Autophagic activity dictates the cellular response to oncogenic RAS

Recent Anti-KRASG12D Therapies: A "Possible Impossibility" for Pancreatic Ductal Adenocarcinoma

Background: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer, able to thrive in a challenging tumor microenvironment. Current standard therapies, including surgery, radiation, chemotherapy, and chemoradiation, have shown a dismal survival prognosis, resulting in less than a year of life in the metastatic setting. Methods: The pressing need to find better therapeutic methods brought about the discovery of new targeted therapies against the infamous KRAS mutations, the major oncological drivers of PDAC. Results: The most common KRAS mutation is KRASG12D, which causes a conformational change in the protein that constitutively activates downstream signaling pathways driving cancer hallmarks. Novel anti-KRASG12D therapies have been developed for solid-organ tumors, including small compounds, pan-RAS inhibitors, protease inhibitors, chimeric T cell receptors, and therapeutic vaccines. Conclusions: This comprehensive review summarizes current knowledge on the biology of KRAS-driven PDAC, the latest therapeutic options that have been experimentally validated, and developments in ongoing clinical trials.

γ-Mangosteen, an autophagy enhancer, prevents skin-aging via activating KEAP1/NRF2 signaling and downregulating MAPKs/AP-1/NF-κB-mediated MMPs

BACKGROUND

Mangosteens, a naturally occurring xanthones, found abundantly in mangosteen fruits. The anti-skin aging potential of γ-mangosteen (GM) remains unexplored; therefore, we investigated the UVB-induced anti-skin aging of GM via activation of autophagy.

HYPOTHESIS

We hypothesized that GM exerts antioxidant and anti-aging capabilities both in vitro and in vivo through activation of autophagy as well as control of KEAP1/NRF2 signaling and MAPKs/AP-1/NF-κB-mediated MMPs pathways.

METHODS

The anti-skin aging effects of GM were studied using HDF cells and a mice model. Various assays, such as DPPH, ABTS, CUPRAC, FRAP, and ROS generation, assessed antioxidant activities. Kits measured antioxidant enzymes, SA-β-gal staining, collagen, MDA content, si-RNA experiments, and promoter assays. Western blotting evaluated protein levels of c-Jun, c-Fos, p-IκBα/β, p-NF-κB, MAPK, MMPs, collagenase, elastin, KEAP1, NRF2, HO-1, and autophagy-related proteins.

RESULTS

GM exhibited strong antioxidant, collagenase and elastase enzyme inhibition activity surpassing α- and β-mangosteen. GM competitively inhibited elastase with a Ki value of 29.04 µM. GM orchestrated the KEAP1-NRF2 pathway, enhancing HO-1 expression, and suppressed UVB-induced ROS in HDF cells. NRF2 knockdown compromised GM's antioxidant efficacy, leading to uncontrolled ROS post-UVB. GM bolstered endogenous antioxidants, curbing lipid peroxidation in UVB-exposed HDF cells and BALB/c mice. GM effectively halted UVB-induced cell senescence, and reduced MMP-1/-9, while elevated TIMP-1 levels, augmented COL1A1, ELN, and HAS-2 expression in vitro and in vivo. Additionally, it suppressed UVB-induced MAPKs, AP-1, NF-κB phosphorylation. Pharmacological inhibitors synergistically enhanced GM's anti-skin aging potential. Moreover, GM inhibited UVB-induced mTOR activation, upregulated LC3-II, Atg5, Beclin 1, and reduced p62 in both UVB induced HDF cells and BALB/c mice, while blocking of autophagy successfully halt the GM effects against the UVB-induced increase of cell senescence, degradation of collagen through upregulation of MMP-1, underscoring GM's substantial anti-skin aging impact via autophagy induction in vitro and in vivo.

CONCLUSION

Together, GM has potent antioxidant and anti-skin aging ingredients that can be used to formulate skin care products for both the nutraceutical and cosmeceutical industries.

Enhancing ASPP2 promotes acute liver injury via an inflammatory immunoregulatory mechanism

Background

Acute liver injury (ALI), which is a type of inflammation-mediated hepatocellular injury, is a clinical syndrome that results from hepatocellular apoptosis and hemorrhagic necrosis. Apoptosis stimulating protein of p53-2 (ASPP2) is a proapoptotic member of the p53 binding protein family. However, the role of ASPP2 in the pathogenesis of ALI and its regulatory mechanisms remain unclear.

Methods

The expression of ASPP2 were compared between liver biopsies derived from patients with CHB, patients with ALI, and normal controls. Acute liver injury was modelled in mice by administration of D-GalN/LPS. Liver injury was demonstrated by serum transaminases and histological assessment of liver sections. ASPP2-knockdown mice (ASPP2+/-) were used to determine its role in acute liver injury. Mouse bone marrow macrophages (BMMs) were isolated from wildtype and ASPP2+/- mice and stimulated with LPS, and the supernatant was collected to incubate with the primary hepatocytes. Quantitative real-time PCR and western blot were used to analyze the expression level of target.

Results

The expression of ASPP2 was significantly upregulated in the liver tissue of ALI patients and acute liver injury mice. ASPP2+/- mice significantly relieved liver injury through reducing liver inflammation and decreasing hepatocyte apoptosis. Moreover, the conditioned medium (CM) of ASPP2+/- bone marrow-derived macrophages (BMMs) protected hepatocytes against apoptosis. Mechanistically, we revealed that ASPP2 deficiency in BMMs specifically upregulated IL-6 through autophagy activation, which decreased the level of TNF-α to reduce hepatocytes apoptosis. Furthermore, up-regulation of ASPP2 sensitizes hepatocytes to TNF-α-induced apoptosis.

Conclusion

Our novel findings show the critical role of ASPP2 in inflammatory immunoregulatory mechanism of ALI and provide a rationale to target ASPP2 as a refined therapeutic strategy to ameliorate acute liver injury.

Exosome GLUT1 derived from hepatocyte identifies the risk of non-alcoholic steatohepatitis and fibrosis

BACKGROUND AND AIMS

It is particularly important to identify the progression of non-alcoholic fatty liver disease (NAFLD) for prognosis evaluation and treatment guidance. The aim of this study was to explore the clinic use of exosomal protein-based detection as a valuable non-invasive diagnostic method for NAFLD.

METHODS

Exosomes were extracted from plasma of patients with NAFLD using Optima XPN-100 ultrafast centrifuge. The patients were recruited from outpatients and inpatients of Beijing Youan Hospital Affiliated to Capital Medical University. The exosomes were stained with fluorescent-labeled antibody and determined by ImageStream® X MKII imaging flow cytometry. Generalized linear logistic regression model was used to evaluate the diagnostic value of hepatogenic exosomes in NAFLD and liver fibrosis.

RESULTS

The percentage of hepatogenic exosomes glucose transporter 1 (GLUT1) in patients with non-alcoholic steatohepatitis (NASH) was significantly higher than that in patients with non-alcoholic fatty liver (NAFL). According to liver biopsy, we found that the percentage of hepatogenic exosomes GLUT1 in patients with advanced NASH (F2-4) was significantly higher than that in patients with early NASH (F0-1), and the same trend was observed in exosomes with CD63 and ALB. Compared with other clinical fibrosis scoring criteria (FIB-4, NFS, etc.), the diagnostic performance of hepatogenic exosomes GLUT1 was the highest and the area under the receiver-operating curves (AUROC) was 0.85 (95% CI 0.77-0.93). Furthermore, the AUROC of hepatogenic exosomes GLUT1 combined with fibrosis scoring was as high as 0.86-0.91.

CONCLUSION

Hepatogenic exosome GLUT1 can be a molecular biomarker for early warning of NAFLD to distinguish the NAFL and NASH, and it also can be used as a novel non-invasive diagnostic biomarker for the staging liver fibrosis in NAFLD.

Interaction between Autophagy and Senescence in Pancreatic Beta Cells

Aging leads to an increase in cellular stress due to the fragility of the organism and the inability to cope with it. In this setting, there is a higher chance of developing different cardiometabolic diseases like diabetes. Cellular senescence and autophagy, both hallmarks of aging and stress-coping mechanisms, have gained increased attention for their role in the pathophysiology of diabetes. Studies show that impairing senescence dampens and even prevents diabetes while the role of autophagy is more contradictory, implying a context- and disease-stage-dependent effect. Reports show conflicting data about the effect of autophagy on senescence while the knowledge about this interaction in beta cells remains scarce. Elucidating this interaction between autophagy and senescence in pancreatic beta cells will lead to an identification of their respective roles and the extent of the effect each mechanism has on beta cells and open new horizons for developing novel therapeutic agents. To help illuminate this relationship we will review the latest findings of cellular senescence and autophagy with a special emphasis on pancreatic beta cells and diabetes.

ASPP2 suppresses tumour growth and stemness characteristics in HCC by inhibiting Warburg effect via WNT/β-catenin/HK2 axis

Abnormal energy metabolism is one of the characteristics of tumours. In the last few years, more and more attention is being paid to the role and regulation of tumour aerobic glycolysis. Cancer cells display enhanced aerobic glycolysis, also known as the Warburg effect, whereby tumour cells absorb glucose to produce a large amount of lactic acid and energy under aerobic conditions to favour tumour proliferation and metastasis. In this study, we report that the haploinsufficient tumour suppressor ASPP2, can inhibit HCC growth and stemness characteristics by regulating the Warburg effect through the WNT/β-catenin pathway. we performed glucose uptake, lactate production, pyruvate production, ECAR and OCR assays to verify ASPP2 can inhibit glycolysis in HCC cells. The expression of ASPP2 and HK2 was significantly inversely correlated in 80 HCC tissues. Our study reveals downregulation of ASPP2 can promote the aerobic glycolysis metabolism pathway, increasing HCC proliferation, glycolysis metabolism, stemness and drug resistance. This ASPP2-induced inhibition of glycolysis metabolism depends on the WNT/β-catenin pathway. ASPP2-regulated Warburg effect is associated with tumour progression and provides prognostic value. and suggest that may be promising as a new therapeutic strategy in HCC.

Targeting and regulation of autophagy in hepatocellular carcinoma: revisiting the molecular interactions and mechanisms for new therapy approaches

Autophagy is an evolutionarily conserved process that plays a role in regulating homeostasis under physiological conditions. However, dysregulation of autophagy is observed in the development of human diseases, especially cancer. Autophagy has reciprocal functions in cancer and may be responsible for either survival or death. Hepatocellular carcinoma (HCC) is one of the most lethal and common malignancies of the liver, and smoking, infection, and alcohol consumption can lead to its development. Genetic mutations and alterations in molecular processes can exacerbate the progression of HCC. The function of autophagy in HCC is controversial and may be both tumor suppressive and tumor promoting. Activation of autophagy may affect apoptosis in HCC and is a regulator of proliferation and glucose metabolism. Induction of autophagy may promote tumor metastasis via induction of EMT. In addition, autophagy is a regulator of stem cell formation in HCC, and pro-survival autophagy leads to cancer cell resistance to chemotherapy and radiotherapy. Targeting autophagy impairs growth and metastasis in HCC and improves tumor cell response to therapy. Of note, a large number of signaling pathways such as STAT3, Wnt, miRNAs, lncRNAs, and circRNAs regulate autophagy in HCC. Moreover, regulation of autophagy (induction or inhibition) by antitumor agents could be suggested for effective treatment of HCC. In this paper, we comprehensively review the role and mechanisms of autophagy in HCC and discuss the potential benefit of targeting this process in the treatment of the cancer. Video Abstract.

Autophagy at the intersection of aging, senescence, and cancer

Autophagy is an evolutionarily conserved cellular process in which macromolecules undergo lysosomal degradation. It fulfills essential roles in quality controlling cellular constituents and in energy homeostasis. Basal autophagy is also widely accepted to provide a protective role in aging and aging-related disorders, and its decline with age might precipitate the onset of a variety of diseases. In this review, we discuss the role of basal autophagy in maintaining homeostasis, in part through the maintenance of stem cell populations and the prevention of cellular senescence. We also consider how stress-induced senescence, for example, during oncogene activation and in premalignant disease, might rely on autophagy, and the possibility that the age-associated decline in autophagy might promote tumour development through a variety of mechanisms. Ultimately, evidence suggests that autophagy is required for malignant cancer progression in a number of settings. Thus, autophagy appears to be tumour-suppressive during the early stages of tumorigenesis and tumour-promoting at later stages.

TP53BP2: Roles in suppressing tumorigenesis and therapeutic opportunities

Malignant tumor is still a major problem worldwide. During tumorigenesis or tumor development, tumor suppressor p53-binding protein 2 (TP53BP2), also known as apoptosis stimulating protein 2 of p53 (ASPP2), plays a critical role in p53 dependent and independent manner. Expression of TP53BP2 is highly correlated with the prognosis and survival rate of malignant tumor patients. TP53BP2 can interact with p53, NF-κB p65, Bcl-2, HCV core protein, PP1, YAP, CagA, RAS, PAR3, and other proteins to regulate cell function. Moreover, TP53BP2 can also regulate the proliferation, apoptosis, autophagy, migration, EMT and drug resistance of tumor cells through downstream signaling pathways, such as NF-κB, RAS/MAPK, mevalonate, TGF-β1, PI3K/AKT, aPKC-ι/GLI1 and autophagy pathways. As a potential therapeutic target, TP53BP2 has been attracted more attention. We review the role of TP53BP2 in tumorigenesis or tumor development and the signal pathway involved in TP53BP2, which may provide more deep insight and strategies for tumor treatment.

Crucial Role of Oncogenic KRAS Mutations in Apoptosis and Autophagy Regulation: Therapeutic Implications

KRAS, one of the RAS protein family members, plays an important role in autophagy and apoptosis, through the regulation of several downstream effectors. In cancer cells, KRAS mutations confer the constitutive activation of this oncogene, stimulating cell proliferation, inducing autophagy, suppressing apoptosis, altering cell metabolism, changing cell motility and invasion and modulating the tumor microenvironment. In order to inhibit apoptosis, these oncogenic mutations were reported to upregulate anti-apoptotic proteins, including Bcl-xL and survivin, and to downregulate proteins related to apoptosis induction, including thymine-DNA glycosylase (TDG) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). In addition, KRAS mutations are known to induce autophagy in order to promote cell survival and tumor progression through MAPK and PI3K regulation. Thus, these mutations confer resistance to anti-cancer drug treatment and, consequently, result in poor prognosis. Several therapies have been developed in order to overcome KRAS-induced cell death resistance and the downstream signaling pathways blockade, especially by combining MAPK and PI3K inhibitors, which demonstrated promising results. Understanding the involvement of KRAS mutations in apoptosis and autophagy regulation, might bring new avenues to the discovery of therapeutic approaches for CRCs harboring KRAS mutations.

ASPP2 Coordinates ERS-Mediated Autophagy and Apoptosis Through mTORC1 Pathway in Hepatocyte Injury Induced by TNF-α

Background: Though ASPP2 plays an important role in regulating cell apoptosis and autophagy in case of liver injury, there remains a lack of clarity on the molecular mechanism of ASPP2 regulating autophagy and apoptosis.

Methods: A hepatocyte injury model was constructed using HL7702 cell line and TNF-α. The cells were treated by ASPP2 overexpression adenovirus or short hairpin RNA lentivirus and endoplasmic reticulum stress (ERS) or the mammalian target of rapamycin (mTOR) inhibitor or agonist, respectively. The autophagy was detected by means of western blot and Green fluorescent protein-labeled- Microtubule-associated protein light chain 3 (GFP-LC3) plasmid transfection, while the apoptosis was detected through western blot, flow cytometry and TUNEL assay. Besides, the proteins related to ERS and mTOR were detected by western blot.

Results: The low level of ASPP2 expression was accompanied by high-level autophagy and low-level apoptosis and vice versa in case of hepatocyte injury induce by TNF-α. By upregulating the proteins related to mTORC1 and ERS, ASPP2 induced apoptosis but inhibited autophagy. However, the effect of ASPP2 on autophagy and apoptosis can be reversed by the use of mTORC1 and ERS interfering agent, which indicates that ASPP2 regulated autophagy and apoptosis through mTORC1and ERS pathway. ERS treatment made no difference to the expression of ASPP2 and mTOR-related proteins, which suggests the possibility that the regulation of ERS on apoptosis and autophagy could occur in the downstream of ASPP2 and mTOR.

Conclusion: ASPP2 could inhibit autophagy and induce apoptosis through mTORC1-ERS pathway in case of the hepatocyte injury induce by TNF-α. The role of ASPP2-mTORC1-ERS axis was verified in hepatocyte injury, which suggests the possibility that ASPP2 is an important regulatory molecule for the survival and death of hepatocyte.

Cellular Senescence: Molecular Targets, Biomarkers, and Senolytic Drugs

Cellular senescence is defined as irreversible cell cycle arrest caused by various processes that render viable cells non-functional, hampering normal tissue homeostasis. It has many endogenous and exogenous inducers, and is closely connected with age, age-related pathologies, DNA damage, degenerative disorders, tumor suppression and activation, wound healing, and tissue repair. However, the literature is replete with contradictory findings concerning its triggering mechanisms, specific biomarkers, and detection protocols. This may be partly due to the wide range of cellular and in vivo animal or human models of accelerated aging that have been used to study senescence and test senolytic drugs. This review summarizes recent findings concerning senescence, presents some widely used cellular and animal senescence models, and briefly describes the best-known senolytic agents.

4,4'-Dimethoxychalcone protects the skin from AAPH-induced senescence and UVB-induced photoaging by activating autophagy

Aging can lead to the occurrence of many degenerative diseases, and the most intuitive consequences are mainly manifested on the skin, which is affected by both endogenous and exogenous aging factors and can be used as an ideal model organ for studying aging. 4,4'-Dimethoxychalcone (DMC), a natural flavonoid compound from Angelica sinensis, has been proven to prolong the lifespan of multiple species. However, it is not clear whether it has the effect of delaying skin aging. This study aimed to establish a skin senescent cell model induced by oxidative stress, and further, to analyze the inhibitory effect of DMC on cellular senescence, and explore its molecular mechanisms. We found that treatment of HaCaT cells with 1 mM 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) for 48 h showed significant senescent characteristics, which could be effectively alleviated by pretreatment with the antioxidant N-acetyl-L-cysteine (NAC). DMC significantly inhibited AAPH-induced senescence, and further mechanism studies showed that the activation of autophagy which depended on the phosphorylation of ULK1 at Ser555 was necessary for DMC to alleviate senescence of HaCaT cells. In addition, the mitogen-activated protein kinase (MAPK) signal pathway was also involved in the regulation of autophagy induced by DMC. These results were also validated in UVB-induced photoaging mice. In conclusion, we successfully establish a skin senescent cell model and prove that DMC can be used as a potential therapeutic agent to intervene in skin aging.

Role and regulation of autophagy in cancer

Autophagy is an intracellular self-degradative mechanism which responds to cellular conditions like stress or starvation and plays a key role in regulating cell metabolism, energy homeostasis, starvation adaptation, development and cell death. Numerous studies have stipulated the participation of autophagy in cancer, but the role of autophagy either as tumor suppressor or tumor promoter is not clearly understood. However, mechanisms by which autophagy promotes cancer involves a diverse range of modifications of autophagy associated proteins such as ATGs, Beclin-1, mTOR, p53, KRAS etc. and autophagy pathways like mTOR, PI3K, MAPK, EGFR, HIF and NFκB. Furthermore, several researches have highlighted a context-dependent, cell type and stage-dependent regulation of autophagy in cancer. Alongside this, the interaction between tumor cells and their microenvironment including hypoxia has a great potential in modulating autophagy response in favour to substantiate cancer cell metabolism, self-proliferation and metastasis. In this review article, we highlight the mechanism of autophagy and their contribution to cancer cell proliferation and development. In addition, we discuss about tumor microenvironment interaction and their consequence on selective autophagy pathways and the involvement of autophagy in various tumor types and their therapeutic interventions concentrated on exploiting autophagy as a potential target to improve cancer therapy.

Bamboo Leaf Flavonoids Suppress Oxidative Stress-Induced Senescence of HaCaT Cells and UVB-Induced Photoaging of Mice through p38 MAPK and Autophagy Signaling

With the global escalation of the aging process, the research on aging mechanisms and anti-aging strategies has become a hot spot. As the most external organ of the human body, skin can be used as an ideal organ for the study of endogenous and exogenous aging. Bamboo leaf flavonoids (BLF) possess a variety of biological effects such as antioxidant, anti-bacterial, anti-inflammatory, lipid-lowering, anti-radiation, and anti-aging. However, it is still unclear whether they can delay skin aging. This study aimed to analyze the inhibitory effect of BLF on skin aging and explore their molecular mechanisms. We found that 10–40 μg/mL BLF significantly inhibited the senescence of HaCaT cells induced by AAPH, which might be related to their antioxidant and anti-inflammatory abilities. Further mechanism studies showed that mitogen-activated protein kinase (MAPK), especially the p38 MAPK pathway, was the key to BLF to alleviate the senescence of HaCaT cells. In addition, autophagy was also involved in the anti-senescence effect of BLF. The results were also verified in UVB-induced photoaging mice. Therefore, BLF can be used as a potential therapeutic agent to intervene skin aging in vitro and in vivo.

Disrupting the MYC-TFEB Circuit Impairs Amino Acid Homeostasis and Provokes Metabolic Anergy

MYC family oncoproteins are regulators of metabolic reprogramming that sustains cancer cell anabolism. Normal cells adapt to nutrient-limiting conditions by activating autophagy, which is required for amino acid (AA) homeostasis. Here we report that the autophagy pathway is suppressed by Myc in normal B cells, in premalignant and neoplastic B cells of Eμ-Myc transgenic mice, and in human MYC-driven Burkitt lymphoma. Myc suppresses autophagy by antagonizing the expression and function of transcription factor EB (TFEB), a master regulator of autophagy. Mechanisms that sustained AA pools in MYC-expressing B cells include coordinated induction of the proteasome and increases in AA transport. Reactivation of the autophagy-lysosomal pathway by TFEB disabled the malignant state by disrupting mitochondrial functions, proteasome activity, amino acid transport, and amino acid and nucleotide metabolism, leading to metabolic anergy, growth arrest and apoptosis. This phenotype provides therapeutic opportunities to disable MYC-driven malignancies, including AA restriction and treatment with proteasome inhibitors.

Cell Survival and Cell Death at the Intersection of Autophagy and Apoptosis: Implications for Current and Future Cancer Therapeutics

Autophagy and apoptosis are functionally distinct mechanisms for cytoplasmic and cellular turnover. While these two pathways are distinct, they can also regulate each other, and central components of the apoptosis or autophagy pathway regulate both processes directly. Furthermore, several upstream stress-inducing signaling pathways can influence both autophagy and apoptosis. The crosstalk between autophagy and apoptosis has an integral role in pathological processes, including those related to cancer, homeostasis, and aging. Apoptosis is a form of programmed cell death, tightly regulated by various cellular and biochemical mechanisms, some of which have been the focus of drug discovery efforts targeting cancer therapeutics. Autophagy is a cellular degradation pathway whereby cells recycle macromolecules and organelles to generate energy when subjected to stress. Autophagy can act as either a prodeath or a prosurvival process and is both tissue and microenvironment specific. In this review we describe five groups of proteins that are integral to the apoptosis pathway and discuss their role in regulating autophagy. We highlight several apoptosis-inducing small molecules and biologics that have been developed and advanced into the clinic and discuss their effects on autophagy. For the most part, these apoptosis-inducing compounds appear to elevate autophagy activity. Under certain circumstances autophagy demonstrates cytoprotective functions and is overactivated in response to chemo- or radiotherapy which can lead to drug resistance, representing a clinical obstacle for successful cancer treatment. Thus, targeting the autophagy pathway in combination with apoptosis-inducing compounds may be a promising strategy for cancer therapy.

Role of Senescence and Aging in SARS-CoV-2 Infection and COVID-19 Disease

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in a global pandemic associated with substantial morbidity and mortality worldwide, with particular risk for severe disease and mortality in the elderly population. SARS-CoV-2 infection is driven by a pathological hyperinflammatory response which results in a dysregulated immune response. Current advancements in aging research indicates that aging pathways have fundamental roles in dictating healthspan in addition to lifespan. Our review discusses the aging immune system and highlights that senescence and aging together, play a central role in COVID-19 pathogenesis. In our review, we primarily focus on the immune system response to SARS-CoV-2 infection, the interconnection between severe COVID-19, immunosenescence, aging, vaccination, and the emerging problem of Long-COVID. We hope to highlight the importance of identifying specific senescent endotypes (or "sendotypes"), which can used as determinants of COVID-19 severity and mortality. Indeed, identified sendotypes could be therapeutically exploited for therapeutic intervention. We highlight that senolytics, which eliminate senescent cells, can target aging-associated pathways and therefore are proving attractive as potential therapeutic options to alleviate symptoms, prevent severe infection, and reduce mortality burden in COVID-19 and thus ultimately enhance healthspan.

Brahma-related gene-1 promotes tubular senescence and renal fibrosis through Wnt/β-catenin/autophagy axis

Although accelerated cellular senescence is closely related to the progression of chronic kidney disease (CKD) and renal fibrosis, the underlying mechanisms remain largely unknown. Here, we reported that tubular aberrant expression of Brahma-related gene 1 (BRG1), an enzymatic subunit of the SWItch/Sucrose Non-Fermentable complex, is critically involved in tubular senescence and renal fibrosis. BRG1 was significantly up-regulated in the kidneys, predominantly in tubular epithelial cells, of both CKD patients and unilateral ureteral obstruction (UUO) mice. In vivo, shRNA-mediated knockdown of BRG1 significantly ameliorated renal fibrosis, improved tubular senescence, and inhibited UUO-induced activation of Wnt/β-catenin pathway. In mouse renal tubular epithelial cells (mTECs) and primary renal tubular cells, inhibition of BRG1 diminished transforming growth factor-β1 (TGF-β1)-induced cellular senescence and fibrotic responses. Correspondingly, ectopic expression of BRG1 in mTECs or normal kidneys increased p16INK4a, p19ARF, and p21 expression and senescence-associated β-galactosidase (SA-β-gal) activity, indicating accelerated tubular senescence. Additionally, BRG1-mediated pro-fibrotic responses were largely abolished by small interfering RNA (siRNA)-mediated p16INK4a silencing in vitro or continuous senolytic treatment with ABT-263 in vivo. Moreover, BRG1 activated the Wnt/β-catenin pathway, which further inhibited autophagy. Pharmacologic inhibition of the Wnt/β-catenin pathway (ICG-001) or rapamycin (RAPA)-mediated activation of autophagy effectively blocked BRG1-induced tubular senescence and fibrotic responses, while bafilomycin A1 (Baf A1)-mediated inhibition of autophagy abolished the effects of ICG-001. Further, BRG1 altered the secretome of senescent tubular cells, which promoted proliferation and activation of fibroblasts. Taken together, our results indicate that BRG1 induces tubular senescence by inhibiting autophagy via the Wnt/β-catenin pathway, which ultimately contributes to the development of renal fibrosis.

ASPP2 inhibits hepatitis B virus replication by preventing nucleus translocation of HSF1 and attenuating the transactivation of ATG7

Hepatitis B virus (HBV) is a kind of virus with the capability to induce autophagy, thereby facilitating its replication. Reducing hepatocyte autophagy is proved to be a useful way to inhibit HBV replication. Herein, we reported that p53-binding protein 2 (apoptosis-stimulating protein of p53-2, ASPP2) could attenuate HBV-induced hepatocyte autophagy in a p53-independent manner. Mechanistically, overexpressed ASPP2 binds to HSF1 in cytoplasm of HBV-infected cells, which prevents the translocation of HSF1 to nuclei, thereby inhibiting the transactivation of Atg7. By regulating the transcription of Atg7, ASPP2 reduces hepatocyte autophagy, thereby inhibiting HBV replication. Therefore, ASPP2 is a key regulator of cell autophagy, and overexpression of ASPP2 could be a novel method to inhibit HBV replication in hepatocytes.

Molecular regulation of autophagy in a pro-inflammatory tumour microenvironment: New insight into the role of serum amyloid A

Chronic inflammation, systemic or local, plays a vital role in tumour progression and metastasis. Dysregulation of key physiological processes such as autophagy elicit unfavourable immune responses to induce chronic inflammation. Cytokines, growth factors and acute phase proteins present in the tumour microenvironment regulate inflammatory responses and alter crosstalk between various signalling pathways involved in the progression of cancer. Serum amyloid A (SAA) is a key acute phase protein secreted by the liver during the acute phase response (APR) following infection or injury. However, cancer and cancer-associated cells produce SAA, which when present in high levels in the tumour microenvironment contributes to cancer initiation, progression and metastasis. SAA can activate several signalling pathways such as the PI3K and MAPK pathways, which are also known modulators of the intracellular degradation process, autophagy. Autophagy can be regarded as having a double edged sword effect in cancer. Its dysregulation can induce malignant transformation through metabolic stress which manifests as oxidative stress, endoplasmic reticulum (ER) stress and DNA damage. On the other hand, autophagy can promote cancer survival during metabolic stress, hypoxia and senescence. Autophagy has been utilised to promote the efficiency of chemotherapeutic agents and can either be inhibited or induced to improve treatment outcomes. This review aims to address the known mechanisms that regulate autophagy as well as illustrating the role of SAA in modulating these pathways and its clinical implications for cancer therapy.

Autophagy displays divergent roles during intermittent amino acid starvation and toxic stress-induced senescence in cultured skeletal muscle cells

Due to the ever-expanding functions attributed to autophagy, there is widespread interest in understanding its contribution to human physiology; however, its specific cellular role as a stress-response mechanism is still poorly defined. To investigate autophagy's role in this regard, we repeatedly subjected cultured mouse myoblasts to two stresses with diverse impacts on autophagic flux: amino acid and serum withdrawal (Hank's balanced salt solution [HBSS]), which robustly induces autophagy, or low-level toxic stress (staurosporine, STS). We found that intermittent STS (int-STS) administration caused cell cycle arrest, development of enlarged and misshapen cells/nuclei, increased senescence-associated heterochromatic foci and senescence-associated β-galactosidase activity, and prevented myogenic differentiation. These features were not observed in cells intermittently incubated in HBSS (int-HB). While int-STS cells displayed less DNA damage (phosphorylated H2A histone family, member X content) and caspase activity when administered cisplatin, int-HB cells were protected from STS-induced cell death. Interestingly, STS-induced senescence was attenuated in autophagy related 7-deficient cells. Therefore, while repeated nutrient withdrawal did not cause senescence, autophagy was required for senescence caused by toxic stress. These results illustrate the context-dependent effects of different stressors, potentially highlighting autophagy as a distinguishing factor.

Biomarkers, oxidative stress and autophagy in skin aging

Aging is a major cause of many degenerative diseases. The most intuitive consequence of aging is mainly manifested on the skin, resulting in cumulative changes in skin structure, function and appearance, such as increased wrinkles, laxity, elastosis, telangiectasia, and aberrant pigmentation of the skin. Unlike other organs of the human body, skin is not only inevitably affected by the intrinsic aging process, but also affected by various extrinsic environmental factors to accelerate aging, especially ultraviolet (UV) radiation. Skin aging is a highly complex and not fully understood process, and the lack of universal biomarkers for the definitive detection and evaluation of aging is also a major research challenge. Oxidative stress induced by the accumulation of reactive oxygen species (ROS) can lead to lipid, protein, nucleic acid and organelle damage, thus leading to the occurrence of cellular senescence, which is one of the core mechanisms mediating skin aging. Autophagy can maintain cellular homeostasis when faced with different stress conditions and is one of the survival mechanisms of cell resistance to intrinsic and extrinsic stress. Autophagy and aging have many features in common and may be associated with skin aging mediated by different factors. Here, we summarize the changes and biomarkers of skin aging, and discuss the effects of oxidative stress and autophagy on skin aging.

ASPP1 deficiency promotes epithelial-mesenchymal transition, invasion and metastasis in colorectal cancer

The apoptosis-stimulating protein of p53 (ASPP) family of proteins can regulate apoptosis by interacting with the p53 family and have been identified to play an important role in cancer progression. Previously, we have demonstrated that ASPP2 downregulation can promote invasion and migration by controlling β-catenin-dependent regulation of ZEB1, however, the role of ASPP1 in colorectal cancer (CRC) remains unclear. We analyzed data from The Cancer Genome Atlas (TCGA) and coupled this to in vitro experiments in CRC cell lines as well as to experimental pulmonary metastasis in vivo. Tissue microarrays of CRC patients with information of clinical-pathological parameters were also used to investigate the expression and function of ASPP1 in CRC. Here, we report that loss of ASPP1 is capable of enhancing migration and invasion in CRC, both in vivo and in vitro. We demonstrate that depletion of ASPP1 could activate expression of Snail2 via the NF-κB pathway and in turn, induce EMT; and this process is further exacerbated in RAS-mutated CRC. ASPP1 could be a prognostic factor in CRC, and the use of NF-κB inhibitors may provide new strategies for therapy against metastasis in ASPP1-depleted CRC patients.

Transcriptome analysis of genes expressed in the earthworm Eisenia fetida in response to cadmium exposure

Eisenia fetida earthworm is an ecotoxicologically important test species to monitor various pollutants. However, there is a little knowledge about the effects of cadmium (Cd) on earthworms at the transcriptional level. Firstly, we exposed E. fetida to soils supplemented with different concentrations (10, 30, 60 mg/kg soil) of Cd. Moreover, we depicted the characterization of gene expressions with E. fetida using high-throughput profiling of gene expression. In addition, a comparison of the gene expression profiles between each Cd treatment group and the control group suggested that differential expressional genes (DEGs) mainly enriched in enzyme activity, metabolism, oxidative stress, regeneration and apoptosis pathways. 8 DEGs from these pathways had been selected randomly to confirm the data of RNA-seq. Among these DEGs, six genes (metallothionein-2, phytochelatin synthase 1a, CuZn superoxide dismutase, sex determining region Y-box 2, sex determining region Y-box 4b, TP53-regulated inhibitor of apoptosis 1-like) up-regulated and 2 genes (beta-1,4-endoglucanase, apoptosis-stimulating of p53 protein 2-like) down-regulated in response to Cd exposure. The alteration of them indicated that earthworms could reduce the toxicity and bioavailability of Cd in polluted soil ecosystems through different pathways. This work lays an important foundation for linking earthworm transcriptional level with the ecological risk of Cd in soil ecosystem.

Overcoming Resistance to Therapies Targeting the MAPK Pathway in BRAF-Mutated Tumours

Overactivation of the mitogen-activated protein kinase (MAPK) pathway is an important driver of many human cancers. First line, FDA-approved therapies targeting MAPK signalling, which include BRAF and MEK inhibitors, have variable success across cancers, and a significant number of patients quickly develop resistance. In recent years, a number of preclinical studies have reported alternative methods of overcoming resistance, which include promoting apoptosis, modulating autophagy, and targeting mitochondrial metabolism. This review summarizes mechanisms of resistance to approved MAPK-targeted therapies in BRAF-mutated cancers and discusses novel preclinical approaches to overcoming resistance.

Variable DNA methylation of aging-related genes is associated with male COPD

Background

Chronic obstructive pulmonary disease (COPD) is a chronic lung inflammatory disease which has a close relationship with aging. Genome-wide analysis reveals that DNA methylation markers vary obviously with age. DNA methylation variations in peripheral blood have the potential to be biomarkers for COPD. However, the specific DNA methylation of aging-related genes in the peripheral blood of COPD patients remains largely unknown.

Methods

Firstly, 9 aging-related differentially expressed genes (DEGs) in COPD patients were screened out from the 25 aging-related genes profile through a comprehensive screening strategy. Secondly, qPCR and multiple targeted bisulfite enrichment sequencing (MethTarget) were used to detect the mRNA level and DNA methylation level of the 9 differentially expressed genes in the peripheral blood of 60 control subjects and 45 COPD patients. The candidate functional CpG sites were selected on the basis of the regulation ability of the target gene expression. Thirdly, the correlation was evaluated between the DNA methylation level of the key CpG sites and the clinical parameters of COPD patients, including forced expiratory volume in one second (FEV1), forced expiratory volume in one second as percentage of predicted volume (FEV1%), forced expiratory volume/ forced vital capacity (FEV/FVC), modified British medical research council (mMRC) score, acute exacerbation frequency and the situation of frequent of acute aggravation (CAT) score. Lastly, differentially methylated CpG sites unrelated to smoking were also determined in COPD patients.

Results

Of the 9 differentially expressed aging-related genes, the mRNA expression of 8 genes were detected to be significantly down-regulated in COPD group, compared with control group. Meanwhile, the methylated level of all aging-related genes was changed in COPD group containing 219 COPD-related CpG sites in total. Notably, 27 CpG sites of FOXO3 gene showed a lower False Discovery Rate (FDR) and higher methylation difference values. Also, some variable DNA methylation is associated with the severity of COPD. Additionally, of the 219 COPD-related CpG sites, 147 CpG sites were not related to smoking.

Conclusion

These results identified that the mRNA expression and DNA methylation level of aging-related genes were changed in male COPD patients, which provides a molecular link between aging and COPD. The identified CpG markers are associated with the severity of COPD and provide new insights into the prediction and identification of COPD.

ASPP2 inhibits tumor growth by repressing the mevalonate pathway in hepatocellular carcinoma

Cancer is, fundamentally, a disorder of cell growth and proliferation, which requires adequate supplies of energy and nutrients. In this study, we report that the haplo-insufficient tumor suppressor ASPP2, a p53 activator, negatively regulates the mevalonate pathway to mediate its inhibitory effect on tumor growth in hepatocellular carcinoma (HCC). Gene expression profile analysis revealed that the expression of key enzymes in the mevalonate pathway were increased when ASPP2 was downregulated. HCC cells gained higher cholesterol levels and enhanced tumor-initiating capability in response to the depletion of ASPP2. Simvastatin, a mevalonate pathway inhibitor, efficiently abrogated ASPP2 depletion-induced anchorage-independent cell proliferation, resistance to chemotherapy drugs in vitro, and tumor growth in xenografted nude mice. Mechanistically, ASPP2 interacts with SREBP-2 in the nucleus and restricts the transcriptional activity of SREBP-2 on its target genes, which include key enzymes involved in the mevalonate pathway. Moreover, clinical data revealed better prognosis in patients with high levels of ASPP2 and low levels of the mevalonate pathway enzyme HMGCR. Our findings provide functional and mechanistic insights into the critical role of ASPP2 in the regulation of the mevalonate pathway and the importance of this pathway in tumor initiation and tumor growth, which may provide a new therapeutic opportunity for HCC.

Autophagy and senescence: A new insight in selected human diseases

Senescence and autophagy play important roles in homeostasis. Cellular senescence and autophagy commonly cause several degenerative processes, including oxidative stress, DNA damage, telomere shortening, and oncogenic stress; hence, both events are known to be interrelated. Autophagy is well known for its disruptive effect on human diseases, and it is currently proposed to have a direct effect on triggering senescence and quiescence. However, it is yet to be proven whether autophagy has a positive or negative impact on senescence. It is known that elevated levels of autophagy induce cell death, whereas inadequate autophagy can trigger cellular senescence. Both have important roles in human diseases such as aging, renal degeneration, neurodegenerative disorders, and cancer. Therefore, this review aims to highlight the relevance of senescence and autophagy in selected human ailments through a summary of recent findings on the connection and effects of autophagy and senescence in these diseases.

Cellular senescence: a promising strategy for cancer therapy

Cellular senescence, a permanent state of cell cycle arrest, is believed to have originally evolved to limit the proliferation of old or damaged cells. However, it has been recently shown that cellular senescence is a physiological and pathological program contributing to embryogenesis, immune response, and wound repair, as well as aging and age-related diseases. Unlike replicative senescence associated with telomere attrition, premature senescence rapidly occurs in response to various intrinsic and extrinsic insults. Thus, cellular senescence has also been considered suppressive mechanism of tumorigenesis. Current studies have revealed that therapy-induced senescence (TIS), a type of senescence caused by traditional cancer therapy, could play a critical role in cancer treatment. In this review, we outline the key features and the molecular pathways of cellular senescence. Better understanding of cellular senescence will provide insights into the development of powerful strategies to control cellular senescence for therapeutic benefit. Lastly, we discuss existing strategies for the induction of cancer cell senescence to improve efficacy of anticancer therapy.

Autophagy inhibition specifically promotes epithelial-mesenchymal transition and invasion in RAS-mutated cancer cells

Macroautophagy/autophagy inhibition is a novel anticancer therapeutic strategy, especially for tumors driven by mutant RAS. Here, we demonstrate that autophagy inhibition in RAS-mutated cells induces epithelial-mesenchymal transition (EMT), which is associated with enhanced tumor invasion. This is at least partially achieved by triggering the NFKB/NF-κB pathway via SQSTM1/p62. Knockdown of ATG3 or ATG5 increases oncogenic RAS-induced expression of ZEB1 and SNAI2/Snail2, and activates NFKB activity. Depletion of SQSTM1 abolishes the activation of the NFKB pathway induced by autophagy inhibition in RAS-mutated cells. NFKB pathway inhibition by depletion of RELA/p65 blocks this EMT induction. Finally, accumulation of SQSTM1 protein correlates with loss of CDH1/E-cadherin expression in pancreatic adenocarcinoma. Together, we suggest that combining autophagy inhibition with NFKB inhibitors may therefore be necessary to treat RAS-mutated cancer.

Abbreviations: 4-OHT: 4-hydroxytamoxifen; DIC: differential interference contrast; EMT: epithelial-mesenchymal transition; ESR: estrogen receptor; MAPK/ERK: mitogen-activated protein kinase; iBMK: immortalized baby mouse kidney epithelial cells; MET: mesenchymal-epithelial transition; PI3K: phosphoinositide 3-kinase; RNAi: RNA interference; TGFB/TGF-β: transforming growth factor beta; TNF: tumor necrosis factor; TRAF6: TNF receptor associated factor 6.

Deficiency of apoptosis-stimulating protein two of p53 ameliorates acute kidney injury induced by ischemia reperfusion in mice through upregulation of autophagy

Acute kidney injury (AKI) has become a common disorder with a high risk of morbidity and mortality, which remains major medical problem without reliable and effective therapeutic intervention. Apoptosis-stimulating protein two of p53 (ASPP2) is a proapoptotic member that belongs to p53 binding protein family, which plays a key role in regulating apoptosis and cell growth. However, the role of ASPP2 in AKI has not been reported. To explore the role of ASPP2 in the progression of AKI, we prepared an AKI mouse model induced by ischaemia reperfusion (I/R) in wild-type (ASPP2^+/+ ) mice and ASPP2 haploinsufficient (ASPP2^+/- ) mice. The expression profile of ASPP2 were examined in wild-type mice. The renal injury, inflammation response, cellular apoptosis and autophagic pathway was assessed in ASPP2^+/+ and ASPP2^+/- mice. The renal injury, inflammation response and cellular apoptosis was analysed in ASPP2^+/+ and ASPP2^+/- mice treated with 3-methyladenine or vehicle. The expression profile of ASPP2 showed an increase at the early stage while a decrease at the late stage during renal injury. Compared with ASPP2^+/+ mice, ASPP2 deficiency protected mice against renal injury induced by I/R, which mainly exhibited in slighter histologic changes, lower levels of blood urea nitrogen and serum creatinine, and less apoptosis as well as inflammatory response. Furthermore, ASPP2 deficiency enhanced autophagic activity reflecting in the light chain 3-II conversion and p62 degradation, while the inhibition of autophagy reversed the protective effect of ASPP2 deficiency on AKI. These data suggest that downregulation of ASPP2 can ameliorate AKI induced by I/R through activating autophagy, which may provide a novel therapeutic strage for AKI.

Deficiency of apoptosis-stimulating protein two of p53 promotes liver regeneration in mice by activating mammalian target of rapamycin

Although liver regeneration has been intensively studied in various ways, the mechanisms underlying liver regeneration remain elusive. Apoptosis-stimulating protein two of p53 (ASPP2) was discovered as a binding partner of p53 and plays an important role in regulating cell apoptosis and growth. However, the role of ASPP2 in hepatocyte proliferation and liver regeneration has not been reported. The expression profile of ASPP2 was measured in a mouse model with 70% partial hepatectomy (PHX). Liver regeneration and hepatocyte proliferation were detected in wild-type (ASPP2+/+) and ASPP2 haploinsufficient (ASPP2+/-) mice with PHX. The mammalian target of rapamycin (mTOR) and autophagy pathways were analyzed in the ASPP2+/+ and ASPP2+/- mice with PHX. After rapamycin or 3-methyladenine (3-MA) treatment, hepatocyte proliferation and liver regeneration were analyzed in the ASPP2+/+ and ASPP2+/- mice with PHX. ASPP2 expression was shown to be upregulated at the early stage and downregulated at the late stage. Compared to the ASPP2+/+ mice, liver regeneration was enhanced in ASPP2+/- mice with 70% PHX. In addition, compared to the ASPP2+/+ mice, the mTORC1 pathway was significantly upregulated and the autophagic pathway was downregulated in ASPP2+/-mice with 70% PHX. Inhibition of the mTORC1 pathway significantly suppressed liver regeneration in ASPP2+/- mice with 70% PHX. In contrast, disruption of the autophagic pathway further enhanced liver regeneration in ASPP2+/- mice with 70% PHX. ASPP2 deficiency can promote liver regeneration through activating the mTORC1 pathway, which further regulates downstream molecules, such as those related to autophagy and p70S6K expression in mouse model post-PHX.

Divergent mechanisms of metabolic dysfunction drive fibroblast and T-cell senescence

The impact of cellular senescence during ageing is well established, however senescence is now recognised to play a role in a variety of age related and metabolic diseases, such as cancer, autoimmune and cardiovascular diseases. It is therefore crucial to gain a better understanding of the mechanisms that control cellular senescence. In recent years our understanding of the intimate relationship between cell metabolism, cell signalling and cellular senescence has greatly improved. In this review we discuss the differing roles of glucose and protein metabolism in both senescent fibroblast and CD8⁺ T-cells, and explore the impact cellular metabolism has on the senescence-associated secretory phenotype (SASP) of these cell types.

The multifaceted role of autophagy in cancer and the microenvironment

Autophagy is a crucial recycling process that is increasingly being recognized as an important factor in cancer initiation, cancer (stem) cell maintenance as well as the development of resistance to cancer therapy in both solid and hematological malignancies. Furthermore, it is being recognized that autophagy also plays a crucial and sometimes opposing role in the complex cancer microenvironment. For instance, autophagy in stromal cells such as fibroblasts contributes to tumorigenesis by generating and supplying nutrients to cancerous cells. Reversely, autophagy in immune cells appears to contribute to tumor‐localized immune responses and among others regulates antigen presentation to and by immune cells. Autophagy also directly regulates T and natural killer cell activity and is required for mounting T‐cell memory responses. Thus, within the tumor microenvironment autophagy has a multifaceted role that, depending on the context, may help drive tumorigenesis or may help to support anticancer immune responses. This multifaceted role should be taken into account when designing autophagy‐based cancer therapeutics. In this review, we provide an overview of the diverse facets of autophagy in cancer cells and nonmalignant cells in the cancer microenvironment. Second, we will attempt to integrate and provide a unified view of how these various aspects can be therapeutically exploited for cancer therapy.

Impact of iASPP on chemoresistance through PLK1 and autophagy in ovarian clear cell carcinoma

Ovarian clear cell carcinoma (OCCC) is a type of epithelial ovarian cancer that is strongly associated with endometriosis, resistance against conventional chemotherapy and thus poorer prognosis. The expression of inhibitory member of the ASPP family proteins (iASPP) and Polo-like kinase (PLK)1 were significantly higher in OCCC compared to benign cystadenomas and endometriosis. Both protein expressions were found to correlate with chemoresistance in patients with OCCC while high iASPP expression alone was significantly associated with a poor patient survival. The growth of OCCC cell lines, OVTOKO and KK, were inhibited after iASPP silencing. Such effect was related to senescence triggering as evidenced by increased SA-β-Gal staining and p21WAF1/Cip1 expression. Moreover, knockdown of iASPP induced PLK1 downregulation, whereas either genes' silencing sensitized the cells in response to cisplatin treatment. More prominent apoptosis was induced by cisplatin in OCCC cells after the knockdown of either iASPP or PLK1 as evidenced by the formation of more cleaved caspase 3. Heightened chemosensitivity to cisplatin after iASPP knockdown was further demonstrated in in vivo xenograft model. Additionally, both iASPP and PLK1 were shown to regulate autophagic flux as the induction of LC3B-II and LC3 puncta were much less in OCCC cells with either knockdown. Importantly, inhibition of autophagy also enhanced chemosensitivity to cisplatin in OCCC cells. These findings strongly imply that iASPP and PLK1 affect the chemoresistance of OCCC via the regulation of autophagy and apoptosis. Both iASPP and PLK1 can be potential therapeutic targets for treating OCCC in combination with conventional chemotherapy.

Nutrient sensing, growth and senescence

Cell growth is dictated by a wide range of mitogenic signals, the amplitude and relative contribution of which vary throughout development, differentiation and in a tissue-specific manner. The ability to sense and appropriately respond to changes in mitogens is fundamental to control cell growth, and reduced responsiveness of nutrient sensing pathways is widely associated with human disease and ageing. Cellular senescence is an important tumour suppressor mechanism that is characterised by an irreversible exit from the cell cycle in response to replicative exhaustion or excessive DNA damage. Despite the fact that senescent cells can no longer divide, they remain metabolically active and display a range of pro-growth phenotypes that are supported in part by the mTORC1-autophagy signalling axis. As our understanding of the basic mechanisms of controlling mTORC1-autophagy activity and cell growth continues to expand, we are able to explore how changes in nutrient sensing contribute to the acquisition and maintenance of cellular senescence. Furthermore, while the protective effect of senescence to limit cellular transformation is clear, more recently, the age-related accumulation of these pro-inflammatory senescent cells has been shown to contribute to a decline in organismal fitness. We will further discuss whether dysregulation of nutrient sensing pathways can be targeted to promote senescent cell death which would have important implications for healthy ageing.

DNA damage regulated autophagy modulator 1 recovers the function of apoptosis-stimulating of p53 protein 2 on inducing apoptotic cell death in Huh7.5 cells

Overexpression of apoptosis-stimulating of p53 protein 2 (ASPP2) can induce apoptotic cell death in hepatoma cells, which contributes to a killing effect of ASPP2 on treating hepatocellular carcinoma (HCC). In the present study, ASPP2 overexpression failed to induce apoptotic cell death in the HCC Huh7.5 cell line, but promoted autophagy development by inhibiting AKT/mTOR pathway. Inhibition of autophagy using 3-methyladenosine recovered the function of ASPP2 on inducing apoptotic cell death, indicating that ASPP2-induced autophagy has an anti-apoptotic role in Huh7.5 cells. A previous study demonstrated that ASPP2-induced autophagy could induce apoptosis in a CHOP- and DRAM-dependent manner, in which CHOP is involved in the initiation of autophagy and DRAM allows autophagy to induce apoptosis. In the present study, CHOP and DRAM were not involved in ASPP2-induced autophagy; however, the induction of DRAM overexpression recovered the apoptosis-inducing function of ASPP2, indicating that DRAM overexpression switches the role of ASPP2-induced autophagy from anti-apoptotic to pro-apoptotic in Huh7.5 cells. Thus, in combination with DRAM, ASPP2 may better perform its pro-apoptotic role by preventing the occurrence of anti-apoptotic autophagy.

Mechanisms and functions of cellular senescence

Cellular senescence is a highly stable cell cycle arrest that is elicited in response to different stresses. By imposing a growth arrest, senescence limits the replication of old or damaged cells. Besides exiting the cell cycle, senescent cells undergo many other phenotypic alterations such as metabolic reprogramming, chromatin rearrangement, or autophagy modulation. In addition, senescent cells produce and secrete a complex combination of factors, collectively referred as the senescence-associated secretory phenotype, that mediate most of their non-cell-autonomous effects. Because senescent cells influence the outcome of a variety of physiological and pathological processes, including cancer and age-related diseases, pro-senescent and anti-senescent therapies are actively being explored. In this Review, we discuss the mechanisms regulating different aspects of the senescence phenotype and their functional implications. This knowledge is essential to improve the identification and characterization of senescent cells in vivo and will help to develop rational strategies to modulate the senescence program for therapeutic benefit.

Inhibition of KRAS-dependent lung cancer cell growth by deltarasin: blockage of autophagy increases its cytotoxicity

Deltarasin is a recently identified small molecule that can inhibit KRAS–PDEδ interactions by binding to a hydrophobic pocket on PDEδ, resulting in the impairment of cell growth, KRAS activity, and RAS/RAF signaling in human pancreatic ductal adenocarcinoma cell lines. Since KRAS mutations are the most common oncogene mutations in lung adenocarcinomas, implicated in over 30% of all lung cancer cases, we examined the ability of deltarasin to inhibit KRAS-dependent lung cancer cell growth. Here, for the first time, we document that deltarasin produces both apoptosis and autophagy in KRAS-dependent lung cancer cells in vitro and inhibits lung tumor growth in vivo. Deltarasin induces apoptosis by inhibiting the interaction of with PDEδ and its downstream signaling pathways, while it induces autophagy through the AMPK-mTOR signaling pathway. Importantly, the autophagy inhibitor, 3-methyl adenine (3-MA) markedly enhances deltarasin-induced apoptosis via elevation of reactive oxygen species (ROS). In contrast, inhibition of ROS by N-acetylcysteine (NAC) significantly attenuated deltarasin-induced cell death. Collectively, these observations suggest that the anti-cancer cell activity of deltarasin can be enhanced by simultaneously blocking “tumor protective” autophagy, but inhibited if combined with an anti-oxidant.

Expression and significance of ASPP2 in squamous carcinoma of esophagus

To study the significance of apoptosis stimulating protein of P53 2 (ASPP2) expression in esophageal squamous cell carcinoma (ESCC), immunohistochemistry S-P method was used to examine the expression of ASPP2 in 136 cases of ESCC, 35 cases of high grade intraepithelial neoplasia (HGIN), 29 cases of low grade intraepithelial neoplasia (LGIN) and 37 cases of normal esophageal epithelium (NEE). The associations of ASPP2 expression with clinicopathological data and overall survival (OS) were also analyzed. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to evaluate ASPP2 expression in a total of 20 matched human ESCC tumor tissues and normal adjacent tissues (NAT). In addition, EC109 cells were treated with cisplatin (CDDP) in vitro for 24 h (the intervention group) and the control group was set up at the same time. Western blot was used to examine the expression of ASPP2 protein between the two groups. The expression of ASPP2 decreased progressively from NEE to LGIN, to HGIN, and to ESCC, and it was related to TNM stage, histological differentiation and lymph node metastasis in ESCC (P < 0.05). ASPP2 was a protective factor of patients with ESCC (P = 0.008). The relative expression of ASPP2 mRNA was markedly downregulated in ESCC compared with the paired NAT (P < 0.01). Western blot results showed that cells in the intervention group could express ASPP2 while there was no expression of ASPP2 in the control group. Taken together, these results indicate that the abnormal expression of ASPP2 may play an important role for development and metastasis in ESCC.

ASPP2 Inhibits the Profibrotic Effects of Transforming Growth Factor-β1 in Hepatic Stellate Cells by Reducing Autophagy

BACKGROUND

Apoptosis-stimulating protein of p53-2 (ASPP2) is a damage-inducible P53-binding protein that enhances damage-induced apoptosis. Fibrosis is a wound-healing response, and hepatic stellate cells (HSCs) are key players in liver fibrogenesis. However, little is known about the relationship between ASPP2 and hepatic fibrosis.

AIMS

We investigated the effects of ASPP2 overexpression in HSCs and the role of ASPP2 in mouse liver fibrogenesis.

METHODS

Human HSCs (LX-2 cells) were pre-incubated with GFP adenovirus (Ad) or ASPP2 adenovirus (AdASPP2) for 24 h and then treated with or without TGF-β1. ASPP2^+/- and ASPP2+/+ Balb/c mice were used to examine the effects of ASPP2 on liver fibrosis in vivo. ASPP2+/+ Balb/c mice were generated by injecting AdASPP2 into the tail vein of ASPP2 WT Balb/c mice; all mice received intraperitoneal injections of carbon tetrachloride.

RESULTS

In this study, ASPP2 was found to markedly inhibit TGF-β1-induced fibrogenic activation of LX-2 cells. Further experiments using an autophagic flux assay confirmed that ASPP2 reduced the fibrogenic activation of LX-2 cells by inhibiting autophagy. Moreover, we found that ASPP2 overexpression attenuated the anti-apoptotic effects of TGF-β1 in LX-2 cells. The extent of liver fibrosis was markedly reduced in ASPP2+/+ mouse liver tissue compared with control mice; however, in ASPP2^+/- mice, hepatic collagen deposition was significantly increased.

CONCLUSION

These results suggest that TGF-β1-induced autophagy is required for the fibrogenic response in LX-2 cells and that ASPP2 may both inhibit TGF-β1-induced autophagy and decrease liver fibrosis.

Dioscin enhances osteoblastic cell differentiation and proliferation by inhibiting cell autophagy via the ASPP2/NF-κβ pathway

Dioscin, a typical steroid saponin, has been reported to promote osteoblastic cell differentiation. However, the underling mechanisms remain to be elucidated. In the present study, it was identified that dioscin (0.5, 1, 5, 10 and 25 µg/ml) promoted MC3T3‑E1 cell proliferation and differentiation in a dose‑dependent manner. Western blot analysis showed that dioscin regulated autophagy‑associated protein expression in MC3T3‑E1 cells; it promoted the expression of apoptosis stimulated protein of p53‑2 (ASPP2), and inhibited the expression of nuclear factor (NF)‑κβ and microtubule‑associated protein 1 light chain 3β, in a concentration‑dependent manner. Caffeic acid phenethyl ester (CAPE) was used to inhibit the activation of NF‑κB and examine the effect of the ASPP2/NF‑κβ pathway on osteoblastic cell differentiation, proliferation and autophagy. It was identified that CAPE reversed the regulation of dioscin on osteoblastic cell differentiation, proliferation and autophagy. In conclusion, the present study revealed that dioscin promoted osteoblast proliferation and differentiation by inhibiting cell autophagy via the ASPP2/NF‑κβ pathway. These results are the first, to the best of our knowledge, to reveal the involvement of autophagy in the effects of dioscin on the prevention and therapy of osteoporosis.

Mitochondria in Cell Senescence: Is Mitophagy the Weakest Link?

Cell senescence is increasingly recognized as a major contributor to the loss of health and fitness associated with aging. Senescent cells accumulate dysfunctional mitochondria; oxidative phosphorylation efficiency is decreased and reactive oxygen species production is increased. In this review we will discuss how the turnover of mitochondria (a term referred to as mitophagy) is perturbed in senescence contributing to mitochondrial accumulation and Senescence-Associated Mitochondrial Dysfunction (SAMD). We will further explore the subsequent cellular consequences; in particular SAMD appears to be necessary for at least part of the specific Senescence-Associated Secretory Phenotype (SASP) and may be responsible for tissue-level metabolic dysfunction that is associated with aging and obesity. Understanding the complex interplay between these major senescence-associated phenotypes will help to select and improve interventions that prolong healthy life in humans.

SEARCH STRATEGY AND SELECTION CRITERIA

Data for this review were identified by searches of MEDLINE, PubMed, and references from relevant articles using the search terms "mitochondria AND senescence", "(autophagy OR mitophagy) AND senescence", "mitophagy AND aging" and related terms. Additionally, searches were performed based on investigator names. Abstracts and reports from meetings were excluded. Articles published in English between 1995 and 2017 were included. Articles were selected according to their relevance to the topic as perceived by the authors.

Autophagy suppresses Ras-driven epithelial tumourigenesis by limiting the accumulation of reactive oxygen species

Activation of Ras signalling occurs in ~30% of human cancers; however, activated Ras alone is not sufficient for tumourigenesis. In a screen for tumour suppressors that cooperate with oncogenic Ras (Ras^V12) in Drosophila, we identified genes involved in the autophagy pathway. Bioinformatic analysis of human tumours revealed that several core autophagy genes, including GABARAP, correlate with oncogenic KRAS mutations and poor prognosis in human pancreatic cancer, supporting a potential tumour-suppressive effect of the pathway in Ras-driven human cancers. In Drosophila, we demonstrate that blocking autophagy at any step of the pathway enhances Ras^V12-driven epithelial tissue overgrowth via the accumulation of reactive oxygen species and activation of the Jun kinase stress response pathway. Blocking autophagy in Ras^V12 clones also results in non-cell-autonomous effects with autophagy, cell proliferation and caspase activation induced in adjacent wild-type cells. Our study has implications for understanding the interplay between perturbations in Ras signalling and autophagy in tumourigenesis, which might inform the development of novel therapeutics targeting Ras-driven cancers.

EGR-1/ASPP1 inter-regulatory loop promotes apoptosis by inhibiting cyto-protective autophagy

The decrease of ASPP1 (Apoptosis-Stimulating Protein of p53 1), a known p53 activator, has been linked to carcinogenesis and the cytotoxic resistance in various cancers, yet the underlying mechanisms of ASPP1 expression and its complex functions are not yet clear. Here, we report that ASPP1 forms an inter-regulatory loop with Early Growth Response 1 (EGR-1), and promotes apoptosis via inhibiting cyto-protective autophagy, independent of the well-documented p53-dependent mechanisms. We show that ASPP1 mRNA and protein were remarkably elevated by ectopic EGR-1 expression or endogenous EGR-1 activation, in cells with different tissue origins and p53 status. Conversely, RNAi-mediated EGR-1 knockdown suppressed ASPP1. The further mechanism studies revealed that ASPP1 promoter, mapped to -283/+88, which contained three conserved EGR-1 binding sites, was required for both binding and transactivity of EGR-1. In addition, we demonstrate that ASPP1 promoted EGR-1 in a positive feedback loop by preventing proteasome-mediated EGR-1 degradation or promoting EGR-1 nuclear import in response to anticancer natural compound Quercetin. Furthermore, albeit activating p53 in the nucleus is the well-studied function of ASPP1, we found that ASPP1 was predominately localized in the cytoplasm. Interestingly, the cytoplasmic ASPP1 retained its pro-apoptosis capability. Mechanistically, ASPP1 suppressed Atg5-Atg12 and also bound with Atg5-Atg12 to prevent its further complex formation with Atg16, resulting in the inhibition of cyto-protective autophagy. In conclusion, our results provide new insights into EGR-1/ASPP1 regulatory loop in sensitizing Quercetin-induced apoptosis. EGR-1/ASPP1, therefore, may be potentially used as therapeutic targets to improve cancer's response to pro-apoptosis treatments.

UVB-Induced Senescence of Human Dermal Fibroblasts Involves Impairment of Proteasome and Enhanced Autophagic Activity

In the current study, we have extended previous findings aiming at a better understanding of molecular mechanisms underlying UVB-induced senescence of diploid human dermal fibroblasts (HDFs), an experimental model to study the process of photoaging in the skin. We provide evidence that the inhibition of proteasomal degradation of damaged proteins and the activation of autophagosome formation are early events in UVB-induced senescence of HDFs, dependent on UVB-induced accumulation of reactive oxygen species. Our data suggest that autophagy is required for the establishment of the senescent phenotype in UVB-treated HDFs and that inhibition of autophagy is sufficient to change the cell fate from senescence to cell death by apoptosis. Studies in reconstructed skin equivalents revealed that UVB irradiation triggers hallmarks of autophagy induction in the dermal layer. These findings have potential implications for fundamental as well as translational research into skin aging, in particular photoaging.

Autophagy and the Cell Cycle: A Complex Landscape

Autophagy is a self-degradation pathway, in which cytoplasmic material is sequestered in double-membrane vesicles and delivered to the lysosome for degradation. Under basal conditions, autophagy plays a homeostatic function. However, in response to various stresses, the pathway can be further induced to mediate cytoprotection. Defective autophagy has been linked to a number of human pathologies, including neoplastic transformation, even though autophagy can also sustain the growth of tumor cells in certain contexts. In recent years, a considerable correlation has emerged between autophagy induction and stress-related cell-cycle responses, as well as unexpected roles for autophagy factors and selective autophagic degradation in the process of cell division. These advances have obvious implications for our understanding of the intricate relationship between autophagy and cancer. In this review, we will discuss our current knowledge of the reciprocal regulation connecting the autophagy pathway and cell-cycle progression. Furthermore, key findings involving nonautophagic functions for autophagy-related factors in cell-cycle regulation will be addressed.