Article

The Signaling Adaptor p62 Is an Important NF-??B Mediator in Tumorigenesis

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Abstract

The balance between cell death and survival, two critical aspects of oncogenic transformation, determines the outcome of tumorigenesis. Nuclear factor-kappaB (NF-kappaB) is a critical regulator of survival; it is induced by the oncogene Ras and, when inhibited, accounts for the cell death response of Ras-transformed cells. Here, we show that the signaling adaptor p62 is induced by Ras, its levels are increased in human tumors, and it is required for Ras-induced survival and transformation. p62-/- mice are resistant to Ras-induced lung adenocarcinomas. p62 is necessary for Ras to trigger IkappaB kinase (IKK) through the polyubiquitination of tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), and its deficiency produces increased reactive oxygen species (ROS) levels, which account for the enhanced cell death and reduced tumorigenicity of Ras in the absence of p62.

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... Second, p62, as an adaptor protein, has a TRAF6-binding domain and specifically interacts with TRAF6, but not with TRAF5 or TRAF2, to facilitate TRAF6 K63-linked ubiquitination, in which both the N-terminal dimerization domain and the UBA domain are also required. p62 plays oncogenic roles in different contexts, underscored by the facts that (i) its upregulation has been detected in several types of cancer, and (ii) it is induced by the oncoprotein Ras, which underlies at least 25% of human cancers (26)(27)(28)(29). We showed recently that p62 mRNA and protein levels are in correlation with EBV latency programs, in which p62 mediates reactive oxygen species (ROS)-induced autophagy and DNA damage response (30). ...
... LMP1 activates the p62 gene promoter via the NF-jB and AP1 axes. The p62 promoter (2.0 kb upstream of the transcription start site [TSS]) contains well-characterized NF-k B and AP1 binding sites, among others (Fig. 1A), and is activated by NF-k B and AP1 in diverse contexts (26,27,(34)(35)(36). Furthermore, in our recent study, we unexpectedly found that short hairpin RNA (shRNA)-mediated deficiency of LIMD1, an adaptor protein required for LMP1 signal transduction to NF-k B and AP1 activation, reduces p62 expression in virus-transformed cells (37). ...
... As a signal-transducing adaptor, p62 has been documented to directly interact with TRAF6, leading to NF-k B activation in diverse biological contexts (26,41,42). LMP1 is well known to interact with TRAF6 and other TRAF family members (8,43). ...
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As a ubiquitin sensor and a signal-transducing adaptor, p62 is crucial for NF-κB activation, which involves the ubiquitin machinery in diverse contexts. However, whether p62 is required for EBV LMP1 activation of NF-κB is an open question.
... Our laboratory has demonstrated that the autophagy substrate and signaling adaptor p62 (encoded by SQSTM1 gene) is a critical regulator of CAF biology Linares et al., 2017;Valencia et al., 2014). p62 has a dual role in cancer (Duran et al., 2008(Duran et al., , 2011Moscat et al., 2016;Umemura et al., 2016). Although it plays an oncogenic function in the tumor epithelium, it is a suppressor of tumor progression by restraining CAF activation Goruppi and Dotto, 2013;Linares et al., 2017;Reina-Campos et al., 2018;Valencia et al., 2014). ...
... In fact, incubation of stromal cells with conditioned media (CM) from PCa cells effectively reduced p62 protein and mRNA levels in stromal cells, without any effect by the CM from normal prostate epithelial cells (PrEC or RWEP1) ( Figures 1D and 1E). To determine whether the reduction in SQSTM1 mRNA was due to inhibited transcriptional activity, we used a luciferase reporter under the control of SQSTM1 promoter (Duran et al., 2008). PCa CM reduced the activity of the luciferase reporter ( Figure 1F), suggesting that stromal p62 downregulation is mediated through the repression of SQSTM1 promoter by a soluble factor secreted by tumor cells. ...
... Thus, although lactate reportedly induces autophagy (Brisson et al., 2016), which can contribute to lactate effects in tumor cells and the stroma, we show here that blocking autophagy or the proteosome failed to prevent p62 downregulation by lactate. At the transcriptional level, p62 has been shown to be regulated by several transcription factors, including AP-1, NRF2, NF-κB, and TFEB, under different conditions (Duran et al., 2008;Jain et al., 2010;Ling et al., 2012;Park et al., 2019). Here, we have identified the AP-1 binding site in the SQSTM1 promoter as the critical element accounting for lactate-mediated p62 downregulation. ...
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Reduced p62 levels are associated with the induction of the cancer-associated fibroblast (CAF) phenotype, which promotes tumorigenesis in vitro and in vivo through inflammation and metabolic reprogramming. However, how p62 is downregulated in the stroma fibroblasts by tumor cells to drive CAF activation is an unresolved central issue in the field. Here we show that tumor-secreted lactate downregulates p62 transcriptionally through a mechanism involving reduction of the NAD+/NADH ratio, which impairs poly(ADP-ribose)-polymerase 1 (PARP-1) activity. PARP-1 inhibition blocks the poly(ADP-ribosyl)ation of the AP-1 transcription factors, c-FOS and c-JUN, which is an obligate step for p62 downregulation. Importantly, restoring p62 levels in CAFs by NAD+ renders CAFs less active. PARP inhibitors, such as olaparib, mimick lactate in the reduction of stromal p62 levels, as well as the subsequent stromal activation both in vitro and in vivo, which suggests that therapies using olaparib would benefit from strategies aimed at inhibiting CAF activity.
... The tumor-promoting properties of p62 are underscored by the facts that p62 is upregulated in different cancer contexts, including LIHC, and breast and prostate cancers (2,(13)(14)(15)(16)(17), and that p62 is induced by the oncoprotein Ras that accounts for more than 25% of human cancers (18). p62 overexpression in LIHC predicts poor prognosis (15). ...
... p62 overexpression in LIHC predicts poor prognosis (15). In mouse models with defective autophagy, p62 ablation decreases tumorigenesis (18). ...
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Liver hepatocellular carcinoma (LIHC) is the major form of liver cancer that is the fourth most common cause of cancer death worldwide. It has been reported that the multifunctional protein p62 (also known as SQSTM1) plays a cancer-promoting role in LIHC, but the detailed mechanisms underlying p62 interaction with LIHC remains unclear. To gain a comprehensive understanding of p62 interaction with LIHC in clinical settings, we performed bioinformatic analyses using various online algorithms derived from high throughput profiling. Our results indicate that p62 expression is significantly upregulated, partially due to its promoter demethylation, rather than p62 gene mutation, in LIHC. Mutation of TP53, CTNNB1, or ALB significantly correlates with, and mutation of AXIN1 reversely correlates with, the p62 expression level. Its upregulation occurs as early as liver cirrhosis, and go through all stages of the carcinogenesis. HCV infection makes a significant contribution to p62 upregulation in LIHC. We further identified p62-associated molecular signatures in LIHC, including many genes that are involved in antioxidant stress and metabolism, such as SRX1 and TXNRD1. Regarding to the clinical outcome, p62 expression level reversely correlates with the survival of LIHC patients (p<0.01). Importantly, we experimentally validated that p62 depletion in liver cancer cell lines downregulates the expression of SRX1 and TXNRD1 at both transcriptional and translational levels, and reduces cell proliferation. As the potential mechanisms underlying the tumor-promoting role of p62, we show that p62 upregulation is remarkably associated with reprogramming of pathways mediated by p53, Wnt/β-catenin, and Keap1-NRF2, which are crucial for oncogenesis in many contexts. Our findings provide a comprehensive insight into the interaction between p62 and LIHC, offering valuable information for understanding of LIHC pathogenesis.
... Autophagy induces cell death and regulates cell proliferation by accelerating genetic stability through removing oncogenic proteins [391]. For example, autophagy has been found to destroy a number of proteins implicated in oncogenesis, including the mutant form of p53, DRAM, p62, NF-κB, promyelocytic leukemia/retinoic acid receptor α (PML/RARα), BCR-ABL1, and sequestosome 1 (SQSTM1) [352,[403][404][405][406][407][408][409]. In addition, autophagy's inducement stress-related response is one possible method by which autophagy serves as a tumor suppressor, including oncogenic stress, ER-stress and DNA-damage-stress, etc. [410,411]. ...
... Cellular senescence is a program of permanent cell division arrest that can be produced in response to oncogenic stress to avoid malignant transformation [412,413]. Increased levels of ER-stress and DNA-damage-stress resulted from autophagy suppression, which in turn contributed to oncogenesis through increased levels of p62 accumulation [405,[414][415][416]. ...
Article
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Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.
... p62 signaling is regulated at both the transcriptional and the posttranslational level. NF-κB controls p62 gene transcription [42]. p62 expression is upregulated by a variety of stressors such as oxidative stress, protein aggregation and proinflammatory cytokines, which promote the activation of NF-κB pathway [43][44][45]. ...
... p62 signaling is regulated at both the transcriptional and the posttranslational level [42]. The regulation of p62-droplet formation is poorly understood. ...
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SQSTM1/p62, as a major autophagy receptor, forms droplets that are critical for cargo recognition, nucleation, and clearance. p62 droplets also function as liquid assembly platforms to allow the formation of autophagosomes at their surfaces. It is unknown how p62-droplet formation is regulated under physiological or pathological conditions. Here, we report that p62-droplet formation is selectively blocked by inflammatory toxicity, which induces cleavage of p62 by caspase-6 at a novel cleavage site D256, a conserved site across human, mouse, rat, and zebrafish. The N-terminal cleavage product is relatively stable, whereas the C-terminal product appears undetectable. Using a variety of cellular models, we show that the p62 N-terminal caspase-6 cleavage product (p62-N) plays a dominant-negative role to block p62-droplet formation. In vitro p62 phase separation assays confirm this observation. Dominant-negative regulation of p62-droplet formation by caspase-6 cleavage attenuates p62 droplets dependent autophagosome formation. Our study suggests a novel pathway to modulate autophagy through the caspase-6–p62 axis under certain stress stimuli.
... The damaged organelles are captured by the autophagosome membrane, recognized by the autophagy substrate p62, and then degraded by lysosomes [87]. Autophagy inhibition is beneficial to tumor growth, as its deficiency leads to the accumulation of p62, and the binding of p62 to mTORC1 inhibits autophagy and activates NF-κB and NRF-2, which further promotes tumor cell proliferation [88][89][90]. ...
... The damaged organelles are captured by the autophagosome membrane, recognized by the autophagy substrate p62, and then degraded by lysosomes [87]. Autophagy inhibition is beneficial to tumor growth, as its deficiency leads to the accumulation of p62, and the binding of p62 to mTORC1 inhibits autophagy and activates NF-κB and NRF-2, which further promotes tumor cell proliferation [88][89][90]. From a metabolic point of view, the existence of autophagy allows cells to still metabolize in a starved state, which means that the activation of autophagy is sufficient to maintain tumor cell survival [87,91]. CRP has not been researched in the field of autophagy for a long time, but it is currently certain that its effects on autophagy include but are not limited to regulating the PI3K/AKT/GSK-3c/mTOR pathway ( Figure 5). ...
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Citri Reticulatae Pericarpium (CRP), also known as “chenpi”, is the most common qi-regulating drug in traditional Chinese medicine. It is often used to treat cough and indigestion, but in recent years, it has been found to have multi-faceted anti-cancer effects. This article reviews the pharmacology of CRP and the mechanism of the action of flavonoids, the key components of CRP, against cancers including breast cancer, lung cancer, prostate cancer, hepatic carcinoma, gastric cancer, colorectal cancer, esophageal cancer, cervical cancer, bladder cancer and other cancers with a high diagnosis rate. Finally, the specific roles of CRP in important phenotypes such as cell proliferation, apoptosis, autophagy and migration–invasion in cancer were analyzed, and the possible prospects and deficiencies of CRP as an anticancer agent were evaluated.
... For instance, p62 has a myriad of roles beyond binding autophagic cargo, such as functions in adipogenesis, the anti-oxidative response, apoptosis, inflammation, or nutrient sensing (reviewed in [81]). In fact, in some tumor models, p62 accumulation has been found to promote tumor growth through the NF-KB pathway [82,83]. Moreover, alternative energy-scavenging strategies, including chaperone-mediated autophagy, an autophagosome-independent form of autophagy, can procure amino acids for protein synthesis and gluconeogenesis (reviewed in [83]). ...
... In fact, in some tumor models, p62 accumulation has been found to promote tumor growth through the NF-KB pathway [82,83]. Moreover, alternative energy-scavenging strategies, including chaperone-mediated autophagy, an autophagosome-independent form of autophagy, can procure amino acids for protein synthesis and gluconeogenesis (reviewed in [83]). It is important to study these potential side issues as they can underlay resistance to TAT-Cx43266-283 and, hence, represent targets for combination therapy to enhance the peptide's antitumor effect. ...
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Autophagy is a physiological process by which various damaged or non-essential cytosolic components are recycled, contributing to cell survival under stress conditions. In cancer, autophagy can have antitumor or protumor effects depending on the developmental stage. Here, we use Western blotting, immunochemistry, and transmission electron microscopy to demonstrate that the antitumor peptide TAT-Cx43266-283, a c-Src inhibitor, blocks autophagic flux in glioblastoma stem cells (GSCs) under basal and nutrient-deprived conditions. Upon nutrient deprivation, GSCs acquired a dormant-like phenotype that was disrupted by inhibition of autophagy with TAT-Cx43266-283 or chloroquine (a classic autophagy inhibitor), leading to GSC death. Remarkably, dasatinib, a clinically available c-Src inhibitor, could not replicate TAT-Cx43266-283 effect on dormant GSCs, revealing for the first time the possible involvement of pathways other than c-Src in TAT-Cx43266-283 effect. TAT-Cx43266-283 exerts an antitumor effect both in nutrient-complete and nutrient-deprived environments, which constitutes an advantage over chloroquine and dasatinib, whose effects depend on nutrient environment. Finally, our analysis of the levels of autophagy-related proteins in healthy and glioma donors suggests that autophagy is upregulated in glioblastoma, further supporting the interest in inhibiting this process in the most aggressive brain tumor and the potential use of TAT-Cx43266-283 as a therapy for this type of cancer.
... p62/SQSTM1, a well-known cargo adapter for autophagy, is a ubiquitous and multimodular scaffold protein, including the N-terminal PB1 domain, the ZZ-type zinc finger (ZZ) domain, the nuclear localization signal (NLS), the TRAF6 binding (TB) domain, the nuclear export signal (NES), the LIR domain, the Keap1-interacting region (KIR), and the C-terminal UBA domain. Beyond autophagy, p62 also regulates diverse cellular events through interaction with a plethora of partners by a series of domains (Moscat et al., 2007), including redox homeostasis maintenance (Rantanen et al., 2013), inflammation control (Duran et al., 2008), and metabolism (Duran et al., 2011), which has been associated with different human pathologies, such as neurodegenerative and metabolic diseases (Nakaso et al., 2004;Ramesh Babu et al., 2008;Rea et al., 2014;Rodriguez et al., 2006), bone and muscle disorders (Laurin et al., 2002), and tumor (Duran et al., 2008;Mathew et al., 2009;Puissant et al., 2012). Recent progress in the field has implicated that p62 also functions in DNA-damage repair. ...
... p62/SQSTM1, a well-known cargo adapter for autophagy, is a ubiquitous and multimodular scaffold protein, including the N-terminal PB1 domain, the ZZ-type zinc finger (ZZ) domain, the nuclear localization signal (NLS), the TRAF6 binding (TB) domain, the nuclear export signal (NES), the LIR domain, the Keap1-interacting region (KIR), and the C-terminal UBA domain. Beyond autophagy, p62 also regulates diverse cellular events through interaction with a plethora of partners by a series of domains (Moscat et al., 2007), including redox homeostasis maintenance (Rantanen et al., 2013), inflammation control (Duran et al., 2008), and metabolism (Duran et al., 2011), which has been associated with different human pathologies, such as neurodegenerative and metabolic diseases (Nakaso et al., 2004;Ramesh Babu et al., 2008;Rea et al., 2014;Rodriguez et al., 2006), bone and muscle disorders (Laurin et al., 2002), and tumor (Duran et al., 2008;Mathew et al., 2009;Puissant et al., 2012). Recent progress in the field has implicated that p62 also functions in DNA-damage repair. ...
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p62, a well-known adaptor of autophagy, plays multiple functions in response to various stresses. Here, we report a function for p62 in base excision repair that is distinct from its known functions. Loss of p62 impairs base excision repair capacity and increases the sensitivity of cancer cells to alkylating and oxidizing agents. In response to alkylative and oxidative damage, p62 is accumulated in the nucleus,acetylated by hMOF,and deacetylated by SIRT7, and acetylated p62 is recruited to chromatin. The chromatin-enriched p62 directly interacts with APE1, a key enzyme of the BER pathway, and promotes its endonuclease activity, which facilitates BER and cell survival. Collectively, our findings demonstrate that p62 is a regulator of BER and provide further rationale for targeting p62 as a cancer therapeutic strategy.
... It is therefore likely that apoptosis might mediate part of the cytotoxic effect of NSP6. On the other hand, lysosome dysfunction and the resulting autophagic flux impairment have been linked to activation of other downstream pro-inflammatory signaling cascades, such as AIM2 inflammasomes [34], SQSTM1/p62-nuclear factor κB signaling [35] and cyclic GMP AMP synthase (cGAS)-STING pathway [36]. It would be equally important to investigate the potential involvement of these pro-inflammatory pathways in the pathogenicity of NSP6. ...
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A recent mutation analysis suggested that Non-Structural Protein 6 (NSP6) of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a key determinant of the viral pathogenicity. Here, by transcriptome analysis, we demonstrated that the inflammasome-related NOD-like receptor signaling was activated in SARS-CoV-2-infected lung epithelial cells and Coronavirus Disease 2019 (COVID-19) patients’ lung tissues. The induction of inflammasomes/pyroptosis in patients with severe COVID-19 was confirmed by serological markers. Overexpression of NSP6 triggered NLRP3/ASC-dependent caspase-1 activation, interleukin-1β/18 maturation, and pyroptosis of lung epithelial cells. Upstream, NSP6 impaired lysosome acidification to inhibit autophagic flux, whose restoration by 1α,25-dihydroxyvitamin D3, metformin or polydatin abrogated NSP6-induced pyroptosis. NSP6 directly interacted with ATP6AP1, a vacuolar ATPase proton pump component, and inhibited its cleavage-mediated activation. L37F NSP6 variant, which was associated with asymptomatic COVID-19, exhibited reduced binding to ATP6AP1 and weakened ability to impair lysosome acidification to induce pyroptosis. Consistently, infection of cultured lung epithelial cells with live SARS-CoV-2 resulted in autophagic flux stagnation, inflammasome activation, and pyroptosis. Overall, this work supports that NSP6 of SARS-CoV-2 could induce inflammatory cell death in lung epithelial cells, through which pharmacological rectification of autophagic flux might be therapeutically exploited.
... We observed that TcdB decreased the levels of total NFKBIA/IKB (an inhibitor of NFKB), enhanced the phosphorylation of NFKB RELA/p65 subunit at serine 536, and increased RELA/p65 nuclear translocation ( Figure 1C and Fig. S1C). To determine the mechanism by which TcdB activated NFKB, we examined the role of autophagy since SQSTM1/p62 (an autophagic receptor accumulated during autophagic flux impairment) is a wellestablished upstream activator of NFKB [22,23]. Consistent with our hypothesis, TcdB induced the concomitant accumulation of LC3-II and SQSTM1/p62 (left panel of Figure 1D and Fig. S1D), which is suggestive of autophagic flux impairment [24]. ...
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Clostridioides difficile infection (CDI) is a common cause of nosocomial diarrhea. TcdB is a major C. difficile exotoxin that activates macrophages to promote inflammation and epithelial damage. Lysosome impairment is a known trigger for inflammation. Herein, we hypothesize that TcdB could impair macrophage lysosomal function to mediate inflammation during CDI. Effects of TcdB on lysosomal function and the downstream pro-inflammatory SQSTM1/p62-NFKB (nuclear factor kappa B) signaling were assessed in cultured macrophages and in a murine CDI model. Protective effects of two lysosome activators (i.e., vitamin D3 and carbamazepine) were assessed. Results showed that TcdB inhibited CTNNB1/β-catenin activity to downregulate MITF (melanocyte inducing transcription factor) and its direct target genes encoding components of lysosomal membrane vacuolar-type ATPase, thereby suppressing lysosome acidification in macrophages. The resulting lysosomal dysfunction then impaired autophagic flux and activated SQSTM1-NFKB signaling to drive the expression of IL1B/IL-1β (interleukin 1 beta), IL8 and CXCL2 (chemokine (C-X-C motif) ligand 2). Restoring MITF function by enforced MITF expression or restoring lysosome acidification with 1α,25-dihydroxyvitamin D3 or carbamazepine suppressed pro-inflammatory cytokine expression in vitro. In mice, gavage with TcdB-hyperproducing C. difficile or injection of TcdB into ligated colon segments caused prominent MITF downregulation in macrophages. Vitamin D3 and carbamazepine lessened TcdB-induced lysosomal dysfunction, inflammation and histological damage. In conclusion, TcdB inhibits the CTNNB1-MITF axis to suppress lysosome acidification and activates the downstream SQSTM1-NFKB signaling in macrophages during CDI. Vitamin D3 and carbamazepine protect against CDI by restoring MITF expression and lysosomal function in mice.
... Second, Duran and coauthors reported another SQSTM1-NFKB1 antioxidant gene transcription pathway [87]. They demonstrated that oncogene Ras could induce SQSTM1 in human cancers. ...
Article
Macroautophagy/autophagy is an evolutionarily well-conserved recycling process in response to stress conditions, including a burst of reactive oxygen species (ROS) production. High level of ROS attack key cellular macromolecules. Protein cysteinyl thiols or non-protein thiols as the major redox-sensitive targets thus constitute the first-line defense. Autophagy is unique, because it removes not only oxidized/damaged proteins but also bulky ROS-generating organelles (such as mitochondria and peroxisome) to restrict further ROS production. The oxidative regulations of autophagy occur in all processes of autophagy, from induction, phagophore nucleation, phagophore expansion, autophagosome maturation, cargo delivery to the lysosome, and finally to degradation of the cargo and recycling of the products, as well as autophagy gene transcription. Mechanically, these regulations are achieved through direct or indirect manners. Direct thiol oxidation of key proteins such as ATG4, ATM and TFEB are responsible for specific regulations in phagophore expansion, cargo recognition and autophagy gene transcription, respectively. Meanwhile, oxidation of certain redox-sensitive chaperone-like proteins (e.g. PRDX family members and PARK7) may impair a nonspecifically local reducing environment in the phagophore membrane, and influence BECN1-involved phagophore nucleation and mitophagy recognition. However, ROS do exhibit some inhibitory effects on autophagy through direct oxidation of key autophagy regulators such as ATG3, ATG7 and SENP3 proteins. SQSTM1 provides an alternative antioxidant mechanism when autophagy is unavailable or impaired. However, it is yet to be unraveled how cells evolve to equip proteins with different redox susceptibility and in their correct subcellular positions, and how cells fine-tune autophagy machinery in response to different levels of ROS.Abbreviations: AKT1/PKB: AKT serine/threonine kinase 1; AMPK: AMP-activated protein kinase; ATG: autophagy related; ATM: ATM serine/threonine kinase; BAX: BCL2 associated X, apoptosis regulator; BECN1: beclin 1; BH3: BCL2-homology-3; CAV1: caveolin 1; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CTSB: cathepsin B; CTSL: cathepsin L; DAPK: death associated protein kinase; ER: endoplasmic reticulum; ETC: electron transport chain; GSH: glutathione; GSTP1: glutathione S-transferase pi 1; H2O2: hydrogen peroxide; HK2: hexokinase 2; KEAP1: kelch like ECH associated protein 1; MAMs: mitochondria-associated ER membranes; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MAPK8/JNK1: mitogen-activated protein kinase 8; MAP3K5/ASK1: mitogen-activated protein kinase kinase kinase 5; MCOLN1: mucolipin 1; MMP: mitochondrial membrane potential; MTOR: mechanistic target of rapamycin kinase; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; NFKB1: nuclear factor kappa B subunit 1; NOX: NADPH oxidase; O2-: superoxide radical anion; p-Ub: phosphorylated Ub; PARK7/DJ-1: Parkinsonism associated deglycase; PE: phosphatidylethanolamine; PEX5: peroxisomal biogenesis factor 5; PINK1: PTEN induced kinase 1; PPP3CA/calcineurin: protein phosphatase 3 catalytic subunit beta; PRDX: peroxiredoxin; PRKAA1: protein kinase AMP-activated catalytic subunit alpha 1; PRKD/PKD: protein kinase D; PRKN/parkin: parkin RBR E3 ubiquitin protein ligase; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PTEN: phosphatase and tensin homolog; ROS: reactive oxygen species; SENP3: SUMO specific peptidase 3; SIRT1: sirtuin 1; SOD1: superoxide dismutase 1; SQSTM1/p62: sequestosome 1; SUMO: small ubiquitin like modifier; TFEB: transcription factor EB; TRAF6: TNF receptor associated factor 6; TSC2: TSC complex subunit 2; TXN: thioredoxin; TXNRD1: thioredoxin reductase 1; TXNIP: thioredoxin interacting protein; Ub: ubiquitin; ULK1: unc-51 like autophagy activating kinase 1.
... Although inflammatory signatures in the lung and intestine exhibit different features (e.g., increased TNF and IL1B in the lung, and increased IFNL and ISGs in the intestine), none of these phenotypes required any stimulus from microbiota, indicating that hyperinflammation and microbial dysbiosis are completely independent in these animals. We also found that neither STING1, which is involved in induction of both inflammation and autophagy [37,38], nor SQSTM1, which may also contribute to regulation of inflammatory pathways [39,40], play any role in epg5 −/associated inflammatory lung phenotypes. Thus, our study in the epg5 −/mouse model broadens the It has been shown in multiple studies that deficiency of autophagy genes is associated with hyperinflammation in multiple organs (e.g., lung, intestine and peritoneum) via elevation of different proinflammatory cytokines including type I IFNs, IFNG, TNF and IL1B [14,15,18,[20][21][22]24]. In a recent study, defects in autophagy genes in intestinal epithelial cells are reported to induce type I IFN responses, driven by the commensal microbiota [24]. ...
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Mutations in the macroautophagy/autophagy gene EPG5 are responsible for Vici syndrome, a human genetic disease characterized by combined immunodeficiency. Previously, we found that epg5−/- mice exhibit hyperinflammation in the lungs mediated by IL1B/IL-1β and TNF/TNFα, resulting in resistance to influenza. Here, we find that disruption of Epg5 results in protection against multiple enteric viruses including norovirus and rotavirus. Gene expression analysis reveals IFNL/IFN-λ responsive genes as a key alteration. Further, mice lacking Epg5 exhibit substantial alterations of the intestinal microbiota. Surprisingly, germ-free mouse studies indicate Epg5-associated inflammation of both the intestine and lung is microbiota-independent. Genetic studies support IFNL signaling as the primary mediator of resistance to enteric viruses, but not of microbial dysbiosis, in epg5−/- mice. This study unveils an important role, unexpectedly independent of the microbiota, for autophagy gene Epg5 in host organism protection by modulating intestinal IFNL responses. Abbreviations: CTNNB1: catenin (cadherin associated protein), beta 1; DAPI: 4′,6-diamidino-2-phenylindole; EPG5: ectopic P-granules autophagy protein 5 homolog (C. elegans); FT: fecal transplant; IFI44: interferon-induced protein 44; IFIT1: interferon-induced protein with tetratricopeptide repeats 1; IFNG/IFN-γ: interferon gamma; IFNL/IFN-λ: interferon lambda; IFNLR1: interferon lambda receptor 1; IL1B/IL-1β: interleukin 1 beta; ISG: interferon stimulated gene; GF: germ-free; LEfSe: linear discriminant analysis effect size; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MNoV: murine norovirus; MX2: MX dynamin-like GTPase 2; OAS1A: 2’-5’ oligoadenylate synthetase 1A; RV: rotavirus; SPF: specific-pathogen free; SQSTM1/p62: sequestosome 1; STAT1: signal transducer and activator of transcription 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK-binding kinase 1; TNF/TNFα: tumor necrosis factor
... Mice are a widely used pre-clinical cancer research model system and have been used in numerous autophagy-modulation studies (Frese and Tuveson 2007, Amaravadi et al., 2007, Komatsu et al., 2007, Duran et al., 2008, Yang et al., 2011. However, many human tumors do not grow in immunodeficient mouse models which makes it impossible to study certain cancers using this model. ...
Article
Hydroxychloroquine (HCQ) is being tested in a number of human clinical trials to determine the role of autophagy in response to standard anticancer therapies. However, HCQ pharmacodynamic responses are difficult to assess in patients and preclinical studies in mouse models are equivocal with regard to HCQ exposure and inhibition of autophagy. Here, pharmacokinetic (PK) assessment of HCQ in non-tumor bearing mice following intraperitoneal (IP) dosing established 60 mg/kg as the human equivalent dose of HCQ in mice. Autophagy inhibition, cell proliferation, and cell death were assessed in 2D cell culture and 3D tumor organoids in breast cancer. Mice challenged with breast cancer xenografts were then treated with 60 mg/kg HCQ via IP dosing and subsequent PK and pharmacodynamic (PD) responses were assessed. Although autophagic flux was significantly inhibited in cells irrespective of autophagy dependency status, autophagy dependent tumors had decreased cell proliferation and increased cell death at earlier time points compared to autophagy independent tumors. Overall, this study shows that 2D cell culture, 3D tumor organoids, and in vivo studies produce similar results and in vitro studies can be used as surrogates to recapitulate in vivo antitumor responses of HCQ. Significance Statement Autophagy dependent tumors, but not autophagy independent tumors, have decreased cell proliferation and increased cell death following single agent hydroxychloroquine treatment. However, hydroxychloroquine causes decreased autophagic flux regardless of autophagy status, suggesting its clinical efficacy in the context of autophagy inhibition.
... Emphasizing the link between autophagy and inflammation, impaired autophagy in C9orf72-deficient myeloid cells leads to the accumulation of the pro-inflammatory STING (stimulator of interferon genes) protein [440]. Likewise, ALS-associated mutations in TBK1, OPTN, SQSTM1, and VCP all affect autophagy as well as microglial function and innate immunity [192,205,206,[441][442][443]. Collectively, these findings reinforce the convergence between inflammation and autophagy in microglia, and their importance for ALS pathogenesis. ...
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Mechanisms of protein homeostasis are crucial for overseeing the clearance of misfolded and toxic proteins over the lifetime of an organism, thereby ensuring the health of neurons and other cells of the central nervous system. The highly conserved pathway of autophagy is particularly necessary for preventing and counteracting pathogenic insults that may lead to neurodegeneration. In line with this, mutations in genes that encode essential autophagy factors result in impaired autophagy and lead to neurodegenerative conditions such as amyotrophic lateral sclerosis (ALS). However, the mechanistic details underlying the neuroprotective role of autophagy, neuronal resistance to autophagy induction, and the neuron-specific effects of autophagy-impairing mutations remain incompletely defined. Further, the manner and extent to which non-cell autonomous effects of autophagy dysfunction contribute to ALS pathogenesis are not fully understood. Here, we review the current understanding of the interplay between autophagy and ALS pathogenesis by providing an overview of critical steps in the autophagy pathway, with special focus on pivotal factors impaired by ALS-causing mutations, their physiologic effects on autophagy in disease models, and the cell type-specific mechanisms regulating autophagy in non-neuronal cells which, when impaired, can contribute to neurodegeneration. This review thereby provides a framework not only to guide further investigations of neuronal autophagy but also to refine therapeutic strategies for ALS and related neurodegenerative diseases. Abbreviations: ALS: amyotrophic lateral sclerosis; Atg: autophagy-related; CHMP2B: charged multivesicular body protein 2B; DPR: dipeptide repeat; FTD: frontotemporal dementia; iPSC: induced pluripotent stem cell; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PINK1: PTEN induced kinase 1; RNP: ribonuclear protein; sALS: sporadic ALS; SPHK1: sphingosine kinase 1; TARDBP/TDP-43: TAR DNA binding protein; TBK1: TANK-binding kinase 1; TFEB: transcription factor EB; ULK: unc-51 like autophagy activating kinase; UPR: unfolded protein response; UPS: ubiquitin-proteasome system; VCP: valosin containing protein.
... These results could be attributed to the fact that activated Kras turns on many downstream signaling pathways, including PI3K/AKT, mitogen-activated protein kinase, and NFKβ. [44] Kras activates NFKβ, which is vital for cell viability and tumor transformation, along with concomitant p53 loss. [45] In addition, TANK-binding kinase 1, a serine-threonine kinase capable of activating NFKβ, was also reported as a synthetically lethal partner with mutant Kras. ...
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OBJECTIVE Oral squamous cell carcinoma (OSCC) comprises about 10% of head and neck cancer. 5-fluorouracil (5-FU) is commonly used for the treatment of OSCC. However, it has many limitations due to its identified side effects. Therefore, this work compared squamous cell carcinoma (SCC) cells’ chemosensitivity to 5-FU, mesenchymal stem cells-derived microvesicles (MVs), and their combination. METHODS Human SCC cell line (SCC152) was subjected to 5-FU or MVs or their combination for 24 h and 48 h. Inverted microscopic evaluation of apoptosis, MTT cell proliferation assay, DNA comet assay, and detection of NFKβ, Kras, and Braf genes’ expression were performed. RESULTS The combination group, compared to 5-FU or MVs treated groups, showed the most apparent apoptotic features. Cell proliferation was significantly decreased, while the tailed DNA% was significantly increased in the combination group versus either the 5-FU or MVs groups. The combination group showed a significant decrease in NFKβ, Kras, and Braf genes’ expression than the 5-FU or MVs treated groups. The correlation between cell proliferation and the studied genes showed a very strong positive linear relationship, while a strong negative linear relationship existed between cell proliferation and tailed DNA%. CONCLUSION The combination of MVs and 5-FU enhanced the genotoxicity and cytotoxicity of the SCC152 cell line compared to using either of them alone. Moreover, downregulation of NFKβ, Kras, and Braf genes’ expression was associated with enhanced apoptotic features, decreased cell proliferation, and enhanced tailed DNA%.
... And although, MG-132 rescues some of this nuclear I B content, it is still appreciably lower than that found in corresponding IL-1 -treated p62-WT cells. Furthermore, our findings of enhanced association of mitochondrial 28S ribosomal complex proteins with I B in the presence of p62-coexpression relative to its absence, also support such a p62-assisted mitochondrial I B -import (Fig. 6G) Given that p62 is documented to promote proliferation and reduce apoptosis (55,56) and mitochondrial I B is thought to serve a unique protective role against apoptosis, it is conceivable that by enhancing I B -mitochondrial import, p62 may similarly play a beneficial role in hepatic inflammatory responses. ...
Preprint
We have previously documented that in liver cells, the multifunctional protein scaffold p62/SQSTM1 is closely associated with IκBα, an inhibitor of the transcriptional activator NF-κB. Such an intimate p62-IκBα association we now document leads to a marked 18-fold proteolytic IκBα-stabilization, enabling its nuclear entry and termination of the NF-κB-activation cycle. In p62 -/- -cells, such termination is abrogated resulting in the nuclear persistence and prolonged activation of NF-κB following inflammatory stimuli. Utilizing various approaches both classic (structural deletion, site-directed mutagenesis) as well as novel (in cell chemical crosslinking), coupled with proteomic analyses, we have defined the precise structural hotspots of p62-IκBα association. Accordingly, we have identified such IκBα hotspots to reside around N-terminal (K38, K47 and K67) and C-terminal (K238/C239) residues in its 5 th ankyrin repeat domain. These sites interact with two hotspots in p62: One in its PB-1 subdomain around K13, and the other comprised of a positively charged patch (R 183 /R 186 /K 187 /K 189 ) in the intervening region between its ZZ- and TB-subdomains. APEX proximity analyses upon IκBα co-transfection of cells with and without p62 have enabled the characterization of the p62 influence on IκBα-protein-protein interactions. Interestingly, consistent with p62’s capacity to proteolytically stabilize IκBα, its presence greatly impaired IκBα’s interactions with various 20S/26S proteasomal subunits. Furthermore, consistent with p62-interaction with IκBα on an interface opposite to that of its NF-κB-interacting interface, p62 failed to significantly affect IκBα-NF-κB interactions. These collective findings together with the known dynamic p62 nucleocytoplasmic shuttling, leads us to speculate that it may be involved in “piggy-back” nuclear transport of IκBα following its NF-κB-elicited transcriptional activation and de novo synthesis, required for the termination of the NF-κB-activation cycle. Consequently, mice carrying a liver specific deletion of p62-residues 68-252 harboring its positively charged patch, reveal age-dependent enhanced liver inflammation. Our findings reveal yet another mode of p62-mediated pathophysiologically relevant regulation of NF-κB. Abstract Figure Highlights p62 binds to and stabilizes IκBα by preventing its proteolytic degradation In-cell chemical crosslinking/LC-MS/MS identified the inter-crosslinked sites Hotspots of p62-IκBα association are defined APEX proximity labeling revealed p62 impaired IκBα-interaction with proteasome p62 chaperones newly synthesized IκBα to terminate NF-κB activation. In Brief The transcriptional activator NF-κB inhibitor, IκBα is proteolytically unstable when uncomplexed. How newly synthesized IκBα escapes degradation to terminate nuclear NF-κB-activation is unknown. Using in-cell chemical crosslinking and proximity labeling MS analyses, we uncovered a novel association of p62 with IκBα via well-defined structural hotspots, which impairs its interaction with the 26S/20S proteasome, extending its life-span and enabling termination of NF-κB-activation. Mice carrying liver-specific genetic deletion of p62-IκBα hotspot exhibit enhanced liver inflammation upon aging, validating this novel p62 role.
... For example, NRF2 degradation is primarily powered by the KEAP1, whereas, phosphorylation of SQSTM1/p62 at S349 may tremendously enhance the adhesion to KEAP1 and subsequently disrupts association between KEAP1 and NRF2, and promotes NRF2 stabilization and activation to facilitate growth of tumor cells, implying crosstalk between SQSTM1/p62-mediated autophagy and the KEAP1-NRF2 system (13,14). Moreover, SQSTM1/p62 acts as a direct transcriptional target of NF-κB and can in turn activate the NF-κB pathway by stimulating inhibitor of NF-κB kinase subunit β/IκB by TNF receptor-associated factor 6 (TRAF6) polyubiquitination (15)(16)(17). In addition, SQSTM1/p62 p.R321C mutation leads to autophagy inhibition by activating the NF-κB pathway in Paget's disease of the bone (18), and as autophagy is inhibited, positive feedback between SQSTM1/p62 and NF-κB interaction can excessively and sustainably trigger the NF-κB pathway, leading to epithelial-mesenchymal transition (EMT) in various RAS-mutated cells (19). ...
Article
Sequestosome 1 (SQSTM1)/p62 is an adapter protein mainly involved in the transportation, degradation and destruction of various proteins that cooperates with components of autophagy and the ubiquitin‑proteasome degradation pathway. Numerous studies have shown that SQSTM1/p62 functions at multiple levels, including involvement in genetic stability or modification, post‑transcriptional regulation and protein function. As a result, SQSTM1/p62 is a versatile protein that is a critical core regulator of tumor cell genetic stability, autophagy, apoptosis and other forms of cell death, malignant growth, proliferation, migration, invasion, metastasis and chemoradiotherapeutic response, and an indicator of patient prognosis. SQSTM1/p62 regulates these processes via its distinct molecular structure, through which it participates in a variety of activating or inactivating tumor‑related and tumor microenvironment‑related signaling pathways, particularly positive feedback loops and epithelial‑mesenchymal transition‑related pathways. Therefore, functioning as a proto‑oncogene or tumor suppressor gene in various types of cancer and tumor‑associated microenvironments, SQSTM1/p62 is capable of promoting or retarding malignant tumor aggression, giving rise to immeasurable effects on tumor occurrence and development, and on patient treatment and prognosis.
... Several studies have linked different cytokines with the regulation of autophagy. When NF-kB is activated after the detection of ROS, cytokines such as IL1B and IL18 are expressed [55,62,84,[101][102][103][104]. In effect, it has been widely described that IL1B expression is stimulated in the event of autophagy. ...
Article
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Age-related macular degeneration (AMD) causes the degeneration of photoreceptors and retinal cells leading to vision loss in older subjects. Among possible exogenous risk factors, it has been recently proposed that long-term exposure to blue light could aggravate the course of AMD. In the search for therapeutic options, plasma rich in growth factors (PRGF) has been shown to enhance cell antioxidant pathways and protect photoreceptors against the harm produced by blue light, although its mechanism of action remains unknown. One possible mechanism, autophagy, is one of the most conservative cell renewal systems used in eukaryotes to destroy cellular components that have been damaged by some kind of insult. The oxidative stress of exposure to blue light is known to induce cell autophagy. In this study, we examined the combined effects on autophagy of blue light and PRGF in a retinal cell line, ARPE19. In response to treatment with both PRGF and blue light, we detected the modulated expression of autophagy markers such as NF-kB, p62/sqstm1, Atg5, LC3 and Beclin1, and inflammatory markers such as IL1B and IL18. Our findings suggest that PRGF promotes cell autophagy in response to exposure to blue light.
... The potential COX-2-independent mechanism of NSAIDs' antineoplastic action includes downregulation of proto-oncogenes, such as c-Myc, and transcriptional factors such as peroxisome proliferator-activated receptor delta (PPARδ), nuclear factor kappalight-chain-enhancer of activated B cells (NF-κB), prostate apoptosis response-4 (PAR-4), and B-cell lymphoma 2 (Bcl-2) [128,129]. Sulindac and indomethacin in vivo studies demonstrated inhibition of tumorigenesis through inhibition of peroxisome proliferatoractivated receptor delta (PPARδ), a gene that is normally regulated by APC [130]. Studies have shown that NSAIDs display anticarcinogenic and chemopreventive properties through the regulation of autophagy in certain types of cancer [131]. ...
Article
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Once it became clear that inflammation takes place in the modulation of different degenerative disease including neurodegenerative, cardiovascular, diabetes and cancer the researchers has started intensive programs evaluating potential role of non-steroidal anti-inflammatory drugs (NSAIDs) in the prevention or therapy of these diseases. This review discusses the novel mechanism of action of NSAIDs and its potential use in the pharmacotherapy of neurodegenerative, cardiovascular, diabetes and cancer diseases. Many different molecular and cellular factors which are not yet fully understood play an important role in the pathogenesis of inflammation, axonal damage, demyelination, atherosclerosis, carcinogenesis thus further NSAID studies for a new potential indications based on precise pharmacotherapy model are warranted since NSAIDs are a heterogeneous group of medicines with relative different pharmacokinetics and pharmacodynamics profiles. Hopefully the new data from studies will fill in the gap between experimental and clinical results and translate our knowledge into successful disease therapy.
... Interestingly, the free UBA domain shows strong preference for Lys63-ubiquitinated cargo [38]. Hence, intermolecular competition of Lys63-ubiquitinated SQSTM1/p62 for cargo binding could inhibit autophagy, while intramolecular blockade of the UBA receptor by long Lys-63-linked chains may redirect SQSTM1/p62 to other functions such as the regulation of apoptosis [39], oxidative stress [40] or NF-kB dependent immune responses [41]. Although not within the scope of this study, our findings emphasize the importance of a thorough dissection of the types of ubiquitin chains attached to SQSTM1/p62 in order to better understand their contribution to the regulation of the autophagy receptor. ...
Article
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Autophagy is an important component of the innate immune response that restricts infection by different types of pathogens. Viruses have developed multiple strategies to avoid autophagy to complete their replication cycle and promote spreading to new hosts. Here, we report that the ubiquitin deconjugases encoded in the N-terminal domain of the large tegument proteins of Epstein–Barr virus (EBV), Kaposi Sarcoma herpesvirus (KSHV) and human cytomegalovirus (HCMV), but not herpes simplex virus-1 (HSV-1), regulate selective autophagy by inhibiting the activity of the autophagy receptor SQSTM1/p62. We found that all the homologs bind to and deubiquitinate SQSTM1/p62 but with variable efficiency, which correlates with their capacity to prevent the colocalization of light chain 3 (LC3) with SQSTM1/p62 aggregates and promote the accumulation of a model autophagy substrate. The findings highlight important differences in the strategies by which herpesviruses interfere with selective autophagy.
... Interestingly, reports indicated that p62 triggers DNA damage and persistent activation of nuclear factor κ B (NF-κB) and nuclear factor erythroid 2-related factor-2 (Nrf-2), two pro-inflammatory and anti-oxidant transcription factors, respectively, that are known to be upregulated in solid tumours (Duran et al., 2008;Inami et al., 2011). Over-activation of NF-κB and Nrf-2 plays an essential role in promoting OC cell survival, migration, and invasion (Macciò and Madeddu, 2012;van der Wijst et al., 2014). ...
Article
Activation of autophagy suppresses ovarian cancer (OC). This in vitro study investigated whether the anti-tumour effect of exendin-4 against OC involves modulation of autophagy and figured out the possible mechanisms of action. SKOV-3 and OVCAR-3 cells (1 × 105/ml) were cultured in DMEM medium and treated with exendin-4 in the presence or absence of chloroquine (CQ), an autophagy inhibitor. In some cases, cells were also treated with exendin- 4 with or without pre-treatment with compound C (CC), an AMPK inhibitor, or insulin-like growth factor (IGF-1), a PI3K/Akt activator. Exendin-4 increased expression of beclin-1 and LC3I/II, suppressed expression of p62, reduced cell survival, migration, and invasion, and increased cell apoptosis and LDH release in both SKOV-3 and OVCAR-3 cells. Besides, exendin-4 reduced phosphorylation of mTORC1, 6SK, 4E-BP1, and Akt but increased phosphorylation of AMPK in both cell lines. These effects were associated with down-regulation of Bcl-2, suppression of nuclear phosphorylation of NF-κB p65, and increased expression of Bax and cleaved caspases 3/8. Chloroquine completely prevented the inhibitory effects of exendin-4 on the cell survival, Bcl-2, NF-κB, and cell invasiveness and abolished its stimulation of cell apoptosis and LDH release. Moreover, only the combined treatment with IGF-1 and CC completely abolished the observed effect of exendin-4 on the expression of beclin-1, LC3I/II, p62, as well as on cell survival, apoptosis, and LDH release. Exendin-4 exhibits a potent anti-tumour cytotoxic effect in SKOV-3 and OVCAR-3 cells by activating the markers of autophagy, mediated by activation of AMPK and inhibition of Akt.
... Down regulation of LAMB3 and LAMA3, which are components of Laminin-332 protein [25], may contribute to the effects of anisomycin. Moreover a decrease of SQSTM1, (also known as p62), which plays a key role in autophagy, might inhibit the NFKB2 signaling pathway, which could result in potent arrest of the cell progression [26]. ...
Article
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Anisomycin is used as a chemical compound that possesses c-Jun N-terminal kinase (JNK)-activating effects. Recently, the potent anti-tumor effects of anisomycin have received much attention. In addition to its JNK-activating effects, anisomycin has been reported to affect gene expression in osteosarcoma, leukemia, hepatocellular carcinoma, ovarian cancer and other cancers. We previously demonstrated that anisomycin induced the degradation of transcription factor GATA-6 in DLD-1 cells (a colorectal cancer cell line) and inhibited their proliferation. However, the details of the gene network involved in the process remain unclear. In this study, we conducted an RNA-seq analysis of differentially expressed genes (DEGs) in anisomycin-treated DLD-1 cells to identify the molecular process of growth-suppressive genes. We found that LAMB3, which regulates cell adhesion and migration, and NFKB2 were down-regulated by anisomycin. In addition, the mRNA expression of several tumor suppressor genes (ATF3, ERRFI1, KLF6, and AKAP12) was transiently enhanced at 3 h after anisomycin treatment. These results suggest that anisomycin blocks a PI3K/Akt-signaling cascade to lead to the suppression of cell growth.
... On one hand, they could work as the activator of autophagy [62][63][64][65][66][67][68]; on the other hand, the nanoparticles constructed from different materials enable to block the autophagy flux and increase the accumulation of P62 [62,65,[69][70][71]. Meanwhile, P62 also participates in the regulation of inflammatory responses via the NF-jB signaling pathway [72,73]. It has been reported that the blockage of autophagy flux could lead to the accumulation of P62 in line with the NF-jB activation and expression of various inflammatory cytokines [74]. ...
Article
Hypothesis Precise modulation of immuno-inflammatory response is crucial to control periodontal diseases and related systemic comorbidities. The present nanosystem with the controlled-release and cell-penetrating manner enhances the inflammation modulation effects of baicalein in human gingival epithelial cells (hGECs) for better oral healthcare. Experiments We constructed a red-emissive mesoporous silica nanoparticle-based nanosystem with cell-penetrating poly(disulfide) (CPD) capping, through a facile in-situ polymerization approach. It was featured with a glutathione-responsive manner and instant cellular internalization capacity for precisely delivering baicalein intracellularly. Laboratory experiments assessed whether and how the nanosystem per se with the delivered baicalein could modulate immuno-inflammatory responses in hGECs. Findings The in-situ polymerized CPD layer capped the nanoparticles and yet controlled the release of baicalein in a glutathione-responsive manner. The CPD coating could facilitate cellular internalization of the nanosystem via endocytosis and thiol-mediated approaches. Notably, the intracellularly released baicalein effectively downregulated the expression of pro-inflammatory cytokines through inhibiting the NF-κB signaling pathway. The nanosystem per se could modulate immuno-inflammatory responses by passivating the cellular response to interlukin-1β. This study highlights that the as-synthesized nanosystem may serve as a novel multi-functional vehicle to modulate innate host response via targeting the NF-κB pathway for precision healthcare.
... (19) NF-κB/p62 signaling plays a critical role in regulating autophagy and cell survival. (20) Recently, it was reported that C-cigarette smoke causes ferritin-selective autophagy (ferritinophagy) and ferroptosis in epithelial cells of human respiratory system. (21,22) Ferroptosis is a catalytic Fe(II)-dependent RCD accompanied by phospholipid peroxidation, (23,24) which may be closely associated with autophagy (25) and carcinogenesis. ...
Article
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Smoke from conventional cigarettes (C-cigarettes) contains various reactive oxygen species and toxic chemicals, which potentially cause oxidative damage not only to airways but also to the whole body, leading eventually to diseases, including emphysema, advanced atherosclerosis, and cancer. Many heat-not-burn tobacco products (HTPs) have been commercialized recently in Japan to maintain the smoking population by advertising that HTPs are less toxic. However, there were few studies reported from neutral organizations whether HTPs are indeed less damaging. To evaluate the potential capacity of HTPs to induce oxidative stress, we here compared two different HTPs with two types of C-cigarettes, using human fibroblast IMR90SV cells and 5% aqueous extracts in 10-ml phosphate-buffered saline (50-ml smoke/10 s). HTPs exhibited significantly lower oxidative toxicity in comparison to C-cigarettes. Whereas C-cigarettes induced ferroptosis in fibroblasts, the effects of HTPs were significantly reduced by measuring the levels of peroxides, pro-inflammatory cytokine expression, autophagy, catalytic Fe(II) and 8-hydroxy-2'-deoxyguanosine. Notably, major portions of C-cigarettes-induced pathogenic responses were inhibited by catalase. However, HTPs still induced p62 autophagy-adaptor at 5%-dilution and caused lethal effects to fibroblasts with undiluted solution. In conclusion, HTPs smoke per se can be toxic despite less toxicity in comparison to C-cigarettes, which warrants further investigation.
... LMP1 promotes p53 stability by inhibiting K48-linked ubiquitination of p53 mediated by the E3 ligase MDM2, while LMP1 enhances p53 accumulation by inducing K63-linked ubiquitination of p53 that is mediated by the tumor necrosis factor receptor-associated factor 2 (TRAF2), contributing to the suppression of cell apoptosis and cell cycle arrest in EBV latently infected cells [38]. The ubiquitin sensor and adaptor protein SQSTM1/p62 has multiple oncogenic roles during diverse conditions [39,40]. p62 is an autophagy adaptor that contributes to formation of protein aggregates and can also be regulated as a substrate by autophagy [41,42]. ...
Article
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Deregulation of the ubiquitin–proteasome system (UPS) plays a critical role in the development of numerous human cancers. Epstein–Barr virus (EBV), the first known human tumor virus, has evolved distinct molecular mechanisms to manipulate the ubiquitin–proteasome system, facilitate its successful infection, and drive opportunistic cancers. The interactions of EBV antigens with the ubiquitin–proteasome system can lead to oncogenesis through the targeting of cellular factors involved in proliferation. Recent studies highlight the central role of the ubiquitin–proteasome system in EBV infection. This review will summarize the versatile strategies in EBV-mediated oncogenesis that contribute to the development of specific therapeutic approaches to treat EBV-associated malignancies.
... B. Des analyses plus particulières montrent ensuite que MELK induit en fait la phosphorylation de SQSTM1(Sequestrosome1)/p62, elle-même responsable de l'activation de la voie NF-B (Duran et al., 2008;Long et al., 2010). Ainsi, l'activation de MELK aboutit alors à la phosphorylation de IB- (NF-B inhibitor ), qui lève alors son inhibition sur NF-B/p65. ...
Thesis
Le mélanome, cancer de la peau au fort potentiel métastatique, représente aujourd’hui plus de 280 000 cas, dont plus de 60 000 décès, chaque année dans le monde. Lorsqu’il atteint un stade métastatique, la mortalité de ce cancer augmente drastiquement et le taux de survie à 5 ans n’est plus que de 25%. En effet, malgré les progrès significatifs apportés ces dix dernières années dans la prise en charge thérapeutique du mélanome métastatique avec l’arrivée des thérapies ciblées et des immunothérapies, plus de 50% des patients ne disposent pas de solution thérapeutique leur procurant une réponse efficace à long-terme. Aujourd’hui, il est donc primordial de trouver de nouvelles stratégies thérapeutiques pour ces patients.Après s’être intéressé aux propriétés anticancéreuses de la Metformine, une molécule utilisée initialement en tant qu’antidiabétique, notre laboratoire a développé des composés dérivés de cette molécule en collaboration avec l’Institut de Chimie de Nice (ICN) afin d’améliorer les propriétés pharmacocinétiques et d’amplifier l’effet antinéoplasique de la Metformine, jusqu’alors insuffisant(es) pour apporter un bénéfice chez l’Homme atteint d’un mélanome en monothérapie (essai clinique NCT01840007). Nous avons alors identifié un composé, le CRO15, capable d’induire la mort des cellules cancéreuses à des doses 1000 fois moins importantes que la Metformine. Cette molécule provoque la mort des cellules cancéreuses par autophagie et apoptose par plusieurs mécanismes moléculaires. D’une part, le CRO15 va induire une perturbation de la respiration mitochondriale et provoquer l’activation de la voie AMPK. D’autre part, la molécule va inhiber directement la kinase MELK, un oncogène surexprimé dans de nombreux cancers, ce qui va induire l’activation de la protéine p53. Les deux voies induisent alors conjointement l’expression de la protéine REDD1, responsable de la mort cellulaire observée. De plus, dans des xénogreffes de cellules de mélanome chez la souris, CRO15 est capable de provoquer la diminution de la croissance tumorale.Ensuite, étant donné les effets de la Metformine sur la réponse immunitaire antitumorale, notamment via l’activation de la voie AMPK, nous nous sommes intéressés au rôle de CRO15 dans cette réponse. Nous avons alors montré dans un modèle de carcinome de colon que CRO15 induisait, in vivo, la potentialisation de la réponse aux anti-PD1 en termes de survie et de croissance tumorale chez des souris immunocompétentes.L’analyse des populations immunitaires infiltrant la tumeur indique que CRO15 induirait une diminution des macrophages M2 dans ces tumeurs. De plus, nous avons montré in vitro que notre composé modulait la polarisation des macrophages humains en induisant la diminution de l’expression des marqueurs de surface M2, principalement. Bien qu’elles doivent être approfondies, ces données suggèrent qu’en plus de provoquer un effet cytotoxique dans les cellules cancéreuses, CRO15 serait capable de moduler la réponse immunitaire antitumorale pour favoriser l’élimination de la tumeur. Cette molécule serait donc un candidat prometteur dans le cadre de l’élaboration d’une nouvelle stratégie thérapeutique contre le mélanome et d’autres cancers solides.
... The SQSTM1 gene causes various carcinomas, including HCC. Its product p62, which acts as an adaptor to degrade molecules through autophagy, provides insight into the effects of SQSTM1 in various cancers [30]. In breast cancer, the PPIA/CrkII axis modulates host antitumor immune escape [31]. ...
Article
Full-text available
Hepatocellular carcinoma (HCC) is the most malignant and poor-prognosis subtype of primary liver cancer. The scRNA-seq approach provides unique insight into tumor cell behavior at the single-cell level. Cytokine signaling in the immune system plays an important role in tumorigenesis and has both pro-tumorigenic and anti-tumorigenic functions. A biomarker of cytokine signaling in immune-related genes (CSIRG) is urgently required to assess HCC patient diagnosis and treatment. By analyzing the expression profiles of HCC single cells, TCGA, and ICGC data, we discovered that three important CSIRG (PPIA, SQSTM1, and CCL20) were linked to the overall survival of HCC patients. Cancer status and three hub CSIRG were taken into account while creating a risk nomogram. The nomogram had a high level of predictability and accuracy. Based on the CSIRG risk score, a distinct pattern of somatic tumor mutational burden (TMB) was detected between the two groups. The enrichment of the pyrimidine metabolism pathway, purine metabolism pathway, and lysosome pathway in HCC was linked to the CSIRG high-risk scores. Overall, scRNA-seq and bulk RNA-seq were used to create a strong CSIRG signature for HCC diagnosis.
... Nuclear erythroid-related factor 2 (Nrf2), a transcription factor mainly activated by PERK and IRE1, also plays a pivotal role in the crosstalk between UPR and NF-κB. Studies on the linkage between Nrf2 and autophagy have shown that Nrf2 activates IKK and subsequent NF-κB by enhancing the expression of p62, which explains NF-κB-dependent autophagy activation (135)(136)(137). Complex interrelation indicates that Nrf2 influences NF-κB both positively and negatively due to various circumstances. ...
Article
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Atherosclerosis (AS) is a common cardiovascular disease with complex pathogenesis, in which multiple pathways and their interweaving regulatory mechanism remain unclear. The primary transcription factor NF-κB plays a critical role in AS via modulating the expression of a series of inflammatory mediators under various stimuli such as cytokines, microbial antigens, and intracellular stresses. Endoplasmic reticulum (ER) stress, caused by the disrupted synthesis and secretion of protein, links inflammation, metabolic signals, and other cellular processes via the unfolded protein response (UPR). Both NF-κB and ER stress share the intersection regarding their molecular regulation and function and are regarded as critical individual contributors to AS. In this review, we summarize the multiple interactions between NF-κB and ER stress activation, including the UPR, NLRP3 inflammasome, and reactive oxygen species (ROS) generation, which have been ignored in the pathogenesis of AS. Given the multiple links between NF-κB and ER stress, we speculate that the integrated network contributes to the understanding of molecular mechanisms of AS. This review aims to provide an insight into these interactions and their underlying roles in the progression of AS, highlighting potential pharmacological targets against the atherosclerotic inflammatory process.
... In response to TNFα, autophagy appears to be required for prolonged transcriptional activity of NF-κB by autophagic degradation of IκBα, which suggests that degradative systems other than the 26S proteasome may sustain long-term NF-κB activation (130). Further evidences suggest that the autophagy cargo receptor SQSTM1/p62 modulates NF-κΒ activity at the level of IKK in a mouse model of Ras-induced lung adenocarcinoma (131). These observations indicate that NF-κB and autophagy are intimately interconnected via a complex network of transcriptional and transcription-independent signals. ...
Thesis
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Es wird vermutet, dass das Zusammenspiel von NF-κB-Signalen und Autophagie die Entzündung in verschiedenen zellulären Kontexten und als Reaktion auf unterschiedliche Stimuli reguliert. Der molekulare Mechanismus, durch den diese beiden Signalwege bei der Regulierung der Entzündungsreaktion zusammenwirken, ist jedoch noch nicht bekannt. Mithilfe biochemischer Analysen und bildgebender Verfahren haben wir zum ersten Mal die Interaktion zwischen dem autophagischen Marker LC3 und der NF-κB/p65-Untereinheit als Reaktion auf verschiedene Stressbedingungen charakterisiert. Wir konnten zeigen, dass die Anhäufung von LC3 im Zellkern nach der NF-κB-Aktivierung mit p65 interagiert, was durch die Ubiquitinierung des p65-Proteins gefördert und durch den Cargo-Rezeptor p62 erkannt wird. Zusammengenommen weisen diese Daten auf eine neue Rolle von p62 beim Transport von im Kern ubiquitiniertem p65 zu Autophagosomen hin, wo es abgebaut wird, um die entzündungsbedingte NF-κB-Hyperaktivierung zu kontrollieren. Diese Erkenntnisse sind wichtig für die Entwicklung neuer therapeutischer Strategien gegen Krankheiten, die mit einer gestörten Autophagie und einer konstitutiven NF-κB-Aktivität einhergehen. Die NF-κB-Signalübertragung spielt nicht nur eine entscheidende Rolle bei Entzündungen und der Tumorbildung, sondern ist auch für Entwicklungsprozesse wichtig. Durch die Etablierung von 3D-Organoid-Kulturen aus dem Dünndarm und unter Verwendung verschiedener Mauslinien weisen wir im zweiten Teil der Arbeit nach, dass NF-κB eine wichtige Funktion bei der Zelldifferenzierung und der Erhaltung von Stammzellen in vivo und ex-vivo spielt. Wir konnten zeigen, dass die Proliferation und das Absterben von Darmepithelzellen (IEC) bei Mäusen mit ubiquitärer Unterdrückung der NF-κB-Aktivität unverändert sind, während die Zahl der Becherzellen auf Kosten der Paneth-Zellen zunimmt. Zusammenfassend lässt sich sagen, dass unsere Ergebnisse eine neue IEC-immanente Rolle von NF-κB bei Entscheidungen über das Zellschicksal und die Differenzierung aufzeigen, die über die Regulierung der Wnt-Signale und der Sox9-Expression stromabwärts von NF-κB erfolgt. Die hier beschriebenen Erkenntnisse verbessern unser Verständnis der NF-κB-Funktionen in der Stammzellbiologie, die, wenn sie dereguliert sind, auch Auswirkungen auf die Entzündung des Darms und die Tumorentstehung haben.
... P62 can recruit TRAF6 and initiate NF-κB signaling. Knockdown of p62 or disruption of p62-TRAF6 binding can lead to cell cycle arrest and apoptosis in MDS/AML cell lines and clinical samples [126]. Importantly, in the study, the lack of p62 had little effect on the lifespan and function of normal HSPCs. ...
Article
It is emerging that autophagy-related proteins regulate the adaptive response to DNA damage in maintaining genome stability at multiple pathways. Here, we discuss recent insights into how autophagy-related proteins participate in DNA damage repair processes, influence chromosomal instability, and regulate the cell cycle through autophagy-dependent and independent actions. There is increasing awareness of the importance of these pathways mediated by autophagy-related proteins to DNA damage response (DDR), and disturbances in these regulatory connections may be linked to genomic instability participated in various human diseases, such as cancer and aging.
... Besides autophagy, SQSTM1 is also involved in the regulation of many cellular signaling pathways, including MTORC1 pathway [19][20][21][22]. In response to various intracellular stimuli or environmental cues, such as nutrients or growth factors, MTORC1 is recruited to the lysosomal surface for activation [23,24]. ...
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Autophagy has emerged as a key regulator of cell metabolism. Recently, we have demonstrated that autophagy is involved in RNA metabolism by regulating ribosomal RNA (rRNA) synthesis. We found that autophagy-deficient cells display much higher 47S precursor rRNA level, which is caused by the accumulation of SQSTM1/p62 (sequestosome 1) but not other autophagy receptors. Mechanistically, SQSTM1 accumulation potentiates the activation of MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) signaling, which facilitates the assembly of RNA polymerase I pre-initiation complex at ribosomal DNA (rDNA) promoter regions and leads to the activation of rDNA transcription. Finally, we showed that SQSTM1 accumulation is responsible for the increase in protein synthesis, cell growth and cell proliferation in autophagy-deficient cells. Taken together, our findings reveal a regulatory role of autophagy and autophagy receptor SQSTM1 in rRNA synthesis and may provide novel mechanisms for the hyperactivated rDNA transcription in autophagy-related human diseases. Abbreviations: 5-FUrd: 5-fluorouridine; LAP: MAP1LC3/LC3-associated phagocytosis; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PIC: pre-initiation complex; POLR1: RNA polymerase I; POLR1A: RNA polymerase I subunit A; rDNA: ribosomal DNA; RRN3: RRN3 homolog, RNA polymerase I transcription factor; rRNA: ribosomal RNA; SQSTM1/p62: sequestosome 1; TP53INP2: tumor protein p53 inducible nuclear protein 2; UBTF: upstream binding transcription factor.
... However, it has been shown that after oncogenic transformation, p62 is necessary for tumor initiation and tumor progression: the induced formation of Her2-breast cancer and the RAS-induced formation of lung cancer are hindered in p62 knockout animals [29,30]. Furthermore, the tumor does not lose its dependence on p62 but becomes dependent, a phenomenon that is known as the non-oncogenic addiction [31]. ...
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The p62 protein, also called sequestosome 1 (SQSTM1), is a ubiquitin-binding scaffold protein. In human oncology, although the interest in the function of this protein is recent, the knowledge is now numerous but its role in tumorigenesis is not yet clear. This preliminary study aims to evaluate the immunohistochemical expression of p62 in 38 cases of feline mammary carcinoma with different grades of differentiation and in 12 non-neoplastic mammary gland tissues, to assess the expression level and a possible correlation with malignancy. The expression of p62 was statistically higher in carcinoma compared to non-neoplastic mammary glands: 28 feline mammary carcinomas (73.7%) had a high p62 expression score, three (7.9%) had a moderate expression, while 7 cases (18.4 %) had a low expression. The grade of differentiation of the carcinoma was not correlated with the p62 expression. Even if new knowledge came out about the role and expression of p62 in veterinary oncology, this study represents the first approach in feline oncology. Our results, although preliminary, are similar to the results of breast cancer therefore, also in the cat, p62 could be considered a possible oncotarget.
... In addition, daphnetin, a natural compound used for coronary heart diseases, could be used for ovarian cancer therapy, as it triggers ROS-induced cell death and activates autophagy by regulating the AMPK/Akt/mTOR pathway [156]. Moreover, in mouse models, the overexpression of selective autophagy receptor p62 (SQSTM1) upon autophagy loss promotes increased oxidative stress and tumor growth [157][158][159]. These data suggest that tumor suppression may play a role in several distinct autophagy proteins that function in different stages in the pathway, thereby underscoring that both the loss of autophagy is a hallmark of cancer, and that autophagy functions as a tumor suppressor. ...
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Autophagy is an evolutionarily conserved and tightly regulated process that plays an important role in maintaining cellular homeostasis. It involves regulation of various genes that function to degrade unnecessary or dysfunctional cellular components, and to recycle metabolic substrates. Autophagy is modulated by many factors, such as nutritional status, energy level, hypoxic conditions, endoplasmic reticulum stress, hormonal stimulation and drugs, and these factors can regulate autophagy both upstream and downstream of the pathway. In cancer, autophagy acts as a double-edged sword depending on the tissue type and stage of tumorigenesis. On the one hand, autophagy promotes tumor progression in advanced stages by stimulating tumor growth. On the other hand, autophagy inhibits tumor development in the early stages by enhancing its tumor suppressor activity. Moreover, autophagy drives resistance to anticancer therapy, even though in some tumor types, its activation induces lethal effects on cancer cells. In this review, we summarize the biological mechanisms of autophagy and its dual role in cancer. In addition, we report the current understanding of autophagy in some cancer types with markedly high incidence and/or lethality, and the existing therapeutic strategies targeting autophagy for the treatment of cancer.
... Thus, the high level of p62 mRNA expression observed in breast cancer compared with that of normal tissues may reflect the transcriptional activation of p62. It has been reported that p62 is a target gene in cancer, which is located downstream of nuclear factor-E2-related factor 2, nuclear factor-ĸB and activator protein-1 (34,73,74). A detailed mechanism of p62 gene expression in ALDH1positive luminal B CSCs will need to be investigated. ...
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Background/aim: p62 (also known as sequestosome 1) is involved in cancer progression, and high expression of p62 indicates poor clinical outcome in several cancer types. However, the association between p62 gene expression and cancer stem cells (CSCs) in breast cancer subtypes remains unclear. Materials and methods: In the present study, genomic datasets of primary breast cancer (The Cancer Genome Atlas, n=593; and Molecular Taxonomy of Breast Cancer International Consortium, n=2,509) were downloaded. p62 Expression was then examined in normal and breast cancer tissues derived from the same patients. Kaplan-Meier and multivariate Cox regression analyses were employed to evaluate disease-specific survival. Next, the effect on cell viability and in vitro tumor-sphere formation of p62 knockdown using targeted small interfering RNA was assessed by using cells with high activity of aldehyde dehydrogenase 1 (ALDH1high). Results: Patients with normal-like, luminal A or luminal B breast cancer with p62high had poor prognosis. Furthermore, patients with p62high ALDH1A3high luminal B type also exhibited poor prognoses. Knockdown of p62 suppressed viability and tumor-sphere formation by ALDH1high cells of the luminal B-type cell lines BT-474 and MDA-MB-361. These results suggest that p62 is essential for cancerous progression of ALDH1-positive luminal B breast CSCs, and contributes to poor prognosis of luminal B breast cancer. Conclusion: p62 is potentially a prognostic marker and therapeutic target for ALDH1-positive luminal B breast CSCs.
... One possible mechanism for enhanced carcinogenesis following autophagy ablation is the pathogenic accumulation of autophagy cargo receptor proteins, which are normally degraded via the autophagy-lysosome system, together with their cargo. As most autophagy cargo receptor proteins have multiple functions and act as signaling molecules [41], their accumulation in autophagydeficient cells can promote tumor formation and progression via multiple mechanisms, including aberrant signal activation [42,43]. For example, Atg5 or Atg7 deletion in mouse liver accelerates adenoma formation [28,29]. ...
Article
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Macroautophagy (hereafter autophagy) is a catabolic process through which cytosolic components are captured in the autophagosome and degraded in the lysosome. Autophagy plays two major roles: nutrient recycling under starvation or stress conditions and maintenance of cellular homeostasis by removing the damaged organelles or protein aggregates. In established cancer cells, autophagy-mediated nutrient recycling promotes tumor progression, whereas in normal/premalignant cells, autophagy suppresses tumor initiation by eliminating the oncogenic/harmful molecules. Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease that is refractory to most currently available treatment modalities, including immune checkpoint blockade and molecular-targeted therapy. One prominent feature of PDAC is its constitutively active and elevated autophagy-lysosome function, which enables PDAC to thrive in its nutrient-scarce tumor microenvironment. In addition to metabolic support, autophagy promotes PDAC progression in a metabolism-independent manner by conferring resistance to therapeutic treatment or facilitating immune evasion. Besides to cell-autonomous autophagy in cancer cells, host autophagy (autophagy in non-cancer cells) supports PDAC progression, further highlighting autophagy as a promising therapeutic target in PDAC. Based on a growing list of compelling preclinical evidence, there are numerous ongoing clinical trials targeting the autophagy-lysosome pathway in PDAC. Given the multifaceted and context-dependent roles of autophagy in both cancer cells and normal host cells, a deeper understanding of the mechanisms underlying the tumor-promoting roles of autophagy as well as of the consequences of autophagy inhibition is necessary for the development of autophagy inhibition-based therapies against PDAC.
... Other mutations in MM cells result in increased survival and proliferation. Activating mutations of NFkB, a transcription factor known for its anti-apoptotic activities, increases survival of MM cells ( Figure 1B) (32)(33)(34). BAFF is also produced by malignant B-cells like MM cells and acts as an autocrine factor on MM cell BCMA and TACI receptors (35). As previously discussed, activated TACI receptors increase NFkB expression (16). ...
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The role of the unfolded protein response (UPR) in plasma cells (PC) and their malignant multiple myeloma (MM) counterparts is a well described area of research. The importance of autophagy in these cells, as well as the interplay between autophagy and the UPR system, has also been well studied. In this review, we will discuss the relationship between these two cellular responses and how they can be utilized in MM to account for the high levels of monoclonal immunoglobulin (Ig) protein synthesis that is characteristic of this disease. Interactions between MM cells and the bone marrow (BM) microenvironment and how MM cells utilize the UPR/autophagy pathway for their survival. These interacting pathways form the foundation for the mechanism of action for bortezomib, a proteasome inhibitor used to modify the progression of MM, and the eventual drug resistance that MM cells develop. One important resistance pathway implicated in MM progression is caspase 10 which attenuates autophagy to maintain its prosurvival function and avoid cell death. We lay a groundwork for future research including 3D in vitro models for better disease monitoring and personalized treatment. We also highlight pathways involved in MM cell survival and drug resistance that could be used as new targets for effective treatment.
... In some cancer cells, autophagy inhibition also leads to increased NF-κB activation and resistance to anti-cancer drugs [11,61]. This could be due to the prolonged activation of the IKK subunits or the accumulation of p62 aggregates that were shown to promote NF-κB activation through various interactions [25,62] (Figure S4A). However, there are also cancer cells where autophagy impairment dampens NF-κB signaling [63], and therefore any therapeutic intervention in the direction of modulating autophagy should take into account the cancer cell type and background mutations. ...
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SQSTM1/p62 is a multitasking protein that functions as an autophagy receptor, but also as a signaling hub regulating diverse cellular pathways. p62 accumulation in mice with autophagy-deficient hepatocytes mediates liver damage and hepatocarcinogenesis through Nrf2 overactivation, yet the role of the p62-Keap1-Nrf2 axis in cell death and hepatocarcinogenesis in the absence of underlying autophagy defects is less clear. Here, we addressed the role of p62 and Nrf2 activation in a chronic liver disease model, namely mice with liver parenchymal cell-specific knockout of NEMO (NEMOLPC-KO), in which we demonstrate that they show no inherent autophagy impairment. Unexpectedly, systemic p62 ablation aggravated the phenotype and caused early postnatal lethality in NEMOLPC-KO mice. Expression of a p62 mutant (p62ΔEx2-5), which retains the ability to form aggregates and activate Nrf2 signaling, did not cause early lethality, but exacerbated hepatocarcinogenesis in these mice. Our immunohistological and molecular analyses showed that the increased tumor burden was only consistent with increased expression/stability of p62ΔEx2-5 driving Nrf2 hyperactivation, but not with other protumorigenic functions of p62, such as mTOR activation, cMYC upregulation or increased fibrosis. Surprisingly, forced activation of Nrf2 per se did not increase liver injury or tumor burden in NEMOLPC-KO mice, suggesting that autophagy impairment is a necessary prerequisite to unleash the Nrf2 oncogenic potential in mice with autophagy-competent hepatocytes.
... Liver-specific deletion of autophagy gene ATG7 was shown to cause p62 accumulation, translocation to the nucleus of Nrf2, overexpression of Nrf2-target genes, and carcinogenesis, which was prevented by p62 deficiency (117). Moreover, deficiency of p62 and Nrf2 was found to greatly suppress the progression of oncogenic RAS-driven NSCLC in mouse models (27,118). These lines of evidence show the oncogenic roles of p62 and Nrf2. ...
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Redox homeostasis is a lifelong pursuit of cancer cells. Depending on the context, reactive oxygen species (ROS) exert paradoxical effects on cancers; an appropriate concentration stimulates tumorigenesis and supports the progression of cancer cells, while an excessive concentration leads to cell death. The upregulated antioxidant system in cancer cells limits ROS to a tumor-promoting level. In cancers, redox regulation interacts with tumor initiation, proliferation, metastasis, programmed cell death, autophagy, metabolic reprogramming, the tumor microenvironment, therapies, and therapeutic resistance to facilitate cancer development. This review discusses redox control and the major hallmarks of cancer.
... However, p62 also can induce downstream signaling pathways, including NF-κB, mTORC1, and nuclear factor-erythroid factor 2-related factor 2 (NRF2), to influence inflammation, nutrient sensing, and the oxidative stress defense, which all may affect tumorigenesis [3,4]. Experimental studies using mouse models have shown that accumulation of p62 activates NF-κB and NRF2 signaling and accelerates the development of pancreatic cancer [1,2,5]. Although both NRF2 and NF-κB are elevated in human pancreatic cancer [1,[6][7][8], little is known about the role of p62 accumulation and associations with its downstream pathways in the development of human pancreatic cancer. ...
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Background Accumulation of the signal adaptor protein p62 has been demonstrated in many forms of cancer, including pancreatic ductal adenocarcinoma (PDAC). Although data from experimental studies suggest that p62 accumulation accelerates the development of PDAC, the association between p62 protein expression and survival in PDAC patients is unclear. Methods Thirty-three tumor specimens from PDAC patients treated by primary surgery were obtained. Immunohistochemical expression of p62, microtubule-associated protein 1A/1B-light chain 3 (LC3), and nuclear factor-erythroid factor 2-related factor 2 (NRF2) in tumor tissue was examined for associations with clinicopathological characteristics and disease-specific survival (DSS). Results There was no association between p62 expression and any of the clinicopathological variables. However, high p62 protein expression in tumor cells was significantly associated with shorter DSS (7 months vs. 29 months, p = 0.017). The hazard ratio for death in patients with high p62 protein expression in tumor cells was 2.88 (95% confidence interval: 1.17–7.11, p = 0.022). In multivariable analysis, high p62 expression was an independent prognostic factor for shorter DSS (p = 0.020) when follow up time was more than 5 years. LC3 and NRF2 staining was not associated with survival or other clinicopathological parameters. Conclusion Our results show that high p62 protein expression in tumor cells is associated with shorter survival following pancreatic tumor resection. This association supports a role for p62 as a prognostic marker in patients with PDAC treated by primary surgery.
... Thus, RAS-mediated cancers are addicted to autophagy for survival, and dysregulated autophagy in these cancer types is proportional to decreased cancer cell survival, accumulation of damaged mitochondria, and oxidative stress that may ultimately promote cell death (155; 25). Furthermore, p62/SQSTM1 deficiency also reduces tumorigenicity and increases ROS levels following RAS activation (145,156,157). Another study also states that autophagy inhibition by FIP200 (FAK familyinteracting protein of 200 kDa) deletion suppressed the breast cancer initiation in vivo driven by the polyoma virus middle T (PyMT) oncogene. ...
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Cancer formation is a highly regulated and complex process, largely dependent on its microenvironment. This complexity highlights the need for developing novel target-based therapies depending on cancer phenotype and genotype. Autophagy, a catabolic process, removes damaged and defective cellular materials through lysosomes. It is activated in response to stress conditions such as nutrient deprivation, hypoxia, and oxidative stress. Oxidative stress is induced by excess reactive oxygen species (ROS) that are multifaceted molecules that drive several pathophysiological conditions, including cancer. Moreover, autophagy also plays a dual role, initially inhibiting tumor formation but promoting tumor progression during advanced stages. Mounting evidence has suggested an intricate crosstalk between autophagy and ROS where they can either suppress cancer formation or promote disease etiology. This review highlights the regulatory roles of autophagy and ROS from tumor induction to metastasis. We also discuss the therapeutic strategies that have been devised so far to combat cancer. Based on the review, we finally present some gap areas that could be targeted and may provide a basis for cancer suppression.
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Tuberous sclerosis complex (TSC) is an autosomal dominant cancer predisposition disorder caused by heterozygous mutations in TSC1 or TSC2 genes and characterized by mTORC1 hyperactivation. TSC-associated tumors develop after loss of heterozygosity mutations and their treatment involves the use of mTORC1 inhibitors. We aimed to evaluate cellular processes regulated by mTORC1 in TSC cells with different mutations before tumor development. Flow cytometry analyses were performed to evaluate cell viability, cell cycle and autophagy in non-tumor primary TSC cells with different heterozygous mutations and in control cells without TSC mutations, before and after treatment with rapamycin (mTORC1 inhibitor). We did not observe differences in cell viability and cell cycle between the cell groups. However, autophagy was reduced in mutated cells. After rapamycin treatment, mutated cells showed a significant increase in the autophagy process (p=0.039). We did not observe differences between cells with distinct TSC mutations. Our main finding is the alteration of autophagy in non-tumor TSC cells. Previous studies in literature found autophagy alterations in tumor TSC cells or knock-out animal models. We showed that autophagy could be an important mechanism that leads to TSC tumor formation in the haploinsufficiency state. This result could guide future studies in this field.
Article
Macroautophagy/autophagy, a highly conserved lysosome-dependent degradation pathway, has been intensively studied in regulating cell metabolism by degradation of intracellular components. In this study, we link autophagy to RNA metabolism by uncovering a regulatory role of autophagy in ribosomal RNA (rRNA) synthesis. Autophagy-deficient cells exhibit much higher 47S precursor rRNA level, which is caused by the accumulation of SQSTM1/p62 (sequestosome 1) but not other autophagy receptors. Mechanistically, SQSTM1 accumulation potentiates the activation of MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) signaling and promotes the assembly of RNA polymerase I pre-initiation complex at ribosomal DNA (rDNA) promoters, which leads to an increase of 47S rRNA transcribed from rDNA. Functionally, autophagy deficiency promotes protein synthesis, cell growth and cell proliferation, both of which are dependent on SQSTM1 accumulation. Taken together, our findings suggest that autophagy deficiency is involved in RNA metabolism by activating rDNA transcription and provide novel mechanisms for the reprogramming of cell metabolism in autophagy-related diseases including multiple types of cancers.Abbreviations: 5-FUrd: 5-fluorouridine; AMPK: AMP-activated protein kinase; ATG: autophagy related; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; ChIP: chromatin immunoprecipitation; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK/ERK: mitogen-activated protein kinase; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; NFKB/NF-κB: nuclear factor kappa B; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; OPTN: optineurin; PIC: pre-initiation complex; POLR1: RNA polymerase I; POLR1A/RPA194: RNA polymerase I subunit A; POLR2A: RNA polymerase II subunit A; rDNA: ribosomal DNA; RPS6KB1/S6K1: ribosomal protein S6 kinase B1; rRNA: ribosomal RNA; RUBCN/Rubicon: rubicon autophagy regulator; SQSTM1/p62: sequestosome 1; STX17: syntaxin 17; SUnSET: surface sensing of translation; TAX1BP1: Tax1 binding protein 1; UBTF/UBF1: upstream binding transcription factor; WIPI2: WD repeat domain, phosphoinositide interacting 2; WT: wild-type.
Chapter
The word sounds a little bit quaint these days. However, we should bear in mind how BCR-ABL was discovered (see Table 9.1). The golden marker Ph in CML is indeed the place where the BCR-ABL oncogene is generated. Tumors in animals were known in the past, including Rous sarcoma in chicken discovered by Peyton Rous in 1911 that is transmissible from chicken to chicken by RS retrovirus, Yoshida sarcoma in albino rat discovered by Tomizo Yoshida in 1944 that was chemically induced (Rous, J Exp Med 13:397–411, 1911; Yoshida et al. Proc Imp Acad Tokyo 20:611–6, 1944). Howard Temin showed in 1958 that morphological transformation of chicken fibroblasts by RSV was quantitated in a focus-forming assay, which eventually led to the discovery of reverse transcriptase under his persistent hypothesis that the transformation is mediated by an RSV-dependent DNA intermediate, namely DNA provirus, stabilized in the transformed cells (Temin and Rubin, Virology 6:669–88, 1958). We should consider the fact that acute viral infection is a self-limited process for the propagation of the virus, but persistent transformation of the infected cells needs to have some stable alterations pertinent to the cells.
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Autophagy is an intracellular catabolic process that degrades cytoplasmic components for recycling in response to stressed conditions, such as nutrient deprivation. Dysregulation of autophagy is associated with various diseases, including cancer. Although autophagy plays dichotomous and context‐dependent roles in cancer, evidence has emerged that cancer cells exploit autophagy for metabolic adaptation. Autophagy is upregulated in many cancer types through tumor cell‐intrinsic proliferation demands and the hypoxic and nutrient‐limited tumor microenvironment (TME). Autophagy‐induced breakdown products then fuel into various metabolic pathways to supply tumor cells with energy and building blocks for biosynthesis and survival. This bidirectional regulation between autophagy and tumor constitutes a vicious cycle to potentiate tumor growth and therapy resistance. In addition, the pro‐tumor functions of autophagy are expanded to host, including cells in TME and distant organs. Thus, inhibition of autophagy or autophagy‐mediated metabolic reprogramming may be a promising strategy for anticancer therapy. Better understanding the metabolic rewiring mechanisms of autophagy for its pro‐tumor effects will provide insights into patient treatment.
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p62/Sequestosome‐1 (SQSTM1) is a selective autophagy receptor that recruits and delivers intracellular substrates for bulk clearance through the autophagy lysosomal pathway. Interestingly, p62 also serves as a signaling scaffold to participate in the regulation of multiple physiological processes, including oxidative stress response, metabolism, inflammation, and programmed cell death. Perturbation of p62 activity has been frequently found to associate with the pathogenesis of many liver diseases. p62 has been identified as a critical component of protein aggregates in the forms of Mallory‐Denk bodies (MDBs) or intracellular hyaline bodies (IHBs), which are known to be frequently detected in biopsy samples from alcoholic steatohepatitis (ASH), non‐alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC) patients. Importantly, abundance of these p62 inclusion bodies is increasingly recognized as a biomarker for NASH and HCC. Although the level of p62 bodies seems to predict the progression and prognosis of these liver diseases, understanding of the underlying mechanisms by which p62 regulates and contributes to the development and progression of these diseases remains incomplete. In this review, we will focus on the function and regulation of p62, and its pathophysiological roles in the liver, by critically reviewing the findings from pre‐clinical models that recapitulate the pathogenesis and manifestation of these liver diseases in human. In addition, we will also explore the suitability of p62 as a predictive biomarker and a potential therapeutic target for the treatment of liver diseases including NASH and HCC, as well as recent development of small molecule compounds for targeting the p62 signaling axis.
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Cardiovascular disease and cancer are the two leading causes of morbidity and mortality in the world. The emerging field of cardio-oncology has revealed that these seemingly disparate disease processes are intertwined, owing to the cardiovascular sequelae of anticancer therapies, shared risk factors that predispose individuals to both cardiovascular disease and cancer, as well the possible potentiation of cancer growth by cardiac dysfunction. As a result, interest has increased in understanding the fundamental biological mechanisms that are central to the relationship between cardiovascular disease and cancer. Metabolism, appropriate regulation of energy, energy substrate utilization, and macromolecular synthesis and breakdown are fundamental processes for cellular and organismal survival. In this Review, we explore the emerging data identifying metabolic dysregulation as an important theme in cardio-oncology. We discuss the growing recognition of metabolic reprogramming in cardiovascular disease and cancer and view the novel area of cardio-oncology through the lens of metabolism.
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p62/SQSTM1 is a selective autophagy receptor that drives ubiquitinated cargos towards autophagic degradation. This receptor is also a stress-induced scaffold protein that helps cells to cope with oxidative stress through activation of the Nrf2 pathway. Functional disorders of p62 are closely associated with multiple neurodegenerative diseases and cancers. The gene encoding the E3 ubiquitin ligase substrate-binding adapter SPOP is frequently mutated in prostate cancer (PCa), but the molecular mechanisms underlying how SPOP mutations contribute to PCa tumorigenesis remain poorly understood. Here, we report that cytoplasmic SPOP binds and induces the non-degradative ubiquitination of p62 at residue K420 within the UBA domain. This protein modification decreases p62 puncta formation, liquid phase condensation, dimerization, and ubiquitin-binding capacity, thereby suppressing p62-dependent autophagy. Moreover, we show that SPOP relieves p62-mediated Keap1 sequestration, which ultimately decreases Nrf2-mediated transcriptional activation of antioxidant genes. We further show that PCa-associated SPOP mutants lose the capacity to ubiquitinate p62 and instead promote autophagy and the redox response in a dominant-negative manner. Thus, our findings indicate oncogenic roles of autophagy and Nrf2 activation in the tumorigenesis of SPOP-mutated PCa.
Chapter
Cancer is the leading menace causing high morbidity and mortality in patients. Infections increase the risk of cancer progression and vice versa in patients. Pro-oncogenic infectious agents increase the high risk for malignancy in chronic infection harboring individuals through inducing cellular aberrations. The self-destructive cellular process known as autophagy has been documented as an important destructive and clearance mechanism during general infections. Autophagy signaling and cross-talks are activated in a coping response to starvation, stress, and hypoxia. The oncogenic etiological agents as well as tumor cells have evolved to regulate the autophagic machinery to evade the detrimental effects of autophagy to survive and proliferate. This chapter contains information about the dynamic facets of autophagy in infection-associated cancers.
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