Astrocyte elevated gene-1 (AEG-1): A key driver of hepatocellular carcinoma (HCC)

An array of human cancers, including hepatocellular carcinoma (HCC), overexpress the oncogene Astrocyte elevated gene-1 (AEG-1). It is now firmly established that AEG-1 is a key driver of carcinogenesis, and enhanced expression of AEG-1 is a marker of poor prognosis in cancer patients. In-depth studies have revealed that AEG-1 positively regulates different hallmarks of HCC progression including growth and proliferation, angiogenesis, invasion, migration, metastasis and resistance to therapeutic intervention. By interacting with a plethora of proteins as well as mRNAs, AEG-1 regulates gene expression at transcriptional, post-transcriptional, and translational levels, and modulates numerous pro-tumorigenic and tumor-suppressive signal transduction pathways. Even though extensive research over the last two decades using various in vitro and in vivo models has established the pivotal role of AEG-1 in HCC, effective targeting of AEG-1 as a therapeutic intervention for HCC is yet to be achieved in the clinic. Targeted delivery of AEG-1 small interfering ribonucleic acid (siRNA) has demonstrated desired therapeutic effects in mouse models of HCC. Peptidomimetic inhibitors based on protein-protein interaction studies has also been developed recently. Continuous unraveling of novel mechanisms in the regulation of HCC by AEG-1 will generate valuable knowledge facilitating development of specific AEG-1 inhibitory strategies. The present review describes the current status of AEG-1 in HCC gleaned from patient-focused and bench-top studies as well as transgenic and knockout mouse models. We also address the challenges that need to be overcome and discuss future perspectives on this exciting molecule to transform it from bench to bedside.

In silico analysis and prediction of transcription factors of the proteins interacting with astrocyte elevated gene-1

Multifunctional in nature, the protein Astrocyte Elevated Gene-1 (AEG-1) controls several cancers through protein-protein interactions. Although, specific physiological processes and molecular functions linked with AEG-1 interactors remain unclear. In our present study, we procured the data of AEG-1 interacting proteins and evaluated their biological functions, associated pathways, and interaction networks using bioinformatic tools. A total of 112 proteins experimentally detected to interact with AEG-1 were collected from various public databases. DAVID 6.8 Online tool was utilized to identify the molecular functions, biological processes, cellular components that aid in understanding the physiological function of AEG-1 and its interactors in several cell types. With the help of integrated network analysis of AEG-1 interactors using Cytoscape 3.8.0 software, cross-talk between various proteins, and associated pathways were revealed. Additionally, the Enrichr online tool was used for performing enrichment of transcription factors of AEG-1 interactors' which further revealed a closely associated self-regulated interaction network of a variety of transcription factors that shape the expression of AEG-1 interacting proteins. As a whole, the study calls for better understanding and elucidation of the pathways and biological roles of both AEG-1 and its interactor proteins that might enable their application as biomarkers and therapeutic targets in various diseases in the very near future.

Silencing of Astrocyte elevated gene-1 (AEG-1) inhibits proliferation, migration, and invasiveness, and promotes apoptosis in pancreatic cancer cells

To investigate the role of Astrocyte elevated gene-1 (AEG-1) in the development and progress of pancreatic cancer, short hairpin RNA (shRNA) was inserted into the RNA interference vector to knock-down the endogenous AEG-1 in two pancreatic cancer cell lines: AsPC-1 and PANC-1. Our results showed that silencing of AEG-1 suppressed the proliferation, colony formation ability, and cell stemness of AsPC-1 and PANC-1 cells, and inhibited their G1-to-S phase transition. Results from apoptosis assay showed that knock-down of AEG-1 led to cell apoptosis. The expression of anti-apoptotic Bcl-2 was downregulated and that of the pro-apoptotic Bax and cleaved caspase-3 was upregulated in AEG-1-silenced pancreatic cancer cells. Further, the capability of AEG-1-silenced cells to migrate and to invade through the Matrigel-coated membrane was weaker, and the expression of matrix metallopeptidase 2 (MMP-2) and MMP-9 were decreased. Moreover, the AKT-β-catenin signaling pathway was inhibited in the cells with knock-down of AEG-1. In addition, the growth of xenograft tumors formed by AsPC-1 and PANC-1 cells was suppressed by AEG-1 shRNA. In conclusion, our study demonstrates that pancreatic cancer cells require AEG-1 to maintain their survival and metastasis, suggesting AEG-1 as a potential target for the treatment of pancreatic cancers.

Astrocyte elevated gene-1 promotes inflammation and invasion of fibroblast-like synoviocytes in rheumatoid arthritis

Astrocyte elevated gene-1 (AEG-1) was initially induced by HIV-1 infection and involved in tumor progression, migration and invasion as a nuclear factor-κB (NF-κB)-dependent gene. The present study we intended to investigate the protein expression of AEG-1 significantly associated with rheumatoid arthritis. Western blot analysis and immunohistochemistry demonstrated that AEG-1 was upregulated in synovial tissue of RA patients compared with the controls. Double immunofluorescent staining suggested that AEG-1 was expressed in fibroblast-like synoviocytes (FLS) of RA patients. Furthermore, the expression of AEG-1 in FLS was increased in time-dependent manner by TNF-α stimulation. Upon TNF-α-treated FLS, AEG-1 transferred from the cytoplasm to nucleus where it interacted with the p65 subunit of NF-κB, as examined by immunoprecipitation and immunofluorescent staining assay. Moreover, the inhibition of AEG-1 by RNA interference significantly suppressed TNF-α-induced IL-6 and MMP-3 expression, leading to attenuation of FLS migration and invasion and markedly decreased the phosphorylation of P65 and IκBα, as well as AKT in FLS. Collectively, Our findings provided evidence that AEG-1 contributed to the production of inflammatory cytokines, migration and invasion of RA FLS, and underscored the importance of AEG-1 in the inflammation process of RA.

Knockdown of Astrocyte Elevated Gene-1 Inhibits Activation of Hepatic Stellate Cells

BACKGROUND

Astrocyte elevated gene-1 (AEG-1) is a positive regulator of tumorigenesis and a valuable prognostic marker of a diverse array of cancers, including liver cancer; however, the relationship between AEG-1 and hepatic fibrogenesis is not known.

OBJECTIVE

The objective of this study was to explore the expression of AEG-1 during hepatic fibrogenesis and determine how AEG-1 regulates the profibrogenic phenotype of hepatic stellate cells (HSCs).

METHODS

The levels of AEG-1 were monitored in the fibrotic livers and transforming growth factor-β (TGF-β)- or lipopolysaccharide (LPS)-stimulated HSCs. The expression of AEG-1 was knocked down by lentivirus-mediated short hairpin RNA in HSCs, and collagen expression, proliferation assays, apoptosis induction studies, and migration assays were simultaneously conducted in vitro.

RESULTS

AEG-1 expression was increased in the fibrotic livers. At the cellular level, TGF-β or LPS stimulation, which caused HSC activation, induced AEG-1 expression in HSC-T6 and primary rat HSCs (P < 0.05). Knockdown of AEG-1 inhibited collagen I and α-smooth muscle actin expression (P < 0.05), reduced cell proliferation (P < 0.05) and motility (P < 0.05), and induced cell apoptosis (P < 0.05) in HSCs. This antifibrotic effect caused by lack of AEG-1 was associated with the inactivation of PI3K/Akt and the mitogen-activated protein kinase pathway.

CONCLUSIONS

Knockdown of AEG-1 suppressed the activation of HSCs by modulating the phenotype and inducing apoptosis. AEG-1 might be a potential target in treatment of hepatic fibrosis.

AEG-1 participates in high glucose-induced activation of Rho kinase and epithelial-mesenchymal transition in proximal tubular epithelial cells

OBJECTIVE

To prove whether astrocyte elevated gene-1 (AEG-1) plays a role in high glucose-stimulated Rho kinase activation and epithelial-mesenchymal transition (EMT) in human renal tubular epithelial (HK-2) cells.

METHODS

The protein levels of AEG-1, alpha-smooth muscle actin, E-cadherin and MYPT1 were determined by Western blot.

RESULTS

AEG-1 protein level was upregulated in HK-2 cells stimulated with high glucose. AEG-1 siRNA downregulated Rho kinase protein expression and blocked high glucose-induced EMT.

CONCLUSIONS

Our results show that AEG-1 acts a key role in high glucose-induced activation of Rho kinase and EMT in HK-2 cells.

Clinical significance of expression of AEG-1 and NF-κB p65 proteins in human primary hepatocellular carcinoma

AIM: To detect the expression of astrocyte elevated gene-1 (AEG-1) and nuclear factor-κB (NF-κB) p65 proteins in hepatocellular carcinoma (HCC) and to analyze their clinical significance.

METHODS: The expression of AEG-1 and NF-κB p65 proteins was detected by immunohistochemical analysis in 40 HCC samples, 40 tumor adjacent tissue samples, and 8 normal hepatic tissue samples. Western blot was also performed for detecting protein levels of AEG-1 and NF-κB p65 in part of the above tissue samples. The relationship between survival and expression of AEG-1 and NF-κB p65 was analyzed by Kaplan-Meier analysis.

RESULTS: The positive expression rates of AEG-1 in HCC, tumor adjacent tissue and normal tissue samples were 72.5% (29/40), 60% (24/40), and 12.5% (1/8), respectively; the differences among the three groups were statistically significant (χ² = 9.74, P < 0.05). The expression of AEG-1 protein was significantly higher in HCC and tumor adjacent tissue than in normal tissue (P < 0.05). The expression rates of NF-κB p65 protein in HCC, tumor adjacent tissue and normal tissue samples were 75% (30/40), 62.5% (25/40), and 12.5% (1/8), respectively; the differences among the three groups were statistically significant (χ² = 11.29, P < 0.05). The expression of NF-κB p65 protein was significantly higher in HCC and tumor adjacent tissue than in normal tissue (P < 0.05). The expression of AEG-1 and NF-κB p65 protein determined by Western blot was similar to that by immunohistochemical analysis. The survival rates in patients with positive expression of AEG-1 and NF-κB p65 were significantly lower than those in patients with negative expression (P < 0.05)．

CONCLUSION: AEG-1 may promote invasion and metastasis of HCC through up-regulation of NF-κB p65 expression and activity. The combined detection of expression of AEG-1 and NF-κB p65 has significance in gene therapy and in predicting the prognosis of patients with HCC.

Expression and clinicopathological significance of miR-193a-3p and its potential target astrocyte elevated gene-1 in non-small lung cancer tissues

Background

Aberrant expression of miR-193a-3p and astrocyte elevated gene-1 (AEG-1) have been revealed to be related to the tumorigenesis of various cancers, including non-small cell lung cancer (NSCLC). However, the significance of miR-193a-3p and its correlation with AEG-1 in NSCLC has not been explored. The purpose of this study was to evaluate the association between miR-193a-3p and AEG-1 and their relationship with the clinicopathological features in NSCLC patients.

Methods

Via online in silico prediction, complementary sequences were found between miR-193a-3p and the 3′-untranslated region of AEG-1. Three independent cohorts were applied in the current study. Firstly, miR-193a-3p level was detected in 125 cases of NSCLC with quantitative real-time PCR (qRT-PCR). Secondly, AEG-1 protein level was evaluated in 339 cases of lung cancers with immunohistochemistry. Finally, the relationship between miR-193a-3p and AEG-1 protein expression was verified in another group with 65 cases of NSCLC.

Results

The results showed that miR-193a-3p level was decreased in NSCLC tissues and significantly negatively related to tumor size (r = −0.277, P = 0.002), clinical TNM stage (r = −0.226, P = 0.011), lymph node metastasis (r = −0.186, P = 0.038), epidermal growth factor receptor (EGFR) protein level (r = −0.272, P = 0.041). On the contrary, AEG-1 protein expression was up-regulated in NSCLC and positively relative to tumor size (r = 0.240, P < 0.001), TNM stages (r = 0.164, P = 0.002) and lymph node metastasis (r = 0.232, P < 0.001) in NSCLC patients. In addition, miR-193a-3p was found to be inversely associated with AEG-1 protein expression in the third cohort (r = −0.564, P < 0.001).

Conclusion

In conclusion, miR-193a-3p and AEG-1 might be responsible for the carcinogenesis and aggressiveness of NSCLC. AEG-1 has the potential to be one of the targeted genes of miR-193a-3p. However, future in vitro and in vivo experiments are needed to verify this hypothesis.

AEG-1 affects expression of HIF-1α and miR-34a in colorectal cancer cells

AIM: To construct a stable expression system for astrocyte elevated gene-1 (AEG-1) using lentiviral vector in colorectal cancer (CRC) cells and assess its relationship with miR-34a and hypoxia-inducible factor-1α (HIF-1α).

METHODS: AEG-1 expression in CRC cells was examined by Western blot analysis. A lentiviral vector carrying AEG-1 was constructed, identified by PCR and DNA sequencing, and then transfected into 293FT cells using lentiviral packaging systems. SW1116 cells were infected with the virus and analyzed by qRT-PCR and Western blot. Expression of miR-34a and HIF-1α was detected using qRT-PCR and Western blot.

RESULTS: Western blot analysis showed that AEG-1 expression was the lowest in SW1116 among 7 CRC cell lines (P < 0.05). AEG-1 lentiviral vector was constructed successfully as revealed by DNA sequencing. The stable expression of AEG-1 was validated by qRT-PCR and Western blot (0.53 ± 0.44 vs 2.02 ± 0.22, P < 0.05; 0.71 ± 0.14 vs 2.02 ± 0.22, P < 0.05). Up-regulation of AEG-1 inhibited miR-34a expression (P < 0.01) but increased HIF-1α expression (P < 0.01).

CONCLUSION: An AEG-1 lentiviral vector has been successfully constructed. AEG-1 can down-regulate the expression of miR-34a and up-regulate the expression of HIF-1α.