ATG7 promotes the tumorigenesis of lung cancer but might be dispensable for prognosis predication: a clinicopathologic study

ATG7 upregulation contributes to malignant transformation of human bronchial epithelial cells by B[a]PDE via DNMT3B protein degradation and miR-494 promoter methylation

Lung cancer primarily arises from exposure to various environmental factors, particularly airborne pollutants. Among the various lung carcinogens, benzo(a)pyrene and its metabolite B[a]PDE are the strongest ones that actively contribute to lung cancer development. ATG7 is an E1-like activating enzyme and contributes to activating autophagic responses in mammal cells. However, the potential alterations of ATG7 and its role in B[a]PDE-caused lung carcinogenesis remain unknown. Here, we found that B[a]PDE exposure promoted ATG7 expression in mouse lung tissues, while B[a]PDE exposure resulted in ATG7 induction in human normal bronchial epithelial cells. Our studies also demonstrated a significant correlation between high ATG7 expression levels and poor overall survival in lung cancer patients. ATG7 knockdown significantly repressed Beas-2B cell transformation upon B[a]PDE exposure, and such promotive effect of ATG7 on cell transformation mediated the p27 translation inhibition. Further studies revealed that miR-373 inhibition was required to stabilize ATG7 mRNA, therefore increasing ATG7 expression following B[a]PDE exposure, while ATG7 induction led to the autophagic degradation of the DNA methyltransferase 3 Beta (DNMT3B) protein, in turn promoted miR-494 transcription via its promoter region methylation status suppression. We also found that the miR-494 upregulation inhibited p27 protein translation and promoted bronchial epithelial cell transformation via its directly targeting p27 mRNA 3'-UTR region. Current studies, to the best of our knowledge, are for the first time to identify that ATG7 induction and its mediated autophagy is critical for B[a]PDE-induced transformation of human normal epithelial cells.

Regulation of autophagy gene expression and its implications in cancer

Autophagy is a catabolic cellular process that targets and eliminates superfluous cytoplasmic components via lysosomal degradation. This evolutionarily conserved process is tightly regulated at multiple levels as it is critical for the maintenance of homeostasis. Research in the past decade has established that dysregulation of autophagy plays a major role in various diseases, such as cancer and neurodegeneration. However, modulation of autophagy as a therapeutic strategy requires identification of key players that can fine tune the induction of autophagy without complete abrogation. In this Review, we summarize the recent discoveries on the mechanism of regulation of ATG (autophagy related) gene expression at the level of transcription, post transcription and translation. Furthermore, we briefly discuss the role of aberrant expression of ATG genes in the context of cancer.

Mechanism of LncHOTAIR Regulating Proliferation, Apoptosis, and Autophagy of Lymphoma Cells through hsa-miR-6511b-5p/ATG7 Axis

Objective

To explore the role of LncHOTAIR in apoptosis and autophagy in lymphoma.

Methods

The interaction between LncHOTAIR and miR-6511b-5p, as well as between miR-6511b-5p and ATG7, was verified by a dual luciferase assay. LncHOTAIR overexpression lentivirus was transducted and siATG7s were transfected into Raji and BJAB lymphoma cells, and the efficiency was verified by qPCR. Lymphocyte proliferation was detected by the cell counting kit-8 (CCK8) test, and autophagy was detected by transmission electron microscopy. The protein expressions of ULK1, Beclin1, ATG7, LC3, Bax, cleaved-caspase 3, and Bcl-2 were detected using Western blots.

Results

There was a targeting relationship between LncHOTAIR and miR-6511b-5p and between miR-6511b-5p and ATG7. LncHOTAIR overexpression promoted the proliferation and autophagy of Raji and BJAB cells, significantly upregulated ATG7, Beclin1, ULK1, Bcl-2, and LC3-II/LC3-I levels, and downregulated Bax and cleaved-caspase3 levels. siATG7 significantly inhibited the proliferation and autophagy of Raji and BJAB cells and promoted their apoptosis.

Conclusion

LncHOTAIR/hsa-miR-6511b-5p/ATG7 could regulate the proliferation, apoptosis, and autophagy of Raji and BJAB lymphoma cells.

Calorie restriction and breast cancer treatment: a mini-review

Calorie restriction (CR), referred to as a reduction in dietary calorie intake without malnutrition, has been demonstrated to be a safe way to extend longevity of yeast, worms, and laboratory animals, and to decrease the risk factors in age-related diseases including cancer in humans. Pre-clinical studies in animal models demonstrated that CR may enhance the efficacy of chemotherapy, radiation therapy, and immunotherapy during breast cancer treatment. Reduced calorie intake ameliorates risk factors and delays the onset of cancer by altering metabolism and fostering health-enhancing characteristics including increased autophagy and insulin sensitivity, and decreased blood glucose levels, inflammation, angiogenesis, and growth factor signaling. CR is not a common protocol implemented by medical practitioners to the general public due to the lack of substantial clinical studies. Future research and clinical trials are urgently needed to understand fully the biochemical basis of CR or CR mimetics to support its benefits. Here, we present a mini-review of research studies integrating CR as an adjuvant to chemotherapy, radiation therapy, or immunotherapy during breast cancer treatment.

Emerging roles of ATG7 in human health and disease

The cardinal stages of macroautophagy are driven by core autophagy-related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood-onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.

Nuclear Receptor 4A2 (NR4A2/NURR1) Regulates Autophagy and Chemoresistance in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer with poor prognosis and chemotherapy with gemcitabine has limited effects and is associated with development of drug resistance. Treatment of Panc1 and MiaPaca2 pancreatic cancer cells with gemcitabine induced expression of the orphan nuclear receptor 4A2 (NURR1) and analysis of the cancer genome atlas indicated the NURR1 is overexpressed in pancreatic tumors and is a negative prognostic factor for patient survival. Results of NURR1 knockdown or treatment with the NURR1 antagonist 1,1-bis(3΄-indolyl)-1-(p-chlorophenyl)methane (C-DIM 12) demonstrated that NURR1 was pro-oncogenic in pancreatic cancer cells and regulated cancer cell and tumor growth and survival. NURR1 is induced by gemcitabine and serves as a key drug-resistance factor and is also required for gemcitabine-induced cytoprotective autophagy. NURR1 regulated genes were determined by RNA sequencing of mRNAs expressed in MiaPaCa2 cells expressing NURR1 and in CRISPR/Cas9 gene edited cells for NURR1 knockdown and KEGG enrichment analysis of the differentially expressed genes showed that autophagy was the major pathway regulated by NURR1. Moreover, NURR1 regulated expression of two major autophagic genes ATG7 and ATG12 which are also overexpressed in pancreatic tumors and like NURR1 are negative prognostic factors for patient survival. Thus, gemcitabine-induced cytoprotective autophagy is due to the NURR1 - ATG7/ATG12 axis and this can be targeted and disrupted by NURR1 antagonist C-DIM12 demonstrating the potential clinical applications for combination therapies with gemcitabine and NURR1 antagonists.

Prognostic autophagy model based on CASP4 and BIRC5 expression in patients with renal cancer: independent datasets-based study

The purpose of this study was to identify key autophagy-related genes (ARGs) in patients with renal cancer (RC) by bioinformatics analysis, and to clarify their potential prognostic value. Thirty-eight differentially expressed ARGs were identified between RC and normal tissues based on The Cancer Genome Atlas database. Functional enrichment analysis suggested that autophagy may play a tumor-promoting role in the initiation of RC. We established a prognostic model with two ARGs (CASP4 and BIRC5) demonstrating significant correlations in expression levels with patient overall survival (OS). Multivariate Cox regression analysis showed that age and the autophagy genes prognostic model were independent prognostic factors for patients with RC. Considering the known prognostic significance of clinical stage in RC, we constructed a nomogram based on age, clinical stage, and the prognostic model. The prognostic model was verified in a separate validation set and external cohort of patients from Beijing Hospital. Patients of low and high risk were defined based on the median risk value calculated by the model and the high risk appeared associated with a significant shorter OS (P < 0.01). Overall, our findings reveal that ARGs have potential prognostic value in patients with RC, providing new directions for targeted therapy.

Exosomal Transfer of lncRNA H19 Promotes Erlotinib Resistance in Non-Small Cell Lung Cancer via miR-615-3p/ATG7 Axis

Background

Drug resistance restrains the effect of drug therapy in non-small cell lung cancer (NSCLC). However, the mechanism of the acquisition of drug resistance remains largely unknown. This study aims to investigate the effect of exosomal lncRNA H19 on erlotinib resistance in NSCLC and the underlying mechanism.

Methods

HCC827 and A549 cells were continuously grafted into erlotinib-containing culture medium to establish erlotinib-resistant cell lines. The expression of H19 and miR-615-3p was detected by qRT-PCR. The protein levels of MMP2, MMP9, CD9, CD63 and ATG7 were measured by Western blot. Cell viability and proliferation were determined by Cell Counting Kit-8 (CCK-8) and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, respectively. Migration and invasion were assessed by transwell assay. Xenograft tumor models were used to investigate the effect of H19 on erlotinib resistance in vivo. Online software and dual-luciferase reporter assay were used to predicate the downstream targets and confirm the targeted relationships.

Results

H19 was upregulated in erlotinib-resistant cells, and knockdown of H19 inhibited cell proliferation, migration and invasion in erlotinib-resistant cells. Extracellular H19 can be packaged into exosomes. Exosomes containing H19 induced erlotinib resistance of sensitive cells, while knockdown of H19 abolished this effect. miR-615-3p was a target of H19 and can bind to ATG7. Exosomal H19 affected erlotinib resistance of erlotinib-resistant NSCLC cells via targeting miR-615-3p to regulate ATG7 expression. In addition, the serum exosomal H19 was upregulated in patients with erlotinib resistance. Furthermore, downregulated H19 decreased the resistance of tumor cells to erlotinib in vivo.

Conclusion

Our study demonstrated that exosomal H19 facilitated erlotinib resistance in NSCLC via miR-615-3p/ATG7 axis, which might provide a potential target for the diagnosis and treatment of NSCLC.

Identification of an Autophagy-Related Prognostic Signature for Clear Cell Renal Cell Carcinoma

Abnormal autophagy is closely related to the development of cancer. Many studies have demonstrated that autophagy plays an important role in biological function in clear cell renal cell carcinoma (ccRCC). This study aimed to construct a prognostic signature for ccRCC based on autophagy-related genes (ARGs) to predict the prognosis of ccRCC. Differentially expressed ARGs were obtained from ccRCC RNA-seq data in The Cancer Genome Atlas (TCGA) database. ARGs were enriched by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The prognostic ARGs used to construct the risk score models for overall survival (OS) and disease-free survival (DFS) were identified by Cox regression analyses. According to the median value of the risk score, patients were divided into a high-risk group and a low-risk group. The OS and DFS were analyzed by the Kaplan-Meier method. The predictive accuracy was determined by a receiver operating characteristic (ROC) curve analysis. Additionally, we performed stratification analyses based on different clinical variables and evaluated the correlation between the risk score and the clinical variables. The differentially expressed ARGs were mainly enriched in the platinum drug resistance pathway. The prognostic signatures based on 11 ARGs for OS and 5 ARGs for DFS were constructed and showed that the survive time was significantly shorter in the high-risk group than in the low-risk group (P < 0.001). The ROC curve for OS exhibited good predictive accuracy, with an area under the curve value of 0.738. In the stratification analyses, the OS time of the high-risk group was shorter than that of the low-risk group stratified by different clinical variables. In conclusion, an autophagy-related signature for OS we constructed can independently predict the prognosis of ccRCC patient, and provide a deep understanding of the potential biological mechanisms of autophagy in ccRCC.

Targeting cellular microtubule by phytochemical apocynin exhibits autophagy-mediated apoptosis to inhibit lung carcinoma progression and tumorigenesis

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide. Several targets have been identified for lung cancer therapy, amongst which 'Microtubule' and its dynamics are the most widely studied and used in therapy. Tubulin-microtubule polymer dynamics are highly sought after targets in the field of anti-cancer drug designing. Natural compounds are important sources for developing anticancer therapeutics owing to their efficacy and lower cytotoxicity. Evidence suggested that therapeutic targeting of microtubule by natural compounds is amongst the most widely used interventions in numerous cancer therapies including lung cancer.

PURPOSE

To determine the efficacy of apocynin (a natural compound) in suppressing the progression of lung carcinoma both in vitro and in vivo, along with the identification of targets and the underlying mechanism for developing a novel therapeutic approach.

METHODS

We have demonstrated themicrotubule depolymerizing role of apocynin by established protocols in cellular and cell-free system. The efficacy of apocynin to inhibit lung carcinoma progression was studied on A549 cells.The tumoricidal ability of apocynin was studied in BALB/c mice model as well.Mice were classified into 4 groups namely-group II mice as tumor control; group III-IV mice asalso tumor-induced but treated with differential apocynin doses whereas group I mice were kept as normal.

RESULTS

Apocynin, showed selective cytotoxicity towards lung cancer cells rather than normal lung fibroblast cells. Apocynin inhibited oncogenic properties including growth, proliferation (p < 0.05), colony formation (p < 0.05), invasion (p < 0.05) and spheroid formation (p < 0.05) in lung cancer cells. Apart from other established properties, apocynin was found to be a novel and potent component to bind with tubulin and depolymerize cellular microtubule network. Apocynin mediated cellular microtubule depolymerization was the driving mechanism to trigger autophagy-mediated apoptotic cell death (p < 0.05) which in turn retarded lung cancer progression. Furthermore, apocynin showed tumoricidal characteristics to inhibit lung tumorigenesis in mice as well.

CONCLUSION

Targeting tubulin-microtubule equilibrium with apocynin could be the key regulator to catastrophe cellular catabolic processes to mitigate lung carcinoma. Thus, apocynin could be a potential therapeutic agent for lung cancer treatment.

MicroRNA‑154 functions as a tumor suppressor in bladder cancer by directly targeting ATG7

Aberrant expression of miR‑154 is usually found in cancer studies; however, the role of miR‑154 has seldom been reported in bladder cancer (BCa). In this study, we observed that miR‑154 expression was significantly downregulated in BCa tissues and cell lines, and was associated with several clinicopathological characteristics, including advanced T stage, lymphatic invasion, and distant metastasis. Low expression level of miR‑154 was associated with poor survival outcomes in BCa patients. Overexpression of miR‑154 led to significant decrease in the proliferation, migration, and invasion of BCa cells, while knockdown of miR‑154 yielded the opposite effect. ATG7 was identified as a direct target of miR‑154. ATG7 expression was negatively correlated with miR‑154 expression in BCa tissues. Silencing of ATG7 achieved a similar effect to miR‑154 overexpression; overexpression of ATG7 reversed the inhibitory effect of miR‑154 on BCa cell proliferation, migration and invasion. A xenograft study revealed that miR‑154 inhibited BCa cell growth in vivo, and suppressed ATG7 expression. Altogether, this study demonstrated that miR‑154 may function as a tumor suppressor in BCa and indicated that miR‑154 may be a potential therapeutic target for BCa patients.

Long noncoding RNA UCA1 targets miR-582-5p and contributes to the progression and drug resistance of bladder cancer cells through ATG7-mediated autophagy inhibition

BACKGROUND

Rently, the incidence of bladder cancer has been on the rise. Accumulating researches have been conducted to clarify the molecular mechanisms and potential therapeutic targets of bladder cancer. The present study aims to explore the regulatory mechanism of the urothelial carcinoma-associated 1 (UCA1)-miR-582-5p-ATG7 axis in bladder cancer.

METHODS

Quantitative real-time polymerase chain reaction was used to detect mRNA level. Relative protein expression was detected by western blot. wound healing assay and transwell were used to determine migration and invasion of cells. in addtion, luciferase reporter assay and immunohistochemistry were performed.

RESULTS

UCA1 expression was upregulated in bladder cancer tissues and cells, while the depletion of UCA1 by shRNA resulted in the suppression of cell proliferation, invasion, migration, and drug resistance. Further studies demonstrated that UCA1 could directly interact with miR-582-5p, and that there was an inverse correlation between miR-582-5p and UCA1. In addition, we found that ATG7 is a target of miR-582-5p and can be downregulated by either miR-582-5p overexpression or UCA1 knockdown. In particular, the autophagy is reduced when UCA1 shRNA is introduced. Moreover, the in vivo experiment further demonstrated the contribution of UCA1 in bladder cancer including tumor growth, invasion, and migration, and UCA1 knockdown can inhibit the aforementioned activities.

CONCLUSION

These results provided evidence for a novel UCA1 interaction regulatory network in bladder cancer, that is, UCA1-miR-582-5p-ATG7-autophagy axis. Our study provides a new insight into the treatment of bladder cancer.

Association of ATG7 Polymorphisms and Clear Cell Renal Cell Carcinoma Risk

BACKGROUND

Kidney cancer is one of the most common cancers worldwide. Recent studies have suggested that single nucleotide polymorphisms (SNPs) in autophagy-related gene are associated with the risk of kidney cancer.

OBJECTIVE

This study was undertaken to investigate the association of autophagyrelated gene 7 (ATG7) polymorphisms with the risk of clear cell renal cell carcinoma (ccRCC) in the Chinese Han population.

METHODS

Blood samples were collected from 293 ccRCC patients and 297 healthy controls. Three ATG7 polymorphisms (rs1375206, rs2606736 and rs6442260) were genotyped by Agena MassARRAY. The association was estimated by genetic models and stratification analyses.

RESULTS

A significant association was observed between allele A of rs6442260 and ccRCC risk (OR = 0.76, 95% CI: 0.58-0.99, p = 0.039). Genetic model analysis revealed that rs2606736 (OR = 0.57, 95% CI: 0.34-0.95, p = 0.031) and rs6442260 (OR = 0.44, 95% CI: 0.22-0.90, p = 0.021) were associated with decreased risk of ccRCC under recessive model. Age stratification analysis showed that rs2606736 (OR = 0.67, 95% CI: 0.46-0.98, p = 0.036) and rs6442260 (OR = 0.26, 95% CI: 0.07-0.89, p = 0.014) were significantly decreased risk of ccRCC under the log-additive model in age > 55 years old and ≤ 55 years old, respectively.

CONCLUSIONS

This study indicated that ATG7 polymorphisms (rs2606736 and rs6442260) have a protective role for ccRCC risk. Further large sample size and functional assays are needed to confirm our findings and reveal the role of ATG7 polymorphisms in ccRCC carcinogenesis.

MiR-490-3p inhibits autophagy via targeting ATG7 in hepatocellular carcinoma

The miR-490-3p was transfected into HepG2 cells to explore the correlation between miR-490-3p and hepatocellular carcinoma cell proliferation, apoptosis, and autophagy and its downstream target gene ATG7. Then we could possibly provide a mechanism for the treatment of hepatocellular carcinoma. MiR-490-3p was screened out by fold change > 4 and P < 0.01 using gene microarray data. The expression level of miR-490-3p was tested by qRT-PCR and the prognosis analysis was achieved by using TCGA data. The cell proliferation was tested via colony formation assay and CCK-8 after the miR-490-3p mimics were transfected into HepG2 cells; the variations of cell cycle and apoptosis was examined by flow cytometry assay; the number of autophagosome was observed by electron microscopy and the changes of autophagy-relative protein LC-II and LC-I as well as their ratio was tested by western blot. MiR-490-3p is low expressed in hepatocellular carcinoma cell lines and tissues. The results of TCGA showed that miR-490-3p high expression indicated better prognosis. After HepG2 cells were transfected with miR-490-3p mimics, cell viability was increased, cell proliferation was enhanced, cell cycle was blocked in G0/G1 phase, cell apoptosis rate was increased, the number of autophagosomes was reduced, autophagy-associated protein LC-II was decreased, and LC-I was increased and their ratio was decreased. After 3-MA was added, cell proliferation was declined, cell apoptosis rate was increased. Besides, the autophagy was inhibited by knocking down the ATG7, which promoted the cell apoptosis. MiR-490-3p could suppress cell proliferation, retard cell cycle and upgrade cell apoptosis by inhibiting autophagy in HCC cells via targeting ATG7. © 2018 IUBMB Life, 70(6):468-478, 2018.

Clinical Applications of Autophagy Proteins in Cancer: From Potential Targets to Biomarkers

Autophagy, a lysosome-mediated intracellular degradation and recycling pathway, plays multiple context-dependent roles in tumorigenesis and treatment resistance. Encouraging results from various preclinical studies have led to the initiation of numerous clinical trials with the intention of targeting autophagy in various cancers. Accumulating knowledge of the particular mechanisms and players involved in different steps of autophagy regulation led to the ongoing discovery of small molecule inhibitors designed to disrupt this highly orchestrated process. However, the development of validated autophagy-related biomarkers, essential for rational selection of patients entering clinical trials involving autophagy inhibitors, is lagging behind. One possible source of biomarkers for this purpose is the autophagy machinery itself. In this review, we address the recent trends, challenges and advances in the assessment of the biomarker potential of clinically relevant autophagy proteins in human cancers.