Prognostic impact of Beclin 1, p62/sequestosome 1 and LC3 protein expression in colon carcinomas from patients receiving 5-fluorouracil as adjuvant chemotherapy

The Prognostic Value of Autophagy-Related Markers Bclin-1 and LC-3 in Colorectal Cancers: A Systematic Review and Meta-analysis

Objective

At present, the relationship between autophagosomes and the prognosis of various cancers has become a subject of active investigation. A series of studies have demonstrated the correlation between autophagy microtubule-associated protein light chain 3 (LC-3), Beclin-1, and colorectal cancer (CRC). Since autophagy has dual regulatory roles in tumors, the results of this correlation are also uncertain. Hence, we summarized the relationship between Beclin-1, LC-3, and CRC using systematic reviews and meta-analysis to clarify their prognostic significance in it.

Methods

PubMed, EMBASE, Cochrane Library, and Web of Science databases were searched online up to April 1, 2019. The quality of the involving studies was assessed against the Newcastle-Ottawa Scale (NOS). Pooled hazard ratio (HR) and 95% confidence interval (CI) in a fixed or random effects model were used to assess the strength of correlation between Beclin-1, LC-3, and CRC.

Results

A total of 9 articles were collected, involving 2,297 patients. Most literatures scored more than 6 points, suggesting that the quality of our including research was acceptable. Our finding suggested that the expression of Beclin-1 was not associated with overall survival (HR = 0.68, 95% CI (0.31–1.52), P=0.351). Nonetheless, LC-3 expression exerted significant impact on OS (HR = 0.51, 95% CI (0.35–0.74), P < 0.05). Subgroup analysis exhibited that Beclin-1 expression was associated with OS at TNM stage III (HR = 0.04, 95% CI = 0.02–0.08, P < 0.05), surgical treatment (HR = 1.53, 95% CI (1.15–2.02), P=0.003), and comprehensive treatment (HR = 0.27 95% CI (0.08–0.92), P=0.036), respectively. Similarly, the results showed the increased LC-3 expression in CRC was related to OS in multivariate analyses (HR = 0.44, 95% CI (0.34–0.57), P < 0.05), stages (HR = 0.51, 95% CI (0.35–0.74), P < 0.05), and comprehensive treatment (HR = 0.44, 95% CI (0.34–0.57), P < 0.05).

Conclusions

Autophagy-related proteins of LC-3 might be an important marker of CRC progression. However, since the number of the original studies was limited, more well-designed, large-scale, high-quality studies are warranted to provide more convincing and reliable information.

Clarithromycin inhibits autophagy in colorectal cancer by regulating the hERG1 potassium channel interaction with PI3K

We have studied how the macrolide antibiotic Clarithromycin (Cla) regulates autophagy, which sustains cell survival and resistance to chemotherapy in cancer. We found Cla to inhibit the growth of human colorectal cancer (CRC) cells, by modulating the autophagic flux and triggering apoptosis. The accumulation of cytosolic autophagosomes accompanied by the modulation of autophagic markers LC3-II and p62/SQSTM1, points to autophagy exhaustion. Because Cla is known to bind human Ether-à-go-go Related Gene 1 (hERG1) K⁺ channels, we studied if its effects depended on hERG1 and its conformational states. By availing of hERG1 mutants with different gating properties, we found that fluorescently labelled Cla preferentially bound to the closed channels. Furthermore, by sequestering the channel in the closed conformation, Cla inhibited the formation of a macromolecular complex between hERG1 and the p85 subunit of PI3K. This strongly reduced Akt phosphorylation, and stimulated the p53-dependent cell apoptosis, as witnessed by late caspase activation. Finally, Cla enhanced the cytotoxic effect of 5-fluorouracil (5-FU), the main chemotherapeutic agent in CRC, in vitro and in a xenograft CRC model. We conclude that Cla affects the autophagic flux by impairing the signaling pathway linking hERG1 and PI3K. Combining Cla with 5-FU might be a novel therapeutic option in CRC.

High PI3K/mTOR and low MAPK/JNK activity results in decreased apoptosis and autophagy in nasal polyposis

Introduction

Nasal polyposis is a progressive inflammatory disease that reduces the quality of life. The role of apoptotic and autophagic pathways in nasal polyposis pathogenesis is not yet clearly known.

Objective

In this study we aimed to investigate apoptotic (MAPK/JNK), anti-apoptotic (PI3K/mTOR) and autophagic (LC3) pathways which are related each other in the nasal polyposis tissues.

Methods

Twenty patients with nasal polyps and fifteen patients going through an inferior turbinate reduction were included in this study. Patients with asthma, Samter triad and allergic fungal sinusitis were excluded from the study. The apoptotic and autophagic pathways were investigated in paraffin-embedded nasal tissue sections of 20 NP and 15 samples from inferior turbinate reduction by H&E and immunohistochemistry with h-score. TUNEL method with apoptotic index was used to demonstrate apoptotic cells.

Results

Decreased immunoreactivity of P38 MAPK (p < 0.005) and JNK (p < 0.005) were observed in nasal polyposis compared to material from inferior turbinate reduction. This decrease may indicate a downregulation of apoptosis as demonstrated by decreased TUNEL staining in nasal polyposis (p < 0.005). The PI3K (p < 0.002) and mTOR (p < 0.005) immunoreactivities were increased in nasal polyposis. This increase indicates a downregulation of autophagy as demonstrated by decreased LC3 staining in nasal polyposis (p < 0.001).

Conclusion

Deficient apoptosis and autophagy through MAPK/JNK and PI3K/mTOR pathways may have a role in the pathogenesis of nasal polyposis.

The importance of epithelial-mesenchymal transition and autophagy in cancer drug resistance

Epithelial-mesenchymal transition (EMT) and autophagy are both known to play an important role in the development of cancer. Subsequently, these processes are now being utilised as targets for therapy. Cancer is globally one of the leading causes of death, and despite many advances in treatment options, patients still face many challenges. Drug-resistance in cancer-therapy is a large problem, and both EMT and autophagy have been shown to contribute. However, given the context-dependent role of these processes and the complexity of the interactions between them, elucidating how they both act alone and interact together is important. In this review, we will provide an insight into the current landscape of the interactions of autophagy and EMT in the context of malignancy, and how this ultimately may affect drug-resistance in cancer-therapy.

Clinically relevant GSK‑3β inhibitor 9‑ING‑41 is active as a single agent and in combination with other antitumor therapies in human renal cancer

Glycogen synthase kinase-3 (GSK-3), a serine/threonine kinase, is involved in a broad range of pathological processes including cancer. GSK-3 has two isoforms, GSK-3α and GSK-3β, and GSK-3β has been recognized as a therapeutic target for the development of new anticancer drugs. The present study aimed to investigate the antitumor effects of 9-ING-41, which is a maleimide-based ATP-competitive small molecule GSK-3β inhibitor active in patients with advanced cancer. In renal cancer cell lines, treatment with 9-ING-41 alone induced cell cycle arrest and apoptosis, and autophagy inhibitors increased the antitumor effects of 9-ING-41 when used in combination. Treatment with 9-ING-41 potentiated the antitumor effects of targeted therapeutics and increased the cytotoxic effects of cytokine-activated immune cells on renal cancer cell lines. These results provided a compelling rationale for the inclusion of patients with renal cancer in studies of 9-ING-41, both as a single agent and in combination with current standard therapies.

Autophagy alleviates ethanol-induced memory impairment in association with anti-apoptotic and anti-inflammatory pathways

Chronic excessive drinking leads to a wide spectrum of neurological disorders, including cognitive deficits, such as learning and memory impairment. However, the neurobiological mechanisms underlying these deleterious changes are still poorly understood. We conducted a comprehensive study to investigate the role and mechanism of autophagy in alcohol-induced memory impairment. To establish an ethanol-induced memory impairment mouse model, we allowed C57BL/6J mice intermittent access to 20% ethanol (four-bottle choice) to escalate ethanol drinking levels. Memory impairment was confirmed by a Morris water maze test. We found that mice exposed to EtOH (ethanol) and EtOH combined with the autophagy inhibitor 3-methyladenine (3-MA) showed high alcohol intake and blood alcohol concentration. We confirmed that the EtOH group exhibited notable memory impairment. Inhibition of autophagy by 3-MA worsened ethanol-induced memory impairment. Ethanol induced autophagy in the hippocampus of mice as indicated by western blotting, electron microscopy, RT-qPCR, and fluorescence confocal microscopy. We determined that the mTOR/BECN1 (S14) pathway is involved in ethanol-induced autophagy in vivo. Further, ethanol-induced autophagy suppressed the NLRP3 inflammatory and apoptosis pathways in the hippocampus in mice and in vitro. These findings suggest that autophagy activation in hippocampal cells alleviates ethanol-induced memory impairment in association with anti-apoptotic and anti-inflammatory pathways.

Enhancing the Astrocytic Clearance of Extracellular α-Synuclein Aggregates by Ginkgolides Attenuates Neural Cell Injury

The accumulation of aggregated forms of the α-Synuclein (α-Syn) is associated with the pathogenesis of Parkinson's disease (PD), and the efficient clearance of aggregated α-Syn represents a potential approach in PD therapy. Astrocytes are the most numerous glia cells in the brain and play an essential role in supporting brain functions in PD state. In the present study, we demonstrated that cultured primary astrocytes engulfed and degraded extracellular aggregated recombinant human α-Syn. Meanwhile, we observed that the clearance of α-Syn by astrocytes was abolished by proteasome inhibitor MG132 and autophagy inhibitor 3-methyladenine (3MA). We further showed that intracellular α-Syn was reduced after ginkgolide B (GB) and bilobalide (BB) treatment, and the decrease was reversed by MG132 and 3MA. More importantly, GB and BB reduced indirect neurotoxicity to neurons induced by α-Syn-stimulated astrocytic conditioned medium. Together, we firstly find that astrocytes can engulf and degrade α-Syn aggregates via the proteasome and autophagy pathways, and further show that GB and BB enhance astrocytic clearance of α-Syn, which gives us an insight into the novel therapy for PD in future.

Autophagy-related Proteins as a Prognostic Factor of Patients With Colorectal Cancer

OBJECTIVES

Autophagy plays a dual role in tumorigenesis. In the initial stages, it promotes cell survival and suppresses carcinogenesis, whereas in cancer development, it induces cancer cell survival. In this study, we investigate the role of autophagy as a protective or tumor suppressor mechanism in colorectal cancer (CRC) cell lines and evaluate its role as a potential biomarker in human tumor samples.

MATERIALS AND METHODS

The data of 68 patients with CRC treated at our Department from January 1 to December 31, 2016 were analyzed. Immunohistochemistry evaluation of p62, LC3B, Beclin-1, and Rab-7 in formalin-fixed paraffin-embedded tissue samples was performed and their expression was correlated with clinicopathologic characteristics, mutation status, and therapeutic approach. The χ was used to test an association among categorical variables. Survival curves were estimated using the Kaplan-Meier method and differences were assessed using the log-rank test. Colo-205, HT29, SW-480, and Caco-2 cell lines were also used so as to test the autophagy markers with oxaliplatin, irinotecan, hydroxychloroquine, and 3-methyladenine.

RESULTS

Overexpression of Beclin-1 is associated with poor survival (P=0.001) in patients with CRC treated with chemotherapy, irrespective of the stage and mutational status. Rab-7 is also correlated with progression-free survival (PFS) (P=0.088). Oxaliplatin (10 and 20 μΜ) and irinotecan (10 and 20 μΜ) inhibit autophagy in microsatellite stable (MSS) CRC cell lines. The inhibition of autophagy in MSS CRC cell lines after treatment with oxaliplatin and irinotecan is further identified through monodancylcadaverine staining. Moreover, inhibition of autophagy with molecules such as hydroxychloroquine (20 μΜ) and 3-methyladenine (5 mM) was identified by the accumulation of p62 and LC3B.

CONCLUSIONS

Beclin-1 is an independent prognostic factor of overall survival and PFS. Also, Rab-7 is identified as an independent prognostic factor of PFS. Besides, several chemotherapeutic drugs such as oxaliplatin and irinotecan inhibit autophagy in MSS CRC cell lines in a similar way like hydroxychloroquine and 3-methyladenine. Thus, in MSS patients who develop chemoresistance, a combination of other therapies that include an autophagy inhibitor could be more beneficial. Further clinical trials are needed to investigate these therapeutic strategies.

SNX10 (sorting nexin 10) inhibits colorectal cancer initiation and progression by controlling autophagic degradation of SRC

The non-receptor tyrosine kinase SRC is a key mediator of cellular protumorigenic signals. SRC is aberrantly over-expressed and activated in more than 80% of colorectal cancer (CRC) patients, therefore regulation of its stability and activity is essential. Here, we report a significant down regulation of SNX10 (sorting nexin 10) in human CRC tissues, which is closely related to tumor differentiation, TNM stage, lymph node metastasis and survival period. SNX10 deficiency in normal and neoplastic colorectal epithelial cells promotes initiation and progression of CRC in mice. SNX10 controls SRC levels by mediating autophagosome-lysosome fusion and SRC recruitment for autophagic degradation. These mechanisms ensure proper controlling of the activities of SRC-STAT3 and SRC-CTNNB1 signaling pathways by up-regulating SNX10 expression under stress conditions. These findings suggest that SNX10 acts as a tumor suppressor in CRC and it could be a potential therapeutic target for future development.Abbreviations: ACTB: actin beta; ATG5: autophagy related 5; ATG12: autophagy related 12; CQ: chloroquine; CRC: colorectal cancer; CTNNB1: catenin beta 1; EBSS: Earle's balanced salt solution; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LAMP2: lysosomal associated membrane protein 2; MAP1LC3: microtubule associated protein 1 light chain 3; MKI67: marker of proliferation Ki-67; mRNA: messenger RNA; PX: phox homology; RT-qPCR: real time quantitative polymerase chain reaction; siRNA: small interfering RNA; SNX10: sorting nexin 10; SQSTM1: sequestosome 1; SRC: SRC proto-oncogene, non-receptor tyrosine kinase; STAT3: signal transducer and activator of transcription 3; WT: wild type.

Isatin inhibits the invasion of human neuroblastoma SH‑SY5Y cells, based on microarray analysis

Neuroblastoma is the fourth most common type of extracranial malignant solid tumor in children. Isatin had been demonstrated to have inhibitory effects on neuroblastoma tumors in vivo and in vitro. The aim of the present study was to investigate the molecular mechanism related to the anti-invasion effect of isatin on SH-SY5Y cells using microarray analysis. The microarray data identified a number of genes to be differentially upregulated or downregulated between isatin-treated cells and untreated controls. A large number of these genes were associated with the mTOR signaling pathway. The differentially expressed genes involved in the mTOR signaling pathway were verified further, as well as their downstream genes associated with autophagy. The results of the present study provided an insight into the potential inhibitory mechanism of isatin on neuroblastoma metastasis.

Retracted: Long noncoding RNA MEG3 inhibits proliferation and migration but induces autophagy by regulation of Sirt7 and PI3K/AKT/mTOR pathway in glioma cells

Glioma is a common primary brain tumor with high mortality rate and poor prognosis. Long noncoding RNA maternally expressed gene 3 (MEG3) is a tumor suppressor in diverse cancer types. However, the role of MEG3 in glioma remains unclear. We aimed to explore the effects of MEG3 on U251 cells as well as the underlying mechanisms. U251 cells were stably transfected with different recombined plasmids to overexpress or silence MEG3. Effects of aberrantly expressed MEG3 on cell viability, migration, apoptosis, expressions of apoptosis-associated and autophagy-associated proteins, and phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathway were all evaluated. Then, messenger RNA (mRNA) and protein expression of Sirt7 in cells abnormally expressing MEG3 were estimated. In addition, effects of abnormally expressed MEG3 and Sirt7 on U251 cells were determined to reveal the underlying mechanism of MEG3-associated modulation. Cell viability and migration were significantly reduced by MEG3 overexpression whereas cell apoptosis as well as Bax and cleaved caspase-3/-9 proteins were obviously induced. Beclin-1 and LC3-II/LC3-I were upregulated and p62 was downregulated in MEG3 overexpressed cells. In addition, the autophagy pharmacological inhibitor (3-methyladenine, 3-MA) affected the effect of MEG3 overexpression on cell proliferation. Furthermore, the phosphorylated levels of key kinases in the PI3K/AKT/mTOR pathway were all reduced by MEG3 overexpression. Sirt7 was positively regulated by MEG3 expression, and effects of MEG3 overexpression on U251 cells were ameliorated by Sirt7 silence. MEG3 suppressed cell proliferation and migration but promoted autophagy in U251 cells through positively regulating Sirt7, involving in the inhibition of the PI3K/AKT/mTOR pathway.

Pro-survival autophagy and cancer cell resistance to therapy

Resistance to therapy is one of the prime causes for treatment failure in cancer and recurrent disease. In recent years, autophagy has emerged as an important cell survival mechanism in response to different stress conditions that are associated with cancer treatment and aging. Autophagy is an evolutionary conserved catabolic process through which damaged cellular contents are degraded after uptake into autophagosomes that subsequently fuse with lysosomes for cargo degradation, thereby alleviating stress. In addition, autophagy serves to maintain cellular homeostasis by enriching nutrient pools. Although autophagy can act as a double-edged sword at the interface of cell survival and cell death, increasing evidence suggest that in the context of cancer therapy-induced stress responses, it predominantly functions as a cell survival mechanism. Here, we provide an up-to-date overview on our current knowledge of the role of pro-survival autophagy in cancer therapy at the preclinical and clinical stages and delineate the molecular mechanisms of autophagy regulation in response to therapy-related stress conditions. A better understanding of the interplay of cancer therapy and autophagy may allow to unveil new targets and avenues for an improved treatment of therapy-resistant tumors in the foreseeable future.

Selected Aspects of Chemoresistance Mechanisms in Colorectal Carcinoma-A Focus on Epithelial-to-Mesenchymal Transition, Autophagy, and Apoptosis

Chemoresistance has been found in all malignant tumors including colorectal carcinoma (CRC). Nowadays chemoresistance is understood as a major reason for therapy failure, with consequent tumor growth and spreading leading ultimately to the patient's premature death. The chemotherapy-related resistance of malignant colonocytes may be manifested in diverse mechanisms that may exist both prior to the onset of the therapy or after it. The ultimate function of this chemoresistance is to ensure the survival of malignant cells through continuing adaptation within an organism, therefore, the nature and spectrum of cell-survival strategies in CRC represent a highly significant target of scientific inquiry. Among these survival strategies employed by CRC cells, three unique but significantly linked phenomena stand out-epithelial-to-mesenchymal transition (EMT), autophagy, and cell death. In this mini-review, current knowledge concerning all three mechanisms including their emergence, timeline, regulation, and mutual relationships will be presented and discussed.

p62/SQSTM1: 'Jack of all trades' in health and cancer

p62 is a stress‐inducible protein able to change among binding partners, cellular localizations and form liquid droplet structures in a context‐dependent manner. This protein is mainly defined as a cargo receptor for selective autophagy, a process that allows the degradation of detrimental and unnecessary components through the lysosome. Besides this role, its ability to interact with multiple binding partners allows p62 to act as a main regulator of the activation of the Nrf2, mTORC1, and NF‐κB signaling pathways, linking p62 to the oxidative defense system, nutrient sensing, and inflammation, respectively. In the present review, we will present the molecular mechanisms behind the control p62 exerts over these pathways, their interconnection and how their deregulation contributes to cancer progression.

Baicalin alleviates 6-hydroxydopamine-induced neurotoxicity in PC12 cells by down-regulation of microRNA-192-5p

Parkinson's disease (PD), which is caused by neurodegenerative disorder, has no effective treatment until now. Baicalin was reported to have neuroprotective effects. Hence, we investigated the effects of baicalin on PD in an in vitro cell model by using 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in rat pheochromocytoma PC12 cells. PC12 cells were stimulated by 6-OHDA and were treated with baicalin and/or transfected with miR-192-5p mimic or negative control (NC). Cell viability and apoptosis were examined by Cell Counting Kit-8 assay and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) analysis, respectively. The expression of p62, ratio of light chain (LC)3-II/LC3-I, miR-192-5p was detected by qRT-PCR. All protein expression levels were analyzed by western blot. We found that 6-OHDA significantly inhibited cell viability, induced apoptosis and autophagy, while baicalin reversed the results led by 6-OHDA. Moreover, baicalin negatively regulated expression of miR-192-5p. Under baicalin treatment, transfection with miR-192-5p mimic decreased cell viability and induced apoptosis and autophagy in 6-OHDA-treated cells compared with NC. In addition, the phosphorylation of phosphatidylinositol 3'-kinase (PI3K) and protein kinase B (AKT) was statistically down-regulated by baicalin then thereafter reversed by miR-192-5p mimic. Baicalin reduced 6-OHDA-induced cell injury through down-regulation of miR-192-5p, as well as regulation of PI3K/AKT and MDM-2/p53 signal pathways.

Effects of Beclin 1 overexpression on aggressive phenotypes of colon cancer cells

Beclin 1 is involved in autophagy, differentiation, apoptosis and cancer progression, and functions as a haploinsufficient tumor suppressor gene. The aim of the present study was to elucidate the function of Beclin 1 in colon cancer. A Beclin 1-expressing plasmid was transfected into HCT-15 and HCT-116 cells, and the phenotypes and associated molecules were determined. Beclin 1 transfectants were subcutaneously injected into nude mice to determine tumor growth, and proliferation and apoptosis levels using Ki-67 immunostaining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), respectively. Beclin 1 overexpression inhibited viability as determined using a Cell Counting Kit-8 assay, inhibited migration and invasion as determined using a wound healing assay or Transwell assay, and lamellipodia formation by filamentous actin staining, induced autophagy as determined using electron microscopy, and light chain 3B (LC-3B) expression, and apoptosis as determined using Annexin V staining in the two cell lines (P<0.05). Beclin 1 induced G₂ arrest of HCT-15 transfectants as determined using propidium iodide staining (P<0.05), whereas HCT-116 transfectants were arrested in G₁ phase (P<0.05). The two transfectants exhibited increased expression of c-Myc, cyclin D1, β-catenin, insulin-response element 1 and 78 kDa glucose-regulated protein compared with the control and mock cells as determined using the reverse transcription-quantitative polymerase chain reaction (P<0.05). Beclin 1 overexpression upregulated LC-3B and cyclin-dependent kinase 4 expression, but downregulated cyclin E expression of the cancer cell lines as determined using western blot analysis (P<0.05). Beclin 1 expression in vivo significantly suppressed the proliferation of colon cancer cells in xenograft models via inducing apoptosis by TUNEL, and inhibiting proliferation by Ki-67 expression (P<0.05). Beclin 1 overexpression may reverse aggressive phenotypes and suppress colon cancer tumor growth, and be employed as a target molecule for gene therapy of patients with colon cancer.

Nrf2 inhibition reverses resistance to GPX4 inhibitor-induced ferroptosis in head and neck cancer

Glutathione peroxidase 4 (GPX4) is a regulator of ferroptosis (iron-dependent, non-apoptotic cell death); its inhibition can render therapy-resistant cancer cells susceptible to ferroptosis. However, some cancer cells develop mechanisms protective against ferroptosis; understanding these mechanisms could help overcome chemoresistance. In this study, we investigated the molecular mechanisms underlying resistance to ferroptosis induced by GPX4 inhibition in head and neck cancer (HNC). The effects of two GPX4 inhibitors, (1S, 3R)-RSL3 and ML-162, and of trigonelline were tested in HNC cell lines, including cisplatin-resistant (HN3R) and acquired RSL3-resistant (HN3-rslR) cells. The effects of the inhibitors and trigonelline, as well as of inhibition of the p62, Keap1, or Nrf2 genes, were assessed by cell viability, cell death, lipid ROS production, and protein expression, and in mouse tumor xenograft models. Treatment with RSL3 or ML-162 induced the ferroptosis of HNC cells to varying degrees. RSL3 or ML-162 treatment increased the expression of p62 and Nrf2 in chemoresistant HN3R and HN3-rslR cells, inactivated Keap1, and increased expression of the phospho-PERK-ATF4-SESN2 pathway. Transcriptional activation of Nrf2 was associated with resistance to ferroptosis. Overexpression of Nrf2 by inhibiting Keap1 or Nrf2 gene transfection rendered chemosensitive HN3 cells resistant to RSL3. However, Nrf2 inhibition or p62 silencing sensitized HN3R cells to RSL3. Trigonelline sensitized chemoresistant HNC cells to RSL3 treatment in a mouse model transplanted with HN3R. Thus, activation of the Nrf2-ARE pathway contributed to the resistance of HNC cells to GPX4 inhibition, and inhibition of this pathway reversed the resistance to ferroptosis in HNC.

p62/SQSTM1 - steering the cell through health and disease

SQSTM1 (also known as p62) is a multifunctional stress-inducible scaffold protein involved in diverse cellular processes. Its functions are tightly regulated through an extensive pattern of post-translational modifications, and include the isolation of cargos degraded by autophagy, induction of the antioxidant response by the Keap1-Nrf2 system, as well as the regulation of endosomal trafficking, apoptosis and inflammation. Accordingly, malfunction of SQSTM1 is associated with a wide range of diseases, including bone and muscle disorders, neurodegenerative and metabolic diseases, and multiple forms of cancer. In this Review, we summarize current knowledge regarding regulation, post-translational modifications and functions of SQSTM1, as well as how they are dysregulated in various pathogenic contexts.

The Roles of Autophagy in Cancer

Autophagy is an intracellular degradative process that occurs under several stressful conditions, including organelle damage, the presence of abnormal proteins, and nutrient deprivation. The mechanism of autophagy initiates the formation of autophagosomes that capture degraded components and then fuse with lysosomes to recycle these components. The modulation of autophagy plays dual roles in tumor suppression and promotion in many cancers. In addition, autophagy regulates the properties of cancer stem-cells by contributing to the maintenance of stemness, the induction of recurrence, and the development of resistance to anticancer reagents. Although some autophagy modulators, such as rapamycin and chloroquine, are used to regulate autophagy in anticancer therapy, since this process also plays roles in both tumor suppression and promotion, the precise mechanism of autophagy in cancer requires further study. In this review, we will summarize the mechanism of autophagy under stressful conditions and its roles in tumor suppression and promotion in cancer and in cancer stem-cells. Furthermore, we discuss how autophagy is a promising potential therapeutic target in cancer treatment.

Cytoplasmic SQSTM1/ P62 Accumulation Predicates a Poor Prognosis in Patients with Malignant Tumor

Aims: SQSTM1/p62, as an autophagy marker, is a key molecule involved in the autophagy process. Recent studies have demonstrated that p62 has a close relationship with tumorigenesis and progression, but the impact of p62 on patients' survival has not been comprehensively understood. Therefore, we conducted this study to assess the expression level of p62 in tumor cells and the prognostic role of p62 expression in various malignant tumors. Methods: We searched PubMed, PubMed Central (PMC), Embase, Ovid and Web of Science databases and identified 30 eligible studies containing 14,072 patients to include in the meta-analysis. The p62 mRNA and protein expression profiles in various tumor tissues and normal tissues were presented according to the Human Protein Atlas (HPA) and the Gene Expression Profiling Interactive Analysis (GEPIA). We also tested the association between p62 mRNA level and patients' survival based on the Cancer Genome Atlas (TCGA) and the Human Protein Atlas (HPA) databases. Results: The expression levels of p62 mRNA and protein varied in different tissues. The p62 proteins were elevated and mainly located in the cytoplasm in some types of tumor compared with the normal tissues. The pooled results indicated that p62 overexpression in tumor tissues was associated with a worse prognosis. In the subgroup analysis, a significant relationship was observed between cytoplasmic p62 accumulation and both overall survival (HR 1.53, 95% CI: 1.03-2.27, P < 0.05) and disease-specific survival (HR 1.60, 95% CI: 1.15-2.24, P < 0.01). The relationship between p62 and worse survival was more evident in early stage tumors. P62 mRNA expression had no significant effect on the patient's survival except of liver cancer. Conclusions: The findings of this meta-analysis highlight the role of p62 as a useful prognostic biomarker for some types of tumor according to different clinicopathologic features, which may contribute to the selection of effective treatment methods for different malignant tumors.

Autophagy is positively associated with the accumulation of myeloid‑derived suppressor cells in 4‑nitroquinoline‑1‑oxide‑induced oral cancer

It has previously been demonstrated that autophagy and inflammation act synergistically to promote carcinogenesis. However, the precise roles of autophagy in multistep oral carcinogenesis are still unclear, particularly regarding its association with tumor inflammation. The present study established a 4NQO-induced oral cancer mouse model and investigated autophagy status in the multistep process of oral carcinogenesis using immunohistochemistry, western blotting and immunofluorescence staining. Furthermore, the number of Gr-1⁺CD11b⁺ myeloid derived suppressor cells (MDSCs) and CD4⁺ Foxp3⁺ regulatory T cells (Tregs) during oral carcinogenesis and the association with autophagy status was also examined. The results revealed that the expression of autophagy biomarkers, including dihydrosphingosine 1-phosphate phosphatase LCB3 (LC3B), p62/SQSTM1 (p62) and Beclin 1 increased during 4NQO-induced carcinogenesis and in human oral cancer. The number of MDSCs and Tregs also increased during oral carcinogenesis. Furthermore, the expression of LC3B and p62 significantly correlated with the accumulation of MDSCs and the expression of Beclin 1 correlated with the increase of Tregs. These data indicated that autophagy may be activated by the tumor inflammation microenvironment during oral carcinogenesis.

TSSC3 promotes autophagy via inactivating the Src-mediated PI3K/Akt/mTOR pathway to suppress tumorigenesis and metastasis in osteosarcoma, and predicts a favorable prognosis

BACKGROUND

Over the last two or three decades, the pace of development of treatments for osteosarcoma tends has been slow. Novel effective therapies for osteosarcoma are still lacking. Previously, we reported that tumor-suppressing STF cDNA 3 (TSSC3) functions as an imprinted tumor suppressor gene in osteosarcoma; however, the underlying mechanism by which TSSC3 suppresses the tumorigenesis and metastasis remain unclear.

METHODS

We investigated the dynamic expression patterns of TSSC3 and autophagy-related proteins (autophagy related 5 (ATG5) and P62) in 33 human benign bone tumors and 58 osteosarcoma tissues using immunohistochemistry. We further investigated the correlations between TSSC3 and autophagy in osteosarcoma using western blotting and transmission electronic microscopy. CCK-8, Edu, and clone formation assays; wound healing and Transwell assays; PCR; immunohistochemistry; immunofluorescence; and western blotting were used to investigated the responses in TSSC3-overexpressing osteosarcoma cell lines, and in xenografts and metastasis in vivo models, with or without autophagy deficiency caused by chloroquine or ATG5 silencing.

RESULTS

We found that ATG5 expression correlated positively with TSSC3 expression in human osteosarcoma tissues. We demonstrated that TSSC3 was an independent prognostic marker for overall survival in osteosarcoma, and positive ATG5 expression associated with positive TSSC3 expression suggested a favorable prognosis for patients. Then, we showed that TSSC3 overexpression enhanced autophagy via inactivating the Src-mediated PI3K/Akt/mTOR pathway in osteosarcoma. Further results suggested autophagy contributed to TSSC3-induced suppression of tumorigenesis and metastasis in osteosarcoma in vitro and in vivo models.

CONCLUSIONS

Our findings highlighted, for the first time, the importance of autophagy as an underlying mechanism in TSSC3-induced antitumor effects in osteosarcoma. We also revealed that TSSC3-associated positive ATG5 expression might be a potential predictor of favorable prognosis in patients with osteosarcoma.

Hedgehog Signaling Pathway and Autophagy in Cancer

Hedgehog (Hh) pathway controls complex developmental processes in vertebrates. Abnormal activation of Hh pathway is responsible for tumorigenesis and maintenance of multiple cancers, and thus addressing this represents promising therapeutic opportunities. In recent years, two Hh inhibitors have been approved for basal cell carcinoma (BCC) treatment and show extraordinary clinical outcomes. Meanwhile, a series of novel agents are being developed for the treatment of several cancers, including lung cancer, leukemia, and pancreatic cancer. Unfortunately, Hh inhibition fails to show satisfactory benefits in these cancer types compared with the success stories in BCC, highlighting the need for better understanding of Hh signaling in cancer. Autophagy, a conserved biological process for cellular component elimination, plays critical roles in the initiation, progression, and drug resistance of cancer, and therefore, implied potential to be targeted. Recent evidence demonstrated that Hh signaling interplays with autophagy in multiple cancers. Importantly, modulating this crosstalk exhibited noteworthy capability to sensitize primary and drug-resistant cancer cells to Hh inhibitors, representing an emerging opportunity to reboot the efficacy of Hh inhibition in those insensitive tumors, and to tackle drug resistance challenges. This review will highlight recent advances of Hh pathway and autophagy in cancers, and focus on their crosstalk and the implied therapeutic opportunities.

A specific expression profile of LC3B and p62 is associated with nonresponse to neoadjuvant chemotherapy in esophageal adenocarcinomas

Paclitaxel is a powerful chemotherapeutic drug, used for the treatment of many cancer types, including esophageal adenocarcinomas (EAC). Autophagy is a lysosome-dependent degradation process maintaining cellular homeostasis. Defective autophagy has been implicated in cancer biology and therapy resistance. We aimed to assess the impact of autophagy on chemotherapy response in EAC, with a special focus on paclitaxel. Responsiveness of EAC cell lines, OE19, FLO-1, OE33 and SK-GT-4, to paclitaxel was assessed using Alamar Blue assays. Autophagic flux upon paclitaxel treatment in vitro was assessed by immunoblotting of LC3B-II and quantitative assessment of WIP1 mRNA. Immunohistochemistry for the autophagy markers LC3B and p62 was applied on tumor tissue from 149 EAC patients treated with neoadjuvant chemotherapy, including pre- and post-therapeutic samples (62 matched pairs). Tumor response was assessed by histology. For comparison, previously published data on 114 primary resected EAC cases were used. EAC cell lines displayed differing responsiveness to paclitaxel treatment; however this was not associated with differential autophagy regulation. High p62 cytoplasmic expression on its own (p ≤ 0.001), or in combination with low LC3B (p = 0.034), was associated with nonresponse to chemotherapy, regardless of whether or not the regiments contained paclitaxel, but there was no independent prognostic value of LC3B or p62 expression patterns for EAC after neoadjuvant treatment. p62 and related pathways, most likely other than autophagy, play a role in chemotherapeutic response in EAC in a clinical setting. Therefore p62 could be a novel therapeutic target to overcome chemoresistance in EAC.

Knockdown of Beclin-1 impairs epithelial-mesenchymal transition of colon cancer cells

Activation of autophagy significantly affects cancer cell behaviors, such as proliferation, differentiation, and invasiveness. Epithelial-to-mesenchymal transition (EMT) as an initial step of malignant transformation of cancer cells was linked to the activation of autophagy, but the detailed molecular mechanisms are still unknown. The present study investigates the effects of Beclin-1, a key molecule involved in activation of autophagy, on EMT of colon cancer cells. The normal colon epithelia cell line of CCD-18Co and six colon cancer cell lines with different expression levels of Beclin-1 were used in this study. The activation of autophagy and EMT markers of cancer cells were monitored by Western blotting and quantitative real-time PCR assay in the presence or absence of rapamycin (autophagy activator) and 3-MA (autophagy inhibitor). The expression of Beclin-1 in selected cell lines was modulated using small interfering RNA, and consequentially EMT markers, and cancer cell behaviors including migration and invasion, were also explored. Activation or inhibition of autophagy in colon cancer cells had positive or negative impacts on the expression of EMT markers and malignant behaviors such as cell migration and invasion. Knockdown of beclin-1 by siRNA apparently inhibited the activation of autophagy induced by rapamycin, consequentially resulted in suppression of EMT and attenuation of invasiveness of colon cancer cells. The results in this study demonstrated an association between activation of autophagy and EMT in colon cancer cells. The results showed suppression of Beclin-1 expression significantly reduced EMT and invasive behaviors in colon cancer cells.

LncRNA HULC mediates radioresistance via autophagy in prostate cancer cells

Prostate cancer (PCa) is the second leading cause of cancer death in men. Irradiation is one of the available options for treatment of PCa, however, approximately 10-45% of PCa are resistant to irradiation. We aimed to explore the role of long non-coding RNA highly upregulated in liver cancer (HULC) in the sensitivity of PCa cells to irradiation. Survival rate, cell apoptosis, cycle, expressions of related proteins, and caspase-3 activity were assessed to explore the effects of HULC on sensitivity of PCa cells to irradiation. Expression of HULC in DU-145, PC3, LNCaP, and RWPE-1 cells was determined and the influence of HULC on DU-145 cells was explored. Then, PC3 cells aberrantly expressing HULC were implanted into NOD-SCID mice for tumor xenograft study. Changes of autophagy after aberrant expression of HULC in vivo and in vitro were tested. Furthermore, the interacted protein of HULC and involved signaling pathway were investigated. In PC3 and LNCaP cells under irradiation, survival rate and cell cycle were decreased and apoptosis was increased by HULC knockdown. HULC knockdown arrested PC3 cells at G0/G1 phase. DU-145 was sensitive to irradiation, and resistance to irradiation of DU-145 cells was enhanced by HULC overexpression. Moreover, HULC knockdown enhanced the sensitivity of PC3 xenografts to irradiation. HULC knockdown promoted autophagy through interaction with Beclin-1 and inhibition of mTOR, resulting in increased apoptosis. HULC knockdown improved sensitivity of PCa cells to irradiation both in vivo and in vitro. HULC suppressed Beclin-1 phosphorylation, thereby reduced autophagy, involving the mTOR pathway.

Effects of intermedin on autophagy in cerebral ischemia/reperfusion injury

OBJECTIVE

This study aimed to evaluate the effects of intermedin (IMD) on autophagy in cerebral ischemia/reperfusion (I/R) injury (CIRI).

METHODS

Sixty rats were randomly averaged into four groups: sham, ischemia/reperfusion (I/R), IMD, and 3-methyladenine (3-MA). In the sham group, the right common carotid artery, external carotid artery, and internal carotid artery were detached, and no monofilament was inserted. In the other groups, two hours after cerebral ischemia, the rats were injected through the lateral ventricle with normal saline for I/R group, IMD for the IMD group, and 3-MA for the 3-MA group for 24h. The cerebral injury was assessed by evaluation of neurological function, hematoxylin and eosin (H&E) staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. The expressions of autophagy associated proteins, such as microtubule-associated protein 1 light chain 3 (LC3), Beclin1, and sequestosome 1 (P62) were analyzed using immunohistochemistry staining and western blot. Meanwhile, transmission electron microscopy was used to investigate the ultrastructure of the brains.

RESULTS

IMD could reduce neuron cell damage and infarction formation and has a protective effect against CIRI as 3-MA. The levels of LC3II/LC3I and Beclin1 were significantly decreased and the P62 level was significantly higher in the IMD group compared with I/R group, which is similar to the effect of 3-MA on CIRI.

CONCLUSIONS

IMD has a similar effect as 3-MA, can reduce pathological neuronal injury and protect the brain against CIRI in rats by attenuating the effects of autophagy. Our findings provide evidence for IMD's protective effects in relation to ischemic cerebrovascular diseases.

Autophagy Modulation in Cancer: Current Knowledge on Action and Therapy

In the last two decades, accumulating evidence pointed to the importance of autophagy in various human diseases. As an essential evolutionary catabolic process of cytoplasmatic component digestion, it is generally believed that modulating autophagic activity, through targeting specific regulatory actors in the core autophagy machinery, may impact disease processes. Both autophagy upregulation and downregulation have been found in cancers, suggesting its dual oncogenic and tumor suppressor properties during malignant transformation. Identification of the key autophagy targets is essential for the development of new therapeutic agents. Despite this great potential, no therapies are currently available that specifically focus on autophagy modulation. Although drugs like rapamycin, chloroquine, hydroxychloroquine, and others act as autophagy modulators, they were not originally developed for this purpose. Thus, autophagy may represent a new and promising pharmacologic target for future drug development and therapeutic applications in human diseases. Here, we summarize our current knowledge in regard to the interplay between autophagy and malignancy in the most significant tumor types: pancreatic, breast, hepatocellular, colorectal, and lung cancer, which have been studied in respect to autophagy manipulation as a promising therapeutic strategy. Finally, we present an overview of the most recent advances in therapeutic strategies involving autophagy modulators in cancer.

Wogonoside inhibits cell growth and induces mitochondrial-mediated autophagy-related apoptosis in human colon cancer cells through the PI3K/AKT/mTOR/p70S6K signaling pathway

Wogonoside, the main effective constituent of traditional Chinese medicine Scutellaria, belongs to the glucuronide family, with various functions, including detoxification, anti-inflammation and nourishing gallbladder, lowering blood pressure, diuresis and anti-allergic reactions. However, the effects of wogonoside on human colon cancer cells remain unclear. The present study aimed to investigate the anticancer effect of wogonoside on human colon cancer cells in vitro and its anticancer mechanisms. The results demonstrated that wogonoside significantly inhibited cell growth, induced apoptosis and mitochondrial-mediated autophagy of colon cancer cells. Furthermore, the results revealed that wogonoside significantly increased caspase-3 and caspase-9 expression levels, induced apoptosis regulator Bax/Bcl-2 and microtubule-associated protein 1A/1B-light chain 3 protein expression, suppressed the phosphatidylinositol 3 kinase (PI3K)/RAC-α serine/threonine-protein kinase (Akt)/mechanistic target of rapamycin (mTOR)/p70 S6 kinase (p70S6K) signaling pathway and induced p62 protein expression in colon cancer cells. In conclusion, these results demonstrated that wogonoside inhibits cell growth and induces mitochondrial mediated autophagy-related apoptosis in human colon cancer cells through modulation of the PI3K/Akt/mTOR/p70S6K signaling pathway.

The prognostic value of p62 in solid tumor patients: a meta-analysis

p62, as a scaffolding/adaptor protein, is involved in multiple physiological processes include inflammation, autophagy and mitosis. However, the influence of p62 in cancer patients has not been comprehensively investigated. Moreover, the prognostic value of p62 for the survival of patients with solid tumors remains controversial. In this present meta-analysis, twenty suitable articles were identified from PubMed, EMBASE and Web of Science, Nature databases, including 4271 patients. A random-effect or fixed-effect model was adopted to correlate p62 expression with different outcome measured in entire tumors. Combined with results of hazard ratios (HRs) and 95% confidence intervals (CIs), we concluded that higher expression of p62 is associated with poorer overall survival (OS) (HR: 2.22, 95% CI: 1.82–2.71, P < 0.05), disease-free survival (DFS) (HR = 2.48, 95% CI: 1.78–3.46, P < 0.05) and even certain clinicopathological parameters, such as lymph node metastasis (RR = 1.21, 95% CI: 1.06–1.37) and clinical stages (RR = 1.27, 95% CI: 1.12–1.45), in cancer patients. Consequently, our data showed that p62 might be an effective poor prognostic factor for patients with various solid tumors.

Inhibition of miR-20 promotes proliferation and autophagy in articular chondrocytes by PI3K/AKT/mTOR signaling pathway

Osteoarthritis is a common cause of functional deterioration in older adults and is an immense burden on the aging population. The molecular mechanism underlying the regulation of chondrocyte requires further elucidation, particularly with respect to the role of microRNAs. The aim of this study was to identify and characterize the expression of miR-20 in normal and OA chondrocytes, and to determine its role in OA pathogenesis. MiR-20 expression in cartilage specimens was examined in 30 patients with knee osteoarthritis and 30 traumatic amputees. The effect of miR-20 on chondrocyte was also investigated in chondrocyte cell line. Transfection with miR-20 mimic or inhibitor was employed to investigate the effect of miR-20 on chondrocyte proliferation and autophagy. Cell proliferation activity was detected by MTT assay and clone formation, cell autophagy were evaluated by monodansylcadaverine staining and GFP-LC3 fluorescence microscopy. Western blotting and immunohistochemical were utilized to detect expressions of autophagy markers (LC3, Beclin1 and p62) and of relevant proteins in the PI3K/AKT/mTOR signaling pathway. The results demonstrated that miR-20 inhibit chondrocyte proliferation and autophagy by targeting ATG10 via PI3K/AKT/mTOR signaling pathway. Our data suggest that miR-20 has an important role in the pathogenesis of osteoarthritis and is a potential therapeutic target.

A Prognostic Bio-Model Based on SQSTM1 and N-Stage Identifies Nasopharyngeal Carcinoma Patients at High Risk of Metastasis for Additional Induction Chemotherapy

Purpose: Metastasis is one of the most important causes of treatment failure in nasopharyngeal carcinoma (NPC). In T4 or N2-3 patients at high-risk of metastasis, concurrent chemoradiotherapy (CCRT) is inadequate and additional induction chemotherapy (IC) is controversial. There is a critical need to develop a better patient stratification to efficiently identify patients at high-risk of metastasis for additional IC. Recently, Sequestosome 1 (SQSTM1)/p62, an autophagy adaptor protein, was identified as one of the metastasis-related proteins in NPC. However, the mechanism by which SQSTM1 is involved in NPC metastasis was not investigated.Experimental Design: The effect of SQSTM1 on cell migration and invasion was examined in vitro and in vivo SQSTM1 expression was analyzed in clinical NPC samples using IHC. Luciferase reporter analyses were conducted to identify the effects of SQSTM1 on NF-κB transcriptional activity. A prediction bio-model was constructed by Cox analysis. Retrospective and prospective randomized clinical data were adopted to build and test the model, respectively.Results: SQSTM1 mediated epithelial to mesenchymal transition (EMT) through the NF-κB pathway to promote NPC metastasis. Inhibiting SQSTM1 enhanced sensitivity to cisplatin in NPC cells. In NPC patients, high SQSTM1 expression was associated with increased risk of distant metastasis. Furthermore, we propose a prognostic bio-model based on SQSTM1 and N-stage to predict NPC metastasis. Most importantly, our prospective randomized study suggested that IC is beneficial for NPC patients with high metastasis risk.Conclusions: The prognostic bio-model identifies NPC patients at high-risk of metastasis for additional IC. Clin Cancer Res; 24(3); 648-58. ©2017 AACR.

Beclin 1 and LC3 as predictive biomarkers for metastatic colorectal carcinoma

Autophagy is a highly conserved self-destructive process that disassembles dysfunctional or unnecessary cellular components. It plays an important role in cancer metastasis, which is of particular interest considering metastatic disease is the major cause of colorectal carcinoma (CRC) related mortality. Here, we investigated the immunohistochemical expression of autophagy-related protein Beclin 1 and Microtubule-associated protein 1A/1B-light chain 3 (LC3) within surgical CRC specimens, first in a training cohort (205 patients), then in an inner validation cohort (160 patients) and an independent cohort (161 patients). The expressions of Beclin 1 and LC3 were lower in metastatic CRC compared with non-metastatic CRC. Furthermore, we developed an autophagy-based classifier for metastatic prediction. This classifier, including Beclin 1, LC3 and carcinoembryonic antigen (CEA) level, resulted in 82.9% sensitivity and 89.8% specificity for metastatic detection in the training cohort. In the independent cohort, it achieved 77.9% sensitivity and 90.3% specificity in predicting the metastasis of CRC. These results suggested that low expression of Beclin 1 and LC3 contributed to a more aggressive cancer cell phenotype, and our autophagy-based classifier was a reliable tool for metastatic prediction in CRC.

Effects of endurance training on autophagy and apoptotic signaling in visceral adipose tissue of prolonged high fat diet-fed rats

PURPOSE

Autophagy and apoptosis play critical roles in both development and tissue homeostasis in response to (patho)physiological stimuli, such as high-fat diet (HFD) and endurance training (ET). Therefore, we aimed to investigate how ET modulates autophagy and apoptotic-related signaling in visceral adipose tissue of long-standing HFD-fed rats.

METHODS

The study was conducted over a 17-week period on Sprague-Dawley rats, which were divided into four groups (n = 8/group): standard diet sedentary (STD+SED), high-fat diet sedentary (HFD+SED), standard diet ET (STD+ET) and high-fat diet ET (HFD+ET). After 9 weeks of dietary regimens, ET groups were trained for 8 weeks on treadmill (5 days/week at 25 m/min for 60 min/day), while maintaining dietary regimens. Autophagy and apoptotic-signaling markers in epididymal white adipose tissue (eWAT) were determined using RT-qPCR, Western blot and spectrometry techniques.

RESULTS

ET reduced body weight, visceral fat mass and HOMA-IR in standard and HF diet-fed animals. Moreover, ET reverted the HFD-induced increases in the percentage of larger adipocytes and also reduced the percentage of smaller adipocytes. The HFD decreased pre-adipocyte factor 1 (DLK1/PREF1) and increased the pro-apoptotic markers (Bax protein and caspase 3-like activity), while having no impact on autophagy markers. However, ET increased DLK1/PREF1 and Bcl-2 in both diet types, while decreasing Bax and caspases 9, 8 and 3-like activities in HFD feeding rats. Additionally, Beclin-1 and p62 protein significantly increased in ET groups of both diet types.

CONCLUSIONS

Data demonstrate that 8 weeks of ET was effective in attenuating apoptotic-related signaling in long-standing HFD-fed rats. Moreover, HFD and ET had no impact on VAT autophagy markers.

p62/sequestosome 1 in human colorectal carcinoma as a potent prognostic predictor associated with cell proliferation

p62/sequestosome 1 (p62) is a multi-domain protein that functions as a receptor for ubiquitinated targets in the selective autophagy and serves as a scaffold in various signaling cascades. p62 have been reported to be up-regulated in several human malignancies, but the biological roles and significance of p62 are still poorly understood in colorectal carcinoma. We immunohistochemically evaluated p62 in 118 colorectal adenocarcinoma and 28 colorectal adenoma cases. We used four colon carcinoma cells (HCT8, HT29, COLO320, and SW480) in the in vitro studies. p62 immunoreactivity was detected in 11% of colorectal adenoma cases and 31% of adenocarcinoma cases, while it was negligible in the normal epithelium. The immunohistochemical p62 status was significantly associated with synchronous liver metastasis, and it turned out to be an independent adverse prognostic factor in colorectal cancer patients. Following in vitro studies revealed that HCT8 and HT29 cells transfected with p62-specific siRNA showed significantly decreased cell proliferation activity, whereas COLO320 and SW480 cells transfected with p62 expression plasmid showed significantly increased cell proliferation activity. The p62-mediated cell proliferation was not associated with the autophagy activity. These findings suggest that p62 promotes the cell proliferation mainly as a scaffold protein, and that the p62 status is a potent prognostic factor in colorectal carcinoma patients.

RITA plus 3-MA overcomes chemoresistance of head and neck cancer cells via dual inhibition of autophagy and antioxidant systems

Reactivation of p53 and induction of tumor cell apoptosis (RITA) is a small molecule that blocks p53–MDM2 interaction, thereby reactivating p53 in tumors. RITA can induce exclusive apoptosis in cancer cells independently of the p53 pathway; however, the resistance of cancer cells remains a major drawback. Here, we found a novel resistance mechanism of RITA treatment and an effective combined treatment to overcome RITA resistance in head and neck cancer (HNC) cells. The effects of RITA and 3-methyladenine (3-MA) were tested in different HNC cell lines, including cisplatin-resistant and acquired RITA-resistant HNC cells. The effects of each drug alone and in combination were assessed by measuring cell viability, apoptosis, cell cycle, glutathione, reactive oxygen species, protein expression, genetic inhibition of p62 and Nrf2, and a mouse xenograft model of cisplatin-resistant HNC. RITA induced apoptosis of HNC cells at different levels without significantly inhibiting normal cell viability. Following RITA treatment, RITA-resistant HNC cells exhibited a sustained expression of other autophagy-related proteins, overexpressed p62, and displayed activation of the Keap1-Nrf2 antioxidant pathway. The autophagy inhibitor 3-MA sensitized resistant HNC cells to RITA treatment via the dual inhibition of molecules related to the autophagy and antioxidant systems. Silencing of the p62 gene augmented the combined effects. The effective antitumor activity of RITA plus 3-MA was also confirmed in vivo in mouse xenograft models transplanted with resistant HNC cells, showing increased oxidative stress and DNA damage. The results indicate that RITA plus 3-MA can help overcome RITA resistance in HNC cells.

Condensed abstract

This study revealed a novel RITA resistant mechanism associated with the sustained induction of autophagy, p62 overexpression, and Keap1-Nrf2 antioxidant system activation. The combined treatment of RITA with the autophagy inhibitor 3-methyladenine overcomes RITA resistance via dual inhibition of autophagy and antioxidant systems in vitro and in vivo.

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RITA induces apoptosis of HNC cells at different levels.

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RITA resistance is related to the sustained expression of autophagy proteins and p62.

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Keap1-Nrf2 antioxidant system is also engaged in the RITA resistance mechanism.

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The autophagy inhibitor 3-MA sensitizes resistant HNC cells to RITA treatment.

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RITA plus 3-MA induces apoptosis of resistant HNC cells via dual inhibition of autophagy and Nrf2 system in vitro and in vivo.

Expression analysis of LC3B and p62 indicates intact activated autophagy is associated with an unfavorable prognosis in colon cancer

Autophagy is a lysosomal degradation and recycling process implicated in cancer progression and therapy resistance. We assessed the impact of basal autophagy in colon cancer (CC) in vitro and ex vivo. Functional autophagy was demonstrated in CC cell lines (LoVo; HT-29) showing a dose-dependent increase of the autophagy markers LC3B, p62 and autophagic vesciles upon increasing concentrations of the autophagy inhibitor chloroquine, which was demonstrated by immunoblotting, immunofluorescence and electron microscopy. Next, tissue microarrays with 292 primary resected CC, with cores from different tumor regions, and normal mucosa were analyzed by immunohistochemistry for LC3B and p62. CC tissue showed LC3B dot-like, p62 dot-like, cytoplasmic and nuclear staining in various levels without significant intratumoral heterogeneity. Tumoral LC3B and p62 expression was significantly higher than in normal tissue (p<0.001). No associations between staining patterns and pathological features (e.g. TNM categories; grading) were observed. Both low LC3B dot-like and low p62 dot-like-cytoplasmic staining were associated with worse overall survival (p=0.005 and p=0.002). The best prognostic discrimination, however, was seen for a combination of LC3B dot-like/p62 dot-like-cytoplasmic staining: high expression of both markers, indicative of impaired activated autophagy, was associated with the best overall survival. In contrast, high LC3B dot-like/low p62 dot-like-cytoplasmic expression, indicative of intact activated autophagy, was associated with the worst outcome (p<0.001 in univariate and HR=0.751; CI=0.607-0.928; p=0.008 in multivariate analysis). These specific expression patterns of LC3B and p62 pointing to different states of autophagy associated with diverging clinical outcomes highlighte the potential significance of basal autophagy in CC biology.

[Contribution of autophagy to intestinal homeostasis and pathology]

The intestinal epithelial cells are crucial mediators of intestinal homeostasis. The intestinal epithelium is the largest of the body's mucosal surfaces exposed to the environment. Intestinal homeostasis is essentially based on the maintenance of intestinal epithelial cell integrity, a complex process involving a balance between the intestinal flora, the immune system and the energy expenses linked to metabolism. Autophagy appears to be central to these functions and allows the epithelium to adapt to its environment and different stress situations by participating in antibacterial defense, by controlling the composition of the intestinal flora and the immune response, and by participating in energy homeostasis. Alterations of this protective mechanism are involved in inflammatory bowel diseases and colorectal cancer.

Hepatocellular carcinomas with intracellular hyaline bodies have a poor prognosis

BACKGROUND & AIMS

Mallory-Denk bodies (MDBs) and intracellular hyaline bodies (IHBs) are cytoplasmic inclusions found in a subset of hepatocellular carcinoma (HCC). MDBs are mainly composed of the intermediate filament proteins keratin (K) 8 and K18, the cellular stress- and adapter-protein sequestosome 1/p62 (p62) and ubiquitin, whereas IHBs consist of p62 and/or ubiquitin. Of note, cytoplasmic inclusions containing p62 can serve as markers of suppressed autophagy, which in turn has been associated with poor prognosis. The aim of this study was to evaluate the prognostic significance of p62-containing MDB and IHB in patients with HCC.

METHODS

Ninety resected HCCs were assessed by H&E histology for MDB or IHB, and their presence was confirmed by immunohistochemistry using K8/18, p62 and ubiquitin antibodies. The prognostic impact of inclusions was assessed using Kaplan-Meier and multivariate Cox proportional model.

RESULTS

Mallory-Denk bodies and/or IHB were found in about 50% of HCC. Both types of inclusions were seen in 21%, MDB only in 19% and IHB only in 10% of cases. The presence of MDB in tumours was associated with the steatohepatitic variant of HCC, which also showed fatty change, ballooning of tumour cells, MDBs, inflammation and pericellular fibrosis (P<.001). In contrast, IHBs were not associated with steatohepatitic morphology but were associated with significantly shorter overall survival (P=.006). Multivariate analysis revealed macroscopic vascular invasion (P=.045) and presence of IHB in HCC cells (P=.005) as independently associated with overall survival.

CONCLUSIONS

Intracellular hyaline bodies and macroscopic vascular invasion identify a subset of HCC patients with poor prognosis.

Tumor SQSTM1 (p62) expression and T cells in colorectal cancer

Evidence suggests that activation of autophagy in neoplastic cells potentiates antitumor immunity through cross-presentation of tumor-associated antigens to T cells and release of immune mediators. The SQSTM1 (sequestosome 1, p62) protein is degraded by activated autophagy, and might enhance immune response to tumor cells. We hypothesized that tumor SQSTM1 expression level might be inversely associated with T-cell densities in colorectal carcinoma tissue. We evaluated tumor SQSTM1 expression by immunohistochemistry in 601 rectal and colon cancer cases within the Nurses' Health Study and Health Professionals Follow-up Study. Ordinal logistic regression analyses were conducted to assess the association of tumor SQSTM1 expression with CD3⁺, CD8⁺, CD45RO (PTPRC)⁺, or FOXP3⁺ cell density in tumor tissue, controlling for potential confounders, including tumor status of microsatellite instability, CpG island methylator phenotype, long interspersed nucleotide element-1 methylation level, and KRAS, BRAF, and PIK3CA mutations. Tumor SQSTM1 expression level was inversely associated with FOXP3⁺ cell density (p_trend = 0.006), but not with CD3⁺, CD8⁺, or CD45RO⁺ cell density (with the adjusted α level of 0.01 for multiple hypothesis testing). For a unit increase in quartile categories of FOXP3⁺ cell density, multivariable odds ratios were 0.66 [95% confidence interval (CI), 0.45-0.98] for intermediate-level SQSTM1 expression, and 0.55 (95% CI, 0.36-0.83) for high-level SQSTM1 expression, compared with low-level SQSTM1 expression. Tumor SQSTM1 expression is inversely associated with FOXP3⁺ cell density in colorectal cancer tissue, suggesting a possible role of SQSTM1-expressing carcinoma cells on regulatory T cells in the tumor microenvironment.

Intestinal Autophagy and Its Pharmacological Control in Inflammatory Bowel Disease

Intestinal mucosal barrier, mainly composed of the intestinal mucus layer and the epithelium, plays a critical role in nutrient absorption as well as protection from pathogenic microorganisms. It is widely acknowledged that the damage of intestinal mucosal barrier or the disturbance of microorganism balance in the intestinal tract contributes greatly to the pathogenesis and progression of inflammatory bowel disease (IBD), which mainly includes Crohn’s disease and ulcerative colitis. Autophagy is an evolutionarily conserved catabolic process that involves degradation of protein aggregates and damaged organelles for recycling. The roles of autophagy in the pathogenesis and progression of IBD have been increasingly studied. This present review mainly describes the roles of autophagy of Paneth cells, macrophages, and goblet cells in IBD, and finally, several potential therapeutic strategies for IBD taking advantage of autophagy.

p62/SQSTM1-Dr. Jekyll and Mr. Hyde that prevents oxidative stress but promotes liver cancer

p62/SQSTM1 is a multifunctional signaling hub and autophagy adaptor with many binding partners, which allow it to activate mTORC1-dependent nutrient sensing, NF-κB-mediated inflammatory responses, and the NRF2-activated antioxidant defense. p62 recognizes polyubiquitin chains via its C-terminal domain and binds to LC3 via its LIR motif, thereby promoting the autophagic degradation of ubiquitinated cargos. p62 accumulates in many human liver diseases, including nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC), where it is a component of Mallory-Denk bodies and intracellular hyaline bodies. Chronic p62 elevation contributes to HCC development by preventing oncogene-induced senescence and death of cancer-initiating cells and enhancing their proliferation. In this review, we discuss p62-mediated signaling pathways and their roles in liver pathophysiology, especially NASH and HCC.

Lower Beclin 1 downregulates HER2 expression to enhance tamoxifen sensitivity and predicts a favorable outcome for ER positive breast cancer

Tamoxifen(TAM) is one of the most effective endocrine treatment for estrogen receptor(ER)-positive breast cancer, however drug resistance greatly limits benefit of it. Our purpose is to uncover the role of Beclin 1 in tamoxifen resistance and prognosis of ER positive breast cancer. We established a tamoxifen resistant ER-positive breast cancer cell subline MCF-7R presenting with higher Beclin 1 and human epidermal growth factor receptor 2(HER2) levels than MCF-7. Silencing Beclin 1 decreased levels of HER2 and significantly promoted TAM sensitivity of MCF-7 and MCF-7R in vitro. Overexpression of HER2 could reverse TAM sensitivity, which was formerly increased in Beclin 1 downregulated cell. Beclin 1 level was not only positively correlated with level of HER2 but also negatively correlated with overall survival of ER-positive breast cancer patients. Using bioinformatic methods, Beclin 1 mRNA was found to be negatively correlated with overall survival in breast cancer patients receiving TAM treatment. This study indicated for the first time that lower HER2 expression by Beclin 1 downregulation contributes to alteration of tamoxifen sensitivity and low Beclin 1 predicts favorable outcome in ER-positive breast cancer.

The Association of Palmitoylethanolamide with Luteolin Decreases Autophagy in Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition of the central nervous system (CNS) often resulting in severe functional impairment and for which there are not yet restorative therapies. In the present study, we performed a widely used model of SCI to determine the neuroprotective propriety of palmitoylethanolamide (PEA) and the antioxidant effect of a flavonoid luteolin (Lut), given as a co-ultramicronized compound co-ultraPEALut. In particular, by western blot analysis and immunofluorescence staining, we investigated whether this compound (at the dose of 1 mg/kg) was able to modulate autophagy. Our results showed that treatment with co-ultraPEALut after SCI reduced the expression of proteins promoter of autophagy such as Beclin-1 and microtubule-associated protein 1A/1B-light chain 3 (MAP-LC3). In contrast, this compound decreased the levels of mammalian target of rapamycin (mTOR), p-Akt, and p-70S6K which are proteins that inhibit autophagy. These data confirmed that the protective role of co-ultraPEALut is associated with inhibition of excessive autophagy and regulation of protein degradation. Therefore, treatment with co-ultraPEALut could be considered as a possible therapeutic approach in an acute traumatic lesion like SCI.

Prognostic relevance of autophagy-related markers LC3, p62/sequestosome 1, Beclin-1 and ULK1 in colorectal cancer patients with respect to KRAS mutational status

Background

Autophagy is a cellular pathway that regulates transportation of cytoplasmic macromolecules and organelles to lysosomes for degradation. Autophagy is involved in both tumorigenesis and tumour suppression. Here we investigated the potential prognostic value of the autophagy-related proteins Beclin-1, p62, LC3 and uncoordinated (UNC) 51-like kinase 1 (ULK1) in a cohort of colorectal cancer (CRC) specimens.

Methods

In this study, we analysed the immunoexpression of the autophagy-related proteins p62, LC3, Beclin-1 and ULK1 in 127 CRC patients with known KRAS mutational status and detailed clinical follow-up.

Results

Survival analysis of p62 staining showed a significant correlation of cytoplasmic (not nuclear) p62 expression with a favourable tumour-specific overall survival (OS). The prognostic power of cytoplasmic p62 was found in the KRAS-mutated subgroup but was lost in the KRAS wildtype subgroup. Survival analysis of Beclin-1 staining did not show an association with OS in the complete cohort. LC3 overexpression demonstrated a slight, though not significant, association with decreased OS. Upon stratifying cases by KRAS mutational status, nuclear (not cytoplasmic) Beclin-1 staining was associated with a significantly decreased OS in the KRAS-mutated subgroup but not in the KRAS wildtype CRCs. In addition, LC3 overexpression was significantly associated with decreased OS in the KRAS-mutated CRC subgroup. ULK1 expression was not correlated to survival.

Conclusions

Immunohistochemical analyses of LC3, p62 and Beclin-1 may constitute promising novel prognostic markers in CRC, especially in KRAS-mutated CRCs. This strategy might help in identifying high-risk patients who would benefit from autophagy-related anticancer drugs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12957-016-0946-x) contains supplementary material, which is available to authorized users.

Clinical relevance of autophagic therapy in cancer: Investigating the current trends, challenges, and future prospects

Oncophagy (cancer-related autophagy) has a complex dual character at different stages of tumor progression. It remains an important clinical problem to unravel the reasons that propel the shift in the role of oncophagy from tumor inhibition to a protective mechanism that shields full-blown malignancy. Most treatment strategies emphasize curbing protective oncophagy while triggering the oncophagy that is lethal to tumor cells. In this review, we focus on the trends in current therapeutics as well as various challenges in clinical trials to address the oncophagic dilemma and evaluate the potential of these developing therapies. A detailed analysis of the clinical and pre-clinical scenario of the anticancer medicines highlights the various inducers and inhibitors of autophagy. The ways in which tumor stage, the microenvironment and combination drug treatment continue to play an important tactical role are discussed. Moreover, autophagy targets also play a crucial role in developing the best possible solution to this oncophagy paradox. In this review, we provide a comprehensive update on the current clinical impact of autophagy-based cancer therapeutic drugs and try to lessen the gap between translational medicine and clinical science.