Induction of autophagy by Beclin-1 in granulosa cells contributes to follicular progesterone elevation in ovarian endometriosis.

Endometriosis is a common gynecological disease in which ovarian dysfunction can be an important cause of infertility. Elevated progesterone (P4) levels during the follicular phase is possibly associated with impaired oocyte quality and pregnancy outcome in endometriosis. Beclin-1 (BECN1), an essential mediator of autophagy, has been shown to be related to the development and progression of endometriosis. This study aimed to investigate the autophagic activity in ovarian granulosa cells (GCs) of patients with endometriosis and to clarify the role of BECN1 in preovulatory P4 elevation. Our results demonstrated that serum P4/estradiol (E2) ratio and P4-to-follicle index (the average P4 secretion per follicle) on the day of human chorionic gonadotropin administration were elevated in women with ovarian endometriosis. Increased expression of BECN1 and enhanced autophagy were observed in GCs of patients with ovarian endometriomas. In cultured GCs, BECN1 knockdown reduced P4 secretion and the expression of key steroidogenic enzymes; whereas overexpression of BECN1 resulted in induced P4 production with activated biosynthesis pathway. Moreover, inhibition of autophagy by BECN1 knockdown significantly attenuated low-density lipoprotein (LDL)-induced P4 synthesis. These findings provide new insights into the role of BECN1 in late follicular P4 elevation in patients with endometriosis by promoting the degradation pathway of LDL for P4 biosynthesis via lysosome activation in GCs, and have potential therapeutic implications for the improvement of oocyte quality in women affected by endometriosis.

Loss of Concurrent Regulation of the Expression of BIF-1, BAX, and Beclin-1 in Primary and Metastatic Melanoma.

Melanoma is one of the most aggressive and drug-resistant cancers. Despite novel promising therapeutic strategies, the prognosis of metastatic melanoma patients remains poor and it is often associated with high relapse rates. Endophilin B1, also known as BIF-1, is a multifunctional protein involved in several biological processes such as autophagy and apoptosis. BIF-1 promotes apoptosis through binding to BAX and its translocation to the mitochondrial outer membrane. On the other hand, BIF-1 can interact with Beclin-1 through UVRAG to promote autophagy. Several reports suggest an ambiguous role of BIF-1 in cancer development and progression. For example, it has been demonstrated that the expression of BIF-1 is reduced in both primary and metastatic melanoma and that the reduction of BIF-1 expression is associated with reduced overall survival of melanoma patients. Here we show that the expression of Beclin-1 and active form of BAX are also reduced in the melanoma patients. However, while we observed strong positive correlations between the expression of BIF-1 and Beclin-1 as well as between BIF-1 and BAX in benign nevi, these correlations were lost in the primary and metastatic melanoma cells. These data indicate disruption in the proximal molecular mechanisms which regulate expression of BIF-1, Beclin-1, and BAX in the primary and metastatic melanoma.

Autophagy in spinal ligament fibroblasts: evidence and possible implications for ossification of the posterior longitudinal ligament.

BACKGROUND: The molecular mechanisms of ossification of the posterior longitudinal ligament (OPLL) remain to be elucidated. The aim of the present study was to investigate the autophagy of spinal ligament fibroblasts derived from patients with OPLL and to examine whether autophagy-associated gene expression was correlated with the expression of osteogenic differentiation genes. METHODS: Expression of autophagy-associated genes was detected in 37 samples from 21 OPLL patients and 16 non-OPLL patients. The correlation of autophagy-associated gene expression and the expression of osteogenic differentiation genes was analyzed by Pearson's correlation. The expression of autophagy-associated genes of ligament fibroblasts was assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blotting, and immunofluorescence. The incidence of autophagy was assessed by flow cytometry. After knockdown using small interfering RNA targeting Beclin1, the expression of osteogenic differentiation genes were compared in spinal ligament fibroblasts. RESULTS: In clinical specimens, mRNA expression levels of microtubule-associated protein 1 light chain 3 and Beclin1 were higher in the OPLL group compared with the non-OPLL group. Pearson correlation analysis demonstrated that Beclin1 expression was positively correlated with expression of osteocalcin (OCN) (r = 0.8233, P < 0.001), alkaline phosphatase, biomineralization associated (ALP) (r = 0.7821, P < 0.001), and collagen type 1 (COL 1) (r = 0.6078, P = 0.001). Consistently, the upregulation of autophagy-associated genes in ligament fibroblasts from patients with OPLL were further confirmed by western blotting and immunofluorescence. The incidence of autophagy was also increased in ligament fibroblasts from patients with OPLL. Furthermore, knockdown of Beclin1 led to a decrease in the expression of OCN, ALP, and COL 1 by 63.2% (P < 0.01), 52% (P < 0.01), and 53.2% (P < 0.01) in ligament fibroblasts from patients with OPLL, respectively. CONCLUSIONS: Beclin1-mediated autophagy was involved in the osteogenic differentiation of ligament fibroblasts and promoted the development of OPLL.

Beclin1 Binds to Enterovirus 71 3D Protein to Promote the Virus Replication.

Enterovirus 71 (EV71) is the main pathogen causing hand-foot-mouth disease (HFMD) in infants and children, which can also lead to severe neurological diseases and even death. Therefore, understanding the replication mechanism of EV71 is of great significance for the prevention and control of EV71-induced diseases. Beclin1 (BECN1, a mammalian homologue of ATG6 in yeast) is an important core protein for the initiation and the normal process of autophagy in cells. In addition to its involvement in autophagy, Beclin1 has also been reported to play an important role in cancer and innate immune signaling pathways. However, the role of Beclin1 in EV71 replication remains elusive. Here, we primarily found that Beclin1 facilitates EV71 replication in human rhabdomyosarcoma (RD) cells and the autophagy was actually induced, but Beclin1 was not significantly affected at either mRNA level or protein level during early EV71 infection. Further studies discovered that Beclin1 could interacts with EV71 non-structural protein 3D mainly through its evolutionary conserved domain (ECD) and coiled-coiled domain (CCD), thus promoting the replication of EV71 in human rhabdomyosarcoma (RD) cells and human astroglioma (U251) cells. Collectively, we reveal a novel regulatory mechanism associated with Beclin1 to promote EV71 replication, thus providing a potential therapeutic target for the prevention and control of EV71-associated diseases.

The role of radiation induced oxidative stress as a regulator of radio-adaptive responses.

Purpose: Various sources of radiation including radiofrequency, electromagnetic radiation (EMR), low- dose X-radiation, low-level microwave radiation and ionizing radiation (IR) are indispensable parts of modern life. In the current review, we discussed the adaptive responses of biological systems to radiation with a focus on the impacts of radiation-induced oxidative stress (RIOS) and its molecular downstream signaling pathways.Materials and methods: A comprehensive search was conducted in Web of Sciences, PubMed, Scopus, Google Scholar, Embase, and Cochrane Library. Keywords included Mesh terms of "radiation," "electromagnetic radiation," "adaptive immunity," "oxidative stress," and "immune checkpoints." Manuscripts published up until December 2019 were included.Results: RIOS induces various molecular adaptors connected with adaptive responses in radiation exposed cells. One of these adaptors includes p53 which promotes various cellular signaling pathways. RIOS also activates the intrinsic apoptotic pathway by depolarization of the mitochondrial membrane potential and activating the caspase apoptotic cascade. RIOS is also involved in radiation-induced proliferative responses through interaction with mitogen-activated protein kinases (MAPks) including p38 MAPK, ERK, and c-Jun N-terminal kinase (JNK). Protein kinase B (Akt)/phosphoinositide 3-kinase (PI3K) signaling pathway has also been reported to be involved in RIOS-induced proliferative responses. Furthermore, RIOS promotes genetic instability by introducing DNA structural and epigenetic alterations, as well as attenuating DNA repair mechanisms. Inflammatory transcription factors including macrophage migration inhibitory factor (MIF), nuclear factor κB (NF-κB), and signal transducer and activator of transcription-3 (STAT-3) paly major role in RIOS-induced inflammation.Conclusion: In conclusion, RIOS considerably contributes to radiation induced adaptive responses. Other possible molecular adaptors modulating RIOS-induced responses are yet to be divulged in future studies.

Lentiviral-Mediated Beclin-1 Overexpression Inhibits Cell Proliferation and Induces Autophagy of Human Esophageal Carcinoma Eca109 Cell Xenograft in Nude Mice.

BACKGROUND: Esophageal carcinoma is one of the common malignant tumors in digestive tract. BECLIN-1 is a key gene that regulates autophagy, and its abnormal expression may be related with many human tumors. However, the mechanism of BECLIN-1 in esophageal carcinoma remains unknown. OBJECTIVE: In this study, we explored the effect of BECLIN-1 overexpression on tumor growth in mice with esophageal carcinoma and its mechanism. METHODS: Recombined lentiviral vector containing BECLIN-1 was used to transfect human esophageal carcinoma Eca109 cells and establish stable cell line. qRT-PCR was used to detect BECLIN-1 mRNA level in the transfected Eca109 cells, CCK-8 assay was used to detect cell proliferation. Beclin-1, P62 and LC3-II protein expression levels in Eca109 cells were detected using Western blot analysis. Subcutaneous xenograft nude mice model of human esophageal carcinoma was established, and the tumor growths in Beclin-1 group, control group and empty vector group were monitored. Beclin-1 protein expression in vivo was detected by immunohistochemistry. RESULTS: Beclin-1 mRNA and protein were overexpressed in Eca109 cells. Compared with empty vector group, the growth rate of cells transfected with BECLIN-1 decreased significantly. Compared with the control group and empty vector group, the expression level of P62 protein in beclin-1 group was significantly decreased, while the expression level of LC3-II protein was significantly increased. The tumor growth rate in nude mice of Beclin-1 group was significantly lower than that of the control group and empty vector group, and Beclin-1 protein was mainly expressed in Beclin-1 group in vivo. CONCLUSION: BECLIN-1 can induce autophagy in esophageal carcinoma Eca109 cells, and it can significantly inhibit the growth of esophageal carcinoma.

Beclin1-mediated ferroptosis activation is associated with isoflurane-induced toxicity in SH-SY5Y neuroblastoma cells.

The widely used inhalation anesthetic, isoflurane, potentially induces neuronal injury in clinical practice. Previous studies showed multiple forms of cell death that resulted from isoflurane-induced cytotoxicity, but the precise underlying mechanism remains poorly understood. Ferroptosis has recently been identified as a non-apoptotic form of regulated cell death. Here, we found that ferroptosis inhibitors, ferrostatin-1 and deferoxamine mesylate (DFOM), showed great efficiency in maintaining cell viability in SH-SY5Y neuroblastoma cells exposed to a high concentration of isoflurane for 24 h. We also observed that cellular chelatable iron and lipid peroxidation were increased in a concentration-dependent manner in response to isoflurane. In addition, isoflurane upregulated Beclin1 phosphorylation, followed by the formation of a Beclin1-solute carrier family 7 member 11 (SLC7A11) complex, which affected the activity of cystine/glutamate antipoter and further regulated ferroptotic cell death. Accordingly, Beclin1 overexpression aggravated isoflurane-induced cell damage by upregulating ferroptosis. This phenomenon was significantly attenuated by silencing of Beclin1 in SH-SY5Y cells. These findings indicate that Beclin1 may regulate ferroptosis in a manner involving inhibition of glutamate exchange activity of system xc(-), which is implicated in isoflurane-induced toxicity. In particular, when isoflurane is administrated at high concentrations and for an extended duration, ferroptosis is more likely to play a crucial role in isoflurane-induced toxicity.

Single-Cell RNA Transcriptome Helps Define the Limbal/Corneal Epithelial Stem/Early Transit Amplifying Cells and How Autophagy Affects This Population.

Purpose: Single-cell RNA-sequencing (scRNA-seq) was used to interrogate the relatively rare stem (SC) and early transit amplifying (TA) cell populations in limbal/corneal epithelia from wild-type and autophagy-compromised mice. Methods: We conducted scRNA-seq on ocular anterior segmental tissue from wild-type and beclin 1-deficient (beclin1+/-) mice, using a 10X Gemomics pipeline. Cell populations were distinguished by t-distributed stochastic neighbor embedding. Seurat analysis was conducted to compare gene expression profiles between these two groups of mice. Differential protein expression patterns were validated by immunofluorescence staining and immunoblotting. Results: Unbiased clustering detected 10 distinct populations: three clusters of mesenchymal and seven clusters of epithelial cells, based on their unique molecular signatures. A discrete group of mesenchymal cells expressed genes associated with corneal stromal SCs. We identified three limbal/corneal epithelial cell subpopulations designated as stem/early TA, mature TA, and differentiated corneal epithelial cells. Thioredoxin-interacting protein and PDZ-binding kinase (PBK) were identified as novel regulators of stem/early TA cell quiescence. PBK arrested corneal epithelial cells in G2/M phase of the cell cycle. Beclin1+/- mice displayed a decrease in proliferation-associated (Ki67, Lrig1) and stress-response (H2ax) genes. The most increased gene in beclin1+/- mice was transcription factor ATF3, which negatively regulates limbal epithelial cell proliferation. Conclusions: Establishment of a comprehensive atlas of genes expressed by stromal and epithelial cells from limbus and cornea forms the foundation for unraveling regulatory networks among these distinct tissues. Similarly, scRNA-seq profiling of the anterior segmental epithelia from wild-type and autophagy-deficient mice provides new insights into how autophagy influences proliferation in these tissues.

VEGF-A promotes angiogenesis after acute myocardial infarction through increasing ROS production and enhancing ER stress-mediated autophagy.

Proangiogenesis is generally regarded as an effective approach for treating ischemic heart disease. Vascular endothelial growth factor (VEGF)-A is a strong and essential proangiogenic factor. Reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and autophagy are implicated in the process of angiogenesis. This study is designed to clarify the regulatory mechanisms underlying VEGF-A, ROS, ER stress, autophagy, and angiogenesis in acute myocardial infarction (AMI). A mouse model of AMI was successfully established by occluding the left anterior descending coronary artery. Compared with the sham-operated mice, the microvessel density, VEGF-A content, ROS production, expression of vascular endothelial cadherin, positive expression of 78 kDa glucose-regulated protein/binding immunoglobulin protein (GRP78/Bip), and LC3 puncta in CD31-positive endothelial cells of the ischemic myocardium were overtly elevated. Moreover, VEGF-A exposure predominantly increased the expression of beclin-1, autophagy-related gene (ATG) 4, ATG5, inositol-requiring enzyme-1 (IRE-1), GRP78/Bip, and LC3-II/LC3-I as well as ROS production in the human umbilical vein endothelial cells (HUVECs) in a dose and time-dependent manner. Both beclin-1 small interfering RNA and 3-methyladenine treatment predominantly mitigated VEGF-A-induced tube formation and migration of HUVECs, but they failed to elicit any notable effect on VEGF-A-increased expression of GRP78/Bip. Tauroursodeoxycholic acid not only obviously abolished VEGF-A-induced increase of IRE-1, GRP78/Bip, beclin-1 expression, and LC3-II/LC3-I, but also negated VEGF-A-induced tube formation and migration of HUVECs. Furthermore, N-acetyl- l-cysteine markedly abrogated VEGF-A-increased ROS production, IRE-1, GRP78/Bip, beclin-1 expression, and LC3-II/LC3-I in the HUVECs. Taken together, our data demonstrated that increased spontaneous production of VEGF-A may induce angiogenesis after AMI through initiating ROS-ER stress-autophagy axis in the vascular endothelial cells.

Profilin 1 induces drug resistance through Beclin1 complex-mediated autophagy in multiple myeloma.

Autophagy plays an important role in multiple myeloma (MM) for homeostasis, survival and drug resistance, but which genes participate in this process is unclear. We identified several cytoskeleton genes upregulated in MM patients by gene expression profiling (GEP) datasets; in particular, patients with high profilin 1 (PFN1) expression had poor prognosis in MM. In vitro, overexpressed PFN1 promotes proliferation and bortezomib (BTZ) resistance in MM cells. Further study indicated overexpression of PFN1 significantly promoted the process of autophagy and induced BTZ resistance in MM. Otherwise, knockdown of PFN1 blocked autophagy and sensitized MM to BTZ. Co-immunoprecipitation in MM cells indicated that PFN1 could bind Beclin1 complex and promote the initiation of autophagy. Inhibition of autophagy by blocking the formation of Beclin1 complex could reverse the phenotype of BTZ resistance in MM. Our findings suggested that PFN1 could promote autophagy through taking part in Beclin1 complex and contribute to BTZ resistance, which may become a novel molecular target in the therapy of MM.

Increased autophagy blocks HER2-mediated breast tumorigenesis.

Allelic loss of the autophagy gene, beclin 1/BECN1, increases the risk of patients developing aggressive, including human epidermal growth factor receptor 2 (HER2)-positive, breast cancers; however, it is not known whether autophagy induction may be beneficial in preventing HER2-positive breast tumor growth. We explored the regulation of autophagy in breast cancer cells by HER2 in vitro and the effects of genetic and pharmacological strategies to increase autophagy on HER2-driven breast cancer growth in vivo. Our findings demonstrate that HER2 interacts with Beclin 1 in breast cancer cells and inhibits autophagy. Mice with increased basal autophagy due to a genetically engineered mutation in Becn1 are protected from HER2-driven mammary tumorigenesis, and HER2 fails to inhibit autophagy in primary cells derived from these mice. Moreover, treatment of mice with HER2-positive human breast cancer xenografts with the Tat-Beclin 1 autophagy-inducing peptide inhibits tumor growth as effectively as a clinically used HER2 tyrosine kinase inhibitor (TKI). This inhibition of tumor growth is associated with a robust induction of autophagy, a disruption of HER2/Beclin 1 binding, and a transcriptional signature in the tumors distinct from that observed with HER2 TKI treatment. Taken together, these findings indicate that the HER2-mediated inhibition of Beclin 1 and autophagy likely contributes to HER2-mediated tumorigenesis and that strategies to block HER2/Beclin 1 binding and/or increase autophagy may represent a new therapeutic approach for HER2-positive breast cancers.

Adiponectin inhibits inflammatory cytokines production by Beclin-1 phosphorylation and B-cell lymphoma 2 mRNA destabilization: role for autophagy induction.

BACKGROUND AND PURPOSE: Adiponectin potently suppresses inflammatory mediator production. Autophagy is known to play a critical role in the modulation of inflammatory responses by adiponectin. However, the underlying mechanisms are not clearly understood. Interaction between Beclin-1 and B-cell lymphoma 2 (Bcl-2) is a critical event in autophagy induction. We examined the effects of globular adiponectin (gAcrp) on the Beclin-1/Bcl-2 association and its underlying mechanisms. EXPERIMENTAL APPROACH: The effect of gAcrp on the interaction between Beclin-1 and Bcl-2 was examined by immunoprecipitation followed by Western blotting. To elucidate the underlying mechanisms, we determined the effects of gAcrp on Beclin-1 phosphorylation and Bcl-2 mRNA stability, and investigated their role in the suppression of inflammatory mediators using pharmacological inhibitors and transient target gene knockdown. KEY RESULTS: Globular adiponectin disrupted the association between Beclin-1 and Bcl-2 and increased Beclin-1 phosphorylation at Thr119 , critical residue for binding with Bcl-2, via a death-associated protein kinase-1 (DAPK1)-dependent mechanism. Moreover, gAcrp reduced Bcl-2 expression via Bcl-2 mRNA destabilization, without significantly affecting Bcl-2 promoter activity and protein degradation, which was mediated by tristetraprolin (TTP) induction. Finally, DAPK1 and TTP were shown to play key roles in gAcrp-induced autophagosome formation and suppression of LPS-stimulated TNF-α and IL-1ß expression. CONCLUSION AND IMPLICATIONS: Beclin-1 phosphorylation and Bcl-2 mRNA destabilization mediated by DAPK1 and TTP are crucial events leading to autophagy and the suppression of inflammatory cytokine production by gAcrp. These results provide novel mechanisms underlying adiponectin's modulation of inflammatory responses. DAPK and TTP are potential therapeutic targets for the management of inflammation.

Expression levels and roles of EMC-6, Beclin1, and Rab5a in the cervical cancer.

OBJECTIVE: This study is to investigate the role of EMC-6 in the pathogenesis of cervical cancer, especially concerning its relationship with autophagy. PATIENTS AND METHODS: Totally 100 invasive cervical cancer, 80 cervical intraepithelial neoplasia (CIN), and 80 normal cervical tissue samples were obtained. Expression levels of EMC-6, Beclin1, and Rab5a in the tissues were detected by immunohistochemistry. RESULTS: Our results showed that positive staining of EMC-6 was mainly located in the nucleus. Compared with the normal cervical tissue, the positive rates of EMC-6 were significantly increased in the CIN and cervical cancer tissues. Moreover, the EMC-6 positive rate in the CIN tissue was higher than the cervical cancer tissue. No significant association was observed between the expression levels of EMC-6 and the clinicopathological features of cervical cancer, including age, FIGO staging, tumor size, tumor type, histological type, cell differentiation, and lymph node metastasis. Compared with the normal cervical tissue, the positive rate of Beclin1 in the CIN tissue was significantly declined, which was further significantly down-regulated in the cervical cancer tissue. However, the positive rate of Rab5a in the CIN tissue was significantly higher than the normal cervical tissue. Moreover, compared with the normal cervical and CIN tissues, the positive rate of Rab5a in the cervical cancer tissue was further significantly increased. EMC-6 was not associated with Beclin1 and Rab5a. CONCLUSIONS: The expression level of EMC-6 is significantly elevated in cervical cancer, without significant correlation with Beclin1 and Rab5a. These findings might contribute to the understanding of the pathogenesis of cervical cancer and the involved role of EMC-6.

[Research progress on mechanism of Nix-mediated mitophagy].

Autophagy is fundamental to maintain cellular homeostasis. As one kind of the most well-studied selective autophagy, autophagy of mitochondria (mitophagy)is crucial for the clearance of damaged mitochondria. Mitophagy dysfunction has been proved to be closely associated with many human diseases. Nix is a key protein for mitophagy during the maturation of reticulocytes. However, the detailed molecular mechanisms underlying Nix-mediated mitophagy are not fully understood. This article summarizes three possible working models of Nix in mitophagy induction. Firstly, Nix can interplay with Parkin, another important protein for mitophagy, to initiate mitophagy. Secondly, Nix can serve as a receptor for autophagy machinery by interacting with Atg8 family through its LIR motif. Finally, as a BH3-only protein, Nix can compete with Beclin-1 to bind other members of Bcl-2 family resulting in increased free Beclin-1 in cytosol, which further promotes autophagy flux.

Advances in Hypoxia-Mediated Mechanisms in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common and the third most deadly malignant tumor worldwide. Hypoxia and related oxidative stress are heavily involved in the process of HCC development and its therapies. However, direct and accurate measurement of oxygen concentration and evaluation of hypoxic effects in HCC prove difficult. Moreover, the hypoxia-mediated mechanisms in HCC remain elusive. Here, we summarize recent major evidence of hypoxia in HCC lesions shown by measuring partial pressure of oxygen (pO2), the clinical importance of hypoxic markers in HCC, and recent advances in hypoxia-related mechanisms and therapies in HCC. For the mechanisms, we focus mainly on the roles of oxygen-sensing proteins (i.e., hypoxia-inducible factor and neuroglobin) and hypoxia-induced signaling proteins (e.g., matrix metalloproteinases, high mobility group box 1, Beclin 1, glucose metabolism enzymes, and vascular endothelial growth factor). With respect to therapies, we discuss mainly YQ23, sorafenib, 2-methoxyestradiol, and celastrol. This review focuses primarily on the results of clinical and animal studies.

Bcl-xL Affects Group A Streptococcus-Induced Autophagy Directly, by Inhibiting Fusion between Autophagosomes and Lysosomes, and Indirectly, by Inhibiting Bacterial Internalization via Interaction with Beclin 1-UVRAG.

Anti-apoptotic Bcl-2 and Bcl-xL are proposed to regulate starvation-induced autophagy by directly interacting with Beclin 1. Beclin 1 is also thought to be involved in multiple vesicle trafficking pathways such as endocytosis by binding to Atg14L and UVRAG. However, how the interaction of Bcl-2 family proteins and Beclin 1 regulates anti-bacterial autophagy (xenophagy) is still unclear. In this study, we analyzed these interactions using Group A Streptococcus (GAS; Streptococcus pyogenes) infection as a model. GAS is internalized into epithelial cells through endocytosis, while the intracellular fate of GAS is degradation by autophagy. Here, we found that Bcl-xL but not Bcl-2 regulates GAS-induced autophagy. Autophagosome-lysosome fusion and the internalization process during GAS infection were promoted in Bcl-xL knockout cells. In addition, knockout of Beclin 1 phenocopied the internalization defect of GAS. Furthermore, UVRAG interacts not only with Beclin 1 but also with Bcl-xL, and overexpression of UVRAG partially rescued the internalization defect of Beclin 1 knockout cells during GAS infection. Thus, our results indicate that Bcl-xL inhibits GAS-induced autophagy directly by suppressing autophagosome-lysosome fusion and indirectly by suppressing GAS internalization via interaction with Beclin 1-UVRAG.

Prognostic role of autophagy-related proteins in epithelial ovarian cancer: a meta-analysis of observational studies.

INTRODUCTION: Autophagy has been reported to play important roles in tumorigenesis. This meta-analysis was conducted in order to investigate the association between autophagy-related proteins, beclin 1 and LC3, with prognostic value and clinical characteristics of ovarian cancer. EVIDENCE ACQUISITION: PubMed, EMBASE and CNKI databases (up to August 2016) were searched for eligible studies using the following key words: "beclin 1", "beclin-1", "Becn 1", "Becn-1", "Atg6", "LC3", "ovarian cancer", "ovarian carcinoma", "ovarian neoplasm", "ovarian tumor", "ovary cancer", "ovary carcinoma", "ovary neoplasm", "ovary tumor". The random effects model was used to combine effect sizes. Higgins I2 value was used to examine heterogeneity between studies. Sensitivity analysis was used to investigate the heterogeneity and the stability of the results. Egger's test and Harbord's test were used to examine publication bias. EVIDENCE SYNTHESIS: Eight studies including a total of 872 patients were eligible for this meta-analysis. The results showed expressions of both beclin 1 (OR=0.498, 95% CI: 0.298-0.832) and LC3 (OR=0.308, 95% CI: 0.142-0.668) were associated with FIGO stage (FIGO I/II versus FIGO III/IV). However, no association was found between the expression of beclin 1 and overall survival (HR=0.678, 95% CI: 0.434-1.058), age (OR=0.965, 95% CI: 0.473-1.967), lymph node metastasis (OR=0.517, 95% CI: 0.218-1.227), pathological classification (OR=0.895, 95% CI: 0.649-1.233) and differentiation (OR=0.571, 95% CI: 0.261-1.247). Similarly, no relationship was found between LC3 with age (OR=0.947, 95% CI: 0.399-2.248), pathological classification (OR=0.821, 95% CI: 0.410-1.644), and differentiation (OR=0.432, 95% CI: 0.118-1.580). CONCLUSIONS: Autophagy-related proteins might be important markers of ovarian cancer progression. However, due to the limited number of original studies, more well-designed, large-scale, high-quality studies are needed, which provide new, valuable information for further investigation.

mda-7/IL-24 Mediates Cancer Cell-Specific Death via Regulation of miR-221 and the Beclin-1 Axis.

Melanoma differentiation-associated gene-7/IL-24 (mda-7/IL-24) displays broad-spectrum anticancer activity in vitro, in vivo in preclinical animal models, and in a phase I/II clinical trial in patients with advanced cancers without harming normal cells or tissues. Here we demonstrate that mda-7/IL-24 regulates a specific subset of miRNAs, including cancer-associated miR-221. Either ectopic expression of mda-7/IL-24 or treatment with recombinant His-MDA-7 protein resulted in downregulation of miR-221 and upregulation of p27 and PUMA in a panel of cancer cells, culminating in cell death. Mda-7/IL-24-induced cancer cell death was dependent on reactive oxygen species induction and was rescued by overexpression of miR-221. Beclin-1 was identified as a new transcriptional target of miR-221, and mda-7/IL-24 regulated autophagy through a miR-221/beclin-1 feedback loop. In a human breast cancer xenograft model, miR-221-overexpressing MDA-MB-231 clones were more aggressive and resistant to mda-7/IL-24-mediated cell death than parental clones. This is the first demonstration that mda-7/IL-24 directly regulates miRNA expression in cancer cells and highlights the novelty of the mda-7/IL-24-miR-221-beclin-1 loop in mediating cancer cell-specific death. Cancer Res; 77(4); 949-59. ©2016 AACR.

Induction of epithelial-mesenchymal transition (EMT) by Beclin 1 knockdown via posttranscriptional upregulation of ZEB1 in thyroid cancer cells.

Beclin 1 has emerged as a haploinsufficient tumor suppression gene in a variety of human carcinomas. In order to clarify the role of Beclin 1 in thyroid cancer, Beclin 1 was knockdown in thyroid cancer cell lines. The current study demonstrated that knockdown of Beclin 1 resulted in morphological and molecular changes of thyroid cancer cells consistent with epithelial-mesenchymal transition (EMT), a morphogenetic procedure during which cells lose their epithelial characteristics and acquire mesenchymal properties concomitantly with gene expression reprogramming. In addition, the current study presented evidence demonstrating that Beclin 1 knockdown triggered this prometastatic process via stabilization of the EMT inducer ZEB1 mRNA through upregulation of AU-binding factor 1 (AUF1), which is recruited to the 3'-untranslated region (UTR) of the ZEB1 mRNA and decreases its degradation. We also found a negative correlation of Beclin 1 with AUF1 or ZEB1 in thyroid cancer tissues. These results indicated that at least some tumor suppressor functions of Beclin 1 were mediated through posttranscriptional regulation of ZEB1 via AUF1 in thyroid cancers.

RNF216 contributes to proliferation and migration of colorectal cancer via suppressing BECN1-dependent autophagy.

Originally identified as an E3 ligase regulating toll-like receptor (TLR) signaling, ring finger protein 216 (RNF216) also plays an essential role in autophagy, which is fundamental to cellular homeostasis. Autophagy dysfunction leads to an array of pathological events, including tumor formation. In this study, we found that RNF216 was upregulated in human colorectal cancer (CRC) tissues and cell lines, and was associated with progression of CRC. RNF216 promoted CRC cell proliferation and migration in vitro and in vivo, largely by enhancing proteasomal degradation of BECN1, a key autophagy regulator and tumor suppressor. RNF216 restricted CRC cell autophagy through BECN1 inhibition under nutritional starvation conditions. RNF216 knockdown increased the autophagy, limiting CRC cell proliferation and migration. Moreover, BECN1 knockdown or autophagy inhibition restored proliferation and migration of RNF216-knockdown CRC cells. Collectively, our results suggested that RNF216 promoted CRC cell proliferation and migration by negatively regulating BECN1-dependent autophagy. This makes RNF216 as a potential biomarker and novel therapeutic target for inhibiting CRC development and progression.