p62: a versatile multitasker takes on cancer

Interferon-induced PARP14-mediated ADP-ribosylation in p62 bodies requires the ubiquitin-proteasome system

Biomolecular condensates are cellular compartments without enveloping membranes, enabling them to dynamically adjust their composition in response to environmental changes through post-translational modifications. Recent work has revealed that interferon-induced ADP-ribosylation (ADPr), which can be reversed by a SARS-CoV-2-encoded hydrolase, is enriched within a condensate. However, the identity of the condensate and the responsible host ADP-ribosyltransferase remain elusive. Here, we demonstrate that interferon induces ADPr through transcriptional activation of PARP14, requiring both the physical presence and catalytic activity of PARP14 for condensate formation. Interferon-induced ADPr colocalizes with PARP14 and its associated E3 ligase, DTX3L. These PARP14/ADPr condensates contain key components of p62 bodies-including the selective autophagy receptor p62, its binding partner NBR1 and the associated protein TAX1BP1, along with K48-linked and K63-linked polyubiquitin chains-but lack the autophagosome marker LC3B. Knockdown of p62 disrupts the formation of these ADPr condensates. Importantly, these structures are unaffected by autophagy inhibition, but depend on ubiquitination and proteasome activity. Taken together, these findings demonstrate that interferon triggers PARP14-mediated ADP-ribosylation in p62 bodies, which requires an active ubiquitin-proteasome system.

Role of ubiquitin-specific proteases in programmed cell death of breast cancer cells

Breast cancer (BC) is the most common malignant tumor and the leading cause of cancer-related deaths among women worldwide. Great progress has been recently achieved in controlling breast cancer; however, mortality from breast cancer remains a substantial challenge, and new treatment mechanisms are being actively sought. Programmed cell death (PCD) is associated with the progression and treatment of many types of human cancers. PCD can be divided into multiple pathways including autophagy, apoptosis, mitotic catastrophe, necroptosis, ferroptosis, pyroptosis, and anoikis. Ubiquitination is a post-translational modification process in which ubiquitin, a 76-amino acid protein, is coupled to the lysine residues of other proteins. Ubiquitination is involved in many physiological events and promotes cancer development and progression. This review elaborates the role of ubiquitin-specific protease (USP) in programmed cell death, which is common in breast cancer cells, and lays the foundation for tumor diagnosis and targeted therapy.

Acetylation: a new target for protein degradation in cancer

Acetylation is an increasing area of focus for cancer research as it is closely related to a variety of cellular processes through modulation of histone and non-histone proteins. However, broadly targeting acetylation threatens to yield nonselective toxic effects owing to the vital role of acetylation in cellular function. There is thus a pressing need to elucidate and characterize the specific cancer-relevant roles of acetylation for future therapeutic design. Acetylation-mediated protein homeostasis is an example of selective acetylation that affects a myriad of proteins as well as their correlated functions. We review recent examples of acetylation-mediated protein homeostasis that have emerged as key contributors to tumorigenesis, tumor proliferation, metastasis, and/or drug resistance, and we discuss their implications for future exploration of this intriguing phenomenon.

Silencing EPHB2 diminished the malignant biological properties of esophagus cancer cells by blocking autophagy and Wnt/β-catenin pathway

Eph receptor B2 (EPHB2) is overexpressed in some tumors and relevant to unfavorable outcomes of tumor patients. By searching Gene Expression Profiling Interactive Analysis and KM Plot websites, we discovered that EPHB2 was highly expressed in patients with esophageal cancer, leading to poor prognosis. However, the role and molecular mechanism of EPHB2 in esophagus cancer is unknown. Our study aims to unveil the underlying mechanism by which EPHB2 modulates the biological properties of esophagus cancer cells. After si-EPHB2 transfection, the malignant biological properties of esophagus cancer cells were determined by several biological experiments. IWP-4 was applied to block Wnt/β-catenin signaling pathway. The expressions of autophagy and Wnt/β-catenin signaling pathway relevant molecules were tested by western blot assay. An increased expression of EPHB2 was happened in esophagus cancer samples and loss of EPHB2 diminished esophagus cancer cells proliferation, migration, and invasion. Moreover, our data showed that depletion of EPHB2 blocked the autophagy and in-activated Wnt/β-catenin signaling pathway in esophagus cancer cells. While, IWP-4 treatment inhibited the autophagy and limited esophagus cancer cells proliferation, migration, and invasion. Moreover, EPHB2 knocked down strengthened the effect of IWP-4 treatment in regulating esophagus cancer cells proliferation, migration, and invasion. Finally, we illustrated that EPHB2 regulated the biological properties of esophagus cancer cells by modulating autophagy and Wnt/β-catenin signaling pathway. Our study illustrated that EPHB2 might be a worthwhile target considering for the treatment of esophagus cancer.

SERPINH1 modulates apoptosis by inhibiting P62 ubiquitination degradation to promote bone metastasis of prostate cancer

Prostate cancer (PCa) is one of the most prevalent urogenital malignancies. Bone metastasis from PCa reduces patient survival rates significantly. There currently exists no effective treatment for bone metastatic PCa, and the underlying mechanisms remain unclear. This study performed transcriptomic screening on PCa bone metastasis specimens and intersection analysis in public databases and identified SERPINH1 as a potential target for treatment. SERPINH1 was found to be upregulated in PCa bone metastases and with poor prognosis, high Gleason score, and advanced metastatic status. SERPINH1 induced PCa cells' bone metastasis in vivo, promoted their proliferation, and mitigated apoptosis. Mechanistically, SERPINH1 bound to P62, reducing TRIM21-mediated K63-linked ubiquitination degradation of P62 and promoting proliferation and resistance to apoptosis of PCa. This study suggests the regulation of ubiquitination degradation of P62 by SERPINH1 that promotes PCa bone metastasis and can be considered as a potential target for treatment of bone metastatic PCa.

Recombinant probiotic Lactococcus lactis delivering P62 mitigates moderate colitis in mice

Introduction and objective

p62 is a human multifunctional adaptor protein involved in key cellular processes such as tissue homeostasis, inflammation, and cancer. It acts as a negative regulator of inflammasome complexes. It may thus be considered a good candidate for therapeutic use in inflammatory bowel diseases (IBD), such as colitis. Probiotics, including recombinant probiotic strains producing or delivering therapeutic biomolecules to the host mucosal surfaces, could help prevent and mitigate chronic intestinal inflammation. The objective of the present study was to combine the intrinsic immunomodulatory properties of the probiotic Lactococcus lactis NCDO2118 with its ability to deliver health-promoting molecules to enhance its protective and preventive effects in the context of ulcerative colitis (UC).

Material and methods

This study was realized in vivo in which mice were supplemented with the recombinant strain. The intestinal barrier function was analyzed by monitoring permeability, secretory IgA total levels, mucin expression, and tight junction genes. Its integrity was evaluated by histological analyses. Regarding inflammation, colonic cytokine levels, myeloperoxidase (MPO), and expression of key genes were monitored. The intestinal microbiota composition was investigated using 16S rRNA Gene Sequencing.

Results and discussion

No protective effect of L. lactis NCDO2118 pExu:p62 was observed regarding mice clinical parameters compared to the L. lactis NCDO2118 pExu: empty. However, the recombinant strain, expressing p62, increased the goblet cell counts, upregulated Muc2 gene expression in the colon, and downregulated pro-inflammatory cytokines Tnf and Ifng when compared to L. lactis NCDO2118 pExu: empty and inflamed groups. This recombinant strain also decreased colonic MPO activity. No difference in the intestinal microbiota was observed between all treatments. Altogether, our results show that recombinant L. lactis NCDO2118 delivering p62 protein protected the intestinal mucosa and mitigated inflammatory damages caused by dextran sodium sulfate (DSS). We thus suggest that p62 may constitute part of a therapeutic approach targeting inflammation.

Enhancing wound healing and overcoming cisplatin resistance in ovarian cancer

Ovarian cancer (OC) poses significant oncological challenges, notably impaired wound healing in the context of cisplatin (DDP) resistance. This study investigates the role of miR-200b in OC, emphasizing its impact on wound healing processes through DNMT3A/TGF-β1 pathway. The primary aim was to explore how miR-200b regulates autophagy and its consequential effects on wound healing in OC, alongside its influence on cisplatin resistance. Utilizing DDP-sensitive (A2780) and resistant (A2780/DDP) OC cell lines, along with human fibroblast cultures, the study employed an array of in vitro techniques. These included cell transfection with miR-200b mimic or inhibitor, chromatin immunoprecipitation (ChIP), dual-luciferase reporter (DLR) assays, quantitative PCR, Western blotting, MTT and particularly, wound healing assays. The research highlighted the role of miR-200b in wound healing within OC. Inhibition of miR-200b in A2780 cells and its mimic in A2780/DDP cells affected cell viability, indicating the link with DDP resistance. Crucially, miR-200b mimic significantly delayed fibroblast-mediated wound closure in assays, underscoring its impact on wound healing. Bioinformatics analysis and subsequent DLR assays confirmed miR-200b's interaction with DNMT3A, affecting TGF-β1 expression, the key factor in wound repair. Further, ChIP, quantitative PCR and Western blot analyses validated the interaction and expression changes in DNMT3A and TGF-β1. The study demonstrated that miR-200b played a pivotal role in OC by modulating autophagy, which in turn significantly affected wound healing through the DNMT3A/TGF-β1 pathway.

UDP-glucose dehydrogenase supports autophagy-deficient PDAC growth via increasing hyaluronic acid biosynthesis

Autophagy is an essential degradation and recycling process that maintains cellular homeostasis during stress or nutrient deprivation. However, certain types of tumors such as pancreatic cancers can circumvent autophagy inhibition to sustain growth. The mechanism that autophagy-deficient pancreatic ductal adenocarcinoma (PDAC) uses to grow under nutrient deprivation is poorly understood. Our data show that nutrient deprivation in PDAC results in UDP-glucose dehydrogenase (UGDH) degradation, which is dependent on autophagic cargo receptor sequestosome 1 (p62). Moreover, we demonstrate that accumulated UGDH is indispensable for autophagy-deficient PDAC cells proliferation by promoting hyaluronic acid (HA) synthesis upon energy deprivation. Using an orthotopic mouse model of PDAC, we find that inhibition of HA synthesis by targeting UGDH in PDAC reduces tumor weight. Thus, the combined inhibition of HA and autophagy might be an attractive strategy for PDAC treatment.

Clinical efficacy of plasmid encoding p62/SQSTM1 (Elenagen) in combination with gemcitabine in patients with platinum-resistant ovarian cancer: a randomized controlled trial

Background

The purpose of this trial is to evaluate the safety and efficacy of ELENAGEN, a novel anticancer therapeutic DNA plasmid encoding p62/SQSTM1 protein, as an adjuvant to chemotherapy with gemcitabine (GEM) in patients with advanced platinum-resistant ovarian cancer.

Methods

This open-label prospective randomized study with two arms. GEM (1000 mg/m2) on days 1 and 8 every 3 weeks was administered in both arms: in the Chemo arm (n = 20), GEM was the only treatment, and in the ELENAGEN arm (n = 20), GEM was supplemented with ELENAGEN (2.5 mg i.m. weekly). The primary endpoint was progression-free survival (PFS), and the secondary endpoint was safety. Antitumor activity was assessed by RECIST 1.1, and criteria safety was assessed according to NCI CTCAE version 5.0.

Results

According to the cutoff data, the median follow-up was 13.8 months. There were no serious adverse events related to ELENAGEN treatment. The median PFS was 2.8 and 7.2 months in the Chemo and ELENAGEN arms, respectively (p Log-Rank = 0.03). Notably, at the time of cutoff, 9 patients (45%) in the ELENAGEN arm did not progress, with the longest PFS recorded thus far being 24 months. Subgroup analysis of patients in both arms demonstrated high efficacy of ELENAGEN in patients with worse prognostic factors: high pretreatment levels of CA125 and progression after platinum-free interval <3 months.

Conclusions

The addition of ELENAGEN to gemcitabine is effective in patients with platinum-resistant ovarian cancer, including those with a worse prognosis.

Clinical trial registration

https://www.clinicaltrials.gov/study/NCT05979298, identifier NCT05979298, 2023-08-07.

Autophagy regulates tumor growth and metastasis

The role of autophagy in tumorigenesis and tumor metastasis remains poorly understood. Here we show that inhibition of autophagy stabilizes the transcription factor Twist1 through Sequestosome-1 (SQSTM1, also known as p62) and thus increases cell proliferation, migration, and epithelial-mesenchymal transition (EMT) in tumor development and metastasis. Inhibition of autophagy or p62 overexpression blocks Twist1 protein degradation in the proteasomes, while p62 inhibition enhances it. SQSTM1/p62 interacts with Twist1 via the UBA domain of p62, in a Twist1-ubiquitination-dependent manner. Lysine 175 in Twist1 is critical for Twist1 ubiquitination, degradation, and SQSTM1/p62 interaction. For squamous skin cancer and melanoma cells that express Twist1, SQSTM1/p62 increases tumor growth and metastasis in mice. Together, our results identified Twist1 as a key downstream protein for autophagy and suggest a critical role of the autophagy/p62/Twist1 axis in cancer development and metastasis.

Nickel nanoparticles induce autophagy and apoptosis via HIF-1α/mTOR signaling in human bronchial epithelial cells

With the rapid development of nanotechnology, the potential adverse health effects of nanoparticles have been caught more attention and become global concerns. However, the underlying mechanisms in metal nanoparticle-induced toxic effects are still largely obscure. In this study, we investigated whether exposure to nickel nanoparticles (Nano-Ni) and titanium dioxide nanoparticles (Nano-TiO2) would alter autophagy and apoptosis levels in normal human bronchial epithelial BEAS-2B cells and the underlying mechanisms involved in this process. Our results showed that the expressions of autophagy- and apoptosis-associated proteins were dysregulated in cells exposed to Nano-Ni. However, exposure to the same doses of Nano-TiO2 had no significant effects on these proteins. In addition, exposure to Nano-Ni, but not Nano-TiO2, led to nuclear accumulation of HIF-1α and decreased phosphorylation of mTOR in BEAS-2B cells. Inhibition of HIF-1α by CAY10585 abolished Nano-Ni-induced decreased phosphorylation of mTOR, while activation of mTOR by MHY1485 did not affect Nano-Ni-induced nuclear accumulation of HIF-1α. Furthermore, both HIF-1α inhibition and mTOR activation abolished Nano-Ni-induced autophagy but enhanced Nano-Ni-induced apoptosis. Blockage of autophagic flux by Bafilomycin A1 exacerbated Nano-Ni-induced apoptosis, while activation of autophagy by Rapamycin effectively rescued Nano-Ni-induced apoptosis. In conclusion, our results demonstrated that Nano-Ni exposure caused increased levels of autophagy and apoptosis via the HIF-1α/mTOR signaling axis. Nano-Ni-induced autophagy has a protective role against Nano-Ni-induced apoptosis. These findings provide us with further insight into Nano-Ni-induced toxicity.

The emerging potential role of p62 in cancer treatment by regulating metabolism

p62 is an important multifunctional adaptor protein participating in autophagy and many other activities. Many studies have revealed that p62 is highly expressed in multiple cancers and decreasing its level can effectively lower the proliferation ability of cancer cells. Moreover, much research has highlighted the significant role of the regulation of cancer cell metabolism in helping to treat tumors. Recent reports demonstrate that p62 could regulate cancer cell metabolism through various mechanisms. However, the relationship between p62 and cancer cell metabolism as well as the related mechanisms has not been fully elucidated. In this review, we describe glucose, glutamine, and fatty acid metabolism in tumor cells and some signaling pathways that can regulate cancer metabolism and are mediated by p62.

Oxidized low-density lipoprotein regulates macrophage polarization in atherosclerosis

Atherosclerosis is the pathological basis of acute cardiovascular and cerebrovascular diseases. Oxidized LDL has been recognized as a major atherogenic factor in the vessel wall for decades. A growing body of evidence suggests that oxidized LDL modulates macrophage phenotypes in atherosclerosis. This article reviews the research progress on the regulation of macrophage polarization by oxidized LDL. Mechanistically, oxidized LDL induces macrophage polarization via cell signaling, metabolic reprogramming, epigenetic regulation, and intercellular regulation. This review is expected to provide new targets for the treatment of atherosclerosis.

PERK prevents rhodopsin degradation during retinitis pigmentosa by inhibiting IRE1-induced autophagy

Chronic endoplasmic reticulum (ER) stress is the underlying cause of many degenerative diseases, including autosomal dominant retinitis pigmentosa (adRP). In adRP, mutant rhodopsins accumulate and cause ER stress. This destabilizes wild-type rhodopsin and triggers photoreceptor cell degeneration. To reveal the mechanisms by which these mutant rhodopsins exert their dominant-negative effects, we established an in vivo fluorescence reporter system to monitor mutant and wild-type rhodopsin in Drosophila. By performing a genome-wide genetic screen, we found that PERK signaling plays a key role in maintaining rhodopsin homeostasis by attenuating IRE1 activities. Degradation of wild-type rhodopsin is mediated by selective autophagy of ER, which is induced by uncontrolled IRE1/XBP1 signaling and insufficient proteasome activities. Moreover, upregulation of PERK signaling prevents autophagy and suppresses retinal degeneration in the adRP model. These findings establish a pathological role for autophagy in this neurodegenerative condition and indicate that promoting PERK activity could be used to treat ER stress-related neuropathies, including adRP.

Delineating the twin role of autophagy in lung cancer

Autophagy represents an intracellular defense mechanism equipped within each eukaryotic cells to enable them to cope with variety of physical, chemical, and biological stresses. This mechanism helps to restore the homeostasis and preserve the cellular integrity and function of the cells. In these conditions, such as hypoxia, nutrient deprivation, inhibition of protein synthesis or microbial attack, the process of autophagy is upregulated to maintain cellular homeostasis. The role of autophagy in cancer is an intriguing topic which needs further exploration. This process of autophagy has been many times referred as a double-edged sword in the process of tumorigenesis. In the initial stages, it may act as a tumor suppressor and enable to quench the damaged organelles and harmful molecules generated. In more advanced stages, autophagy has been shown to act as a tumor-promoting system as it may help the cancer cells to cope better with stressful microenvironments. Besides this, autophagy has been associated with development of resistance to anticancer drugs as well as promoting the immune evasion in cancer cells, representing a serious obstacle in cancer treatment and its outcome. Also, autophagy is associated with hallmarks of cancer that may lead to activation of invasion and metastasis. The information on this twin role needs further exploration and deeper understanding of the pathways involved. In this review, we discuss the various aspects of autophagy during tumor development, from early to late stages of tumor growth. Both the protective role of autophagy in preventing tumor growth and the underlying mechanisms adopted with evidence from past studies have been detailed. Further, the role of autophagy in conferring resistance to distinct lung cancer treatment and immune shielding properties has also been discussed. This is essential for further improving on treatment outcome and success rates.

Autoimmunity and Carcinogenesis: Their Relationship under the Umbrella of Autophagy

The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease's origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a "double-edged sword" in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.

Methylmercury drives lipid droplet formation and adipokine expression during the late stages of adipocyte differentiation in 3T3-L1 cells

Chronic exposure to methylmercury (MeHg) is positively associated with obesity and metabolic syndromes. However, the effect of MeHg on adipogenesis has not been thoroughly investigated. This study investigated the effects of continuous exposure to 0.5 µM MeHg on adipocyte differentiation in 3T3-L1 cells. Oil Red O staining and triglycerides (TG) assays demonstrated that MeHg enhanced the TG content in 3T3-L1 cells. MeHg enhanced the mRNA and protein expression of adipocyte differentiation markers including peroxisome proliferator-activated receptor γ, adiponectin, and fatty acid-binding protein, and their expression levels were prominent during the late stages (days 6-8) after the induction of differentiation. In addition, 0.5 µM MeHg promoted the expression of autophagy-related genes, including light chain 3 B-II and p62, after induction of differentiation. Treatment of 3T3-L1 cells with chloroquine (CQ), an autophagy inhibitor, during the early stages (days 0-2) after induction of differentiation inhibited cellular lipid accumulation in the presence of 0.5 µM MeHg. However, treatment with CQ during the late stages (days 6-8) had little effect on the MeHg-induced increase in TG content and the expression of adipocyte differentiation markers. Although the underlying mechanisms in the late stages remain to be completely elucidated, but the present data suggest that autophagy and other mechanisms play critical roles in adipogenesis during MeHg-induced differentiation. Collectively, our results suggest that continuous exposure to MeHg induces TG accumulation and expression of genes related to adipogenesis, especially during the late stages of 3T3-L1 differentiation, which may contribute to an improved understanding of MeHg-induced adipogenesis.

Cytotoxicity and Autophagy Induced by Ivermectin via AMPK/mTOR Signaling Pathway in RAW264.7 Cells

The widespread and excessive use of ivermectin (IVM) will not only cause serious environmental pollution, but will also affect metabolism of humans and other mammals that are exposed. IVM has the characteristics of being widely distributed and slowly metabolized, which will cause potential toxicity to the body. We focused on the metabolic pathway and mechanism of toxicity of IVM on RAW264.7 cells. Colony formation and LDH detection assay showed that IVM significantly inhibited the proliferation of and induced cytotoxicity in RAW264.7 cells. Intracellular biochemical analysis using Western blotting assay showed that LC3-B and Beclin-1 were upregulated and p62 was down-regulated. The combination of confocal fluorescence, calcein-AM/CoCl₂, and fluorescence probe results showed that IVM could induce the opening of the mitochondrial membrane permeability transition pore, reduce mitochondrial content, and increase lysosome content. In addition, we focused on induction of IVM in the autophagy signal pathway. The Western blotting results showed that IVM increased expression of p-AMPK and decreased p-mTOR and p-S6K expression in protein levels, indicating that IVM activated the AMPK/mTOR signaling pathway. Therefore, IVM may inhibit cell proliferation by inducing cell cycle arrest and autophagy.

Impaired hepatic autophagy exacerbates hepatotoxin induced liver injury

Hepatotoxins activate the hepatic survival pathway, but it is unclear whether impaired survival pathways contribute to liver injury caused by hepatotoxins. We investigated the role of hepatic autophagy, a cellular survival pathway, in cholestatic liver injury driven by a hepatotoxin. Here we demonstrate that hepatotoxin contained DDC diet impaired autophagic flux, resulting in the accumulation of p62-Ub-intrahyaline bodies (IHBs) but not the Mallory Denk-Bodies (MDBs). An impaired autophagic flux was associated with a deregulated hepatic protein-chaperonin system and significant decline in Rab family proteins. Additionally, p62-Ub-IHB accumulation activated the NRF2 pathway rather than the proteostasis-related ER stress signaling pathway and suppressed the FXR nuclear receptor. Moreover, we demonstrate that heterozygous deletion of Atg7, a key autophagy gene, aggravated the IHB accumulation and cholestatic liver injury. Conclusion: Impaired autophagy exacerbates hepatotoxin-induced cholestatic liver injury. The promotion of autophagy may represent a new therapeutic approach for hepatotoxin-induced liver damage.

Autophagy: A challengeable paradox in cancer treatment

OBJECTIVE

Autophagy is an intracellular degradation pathway conserved in all eukaryotes from yeast to humans. This process plays a quality-control role by destroying harmful cellular components under normal conditions, maintaining cell survival, and establishing cellular adaptation under stressful conditions. Hence, there are various studies indicating dysfunctional autophagy as a factor involved in the development and progression of various human diseases, including cancer. In addition, the importance of autophagy in the development of cancer has been highlighted by paradoxical roles, as a cytoprotective and cytotoxic mechanism. Despite extensive research in the field of cancer, there are many questions and challenges about the roles and effects suggested for autophagy in cancer treatment. The aim of this study was to provide an overview of the paradoxical roles of autophagy in different tumors and related cancer treatment options.

METHODS

In this study, to find articles, a search was made in PubMed and Google scholar databases with the keywords Autophagy, Autophagy in Cancer Management, and Drug Design.

RESULTS

According to the investigation, some studies suggest that several advanced cancers are dependent on autophagy for cell survival, so when cancer cells are exposed to therapy, autophagy is induced and suppresses the anti-cancer effects of therapeutic agents and also results in cell resistance. However, enhanced autophagy from using anti-cancer drugs causes autophagy-mediated cell death in several cancers. Because autophagy also plays roles in both tumor suppression and promotion further research is needed to determine the precise mechanism of this process in cancer treatment.

CONCLUSION

We concluded in this article, autophagy manipulation may either promote or hinder the growth and development of cancer according to the origin of the cancer cells, the type of cancer, and the behavior of the cancer cells exposed to treatment. Thus, before starting treatment it is necessary to determine the basal levels of autophagy in various cancers.

p62/SQSTM1 indirectly mediates remote multipotent mesenchymal cells and rescues bone loss and bone marrow integrity in ovariectomized rats

Intramuscular administration of p62/SQSTM1 (sequestosome1)-encoding plasmid demonstrated an anticancer effect in rodent models and dogs as well as a high safety profile and the first evidence of clinical benefits in humans. Also, an anti-inflammatory effect of the plasmid was reported in several rodent disease models. Yet, the mechanisms of action for the p62 plasmid remain unknown. Here, we tested a hypothesis that the p62-plasmid can act through the modulation of bone marrow multipotent mesenchymal cells (MSCs). We demonstrated that a p62 plasmid can affect MSCs indirectly by stimulating p62-transfected cells to secrete an active ingredient(s) sensed by untransfected MSCs. When we transfected MSCs with the p62-plasmid, collected their supernatant, and added it to an untransfected MSCs culture, it switched the differentiation state and prompt osteogenic responses of the untransfected MSCs. According to an accepted viewpoint, ovariectomy leads to bone pathology via dysregulation of MSCs, and restoring the MSC homeostasis would restore ovariectomy-induced bone damage. To validate our in vitro observations in a clinically relevant in vivo model, we administered the p62 plasmid to ovariectomized rats. It partially reversed bone loss and notably reduced adipogenesis with concurrent reestablishing of the MSC subpopulation pool within the bone marrow. Overall, our study suggests that remote modulation of progenitor MSCs via administering a p62-encoding plasmid may constitute a mechanism for its previously reported effects and presents a feasible disease-preventing and/or therapeutic strategy.

High p62 expression suppresses the NLRP1 inflammasome and increases stress resistance in cutaneous SCC cells

NLRP1 is the primary inflammasome sensor in human keratinocytes. Sensing of UVB radiation by NLRP1 is believed to underlie the induction of sunburn. Although constitutive NLRP1 activation causes skin inflammation and predisposes patients to the development of cutaneous SCCs, the NLRP1 pathway is suppressed in established SCCs. Here, we identified high levels of the autophagy receptor p62 in SCC cells lines and SCC tumors. Increased NF-κB activity in SCC cells causes p62 up-regulation. Suppression of p62 expression rescues UVB-induced NLRP1 inflammasome activation in early-stage SCC cells. p62 expression protects SCC cells from cytotoxic drugs, whereas NLRP1 sensitizes them. In summary, we identify p62 as a novel negative regulator of the NLRP1 inflammasome in human cutaneous SCC cells, in which suppression of NLRP1 by increased levels of p62 supports stress resistance of skin cancer cells.

Recent advances in esophageal squamous cell precancerous conditions: A review

Esophageal squamous cell carcinoma (ESCC) is a common cancer in many developing countries in Asia and Africa, with a 5-year survival rate of approximately 20%. Most cases are diagnosed at an advanced age when there is no effective treatment strategy. Esophageal precancerous conditions have a much better prognosis, with a 5-year survival rate of over 90% by endoscopic diagnosis and treatment. Nevertheless, limitations, contraindications, and lymph node metastasis incompetency of endoscopy. Thus, the diagnosis and treatment of esophageal precancerous lesions remain a significant challenge. Biomarker investigations provide opportunities for target detection and therapy. Additionally, drug development is ongoing. Changes in lifestyle habits, such as diet balance, smoking and alcohol cessation, are beneficial for the prognosis of esophageal precancerous lesions. Collectively, multiple and sequential diagnoses and treatments are essential for curing esophageal precancerous lesions and reducing the incidence and mortality of ESCC.

Transforming growth factor-β in tumour development

Transforming growth factor-β (TGFβ) is a ubiquitous cytokine essential for embryonic development and postnatal tissue homeostasis. TGFβ signalling regulates several biological processes including cell growth, proliferation, apoptosis, immune function, and tissue repair following injury. Aberrant TGFβ signalling has been implicated in tumour progression and metastasis. Tumour cells, in conjunction with their microenvironment, may augment tumourigenesis using TGFβ to induce epithelial-mesenchymal transition, angiogenesis, lymphangiogenesis, immune suppression, and autophagy. Therapies that target TGFβ synthesis, TGFβ-TGFβ receptor complexes or TGFβ receptor kinase activity have proven successful in tissue culture and in animal models, yet, due to limited understanding of TGFβ biology, the outcomes of clinical trials are poor. Here, we review TGFβ signalling pathways, the biology of TGFβ during tumourigenesis, and how protein quality control pathways contribute to the tumour-promoting outcomes of TGFβ signalling.

Immunohistochemical Expression of p62 in Feline Mammary Carcinoma and Non-Neoplastic Mammary Tissue

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 seven cases (18.4%) had a low expression. The grade of the differentiation of the carcinoma was not correlated with the p62 expression. This study represents the first approach in feline oncology that correlates p62 expression in feline mammary carcinoma. Our results, although preliminary, are similar to the results of human breast cancer, therefore, also in the cat, p62 could be considered a possible oncotarget.

Bioinformatics-Driven Identification of p62 as A Crucial Oncogene in Liver Cancer

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.

Emerging roles of mitotic autophagy

Lysosomes exert pleiotropic functions to maintain cellular homeostasis and degrade autophagy cargo. Despite the great advances that have boosted our understanding of autophagy and lysosomes in both physiology and pathology, their function in mitosis is still controversial. During mitosis, most organelles are reshaped or repurposed to allow the correct distribution of chromosomes. Mitotic entry is accompanied by a reduction in sites of autophagy initiation, supporting the idea of an inhibition of autophagy to protect the genetic material against harmful degradation. However, there is accumulating evidence revealing the requirement of selective autophagy and functional lysosomes for a faithful chromosome segregation. Degradation is the most-studied lysosomal activity, but recently described alternative functions that operate in mitosis highlight the lysosomes as guardians of mitotic progression. Because the involvement of autophagy in mitosis remains controversial, it is important to consider the specific contribution of signalling cascades, the functions of autophagic proteins and the multiple roles of lysosomes, as three entangled, but independent, factors controlling genomic stability. In this Review, we discuss the latest advances in this area and highlight the therapeutic potential of targeting autophagy for drug development.

P62/SQSTM1 enhances osteogenesis and attenuates inflammatory signals in bone marrow microenvironment

Bone marrow-derived mesenchymal/stromal stem cells (MSCs) became a major focus of research since the anti-inflammatory features and the osteogenic commitment of these cells can prevent the inflamm-aging and various form of osteopenia in humans and animals. We previously showed that p62/SQSTM1 plasmid can prompt release of anti-inflammatory cytokines/chemokines by MSC when injected in adult mice. Furthermore, it can enhance osteoblastogenesis at the expense of adipogenesis and ameliorate bone density and bone remodeling. On the other hand, absence of p62 partially exhausted MSC pool caused expansion of fat cells within bone marrow and pro-inflammatory mediator's accumulation. Given the critical function of p62 as molecular hub of MSC dynamics, here, using MSCs from p62 knockout adult mice, we investigated the effect of this protein on MSC survival and bone-forming molecule cascades. We found that the main osteogenic routes are impaired in absence of p62. In particular, lack of p62 can suppress Smads activation, and Osterix and CREBs expression, thus significantly modifying the schedule of MSCs differentiation. MSCs obtained from p62-/- mice have also demonstrate an amplified NFκB/ Smad1/5/8 colocalization along with NFκB activation in the nucleus, which precludes Smads binding to target promoters. Considering the "teamwork" of TGFβ, PTH and BMP2 on MSC homeostatic behavior, we consider that p62 exerts an essential role as a hub protein. Lastly, ex vivo pulsing p62-deficient MSCs, which then will be administered to a patient as a cell therapy, may be considered as a treatment for bone and bone marrow disorders.

The Relationship of Redox With Hallmarks of Cancer: The Importance of Homeostasis and Context

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.

Nobiletin as an inducer of programmed cell death in cancer: a review

Cancer resistance to therapy is a big issue in cancer therapy. Tumours may develop some mechanisms to reduce the induction of cell death, thus stimulating tumour growth. Cancer cells may show a low expression and activity of tumour suppressor genes and a low response to anti-tumour immunity. These mutations can increase the resistance of cancer cells to programmed cell death mechanisms such as apoptosis, ferroptosis, pyroptosis, autophagic cell death, and some others. The upregulation of some mediators and transcription factors such as Akt, nuclear factor of κB, signal transducer and activator of transcription 3, Bcl-2, and others can inhibit cell death in cancer cells. Using adjuvants to induce the killing of cancer cells is an interesting strategy in cancer therapy. Nobiletin (NOB) is a herbal-derived agent with fascinating anti-cancer properties. It has been shown to induce the generation of endogenous ROS by cancer cells, leading to damage to critical macromolecules and finally cell death. NOB may induce the activity of p53 and pro-apoptosis mediators, and also inhibit the expression and nuclear translocation of anti-apoptosis mediators. In addition, NOB may induce cancer cell killing by modulating other mechanisms that are involved in programmed cell death mechanisms. This review aims to discuss the cellular and molecular mechanisms of the programmed cell death in cancer by NOB via modulating different types of cell death in cancer.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

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.

AKR1C1 connects autophagy and oxidative stress by interacting with SQSTM1 in a catalytic-independent manner

Targeting autophagy might be a promising anticancer strategy; however, the dual roles of autophagy in cancer development and malignancy remain unclear. NSCLC (non-small cell lung cancer) cells harbour high levels of SQSTM1 (sequestosome 1), the autophagy receptor that is critical for the dual roles of autophagy. Therefore, mechanistic insights into SQSTM1 modulation may point towards better approaches to treat NSCLC. Herein, we used multiple autophagy flux models and autophagy readouts to show that aldo-keto reductase family 1 member C1 (AKR1C1), which is highly expressed in NSCLC, promotes autophagy by directly binding to SQSTM1 in a catalytic-independent manner. This interaction may be strengthened by reactive oxygen species (ROS), important autophagy inducers. Further mechanistic research demonstrated that AKR1C1 interacts with SQSTM1 to augment SQSTM1 oligomerization, contributing to the SQSTM1 affinity for binding cargo. Collectively, our data reveal a catalytic-independent role of AKR1C1 for interacting with SQSTM1 and promoting autophagy. All these findings not only reveal a novel functional role of AKR1C1 in the autophagy process but also indicate that modulation of the AKR1C1-SQSTM1 interaction may be a new strategy for targeting autophagy.

A perspective on the role of autophagy in cancer

Autophagy refers to a ubiquitous set of catabolic pathways required to achieve proper cellular homeostasis. Aberrant autophagy has been implicated in a multitude of diseases including cancer. In this review, we highlight pioneering and groundbreaking research that centers on delineating the role of autophagy in cancer initiation, proliferation and metastasis. First, we discuss the autophagy-related (ATG) proteins and their respective roles in the de novo formation of autophagosomes and the subsequent delivery of cargo to the lysosome for recycling. Next, we touch upon the history of cancer research that centers upon ATG proteins and regulatory mechanisms that control an appropriate autophagic response and how these are altered in the diseased state. Then, we discuss the various discoveries that led to the idea of autophagy as a double-edged sword when it comes to cancer therapy. This review also briefly narrates how different types of autophagy-selective macroautophagy and chaperone-mediated autophagy, have been linked to different cancers. Overall, these studies build upon a steadfast trajectory that aims to solve the monumentally daunting challenge of finding a cure for many types of cancer by modulating autophagy either through inhibition or induction.

Autophagy: The Potential Link between SARS-CoV-2 and Cancer

Simple Summary

Coronavirus disease 2019 (COVID-19) has led to a global crisis. With the increasing number of individuals infected worldwide, the long-term consequences of this disease have become an active area of research. The constellation of symptoms COVID-19 survivors suffer from is commonly referred to as post-acute COVID-19 syndrome in the scientific literature. In this paper, we discuss the potential long-term complications of this infection resulting from the persistence of the viral particles in body tissues interacting with host cells’ autophagy machinery in the context of the development of cancer, cancer progression and metastasis, as well as response to treatment. We also propose a structured framework for future studies to investigate the potential impact of COVID-19 infection on cancer.

Abstract

COVID-19 infection survivors suffer from a constellation of symptoms referred to as post-acute COVID-19 syndrome. However, in the wake of recent evidence highlighting the long-term persistence of SARS-CoV-2 antigens in tissues and emerging information regarding the interaction between SARS-CoV-2 proteins and various components of the host cell macroautophagy/autophagy machinery, the unforeseen long-term consequences of this infection, such as increased risk of malignancies, should be explored. Although SARS-CoV-2 is not considered an oncogenic virus, the possibility of increased risk of cancer among COVID-19 survivors cannot be ruled out. Herein, we provide an overview of the possible mechanisms leading to cancer development, particularly obesity-related cancers (e.g., colorectal cancer), resulting from defects in autophagy and the blockade of the autophagic flux, and also immune escape in COVID-19 survivors. We also highlight the potential long-term implications of COVID-19 infection in the prognosis of patients with cancer and their response to different cancer treatments. Finally, we consider future directions for further investigations on this matter.

The Ubiquitin Sensor and Adaptor Protein p62 Mediates Signal Transduction of a Viral Oncogenic Pathway

The Epstein-Barr virus (EBV) protein LMP1 serves as a paradigm that engages complicated ubiquitination-mediated mechanisms to activate multiple transcription factors. p62 is a ubiquitin sensor and a signal-transducing adaptor that has multiple functions in diverse contexts. However, the interaction between p62 and oncogenic viruses is poorly understood. We recently reported a crucial role for p62 in oncovirus-mediated oxidative stress by acting as a selective autophagy receptor. In this following pursuit, we further discovered that p62 is upregulated in EBV type 3 compared to type 1 latency, with a significant contribution from NF-κB and AP1 activities downstream of LMP1 signaling. In turn, p62 participates in LMP1 signal transduction through its interaction with TRAF6, promoting TRAF6 ubiquitination and activation. As expected, short hairpin RNA (shRNA)-mediated knockdown (KD) of p62 transcripts reduces LMP1-TRAF6 interaction and TRAF6 ubiquitination, as well as p65 nuclear translocation, which was assessed by Amnis imaging flow cytometry. Strikingly, LMP1-stimulated NF-κB, AP1, and Akt activities are all markedly reduced in p62-/- mouse embryo fibroblasts (MEFs) and in EBV-negative Burkitt's lymphoma (BL) cell lines with CRISPR-mediated knockout (KO) of the p62-encoding gene. However, EBV-positive BL cell lines (type 3 latency) with CRISPR-mediated KO of the p62-encoding gene failed to survive. In consequence, shRNA-mediated p62 KD impairs the ability of LMP1 to regulate its target gene expression, promotes etoposide-induced apoptosis, and reduces the proliferation of lymphoblastic cell lines (LCLs). These important findings have revealed a previously unrecognized novel role for p62 in EBV latency and oncogenesis, which advances our understanding of the mechanism underlying virus-mediated oncogenesis. IMPORTANCE 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. In this study, we provide evidence that p62 is upregulated in EBV type 3 latency and, in turn, p62 mediates LMP1 signal transduction to NF-κB, AP1, and Akt by promoting TRAF6 ubiquitination and activation. In consequence, p62 deficiency negatively regulates LMP1-mediated gene expression, promotes etoposide-induced apoptosis, and reduces the proliferation of LCLs. These important findings identified p62 as a novel signaling component of the key viral oncogenic signaling pathway.

Canonical and Non-canonical TGFβ Signaling Activate Autophagy in an ULK1-Dependent Manner

The mechanism(s) in which transforming growth factor beta 1 (TGFβ) modulates autophagy in cancer remain unclear. Here, we characterized the TGFβ signaling pathways that induce autophagy in non-small cell lung cancer cells, using cells lines stably expressing GFP-LC3-RFP-LC3ΔG constructs that measure autophagic flux. We demonstrated that TGFβ1 increases Unc 51-like kinase 1 (ULK1) protein levels, 5' adenosine monophosphate-activated protein kinase (AMPK)-dependent ULK1 phosphorylation at serine (S) 555 and ULK1 complex formation but decreases mechanistic target of rapamycin (mTOR) activity on ULK1. Further analysis revealed that the canonical Smad4 pathway and the non-canonical TGFβ activated kinase 1/tumor necrosis factor receptor-associated factor 6/P38 mitogen activated protein kinase (TAK1-TRAF6-P38 MAPK) pathway are important for TGFβ1-induced autophagy. The TAK1-TRAF6-P38 MAPK pathway was essential for downregulating mTOR S2448 phosphorylation, ULK1 S555 phosphorylation and autophagosome formation. Furthermore, although siRNA-mediated Smad4 silencing did not alter mTOR-dependent ULK1 S757 phosphorylation, it did reduce AMPK-dependent ULK1 S555 phosphorylation and autophagosome formation. Additionally, Smad4 silencing and inhibiting the TAK1-TRAF6-P38 MAPK pathway decreased autophagosome-lysosome co-localization in the presence of TGFβ. Our results suggest that the Smad4 and TAK1-TRAF6-P38 MAPK signaling pathways are essential for TGFβ-induced autophagy and provide specific targets for the inhibition of TGFβ in tumor cells that utilize autophagy in their epithelial-mesenchymal transition program.

Single-domain antibody screening by isPLA-seq

This study describes a high-sensitive, high-throughput single-domain antibody library screening approach, which is applicable for any given interested protein at single-cell resolution by isPLA-seq.

Single-domain antibody (sdAb) holds the promising strategies for diverse research and translational applications. Here, we describe a method for the adaptation of the in situ proximity ligation assay (isPLA) followed by sequencing (isPLA-seq) to facilitate screening of a high-sensitive, high-throughput sdAb library for a given protein at subcellular and single-cell resolution. Based on the sequence of complementarity-determining region 3 (CDR3), the recombinant sdAb can be produced for in vitro and in vivo utilities. This method provides a general means to identify the functional measure of sdAb and its complementary epitopes and its potential applications to investigate cellular processes.

p62/sequestosome 1 attenuates methylmercury-induced endoplasmic reticulum stress in mouse embryonic fibroblasts

Methylmercury (MeHg) is a hazardous environmental pollutant that causes serious toxicity in humans and animals, as well as proteotoxic stress. In our previous study, we found that MeHg induces the expression of p62/sequestosome 1 (p62) that selectively targets ubiquitinated proteins for degradation via autophagy, and that p62 might protect cells against MeHg toxicity. To further investigate the role of p62 in MeHg-induced stress responses, we evaluated the role of p62 in MeHg-induced endoplasmic reticulum (ER) stress in p62 knockout (p62KO) mouse embryonic fibroblasts (MEFs). Treatment of wild-type (WT) MEFs were treated with MeHg (1 μM) increased mRNA levels of Chop encoding C/EBP homologous protein, Trib3 encoding Tribbles homolog 3, and Dnajb9 encoding DnaJ heat-shock protein family (Hsp40) member B9 increased, suggesting that ER stress is elicited by MeHg stress. Additionally, p62KO MEFs treated with MeHg showed a higher mRNA expression of Chop and Trib3 relative to that in WT MEFs. Furthermore, knock-in of GFP-p62 to p62KO cells diminished the Chop and Trib3 induction responses to MeHg stress and resulted in a higher cell viability than that of p62KO MEFs. These results suggest that the protective role of p62 against MeHg toxicity is partly mediated by suppressing the ER stress response.

CDK1-Mediated Phosphorylation of BAG3 Promotes Mitotic Cell Shape Remodeling and the Molecular Assembly of Mitotic p62 Bodies

The cochaperone BCL2-associated athanogene 3 (BAG3), in complex with the heat shock protein HSPB8, facilitates mitotic rounding, spindle orientation, and proper abscission of daughter cells. BAG3 and HSPB8 mitotic functions implicate the sequestosome p62/SQSTM1, suggesting a role for protein quality control. However, the interplay between this chaperone-assisted pathway and the mitotic machinery is not known. Here, we show that BAG3 phosphorylation at the conserved T285 is regulated by CDK1 and activates its function in mitotic cell shape remodeling. BAG3 phosphorylation exhibited a high dynamic at mitotic entry and both a non-phosphorylatable BAG3^T285A and a phosphomimetic BAG3^T285D protein were unable to correct the mitotic defects in BAG3-depleted HeLa cells. We also demonstrate that BAG3 phosphorylation, HSPB8, and CDK1 activity modulate the molecular assembly of p62/SQSTM1 into mitotic bodies containing K63 polyubiquitinated chains. These findings suggest the existence of a mitotically regulated spatial quality control mechanism for the fidelity of cell shape remodeling in highly dividing cells.

SETD8 involved in the progression of inflammatory bowel disease via epigenetically regulating p62 expression

BACKGROUND AND AIM

Epigenetic modification is an important part of the pathogenesis of inflammatory bowel disease (IBD). Some studies proved that p62 was involved in inflammatory response and upregulated in IBD patients, and histone modification plays an important role in regulating p62 expression. SETD8, a histone H4K20 methyltransferase, has been reported downregulated in some inflammatory diseases. Here, we investigated the role of SETD8 in the development of IBD and its underlying mechanisms.

METHODS

An inflammatory cell model was established to elucidate whether SETD8 involved in inflammatory response in macrophages. Three percent dextran sodium sulfate-induced colitis murine model injection with SETD8 inhibitor was used in our study to investigate whether SETD8 inhibition can affect the progress of IBD. The expression of SETD8 and p62 was measured by qRT-PCR and western blot. The mRNA level of inflammatory cytokines was analyzed by qRT-PCR. In addition, chromatin immunoprecipitation-PCR was performed to identify the mechanism by which SETD8 regulates p62.

RESULTS

SETD8 expression obviously decreased in vitro, in vivo models and in IBD patients. In lipopolysaccharide-activated RAW264.7 cells, knockdown of SETD8 significantly increased the mRNA expression of inducible nitric oxide synthase, cyclooxygenase-2, TNF-α, IL-6, IL-1β, and MCP-1. Based on the dataset, we verified that p62 was a target gene of SETD8 and chromatin immunoprecipitation-PCR assay identified that silence of SETD8 distinctly decreases the H4K20me1 enrichment in the promoter of p62. Moreover, silencing of p62 partly reverses the SETD8 inhibition-mediated pro-inflammatory effect in vitro. Finally, SETD8 pharmacological inhibitor (UNC0379) aggravated the disease progression in dextran sodium sulfate-induced murine colitis.

CONCLUSION

Our findings elucidate an epigenetic mechanism by which SETD8 regulates the p62 expression and restrains the inflammatory response in colitis. Our result suggests that targeting SETD8 may be a promising therapy for IBD.

CD148 Deficiency in Fibroblasts Promotes the Development of Pulmonary Fibrosis

Rationale: CD148/PTRJ (receptor-like protein tyrosine phosphatase η) exerts antifibrotic effects in experimental pulmonary fibrosis via interactions with its ligand syndecan-2; however, the role of CD148 in human pulmonary fibrosis remains incompletely characterized.Objectives: We investigated the role of CD148 in the profibrotic phenotype of fibroblasts in idiopathic pulmonary fibrosis (IPF).Methods: Conditional CD148 fibroblast-specific knockout mice were generated and exposed to bleomycin and then assessed for pulmonary fibrosis. Lung fibroblasts (mouse lung and human IPF lung), and precision-cut lung slices from human patients with IPF were isolated and subjected to experimental treatments. A CD148-activating 18-aa mimetic peptide (SDC2-pep) derived from syndecan-2 was evaluated for its therapeutic potential.Measurements and Main Results: CD148 expression was downregulated in IPF lungs and fibroblasts. In human IPF lung fibroblasts, silencing of CD148 increased extracellular matrix production and resistance to apoptosis, whereas overexpression of CD148 reversed the profibrotic phenotype. CD148 fibroblast-specific knockout mice displayed increased pulmonary fibrosis after bleomycin challenge compared with control mice. CD148-deficient fibroblasts exhibited hyperactivated PI3K/Akt/mTOR signaling, reduced autophagy, and increased p62 accumulation, which induced NF-κB activation and profibrotic gene expression. SDC2-pep reduced pulmonary fibrosis in vivo and inhibited IPF-derived fibroblast activation. In precision-cut lung slices from patients with IPF and control patients, SDC2-pep attenuated profibrotic gene expression in IPF and normal lungs stimulated with profibrotic stimuli.Conclusions: Lung fibroblast CD148 activation reduces p62 accumulation, which exerts antifibrotic effects by inhibiting NF-κB-mediated profibrotic gene expression. Targeting the CD148 phosphatase with activating ligands such as SDC2-pep may represent a potential therapeutic strategy in IPF.

The role of P62 in the development of human thyroid cancer and its possible mechanism

BACKGROUND

Thyroid cancer is the most common malignancy in human endocrine system. Increasing evidence has indicated that p62 plays a key role in tumorigenesis. The roles and underlying molecular mechanisms of P62 in thyroid cancer, however, remain to be elucidated.

METHODS

The expression levels of P62 in thyroid tumor tissues and thyroid cancer cells were detected by western blotting and qRT-PCR. Then, the effects of up-regulation or down-regulation of P62 on thyroid cancer cell proliferation, migration, invasion, cell cycle and apoptosis were measured by CCK-8 assay, transwell assay, flow cytometry and transwell assay, respectively. In terms of the mechanism, P62 could stimulate thyroid cancer progression by the activation of nuclear factor-kappa B (NF-κB) signaling pathway.

RESULTS

P62 was highly expressed in thyroid tumor tissues. Furthermore, high expression of p62 was observed in PTC cell lines, and especially in the K1 and TPC-1 cells. In vitro, the up-regulation of p62 promoted cell proliferation, migration, and invasion of thyroid cancer cells, whereas the knockdown of p62 resulted in the opposite effect. Knock-down of P62 increased the number of cells in the G0/G1 phase but reduced it in the S and G2/M phase. Moreover, we confirmed that overexpression of p62 inactivated NF-κB pathway with sequencing analysis and bioinformatics analysis.

CONCLUSION

This research work suggested that p62 could promote PTC cell proliferation, migration, and invasion via NF-κB signaling pathway. Furthermore, p62 is a potential biomarker which might be closely related to the tumorigenesis in PTC. Its potential role as a therapeutic target for PTC is worthy of further study.

Autophagy promotes invadopodia formation in human ovarian cancer cells via the p62-extracellular signal-regulated kinase 1/2 pathway

Invasiveness and metastatic potential are among the most essential characteristics of malignant tumors. Furthermore, it has been reported that autophagy and invasion are enhanced when tumor cells are grown in adverse conditions, such as nutritional deficiency and starvation. However, the association between autophagy and invasion remains largely unclear. In the present study, Earle's balanced salt solution (EBSS) was used to induce autophagy and an autophagy inhibitor was used to block autophagy. The results of Transwell assays revealed that autophagy inhibition limited the invasiveness of human ovarian cancer cells. Furthermore, the results of invadopodia formation assay indicated that autophagy stimulated invadopodia formation, and the selective autophagy receptor and signaling adaptor, sequestosome-1 (SQSTM1/p62 or simply p62), was closely associated with invadopodia formation in human ovarian cancer SKOV3 cells. The results of western blot analysis indicated that autophagy induced changes in p62 protein levels and p62 then functioned as a negative regulator of extracellular signal-regulated kinase 1/2 (ERK1/2) activity and invadopodia formation. The interaction between autophagy and invasion may thus be a self-protective mechanism for tumor cells in an unfavorable environment of nutritional deficiency, that maintains their survival and leads to increased invasiveness. An exploration of the intrinsic link between autophagy and invasion may provide a novel theoretical basis to reverse the resistance of tumor cells to a nutritional deficient environment.

The Pathways Underlying the Multiple Roles of p62 in Inflammation and Cancer

p62 is a highly conserved, multi-domain, and multi-functional adaptor protein critically involved in several important cellular processes. Via its pronounced domain architecture, p62 binds to numerous interaction partners, thereby influencing key pathways that regulate tissue homeostasis, inflammation, and several common diseases including cancer. Via binding of ubiquitin chains, p62 acts in an anti-inflammatory manner as an adaptor for the auto-, xeno-, and mitophagy-dependent degradation of proteins, pathogens, and mitochondria. Furthermore, p62 is a negative regulator of inflammasome complexes. The transcription factor Nrf2 regulates expression of a bundle of ROS detoxifying genes. p62 activates Nrf2 by interaction with and autophagosomal degradation of the Nrf2 inhibitor Keap1. Moreover, p62 activates mTOR, the central kinase of the mTORC1 sensor complex that controls cell proliferation and differentiation. Through different mechanisms, p62 acts as a positive regulator of the transcription factor NF-κB, a central player in inflammation and cancer development. Therefore, p62 represents not only a cargo receptor for autophagy, but also a central signaling hub, linking several important pro- and anti-inflammatory pathways. This review aims to summarize knowledge about the molecular mechanisms underlying the roles of p62 in health and disease. In particular, different types of tumors are characterized by deregulated levels of p62. The elucidation of how p62 contributes to inflammation and cancer progression at the molecular level might promote the development of novel therapeutic strategies.

CUL5-ASB6 Complex Promotes p62/SQSTM1 Ubiquitination and Degradation to Regulate Cell Proliferation and Autophagy

p62/SQSTM1 (sequestosome-1) is a key protein involved in multiple cellular bioprocesses including autophagy, nutrient sensing, cell growth, cell death, and survival. Therefore, it is implicated in human diseases such as obesity and cancer. Here, we show that the CUL5–ASB6 complex is a ubiquitin E3 ligase complex mediating p62 ubiquitination and degradation. Depletion of CUL5 or ASB6 induced p62 accumulation, and overexpression of ASB6 promoted ubiquitination and degradation of p62. Functionally, ASB6 overexpression can inhibit the proliferation of MEF and hepatocellular carcinoma cells by reducing p62 protein level, and impair the occurrence of autophagy. Overall, our study identified a new molecular mechanism regulating p62 stability, which may provide additional insights for understanding the delicate control of p62 and cell proliferation–autophagy control in physiological and pathological settings.

p62/Sequestosome 1 regulates transforming growth factor beta signaling and epithelial to mesenchymal transition in A549 cells

Transforming growth factor beta (TGFβ) receptor trafficking regulates many TGFβ-dependent cellular outcomes including epithelial to mesenchymal transition (EMT). EMT in A549 non-small cell lung cancer (NSCLC) cells has recently been linked to the regulation of cellular autophagy. Here, we investigated the role of the autophagy cargo receptor, p62/sequestosome 1 (SQSTM1), in regulating TGFβ receptor trafficking, TGFβ1-dependent Smad2 phosphorylation and EMT in A549 NSCLC cells. Using immunofluorescence microscopy, p62/SQSTM1 was observed to co-localize with TGFβ receptors in the late endosome. Small interfering RNA (SiRNA)-mediated silencing of p62/SQSTM1 resulted in an attenuated time-course of Smad2 phosphorylation but did not alter Smad2 nuclear translocation. However, p62/SQSTM1 silencing promoted TGFβ1-dependent EMT marker expression, actin stress fiber formation and A549 cell migration. We further observed that Smad4-independent TGFβ1 signaling decreased p62/SQSTM1 protein levels via a proteasome-dependent mechanism. Although p62/SQSTM1 silencing did not impede TGFβ-dependent autophagy, our results suggest that p62/SQSTM1 may aid in maintaining A549 cells in an epithelial state and TGFβ1 decreases p62/SQSTM1 prior to inducing EMT and autophagy.

Autophagy of the m6A mRNA demethylase FTO is impaired by low-level arsenic exposure to promote tumorigenesis

Here we show that FTO as an N6-methyladenosine (m6A) RNA demethylase is degraded by selective autophagy, which is impaired by low-level arsenic exposure to promote tumorigenesis. We found that in arsenic-associated human skin lesions, FTO is upregulated, while m6A RNA methylation is downregulated. In keratinocytes, chronic relevant low-level arsenic exposure upregulated FTO, downregulated m6A RNA methylation, and induced malignant transformation and tumorigenesis. FTO deletion inhibited arsenic-induced tumorigenesis. Moreover, in mice, epidermis-specific FTO deletion prevented skin tumorigenesis induced by arsenic and UVB irradiation. Targeting FTO genetically or pharmacologically inhibits the tumorigenicity of arsenic-transformed tumor cells. We identified NEDD4L as the m6A-modified gene target of FTO. Finally, arsenic stabilizes FTO protein through inhibiting p62-mediated selective autophagy. FTO upregulation can in turn inhibit autophagy, leading to a positive feedback loop to maintain FTO accumulation. Our study reveals FTO-mediated dysregulation of mRNA m6A methylation as an epitranscriptomic mechanism to promote arsenic tumorigenicity.