after purine analogs or who are refractory to purine analogs, a short course of the oral BRAF inhibitor vemurafenib produced an almost 100% response rate, including complete remission rates of 35% to 42%, without myelotoxicity. To further improve on these results, it will be important to clarify the mechanisms of incomplete leukemic cell eradication by vemurafenib and to explore chemotherapy-free combinations of a BRAF inhibitor with other targeted agents (eg, a MEK inhibitor and/or an anti-CD20 monoclonal antibody).

Immunosenescence and hurdles in the clinical management of older HIV-patients

People living with HIV (PLWH) who are treated with effective highly active antiretroviral therapy (HAART) have a similar life expectancy to the general population. Moreover, an increasing proportion of new HIV diagnoses are made in people older than 50 y. The number of older HIV-infected patients is thus constantly growing and it is expected that by 2030 around 70% of PLWH will be more than 50 y old. On the other hand, HIV infection itself is responsible for accelerated immunosenescence, a progressive decline of immune system function in both the adaptive and the innate arm, which impairs the ability of an individual to respond to infections and to give rise to long-term immunity; furthermore, older patients tend to have a worse immunological response to HAART. In this review we focus on the pathogenesis of HIV-induced immunosenescence and on the clinical management of older HIV-infected patients.

BRG1 and BRM loss selectively impacts RB and P53, respectively: BRG1 and BRM have differential functions in vivo

The SWI/SNF complex is an important regulator of gene expression that functions by interacting with a diverse array of cellular proteins. The catalytic subunits of SWI/SNF, BRG1 and BRM, are frequently lost alone or concomitantly in a range of different cancer types. This loss abrogates SWI/SNF complex function as well as the functions of proteins that are required for SWI/SNF function, such as RB1 and TP53. Yet while both proteins are known to be dependent on SWI/SNF, we found that BRG1, but not BRM, is functionally linked to RB1, such that loss of BRG1 can directly or indirectly inactivate the RB1 pathway. This newly discovered dependence of RB1 on BRG1 is important because it explains why BRG1 loss can blunt the growth-inhibitory effect of tyrosine kinase inhibitors (TKIs). We also observed that selection for Trp53 mutations occurred in Brm-positive tumors but did not occur in Brm-negative tumors. Hence, these data indicate that, during cancer development, Trp53 is functionally dependent on Brm but not Brg1. Our findings show for the first time the key differences in Brm- and Brg1-specific SWI/SNF complexes and help explain why concomitant loss of Brg1 and Brm frequently occurs in cancer, as well as how their loss impacts cancer development.

Δ40p53α suppresses tumor cell proliferation and induces cellular senescence in hepatocellular carcinoma cells

Splice variants of certain genes impact on genetic biodiversity in mammals. The tumor suppressor TP53 gene (encoding p53) plays an important role in the regulation of tumorigenesis in hepatocellular carcinoma (HCC). Δ40p53α is a naturally occurring p53 isoform that lacks the N-terminal transactivation domain, yet little is known about the role of Δ40p53α in the development of HCC. Here, we first report on the role of Δ40p53α in HCC cell lines. In the TP53^+/Δ40 cell clones, clonogenic activity and cell survival dramatically decreased, whereas the percentage of senescence-associated β-galactosidase (SA-β-gal)-positive cells and p21 (also known as WAF1, CIP1 and CDKN1A) expression significantly increased. These observations were clearly attenuated in the TP53^+/Δ40 cell clones after Δ40p53α knockdown. In addition, exogenous Δ40p53 expression significantly suppressed cell growth in HCC cells with wild-type TP53, and in those that were mutant or null for TP53. Notably, Δ40p53α-induced tumor suppressor activity was markedly attenuated in cells expressing the hot-spot mutant Δ40p53α-R175H, which lacks the transcription factor activity of p53. Moreover, Δ40p53α expression was associated with increased full-length p53 protein expression. These findings enhance the understanding of the molecular pathogenesis of HCC and show that Δ40p53α acts as an important tumor suppressor in HCC cells.

Summary: Δ40p53 exerts tumor suppressor activity that is associated with upregulation of p53-target gene expression and induces senescence in hepatocellular carcinoma cell lines.

SENP1 Is a Crucial Regulator for Cell Senescence through DeSUMOylation of Bmi1

Cell senescence can limit proliferative potential and prevent tumorigenesis. Bmi1 is a key regulator in cell senescence by suppressing the Ink4a/Arf locus. However, how to regulate Bmi1 activity in cell senescence is largely unknown. Here, we show that SENP1 plays an important role in cell senescence by regulating Bmi1 SUMOylation. Senp1^−/− primary MEF cells show resistance to cell senescence induced by passaging or other senescence inducing signals. SENP1 deficiency also reduces oncogene H-Ras^V12-induced senescence, and enhances H-Ras^V12-induced cell transformation. We further show that in Senp1^−/− MEFs the expression of p19^Arf, an important regulator in p53/p21-mediated cell senescence, is markedly reduced. Meanwhile, we demonstrate that SENP1 can specifically de-SUMOylate Bmi1 and thereby decreases the occupancy of Bmi1 on p19^Arf promoter leading to decrease of H2AK119 mono-ubiquitination and up-expression of p19^Arf. These data reveal a crucial role of SENP1 in regulation of cell senescence as well as cell transformation.

Soluble egg antigens of Schistosoma japonicum induce senescence in activated hepatic stellate cells by activation of the STAT3/p53/p21 pathway

Liver fibrosis is characterized by the activation of hepatic stellate cells (HSCs). Recent findings suggest that senescence of activated HSCs might limit the development of liver fibrosis. Based on previously observed anti-fibrotic effects of soluble egg antigens from Schistosoma japonicum in vitro, we hypothesized that SEA might play a crucial role in alleviating liver fibrosis through promoting senescence of activated HSCs. We show here that SEA inhibited expression of α-SMA and pro-collagen I and promoted senescence of activated HSCs in vitro. In addition, SEA induced an increased expression of P-p53 and p21. Knockdown of p53 inhibited the expression of p21 and failed to induce senescence of activated-HSCs. Phosphorylated STAT3 was elevated upon SEA stimulation, while loss of STAT3 decreased the level of p53 and senescence of HSCs. Results from immunoprecipitation analysis demonstrated that SOCS3 might be involved in the SEA-induced senescence in HSCs through its interaction with p53. This study demonstrates the potential capacity of SEA in restricting liver fibrosis through promoting senescence in HSCs. Furthermore, a novel STAT3-p53-p21 pathway might participate in the observed SEA-mediated senescence of HSCs. Our results suggest that SEA might carry potential therapeutic effects of restraining liver fibrosis through promoting senescence.

DNA Damage and Repair Biomarkers in Cervical Cancer Patients Treated with Neoadjuvant Chemotherapy: An Exploratory Analysis

Cervical cancer cells commonly harbour a defective G₁/S checkpoint owing to the interaction of viral oncoproteins with p53 and retinoblastoma protein. The activation of the G₂/M checkpoint may thus become essential for protecting cancer cells from genotoxic insults, such as chemotherapy. In 52 cervical cancer patients treated with neoadjuvant chemotherapy, we investigated whether the levels of phosphorylated Wee1 (pWee1), a key G₂/M checkpoint kinase, and γ-H2AX, a marker of DNA double-strand breaks, discriminated between patients with a pathological complete response (pCR) and those with residual disease. We also tested the association between pWee1 and phosphorylated Chk1 (pChk1), a kinase acting upstream Wee1 in the G₂/M checkpoint pathway. pWee1, γ-H2AX and pChk1 were retrospectively assessed in diagnostic biopsies by immunohistochemistry. The degrees of pWee1 and pChk1 expression were defined using three different classification methods, i.e., staining intensity, Allred score, and a multiplicative score. γ-H2AX was analyzed both as continuous and categorical variable. Irrespective of the classification used, elevated levels of pWee1 and γ-H2AX were significantly associated with a lower rate of pCR. In univariate and multivariate analyses, pWee1 and γ-H2AX were both associated with reduced pCR. Internal validation conducted through a re-sampling without replacement procedure confirmed the robustness of the multivariate model. Finally, we found a significant association between pWee1 and pChk1. The message conveyed by the present analysis is that biomarkers of DNA damage and repair may predict the efficacy of neoadjuvant chemotherapy in cervical cancer. Further studies are warranted to prospectively validate these encouraging findings.

p53 Restoration in Induction and Maintenance of Senescence: Differential Effects in Premalignant and Malignant Tumor Cells

The restoration of p53 has been suggested as a therapeutic approach in tumors. However, the timing of p53 restoration in relation to its efficacy during tumor progression still is unclear. We now show that the restoration of p53 in murine premalignant proliferating pineal lesions resulted in cellular senescence, while p53 restoration in invasive pineal tumors did not. The effectiveness of p53 restoration was not dependent on p19(Arf) expression but showed an inverse correlation with Mdm2 expression. In tumor cells, p53 restoration became effective when paired with either DNA-damaging therapy or with nutlin, an inhibitor of p53-Mdm2 interaction. Interestingly, the inactivation of p53 after senescence resulted in reentry into the cell cycle and rapid tumor progression. The evaluation of a panel of human supratentorial primitive neuroectodermal tumors (sPNET) showed low activity of the p53 pathway. Together, these data suggest that the restoration of the p53 pathway has different effects in premalignant versus invasive pineal tumors, and that p53 activation needs to be continually sustained, as reversion from senescence occurs rapidly with aggressive tumor growth when p53 is lost again. Finally, p53 restoration approaches may be worth exploring in sPNET, where the p53 gene is intact but the pathway is inactive in the majority of examined tumors.